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About Google Book Search Google's mission is to organize the world's information and to make it universally accessible and useful. Google Book Search helps readers discover the world's books while helping authors and publishers reach new audiences. You can search through the full text of this book on the web at http : //books . google . com/| Digitized by Google Digitized by Google Digitized by VjOOQ IC Digitized by Google Digitized by Google K.F. WENDT LIBRARY UW COLLEGE OF ENGR. 21 sjaBgggwENUE rc5 Digitized by Google Digitized by Google Digitized by Google Digitized by Google Digitized by Google Digitized by Google Digitized by Google INTERNATIONAL LIBRARY OF TECHNOLOGY A SERIES OF TEXTBCX)KS FOR PERSONS ENGAGED IN THE ENGINEERING PROFESSIONS AND TRADES OR FOR THOSE WHO DESIRE INFORMATION CONCERNING THEM. ' FULLY ILLUSTRATED AND CONTAINING NUMEROUS PRACTICAL EXAMPLES AND THEIR SOLUTIONS GASOLINE AUTOMOBILES GASOLINE AUTOMOBILE ENGINES AUTOMOBILE ENGINE AUXILIARIES ELECTRIC IGNITION TRANSMISSION AND CONTROL MECHANISM BEARINGS AND LUBRICATION AUTOMOBILE TIRES (VOU 0 SCRANTON INTERNATIONAL TEXTBOOK COMPANY HOB Digitized by Google Gasoline Automobiles: Cop3rright, 1913, by International Textbook Company. Copy- right in Great Britain. Gasoline Automobile Engines: Copyright, 1913, by International Textbook Com- pany. Copyright in Great Britain. Automobile Engine Auxiliaries: Copyright. 1913. by International Textbook Com- pany. Copyright in Great Britain. Electric Ignition, Parts 1 and 3: Copyrifi^t, 1907. 1910, by International Textbook Company. Entered at Stationers' Hall, London. Electric Ignition, Part 2: Copyright, 1910, by International Textbook Company. Entered at Stationers' Hall, London. Electric Ignition. Part 4: Copyright. 1913. by International Textbook Company. Copyright in Great Britain. Transmission and Control Mechanism: Copyright, 1914. by International Textbook Company. Copyright in Great Britain. Bearings and Lubrication. Part 1: Copyright. 1913. by International Textbook Com- pany. Copyright in Great Britain. Bearings and Lubrication, Part 2: Copyright. 1914, by International Textbook Com- pany. Copyright in Great Britain. Automobile Tires: Copyright. 1914. by International Textbook Company. Copy- right in Great Britain. All rights reserved. Press OF International Textbook Company . SCRANTON, Pa. 29581 HOB Digitized by Google ^02330 APR -6 I9!B SB HOB PREFACE The volumes of the International Library of Technology are made up of Instruction Papers, or Sections, comprising the various courses of instruction for students of the Interna- tional Correspondence Schools. The original manuscript for each Instruction Paper is prepared by a person thoroughly qualified, both technically and by experience, to write with authority on his subject. In many cases the writer is regularly employed elsewhere in practical work and writes for us during spare time. The manuscripts are then carefully edited to make them suitable for correspondence work. The only qualification for enrolment as a student in these Schools is the ability to read English and to write intelligibly the answers to the Examination Questions. Hence^ our stu- dents are of all grades of education, and our Instruction Papers are, therefore, written in the simplest possible lan- guage so as to make them readily understood by all students. If technical expressions are essential to a thorough under- standing of the subject, they are clearly explained when first introduced. The great majority of our students wish to prepare them- selves for advancement in their vocations or to qualify for other and more congenial occupations. Their time for study is usually after the day's work is done and is limited to a few hours each day. Therefore, every effort is made to give them practical and accurate information in clear, concise form, and to make this information include all of the essentials but none of the non-essentials. To effect this result derivations of rules and formulas are usually omitted, but thorough and complete instructions are given regarding how, when, and under what m Digitized by Google iv PREFACE conditions any particular rule, formula, or process should be applied. Whenever possible one or more examples, such as would be likely to arise in actual practice, together with their solutions, are given for illustration. As the best way to make a statement, explanation, or descrip- tion clear is to give a picture or a diagram in connection with it, illustrations are very freely used. These illustrations are especially made by our own Illustrating Department in order to adapt them fully to the requirements of the text. Projec- tion drawings, sectional drawings, outline drawings, perspec- tive drawings, partly shaded or full shaded, are employed, according to which will best produce the desired result. Half- tone engravings are used only in those cases where the general effect is desired rather than the actual details. In the table of contents that immediately follows are given the titles of the Sections included in this volume, and under each title is listed the main topics discussed. At the end of the volume will be found a complete index, «o that quick reference can be made to any subject treated. International Textbook Company iicm Digitized by Google CONTENTS Gasoline Automobiles General Characteristics General Assembly of the Automobile . Methods of Propelling the Automobile Bodies and Accessories Types of Bodies Accessory Fittings Automobile Tops Wind Shields Speedometers Automobile Rimning Gear Wheels Front Axles Rear Axles and Housings Springs and Frames Shock Absorbers Section Gasoline Automobile Engines Principles of Operation 2 Four-Cycle Principle 2 Two-Cycle Principle 2 Typical Automobile Engines 2 Four-Cycle Engines 2 Unit Power Plant ! 2 Two-Cycle Engines 2 Details of Construction 3 Automobile-Engine Cylinders 3 Crank-Cases 3 Manifolds 3 Reciprocating and Rotating Parts 3 Page 1 2 9 30 30 37 37 38 40 49 49 56 71 98 102 1 1 13 18 18 42 46 1 1 15 24 27 Digitized by Google vi CONTENTS Gasoline Automobile Engines — (Continued) Section Page Valves and Valve Mechanism 3 37 Engine Fittings and Engine Rating .... 3 48 Automobile-Engine Auxiliaries Cooling, Muffling, and Governing ..... 4 1 Water Cooling 4 2 Air Cooling 4 27 Exhaust Mufflers 4 30 Governing Devices 4 34 Electric Ignition Theory and Application 6 1 Electrodynamics 6 4 Magnets and Magnetism . . 6 12 Electromagnetic Induction 6 18 Ignition Apparatus 6 20 Primary Batteries 6 22 Secondary, or Storage, Batteries 6 30 Spark Coils 6 41 Induction Coils 6 43 Current-distributing Devices 7 1 Ignitess 7 1 Spark Plugs 7 5 Timers 7 10 Distributors 7 12 Switches 7 21 Current-Measuring Instruments 7 28 Ignition Systems 7 34 Low-Tension Ignition 7 34 High-Tension Ignition 7 36 Dual Ignition 7 45 Direct-Current Generators 8 -1 Principles of Operation 8 1 Details of Construction 8 7 Magneto-Electric Generators 8 19 Details of Construction 8 24 Low-Tension Magnetos 8 29 Low-Tension Magneto-Ignition Systems . . 8 36 Digitized by Google CONTENTS vii Electric Ignition — (Continued) Section Page Dual Ignition Systems 8 42 High-Tension Magnetos 8 45 Spark Control 8 63 Spark Intensity 8 79 Starting on the Spark 8 89 Modem Ignition Systems 8 91 Single Magneto-Ignition Systems 8 91 Dual Ignition Systems 8 104 Double Ignition Systems 8 117 Miscellaneous Ignition Systems 8 124 Transmission and Control Mechanism Friction Clutches 9 1 Cone Clutches 9 3 Disk Clutches 9 14 Contracting and Expanding Clutches ... 9 25 Clutch-Operating Devices 9 30 Clutch Brakes 9 34 Friction Material for Clutches 9 35 Transmission Mechanism 9 37 Speed-Changing Mechanism 9 37 Sliding Change-Speed Gears 9 38 Planetary Change-Speed Gears 9 58 Friction-Gear Transmission 9 62 Electric Gear-Shifting Mechanism 9 64 Pnetmiatic Gear-Shifting Mechanism ... 9 70 Two-Speed Bevel-Gear Rear Axle 9 72 Power Transmission Details 9 76 Control Mechanisms 9 86 Steering Mechanisms 9 86 Brake Mechanism 9 97 Bearings and Lubrication Bearings 10 1 Plain Bearings 10 1 Antifriction Bearings 10 14 Straight Roller Bearings 10 15 Tapered Roller Bearings 10 20 Digitized by Google vin CONTENTS Bearing and Lubrication — {Continued) Section Page Radial Ball Bearings 10 23 Radial-and-Thrust Ball Bearings 10 35 Ball Thrust Bearings 10 39 Lubrication 10 43 Lubricants 10 43 Engine Lubrication Systems 10 60 Splash Lubrication Systems 10 53 Pressure-Feed Lubrication Systems .... 10 65 Combined Splash and Pressure-Feed Lubri- cation System 10 73 Lubricating Devices 10 75 Automobile Tires Tire Construction and Application .... 11 1 Pneumatic Tires 11 1 Demountable and Quick-Detachable Rims .11 9 AirValves, Lugs, and Inner Tubes 11 16 Tire Maintenance 11 24 Inflation of Tires 11 24 Pump Connections and Pressure Gauges . . 11 36 ■ Tire Protectors and Antiskid Devices ... 11 40 Tire Deterioration and Repairs 11 45 Causes of Tire Failure 11 45 Roadside Tire Repairs 11 53 Tire Tools 11 53 Handling of Clincher Tires 11 56 Handling of Quick-Detachable Tires . ... 11 63 Roadside Inner-Tube Repairs 11 65 Roadside Repairs to Casings 11 69 Vulcanized Tire Repairs 11 73 Digitized by Google GASOLINE AUTOMOBILES (PART 1) GENERAL CHARACTERISTICS INTRODUCTION CLASSIFICATION OF MOTpB VEHICLES 1. In its broadest sense, the term automobile applies to any self-propelled vehicle, including even steam road rollers, the traction engines used in agricultural work, and locomotives. Custom, however, has narrowed the application of this term until it is now chiefly applied to the self-propelled vehicles used for the transportation, without pa)rment therefor, of passengers for pleasure or for business pxuposes. When the same auto- mobile is diverted from its original purpose to the canying of passengers for a money consideration, it is then spoken of as a livery automobile or a livery car, implying that it is for hire. The terms motor car, or car for short, and motor vehicle are used S3monymously.with the term automobile. Motor vehicles devoted entirely to the carrying of freight are called motor trucks, auto trucks, delivery cars, delivery wagons, or commercial vehicles, the latter term being sufficiently broad to embrace them all as a class distinct from pleasure vehicles. Although automobiles are sometimes hired for touring pur- poses, motor vehicles for the transportation of passengers for hire in cities are of two general classes, namely, motor busses and taxicabs. The latter are usually designed to carry four COrrniCHTBO by INTKIINATIONAt. TKXTBOOK COMPANY. ALL RICHTS RKSKRVKO §1 222B— a Digitized by Google 2 GASOLINE AUTOMOBILES § 1 passengers and considerable baggage as well. They are used extensively in large cities, where they are very popular for making short business and pleasure trips. Motor busses are usually operated on certain main thoroughfares where there are no street-car Unes. They carry a large ntmiber of pas- sengers, some inside and some on top of the vehicle, and make regular trips at stated intervals between specified points, stopping to take on or to let off passengers at street crossings whenever signaled to do so. What are known as "sight- seeing** motor vehicles are automobiles especially designed for the transportation of a large niunber of passengers on sight- seeing trips, the places of interest along the selected routes being pointed out and described by the man in charge of the vehicle. At present, most automobiles are driven by internal-com- bustion engines using gasoline as fuel, the power developed by the engine being applied to the driving road wheels by means of suitably arranged power-transmitting mechanism. GENERAL ASSEMBLY OF THE AUTOMOBILE 2. There are two principal parts to an automobile, namely, the chassis (pronounced shah-see) and the body. As originally employed by the French, from whom it has been borrowed, the term chassis was used to designate only the frame of the automobile, but as now used it applies to the assembly of the running gear, consisting of wheels, axles, springs, and frame, and the power plant, which includes the engine and transmis- sion. In other words, the chassis includes everything but the body and its accessories. Before considering in detail the con- struction of the various parts of the chassis, attention will be given to the assembled parts of the automobile as a whole, the names, location, arrangement, purpose, and relations of the principal parts being noted. In conjimction with this, it should be noted that while automobiles produced by different manu- facturers greatly resemble one another in their general features, . there is naturally a great difference in the design of the details and the location and arrangement of many parts. For this Digitized by Google Digitized by Google 4 GASOLINE AUTOMOBILES § 1 reason, some of the details of the description of an automobile given here apply to only the particular motor car that is illus- trated, the general features of this automobile, however, being common to all of the same type. The various component parts of an automobile are here treated in a general way, and their construction, functions, operation, and management are explained in detail in the proper places. Fig. 2 3. Three illustrations of a Chalmers "Thirty-six" five- passenger automobile of the touring-car class are presented in Figs. 1 to 3. Fig. 1 shows a perspective side view of the right side of the automobile; Fig. 2, a view of the front com- partment looking toward the front and the right, the left front door of the body having been opened wide; and Fig. 3, a per- spective front view of the automobile. In connection with Digitized by Google § 1 GASOLINE AUTOMOBILES 5 this, it should be noted that the right side of a motor car is the one at the right of the observer when he is in one of the seats and is facing toward the front; under the same conditions, the left side of the motor car is at his left. The automobile shown is intended to seat two persons in front and three in the rear; the driver of this car sits at the right, but in some makes of automobiles the driver sits at the left. As far as possible, the same parts are lettered alike in Figs. 1 to 3, and all three illustrations should be referred to in reading the description. 4. Just in front of the driver's seat a is a steering wheel b at the top of the inclined steering column c. The guiding of Fig. 3 the car is accomplished by rotating this wheel through part of a revolution by hand. This rotation transmits motion to the front road wheels d, so as to turn them sidewise and change the direction of travel of the car. Pedals e, e\ and e", which can be seen only in Fig. 2, pro- ject through the floor of the front compartment, the board e\ being known as the toe hoard, because it is under the toes of the driver. For a similar reason, the part e^ of the front- compartment floor is known as the heel hoard. The clutch Digitized by Google 6 GASOLINE AUTOMOBILES § 1 pedal e is used for engaging the engine with the driving mechanism or disengaging the engine from it. The service" brake pedal e' is used for applying the brakes ordinarily employed in regular service to slow down the car or to stop its travel. The accelerator pedal e*\ often called the jooi- throttky is used for increasing or decreasing the speed of the engine. All three pedals are operated by the pressure of the driver's foot. At the right side of the car, and just forward of the driver's seat, are located two levers / and g. One, the emergency-brake lever f, controls a set of brakes independent of the service brakes, and is used for applying these brakes in an emergency, either in conjimction with the service brakes or alone in case the serv- ice brakes are out of order or it is considered undesirable to use them. The other lever g, which is called the gear-shift lever, the change-speed lever, and also the speed-control lever, is eniployed for adjtisting the power-transmitting mechanism, so that the speed of travel of the car can be varied through a greater range than that obtainable in the engine, and also for giving the car backward travel. This' arrangement is use- ful and generally necessary in order to obtain both high and low speeds of travel, and also in order to be able to climb steep hills. A gasoline engine such as is used on automobiles rotates in only one direction and cannot be run at very low speeds. The minimum speed of rotation of automobile engines is prob- ably never as low as 100 revolutions per minute and generally not lower than 200, 300, or even more, according to the size and form of the engine. On top of the steering wheel b are two small levers 6' and &" (see Fig. 2) for controlling the power and the speed of the engine. Each of these levers is attached to a shaft, or tube, that extends down inside the steering column that supports the steering wheel. One of the levers is for regulating the amount of fuel delivered to the engine, and the other is for regulating the instant at which the fuel is ignited. The lever b' for regula- ting the supply of fuel is called the throttle lever; the lever &" for regulating, or varying, the time of ignition is called the spark lever, or spark control. Digitized by Google § 1 GASOLINE AUTOMOBILES 7 On the right-hand side of the cowl board h, to the top of which the wind shield i is attadied, there is located a pear-shaped rubber btdb /. This bulb is connected by means of a flexible metallic tube f to a signal horn /", Fig. 1, located at the right side of the car and somewhat above the level of the floor of the car. The horn is blown by pressing this bulb with the hand. The purpose of the wind shield, which is hinged near its center so that it can be folded downwards, is to protect the occupants of the front seats from the impinging of air against the upper part of their bodies on accotmt of the forward motion of the car. 5. In the car here illustrated, the engine is arranged to be started by means of compressed air carried in a storage tank; the pressure in this tank is indicated on the starter air-pressure gauge k, Fig. 2, which is mounted on the board A. A push button k' is mounted on the dashboard /, and upon being pushed with the hand or the foot it admits compressed air to the engine. The pedal k'\ when depressed, starts a small air compressor that ptunps air into the storage tank. A spark coil m is mounted horizontally on the board h; it forms part of one of the two systems for igniting the fuel with which this car is equipped. One end of the spark coil pro- jects through the board h and carries a switch handle by means of which the ignition may be switched off entirely, or either ignition system switched on. The fuel for the engine of this car consists of a mixture of the right proportions of gasoline and air. This mixture is formed in a device called a carbureter , the gasoline being forced to the carbureter from the gasoline tank by air pressure, which is kept up automatically while the engine is running by a small engine-driven air ptmip. A hand air pump n is employed for pumping up air pressure in the gasoline tank after the tank has been filled, or when the air pressure in the tank is too low from any cause to force the gasoline to the carbureter. 6. The Chalmers "Thirty-six" automobile is equipped with two electric headlights. These, as shown at o. Figs. 1 and 3, are located at the front end of the car, and serve to light the road at night. A switch o\ Fig. 2, on the board A, is used Digitized by Google 8 GASOLINE AUTOMOBILES § 1 for switching the electric current on or oflE all the lamps; a measuring instrument o*\ called an ammeter, indicates the current that is flowing to the lamps. Combination oil-and- electric lamps p and q are used as signal lights at night to indi- cate the position of the car to other users of the road; these lamps can be seen in Figs. 1 and 3. The two lamps p are placed in front of the dash near its top; they are called side lamps or side lights, and are arranged to throw a clear white light ahead, thus indicating to an observer that the car is facing him. The lamp q, which can be seen only in Fig. 1, is called the tail-lamp, or tail-light; it is always arranged to show a red light toward the rear, thus indicating to an observer that he is looking at the rear of the car. The tail-lamp is also arranged to throw a white light at right angles to the car for the purpose of illiuninating the rear license tag in localities where cars are required by law to carry such tag. The side lamps and tail-lamp are arranged to use oil in addition to electricity as a precautionary measure, the oil burners being lighted when electric current for any reason is not available. While the engine is running, the electric current for lighting the lamps is furnished by means of a small current generator, called a dynamo, which is driven by the engine; when the engine is stopped, the electric current is furnished by a storage battery. 7. A radiator r, Figs. 1 and 3, is mounted at the extreme front of the car; its purpose is to cool the water used for keep- ing the engine cylinders from becoming too hot. The engine, which cannot be seen in any of the illustrations, is located in the front of the car, between the radiator and the dash and underneath the hood s, Fig. 1; beneath the engine is placed a mud-pan, or sod pan, t, which protects it from mud and dust. At the extreme front of the car is a crank-handle, or starting crank, u, Fig. 3, which is used for starting the engine if the compressed-air starter for any reason fails to start it. An oil sight-feed glass v. Fig. 2, is placed on the dash to show whether or not the oil pump that lubricates the engine is work- ing properly; a carbureter adjustment w is also carried on the dash. A speedometer x indicates the speed of the car in miles Digitized by Google § 1 GASOLINE AUTOMOBILES 9 per hour. A valve operated by the handle i'" shuts off com- munication between the air tank and the starting button. The body of the car, consisting of the front and rear seats, together with the necessary doors to give access to the seats, is moimted on the frame of the car; it is fitted with a folding top y, shown folded in Fig. 1 and covered by a slip top cover y\ The car is driven by the rear wheels d\ which are rotated by the engine. Mud-guards, or fenders, d'' are placed over all the wheels to prevent mud from splashing over the occupants of the car; the front and rear fenders are connected to running boards du which serve as steps to facilitate entering and leaving the front and rear compartments of the body. Springs are interposed between thefratne z of the car and the axles on which the road wheels are mounted, in order that the occupants may ride over the road in comfort. METHODS OF PROPELLING THE AUTOMOBILE DEFINITIONS 8. An automobile is propelled by rotating either all four wheels, or only the rear wheels, or only the front wheels, by some suitable mechanism driven, in tiun, by the engine. The method of driving all four wheels simultaneously has been, and still is, used to a sli^t extent on one make of motor truck, but it is not employed on any regularly built pleasure cars. Propelling an automobile through its front wheels has been tried out successfully, but no cars embodying this feature are r^ularly in the market. Practically all automobiles are propelled by rotating their rear wheels. Power may be transmitted to the rear wheels (1) by chains and sprockets, thus making the car chainrdriven; (2) by means of a rotating shaft and either bevel gearing or worm-gearing, thus making the car shaft-driven; (3) by friction gearing, thus making it frictionrdriven; (4) by a combination of friction gear- ing and chain and sprocket, thus making it friction-and-chain driven. Digitized by Google i 10 Digitized by Google 91 to Digitized by Google 12 GASOLINE AUTOMOBILES § 1 Chain-driven cars may have both rear wheels driven by a single chain, which is usually located near the center of the rear axle. In such a case, the wheels are driven by shafts rotated by means of the chain, the shafts being inside the rear axle, which is then known as a live axle, and the car is spoken of as a single-chaifirdrive car. Pleasure cars employing this method of propulsion, however, are practically obsolete. Each rear wheel may be driven by its own chain, in which case no part of the rear axle revolves. Such an axle is spoken of as a dead rear axle, and a car thus driven is said to have a double- chain drive, or, since the chains are naturally located at the sides of the car, it is often spoken of as a side-chain-drive car. Although the double-chain drive is very common in motor trucks, it is employed but very little in pleasure cars at present. Most of the automobiles in use in the United States and Canada employ a live axle and are shaft-driven. NOMENCLATURE OF TYPICAL CHAfiU9L9 PARTS 9. Two views of the chassis of a Studebaker **20*' shaft- driven automobile are shown in Figs. 4 and 5, on which the same parts have the same reference figures. Fig. 4 is a plan view, the steering column being broken off so that the steering wheel and throttle and spark levers thereon will not hide the toot-levers, or pedals, and Fig. 5 is a side elevation partly in section. Beginning at the front end of the chassis the various parts are numbered and named as follows: i, Front road wheels 8, Arms of steering knuckles S, Front axle 9, Steering rod or drag link, one S, Front springs, of the semielliptic end of which is attached to type arm 8 of left steering knuckle, 4, Front end of frame, forming the other end of the steering hanger for front spring rod being connected to the 5, Side members of frame actuating lever arm of the 6, Starting crank for starting steering gear engine 10, Radiator in which water for dr- 7, Tie-rod, distance rod, or cross- culation in engine water- connecting rod with adjust- jackets is cooled able end joining arms of 11, Fan to create circulation of air steering knuckles or pivots through radiator, thus cooling Digitized by Google §1 GASOLINE AUTOMOBILES 13 water therein when car is S7, standing still while engine is B8, in operation, and aiding dr- £9, dilation while car is running IS, Cross-member of frame SO, 13, Gear-driven pump for drcula- SI, ting cooling water i4t Water-delivery pipe from pump to cylinder water-jackets ; also SB, called water-inlet pipe and pump-outlet pipe SS, 15, Water-outlet pipe conveying water from cylinder water- Si^, jackets to radiator S6, 16, Large fan-belt pulley on end of engine cam-shaft S6, 17, Small flanged fan-belt puUey 18, Bracket for supporting spindle on which small fan-belt pulley and fan rotate 19, Cylinder casting comprising S7, four cylinders, which are cast S8, as a monobloc; that is, com- bined into a single casting S9, fSO, Water-jacket surroimding upper 40, part of cylinder and cast in- 4/, t^;ral with it £1, Cylinder cover closing upper water-jacket opening ££, Plugs closing openings above the eight valves, which are 4^, put in place or removed 4S, through the openings; the spark plugs (not shown) are placed in the valve plugs over 44t the four intake valves; pri- 4^, ming cocks (not shown) are 4^, fitted to the valve plugs over the four exhaust valves £3, Exhaust pipe manifold 4^» £4, Muffler ^, £S, Intake openings of cylinders, to which intake manifold is fitted 4^, 26, Exhatist openings of cylinders, to which exhaust manifold is fitted 50, Dash Steering column Steering-gear-case cov«r at lower end of steering column Steering wheel Quadrant on which are mounted throttle lever and spark con- trol lever Clutch pedal for operating clutch Engine flywheel containing dutch Service brake pedal Accelerator pedal, often called foot-throttle Service brake rods leading to actuating mechanism of ex- ternal contracting band brakes on brake drums bolted to rear wheels Rear wheels Rear springs, of the scroll full- elliptic type Spring shackle Emergency-brake lever Emergency-brake-lever rods leading to actuating mechan- ism of internal expanding emergency brakes on inside of brake drums Emergency-brake equalizer bar Quadrant, or bracket, for emer- gency-brake lever and gear shift lever Gear shift lever Gear shifting rods Universal-joint assembly trans- mitting power from dutch to driving shaft Driving, or propeller, shaft Torsion tube housing the pro- peller shaft Transmission case forming part of rear axle and containing sliding-gear transmission Right and left rear-axle housings Digitized by Google U GASOLINE AUTOMOBILES § 1 61, Radius rods, or diagonal brace 66, Exhaust pipe, connecting rods exhaust manifcdd with muf- 62, Service-brake shafts fler 6S, Emergency-brake shafts 66, Cross-member of frame, form- 64, Tumbuckles on brake rods, used ing forward support for tor- for adjusting their lengths sion tube SHAFT-DRIVE DBIVINQ-MECHANISH ARRANGEMENTS 10. In shaft-driven cars, there are in use at present several diflFerent arrangements of the engine and clutch, the transmis- sion, and the rear axle with reference to one another. Each of the various arrangements has its own adherents among auto- mobile manufacturers. The preference of automobile purchasers has caused the following general arrangment to be followed in practically every shaft-driven pleasure car: The engine, with which the clutch, in most cases, is combined, is placed at the front end of the car, with its crank-shaft in the direction of the length of the car. The transmission is then placed to the rear of the engine. In the great majority of cars, use is made of an engine with either four or six vertical cylinders. In both the Edwards-Knight car and the Winton six-cylinder car, the clutch does not form part of the engine, but is contained in the same casing as the transmission. This, however, does not change the general arrangement mentioned. In n^my cases the engine, the clutch, and the transmission are combined into a single tmit; the com- bination is then spoken of as a unit power plant. An example of each one of the most common of the different driving-mechanism arrangements is here given in the form of a top view of the chassis of a car actually manufacttired. The different cars presented do not constitute the only examples of automobiles employing the particular arrangement of the driving mechanism each one illustrates; those shown, however, have been selected because they clearly exhibit the salient features of each driving-mechanism arrangement. !!• In Fig. 6 is presented a top view of the chassis of a Ford, model T, automobile. In this car is employed a unit power Digitized by Google I u Digitized by VjOOQ IC 16 GASOLINE AUTOMOBILES § 1 plant, the top of the cylinders showing at a. The clutch and transmission are enclosed in the casing 6, and the drive to the rear axle is by means of a shaft endosed in the housing c. The engine is bolted rigidly to the frame d of the car. The rear axle e is connected to the frame in this case by a single cross- spring /; consequently, its distance from the frame is changing continually with different loads in the car and under different road conditions. Furthermore, the center line of the crank- shaft and the center line of the driving shaft are not normally in the same straight line, although they always intersect. From this it can readily be seen that a jddding connection must be made between the power plant and the driving shaft so as to take care of any original disalinement, as well as that caused by the compression and extension of the rear body spring. This jddding connection is, in practice, made by a so-called universal joint. In the case of the Ford car under discussion, a single universal joint is employed at the forward end of the propdler shaft, the joint being endosed in the casing g. The application of the power of the engine to the driving wheds tends to rotate the whole rear-axle housing around its center line in a direction opposite to that in which the wheels turn, and this tendency must be coimteracted by some means. In the Ford car, the propdler shaft housing c is rigidly bolted to the rear axle e and is connected by means of a ball joint to the casing g; this housing c thus resists the torsional, or tiuning, effect due to appljring the engine, and hence is often called the torsion tube. This tube also resists the tendency of the axle housing to rotate, when the brakes inside the brake drums h of the rear wheds are applied, in a direction opposite that in which rotation tends to take place when the car is driven by the engine. In the Ford car, the rods i, called radius rods, hold the front axle substantially at right angles to the frame d. The rods /, which also are called radius rods, tie the torsion tube and rear axle ends together, and hence serve as tie-rods. The rear axle is confined lengthwise by hinging the torsion tube at its forward end to the rear of the power plant. The arrangement of the driving mechanism is, briefly, as follows: A unit power pdant drives the rear wheds through a Digitized by Google 17 222B— 3 Digitized by Google 18 GASOLINE AUTOMOBILES § 1 propeller shaft having a single universal joint at its forward end, the shaft being endosed in a torsion tube. 12. A top view of the chassis of an Oakland, model **45,** automobile is shown in Fig. 7. This car employs a tmit power plant. The top of the eilgine cylinders is shown at a; the clutch is next to the engine and is contained in the casing 6; and the transmission is in the casing c. The propeller shaft d is not housed, and a flexible connection between the rear axle e and the transmission is made by means of two tmi- versal joints /, one at each end of the propeller shaft. Rota- tion of the rear axle housing in either direction tmder the driving or braking stresses is prevented by a torsion rod, or torsion bar, g. This rod is anchored at its rear end to the rear-axle housing, and through a somewhat flexible connection at its front end it is attached to a cross-member h of the frame i of the car. The frame is supported on fotu* springs. The front springs, running lengthwise of the car, are placed underneath the frame and hence cannot be seen in this top view; they are of the semielliptic type, as is shown in S, Fig. 5. The two rear springs / are also placed lengthwise of the car, but they are outside of the frame and can therefore be clearly seen in the illustration. These rear springs are of the three-quarter elliptic type, con- sisting of one-half of the upper member and the whole lower member of the full-elliptic spring shown at 38, Fig. 5. Support- ing the frame of the car on four springs placed lengthwise is by far the most common method of support. The front ends of both the rear and front springs are hinged to the frame, and as they are also bolted at their middle to the front and rear axles, they serve to hold the two axles at right angles to the frame and also confine them lengthwise; hence, no radius rods are fitted or required. The arrangement of the driving mechanism is, briefly, as follows: A tmit power plant drives the rear wheels through an tmhoused propeller shaft with universal joints at each end, a torsion rod, or torsion bar, preventing the rotation of the rear- axle housing. Digitized by Google 19 Digitized by Google 20 GASOLINE AUTOMOBILES § 1 13« A top view of the chassis of a Rambler, "Cross-Country" model, automobile is shown in Fig. 8. In this car, the engine and the clutch form one tmit, the engine being shown at a and the clutch at 6. The transmission c is motmted on the end of the propeller-shaft housing d, which, in turn, is rigidly bolted to the rear-axle housing e. This can be seen very clearly in Fig. 9, which shows the rear axle e, together with the propeller-shaft housing d and the transmission <;, removed from the chassis. As the rear axle and the transmission are permanently alined, the propeller shaft inside the housing d, which also serves as a torsion tube, has no tmiversal joints. The transmission is hinged to a cross-member /, Fig. 8, of the frame g. The power Pig. 9 of the engine is transmitted through the clutch to the trans- mission through a short driving shaft h having a tmiversal joint at each end. The front springs are hinged to the frame at their forward end and bolted at the middle to the front axle; thus, they confine the axle lengthwise and also hold it at right angles to the frame, and hence no radius rods are needed. The front springs are placed directly tmdemeath the frame. The rear springs i, Fig. 8, are on the outside of the frame, and their lower half is bolted at the middle to the rear-axle housing. The forward ends of the lower half of the rear springs are attached to the frame, and the rear ends to the upper half of the rear springs, by swinging links, called shackles; consequently, the rear axle is not confined lengthwise of the car by the rear springs and hence radius rods /, are employed to hold the rear axle, at all times, at right angles to the frame, as well as to confine it lengthwise. Digitized by Google § 1 GASOLINE AUTOMOBILES 21 Summed up briefly, the arrangment of the driving mechanism is as follows: The engine and the clutch form a unit that I drives the transmission through a short shaft with double universal joints, the transmission being carried by the forward end of the torsion tube enclosing the propeller shaft. Digitized by Google 22 GASOLINE AUTOMOBILES § 1 14. A top view of the chassis of an Overland automobile model 69, is presented in Fig. 10. In this car, the engine and the clutch fonn a unit, the engine being shown at a and the clutch at 6. The transmission c is motmted on the rear axle d, and the propeller shaft is housed inside the torsion tube e, which is bolted to the forward end of the transmission case and is hinged to a cross-member / of the frame. The power of the engine is transmitted from the clutch to the driving shaft through a single imiversal joint g. Some other manufacturers of automobiles using the same arrangement of engine, transmission, and rear axle as the Overland here shown employ two universal joints between the clutch and the driving shaft. The front springs are semielliptic, are placed directly imder the frame, and are hinged to it at the front. Their rear ends are shackled to the frame, and they are bolted, at their middle, to the front axle, which is thus confined lengthwise of the car by the springs. The rear springs are of the three-quarter eUiptic type, like the rear springs of the Chalmers car shown in Fig. 1. The lower half of each rear spring is shackled at the front to the frame, and at the rear to the upper part of the spring, and is bolted at the middle to a rotatable spring seat on the rear-axle housing; consequently, the rear springs in themselves do not hold the rear axle lengthwise of the frame. This is done, however, by hinging the forked forward end of the torsion tube to the cross-member /, as shown, and tying the front end of the torsion tube to the rear axle ends by the tie- rods h. This arrangement of the driving mechanism, summed up briefly, is as follows: The engine and the clutch form a xmit that drives the propeller shaft housed in a torsion tube through either a single universal joint or through two imiversal joints, the transmission being carried by the rear-axle housing. 16. In Fig. 11 is illustrated a top view of the chassis of a Packard, model 48, automobile. In this car, as in the Overland, the engine and the clutch form a imit. The engine is shown at a, and the clutch is enclosed in an extension b of the crank-case. Digitized by Google i 23 Digitized by Google 24 GASOLINE AUTOMOBILES § 1 The transmission is mounted in a casing c that is bolted to the rear-axle housing, the power being transmitted from the engine through a propeller shaft d that is not enclosed. The propeller shaft is provided with two tmiversal joints e and /, which allow for lack of alinement between the engine shaft and the rear axle. A torsion rod g is attached at one end to the transmission casing, and at the other end to a cross- member h of the frame, to which it is connected by means of a spring connection that allows for vibration due to play of the body springs. The front springs i are of the semielliptic type, being shackled to the frame at the rear by means of a link and bolts and hinged to it in front. The rear springs / are of the three-qtiarter elliptic type, like those on the Overland and Chalmers car, the lower half being shackled to the frame and to the upper part, and the upper quarter being attached by spring clips to the frame. The rear springs are fastened to the axle by spring clips k. The rear axle is held in alinement with the frame by two radius rods located directly below the side members of the frame. On accoimt of their position they cannot be seen in Fig. 11. The foregoing arrangement summed up briefly is as follows: The transmission is mounted on the rear axle and is driven from the engine through an exposed propeller shaft with two xmiversal joints, the tendency of the rear axle to turn being overcome by a separate torsion rod. 16« Another form of shaft-drive mechanism, different from any thus far described, is illustrated in Fig. 12, which shows the top view of a 35-horsepower chassis of the Fiat automobile. In this car, the engine, with its clutch, and the transmission, are enclosed in separate casings. The tops of the four engine cylinders, which are cast in one piece, are shown at a; the clutch is enclosed in the casing 6, which is bolted to the flywheel, and the transmission is carried in the housing c. Power is transmitted to the rear axle through a propeller shaft that turns inside of the tube d, the tube being an integral part of the pressed-steel axle housing. A coupling is provided in the short Digitized by Google 26 Digitized by Google 26 GASOLINE AUTOMOBILES § 1 shaft e, which connects the clutch and the transmission, and a universal joint / is located at the forward end of the propeller shaft to allow for any disalinement. The torsion tube d, which prevents rotation of the rear axle housing, is supported at the front by a yoke g which is hinged to the frame of the car. The front springs h are of the usual semielliptic type, and the rear springs i, of the three-quarter elliptic type. The front springs are^ hinged at the front and shackled at the rear, while the rear springs are shackled both at the front and the rear and are attached to the rear axle by means of the spring clips /. All four of the springs are placed lengthwise with the frame. Besides performing its usual function, the propeller shaft housing d keeps the rear axle in alinement with the remainder of the car. In brief, the arrangement shown in Fig. 12 is as follows: Power is carried from the engine and clutch through a short shaft and coupling to the transmission, which is supported by the frame; thence, through a single universal joint and an enclosed propeller shaft to the rear axle. 17. Still another form of arrangement of the driving mechanism in a shaft-driven car is illustrated in Fig. 13, which shows the chassis of the Reo the Fifth automobile. In this car, the propeller shaft is provided with two universal joints and is not housed, separate torsion rods being used to prevent the rear-axle housing from tiuning. The tops of the engine cylinders, which are cast in pairs, are shown at a. The clutch is enclosed in the case 6, and the transmission, in the housing c, power being transmitted to the rear axle through the propeller shaft d and the imiversal joints e and /. The clutch is coimected to the transmission by the shaft g, which is provided with the flexible coupling h to allow for lack of alinement. The rear-axle housing is prevented from rotating by two torsion rods i (one of which is directly tmder the other) that are rigidly attached to the differential casing at the rear, and fastened by a flexible connection to the cross- member y at the forward end. The front springs, which are hidden from view by the frame, are of the semieUiptic type and are attached in the usual manner. Digitized by Google i Digitized by VjOOQ IC 28 GASOLINE AUTOMOBILES § 1 The rear springs k are of the three-quarter elliptic type; the bottom half of each one is hinged to the frame at the forward end by means of a bracket and bolt, and is shackled to the upper part of the spring at the rear. These springs are rigidly bolted to the rear-a^e spring seats and serve to hold the axle in alinement with the remainder of the car. Summed up briefly, the arrangement is as follows: The power developed by the engine is transmitted through a clutch and a short shaft and flexible coupling to the transmission; thence, by means of an unhoused propeller shaft having two universal joints, to the rear axle, a separate torsion member being employed to prevent the axle housing from turning. CHAIN-DBIVE DBIVINO- MECHANISM ARBANOEMENTS 18. Practically all chain-driven pleasure cars now being built are of the double chain-driven type. This type of car is provided with a countershaft that is driven from the engine through a propeller shaft and that, in turn, drives the rear wheels through two chains. .19. A top view of the chassis of a six-cylinder, type 19, Chadwick automobile is presented in Fig. 14, which shows the arrangement of the various parts. In this car, the transmission and the engine with its clutch are separate imits. The tops of the engine cylinders are shown at a, the clutch being incorporated in the flywheel 6; the transmission is enclosed in the casing c, which is located at the coimtershaft d. Power is carried from the clutch to the transmission by an tmhoused propeller shaft that is located directly under the longitudinal brace e and is provided with a imiversal joint at its rear end. It is to be noted that the coimtershaft is driven exactly like the rear axle in some forms of shaft-driven cars, except that only one imiversal joint is required because the coimtershaft is carried by the frame, and hence the alinement is not disturbed by spring deflection. From the countershaft, the rear wheels are driven by chains enclosed in the cases / and g. These chains run on sprockets attached to the ends of the countershaft and to the Digitized by Google § 1 GASOLINE AUTOMOBILES 29 wheel hubs. The wheels turn on a sta- tionary, or dead, axle h. The countershaft housing , or differential housing, i is prevented from turning by the braces /, and the rear axle and countershaft are held in alinement with each other by means of radius rods, which form a portion of the chain cases. The front springs, which are beneath the frame and therefore not visible in the illus- t tration, are of the ^ semielliptic type and are shackled at the rear and hinged in front. The rear spring is of the platform type. It is composed of the two-side members fe, which are ordinary semielliptic springs, and the rear member /, which is an inverted semielliptic spring shackled to the rear ends of the side springs. The forward ends of the side mem- bers k are shackled to the frame, and the rear member I is attached Digitized by Google 30 GASOLINE AUTOMOBILES § 1 to it by means of a bracket at its center. Thesprings are rigidly attached to the rear axle, which is held in alinement by the two raditts rods. Briefly, the arrangement of the driving mechanism of this chain-driven car is as follows: The power of the engine is transmitted through a clutch, a propeller shaft, a universal joint, and a transmission to a countershaft, from which the rear wheels are driven by means of chains and sprockets, the propeller shaft being imhoused, with braces holding the coimter- shaft casing in position. BODIES AND ACCESSORIES TYPES OP BODIES GENERAL CLASSIFICATION 20. The body is that part of an automobile which pro- vides accommodations for the carriage of passengers. It is the superstructure that rests on the frame of the chassis, to which it is fastened in such a way that it may readily be removed to facilitate repairs or to make possible the substitution of one style of body for another. 21. Bodies may be classified under two heads, namely, open bodies and closed bodies. The former are used for run- ning around town and for touring in summer, while the latter are popular for winter use. The folding tops with which the open bodies are usually equipped afford protection from sun and rain to both the driver and the passengers. Closed bodies are often fitted with side curtains, by means of which the space between the driver's seat and the wind shield at the dash is entirely closed, thtis protecting the driver in extremely cold winter weather. The side curtains are provided with large celluloid windows through which can be seen clearly the mirror that gives the operator a good view of the road at the rear of his car. Closed bodies have recently been brought out in Digitized by Google § 1 GASOLINE AUTOMOBILES 31 which the driver is protected in the same maimer as the pas- sengers; that is, the driver's seat is fully enclosed by the dash and wind shield in front and by permanent side doors with glass windows at the sides. Closed bodies are frequently provided with means for heating them, and they are often supplied with luxurious accessories, such as speaking tubes, flower holders, mirrors, and electric lights. OPEN BODIES 22. Types of Open Bodies. — ^Automobiles having open bodies consist of two general types — runabouts and touring cars. The term runabout is applied in a general way to all Ught cars having a single seat for two or three passengers, or a seat in front for two passengers and a seat behind, called a rumble seat, for one passenger. The touring-car body differs from the runabout body in that it has a tonneau, or rear-seat, sec- tion made wide enough to seat comfortably either two or three persons. The tonneau is sometimes also provided with two side seats that can be folded up out of the way when not in use, so that the seating capacity of a touring car may be four, five, six, or seven persons. 23. Rrmabouts. — ^In Fig. 15 (a), (6), and (c) are shown three automobiles belonging to the runabout class. View (a) shows an ordinary two-passenger runabout without doors, the space on the sides between the dash and the seat being left open. A tool chest nriay be carried on the rear, and in some cars the gasoline tank is also carried in this position. Some- times a supplementary, or rumble, seat is placed on top of the tool chest, thus adapting the car for three persons. 24. The open-door runabout just described has gradually given way to the more popular foredoor, or torpedo, runabout, an example of which is presented in view (6). A characteristic featiu-e of the torpedo body is the closing of the space on the sides between the seat and the dash by doors called foredoors. Sometimes a foredoor is placed on only one side of the car and a blind door, or one that cannot be opened, on the other Digitized by Google 32 GASOLINE AUTOMOBILES §1 side. The dash on this type of car is usually extended toward the driver's seat in the form of a cowl^ as is shown in the illustra- tion, thus affording protection to the dash equipment. How- ever, some torpedo bodies are made with a straight dash. Some makers style this form of runabout a roadster, and occa- sionally the seat is made wide enough to accommodate three, when it becomes a sociability torpedo roadster. The term road- ster is sometimes applied to a four-passenger car of the touring- car type. 25. The raceabout, or semiracer, as shown in Fig. 15 (c), is a two-passenger runabout having the seats placed very low and the steering colimm inclined, or raked, at an extreme angle. This type of car is usually provided with a high-power engine and is not much used for ordinary purposes. The racer differs from the semiracer in that it is stripped of fenders, running boards, and all body work except that actually required to support the two individtial seats with which such cars are fitted. This car is, of course, used only for racing purposes, and is pro- vided with a high-power engine and an tmusually large gasoline tank. Digitized by Google § 1 GASOLINE AUTOMOBILES 33 26. Touring Cars. — ^The common type of touring car, such as is illustrated in Fig. 15 (d), is almost invariably fitted with foredoors, as well as doors closing up the space on the sides between the front and the rear seats. Ordinarily, the front seat accommodates the driver and one passenger and the rear seat is made wide enough for three passengers. A seven- passenger car is made by adding to this seating arrangement two folding side seats that are carried in the tonneau. In some cases, the control levers are located in the center of the car, so that both foredoors are used, and in other cases the con- trol levers are on the side and the door on that side is a blind door. In still other cars, the control levers are located on the side and both foredoors are used, although it is rather incon- venient to use the door on the same side as the levers. The dash is often made with a cowl in order to protect the equip- ment located on it. The touring car is usually provided with a top that can be folded back out of the way when not in use. 27. In Fig. 15 {e) is shown the so-called haby tonneau, or toy tonneau, type of touring car. This form of body differs from the common type of touring-car body in that the rear seat provides room for only two passengers, and the tonneau is shorter, so that there is less room between the rear seat and the back of the front seat than in the regular touring car. The car shown in the illustration is not provided with foredoors, but it has doors that close the space on the sides between the seats; foredoors, however, may also be fitted. 28. The term phaeton is very often appUed to cars of the touring-car class that carry four passengers and are similar in appearance to the toy-tonneau type. As previously men- tioned, some makers designate one style of four-passenger touring car as a roadster. What is commonly known as a close-coupled touring car is one having a body of the toy, or two-passenger, tonneau variety, the rear seat being located so that the passengers are either in front of the center line of the rear axle or just over it. In touring cars of the regular type, the rear-seat passengers are back of the center line of the rear axle. 222B— 1 Digitized by Google 34 GASOLINE AUTOMOBILES §1 CXiOSED BODIES 29. Types of Closed Bodies. — Closed bodies for auto- mobiles are made in a variety of forms, from those used on the taxicab, which is built for service only, to the palatial body of the high-priced limousine, upon which no expense is spared to secure the greatest possible amount of beauty and luxury. The popular forms of closed bodies are the coup4, the litnousine, the Berline body, the landaulet, and the taxicab. 30. CJoui)^. — ^The coup^, an example of which is shown in Fig. 16 (a), is a type of closed body usually designed for carry- PlG. 16 ing two or three persons facing forwards. A folding seat is sometimes provided, in which case the additional passenger sits with his back toward the front of the car. This car is Digitized by Google § 1 GASOLINE AUTOMOBILES 35 especially adapted for the tise of physicians in cold and stormy weather, for women out shopping, and so on. 31. LLmousiiie. — For private use, the limousine body is the most poptilar of bodies of the closed type. It affords a maximum of comfort, combined with an elegant luxurious- ness not common to other types of closed bodies. As shown in Fig. 16 (6), the upper part of the doors and body is made up of glass set in a sash to form windows that may be lowered into recesses provided to receive them. Thus, when the weather is warm the passengers need not suffer from heat or lack of fresh air. The glass partition back of the driver's seat is some- times arranged so as to swing upwards against the roof, from which it is suspended. The driver's seat is sometimes enclosed by foredoors, as in view ((;), such a body being styled a foredoor limousine. 32. Berline Body. — ^The Berline type of body is shown in Fig. 16 (c). This body differs from the limousine bgdy in that the front seats are entirely enclosed in the same manner as the rear seats. It is also a very elegant body and is tised only on high-priced cars. 33. Landaulet. — -For use in the suburbs or in the city, a type of closed body known as the landaulet is very popular. As shown in Fig. 16 (d), an extension of the top covers the driver's seat, and a wind shield in front affords further protec- tion to the driver in cold and rainy weather. In warm, pleas- ant weather, the glass panels back of the driver, at the sides, and in the doors may be let down into spaces provided to receive them, and the rear portion of the body, being made of flexible leather, may be folded down and back, transforming the pre- viously closed body into one having some of the character- istics of those of the open type. When, as is sometimes the case, provision is made for removing the top over the driver's seat, the framework back of it, and the upper part of the frames of the side doors, the body is converted into one more nearly like those of the fully open, or touring type. Landaulets are usually provided with folding seats for two passengers, who must ride backwards, the fixed rear seat Digitized by Google 36 GASOLINE AUTOMOBILES § 1 accommodating two or three passengers facing forwards. In the horse-drawn vehicle from which the landaulet automobile body takes its name, there are two seats facing each other and the top is made in two sections so as to permit of folding them back and thtis make an open carriage. 34. Taxicab. — ^The term taxicab is applied to automo- biles of the closed-body type that are designed for hire to the general public. To adapt it for use in summer as well as in winter, in fair as well as in stormy weather, the taxicab body, as shown in Fig. 16 {e), is made with a top that may be folded down and back, as in the landaulet. The glass windows in the side doors may be lowered into recesses provided for them, as may also the windows at the back of the driver's seat. The taxicab body is usually provided with one regular seat, which comfortably accommodates two persons, and two folding single seats, so that the car will carry foiu* passengers. The driver's seat, which is only partly protected, is sometimes a single seat, thus providing a place alongside the driver in which baggage can be carried. Very often this type of car has the control levers located in the center. 36. Miscellaneous Body Types. — Other types of auto- mobiles employing closed bodies are known variously as the brougham, the demilimousine, and the touring coach. The brougliam and the demlllmouslne greatly resemble the limousine, differing from it principally in having a smaller seating capacity. The touring coacli is a car fitted with a closed body designed to accommodate several persons besides the driver. Large baggage-carrying capacity is provided at the rear and on top of the coach, within which are provided toilet accessories and every convenience for touring. These bodies are commonly made to order and are fitted to standard and special chassis. Digitized by Google § 1 GASOLINE AUTOMOBILES 37 ACCESSORY FITTINGS AUTOMOBILB TOPS 36. Practically all automobile tops now in use belong to one of two types; they are either cape tops or canopy tops. 37. Automobiles having open bodies, that is, runabouts and totiring cars, are provided with flexible cape tops that Pig. 17 can be folded back out of the way when not in use. Fig. 17 illustrates a cape top in place on a seven-passenger touring car. This top may be folded back and protected by means of a slip cover, when it will appear like the top seen in Fig. 15 (d) or {e). Pig. 18 A cape top applied to a two-passenger runabout is shown in Fig. 18. When folded back, this style of top has the appear- ance of that shown in Fig. 15 (a) or (6). Digitized by Google 38 GASOLINE AUTOMOBILES § 1 Cape tops are provided with side curtaiiis, which are intended for tise in winter or in stonny weather. When not in tise, these curtains are ordinarily folded and carried under the rear-seat cushion or in pockets especially provided for them. 38. Canopy tops are the rigid, non-folding tops used on closed and semidosed bodies, as shown in Fig. 16. They were originally used on open bodies, but because they were not readily" detachable and had to be entirely removed when they were not needed, their use was discontinued on this type of body. WIND SHIELDS 39. A wind sMeld is a device attached to the dash or the cowl of an automobile body for the purpose of protecting the occupants of the car from dust, rain, cold winds, etc. Wind shields consist of glass supported by metal frames, and they are usually so constructed that they may be folded or tilted at different angles. In some cases, the glass is in one piece, form- ing a solid mind shield, and in other cases it is in sections, which are either hinged together, forming an ordinary folding wind shield or a zigzag wind shield, or hinged separately, so that the top section can be tilted independently of the other, forming a rain vision wind shield. Practically all manufacturers include a wind shield of one of these types in the regular equipment on their cars. In some of the older cars fitted with a cape top the place of the windshield was taken by a storm front, which consists of a waterproofed fabric fitted with a large celluloid window and extending vertically from the dash to the top. This storm front could be rolled up in fair weather. 40. A solid wind shield mounted on the cowl of the dash of a touring car is shown in Fig. 19 (a). This type of wind shield is made of a single piece of glass a contained in a metal frame fe, and is hinged at c and d so that it can be inclined to any angle. When not in use, it can be inclined forwards over the cowl and out of the way. Digitized by Google §1 GASOLINE AUTOMOBILES 39 41.' An ordinary folding wind sMeld attached to the dash of a touring car is shown in Fig. 19 (fe). This syle of Pig. 19 wind shield is composed of two sections a and 6 that are hinged at c and d. The hinges are made so that the top part a will stay in any position in which it is placed; hence, it can be Digitized by Google 40 GASOLINE AUTOMOBILES § 1 swung down below the line of vision of the driver as shown, or placed in a vertical position above the section 6, giving the maximnm height. This style of wind shield is perhaps more used than any other type. 42. The zigzag .wind sliield, which is so named because the lower part is always inclined at an angle, is shown in Fig. 19 (c). Except for the position of its lower section, this style of wind shield is the same as the ordinary folding type. However, it is not employed so extensively as the folding wind shield, its use being confined to the smaller cars, as, for instance, runabouts and roadsters. 43. The raln-vlsion wind slileld, as illustrated in Fig. 19 (d), is also made up of two sections; it differs from the two preceding types in that the upper section is hinged near its middle or at its top so that it can be tilted, as shown. When in this position, a good view of the road can be obtained between the sections; this is an advantage in stormy weather when the glass may become wet and blurred. The upper section may also be swtmg down, as in the folding type, by means of the arms that support it, these being hinged at the top of the lower section. In some instances the lower section of a rain-vision wind shield is so arranged that it may be inclined so as to deflect a current of air into the front compartment; in that case it is spoken of as a ventilating rain-vision wind shield. 44. In a strict sense, a speedometer is an instrument that indicates the speed, either in miles or in kilometers per hour, at which an automobile is traveling at any given time. It has become customary, however, to combine with the speedometer one or two odometers, which are instruments that measure either in miles or in kilometers, the distance traveled by an automobile. When only one odometer is used, it registers consecutively the nimiber of miles or kilometers traversed by the car; no means are provided for setting the instrument back to zero, and it is Digitized by Google § 1 GASOLINE AUTOMOBILES 41 spoken of as a season odometer. When a second odometer is provided, it is always fitted with a device by which it can quickly be set back to zero at the beginning of each trip; hence, it is called a trip odometer. The setting-back device is always arranged so that its use will not affect the reading of the season odometer. At least one manufactiu'er incorporates in his speedometer a grade meter, which registers, in per cent., the grade that the car is ascending or descending. Thtis, as the term is used at present, a speedometer is expected to have at least one odometer incorporated in it, and it may have two odometers and also a grade meter. 45. The speedometer is usually driven from one of the front wheels; the reason for this is that these wheels have practically no slip on the road in comparison with the rear wheels, or in other^ words, their speed is always in proportion to the car speed. The speedometer is usually mounted on the dash or the cowl board, where it can readily be seen by the driver. In applying a speedometer to a car, care must be taken to obtain gearing that is suitable for the size of the front tire; thus, a 36-inch front tire requires different gearing for the speedometer than a 30-inch tire. Hence, the size of the front tire should always be specified in an order for a speedometer, so that the dealer will be enabled to forward the proper gears. When improperly geared, the speedometer will indicate a wrong speed as well as a wrong distance. 46. In the speedometers most widely used, the speed indi- cation is obtained (1) by centrifugal force, (2) by magnetic induction, (3) by pressure exerted by a fluid, or (4) by an electric current. In centrifugal speedometers, either the principle of the ordinary fly-baU governor commonly used on steam engines is employed, or the so-called ring governor is used. In either case, centrif- ugal force acts on weights whose center of gravity is outside the axis around which they revolve, the weights being revolved by a flexible shaft driven from one of the front wheels. Centrif- ugal force tends to make these weights fly away from the axis of rotation. Digitized by Google '42 GASOLINE AUTOMOBILES § 1 In magnetic speedometers, either a permanent magnet or a series of pennanent magnets is revolved by a flexible shaft from one of the front wheels, the revolving magnet or magnets exercising a pull on a drum that can. oscillate against the resist- ance of a coiled spring. In fluid-pressure speedometers, either a liquid or a gas is acted on by a suitable device that creates a pressure proportional to the speed of the wheels, which pressure is indicated on a dial graduated to miles or kilometers per hour. In electric speedometers, a very small dynamo is driven by one of the front wheels, the voltage of the current delivered by the dynamo being measured by a voltmeter car- ried on the dash of the car, this voltmeter being graduated to miles per hour instead of to volts. The voltage of the dynamo used is directly proportional to the speed ("^ at which its armature is revolved, and hence is also proportional to the speed at which the front wheels revolve. 47. The Standard speedome- ter, which is shown in section in Fig. 20 (a) and in perspective in (6), belongs to the class of speedometers operated by centrifugal force. It <"*> has two weights a that are free to ^'°" ^ slide on the rods 6, which are hinged to the stem c. This stem has motmted on it two segments d whose teeth engage those of a rack e that is movable in a longitudinal direction. An arm / is clamped to the spindle of each segment, and the free end of each arm has hooked to it a coiled spring g. Each of the sliding weights a carries four Digitized by Google § 1 GASOLINE AUTOMOBILES 43 pins fe, two on each side of each segment d, between which fits loosely a cross-pin i carried by each segment. The flexible shaft driven by one of the front wheels rotates the stem c, and, tmder the influence of centrifugal force, the weights a slide out- wards; in doing so, the weights rotate the segments d, thereby putting tension on the springs g, until the centrifugal force of the weights equals the spring tension. The rotation of the segments moves the rack up or down; the movement of the rack is, by means of the pinion ; and the bevel gears k and /, transmitted to the pointer m moving over a scale graduated in miles per hour. The odometer part of the speedometer is purposely omitted in the sectional view in order to show the speed-indicating mechanism more clearly. A knob n, view (6), is used for resetting the trip odome- ter to zero. 48. The speed-indicat- ing mechanism of the Jones speedometer is shown in Fig. 21, all the odometer parts being removed for the sake of clearness and the case being partly broken . . Fig. 21 away. A rmg governor having the shape shown at a is employed. This governor is pivoted by the pin b to the steel shaft c, which is rotated by a flexible shaft d driven by one of the front wheels. The rota- tion of the shaft c causes centrifugal force in the ring a, making it tend to assimie a position at right angles to the shaft; this tendency is resisted by a coiled spring e that is compressed by the motion of the ring until the centrifugal force of the ring and the spring tension are equal. At very high speeds, an auxiliary spring/ comes into action. A brass tube, to which is attached the brass spool g, can slide along the shaft c, and it is connected to 'the ring a by means of a link h; consequently, as the ring moves toward a position at right angles to the Digitized by Google 44 GASOLINE AUTOMOBILES § 1 shaft, the spool g is moved to the left. In doing so, the spool pulls around a cam i that is pivoted by the shaft /, a pin k rigidly attached to the cam i engaging the slot of the spool. The face of the cam bears against a pin / carried by the link m, which is hinged to an ann fixed to a shaft carrying the pointer n that, in the assembled instrument, moves over the graduated scale, showing the speed. The cam pushes the link m to the left, thereby rota- ting the pointer n. A coiled spring o insures that the pin / is always in contact with the face of the cam t, its one end being attached to the shaft that carries the pointer. 49. The Stewart multipolar speedome- ter, a perspective view of one model of which, with enough of the casing and dial broken away to show the speed-indicatingmech- (^) anism, is presented in ^'^•^ Fig. 22 (a), belongs to the class of speedometers operating by magnetic induction. The rotor a is made of a non-ferrous metal and has inserted in it four permanent magnets 6. This rotor is mounted on Digitized by Google § 1 GASOLINE AUTOMOBILES 45 a pair of ball bearings and is revolved by the bevel pinion c on the solid driving shaft d that meshes with the internal gear e. The shaft d, in turn, is driven from one of the front wheels by a flexible shaft, not shown. The central stud around which the rotor revolves is recessed and has at the bottom of the recess a jeweled bearing for one end of the shaft /, the second bearing for this shaft being in the stationary plate g. A circular disk fe, made of an alloy having a low electrical resistance, is fastened to the shaft /; a pointer i is also attached to the same shaft. One end of a hair ^ring / is fastened to the shaft /, its other end being attached to the stationary plate g. It will be observed that there is no mechanical connection between the rotor and the rotatable disk h. In operation, the revolution of the rotor causes the disk h to revolve in the same direction, this tendency being resisted by the hair spring ;, and, consequently, the disk h turns imtil its tendency to revolve just balances the tension of the hair spring. The tendency of the disk ft, and hence of the pointer t, to revolve is proportional to the speed of the rotor; thus, for each change in the car speed, the disk h assimies a new position, thereby indicating the speed on the dial by means of the pointer moving with the disk. 50. Experience has demonstrated that, under great changes of temperature, the electric resistance of the disk pulled around by the magnets of magnetic speedometers is subject to change; under such conditions, therefore, a magnetic speedometer is liable to indicate wrong speed. To overcome this faxilt, many Stewart speedometers are fitted with a temperature-compen- sating device, which is shown in Fig. 22 (6), applied to the hair spring of a different model of instrument from that shown in (a) . The compensator consists chiefly of a laminated strip a of steel and brass that is coiled as shown, one end of it being anchored at 6, and the other end being free. The free end of the strip uncoils slightly when the temperattire rises, because the brass in it expands more than the steel; and it coils up more when the temperature drops, because the brass contracts more than the steel. The movement of the free end of the Digitized by Google 46 GASOLINE AUTOMOBILES § 1 strip a is transmitted to a sector c that meshes with a pinion, to which the one end of the hair spring d is attached. The uncoiling of the strip lengthens the hair spring on a hot day, and the coiling up of the spring shortens the hair spring on a cold day, thtis causing it to offer more resistance to the pull of the magnets of the rotor. Changes in the electrical resistance of the disk pulled around by the rotor magnets are thus compensated 1 for by increasing or decreasing the resist- ance of the spring op- _.^^ posing the pull of the rotor magnets. / 51. Practically all speedometers are driven in the manner indicated in Fig. 23 (a) . ^^ A large spur gear a is bolted to the hub of one front wheel and central with the hub; with it meshes a pinion b fastened to a shaft inside the tube c. This shaft, through a (b) series of four bevel ^'°-^ gears enclosed in the casing d drives another shaft in the tube e, to which the flexible shaft leading to the speedometer is attached. The casing d is made in two halves that can swivel on each other; conse- quently, as the lower part is held rigid with reference to the wheel, the upper part can swing in a horizontal plane. By this means the flexible shaft is not subjected to bending every time the front wheels are turned, and its Uf e is thus greatly increased. Digitized by Google § 1 GASOLINE AUTOMOBILES 47 The comhiiiation of the casing parts with its four bevel gears and its two soUd shafts forms what is variously known as a flexible-joint drive, a swiveUjoitU driven or a pivoi-joint drive. The internal construction of a swivel joint, as used in connec- tion with the Hoffecker speedometer, is shown in (6). The bolt a fonns the pivot on which the two parts of the casing can swivel; it has motmted on it loosely the double bevel gear 6, which transmits the motion of the lower shaft to the upper shaft. 52. The flexible shaft used & with speedometers consists of two members, namely, a protective flexible casing and a flexible driving member. The flexible casing may be metallic tubing, or it may be braided and water- proofed fabric over a flexible metallic core, inside of which is the flexible driving member. In Fig. 24 are shown short sections of three different types of flexible shafts in common use. In view (a) is presented the flexible shaft used with the Hoffecker speedometers. The ca- sing consists of a metallic core a coiled from flat stock; this core <'^> ^> ^^^ is covered with two layers b and c ^°* ^ of waterproofed flexible braided fabric. The flexible driving member d consists of seventeen strands of very fine piano wire that are woven together. In the flexible shaft used with the Warner speedometer, and shown in view (6), the flexible casing consists of a flexible steel core a made by coiling from two strips of flat stock; this core is slipped inside a r^ular flexible brass tube fc, such as is used for automobile horns. The brass tubing, in turn, is protected by Digitized by Google 48 GASOLINE AUTOMOBILES § 1 a casing c having the form of an ordinary helical spring. The flexible driving members consist of a series of cylindrical links d to which are hinged flat links e, pins being passed through holes/ that are somewhat larger than the pins. Owing to the shape of the slots in the links d, considerable motion in all directions is possible between all links. The Stewart speedometer uses the flexible shaft presented in view (c). The casing consists of the usual core a coiled from flat stock; this is kept in shape and protected by the flexible brass tube fc. The driving member consists of a series of like links c hooked together, the two hooks of each link being at right angles to each other. Digitized by Google GASOLINE AUTOMOBILES (PART 2) AUTOMOBILE RUNNING GEAR WHEELS AND AXLES WHEELS !• Types of Motor- Vehicle Wheels. — Most automobiles are eqtdpped with wooden wheels of the so-called artillery type, a form of wheel used on gun carriages and one capable of with- standing severe shocks imder heavy loads. Early types of automobiles were equipped with wire wheels; that is, wheels having wire spokes. Such wheels are again coming into use on accotmt of the progress made in wire-wheel construction. Wooden wheels of the artillery type are known as compression wheels, because the spokes in the bottom half of the wheel carry the weight and are therefore in compression. Wire wheels are known as suspension wheels, because the spokes supporting the hub are in tension, that is, drawn up tightly, and the load may be said to be suspended by these spokes. 2. Wooden Wheels. — Artillery wheels are usually con- structed with the spokes set in a single circle aroimd the hub, between the flanges of which they are securely clamped by means of bolts. As compared with wire wheels, this type of wheel is more easily cleaned, is more elastic, and is not sub- ject to deterioration on acdoimt of rusting. Ordinarily, the COPVm«HTBO BY INTBRNATIONAL TKXTBOOK COMPANY. ALL RIOMTS RnSIIVBO 222B— 5 Digitized by Google 50 GASOLINE AUTOMOBILES § 1 spokes lie in a plane perpendicular to the longitudinal center line of the hub, but in a few cases they are dished; that is, they are set inwards at the hub and are not perpendicular to the center line of the hub. The dished construction is claimed by some manufacturers to give the wheel greater strength to resist lateral or sidewise stresses, as when turning comers. In most automobiles equipped with wooden wheels, each front wheel Pig. 1 has ten spokes and each rear wheel, twelve; although, in some cases, both front and rear wheels are provided with twelve spokes each. 3. The construction of a typical automobile wheel is shown in Fig. 1, which illustrates the front and rear wheels used on the Packard car. Part of each wheel is cut away in order to show the arrangement of the pafts at the hub. Except for the different ntunber of spokes and the different requirements at the hubs, the construction of the two wheels is identical. As shown, they are fitted with demountable rims a, which can be taken off quickly by removing the nuts 6 and the cleats c. The front wheel, which is illustrated in view (a), contains ten spokes d set around the hub in a single circle and held in place by bolts e Digitized by Google S 1 GASOLINE AUTOMOBILES 61 that pass through the hub flanges. The felloe f and the spokes are bound in place by the steel rim g, which is pressed over the felloe. In view (6) is shown the rear wheel, which contains twelve spokes h arranged in a single circle, like the spokes in the front wheel. These spokes are held in place by bolts i that pass through the hub flanges and bolts / that are used for attaching the brake drum k. The bolts / pass through the brake drum Jfe, the hub flange /, and the spokes, thus tying, or binding, these Pig. 2 parts together. Part of the hole in the hub is squared in order that the wheel may be driven by the squared end of the axle shaft. The hub caps m and n are provided to keep dust and dirt out of the hubs and to give the hubs a finished appearance. 4. Fig. 2 illustrates both the construction and the arrange- ment of the spokes in the Schwarz patent wheel, which is used on a large number of automobiles. The mitered joints at the hub end of the spokes are made to overlap by using the mortise- and-tenon joint. When the spokes are assembled, the tenon a fits into the mortise 6, tenon c into mortise d, and the inner tenons a and e are overlapped by the outer tenons / and g. The spokes are thus so interlocked that they cannot work loose, and they support one another in a compact, true Digitized by Google 52 GASOLINE AUTOMOBILES § 1 assemblage. The spokes are put together under pressure with glue, and the appearance of the spokes at the hub when assembled is as shown at the right in Fig. 2. 5. Wire Wheels. — ^For automobile use wire wheels are constructed on practically the same principle as ordinary bicycle wheels. Usually, the spokes are arranged about the hub in two circles, one set of spokes being attached to the inner hub flange and the other set to the outer hub flange. All the spokes are tightened to exactly the same tension, so that they hold the hub in a central position and equalize the strain on the hub and the rim. The principal advantages Fig. 3 claimed for wire wheels over wooden wheels are that they are stronger and will withstand a greater driving stress in pro- portion to their weight. It is also claimed that wire wheels keep cooler than wooden wheels, on accotmt of their ability to radiate heat more readily, and hence the tires are not affected to so great an extent by the heat generated when rotating rapidly. 6. An example of an American-made wire wheel is the McCue wheel, one form of which is illustrated in Fig. 3 (a). This wheel, as shown, contains two rows of spokes, one row being attached to the inner part of the hub and the other row to the Digitized by Google § 1 GASOLINE AUTOMOBILES 53 outer part. There are forty-two spokes in the inner row and twenty-eight in the outer row, so that the hub is suspended at seventy points. Each spoke is fastened to the rim a by means of a nipple 6, into which the spoke is screwed. The spokes are in pairs; that is, two spokes are formed of one piece of wire, which is passed through two holes in the hub casing and attached at two different points on the rim. For example, the spokes c and d are formed of the same piece of wire, which extends from the rim through the hole e and is bent over on the inside of the hub casing g and brought out through the hole /, from which it extends to another point on the rim. The two spokes thus formed cross at an angle close to the hub, as shown. In the manufacture of the wheel, all the spokes are tightened to ex- actly the same tension. Fig. 3 (6) shows the inner hub that fits in- side the hub casing g. As will be observed, this inner hub is made for a rear wheel and carries the brake drum h. The inner ^'""'^ hub and the outer casing are made with a taper fit, the part i fitting into g and the long part ; fitting into k of the outer casing. The driving strain is taken by pins / that engage with the holes m in the outer casing. The wheel is held in place on the inner hub by means of a nut n that screws on the end of the hub and presses against the end of the outer casing, thus pre- venting the parts from separating. The nut n is screwed in place by means of a wrench o, which is provided with hooks p that engage with projections on the nut. One of these projections is shown at q and the other is covered by the safety latch r . The end of the outer casing of the wheel hub is shown in Fig. 4. The projection, or pin, that is covered by the safety Digitized by Google 64 GASOLINE AUTOMOBILES § 1 latch, shown in Fig. 3, fonns a pawl that extends through the nut and engages with the ratchet teeth 5, Fig. 4. This pin, or pawl, is fitted with a coil spring that pushes it out, disengaging it from the ratchet when the safety latch is moved to one side. When the wheel is to be taken off, the wrench o. Fig. 3, is placed on the nut and Jiumed until the hooks p engage the pins, or pro- jections, on the nut. This operation auto- matically pushes the safety latch r aside and allows the pawl and ratchet to become dis- engaged. The nut can then be unscrewed. In putting on the wheel, the nut n is first screwed on the hub and then, when the wrench is removed, the safety ratchet snaps back into place, forcing the pawl into the teeth on the ratchet s, Fig. 4, and locking the nut and, consequently, the wheel in position. It is to be noted that the wire wheel just de- scribed is a detachable ^°* ^ wire wheel; that is, it can be readily removed. Generally, where these wheels are used, a spare wheel is carried for use in case of tire trouble. Digitized by Google S 1 GASOLINE AUTOMOBILES 55 7. Another form of McCue wheel is provided with three rows of spokes, as is illustrated in Fig. 5, which is a sectional view of a rear wheel, showing the inside construction of the rear hub, as well as the arrangement of the spokes. The axle shaft a, to which the wheel is fitted, turns freely in the stationary tube b of the axle housing. The ball bearing c is moimted on the outside of the tube 6; the inner wheel hub d, which is keyed to the axle shaft, turns on this bearing. The hub casing e fits over the inner hub d and is held in place by the cap /, the driving stress being transmitted through the pins g. The brake drums h and i are so bolted to the inner hub that they rotate with it. The three rows of spokes are shown at /, ife, and /, the rows ; and k containing the same number of spokes. The spokes of this wheel are made separately, instead of in pairs, as in the whefel illustrated in Figs. 3 and 4, each spoke being attached to the wheel hub by having the end upset and swaged, as shown at w. The triple-spoke wire wheel is used where wire wheels are fitted to an automobile that had previously been equipped with wooden wheels, the third row being added to take up the extra strain occasioned by setting the rim in for the purpose of keeping the wheel tread the same. On accoimt of the con- struction of the rear axle used with wooden wheels, the brake drums must be kept the same distance apart when wire wheels are substituted; hence, it is necessary to set the wheel rim in farther toward the automobile body, in relation to the hub, than when the axle is built specially for wire wheels. The extra strain set up by thus constructing the wheel is taken by the row of spokes k. 8. Spring Wheels. — ^To obviate the use of pneumatic tires, the maintenance and first costs of which are high, and at the same time to secure the easy riding qualities of the pnetmiatic tire, many inventors have given a great deal of thought to the problem of producing commercially feasible elastic, or spring, wheels. Numberless designs have been produced, but spring wheels have not become popular. . Digitized by Google 66 GASOLINE AUTOMOBILES § 1 FRONT AXLES 9. The front axle of an automobile is made up of four parts; namely, a bar carrying the spring seats upon which the springs supporting the front part of the automobile rest, two steering knuckles carrying the spindles on which the wheels turn, and a cross-rod extending from one steering knuckle to the other and by means of which the knuckles are tied together Pig. 6 so as to move in imison when the wheels are swiveled in steer- ing. The location of these four parts is shown clearly in Fig. 6, which is a front view of one model of the chassis of the Winton automobile. The main bar of the axle is shown at a, and at b and c are located the spring seats upon which the front springs e and / are carried. The steering knuckles g and h are pivoted at the ends of the axle bar and are connected by the cross-rod i, which, in this automobile, is located in front of the front axle. Digitized by Google § 1 GASOLINE AUTOMOBILES 57 More frequently, the rod i is located back of the axle, but in every instance it performs the same service; that is, it forms a connecting link between the steering knuckles. On the majority of automobiles, the front axle bar is made of a forged-steel I beam, as shown in Fig. 6. In a few cases, however, the axle is made of a steel tube, in still other instances the bar is of channel cross-section, and on at least one of the smaller cars a wooden axle has been used. Front axles may, then, be classified broadly as solid front axles, of which there are a ntmiber of types, and tubtUar front axles. 10. Solid Front Axles. — Several types of solid front axles having an I-beam cross-section are illustrated in Fig. 7, which shows a top and a side view of each. In (a) is shown the front axle of the Studebaker "20" automobile. The axle bar a of this axle is made of a sted I beam, which is dropped at the center to make it more elastic. This bar carries the spring seats 6, upon which the front springs rest, and the spring clips d, which hold the springs in place. The steering knuckles e are pivoted in the yoked ends of the axle by the pins c, and they carry the spindles /'upon which the front wheels rotate. The knuckles are connected by the cross-rod A, which is attached to the arms g by means of yoked ends. The rod h and the steering knuckles are rocked to and fro when steering the auto- mobile, by a rod i that is connected at its free end to tfie steer- ing gear. The steering knuckles used on this axle are known as the EUiott type. In this type, the knuckles fit between jaws formed at the ends of the axle bar. Another front axle of I-beam cross-section, but one that makes use of steering knuckles of the reversed Elliott type, is the McCue axle shown in (6). The different parts of this axle perform the same functions as the corresponding parts in the axle shown in (a), the steering knuckles in this case being rotated by an arm a that is connected to the steering gear by means of a nxi, not shown. It will be noted that in this case the steer- ing knuckles have jaws fitting over stub ends of the axle bar. The Winton axle, shown in (c), also makes use of an I-beam cross-bar, but it uses \h&Lemoine type of steering knuckle. Digitized by Google Q; nfiiiiniiiiii'aiimHiiiiiiij QaOiE Digitized by Google § 1 GASOLINE AUTOMOBILES 59 In this case, the steering knuckles are rotated by means of an arm a that is connected to the steering gear by a rod, as previously ex- plained in connection with the McCue axle. In the Lemoine steer- ing knuckle, no jaws are used; the knuckle has a stub b that fits into a corresponding hole in a boss c at each end of the axle bar. The "32" Hupmobile car uses a reversed Lemoine steering knuckle, which means that the spindle upon which the wheel turns is at the top of the axle bar instead of below it. 11. In Fig. 8 is shpwn a part sectional and part front view of a ^ pressed-steel front axle, made in i the form of a channel, as used in some S. G. V. automobiles. The main part of the axle a is fitted with two end-pieces b that carry the steering knuckles c. The steering knuckles, which are of the reversed Elliott type, are tied together by the rod d, so that they receive the same movement when operated by the ann e. The wheel hubs are shown in place at / and g, and the spring clips that hold the springs on their seats, at h and i, 12. Tubular Front Axles. ■ An example of a tubular front axle is the Franklin axle, two views of which are shown in Fig. 9. The main axle bar is a steel tube a, which is brazed to the steering Digitized by Google 60 Digitized by VjOOQ IC § 1 GASOLINE AUTOMOBILES 61 knuckles b. The axle is dropped, or bent downwards, at the center to increase its elasticity. The springs are carried beneath the axle tube by spring dips c that are bolted to the supports d. The steering knuckles are tied together by the rod e^ so that they move in unison, and they are operated from the steering gear by means of the arm /. One road wheel g is shown in part section in place on the axle, and it serves to illustrate the Pig. 10 relative positions of the wheel and the steering knuckles. When springs are placed beneath the axle, they are said to be underslung. 13. Steering Knuckles. — In four-wheeled horse-drawn vehicles, the spindles upon which the wheels revolve form an integral part of the front axle, and steering is accomplished by turning the entire axle about its center. In automobiles, however, this construction is imdesirable because of the dif- Digitized by Google 62 GASOLINE AUTOMOBILES § 1 ficulty that wotild be incurred in steering by hand at high speeds, as weU as the lack of strength that would result. In order that the front axle bar of an automobile may be attached rigidly to the springs, and to obtain easy steering by turning the wheels through only a small radius, steering knuckles are provided. Steering knuckles are devices pivoted at the ends of the front axle of an automobile for the purpose of supporting the front wheels and allowing them to be turned without moving the axle bar. 14. A common form of the Elliott steering knuckle is shown in place on the axle in Fig. 10, which is a view of the right-hand front wheel and steering connections on the Abbott- PlG. 11 Detroit automobile, looking from the rear of the car toward the front. The steering knuckle a is pivoted in the yoke b of the axle bar, and it is operated from the hand steering wheel through the arm c, the reach rod d, and the steering-gear crank- • arm c clamped to the steering gear-shaft /. The spindle g upon which the road wheel h revolves is an integral part of the knuckle. This steering knuckle is connected to the knuckle on the left side of the car by means of the distance rod i, which is attached to the arm /. When the steering wheel is turned. Digitized by Google § 1 GASOLINE AUTOMOBILES 63 the reach rod d is moved forwards or backwards by the arm e, so that the kaudde, and, consequently, the road wheel, is turned to the right or the left by the arm c. The other front wheel is turned at the same time and in the same direction by means of the distance rod i. The steering knuckle on the left side of the automobile is exactly the same as that shown in Fig. 10, except that the arm c is omitted. 15. In Fig. 11 is shown the left-hand steering knuckle used on the Chadwick car. In this automobile, the steering gear is located on the right-hand side, so that no reach rod arm is necessary on this knuckle. The steering knuckle a has a separable ann b con- nected to the distance rod c by means of a ball-and-socket joint at d. The steering- knuckle pivot pin e passes through the yoke/ and is prevented from coming out by a nut and a cotter pin on the lower end. This knuckle is also of the EUiott type, the yoke being an in- t^;ral part of the axle bar. A cross-sectional view p^^, ^^ of the Chadwick steer- ing knuckle is illustrated in Fig. 12, which is lettered the same as Fig. 11, wherever possible, so that the preceding explanation may be applied to both illustrations. In Fig. 12, the wheel hub g is shown in place on the spindle and the distance rod is omitted in order to show the other parts more clearly. 16. Fig. 13 shows a cross-sectional view of the steering knuckle used on the Steams automobile. It, too, is of the Elliott typOf and differs principally from the Chadwick knuckle in that the pivot pin bearings, or bushings, h and i are mounted Digitized by Google 64 GASOLINE AUTOMOBILES § 1 in the yoke ends instead of in the knuckle head, as shown in Fig. 12|, and a plain thrust bearing /, instead of a ball thrust bearing is used to support the load. In the Steams steering knuckle, the wheel hub is mounted on roller bearings k, while in the Chadwick it is mounted on ball bearings. 17. An example of the reversed Elliott steering knuckle is that used on the Fierce- Arrow automobile. A perspective view of this '^" ^^ knuckle is shown in Fig. 14, and a cross-sectional view, in Fig. 15. On referring to these illustrations, which are lettered alike, it will be seen that the spindle a and the yoke b form a one-piece steel forging, and that this forging carries the wheel hub c on the bearings d and e. Pig. 14 The enlarged portion g of the axle bar/ is pivoted in the yoke by the pin h. It is to be noted that the steering-knuckle bearings, or bushings, i and / are mounted in the yoke and that the yoke Digitized by Google § 1 GASOLINE AUTOMOBILES 66 turns on the pin A, which remains stationary with respect to the axle bar. This fonn of construction is the rule in the reversed £lliott type of steering knuckle, although in the ElUott type, Fig. 15 as jtist explained, the bearing may be in the knuckle, or head, as shown in Fig. 12, or it may be in the yoke, as in Fig. 13. Figs. 14 and 15 show the right-hand steering knuckle viewed from the front of the automobile. The knuckle is operated from the reach rod by means of the remova- ble armfe and is tied to the left-hand knuckle by means of the dis- tance rod /, which is joined to the arm m by the ball-and-socket joint n. 18« A Lemoine steering knuckle, ^^ ^^ as used on the Win- ton automobile, is shown partly in section in Fig. 16; an outside view of this tjrpe of knuckle, on the front axle, is shown in Fig. 7 (c). As will be seen on referring to Fig. 16, no yoke is employed in this knuckle, but the spindle a and the pivot pin b 222B— 6 Digitized by Google 66 GASOLINE AUTOMOBILES § 1 are integral, and the pin rotates in bearings c and d in the axle head e. 19. Steering Connections. — Fig. 17 illustrates the com- plete steering system of the Pierce-Arrow automobile. This system is presented to show the way in which many steering systems are arranged and how turning the steering wheel a to the right or the left causes a corresponding movement of the front wheels. When the wheel a is rotated, a worm at the lower end of the steering coltmin b causes the segment of a worm-wheel with which it meshes to turn on its axle, thereby causing the arm c to move backwards or forwards, as the case Fig. 17 / may be. The motion of the reach rod d is transmitted to the steering arm e of the right-hand steering knuckle /, and from the latter, through the knuckle arm g and the distance rod A, to the arm i of the left-hand steering knuckle ;. The two steering knuckles are thus made to move in imison to the right or the left in response to a corresponding movement of the steering wheel. When the wheel is ttimed to the right, the reach rod d moves forwards, causing the front wheels to be swimg around so that the car travels toward the right. Rota- ting the wheel in the opposite direction causes the reach rod d to be drawn back, so as to turn the front wheels toward the left. Digitized by Google § 1 GASOLINE AUTOMOBILES 67 It is to be noted that on this automobile the steering wheel a is located on the right-hand side, so that the reach rod d and the arm e are also on the right-hand side. However, many Pig. 18 manuf acturers now place the steering colimm on the left-hand side of the automobile, in which case the distance rod and the steering arm are also placed on that side. Generally, the dis- tance rod that connects the steering-knuckle arms is located Digitized by Google 68 GASOLINE AUTOMOBILES $ 1 behind the front axle, as is indicated in Fig. 17, the object being to protect it from damage that might result from obstructions in the road; nevertheless, it is sometimes placed in front of the axle, as is shown in Fig. 6. 20. On some automobiles, the reach rod extends across the chassis, in which case it connects the lower end of the steer- ing colimin with the steering knuckle on the opposite side of the automobile. An example of this kind of construction is illustrated in Fig. 18, which shows a top view of the forward part of the chassis of one model of the Overland car. A worm and a worm-wheel are located in the casing h at the lower end of the steering coltunn a, jtist as is explained in connection with Fig. 17; but they are so arranged that when the steering wheel b is turned to the tight or the left the reach-rod arm is rotated backwards or forwards crosswise of the chassis instead of lengthwise. A movement of this arm causes a correspond- ing movement of the reach rod c, and this, in turn, causes the desired rotation of the road wheels d through the steering- knuckle arms e and / and the distance rod g. When the steering wheel is located on the left-hand side of the automobile and a reach rod running cross wise of the frame is employed, the reach rod extends to the steering knuckle on the right-hand side. 21. Mounting Front Wheels. — ^In order that an auto- mobile may be steered easily by hand, it is desirable that the front wheels turn as nearly as possible on an exact pivot; that is, that the pivot pin be as nearly as possible in line with the point where the wheel touches the ground. This object is accomplished in some cases by having the steering knuckles constructed so that, while the pivot pins are vertical, the wheels are inclined slightly and are closer together at the bottom than at the top. In other words, a line x x, Fig. 9, drawn through the center of one of the pivot pins will be nearer the center line ^^ :v of the wheel at the point where it touches the ground than at the hub. By thus bringing the bottom of the wheel as near as possible to the center line of the pivot pin, the ease with which the wheels may be turned in steering is increased. Digitized by Google § 1 GASOLINE AUTOMOBILES 69 The same object may be accomplished by keeping the wheel vertical and inclining the steering-knuckle pin, or by inclin- ing both the wheel and the pivot pin. The method last named is illtistrated in Fig. 12, which shows a steering knuckle so designed that both the wheel and the pin are set at an angle. 22. Ease of steering is accomplished in some automobiles by making the hub of the front wheel hollow and placing the st.eering knuckle in its center. In this way, the center of the steering-knudde pivot pin is brought into exact line with the center plane of the wheel, and maximum ease of steering is produced because the wheel is turned on an exact pivot. An Fig. 19 example of this form of steering knuckle and front axle is pre- sented in Pig. 19, which shows a front view of the six-cylinder Mannon car. The axle yoke a extends into the hub 6, so that the center line of the steering knuckle c coincides with the center plane of the wheel. 23. Caster Steering. — By means of certain particular settings of the steering-knudde pivot pins, it is possible to make the front wheels of an automobile keep automatically in line with the rear wheels while the car is in motion, thus tending to ntiake it go straight ahead. The principle involved is either identical with that used in casters placed imder Digitized by Google 70 GASOLINE AUTOMOBILES 51 •■-^■"^^-~- .. r-l- Co q If Lb3^ fumittire or a modification of it; for this reason, front axles constructed on the same principle are known as caster steering axles. This effect is accomplished in three ways, as is illus- trated in Fig. 20. In the first method, which is shown in view (a), the steering knuckle a is slanted so that the line A 5, which passes through the center of the pivot pin, meets the ground at a point 6, which is a short distance ahead of the point c where the tire touches the ground. It is assumed that the front of the automobile points in the direction of the arrow x. Slanting the steering knuckles in the manner first explained gives the same steering effectas slantingthe front fork of a bicycle; that is, the weight of the automo- bile tends to keep the front wheels in line with the rear wheels and to make the car go straight ahead. It is to be noted that in this case the spring seatrf is not set square with the axle but is tilted slightly to allow the spring e to be mounted horizontally. The second method of obtaining the caster effect Digitized by Google § 1 GASOLINE AUTOMOBILES 71 is shown in view (6). This method is exactly like that illus- trated in view (a), except that the spring seat d is set square with the pivot pin, so that both the spring and the pivot pin are tilted in order to slant the steering knuckle. In the third method of obtaining the caster steering effect, use is made of the identical principle of the ordinary caster that is used on furniture. The application of this principle to a steering knuckle, as carried out in the B. and L. caster front axle, is shown in (c), which presents a top view and a rear view. The pivot pin a is set in front of the center line A B of the axle and inside of the wheel hub b, which is made hollow. By this arrangement, the center line of the pivot pin lies in the center of the wheel, but when extended it meets the ground at a point some distance ahead of the point where the tire touches the ground. The wheel, then, has the effect of trail- ing behind the pivot pin, just as the ordinary caster trails behind its pivot, or bearing, and tends to keep the automobile moving in a straight line. RBAB AXLES AND H0USINO8 24. T^pes of Rear Axles. — ^Rear axles are of two gen- eral types, namely, live rear axles and dead rear axles, depend- ing on their construction. A live rear axle is one that rotates or has a rotating part. It not only carries a part of the weight of the car and the occu- pants, but also serves to drive the rear wheels and thus propel the vehicle. A dead, rear axle has no rotating parts; the wheels are driven by chains from a countershaft and they turn on spin- dles on the ends of the axle. A dead rear axle serves only to carry its proportionate part of the weight of the car and its load, and fakes no part in driving the wheds. 25. In the majority of American-made automobiles use is made at present of the live rear axle; the dead axle is employed in only a limited number. The live axle is made up of three principal parts, namely, a two-piece driving axle shaft, a differential, and a housing that encloses the axle shaft and Digitized by Google 72 GASOLINE AUTOMOBILES § 1 the differential. That part of the housing which surrounds the axle shaft is sometimes called the axle tube, and to it are pinned and brazed or otherwise fastened the spring seats, or blocks, to which the rear springs are fastened by means of spring clips. Each half of the axle shaft is attached at its inner end to the differential, which is located in the middle of the axle, and at its outer end to one of the road wheels, which it drives. The axle shaft is driven through the differential, which consists of a set of gears so arranged that while both parts of the shaft receive power, one part may turn at a higher rate of speed than the other and thus allow the automobile to go around a comer without causing one of the wheels to slide. Usually, the differential is driven from the engine by means of a shaft and bevel gears, or by means of a shaft driving a worm that meshes with a worm-wheel, although in a few cases it has been driven by a chain and sprockets. Live rear axles are divided into a number of types, or classes, depending on the arrangement of the axle bearings and on the method of connecting the road wheels to the axle shaft. These classes are plain live rear axles, semifloaiing rear axles, three- quarter-floating rear axles, and full-floating rear axles, 26. Plain Live Rear Axles. — ^The first rear axle in gen- eral use was of the plain live-axle type and was driven by a chain and sprocket wheels. In this type, each part of the two-piece axle shaft is supported directly by two bearings, which are motmted between the axle shaft and the axle tube. Besides driving the rear wheels, the rotating axle shaft must carry the weight that comes on the rear axle. Chain-driven axles of this type are obsolete, practically all the plain live rear axles now employed being driven by a propeller shaft. 27. An example of a shaft-driven plain live rear axle is presented in Fig. 21, which illustrates the axle used on the Ford, model T, automobile, (a) being an external view and (fc) a cross-sectional view; the two views are lettered the same, as far as possible, but are drawn to different scales. The cross-sectional view (fc) shows part of the axle housing a cut away, exposing to view the axle shaft 6, V and the differential c. Digitized by Google 73 Digitized by Google [LES § 1 3 b and b\ which are ear d being keyed to )'. Each part of the / and g. The road axle shaft, which is e is driven from the h drives the differen- road wheels, through ing gear /. d g is shown in detail s d made up of bars lical spring is made. f two rings a, which 5 b and contain pro- sing e is placed inside the Ford differential t^ — , „ „ w« 1 at a higher rate of, speed than the other. In this illustration, part of the housing a is cut away so as to show the gears, and the different parts are lettered the same as in Fig. 21. On referring to Fig. 23, it will be seen that the differential consists, in part, of the inner housing, or casing, k, to which is fastened the bevel dri\dng gear ;. Three small bevel pinions /, which are fitted to the Digitized by Google § 1 GASOLINE AUTOMOBILES 75 inner housing k and are free to ttim on their own axes, mesh with the gears d and e, which are keyed to the halves of the axle shaft. When the automobile is being propelled by the engine, the pinion i on the propeller shaft turns the inner hous- ing k by means of the bevel driving gear /. The housing k carries the small pinions / bodily around with it, and these pinions, in turn, rotate the gears d and e and thus cause the axle shaft and the rear wheels to turn. When the automobile is traveling straight ahead, the gears d and e rotate at the same speed because the road wheels rotate at the same speed; hence, Pig. 23 the pinions / do not turn on their own axes, but remain sta- tionary with respect to the housing k^ simply forming a con- nection between the housing and the gears d and e. However, when the automobile turns a comer, or goes around a curve, the rotation of one rear wheel is resisted more than that of the other, or, in other words, the inner rear wheel is held back and does not travel so fast as the outer one, so that the gears d and e must be allowed to turn at different speeds in order that one of the road wheels will not skid. When this condition exists, the pinions /, besides being carried around bodily by the housing k, turn on their own axes, and thus permit one of the gears d and e to rotate more slowly than the other and allow the road wheels to travel at different rates of speed and ' at the same time receive power from the engine. Digitized by Google 76 GASOLINE AUTOMOBILES § 1 The meshing of the bevel driving pinion i, Fig. 23, with the driving bevel gear / tends to thrust the whole differential- gear assembly sidewise; this tendency is resisted, however, by a special thrust bearing, which must be provided in all rear axles employing the bevel-gear drive. The differential just explained is known as a bevel-gear dif- feretUial, because the gears inside of the inner housing are bevel gears. On some automobiles a spur-gear differential is used. This kind of differential is constructed on the same principle as the bevel-gear differential, except that spur gears instead of bevel gears are employed inside the housing. 29. Semifloating Rear Axles. — ^The semifloating rear axle differs from the plain live rear axle in that the inner ends Fig. 24 of the axle shaft are supported, that is, have a bearing, in the differential housing instead of in the axle housing. The axle shaft, at its outer ends, just as in the plain live axle, rotates directly in bearings fitted to the axle tube. The inner housing of the differential rotates on bearings that are motinted between hubs on each side of the differential housing and the outer or stationary axle housing. The axle shaft passes freely through the hubs of the housing, so that it is relieved of the weight of the differential, and its inner ends are subject chiefly to the driving stress, the axle tube taking part of the weight of the Digitized by Google § 1 GASOLINE AUTOMOBILES 77 autxttnobile. In this type of axle, the wheels are keyed or other wise fastened to the outer ends of the axle shaft, just as in the plain live rear axle. Owing to the fact that the inner ends of the axle shaft do not support the differential assembly, and hence are not sub- ject to as severe bending stresses as those of the plain axle, these ends of the axle are said to float, whence the name semi- floating axle is derived. 30. An example of a semifloating rear axle is that used on the Pierce-Arrow automobile. This axle is illustrated in Pigs. 24 and 25. Pig. 24, which is a perspective view, shows the rear- axle construction and part of the automobile frame, and Pig. 25, which is a cross-sectional view of the same axle, shows the axle housing and differential cut in half, thus exposing to view the axle shaft a. The same parts in both illustrations are lettered alike as far as possible. In Pig. 24, the end of the axle shaft upon which the road wheel is fitted is shown at a; the axle tube b surrounds the shaft and carries the rear springs, which are of the three-quarter-elliptic type. The outer differential housing is shown at c. The brake dnun d is bolted to the wheel and, when assembled, it is located between the brake bands e and /, which may be applied and released by the driver either by means of a hand lever or by a pedal. 31. On referring to Pig. 25, which shows the inside con- struction of the axle, it will be seen that the axle shaft a is sup- ported at its outer ends by the bearings g mounted inside of the axle tube 6, and at the differential by the hubs of the gears h and h\ into which its inner ends extend and are keyed. The inner differential housing i is carried by the bearings /, which are mounted in the outer housing c. The thrust bearing k is supported against a shoulder in the housing c and prevents endwise motion of the housing i. The different forms of bearings used in this axle are illus- trated in Pig. 26. At (a) is shown the bearing used for sup- porting the outer ends of the axle shaft; this bearing is marked with the lett^- g in Pig. 25. It is known as a conical-roller bearing, and by means of the rollers, which are held between Digitized by Google 78 Digitized by VjOOQIC § 1 GASOLINE AUTOMOBILES 79 tapered casings, it prevents the shaft from moving endwise. The outer casing is not shown in this view, in order to more clearly show the rollers. At (b) is shown an annular ball bearing of the type used to support the inner diJBferential housing, as shown at /, Pig. 26. This bearing consists of two rings a and fe, between which hardened-steel balls c rotate. The balls are separated by means of cages d. A ball-thrust bearing like that used at i, Fig. 25, is shown in Fig. 26 (c). Pic. 28 It is made up of grooved races a and fc, between which the balls c rotate. This bearing is mounted in the axle by placing the ring a against the inner differential housing and the ring d against the stationary housing, in which position it prevents endwise motion of the differential. The differential-gear assembly t, Fig. 26, is driven by means of the large bevel gear I and the bevel driving pinion m. This differential is of the spur-gear type, being composed of spur gears so arranged as to allow one of the road wheels to turn at a higher rate of speed than the other, as, for instance, in going around a curve, with both wheds receiving power from the propeller shaft and engine. At n are shown the wheel hubs together with a part of the spokes o. In all bevel-gear-drive rear axles, a thrust in a forward direc- tion is exerted on the shaft that carries the bevel driving pinion. In the rear axle shown in Fig. 25 this thrust is taken care of by the annular ball bearing p\ in other rear axles, it is taken care Digitized by Google 80 GASOLINE AUTOMOBILES § 1 of by the use of conical roller 'bearings; and in still others, a separate thrust bearing is fitted to the bevel-pinion driving shaft. 32. Three-Quarter-Floatiiig Rear Axles. — In what is known as the three-quarter-floating rear axles, the bearings at the outer ends are so mounted outside of the axle tube that the wheels turn on them and the weight of the automobile and occupants is carried by the axle tube, or housing. The axle shaft is rigidly attached to the wheels and helps to keep them in the correct position; but outside of this, broadly speak- ing, the only stress that comes on it is the driving stress. In this axle, the driving shaft does not come directly in contact with any bearing, but is supported at the inner ends by the differential and at the wheel ends by the wheels, which run on the axle tube. The construction at the differential is exactly like that of the semifloating axle. 33. A three-quarter-floating rear axle, such as is used on the Overland car, is illustrated partly in section and partly in full view, in Fig. 27. The left half of this illustration shows that part of the ^e assembly cut in half, exposing to view the axle shaft and bearings, while the right half shows a top external view of the other part of the axle. At a is shown one-half of the axle shaft, which extends into the differential b at the inner end, and to which the rear-wheel hub c is keyed at the outer end. The differential is supported by roller bearings of the coiled roller type, one of which is shown at d, and the wheds run on the same type of bearings, which are mounted outside of the axle tube, as at e. The entire weight of the load is carried by the axle tube /, the shaft a taking the driving stress and helping to keep the wheels in a vertical position. The differential is prevented from being forced endwise by a ball-thrust bearing on each side. One of these bearings is shown at g, where it fits between the outer differential housing h and the thrust collar i. The axle is strengthened by means of a truss rod /, which may be adjusted by the turn- buckle k. The bolts / are used for fastening the transmission Digitized by Google § 1 GASOLINE AUTOMOBILES 81 casing, which is not shown, to the outer diflEerential housing, and the levers m and n are used for applying the brakes through the rods o and the tubes p. The grease retainer q isintheformofaring; it prevents the oil and grease from escaping from the diJBferential, being held in place by the spring r. 34. In the Over- land axle, the shaft a may be removed by loosening the screws of the collar i and withdrawing the shaft through the collar. The differential may be removed by with- drawing the halves of the ^e shaft and then removing the bearing caps s, after which it may be lifted out bodily. Of course, before removing the differential, the out- side cover-plate, which is not shown in the illustration but which fits on the bearing surface /, must be taken off. 222B— 7 Digitized by Google 82 GASOLINE AUTOMOBILES § 1 35. Full-Floating Rear Axles. — ^The only difference between a full-floating rear axle and a three-qiiarter-floating axle is that in the f onner the rear wheels are not rigidly attached to the axle shaft as in the latter, but are driven from it by means of a positive, or dog, clutch, or its equivalent. Two bearings are required at the outer end to support the wheel in an erect position. In this type of axle, the entire load is carried by the axle tube, or housing, while the axle shaft simply transmits the turning power from the differential to the wheels. The construction at the differential is exactly the same as in the three-quarter-floating axle or in the semifloating axle. 36. A typical full-floating rear axle, such as is used on the Stoddard-Dayton car, is shown in Fig. 28. The left half of the axle and the differential are shown in horizontal section; that is, they are considered as being cut in half horizontally, exposing to view the inside construction. The right half of the illustration is, in part, an external view of that part of the axle, looked at from the top. On referring to the sectional view, it will be seen that the axle shaft a extends from the differential gear 6, in which it fits, through the axle tube c, without coming in contact with any bearings, to the dog d, by means of which it is connected to the wheel hub e. The dog d has cut aroimd its circum- ference square teeth that mesh with square teeth cut into the face of the wheel hub, thus insuring a positive drive. The differential is carried on the conical roller bearings / and g, which prevent it from moving endwise, and each wheel runs on two annular ball bearings, as h and i, which are mounted outside of the axle tube and support the wheel in an erect position. The differential is of the bevel-gear type and is driven from the propeller shaft by the pinion / and a large bevel gear k. The brakes I and m are operated through the rod n and the tube o. As shown in the right half of the illustration, the spring seats p are carried by the axle tube c, which takes the entire load brought to bear on the rear axle. The propeller shaft q is encased by a torsion tube r, which helps to overcome the Digitized by Google 83 Digitized by VjOOQ IC 84 GASOLINE AUTOMOBILES § 1 tendency of the axle tube to turn. Oil and grease are pre- vented from escaping from the differential by the grease rings s. 37. Fig. 29 illustrates a Timken-Detroit full-floating rear Digitized by Google S 1 GASOLINE AUTOMOBILES 85 splines, or keys, that form an integral part of the axle shaft, and that engage slots in the wheel hub. The main axle housing/ is made of pressed steel and contains two inner reinforcing sleeves, or tubes, one on each side; each of these helps to carry the wheel bearings at its outer end. These inner sleeves extend in beyond the spring seats g, upon which the weight of the car rests. The inner ends of the axle shaft are shown at A, view (6) . When assembled, the differential housing i is bolted to the axle housing at /, so that the differential gears fit inside of the axle housing and the ends of the axle shafts extend into them from each side. The cover-plate k is bolted on the rear of the axle, as shown in (a). The differential gears are operated through the large bevel driving gear /, which is driven from the pinion Fig. 30 shaft m by means of a pinion enclosed in the differential hous- ing i. The truss rod n, located on the tmder part of the axle, serves to strengthen it, and the rods and levers on the front of the axle tube are for actuating the brakes, which are located at d and o. There are two sets of brakes, the one set being internal expanding brakes, while the other set, shown at d and o, are external contracting brakes. In operation, the outer differential housing is partly filled with oil, as shown at a, Pig. 30, where part of the axle housing is cut away in order to show the reinforcing sleeve fe, which extends inwards as far as shown. There is thus formed on each side of the axle, between the inside of the axle housing and the outside of each reinforcing sleeve, an oil pocket that catches oil thrown sidewise whenever the car is turning a Digitized by Google 86 GASOLINE AUTOMOBILES $ 1 corner; oil in large quantities is thereby prevented from work- ing along the axle shaft into the wheel hubs and thence into the brakes, where it would ereatlv reduce their efficiency. ead again, oil in the er differential housing. LKles. — ^All the rear fm the propeller shaft f the shaft and a large rential. Another form of drive that is used to some ejctent is the worm-gear drive, in which the axle shaft is driven by means of a worm on the end of the pro- peller shaft, and a worm-wheel on the differential. The worm meshes with the worm-wheel and turns the differential, just as the bevel pinion and gear do in the more ordinary form of axle. The d on any type of rear rive. ^1 is shown in Fig. 31, nplete differential-gear assembly ot a imucen-uavia tJrown rear axle removed from the axle housing. The worm a is integral with the shaft 6, and its teeth mesh with the teeth on the wheel c. The teeth on the wheel are made concave, as shown, so that they make contact over their entire width with the teeth on the worm. In the example illustrated, the worm is located on top of the wheel, but worm-drive rear axles are also built with the worm Digitized by Google Digitized by Google 88 GASOLINE AUTOMOBILES § 1 underneath. With the type of construction last named, the worm may run in a bath of oil. In the illustration, one part of the diflEerential housing is shown at d; a hub formed thereon carries the roller bearing e. Lxle is illustrated in Pig. 32, rt sectional view of the axle Jail Bearing Company. In 5 top, a part of the housing loved in order to show the the wheel-hub; in view (6), the outside of the axle is seen from the front end of the automobile. The axle is of the full floating type and in all respects, except the method of driving, is similar to the full-floating rear axles pre- viously described; there- fore, only the drive mecha- nism proper will be dealt with here. As far as pos- iews are lettered the same, ial a is enclosed in the outer [so encloses the axle shaft c. is bolted a worm-wheel e, ■m located beneath the axle le worm is integral with the le teeth on the worm-wheel, Irives the wheel e, and con- 5s. The shaft g is connected e is installed in the car. :he worm-wheel ^, together oved from the axle. These 5 bolts h, Fig. 32, and loosen- t secure the worm-wheel to town at / in Pig. 33, and the Digitized by Google S 1 GASOLINE AUTOMOBILES 89 end g of the shaft that carries the worm is seen protruding from the housing /. The end of the axle shaft to which the dif- ferential gears are fitted .extends into the casing at i, and a torsion rod can be attached by means of the socket /. The entire axle can be readily disassembled by simply pulling out the halves of the axle shaft and lifting out the worm-wheel and diSerential. 41. Rear- Axle Housings. — ^A rear-axle housing consists, in part, of an enlarged portion, in the middle of the axle, that encloses the differential gears, and, in part, of two axle tubes that surround the two halves of the axle shaft. The enlarged Pig. 34 part, or differential housing, is sometimes called the bridge, and the axle tubes are sometimes known as the bridge tubes. In some rear axles, the outer differential housing and the axle tubes are separate pieces, the differential housing being either made in two halves or provided with a large opening to permit insertion, inspection, and removal of the differential-gear assem- bly. The outer differential housings are made of cast steel, cast bronze, cast aluminimi, malleable iron, pressed steel, or drop forgings, and the tubes are usually made of drawn steel, although they are sometimes cast. The tubes are fitted to the outer differential housing in a variety of ways, In some cases. Digitized by Google 90 GASOLINE AUTOMOBILES § 1 they are forced into the hubs of the housing and riveted, some- times they are bolted to the housing, and in still other cases they are brazed. The rear-axle housing c shown in Figs. 24 and 25, is made up of two halves bolted together, the halves of the axle tube b being forced into the hubs of the housing and riveted. In the axle shown in Pig. 27, the tubes are fitted to the outer differ- ential housing in the same manner, but, instead of being divided into halves, this housing is provided with a large opening on top for inserting or removing the differential. This opening is ordinarily closed by a cover-plate, which is bolted on. Prac- tically the same construction is shown in Pig. 28. The axle housing illustrated in Pig. 23 is an example of a pressed-steel differential housing made in halves and riveted to the axle tube. 42. Pressed-steel rear-axle housings in which the differ- ential casing and the axle tubes are integral are now in wide use. Such a housing is illustrated in Pig. 29. The housing / is pressed in two halves from sheet steel, the top and bottom halves being welded together by the oxy-acetylene method. The housing has two large openings in the front and rear for inserting or cleaning the differential and the driving-gear assembly. Another pressed-steel axle housing of the same type is shown in Pig. 34, which illustrates the rear axle used on one model of the Marmon automobile. This axle housing is also pressed from sheet steel in two halves, but these are welded together so that the seam is in the vertical plane instead of in the hori- zontal plane, as in the Timken axle. The axle housing shown in Pig. 34 has, in the rear, a large opening a, that is normally closed by a cover-plate — ^removed in the illustration. A gear- carrying plate by shown removed from the differential housing, carries' the differential-gear assembly c. When the gear-carry- ing plate b has been removed from the outer differential housing, the transmission shafts and gears can be pulled out rearwards, the transmission in this case being incorporated in the rear axle. The gear-carrying plate b has in it two large holes d Digitized by Google § 1 GASOLINE AUTOMOBILES 91 and € that receive the rear bearings for the transmission shafts when it is bolted in place. It will be understood that the two halves of the axle shaft. have to be partly withdrawn if the differential-gear assembly is to be removed. 43. Tbrslon Rods and Tubes. — ^The rear-axle housing of a shaft-driven automobile has a tendency to rotate in a direc- tion opposite that in which the wheels and the axle shaft are rotating when the engine is driving the car. This is due to the action of the bevel pinion on the end of the propeller shaft; it tends to climb up aroimd the large bevel driving gear and to carry the differential housing and axle tube with it. When the clutch is thrown out, so that the engine is not driving the car, and the hub brakes are applied, the wheels tend to drag the Fic. 35 axle housing arotmd with them, because the brake bands are supported by the housing; hence, in this case, the axle housing has a tendency to turn in the same direction that the wheels are rotating. In order to overcome the tendency of the rear- axle housing to turn, and to keep it in its correct position, torsion rods or torsion tubes are often provided. Torsion rods are solid or hollow rods or channel-section pressed-steel beams of different design connected at one end to the differential housing and at the other end to some part of the automobile frame, thus forming a brace that prevents the housing from turning. vSometimes the turning effort of the axle housing is taken by a tube that surrounds the propeller shaft and is attached at the rear end to the differential casing. This tube is known as a torsion tube. In other cases, the Digitized by Google 02 GASOLINE AUTOMOBILES §1 turning eflfort is resisted by the rear springs, which are then bolted to spring seats that are rigidly fastened to the axle hotising. 44. A simple method of applying a solid torsion rod is d in Fig. 35, which shows the propeller shaft a of an yile and a sectional view of the outer differential hous- The rear end of the torsion rod c is rigidly attached axle housing; the forward end is connected to the of the car by means of a link and pins. The link- connection allows the axle free play up and down, and ivards and backwards to some extent, on account of iction, while at the same time it resists the tendency Lousing to rotate. A torsion member composed of two rods arranged Dim of a triangle, as used on the McCue rear axle, is Fig. 36 3d in Fig. 36. The rear ends of the hollow rods a are 3 the top and the bottom of the axle housing 6, and the ds of these rods are joined to a suitable fitting c. This in turn, is attached by means of a spring connection ss-member d of the frame of the car. The end of the ; made in the form of an eye, through which the spring ses; thus, the fitting is cushioned between the springs e, •e suspended from d, and the shocks coming on'the frame ir are by this means greatly reduced. Fig. 37 shows the torsion tube used in one model of heson car. The propeller shaft a rotates in the tube 6, 5 rigidly attached at its rear end to the transmission case c. In this instance, the transmission is located at the rear axle, so that its casing is an extension of the differential Digitized by Google SI GASOLINE AUTOMOBILES 93 housing; fixing the torsion tube to the casing has the same effect as fixing it to the axle housing. The axle tube is at- tached to the transmission case by means of a sleeve, or socket, d, which is bolted to the casing and in which the end of the tube is held by the screws e. The forward end of the tube is carried in the casing/, to which it is fastened by the screws g; this casing, in turn, is supported on a roller bearing moimted on the propeller shaft. Any tendency of the rear-axle housing to turn is thus prevented by the torsion tube. The propeller shaft is driven from the engine through the shaft h, 47. Radius Rods. — In the strict sense, radius rods are rods attached at one end to the rear axle of an automobile and at the other end to the frame for the purpose of keeping the axle in alinement with the remainder of the car. These I Fic. 37 rods, one on each side of the frame of the car, are usually pro- vided with two yoke ends, one of which is pinned to a lug car- ried by the spring-seat forging or by a special fitjing on the axle tube, and the other to a lug on the frame, thereby per- mitting the axle to move freely up and down, but maintaining equal distances to the ends of the axle. In chain-driven cars equipped with swivel spring seats, the radius rods also serve as take-up rods for adjusting the distance between the engine sprocket and the differential sprocket. These rods are usually equipped with ttunbuckles that permit of taking up any undue slack caused by wear. When tumbuckles are not used, the yoke ends are made longer and are threaded, so that the chain tension may be varied by screwing or tmscrewing them. 48. The radius rods used on the Stoddard Dayton, "Say- brook" model, automobile are shown at a and 6, Fig. 38, which Digitized by Google 94 GASOLINE AUTOMOBILES § 1 is an illustration of the rear half of the chassis of this car. Each rod is attached at its forward end to a bracket c on the frame d, and at its rear end to a fitting on the axle tube e. The radius rods here shown are fitted with a imiversal joint / at each end, which joints prevent the rods from being strained by any move- ment of the axle. The axle may move freely up or down, but both ends of the axle are always confined lengthwise of the frame. The method of attaching the three-quarter-elliptic springs is also shown in this illustration. The lower half g of each spring is shackled at its forward end by means of links and bolts to a hanger h that is fitted to the frame. The rear end of the lower half is shackled to the upper quarter f , which Pig. 38 is clamped to the rear cross-member of the frame at /. Other parts of the chassis shown in Fig. 38 are the gasoline tank k, the wheel bearing /, the hub brakes m, and the brake rods n. 49. With some shaft-driven cars, the torsion tube that surrounds the propeller shaft, or the torsion rod used with the rear axle, not only serves to take care of the torsional stress produced by the driving pinion, but takes the place of the radius rods used on other cars. Sometimes neither a torsion rod nor radius rods are used, the driving stress being taken by the springs alone, one end of which, usually the forward end, is then hinged to the frame in the case of half-elliptic springs. In the case of three-quarter-elliptic springs, the front end of Digitized by Google § 1 GASOLINE AUTOMOBILES 96 the lower member is hinged to the frame. With full-elliptic springs, the upper half is rigidly bolted to the frame and the lower half to the rear-axle housing; the two halves of the spring must then be hinged together at least at one end. Whenever springs serve as raditis rods, which is almost invariably the case with front axles, the springs must be bolted to spring seats that are rigidly attached to the axle. Diagonal brace rods, which are also commonly classed as radius rods, are used on a niunber of automobiles for the ptir- pose of tying the rear axle and the torsion tube together. One of these rods is located on each side of the car, and extends from the outer end of the axle tube to the forward end of the propeller-shaft housing, or torsion tube. Such brace rods usually have yoke ends, and they are attached in the same manner as the true radius rods just described. This form of Pig. 39 radius rod is not attached to the frame of the car, so that it does not take the driving stress; it serves only as a stiffener, or brace, holding the axle and the torsion tube in their correct relative positions. 50. I>ead Rear Axles. — Dead rear axles, or axles that are stationary, are usually forged I-beam sections, and sometimes they are made with a drop between the spring seats; that is, the middle part is lower than the ends. Such an axle, as vised in the Great Chadwick car, is illustrated in Fig. 39. Each of the spindles a carries two annular ball bearings 6, upon which the wheels rotate. The parts c, between the spindles and the spring seats d, provide room for the radius rods and braking mechanism. The main part e of the axle is dropped below the spring seats, as shown. Some dead rear axles are made perfectly straight and of rectangular cross-section, but as a rule the I-beam section is used. Digitized by Google 96 GASOLINE AUTOMOBILES § 1 51. Dead axles are used with only the double-chain type of drive, in which the reax; wheels are driven from a counter- shaft by means of side chains. The location of the chain and sprockets by means of which the wheels are driven is shown in Fig. 40, which presents a view of the rear of the chassis of a Chadwick automobile. The upper half a of the chain case is lifted, exposing to view the chain 6, which passes around the sprocket c on the end of the countershaft and the sprocket d on the wheel hub. In this case, the sprocket d forms part of the brake drum e, which is bolted to the spokes of the wheel Fig. 40 by the bolts/. On the inside of the chain case, and forming a part of it, is the adjustable radius rod g, by means of which the distance between the sprockets c and d can be adjusted, or changed, to allow for wear on the diain. The chain case, when closed, serves to protect the chain from dust and dirt. 52. Automobile Clialns. — The automobile chains now in use for driving the rear wheels of a car are of the roller type exclusively. This type is so named because it is provided with rollers, which rotate on pins connecting the side links. All roller chains consist of these essential parts, although there Digitized by Google § 1 , GASOLINE AUTOMOBILES 97 are several different methods of attaching the side links to the pins. 53. A Baldwin detachable roller chain, or one that can be separated at each link, is iUnstrated in Pig. 41. The pins a are formed with a head on one side of the chain, and on the other side they are provided with special dips that hold m>z f Pig. 41 the links in place. The rollers b rotate on bushings c that sumoimd the pins a. At one end of each pin are milled two slots d, into which, after the side link e is slipped on, the clips, or fasteners, / are forced and closed by a pair of flat-nose pliers. These clips may be removed by means of a screw-driver or with a special tool provided by the chain manufacturer. The pins, or studs are knurled at the neck where they pass through the links, into which they are forced under pressure. 54. A form of roller chain that can be detached at only one link, called the master linky or connecting link, is illustrated in Fig. 42. This chain, like the one shown in Fig. 41, is made up of rollers a that run on bushings b supported by pins c. In Fig. 42 this case, however, the pins are riveted on both sides of the chain, so that the side links cannot be removed except at the master link. In the illustration, the master link is shown at the right- hand end of the piece of chain. Instead of nmning on rivets, 222B'-« Digitized by Google 98 GASOLINE AUTOMOBILES § ] the rollers e of this link turn on bolts / that are fitted with nuts g and cotter pins fe, so that the chain can be separated at this point by removing the bolts. Each chain is provided with aster link, or connecting link. 1 illustrated in Fig. 42 is known to the trade as the cliain. There are several other makes of detach- 1 as riveted, roller chains on the n:iarket; these are lown to the trade by the names of their makers, tiey embody the same general principle they natur- xmewhat in their details. SPRINGS ANB FRAMES AUTOMOBILE SPRINGS tomobile springs, which are used for support- le and body of an automobUe on its axles, are made and comparatively thin and narrow curved steel aves, of different lengths. These leaves are usually 3r by a bolt at the center, although in some springs eliminated and cUps are used entirely. The shorter usually prevented from moving sidewise by small r ends, by projections of one leaf entering corre- spressions of the next leaf, or by cUps that pass n. Springs are assembled in a ntmiber of different are named according to the form in which they are . 43 shows each of the different types of automobile iitline, as well as the way in which the parts are held lllptlc spring, or, simply, an elliptic spring, is h the leaves are bent, or arched, so as to take the jllipse. Fig. 43 (a) shows a common form of elliptic is composed of an upper and a lower half joined at rith bolts. This spring is sometimes known as the elliptic spring, because the bolts are commonly a head resembling a button. Digitized by Google Pig. 43 Digitized by Google 100 GASOLINE AUTOMOBILES § 1 A single-scroll elliptic spring is illustrated in view (6). This spring differs from the common elliptic spring in that its upper half is provided with a scroll at one end and is joined to the lower half at this end by a shackle and at the other end by a bolt, instead of having bolts at both ends. The scroll ^d is curved down around the lower half and is attached to it hy links and tjolts, forming the shackle. A double-scroll elliptic spring, as shown in view (c), is shackled at both ends, the upper half being provided with two scrolls. The different types of elliptic springs so far described are used as front springs in some cars and as rear springs in others, although they are not employed very extensively in either case. A three-qUarter-elllptic spring is one composed of the bottom part and one-half of the top part of a full elliptic spring, joined either by a bolt or by a shackle. Such a spring, in which the upper qtiarter is scrolled and shackled to the lower half, is shown in view (d). This type of spring is used more than any other as a rear spring on pleasure cars. A lialf-elliptic spring is simply half of a full-elliptic spring. An ordinary spring of this type is shown in view (e) . A specially constructed half-elliptic spring, known as the Titanic spring, which does not have a bolt at the center, is shown in view (0- The leaves of this spring are arched so as to form a himip at the middle, and are clamped over a filler that maintains this himip. Greater strength is claimed for this spring in the cen- ter, on accoimt of doing away with the bolt hole that is neces- sary in the ordinary spring. The half-elliptic spring, or semi- elliptic spring, as it is sometimes called, is used largely on pleas- ure automobiles for supporting the front end of the frame; in a few cases, it is used for supporting the rear end. A cross-spring is a spring that runs crosswise on the car, and therein it differs from the springs previously described, which are arranged lengthwise with the frame. The cross- spring resembles an inverted semi-elliptic spring, as will be seen on referring to view (g), which shows the rear cross-spring of the model T, Ford car. When in place on the car, it is shackled to lugs on the axle at both ends and supports the load at its Digitized by Google § 1 GASOLINE AUTOMOBILES 101 center. Cross-springs are employed only on the lighter class of automobiles. In view (h) is shown a platform spring, of which the side members are half -elliptic springs shackled to the cross-member, and the rear member is an inverted half-eUiptic spring. This spring assembly is used as a rear spring on a few pleasure cars, and it is attached to the frame at the forward ends of the side members and at the center of the cross-spring. What is known as a cantilever spring is shown in view (i). It consists of an inverted and very flat semielliptic spring shackled at its rear end to the rear axle and at its front end to the frame, and pivoted at its middle to the frame. The spring may also be attached to the axle by means of a roller connection, which allows a free backward-and-forward motion. When supported in this manner, it extends imdameath the axle. A cantilever spring may also consist of a quarter-elliptic spring, having its big end rigidly attached to the frame and its small end shackled to the axle. . A cantilever spring is used as a rear spring wherever employed, but it is found at present on a comparatively small number of automobiles, among which may be mentioned the King and the Edwards-Knight cars. 57. After a spring has been compressed, the following upward movement, or recoUy tends to cause separation of its leaves, which separation may result in their breakage. This fact -is especially true of the master leaf, which is that leaf on the ends of which are formed the eyes for attaching it to the frame of the car, to the shackles, or to the other part of the spring in case of other than the half-eUiptic spring. To reduce this danger of spring breakage through recoil, many springs are now fitted with recoil clipSy which are narrow clips that surroimd several spring leaves and the master leaf, and that permit free sliding of the leaves on each other while restraining their separation. Such recoil dips are shown at a, Fig. 43 (c), (d), (0, (g), and (A). Digitized by Google 102 GASOLINE AUTOMOBILES § 1 SHOCK ABSOHBESEUS 58. Types of Sliock Absorbers. — Devices that are used to modify the action of automobile springs and thus prevent excessive vibration of the body of the car while passing over rough roads are called sliock absorbers. These devices are attached to the frame and the springs or axles, so that they offer resistance to the action of the springs and tend to do away with any jar when the springs are suddenly compressed, or when they recoil. There are three types of shock absorb- ers, depending on the method used to obtain the required resistance: (1) those which depend on the frictional resist- ance of two or more surfaces in contact; (2) those which depend on restricting the flow of a fluid; and (3) those which depend on the action of some kind of supplementary springs. 59. Friction Shock Absorbers. — One of the most widely used friction shock absorber is the Truffault-Hartford device, which is shown in Fig. 44 (a). It is made up of circular disks. Some of these move with the arm a, which is attached to the frame c in the manner shown, and some with the arm 6, which is attached to a special spring clip d or to a lug carried on a plate held in place by both spring clips. The frictional ten- sion on the disks may be adjusted by loosening or tightening the nut e. This nut presses against a five-fingered bearing plate / that carries a pointer g for indicating the degree of pres- sure on the outer disk. The action of the springs is modified by the frictional resistance of the disks when the arms a and b move toward each other, as when the springs are compressed,- or away from each other when the springs recoil. 60. The device shown in Fig. 44 (6) is called the Gabriel rebound snubber, or cbeck, because it has no effect on the compression of the spring, but serves merely to check its move- ment on the recoil. It consists of the fabric belting a that is faced with a flexible brass friction band b and is wound about a base consisting of a fixed half c and a movable half d; the two halves of the base are separated by the coil spring e. The telescopic connection / permits the movement of the Digitized by Google SI GASOLINE AUTOMOBILES 103 half d of the base, so that when the springs rebound, the coils erf belting tighten and unwind, thus creating a friction on the brass band and gradually absorbing the shock of the recoil. As the springs compress again and allow the {<o; fiame and axle to move toward each other, the coil spring e expands and takes up the slack in the belting. When in use, the stationary half e of the base is fixed to the frame of the car and the piece of belting is at- tached to the axle, as shown. 61. Fluid Sliock Absorbers. — In one type of the so-called fluid shock absorber, a piston reciprocates in a cylinder in which there are no valves. A small by-pass is provided in the side of the cylinder, so that the frictional resistance to the passage of air through the by-pass from one side of the piston to the other is such that the passengers practically ride on an air cushion. In another fluid shock absorber, glycerine is placed in a vertically arranged cylinder that is connected to the axle, a piston that moves inside the cylinder being connected to the frame. Under the alternate compression and expansion of the springs, the glycerine is Pic. 44 Digitized by Google 104 GASOLINE AUTOMOBILES § 1 forced through small passages from one side of the piston to the other. The hollow piston rod is provided with a regulating valve by which the modifying effect of ^ the shock absorber may be varied at will. 62. Spring Sliock Absorbers. Several devices that absorb road shocks through the action of coiled-steel (a) springs are shown in Fig. 45. In (a) is shown the Sager equal- izing springy which is a simple coiled spring attached to the frame and to the axle, so as to be in compression during the descent of the body and in tension during its rise, and thus modify the spring action in both direc- tions. View (b) shows the J. W. shock absorber applied to a three-quarter elliptic spring. Each of the tubes a contain a helical spring 6, which is held against the upper end of the tube by means of a bolt c having the shape W of an inverted U. The lower end of the spring b presses against a plate that fits inside of the tube and is supported by the nuts d on the end of the I bolt. The plate can slide up or down inside of the tube as the spring is com- pressed or extended. The tubes are attached to the top member e of the spring, and the inverted U bolt is ^^^ carried by the bottom mem- ^'^' *^ ber /, so that as the body Digitized by Google S 1 GASOLINE AUTOMOBILES 105 of the car descends the shock absorber springs are first com- pressed, thtis modifying the action of the main springs. When applied to a car eqtdpped with semi-elliptic springs, one part of the absorber is attached to the frame and the other part to the spring. The shock absorber shown at (c) is a recoil checking device. It consists of a curved spring fastened at one end to the axle, and attached at the other end to the frame by means of a strap. This kind of device is designed to eliminate upthrow of the body in passing over obstructions in the road, and to prevent breakage of the springs by absorbing the recoil. 63. The rebound of the spring is sometimes limited by making use of reversely curved leaves on top of the main leaf, as is shown in Fig. 46. The reverse leaves a and b tend to counteract the reboimd of the spring and thus prevent it from breaking. Before assembling, the reverse leaves have the Pig. 46 form indicatec^ by the dotted lines, so that when they are forced into place, and the bolt c is appUed, they tend to straighten out the spring and in reality to weaken it. But when the spring reboimds after being compressed, these short leaves prevent it from coming back to its original position with too sudden a shock. It is thus seen that this form of shock absorber, like those illustrated in Fig. 44 (6) and Fig. 45 (a), only limits the movement of the spring on the recoil. AUTOMOBILB FRAMES 64. Types of Frames. — ^The frame is that part of the automobile that supports the body and machinery of the car; the frame rests on the springs. With r^ard to the material of which they are built, frames used on pleasure cars are of two kinds, namely, pressed-steel frames and wooden frames. Digitized by Google 106 GASOLINE AUTOMOBILES § 1 Pressed-steel frames are used almost exclusively, wooden frames being used on only a few cars. Where wooden frames are used, they are either armored with steel plates or lami- nated, that is, made up of several layers or lamina- tions. A frame made of wooden sills is used on the Franklin automobile, which offers the best illustration of this type. On this car, the main frame is made of three laminations of second- growth white ash with a thin strip of wood placed on ^ the top of the sills to pre- I vent water from getting between the laminations, the whole being glued to- gether. 65. Pressed-steel nrames. — ^P r essed-steel frames are made up of parts pressed, or formed, to the required shape in hydraulic presses. The longitudinal sills, or side rails, running lengthwise on the car, are practically always made in channel sections, and the cross-members, running from one side to the other, are largely made in the same shapes. Digitized by Google S 1 GASOLINE AUTOMOBILES 107 A perspective view of the pressed-sted frame used on one model of the Packard car is shown in Fig. 47. Besides the various brackets that are riveted to the frame, the front and rear springs and the front axle are shown in place, illustrating how those parts are attached to the sills. The channel-shaped side rails, or sills, a and b are connected by the four cross- members c, d, e, and /, which are also formed in channel sec- tions. The front springs g are hinged to the side rails at the forward end by the bolts h, and are shackled at the rear by the links t and bolts ; and k. These springs are held in place on the front axle / by the spring clips w. The lower halves n of the rear springs are. shackled to the side rails at the forward end, and to the top quarter o of the springs at the rear. These springs are attach^ to the frame by the clips p. The radius rods g, with brackets r for attaching them to the rear axle, are shown in place. Brackets s support the running boards, and brackets t hold the toe board in place; the lever u is part of the reversiog mechanism. While all pressed-steel automobile frames are not built exactly alike, the forgoing will serve to illustrate how the parts are arranged and attached on a typical frame. It is to be noted that this frame is mounted on top of the springs and above the axles. This is the usual method of mounting an automo- bile frame, and is employed on the great majority of cars. In many cars, the frame is raised over the rear axle, as shown in Fig. 47, in order to give clearance over the rear axle and to permit the body to be brought lower to the ground than is possible with a straight frame; such a frame is said to be upswept, or kicked up. When it is offset vertically in the same manner at the front, the frame is spoken of as a double kick-up frame. Many frames are narrowed at the front end in order to give a larger turning radius to the front wheels, which means a shorter turning radius for the car; such a frame is said to be inswept at the front. The frame shown in Fig. 47 has this construction. 66« XJndersltiiig Frames. — ^An underslung frame is a frame that is located underneath the axles and suspended from the springs. This type of frame gives a low center of Digitized by Google 108 GASOLINE AUTOMOBILES § 1 gravity to the car, but requires the use of larger wheels than can be used on cars having the frame mounted on top of the springs and axles. tne subtrame is generally made ot pressed-steel shapes ot chan- nel cross-section, although tubular subframe members are sometimes foimd Digitized by Google GASOLINE AUTOMOBILE ENGINES PART 1 PRINCIPLES OF OPERATION FOUR-CYCLE PRINCIPLE DEFINITIONS AND NAMES OF PARTS 1. An internal-combustion engine is an engine in which power is generated by burning within the cylinder, a combus- tible mixture of air and gasoline, air and kerosene, or air and any other liquid fuel. The burning of the fuel results in the production of gases of high temperature and pressure, which act directly on a piston that moves back and forth in a cylin- der to which the air and fuel are admitted and from which the burned gases are discharged by means of suitable valves. The required mechanical work is done by the piston through the proper mechanism. ^Internal-combustion engines are classified as single-acting engines and double-acting engines, depending on their construction and operation. Engines in which the cylin- der is so constructed that gas is admitted to only one end and burned on only one side of the piston are single-acting engines, because the expanding gases force the piston in but one direction; engines in which gases are admitted to each end of the cylinder alternately, and burned first on one side of the piston and then on thp other, forcing it first in one direction and then in the other, are double-acting engines. All gaso- line automobiles now in use are driven by sonje type of the conrmaHTSD by intkrnationai. tkxtbook company, all riohts rmkrvkd 52 Digitized by Google i Digitized by Google § 2 GASOLINE AUTOMOBILE ENGINES 3 single-acting intemal-combiistion engine. Double-acting inter- nal-combustion engines have never proved successful as auto- mobile engines, but are used to some extent as stationary engines, being sometimes employed in power plants where gas instead of gasoline is used as fuel. 2. An external view of a typical modem poppet-valve gaso- line automobile engine is presented in Fig. 1, which shows the left side of one model of the Pierce-Arrow six-cylinder engine. The cylinders are cast in pairs — ^that is, there are two cylinders in each of the castings, or blocks, a. The cylinders are ver- tically arranged on the crank-case 6, which supports them and which contains a shaft c, called a crank-shaft, extending its entire length. The crank-shaft, being rapidly rotated by the up-and-down movement of the pistons in the cylinders, through suitable cranks and connecting-rods, imparts a rotary motion to the driving mechanism of the automobile through a clutch located at the rear of the engine inside of the flywheel d. The combustible mixture enters the cylinders at the right side of the engine, and the btuned gases resulting from the explosions escape through the outlet manifold e. The piping / is for the purpose of circulating water through jacket spaces surroimd- ing the cylinders and thus cooling them and preventing them from being burned or otherwise injured by the heat due to the explosions. The /an g, located at the forward end of the engine, also belongs to the cooling system, its purpose being to draw air through a radiator, which is used to cool the circulating water. Other important parts shown are the oil pump h, with the necessary piping, for lubricating the engine; the water pump i, for circulating the cooling water; an electric generator k, for supplying electric current for lighting purposes as well as for ignition; the wires I, for carrying electric current for igniting the combustible mixture in the cylinders ; and the valve springs m, used for closing the valves, which permit the gases to enter and escape from the cylinders. The engine is supported in the frame of the car at four points by means of the supports n, two of which are located on each side. These supports are secured to the side members of the frame. Digitized by Google Pig. 2 Digitized by VjOOQ IC § 2 GASOLINE AUTOMOBILE ENGINES 5 3. A cross-sectional view of the Pierce-Arrow six-cylinder engine showing the arrangement of the parts inside of one of the cylinders is seen in Fig. 2. This illustration shows one of the cylinders cut in half crosswise and viewed from the forward end of the engine. The oil pump, water pump, and other accessories are omitted in order to simplify tJie view. The piston a is free to move up and down within the hollow, or bore, of the vertical cylinder b. The piston is coimected to the crank c by means of the connecting-rod d, which is attached at its upper end to the piston pin e and at its lower end to the crank-pin J, so that an up-and-down motion of the piston causes the crank to rotate. The crank-shaft g, being integral with the cranks, also rotates, and through it the driving mechanism of the car is caused to turn. The crank-shaft is carried in bearings supported by the crank-case h. At i is seen an opening called the inlet port, through which the mixture of gasoline vapor and air enters the cylinders; and at / is the exhaust port, through which the burned gases, or products of combustion, are expeUed. These openings are fitted with valves k and /, called the inlet valve and the exhaust valve, respectively, by means of which the ports may be closed. The wall of the port on which the valve rests when in the closed position is known as the valve seat. The valves are operated by means of cams m and push rods n. The cams are carried on cam-shafts o, which are rotated by means of gears from the crank-shaft, and, as the cams revolve, the lobes, or raised por- tions, strike on and raise the push rods, which in turn lift the valves. This cam-shaft always rotates at one-half the speed of the crank-shaft; in other words, for every two revolutions of the crank-shaft the cam-shaft ntiakes one revolution. It will be noticed that in the illustration the inlet valve cam is turned so that its lobe is directly underneath the push rod, in which position the inlet valve is raised and the inlet port opened; the lobe of the exhaust valve cam is at one side of the push rod, in which position the exhaust valve remains on its seat in a closed position. The push rods are provided at the bottom with rollers on which the cams strike. The valves are held in place by the guides p in which the valve 222B— 9 Digitized by Google GASOLINE AUTOMOBILE ENGINES § 2 5 and by the springs q. The springs are constantly i so that they push downwards on the caps r and alves closed except when the lobes of the cams strike xis. nder head is seen at s and between it and the valves :^ t, called the combustion chamber, or the compres- because it is in this space that the burning, or com- f the fuel, takes place. In the cylinder head are i V, which can be taken out when the valves are to be )r the cylinder cleaned. The spark plugs w are to the combustion chamber for the purpose of pro- ;tric sparks to ignite the fuel,'and the priming valve x means for pouring extra fuel into the cylinder when or for pouring kerosene in to clean the piston face •walk. > end of the cylinder that is attached to the crank- led the crank end, and the other end is called the The movement of the piston from the head end ik end is called the forward, or outward, stroke; the in the opposite direction is called the return, or oke, le piston has reached the end of either stroke, the -rod and crank are in a straight line, and the pres- 5 gases on the piston is transmitted directly to the bearings, none of it being used to turn the crank, crank occupies this position it is said to be on its ter. There are two dead-center jx^sitions, corre- ;o the two extreme jx^sitions of the piston. When is at the extreme bottom end of its stroke, the crank iter, or lower, dead center; and when the piston is at le top end of its stroke, the crank is on its inner, ^£ad center. \ cliarge is a mixture of fuel and air taken in at 5 of the engine. It varies according to the con- operation, and may sometimes be sufficient to fill ler completely at atmospheric pressing, while at Digitized by Google §2 GASOLINE AUTOMOBILE ENGINES 7 other times it may be reduced. The proportions of fuel and air may also vary from time to time. The burned gases, which are expelled from the engine after having performed the work required, are known as the exhaust gases, or, simply, the exhaust. These gases are waste products and are allowed to escape into the atmosphere. 6. Gasoline automobile engines are either vertical or hori- zontal, depending on the manner in which the cylinders are arranged. Engines having their cylinders arranged ver- tically, like that illustrated in Figs. 1 and 2, are vertical engines ; engines having their cylinders arranged horizontally are horizontal engines. Practically all engines now used to propel gasoline pleasure automobiles are of the vertical type. OASOLINE-ENOINE CTCLB 7. A cycle is any chain, or series, of events, or happenings, occurring over and over in the same order. As applied to a gasoline engine, the term cycle refers to the operations, or events, that take place within the cylinder from one explosion to the next, and by means of which the fresh charge is drawn into the combustion chamber and exploded and the exhaust gases expelled. These events always occur in the same order and are repeated after each explosion. The cycle on which an internal-combustion engine operates is one of the distin- guishing features of different types. 8. The modem cycle of gasoline engines is known as the Beau de Hoclias cycle, after the name of the inventor, and more commonly as the Otto cycle, after the name of the engi- neer who carried out its early commercial application. This cycle, in its broad and strictly scientific meaning, does not take into consideration the method of getting the charge of com- bustible mixture into the cylinder nor that of expelling the hot burned gases. The steps of the cycle in the engine of Fig. 2 are as follows: Suppose that, at the beginning of operations, the valves are closed, that the piston is at its position farthest out toward the crank-shaft, and that the cylinder is filled with a com- Digitized by Google 8 GASOLINE AUTOMOBILE ENGINES § 2 bustible mixture at atmospheric pressure. By forcing the piston inwards to the completion of the inward stroke, the charge will be compressed into the compression space, or com- bustion space. Now by igniting the compressed charge, the pressure will be increased still more by the heat of combustion. The pressure tends to drive the piston out- wards, and as soon as the rotating crank-shaft has made the angle between the connecting-rod and crank suflSciently great, the pressure of the hot gases against the piston face will drive the crank-shaft. The biimed gases expand to fiU the increas- ing volume of the cylinder as the piston moves outwards and the pressure decreases. At the completion of the outward stroke, the exhaust valve is opened and the hot biimed gases escape by expansion tmtil the pressure falls to that of the atmosphere. This completes the Otto heat cycle. 9. The method of expelling the burned gases that remain in the cylinder at atmospheric pressure and of taking in a fresh charge of combustible mixture has not yet been considered. This is accomplished in two distinct ways, which are the foim- dation for the commercial names, four cyck and two cycle, as applied to automobile engines. 10. A four-cycle engine is one in which fovir complete strokes of the piston are required to complete the cycle. In this engine the burned gases remaining in the cylinder after the exhaust valve has been opened and part of the hot gases removed by expansion are expelled in part by a separate inward stroke of the piston, and a fresh charge is drawn into the cylin- der through the inlet port by a separate outward stroke. Gen- erally speaking, one event occurs during each of the four strokes of this cycle; that is, considering the stroke by which the charge is drawn into the cyUnder as the first stroke, the mixture is compressed during the second stroke, burned during the third stroke, and the exhaust gases are expelled during the fourth stroke, after which the conditions are the same as at first and the cycle is complete. !!• A two-cycle engine is one in which only two strokes of the piston, corresponding to one revolution of the crank- Digitized by Google §2 GASOLINE AUTOMOBILE ENGINES 9 shaft, are required to complete the cycle. In this cyde an explosion occurs on each downward stroke of the piston, the fresh charge being admitted and the exhaust gases expelled at or near the end of this stroke. Hence, for the same number of revolutions of the crank^shaft, there are twice as many explosions in the cylinder of a two-cycle engine as in that of a four-cycle engine. However, this does not mean that the power developed by a two-cycle engine is twice as great as that produced by a four-cycle engine of the same size and speed, for, on accotmt of the inefficient scavenging, or cleaning, of the 'cylin/ier after the explosion and the lower compression pres- sure in the two-cycle engine, the explosions are not so power- ful as in the four-cycle engine. It is generally estimated that a two-cycle engine of a certain size and speed will develop about L65 times as much power as a four-cycle engine of the same size and speed. 12. The two types of internal combustion engines just defined are sometimes designated by the longer terms four- stroke OtUhcycle engine and two-stroke Otto-cycle engine to dis- tinguish them from other engines that operate on cycles that differ from the Otto. However, since all automobile engines of the internal-combustion class operate on the Otto cycle, the terms four-cycle and two-cycle are suflSdently definite in meaning when limited to this field of application. 13. It has been found that by compressing the charge before igniting it, a greater amount of power can be obtained from a given quantity of fuel than by simply burning it at atmospheric pressure. In other words, the effidency of the btemal-combustion engine is increased by compressing the charge before igniting it. Compressing the charge heats it; hence, on account of the danger of overheating the cylinder the compression pressure is limited to from 60 to 75 pounds per square inch, as shown by a pressure gauge. Another disadvantage of too high a compression is that the bearings and joints of the moving parts of the engine are liable to give trouble by knocking or pounding. All internal-combustion automobile engines compress the charge before igniting it. Digitized by Google 10 GASOLINE AUTOMOBILE ENGINES § 2 OPEERATION OF FOUR-CJTCLE ENOINB 14. As already explained, four separate strokes of the piston, two outwards and two inwards, are required to complete a cycle in the cylinder of a four-stroke cycle engine. These four strokes are shown diagrammatically in Fig. 3, which presents four cross-sectional views, each showing the cylinder a and crank-case b cut at right angles to the crank-shaft c, exposing to view the piston d, connecting-rod e, inlet and exhaust valves/ and g, and cams h and i. These views illustrate the various steps in the operation of the four-cycle type of automobile engine and the corresponding positions of the valves. The engine presented in the illustration does not represent any particular make but shows the principle on which aU f otir-cycle gasoline engines are operated. If the different events here described are understood there will be no difficulty in comprehending the operation of any engine of this type. 15. The first stroke in the operation of the engine is shown in Fig. 3 (a). During this stroke the piston d, following the motion of the crank-shaft c, which is being propelled by the force of the preceding explosion, moves downwards as indicated by the arrows. At or slightly after the time that the piston starts on this stroke, the inlet valve / is opened by means of the cam h. The downward motion of the piston tends to pro- duce a vacutun in the upper part of the cylinder, so that com- bustible mixture flows into the cylinder through the inlet port, as shown by the curved arrows, to fill up this vacuum, or, in other words, a charge is drawn into the cylinder. At the end of this stroke, or slightly after, the inlet valve closes. The exhaust valve g is kept closed during this stroke so that none of the entering charge can escape through the exhaust port. Because of the fact that the combustible mixture is drawn into the cylinder during this stroke, it is usually called the suction stroke, although it is also variously known as the charging stroke^ admission stroke, inlet stroke^ and induction stroke. 16. During the second stroke in the cycle of operations, the piston d, still driven by the crank-shaft c, moves upwards as Digitized by Google 11 Digitized by Google :jasoline automobile engines § 2 he arrow in view (b). Both the inlet valve/ and the ive g are closed dming this stroke, so that the com- Lture that was drawn into the cylinder on the suction >w compressed into the small space between the top n, when it is at tHe top of its stroke, and the cylinder y thus compressing the charge into a small space ing it, a greater amount of power can be obtained jn quantity of fuel as previously explained. About tiat this stroke, which is called the compression completed, the charge is ignited by means of an rk. e combustible mixture that was drawn into the the first stroke of the piston and compressed on the )ke is completely burned during the third stroke, iston is again on its downward movement, as shown . The combustion of the charge is so rapid during as to be practically instantaneous, and is usually explosion. The pressure in the cylinder, resulting plosion, drives the piston downwards and outwards, 3 crank-shaft by means of the connecting-rod and >th valves remain closed from the beginning to nearly this stroke. The exhaust valve g is opened by the before the end of the stroke and part of the burned ie into the air, so that the pressure in the cylinder as low as that of the atmosphere. It is during this stroke of the piston that work is done and a forward given to the piston, so that it is called the workinsr tptdse stroke, explosion stroke, or combustion stroke, view (d) the piston d is seen on the fourth and last the cycle. During this stroke it moves upwards, 3n by the crank-shaft, and expels the greater part aining burned gases from the cylinder through the )rt. However, the combustion chamber, between r head and the face of the piston, when at the top of its stroke, remains filled with the burned gases at the com- pletion of this stroke. The pressure of these residual gases is generally about the same as, or somewhat higher than,- that of Digitized by Google §2 GASOLINE AUTOMOBILE ENGINES 13 the external atmosphere. The inlet valve remains closed during this stroke and the exhaust valve remains open, it being closed about the time that the piston reaches the end of its stroke. This upward movement of the piston is known as the exhaust stroke, and its completion ends the cycle of operations. Fol- lowing the exhaust stroke, the suction stroke again begins and the series of operations takes place over and over in exactly the same order. « 19. Four-cycle automobile engines are classified as poppet- valve engines and non-poppet-valve engines, depending on the type of valve used for controlling the admission of fuel into the cylinder and the escape of burned gases therefrom. Poppet-valve engines are those that make use of the so-called poppet type of valve such as shown in Figs. 2 and 3; non-poppet-valve engrlnes are those that employ other types of valves for inlet and exhaust, such as sliding valves or rotary valves. Non-poppet-valve engines operate on exactly the same principle as the poppet-valve engine just described. TWO-CYCLE PRINCIPLE OPERATION OP TWO-POBT TWO-CYCLE ENGINE 20. The operation of the two-cycle engine differs from that of the four-cycle engine in that but two strokes of the piston, instead of four, are required to complete a cycle; or, in other words, each downward stroke of the piston is a power stroke. This cycle of operations is made possible by making use of an air-tight crank-case by means of which the charge is compressed slightly before being admitted to the cylinder, or by employing a pump or air compressor for this purpose, so that a separate suction stroke is unnecessary. In addition, the burned gases are expelled at the end of the working stroke, thus eliminating a separate exhaust stroke. The principle of operation of the two-cycle engine is illustrated diagranunatically in Fig. 4, which shows three cross-sectional Digitized by Google ^ s: ^ 14 Digitized by Google § 2 GASOLINE AUTOMOBILE ENGINES 15 views of what is known as a two-port two-cycle engine, so named because only two ports enter the bore of the cylinder, distin- guishing it from the three-port engine, which has three ports opening directly into the cylinder. However, the principle on which the two tjrpes operate is exactly the same. Each view in the illustration shows the cylinder and crank-case cut in half, exposing to view the various parts of the engine and showing the different positions of the piston. At a is shown the piston; at 6, the crank-shaft; at c, the crank; at d, the crankpin; at e, the connecting-rod; at /, the exhaust port; at g, the inlet, or transfer, port; at fe, the transfer passage, or by- X^ass, leading from the crank-case to the cylinder; at t, the inlet valve in the crank-case; at /, a deflector, or baffle plate, on the «id of the piston; at i, the spark plug at which the spark is produced; and at /, the crank-case. 21. In Fig. 4 (a) it may be assumed that the cylinder has been filled with a combustible mixture and the piston is com- pressing this charge during its inward stroke. At the same time, the partial vacuiun created by the upward movement of the piston draws a fresh charge into the crank-case / through the inlet valve t. At about the end of this stroke the mixture of gasoline vapor and air, which has been compressed into the compression space at the top of the cylinder, is ignited by a spark formed at the spark plug k. This completes the first stroke of the cycle, which is called the compression stroke. 22. During the second stroke combustion takes place; that is, the charge in the cylinder is burned. The piston is forced downwards by the rapid expansion of the burned gases and a rotary motion is given to the crank-shaft by means of the connecting-rod and crank. The outward motion of the piston on this stroke slightly compresses the mixture in the crank-case Z, the inlet valve i having been closed at about the end of the first, or inward, stroke. This downward movement of the piston, called the impulse stroke, is illustrated in (6). As the piston approaches the completion of the impulse stroke, it begins to uncover the exhaust port /. As soon as the edge of this port is uncovered, the burned gases in the Digitized by Google 16 GASOLINE AUTOMOBILE ENGINES § 2 cylinder begin to escape into the atmosphere. This escape is, or should be, rapid enough to allow the pressure in the cylinder )w that of the precompressed combustible mixture ik-case by the time the piston has moved out far )egin to tmcover the transfer port g, through which a e then begins to enter the cylinder and to drive out gases. shows the burned gases escaping and a fresh charge 1 into the cylinder. The baffle plate ; deflects the harge, so as to prevent it from flowing out with gases. The more or less complete expulsion of the es and the drawing of a fresh combustible charge linder are accomplished during the time the piston through a small portion of the latter part of the :oke and early part of the inward stroke. The ports )sed by the piston during the early part of the inward T which the fresh charge is compressed in the com- imber, and more combustible mixtvu-e is drawn into ase. ; valve i opening into the crank-case may be operated matically by the suction of the piston or mechanic- ms of a cam and push rod. le series of operations taking place during the two- e in the form of engine just described may be tabu- lows: • TWO-STROKE CYCLE I Crank-Case First Stroke, Inwards ion; pressure rises; Suction; inlet valve open; *ar end of stroke, pressure falls below atmos- Dy explosion and phere. )f pressure. Second Stroke, Outwards Expansion; pressure falls; Compression; pressure rises exhaust followed by entrance to from 4 to 8 pounds; char- of fresh mixture from crank- ging cylinder; pressure falls case. to atmospheric pressure. Digitized by Google §2 GASOLINE AUTOMOBILE ENGINES 17 OPERATION OP THBEE-POBT TWO-CYCXE ENGINE 24. The three-port two-cycle type of automobile engine differs from the two-port two-cycle type in that the inlet port opens into the cylinder bore at a point near the crank-case and is opened and dosed by the piston, instead of opening directly into the crank-case. This arrangement ob\dates the use of a valve of any kind, as the piston takes the place of valves, so that the engine is also known as a valveless iwo<ycle engine. A three-port two-cycle en- gine is illustrated diagramma- tically in Fig. 5, which is a cross-sectional view of a cylin- der of an engine of this type and shows the location of the various ports. The inlet port is seen at a, the transfer port at 6, and the exhaust port at c. In the position shown the pis- ton d has just completed its downward, or power, stroke and a fresh charge is flowing from the crank-case e through the transfer passage/and trans- fer port b into the cylinder. The pressure of this incoming fresh charge helps to drive the products of combustion, or exhaust gases, out through the exhaust port c, as indicated by the curved arrows. Fig. 5 25. The operation of the engine shown in Fig. 5 is as follows : Starting with the position shown, as the piston moves on its upward stroke the combustible mixture is compressed into the compression space in the upper part of the cylinder, and at the same time the inlet port a is uncovered by the piston so that a fresh charge is drawn into the crank-case by the suction Digitized by Google 18 GASOLI^ AUTOMOBILE ENGINES §2 of the piston. At ^bout the end of this stroke the mixture in the upper part of the cylinder is fired by a spark produced at the spark plug g and the piston is driven downwards on its second, or impulse, stroke by the force of the resulting explosion. During this downward movement of the piston the fresh charge that had been drawn into the crank-case is slightly precom- pressed so that it will flow into the cylinder through the transfer passage / when the transfer port b is uncovered. As the piston nears the end of its impulse stroke the exhaust port and transfer port are uncovered, admitting the fresh charge into the cylinder and allowing the exhaust gases to escape into the atmosphere. At the end of the impulse stroke the conditions indicated in the illustration again exist and the cycle is completed. This cycle of operations is gone through again and again. The raised portion h on the face of the piston acts as a deflec- tor, or baffle plate, which prevents the fresh charge from escap- ing with the burned gases through the exhaust port. Other parts of the engine which are shown are the connecting-rod i and the crank-pin k. TYPICAL AUTOMOBILE ENGINES POUR-CYCLE ENGINES ARBANOEMENT OF ENGINE CYLINDERS 26. General Eng^ine Construction and Control. — ^The typical automobile engine has four or six cylinders, is of the vertical four-cycle type, and runs at an average speed of about 1,500 revolutions per minute when at full speed. Except in rare cases the maximum speed is about 1,800 revolutions per minute. Automobile engines develop from 20 to 80 horse- power, depending on the size and number of cylinders. The engine is ordinarily governed by regulating the amount and quality of the charge that enters the cylinders, and by varying the time at which the mixture is fired. This is accomplished by the levers that are usually located on or near the steering wheel in front of the driver, although in some engines the time of Digitized by Google §2 GASOLINE AUTOMOBILE ENGINES 19 ignition is varied by an automatic device, or governor, so that no hand spark lever is necessary. Some engines are also pro- vided with an automatic governor by means of which the fuel supply is automatically regulated and the speed controlled within certain limits. In a number of the earlier makes of automobiles, engines with a single cylinder or with two cylinders were used as a means of propulsion, but as the automobile industry developed, engines with a greater nxunber of cylinders were required in order to secure the power and smooth running demanded in the modem pleasure car. As a result, the four- and six-cylinder four-cycle engines are used on practically all pleasure cars of today, and the single- and double-cylinder types are not being Pig. 6 manufactured for this piupose, although a few of these engines are still ini existence. 27. Two-Cylinder Arrangement. — ^The most popular type of two-cylinder four-cycle automobile engine manufac- tured is known as the doyble-opposed engine, which has its cylinders arranged horizontally as shown in Fig. 6. The two cylinders c are placed on opposite sides of the crank-shaft a, and the cranks b are directiy opposite each other. By this arrangement of cylinders, the explosions and consequent impulses on the piston occur every revolution, first in one cylinder and then in the other. While one of the pistons d is on its impulse stroke, the other is on its suction stroke. Both pistons move toward the crank-shaft at the same instant and with the same speed; they also recede from the Digitized by Google lOBILE ENGINES § 2 each having the same speed They are therefore balanced ght tendency to move sidewise are not exactly opposite each are not exactly in Une. ylinder four-cycle automobile he cylinders arranged side by rank-shaft, as shown in Fig. 7, eneral use in pleasure cars and are not now manufactured for that purpose. Such engines were usually made with the cranks a, Fig. 7, side by side so that the pistons b moved in unison. This arrangement secures an equal time interval of one revolution of the crank- shaft between the impulses; when one piston is moving down on its power stroke the other is moving down on its suction stroke, so that the impulses alternate, occurring first in one cylinder and then in the other. However, with the cranks arranged in this way it is extremely diiBcult to balance the moving parts so as he automobile. When the two I part, as shown in the illustra- ers, and are said to be en bloc, which is a French expression for "in block." 29. Four-Cylinder Arrangement. — ^The four-cylinder four-cycle gasoline engine, which is the most widely used type of automobile engine, has its cylinders vertically arranged on one side* of the crank-shaft. This arrangement is seen in Fig. 8, which is a diagrammatic illustration showing the cylin- Digitized by Google §2 GASOLINE AUTOMOBILE ENGINES 21 ders cut in half and exposing to view the pistons a, the cranks 6, and the connecting-rods c. For each cylinder of a four-cylinder engine there is a corre- sponding crank; hence, in this engine there are four cranks, each one being part of the crank-shaft d, which is offset to form the cranks as shown. In order to secure a uniform application of power and smooth running of the engine, it is essential that the cranks be arranged around the crank-shaft in such a man- ner that no two pistons will be on their impulse strokes at the same time, but that the explosions in the various cylinders wiU occur in regular order with equal intervals of time between them. This result is obtained by placing the cranks so that the two end ones are on one side of the crank-shaft and directly opposite the two middle ones, which are on the other side of the crank-shaft. In other words, the cranks of a four-cylinder four-cycle engine are arranged so that when the two end ones stand vertically downwards, the two middle ones stand vertically upwards, as shown in Fig. 8. The two outer cranks are then said to be at an angle of 180^ with the two inner ones. 30. Order of Explosions of Four-Cyltnder Engines. With the cranks of a four-cylinder four-cycle engine arranged as shown in Fig. 8, two of the pistons will be descending while two are ascending. For instance, while the pistons in cylin- ders 1 and 4 are descending on their working and suction strokes, respectively, those in cylinders £ and S are moving upwards on their compression and exhaust strokes. Ehiring the half of a revolution of the crank-shaft represented by these move- ments of the pistons, the explosion occurs in cylinder 1 and work is done in that cylinder. At the same time a charge is being compressed in cylinder £, so that during the following half revolution, the piston in cylinder ;^ is on its working stroke, that in cylinder S is on its suction stroke, and those in cylin- ders 1 and 4 are moving upwards on their exhaust and com- pression strokes, respectively. Ehiring the third half revolu- tion, the pistons in cylinders 1 and 4 again descend, this time, however, with that in cylinder 4 on its working stroke and that in cylinder i on its suction stroke; the pistons in cylinders 2 222B— 10 Digitized by Google 22 GASOLINE AUTOMOBILE ENGINES § 2 and S are at the same time ascending on their exhaust and com- pression strokes, respectively. On the fourth half revolution of the crank-shaft, when the pistons in cylinders i^ and 3 descend, that in S is on its working stroke, and that in ;^ is on its suction stroke, while those in cylinders 1 and 4 move upwards on their compression and exhaust strokes, respectively. On the following strokes of the pistons an explosion will again occur in cylinder 1, the cyde of operations in that cylinder having been completed, and the same order of events as just named is repeated as the crank-shaft revolves. Fig. 8 31. In brief, the order in which the explosions, or impulses, take place in the various cylinders of a fovir-cylinder four- cycle automobile engine is as follows: Starting with cylin- der 1, an explosion first occurs in that cylinder, then one occurs in cylinder j^, then in cylinder 4» and finally in cylinder S. Two full revolutions of the crank-shaft are necessary in order to complete the various operations required to produce an explosion in each cylinder; hence, an impulse is given to the Digitized by Google § 2 GASOLINE AUTOMOBILE ENGINES 23 crank-shaft each half of a revolution. The order in which the imptilses occur in the various cylinders is called the order of explosions or the order of firing. The order of firing just explained is said to be one, two, four, three, or more briefly, 1-2-^-3. Since the pistons in cylinders 1 and 4 move together, or in tinison. and those in cylinders 2 and S also move together, or in unison, in a four-cylinder fotir-cycle engine, it is evident that the events taking place in cylinders 1 and 4 may be reversed, or those taking place in 2 and 3 may be reversed, in which case the order of firing becomes one, three, foiu-, two, or 1-3-4-2. The sequence of events may be traced out in the manner explained in Art. 30 by substituting cylinder 4 for cylinder 1, or cylinder 2 for cylinder 5, and vice versa. The two orders of firing just named are used exclusively in four-cylinder four-cycle automobile engines. The order employed depends on the manner in which the valve cams are set to open and close the inlet and exhaust valves; naturally, the sequence in which the ignition spark is made to occur in the several cylinders must be the same as called for by the construction of the engine. It is the usual practice to assign the number 1 to the cylinder nearest the front end of the car and to number those to the rear of it in succession 2, 3, etc. 32« Six-Cylinder Arrangement. — On account of their flexibility and smooth running qualities, automobile engines having six cylinders are used extensively, especially in the larger cars. The six-cylinder engines are much the same in form as the usual type of four-cylinder engines, the cylinders being arranged vertically in a row above the crank-shaft. The cranks in a six-cylinder engine are arranged in pairs, that is, there are three pairs, each pair consisting of two cranks located on the same side of the crank-shaft and in the same plane. The two cranks of a pair may be either adjacent to each other or separated by other cranks placed between them. A common arrangement is shown in Fig. 9, which is a diagram- matic illustration showing the relative positions of the cranks Digitized by Google 24 GASOLINE AUTOMOBILE ENGINES § 2 and pistons. The cranks a and/ form a pair, b and e form a pair, and c and d form a pair, the cranks of each pair being in line, as shown in view (6). As generally stated, the cranks of cylinders 1 and 6 form a pair, those of cylinders 2 and 5 form a pair, and those of cylinders S and 4 form a pair. The pairs are located at equal intervals arotmd the crank-shaft^ that is, at an angle of 120® with each other. The two pistons of each pair move in unison, that is, when one piston is on its up stroke, the other is also on its up stroke, and when one is on its down stroke, the other is also on its down stroke. 33« Order of Explosions of Six-Cylinder En^^ines. The impulses in the cylinders of a six-cylinder four-cycle auto- mobile engine occur at intervals of one-third of a revolution; therefore, there are three impulses per revolution. Consider- ing the cylinders as being in pairs corresponding to the three pairs of cranks, the explosions first occur in one cylinder of each pair and then in the other cylinder of each pair in the same order. A common firing order is 1-5-3-6-2-4. With this order, an explosion first occurs in cylinder 1, then in cylinder 5, then in cylinder 3, after which the explosions occur in the other members of the pairs in the same order; that is, first in cylin- der 6, which completes a pair with cylinder 1 ; then in cylin- der 2, which completes a pair with cylinder 5; and finally in cylinder 4, which is the mate to cylinder 3. Other orders of firing possible with the crank arrangement shown in Fig. 9 are: 1-2-3-6-5-4, 1-2-4-6-5-3, and 1-5-^ 6-2-3. When cranks 3 and 4 and cranks 2 and 5 are inter- changed, the following firing orders may be obtained: 1-3-2- 6-4-5, l-3-5-fr4-2, l-4r-5-6-3-2, and l-4r-2-6-3-5. In aU of these firing orders, explosions occur first in any three cylinders belonging to different pairs and then in the other cylinders of the pairs taken in the same order. The various orders can be 'traced out just as in a four-cylinder engine by starting with the explosion stroke in cylinder 1 and the suction stroke in cylin- der 6, compression and exhaust occiuring in the two cylinders forming the pair that is 120° behind cranks 1 and 6 and following out the events of the cycle in each cylinder. Digitized by Google ■"—'^'"'^^ T Digitized by Google 26 GASOLINE AUTOMOBILE ENGINES § 2 In practice, the different firing orders are obtained by using different arrangements of the cams which open the inlet and exhaust valves, and employing ignition systems wired so that the electric spark is sent to the cylinders in the sequence desired. TYPICAL POUB-CYLINDEB ENGINES rpes of Engines. — Four-cylinder four-cycle auto- yines may be said to be divided into three classes, on the manner in which the cylinders are assem- lely: those having their cylinders cast separately; ing their cylinders cast in pairs; and those having ders cast in one piece, that is, en bloc. Cylinders rs are the most widely used, although engines employ- )ck type of casting are rapidly increasing in ntmiber. cast separately are decreasing in number. Engines cylinders cast en bloc have the advantage of being compact, and their various parts are always in irlinders Cast Separately. — ^An example of a four- )ur-cycle automobile engine with the cylinders cast is presented in Figs. 10 and 11, which show two be Overland model 71 engine. In Fig. 10 is seen a udinal section and side view, and in Fig. 11 is shown ition through one of the cylinders. In reading the I both illustrations should be referred to. Each of ylinders, a, 6, c, and d, is a separate casting and is uuivcvj. j>cparately to the crank-case e. Both the inlet and the exhaust valves are located on the same side of the engine, as shown at / and g, thereby permitting the use of a single cam- shaft h for operating both sets of valves. The cam-shaft is driven from the crank-shaft by means of gears enclosed in the casing i. At the forward end of the engine and driven from the crank-shaft by the belt ; is a fan fe, which is a part of the cooling system, and at the rear end is the flywheel /, inside of which is a clutch for connecting the engine to the driving mechanism of the automobile. The toothed wheel m Digitized by Google Digitized by Google 28 GASOLINE AUTOMOBILE ENGINES §2 accommodates a silent chain that turns a dynamo used for supplying current for electric lighting. The engine cylinders are cooled by means of water flowing through the jacket spaces n. I, n le Digitized by Google §2 GASOLINE AUTOMOBILE ENGINES 29 atmosphere to provide a way of escape for any hot gases going past tiie pistons. The breather pipe is also used as a filler pipe through which lubricating oil can be poured into the crank- case. The spark plugs r in this engine are located directly over the inlet valves, and the priming valves, or cups, s are located directly over the exhaust valves. An oil pump t forces the lubricating oil from a reservoir u in the bottom of the crank-case through certain pipes and into the troughs v^ from which it is picked up by the ends of the connecting-rods w. The cranks of the engine shown in Figs. 10 and 11 are arranged in the usual manner, that is, when the two middle cranks x and y stand vertically downwards, the two end cranks o' and b' stand vertically upwards. The operation of the engine is on the ordinary four-cycle principle, the explosions occurring in the order 1-3-4-2. The engine is supported in the frame of the automobile at two points near the rear end and at one point in front. This method of support is known as the three-point suspension. The advantage claimed for suspending the engine at three points is that it is not subjected to all of the torsional stresses set up in the frame by the car turning comers or travel- ing over rough places. In an engine with cylinders cast sep- arately there are usually five crank-shaft bearings — one between each two cylinders, and one at each end, as seen at c\ 36. By referring to Fig. 11, it is seen that the center line A B oi the cylinder does not pass through the center C of the crank-shaft; or, in other words, when the center of the crank- pin d' is at its lowest position it does not lie on the center line AB oi the cylinders. Cylinders arranged in this manner are said to be offset. The principal object of oflfsetting the cylinders of an auto- mobile engine is to obtain a more nearly perpendicular pres- sure on the crank during the working stroke, and thus reduce the sidewise thrust of the piston against the cylinder wall and lessen the consequent wear. 37. Cylinders Cast in Pairs. — ^An external view of a four-cylinder four-cycle automobile engine having its cylinders cast in pairs is presented in Fig. 12, which shows the engine Digitized by Google 30 GASOLINE AUTOMOBILE ENGINES § 2 used on many Buick automobiles. A feature of this engine is that the inlet and exhaust valves are located in the cylinder heads and are operated from a single cam-shaft by means of rocker-arms and push rods. The cam-shaft is located on the right side of the engine, when viewed from the driver's seat ir the car. The carbureter a and the inlet and exhaust mani folds b and c, respectively, are located on the left side. The air-circulating fan d is driven from the crank-shaft by the belt e. Each cylinder block, or casting, /, containing two cylin- ders, is bolted to the crank-case g, and the whole is supported Fig. 12 on the frame of the car by the arms ft, two of which are located on each side of the engine. The crank-case is provided with two breathers for allowing hot gases to escape. 38. A view of the right side of the Buick engine, part of which is shown in section, is presented in Fig. 13. On this side of the engine is located the cam-shaft a, which is driven from the crank-shaft b by the helical gears c and d. The shaft Cf which drives the magneto and the water pimip, is rotated at crank-shaft speed by means of the helical gear /, which meshes with the gear d on the cam-shaft. The magneto, which Digitized by Google 81 Digitized by Google 32 GASOLINE AUTOMOBILE ENGINES § 2 is not shown in the illustration, is located near the center of the engine on the right side. The water pump is seen at g. The cooling water is circulated from the radiator through the pipe h to the pump and thence into the cylinder water-jackets i by way of the pipe /. From the water-jackets, it flows back into the radiator through the pipe k. The inlet valves / and exhaust valves m are located in the cylinder heads. The inlet valves / are arranged side by side in each pair of cylinders, with an exhaust valve m on each ade of them. The valves are assembled in cages n, which can be removed by imscrewing the caps o; the valves are operated by the rocker-arms p and the push rods q. The push rods are raised by the cams r on the cam-shaft, and their upward movement in turn raises one end of each rocker-arm. The other end of each rocker presses against the top of a valve stem, hence each upward movement of a push rod forces the corre- sponding valve open against the pressure of its spring. The valves in this engine are timed so as to give a firing order of 1-3-4-2. The crank-shaft 6 is of the three-bearing type; that is, it turns in a bearing ^ at each end and one in the middle. The crank-case is divided into two compartments. The lower oxnpartment t serves as an oil reservoir from which the lubri- cating oil is circulated throughout the oiling system by means of a gear-pump w, which is driven from the crank-shaft by means of bevel gears and a vertical shaft. The upper compartment v is the crank-case proper and contains oil troughs w into which the scoops X, on the lower ends of the connecting-rods, dip and gather up oil for lubricating the cylinders and connecting- rod bearings. In the broad flywheel ;v is a cone clutch that connects or disconnects the engine from the driving mechanism of the car when desired. The clutch consists of the cone 2, which is normally held against the inner conical surface of the fljrwheel by the spring a' and is faced with the leather b\ The cone z is coupled to the driving mechanism of the car, and the clutch is disengaged by compressing the spring a' by means of a foot-pedal, thus separating the outer surface of the cone from the inner surface of the flywheel. Digitized by Google §2 GASOLINE AUTOMOBILE ENGINES 33 The spark plugs in this engine are located along the side of the cylinders, as seen at c', A pointer d\ fixed to the rear cylinder, indicates by means of marks on the flywheel rim the time at which the valves should be opened and closed, and the positions of the dead center of the cranks. 39. Cylinders Cast En Bloc. — ^Fig. 14 is a view of the inlet side of the Chalmers "Thirty-six" motor, which is an example of a four-cylinder four-cycle engine having its cylinders cast en bloc. A front-end view of the same engine is shown in Digitized by Google 34 GASOLINE AUTOMOBILE ENGINES § 2 Fig. 15. The carbureter a is located on the right side of the engine and the magneto b and water pump c on the left side. In the end view, Fig. 15, is seen the arrangement of. the gears by means of which the cam-shaft and magneto shaft are driven. The diameter of the gear d on the cam-shaft is twice that of the gear e on the crank-shaft, and the diameter of the gear/ on the magneto shaft is the same as that of the gear e. This arrange- ment gives the gear ratios required to drive the cam-shaft at one-half crank-shaft speed, and the magneto shaft at crank- shaft speed. The gear g is an idler gear and is used simply to connect the gears d and e. It has no effect on the gear ratio but causes the cam-shaft to be rotated in the same direction as the crank- shaft. In some engines the crank- shaft gear meshes directly with the cam-shaft gear, and the two shafts rotate in opposite direc- tions. The cam-shaft may rotate in either direction, provided the cams are designed so that they will work properly in that direction. In this engine, the inlet valves ^°- '^ are located in the cylinder heads imder the caps fe, and are operated from the cam-shaft by means of the push rods i and the rocker-arms /; the exhaust valves are located on one side and are operated directly by the push rods k. The inlet manifold /, leading from the carbureter a to the intake passages, is on the right side of the engine, and the exhaust manifold w is on the left side. The carbureter employed on this engine is warmed by hot water from the cylinder jacket; the water flows through a jacket space around the carbureter, entering it by the pipe n and leaving by the pipe Of which leads into the cooling system near the pump. A breather pipe, which is also used as an oil funnel, is seen at p. The foot-pedal q operates the clutch, which is contained in the case r, and the levers s are part of the connections running from Digitized by Google Pig. 16 Digitized by VjOOQ IC 86 GASOLINE AUTOMOBILE ENGINES § 2 the hand spark lever on the steering column to the spark- timing device on the magneto. 40. A part longitudinal section of the Chalmers four- cylinder engine is presented in Fig. 18. The view shows at a the inside of the first cylinder and the location of the inlet valve by which opens downwards into the center of the combus- tion chamber. In the second cylinder, part of the exhaust valve chamber is cut away, exposing to view the exhaust valve c, which opens upwards into the side, x)r projecting part, of the combustion chamber. The spark plugs d are placed directly over the exhaust valves. The crank-shaft ^ is of the two-bearing type and is supported at its ends by the ball bearings /. A single cam-shaft g operates both inlet and exhaust valves, two of the gears by which it is driven from the crank-shaft being shown at h and i. The bottom of the crank-case contains four troughs ; into which' lubricating oil is pumped from the oil reservoir k. The ends / of the connecting-rods dip into these troughs and splash the oil over the interior of the engine, thus lubricating the moving parts. The fan pulley is seen at tn and the flywheel at n. TYPICAL SIX-CYLIKDEB ENGINES 4 41. Cylinders Cast Separately. — Six-cylinder four-cycle automobile engines usually have their cylinders cast in blocks of two or more, although in a few the cylinders are cast sepa- rately. An example of the latter method of construction is the Franklin six-cylinder air-cooled engine shown partly in side view and partly in section in Fig. 17. The distinguishing feature of this engine is that its cylinders are cooled by means of air- currents flowing over them instead of by means of the tisual water-jacket. The cylinders a are provided with flanges 6 that increase their radiating surface and make it possible for the cool air flowing around them to carry off enough heat to sufficiently cool the cylinders. Both the inlet valves and the exhaust valves are located in the cylinder heads, as shown in the first cylinder, in which c is the inlet valve and d the exhaust valve. The valves are Digitized by Google 97 222B— 11 Digitized by Google 38 GASOLINE AUTOMOBILE ENGINES § 2 operated from a single cam-shaft e by means of push rods / and rockers g. The cam-shaft is driven from the crank-shaft h by means of the helical gears i and /. A third helical gear k drives the magneto shaft / from the cam-shaft gear /. An oil pump m is located on the same side of the engine and receives its power from the cam-shaft through a vertical shaft n that is driven by helical gears, one of which is seen at o. By means of this pimip, the lubricating oil is piunped from the reservoir p through the lubricating system to the various bearing surfaces. A multiple disk clutch g, enclosed in the flywheel r, connects the engine crank-shaft with the driving mechanism of the car. The inlet manifold is seen at s and the exhaust manifold at t. The crank-shaft h is supported by seven bearings, one at each end of the engine and one between each two adjacent cylinders. 42. Cylinders Cast In Pairs and in Threes. — ^The most common method of grouping the cylinders of a six-cylinder four-cycle automobile engine is in blocks of two, as shown in Fig. 1. The advantage of this construction over that in which the cylinders are cast separately is that a shorter and more compact engine is obtained and a smaller number of crank- shaft bearings are necessary. On the other hand, as the number of cylinders in one block increases, the difficulty of making the casting also increases. Cylinders cast in blocks of two, or in pairs, are comparatively easy to make; hence, engines of this type have certain advantages, from the manufacturers' stand- point, over engines with all of the cylinders cast in one piece. However, the compactness and neat appearance of the six- cylinder engine with the cylinders cast en bloc, are advantages that are bringing this type of motor rapidly into use. 43. A number of six-cylinder engines are built with the cylinders grouped in two blocks having three cylinders in each block, as shown in Figs. 18 and 19. Fig. 18 is a right-hand side view of the Lozier "Light Six," and Fig. 19 is a left-hand side view of the same engine. The engine has a bore of 3f inches and a stroke of 5| inches and is rated at 36 horsepower. Thie two blocks are seen at a and 6, Fig. 18. The inlet and exhaust valves are located on this side ot the engine, the valve stems Digitized by Google 00 6 Digitized by Google 40 GASOLINE AUTOMOBILE ENGINES § 2 and springs being enclosed. The valves are operated from a single cam-shaft that is driven from the crank-shaft by means of gears contained in the casing c. The fuel enters the cylinders from the carbureter d by way of the intake manifold e, and the exhaust gases escape through the exhaust manifold /. At g is a sleeve that surrounds the exhaust pipe and is connected to the carbureter for the purpose of supplying warm air to aid in evaporating the gasoline. The djniamo h supplies electricity for the electric lights on the car, and the electric starting device i automatically cranks the engine when starting. The spark plugs ; are located over the inlet valves. The clutch and transmission gears are located in the casing k, which is rigidly bolted to the engine crank-case /, thus forming a imit power plant. The clutch is operated by the foot-pedal m and the transmission gears by the hand-lever w. The foot-pedal o and the hand-lever p are for operating the service and emergency brakes, respectively. The foot-pedal q is the accelerator pedal, which is used for opening the throttle valve in the carbureter by foot pressure. 44. The water piunp r and the magneto s are located on the left-hand side of the engine, as shown in Fig. 19. Both are driven by the shaft t, which in turn is driven from the crank- shaft through the gears contained in the casing c. The water circulation is from the ptmip r through the pipe u to each casting, thence to the radiator by way of the connection », and back to the pimip through a pipe not shown. The breather pipe w allows the escape of hot gases from the crank-case and affords a means of pouring oil into the oil reservoir in the bottom of the crank-case. An oil-level gauge is located at x. The power plant is supported in the frame of the car by the four arms y and z, two on each side. 45. Cylinders Cast En Bloc. — ^Fig. 20 shows the outside appearance of the Studebaker six-cylinder engine. All the cylinders are cast in one piece a and the valve stems and springs are completely enclosed, giving the engine a very compact and clean-cut appearance. All of the valves are located on the left side of the motor, which is the side shown, and the inlet valves Digitized by Google I Digitized by Google 42 GASOLINE AUTOMOBILE ENGINES § 2 are adjacent to each other. The spark plugs b are located over the inlet valves, and the priming cups c over the exhaust valves. The carbureter is on the right side of the engine and the exhaust pipe d is on the left: A feature of this engine is the location of the water pump e, which is placed at the forward end of the cylinders and pumps water into the cylinder jackets in line with the valves. The pump receives its power from a cross-shaft that is driven by a worm-gear from the engine crank-shaft. The magneto is also driven by this cross-shaft, and is located on the opposite side of the engine. The cooling water is returned to the radiator through the pipe /. The crank-case g is made Pig. 20 bottomless and a pressed-steel oil reservoir h containing lubri- cating oil is bolted to it. The amount of oil in the reservoir may be ascertained at any time by means of the gauge i. Oil is poured into the crank-case through the breather pipe ;'. The engine is supported in the frame of the car by means of four supports, two of which are located on each side, as shown at k and I. UNIT POWER PLANT 46. In general, there are two methods of placing the engine, clutch, and transmission gears in relation to each other in an automobile chassis. First, the transmission gears, and in some instances, also the clutch, may be entirely separate from the Digitized by Google §2 GASOLINE AUTOMOBILE ENGINES 43 engine and be either contained in a separate casing or form part of the rear axle; and second, the three units may be enclosed in a single rigid casing, forming the unit i>ower plant type of construction. In the first method, the change-speed gears are connected to the engine by a shaft fitted with either one or two universal joints to give flexibility and thus relieve the parts of the strej>ses that otherwise would be thrown on them in passing over rough, imeven roads. In the tmit power plant, the parts are held rigidly in alinement by means of the casing. 47. An example of a unit power plant is presented in Fig. 21, in which {a) is a side view and part longitudinal section and (jb) is a top view of the Model 31 imit power plant manufactured by the Northway Manufacturing Company. The transmission housing a is bolted to the engine casing 6 so as to form a single rigid casing in which the engine, clutch, and transmission are enclosed. The engine is of the six-cylinder type, with its cylinders cast in pairs, and all the valves c and d are located on the left side and operated from a single cam-shaft e, A feature of this engine is that the cam-shaft e and pump shaft/ are driven from the crank-shaft by means of a silent chain, represented by the dotted lines g. This aids in making the engine run quietly. The clutch is located inside of the flywheel h and is of the cone type. The chief advantages claimed for the imit power plant are that the imit casing keeps the oil in and the dust out and that every part is held in absolute and imdisturbed alinement imder all conditions. Another advantage is that it petmits the power plant to be assembled as a whole and put into position without fitting it into place. A disadvantage is that with the unit construction, it is sometimes diflScult to remove one part with- out first removing many other parts. ENGINE SUSPENSION 48. An automobile engine may be suspended from the frame of the car by either one of two methods, namely, by tliree-polnt suspension, or by four-i>olnt suspension. With the three- Digitized by Google 44 GASOLINE AUTOMOBILE ENGINES § 2 point method of support, the power plant is carried by two rigid supports at one end and by a single pivotal support at the other. In some cars the power plant is suspended in front from the main frame or the subframe by two arms, and in the rear from a cross-member of the frame by a single pivotal joint; in other cars the two supports are at the rear and the single support in front. For example, the unit power plant illustrated in Fig. 21 is suspended in this manner. The rear of the power plant is carried by two arms i and /, view (6), which rest on longitudinal members of the frame, and the forward end is carried by the support fe. The front sup- port fe is in the form of a bearing that is bolted to the cross- member of the frame and carries the forward end of the engine through the part /, which extends into k. The part / is free to turn in the support ky and hence any twisting motion that is given to the power plant through the arms i and ; does not tend to distort the engine and throw it out of alinement, but merely turns the entire power plant in the bearing k. In the four-point suspension, the engine or power plant is supported by the frame of the car at four points. Four arms or supports extend from the power plant casing or from the crank-case to the side members of the frame to which they are rigidly attached. The engine and transmission may each be supported or carried separately in their own casings, or they may be combined into a unit power plant and the whole carried at four points. A good example of four-point suspension is the engine shown in Fig. 12, which is carried on the side members of the frame by two arms h on each side of the crank-case. 49. Each method of supporting the power plant of an automobile has certain advantages peculiar to itself. The advantage claimed for the three-point suspension is that it prevents twisting stresses from being transferred from the frame of the car to the engine, thus throwing the moving parts out of alinement. On the other hand, it is claimed by the adherents of the four-point method of suspension that, although the three-point suspension is theoretically correct, from a practical standpoint the four-point suspension is the more satisfactory. Digitized by Google Digitized by Google a22B 12 Digitized by Google Digitized by Google Digitized by Google § 2 GASOLINE AUTOMOBILE ENGINES 45 The engine with four points of suspension is more stable and less inclined to rock under heavy loads tinder varying conditions. It is also claimed that with the four-point suspension, the engine is held rigid by means of its supports and the frame gives the desired flexibility. As a matter of fact, both methods of power plant suspension are used with success on all kinds of automobiles. 60. The two meth- ods of suspension can be compared by observ- ing the two views of Fig. 22. In (a) the engine a and the trans- mission b are located in separate casings, each casing being suspended from the frame by f our arms. In (6) the engine a and trans- mission b are enclosed in a single casing and the whole is suspended from the frame by the two arms c in the front and the joint d in the rear. The pivotal joint d rests on a cross- member e of the frame. It must not be iniagined that a three- ^'^' ^ point suspension can be applied only to a unit power plant; the engine alone is often suspended from the frame on three points and the transmission carried as a separate tmit. In other words, the term three-point suspension refers to the number of points at which the engine or power plant is sup- ported, regardless of the m^iner in which the engine is encased. Digitized by Google 46 GASOLINE AUTOMOBILE ENGINES §2 TWO-CYCIiB ENGINES ABRANGEMENT OF TWO-CTCLE ENGINE CTLINDEB8 51, A two-cylinder two-cycle engine ustially has its cylin- ders arranged side by side, as in Fig. 23, and the cranks at an angle of 180® apart, or directly opposite each other. In other words, while one piston is moving downwards on its imptilse stroke the other is moving upwards on its compression stroke, so that the explosions alternate, occurring first in one cylinder i M and then in the other. By this arrangement an impulse occurs every half revolution, and the moving parts are well balanced. 52. Three-cylinder two- cycle engines are generally arranged as shown in Fig. 24. The cranks are 120° apart, that is, they are arranged at equal distances aroimd the crank-shaft, so that the impulses occur every third of a revolution. With this arrangement and starting with the first cylinder, an explosion occurs first in cylinder 1 , then in cylinder 5, ^'°- ^ and lastly in cylinder 2, or, in other words, the order of firing in such an engine is 1-3-2. 53. In four-cylinder two-cycle engines all the cylinders are generally in Une on one side of the crank-shaft, as seen in Fig. 26. The cranks are arranged 90° apart, hence in such an engine four impulses occur at equal time intervals for each revolution of the crank-shaft. In order to balance each other and thus prevent any great vibration, the cranks are arranged Digitized by Google Fig. 24 Fig. 26 47 Digitized by VjOOQ IC 48 GASOLINE AUTOMOBILE ENGINES §2 so that cranks 1 and 2 are directly opposite each other and cranks S and 4 are directly opposite each other, as seen in the illustration. Beginning with cylinder 1, an explosion occurs first in that cylinder, then in cylinder ^, then in cylinder 2^ and finally in cylinder 5; or, in other words, the firing order is l-4r-2-3. The arrows in the illustration show the direction in which the different pistons are moving, and the numbers at the top indicate the usual numbering of the cylinders, No. 1 being at the front end of the engine and No. 4 at the rear. EXAMPLES OF TWO-CTCLE AUTOMOBILE ENGINES 54. Application of Two-Cycle Principle. — ^The use of the two-cycle automobile engine is practically confined to the high-wheel type of motor vehicle known as the motor buggy , so named from its resemblance to the ordinary horse-drawn buggy, and to a few makes of motor trucks, or commercial vehicles. The two-cycle engine is not used to any extent in automobile practice, principally because it is not as economical as the four-cycle engine in the use of fuel and oil, and because its construction is not such as to readily adapt it to high speeds. In this type of engine the cylinder is not completely cleared of exhaust gases at the end of the working stroke, so that the burned gases are liable to mix with the fresh charge and make a poor combustible mixture. This is. most likely to occur when miming at the high speeds required in pleasure cars. Various types of two-cycle engines have been designed from time to time for use on pleasure cars, and although these have their good feattures, practically all have had to give way to the more popular four-cycle engine. 55. Two-Cylinder Two-Cycle Engine. — ^An external view of a two-cylinder two-cycle engine of the two-port type, used on the Duryea motor buggy, is shown in Fig. 26. The cylinders a and b are placed side by side on the same side of the crank-shaft c, and the flywheel d is placed between them. The inlet ports leading into the crank-cases are located at e and Digitized by Google §2 GASOLINE AUTOMOBILE ENGINES 49 the exhaust ports at / on the opposite side of the cylinders. Spark phigs g are screwed into the cylinder heads for the pur- pose of igniting the charge at the proper time. This engine is provided with means for turning the flywheel over from the seat when starting. The arm A, which is free to rotate about the crank-shaft, is provided with a pawl i that can be made to engage in notches / placed at intervals around the flywheel rim. A wire and rope connection extends from the arm and pawl to a handle at the driver*s seat. The engine can be turned over by pulling on this connec- tion, thus engaging the pawl in one of the notches and rotating the flywheel. 56. A cross-sec- tional view of one of the cylinders of the engine illustrated in Fig. 26 is seen in Fig. 27, which shows the piston at the bot- tom of its stroke with the transfer port a and the exhaust port b open. The charge enters the crank-case Pig. 26 through the crank-case inlet port c. This port is controlled by a check-valve d, which prevents the combustible mixture from flowing back into the inlet pipe or the carbureter when the pis- ton is on its downward stroke. Normally the valve is held to its seat by a light spring, but when a vacuimi is formed in the crank-case by the upward stroke of the piston, the valve opens inwards and allows the mixture to enter the crank-case. The deflector on the piston face is shown at e, and the spark plug at/. 67. The arrangement of the cranks of the engine illustrated in Fig. 26 is shown in Fig. 28. This illustration shows the Digitized by Google 60 GASOLINE AUTOMOBILE ENGINES § 2 pistons a and b connected to the cranks c and d by the con- necting-rods e and /, respect- ively. The cranks are located on opposite sides of the crank-shaft so that the explo- sions in the cylinders will alternate, as is the usual cus- tom in two-cylinder two-cycle engines. Each crank is pro- vided with a counterweight g that serves to balance the moving parts of the engine. The crank-shaft h rotates in the roller bearings i, which are supported by the frame of the car. The rollers / drive the road wheels of the motor buggy. 58. Detailed views of one of the cylinders removed from the engine illustrated in ^'*'- ^^ Fig. 26 are shown in Fig. 29. In view (a) is seen the inlet side of the cylinder with the inlet port at a, and in view (6) is seen the exhaust side with the Pig. 28 exhaust port at b. Copper spines for the purpose of carry- ing off the excess heat and thus preventing damage from Digitized by Google § 2 GASOLINE AUTOMOBILE ENGINES 51 over-heating are bound to the outside of the cylinders, as seen in view (6) These spines, or projections, serve the same ptirpose W Pig. 29 fb) as the cooling water in the engines previously described. 69. Three-Cylinder Two-Cycle Engine. — ^The Chase three-cylinder two-cycle en r^ -McIj is of the three-port type, is illustrated in Figs. 30 ai < Fig. 30 shows the engine Digitized by Google 52 GASOLINE AUTOMOBILE ENGINES § 2 mounted on the frame of the car with part of the hood a and mud pan 6 cut away, exposing to view the intake side of the motor. The carbureter is located at c and is connected to the cylinders d by the intake manifold e^ through which the charge is drawn into the crank-case /. At g is the exhaust manifold, by means of which the exhaust gases escape into the exhaust pipe and thence to the atmosphere. The crank-shaft h extends lengthwise through the crank- case and is provided with the starting crank / for the purpose of turning over, or cranking, the engine when starting. This engine is of the air-cooled type, that is, the cylinders are cooled by currents of air flowing around and over them. Flanges are cast integral with the cylinder walls to increase their radiating surface and better to enable the air to carry away the heat. 60. Fig. 31 shows a cross- sectional view of one of the cyl- inders of the engine illustrated in Fig. 30. As far as possible the same parts in the two illus- trations are lettered the same. The piston fe, Fig. 31, is seen at the bottom of its stroke with ^*^'^^ the crank-case inlet port I closed and the transfer port m and the exhaust port n open. The operation of this engine is identical with that of the three- port engine shown in Fig. 5. A charge flows into the crank- case / on the upward stroke of the piston when the inlet port / is opened, and is slightly compressed on the downward stroke, at the end of which the transfer port m is uncovered and the mixture rushes into the combustion chamber through the pas- sage o. On the next upward stroke of the piston the charge Digitized by Google § 2 GASOLINE AUTOMOBILE ENGINES 53 is compressed in the cylinder, after which it is ignited and the resulting expansion drives the piston downwards again, a new charge being precompressed in the crank-case at the same time. The exhaust gases escape through the port n at the end of each down stroke. A feature of this engine is the use of a baf&e plate p in the combustion chamber. One of these plates is located on the exhaust side of each cylinder, and is for the purpose of preventing the fresh charge in the combustion chamber from escaping by way of exhaust port n at the begin- ning of the compression stroke. 232B— 12 Digitized by Google Digitized by VjOOQ IC GASOLINE AUTOMOBILE ENGINES (PART 2) DETAILS OF CONSTRUCTION AUTOMOBIIiE-EINGINE CYUNBERS WATER-JACKETED CYLIXDEBS !• Cylinders with Integral Heads and Jackets. — ^The almost universal practice in water-jacketed automobile-engine construction is to cast the cylinder body, the head, and the water-jacket in one piece. In the earlier types of engines it was common practice to make the cylinder head a separate casting and bolt it on to the cylinder proper, but at the present time only a very few ntiakers of automobile engines adhere to this custom. The chief object of casting the cylinder, the head, and the jacket in one piece is to avoid packed joints between the cylinder and the head and between the cylinder and the water-jacket. 2* The form of an automobile-engine cylinder depends on the location and arrangemait of the inlet and exhaust valves. Classified according to the valve location, there are three general types of cylinders, namely, the l-head, the L-head, and the valve- in^he-head. 3. In engines of the T-liead type, the inlet and exhaust valves are located on opposite sides of the cylinder, giving it, roughly, the appearance of the letter T. This type of cylinder oorrmaHTBD by intirnationai. tbxtbook company, all iiiaHTs rbmrvbd S3 Digitized by Google GASOLINE AUTOMOBILE ENGINES §3 is illiistrated in Fig. 1, which shows a cross-sectional view of one of the cylinders of the National, 4J''X6", four-cycle engine. The combustion chamber ti and the inlet and exhaust passages 6 are surrounded by the water passages c. This inlet and exhaust chambers are made alike, and the valves are interchangeable. The intake pipe is connected to the opening shown at d and the exhaust pipe to that shown at e, chambers being cored from these Pig. 1 openings to the valves, as indicated by the dotted lines. The opening on top of the cylinder at / permits placing the inlet valve in position or withdrawing it, and also gives access to it; a corresponding opening g on the opposite side is provided for the same purposes for the exhaust valve. The openings are ordinarily closed by means of plugs screwed into them. The National engine is provided with two separate sets of spark plugs, and one of these is screwed into the center of each of the Digitized by Google §3 GASOLINE AUTOMOBILE ENGINES plugs, or caps, that dose the openings/ and g. The opening h is for a priming cup, and the openings i are provided to accom- modate the valve-stem guides. 4. When the inlet and exhaust valves are placed together on the same side of the cylinder and are operated by the same cam-shaft, the cylinders are said to be of the L-head type. This tjrpe of cylinder is illustrated in Fig. 2, which shows two views of one of the cylinders used in the Rambler four-cylinder, four-cycle engine. View (a) is a cross-section of the cylinder, and view (fe), a side view and section through the valve cham- <^) Fig. 2 bers. A water-jacket a surrounds the upper part of the cylin- der b and the valve chambers c and d. Valve-stem guides e are cast integral with the valve chambers, and the valves are made interchangeable. The valves may be removed by unscrewing the plugs, or caps, / and g. The spark plug is located over the inlet valve in the center of the cap /. The cooling water escapes from the water-jacket through the opening h. The opening i, which, ordinarily, is closed by a plug, gives access to the inside of the cylinder. In engines of this type, it is common practice to place the inlet valves of adjacent cylinders next to each other. Digitized by Google GASOLINE AUTOMOBILE ENGINES §3 5. Yalve-in-tlie-liead eiiglnes» with cylinder, head, and water-jacket cast in one piece, usually embody some type of valve cage containing the valve seat and valve-stem guides. The valve-in-the-head construction is illustrated in Fig. 3, which shows a longitudinal section of a pair of cylinders of the Buick engine. Each cage consists of a cylindrical shell a that fits in a Pig. 3 bored-out pocket in the cyUnder head and has a large opening cut through the shell to register with the inlet or the exhaust passage The cage is forced against a shoulder 6 at the lower end of the pocket by means of an annular nut c screwed into the outer threaded end of the pocket. The valve-stem guide d is supported within the cage by means of a spider e, and the valve is held to its seat by a spring /, whieh is held in compression Digitized by Google §3 GASOLINE AUTOMOBILE ENGINES 6 between the spring seats g and h. The seat g is prevented from being forced oflE the valve stem by the cotter i. The valves are opened by pressure exerted on the upper aids of the valve stems. The two inlet valves ; and k are located next to each other at the center of the twin casting, and the two exhaust valves are located at the ends of the casting, one being shown at /. This arrangement has the advantage that a single con- nection from the intake manifold is sufficient for both cylinders. A single continuous water-jacket m surrounds the entire casting, and the spark plugs are located on one side, immediately below the valve cages. 6. The cylinders shown in Fig. 3 have the valves arranged vertically in the cylinder heads. Another type of valve-in- the-head engine, in which the valves are incUned, is illustrated in Fig. 4, which shows a cross-sectional view of one of the cylinders (rf the engine used in the Stoddard-Dayton, model 58, car. In this engine, the valves are located on opposite sides of the cylinder and they are operated from separate cam-shafts by means of push rods and rocker-arms. The charge enters the inlet valve cage a through an opening at b, and the exhaust gases escape from the exhaust-valve cage c through an opening d. The valve cages a and b are indined at an angle to the ver- tical and have between them a jacket space e. A water-jacket / ^'^"^ surrounds the outside of the valve chambers, the combustion chamber g, and the upper part of the cylinder proper. 7. The chief advantage of having the valves located in the cylinder head is that a more nearly ideal combustion cham- ber may be had with this design than with any other. The ideal combustion chamber is spherical in form, for the reason Digitized by Google 6 GASOLINE AUTOMOBILE ENGINES § 3 that a sphere has the least surface area for its cubical contents; hence, in such a combustion chamber, the loss of heat through the walls is least. Among the valve-in-the-head cylinders, those having the valves set at an angk more nearly approach this form of combustion chamber. However, motors with the valves located in the cylinder head have the disadvantage of reqtdring the use of a complicated and more or less noisy valve-actuating mechamsm. This is a very important con- sideration, especially in high-speed engines. T-head and L-head engines have the advantage of simple valve-operating mechanism. The valves are more easily removed than in the valve-in-the-head type, and the spark plugs can be located in the inlet valve chamber, where a fresh charge is always found* On accoimt of this advantageous location of the spark plugs, T-head and L-head motors can be run at a lower speed under no load than can an engine with the valves in the head. Because of these practical considera- tions, most manufacturers make use of either the T-head or the L-head motor for ordinary pleasure car service; valve-in-the- head engines are used extensively in racing cars. 8. A t3rpe of engine cylinder in which the inlet valve is located in the head and the exhaust valve at one side is some- times used. The appearance of the engine is similar to that of the regular L-head motor, except for the valve-actuating mechanism. The inlet valve is operated by means of a push- rod and a rocker-arm, and the exhaust valve, by means of a valve tappet that operates directly on the valve stem. In some Chalmers engines, which use this type of cylinder, both valves are operated from a single cam-shaft. The spark plug is located over the exhaust valve. This form of cylinder pro- vides a better shaped combustion chamber than is provided by the T-head cylinder, and at the same time it allows large inlet and exhaust passages, as these may be placed on opposite sides of the engine. This is an advantage over the regular L-head cylinder, in which the valve passages are more restricted on account of all the valves being on the same side. On the other hand, this construction has the disadvantage of a Digitized by Google § 3 GASOLINE AUTOMOBILE ENGINES 7 somewhat complicated valve-operating mechanism. Also, the spark plug is located in the exhaust-valve chamber, where a small quantity of burned gases is liable to become mixed with the fresh charge and thus make the mixture more difficult to ignite. 9. Cylinders With Separate Heads. — In the early auto- mobile engines having cylinder heads cast separately, the upper end of the cylinder and the water-jack- eted head were pro- vided with passages for the circulation of the cooling water. The openings in the head and the upper end of the cylinders were made to match, and the joints were made tight by means of gaskets that con- tained holes corre- sponding to the water passages. The difficulty of keeping these narrow gaskets in place and of pre- venting the joint from leaking has led to the abandonment of this practice in engine design, except in a few special cases. 10. In the Knox ^'^'^ engine, as shown in Fig. 6, the cored openings for commimica- tion between the water-jacket and the head are omitted and an outside connection is used instead. The detachable head a is held in place by four long stud bdts b that pass through lugs cast on the cylinder head, as Digitized by Google 8 GASOLINE AUTOMOBILE ENGINES § 3 shown. Communication between the head a and the water- jacket c of the cylinder is afforded by a separate detachable U-shaped hollow fitting d held in place by the yoke e^ which also serves to hold in place the return-water manifold or pipe connection ; leading to the radiator. One end of the fitting d fits in the opening / leading to the cylinder water-jacket, and the other end fits in the hole g of the cylinder head. A hori- zontal division plate, which is cast in the head, divides the water space thereof into two parts. The circulating water from the cylinder jacket enters the lower space through the opening g and passes out into the return-water manifold through the open- ing h. Water from the supply manifold enters the jacket at i. On the bottom of the head there is a. machined concentric tongue that fits into a corresponding machined groove in the upper end of the cylinder casting, and in the groove is placed a copper-asbestos gasket k that serves to make a tight joint when the nuts on the stud bolts 6 are screwed down. The manufacturers daim that, among other advantages of this construction, the machining of the whole bottom of the head contributes to the smooth running of multicylinder engines, because it insures combustion spaces of uniform capacity and lessens the liabihty to backfiring by eliminating the carbon- collecting projections, sharp points, rough edges, or uneven surfaces common to tmmachined castings. Being located in the head, as shown, the inlet and exhaust valves that control the flow of the fresh charge and exhaust gases through pas- sages cored in the head are surrounded by the circulating water and are thus kept cool. 11. Another example of a detachable water-jacketed cylin- der head is illustrated in Fig. 6, which shows several views of the cylinders of the Ford, model T, engine. A side and part sectional view of the cylinders is shown in (a); a top view, in (6) ; and a bottom view of the head and a top view of the cylinders with the head removed, in (c) and (d), respectively. Each cylinder is of the L-head type, and the four cylinders are cast en bloc. The cylinder head a is a single casting that is bolted to the cylinders by fifteen capscrews b. When the head Digitized by Google §3 GASOLINE AUTOMOBILE ENGINES 9 i ^_^ CD o fa) is removed by tmscrewing these capscrews, the tops of the valves c and the tops of the pistons d, are exposed, thus facili- tating the processes of removing deposits of carbon, regrinding the valves, and re- moving the pistons and comiecting-rods. As shown by the sec- tional view, the valve stans are kept cool by the water circula- ting in the jacket e from which the water passes into the head through two passages /, one at each end of the cyl- inder casting, corre- sponding passages g being formed in the head, as shown by the bottom view of this part. The water that enters the water-jacket through the pipe h passes out to the radiator through the pipe attached to the top of the head, as shown. The spark plugs / are screwed into the openings k, so as to project into the combustion chambers / formed in the head. A copper-and-asbestos gasket is used between the •^ y^ O O O N. ^ ' t0o:aQy (d) Pig. 0 Digitized by Google 10 GASOLINE AUTOMOBILE ENGINES § 3 cylinders and the head in order to form a tight joint. The gasket is comparatively wide and is not liable to be blown out on account of the cylinders being cast en bloc. A special advantage of separate cylinder heads is that they allow a boring tool to be used to the best advantage and thus facilitate the boring of the cylinders in their manufacture. However, their use in automobile engine construction is almost entirely confined to the Knox and Ford engines. 12. Cylinders With Separate Water- Jackets. — ^The water-jacket that surroimds the cylinder of an automobile engine is necessary in order to prevent the damage to piston and cylinder that would otherwise result from burning the oil used for lubricating them. Great care must be taken to select lilbricating oils that will stand even as high temperatures as those reached in water-cooled cylinder walls. With such inflammable fuel as gasoline, it is necessary to keep the com- bustion chamber, the piston head, and the valves reasonably cool in order to avoid premature explosions due to hot cylinder walls. These walls are made hot by the high compression pressures commonly employed with the high-speed, or auto- mobile, type of engine, as well as by the heat of combtistion. 13. In the majority of automobile engines, the water- jackets are cast integral with the cylinders, as is shown in Figs. 1 to 6. However, in a few cases, separate water-jackets made of sheet metal are successfully used. Examples of such jackets are to be foxmd in the engines of the Cadillac and Chad- wick cars. These jackets are lighter than those integrally cast, because they can be made thinner, and they are not so liable to be injxired by a freezing of the cooling water. Another advantage of such jackets is that they can be readily cleaned when scale deposits accumulate in them. 14. A cylinder of the Cadillac engine is shown in Fig. 7, which serves to illustrate the separate water-jacket. This engine is of the L-head type, with all the valves on the right side of the engine, the cylinders being cast separately. The water-jacket a, which surroimds the cylinder fc, is made of spun Digitized by Google § 3 GASOLINE AUTOMOBILE ENGINES 11 copper. The lower end of the jacket is pressed over a flange c that is cast on the cylinder, and a steel ring d is forced over the copper, thus clamping the jacket into position and making a tight joint. The cylinder head e, con- taining the valve chamber, is secured to the top of the cyl- inder by a right-and- left threaded nipple/. The top of the copper jacket is clamped between the cylinder head and the top of the cylinder at g and h, thus forming a tight joint. The valve chamber i is surrounded by water passages ;, which are cast integral with the cylinder head. The piston is shown at k. In case of injury to any part of a cylin- der of this form, as for instance to the head, the particular part damaged can be replaced at the factory without discarding the entire cylinder. In the six-cylinder engines of the Chadwick car, each pair of cylinders is sturoimded by a separate copper water-jacket. AIR-COOLED CTLINDERS 15. The internal construction of an air-cooled cylinder is the same as that of a water-cooled cylinder; also, the arrange- ment of the valves and other mechanism is similar. The external surface of an air-cooled cylinder, however, is extended, or increased, by various means, usually by the use of thin Digitized by Google 12 GASOLINE AUTOMOBILE ENGINES §3 heat-radiating flanges, or ribs, cast integral with the cylinder walls or fitted to them. These ribs, or flanges, serve to conduct the heat from the cylinder walls, the heat being absorbed and carried away by the air that comes in contact with the flanges. (b) W Fig. 8 In some of the earlier air-cooled engines, the cylinders were provided with pins, or studs, radiating from the outer surface of the casting. These studs, which were screwed into the Digitized by Google § 3 GASOLINE AUTOMOBILE ENGINES 13 cylinder walls were sometimes threaded from end to end in CMxler to provide a greater heat-radiating surface. 16. The best-known example of the air-cooled cylinder is that used on the Franklin automobile, which is practically the only American pleasure car propelled by an air-cooled engine. Two of these cylinders are illustrated in Pig. 8, a sectional view of one and an external view of the other being shown in (a) and a top view of one of these cylinders in (b). Like parts are let- tered the same in each view. A large heat-radiating surface is obtained by the use of vertical steel flanges a that are cast in the wall 6 of the cylinder. The flanges are spaced about i inch apart around the entire outer circumference of the cylinder and project radially outwards a distance of about 1 inch. The average length of these flanges is 8 inches. A cylindrical air jacket c surrounds each cylinder and, with the cylinder wall, it forms an air-tight passage through which the cooling air is drawn. The air is thus brought into close contact with the flanges, which conduct the heat from the cylinder walls. The air jackets t: are set in a horizontal metal deck d at the shoulder ^. This deck forms, with the engine hood and the dash, two sep- arate compartments, one below and one above. Air drawn from one compartment to the other must flow through the jacket c and thus come in contact with the flanges a. The cylinders shown in Fig. 8 are of the valve-in-the-head type. The valves/ and g open downwards into the head of the cylinder and are operated by push rods and rocker-arms. The valve seats are cast integral with the cylinder head; that is, no valve cages are used. 17. In the Chase two-cycle engine cylinder, the cooling flanges are cast integral with the cylinder walls and encircle the cylinder, being radially arranged on top. This engine is used principally on motor trucks. A large radiating surface is obtained in the Duryea two- cycle engine by fastening copper spines to the cylinders in the manner shown in Fig. 9. The cylinder is finished inside and outside. On the outside, the cylinder surface is deeply grooved. One of these spiral grooves is wider than the other and is intended Digitized by Google 14 GASOLINE AUTOMOBILE ENGINES §3 to receive the copper spines a. Both add much to the stiff- cylinder wall and, without making it heavy, insure al form. At the head of the cylinder is a small dch the end of a steel wire is hooked, the other end ed as shown in Fig. 9 (6), which indicates how the )ears after the spines are boimd in place, the plain, cylinder being shown in Fig. 9 (a). The copper r inch wide, iV inch thick, and about 4 or 5 inches long. They are doubled at the middle to fit the groove into which they are forced and stand with both ends project- ing, each projection being 2 or 2i inches long. The steel wire is tightly drawn to bind them in place. When applied, this wire is heated, and ^ ^ ^^ as it cools it shrinks and gnps the copper still i3 also of such quality that it does not expand is much as does the cylinder; therefore, the higher ture the tighter it binds. There is no tendency of to expand away from the cylinder. The spines spokes of a wheel, and thus allow ample space for irculate to the bottom of the grooves. The extra self allows much additional surface to be reached The spines are more or less irregular, and thus offer a variety of paths to the air flowing around them. In addition to this, copper has the advantage of being a good con- ductor of heat and therefore the spines form an efficient radi- ating siuface. The two-cycle engine cylinder is well adapted to air cooling because the exhaust gases do not heat the head, but pass out at a point farthest from the head, which is also cooled from the inside by each new charge thrown against it. The head has no valve chambers or mechanism to prevent free access of air to the outside. Digitized by Google § 3 GASOLINE AUTOMOBILE ENGINES 15 CRANK-CASES 18« General Construction. — ^The casing, or housing, of an automobile engine that encloses the cranks and crank- shaft, and, frequently, other moving parts as well, is called the crank-case. Besides forming a housing for most of the working parts, it also serves as a frame, or bed, that supports the crank-shaft and cylinders; and, usually, the lower part serves as a receptacle for the oil used in the lubrication of the - Fig. 10 engine. Crank-cases are generally cast of altmiinimi or an alloy of alimiintim, although in rare cases manganese bronze, malleable iron, or cast iron is employed. Aluminimi is used on acxxamt of its light weight in comparison with its strength. The size of a crank-case depends entirely on the design of the engine, but in any event it must be large enough to allow the cranks to rotate freely within it and strong enough to support the cylinders and crank-shaft. 222B— 13 Digitized by Google 16 GASOLINE AUTOMOBILE ENGINES §3 Crank-cases are usually divided horizontally into two halves, which are bolted together. However, they are sometimes divided vertically, or they are made in single castings provided with openings for the connecting-rods and for inspection pur- poses. The type last named is known as the barrel type. 19. Typical Crajik-Cases. — A very common type of automobile-engine crank-case is that in which the case is divided horizontally into two halves and the crank-shaft bearings are supported entirely from the upper half. This type of crank- case is illustrated in Fig. 10, which shows the upper and lower parts of the crank-case used on the Premier six-cylinder engine. In (a) is shown a view of the upper half, such as would be obtained by a person Ijring on his back beneath the engine and looking upwards after the lower half is removed. In (b) is shown a top view of the lower half of the crank-case. There are four crank-shaft bearings a in this case. The lower half of each bearing is a cap held in place by capscrews 6, which are prevented from turning by keepers c; the capscrews are screwed into the supports d. Movement of the keepers c is prevented by pins e that extend through the keepers and have cotter pins passed through them. The object of the keepers is to prevent the capscrews from turning under the influence df vibration. The connecting-rod bearing caps / are fastened in the same manner. The engine is of the T-head cylinder type, the valves being operated from cam shafts g and fe, which are located on opposite sides of the crank-shaft. The lower half of the crank-case is attached to the upper half by means of bolts that pass through the holes t, and the entire case is supported from the frame of the automobile by the arms / and k. The lower half is provided with the oil troughs /, into which the ends of the connecting-rods dip in order to lubricate the moving parts of the engine. The bot- tom m of the case, beneath the oil troughs, is used as an oil well, or reservoir. In many cases the oil reservoir is a separate casting bolted to the lower half of the crank-case, and in a few instances the lower crank-case is made of pressed steel. Sometimes the Digitized by Google §3 GASOLINE AUTOMOBILE ENGINES 17 troughs are made of sheet metal and in- serted into the lower half of the crank-case. Some crank-cases are made with an enlarged extension on one end, which exten- sion encloses the fly- wheel. 20« An example of a crank-case divi- ded horizontally, but having its supports attached to the lower half, is found on the Alco car. An exter- nal view of this crank- case is shown in Pig. 11. The upper and lower halves are held together by bolts a, and the entire crank-case is sup- ported by the arms 6, which are cast integ- ral with the lower half c. These arms are connected on each side by a web d that serves to stiffen them. This web also forms a support for the engine auxiliaries, such as the magneto and the pump, and acts as a pan to exclude dirt Digitized by Google 18 GASOLINE AUTOMOBILE ENGINES § 3 from below. The crank-shaft bearings, which are in line with the -division line of the case, are supported directly by the lower half. The flywheel and the dutdh are enclosed within the enlarged part e. 21. Another example of a crank-case that is supported by its lower half is illustrated in Fig. 12, which shows a top view of the bottom half of the crank-case used on the Ford, model T, automobile. The crank-shaft bearings are carried by the upper half of the case, which is of cast iron and is cast integral with the foxir cylinders. The lower half is of pressed steel and is bolted to the upper half. An inspection plate a is bolted to the bottom half and can be removed for inspection purposes. Pig. 12 The rear end h encloses the flywheel and transmission gears and is supported by two arms c that are fastened to the case. The front end is supported at a single point d, thus forming the three-point suspension method of support. 22. A crank-case made of a angle casting and provided with an opening for inspection is illustrated in Fig. 13, which shows the crank-case of the Rambler 38-horsepower, foiu:- cylinder engine. In this case, the opening is in the side, and it is ordinarily closed by means of a cover fastened on with capscrews. The interior of the case is divided into two parts by a partition a that supports the center bearing of the three- bearing crank-shaft. The end bearings are located at the ends of the case. In this engine, all the valves are located on the Digitized by Google § 3 GASOLINE AUTOMOBILE ENGINES 19 same side, the valve-lifter guides being shown at b and the single cam-shaft at c. In some crank-cases of this type, for instance, in that used on the Chalmers '*36*' car, the opening is located at the bottom and the cover is used as an oil reservoir. The crank-case is made of a single casting in this instance also. The advantage of this construction is that it provides a very rigid crank-case, and hence a good support for the engine. 23. A vertically divided crank-case, such as is used on the Winton six-cylinder engine, is illustrated in Fig. 14. This Fig. 13 case, which is made of alimiinum, is divided into two halves, but the dividing line is vertical and forms right and left halves, instead of the common upper and lower halves. The crank- shaft bearings a are mounted in the right half of the case, making it possible to remove the left half and thus expose the entire crank-shaft to view without interfering with the adjustment of any of the bearings. Shallow compartments, or troughs, b are located beneath each connecting-rod. They contain oil into which the ends of the connecting-rods dip. Drain holes c serve as overflows that prevent too high an oil level in each Digitized by Google 20 GASOLINE AUTOMOBILE ENGINES § 3 trough. The left half of the crank-case, not shown, is secured to the right half by means of capscrews that are screwed into the holes d. The removable half is provided with three hand- holes that permit inspection without removing the entire half. The cylinders of this engine are of the L-head type, all of the valves being operated from a single cam-shaft e. 24. The crank-case of a two-cycle engine must be air- tight in order that the fresh charge can be compressed in it before being admitted into the cylinder. There is liability of leakage through the crank-shaft bearings, and to prevent this, these bearings should be of suflSdent diameter and length Fig. U so that they will not wear out rapidly. Occasionally, two-cycle engines are provided with stuffing boxes on one or both ends of the crank-case bearings, and sometimes special forms of bushings are used with a fair degree of success to prevent leak- age. In three-port, two-cycle engines, the piston is provided with a piston ring at its lower end to prevent the gases from leaking back past the piston into the inlet port. In multiple-cylinder, two-cycle engines, it is important that one crank-case should not leak into the other; otherwise, there would be no crank-case compression. With removable cylin- der heads, such a condition can be detected by removing the heads and noting the velocity with which the gas or the air Digitized by Google §3 GASOLINE AUTOMOBILE ENGINES 21 enters the combustion chamber through the passover port when the engine is turned over. The crank-case of a two-cycle engine must be as small as possible, so that the required compression of the fresh charge may be obtained. The connecting-rod is usually made as short as possible to attain this object, and in some cases the vdume of the crank-case has been decreased by providing the crank-shaft with disks instead of the usual crank-arms. The disks occupy more space than the crank-arms in the crank-case, and hence decrease the volume. They thereby increase the ratio between the voltune of the case when the piston is at the top of the stroke and the volume when the piston is at the bot- tom of its stroke, and, consequently, cause a greater degree of crank-case compression. 25. Craiik-Caae Breathers. — ^The crank-cases of four- cycle engines are provided with one or more openings to which are attached pipes, called breathers, that allow the escape of air and hot gases. With the four-cycle engine, an air-tight crank-case would not be advantageous, because where the hot gases leak past the piston rings into the crank-case, there would be a tendency to overheat the bearings and to bum the oil, and through imperfect lubrication rapid wear of the engine would result. The breathers prevent this by allowing these hot gases to escape. In addition to this, the pressure in a closed crank-case of a multiple-cylinder engine varies because of the movements of the reciprocating parts; hence, another use of the breather is to relieve this pressure variation and keep it the same at aU tiunes. Varying pressures in the crank- case might interfere with the proper working of the lubricating sjTstem by forcing the oil out of the crank-case through the joints or bearings. Crank-case breathers usually serve the purpose of oil filling tubes, through which the lubricating oil is poured into the lower half of the case. 26. Breathers are usually located in the upper part of the crank-case and are frequently placed on the supporting arms. Occasionally, they are cast integral with the case, but more often they are separate pipes bolted on. Digitized by Google 22 Digitized by VjOOQ IC § 3 GASOLINE AUTOMOBILE ENGINES 23 An example of a breather pipe cast integral with one of the sui>porting arms of the engine is shown in Fig. 15 (a). The web a, which is cast integral with the pipe 6, carries a boss c. The cover d is supported by a stem e that fits in a hole in the boss. The lower end of the stem e is slotted, and the two halves thus formed have a tendency to spring apart and hence hold the cover in place. The air and hot gases escape between the edge of the cover and the top of the pipe, as shown by the arrows. The breather is provided with baffle plates / that are inclined downwards to prevent the escape of oil with the air. The oil globules are collected on these plates and rettuned to the oil reservoir in the bottom of the crank-case. The dome- like cover also serves to prevent the escape of oil. The breather communicates directly with the oil reservoir and is provided with a screen at g for cleaning the oil as it is poured in. The oil reservoir can be filled by simply removing the cover. 27. Another type of crank-case breather, in which the pipe is bolted to the crank-case by capscrews, is shown in Fig. 15 (6). The breather consists of an outer casting a and an inner tube 6, which is screwed into a partition c in the outer port. The part a is secured to the side of the crank-case d by means of six cap- screws, one of which is visible at e. It is provided with a cover/ that is supported by three extensions of the casting, as shown at g, thus allowing air and hot gases to escape between the cover and top of the breather. The outer part of the breather is formed into a lip A, into which oil may be poured. The outer casting a is in communication with the crank-case proper, and the inner tube 6 opens into the oil reservoir and is the pipe through which the reservoir is filled. The oil piunp i is attached to the breather by capscrews /. 28. A simple form of breather and oil filler is shown in Pig. 15 (c). It consists of a pipe a secured to the side of the crank-case 6 by m^ans of capscrews. A funnel-shaped wire screen c is located in the upper end of the pipe for the ptupose of straining the oil as it is poured into the case. The cover is fitted with a second wire screen d that prevents oil from esca- ping from the crank-case with the air or the gases. Digitized by Google 24 GASOLINE AUTOMOBILE ENGINES § 3 29. A common method of attaching a crank-case breather to the top of the crank-case is shown in Fig. 15 (d). In this /«oc^ fh^ KtviQ+Vi^r ic cimnKr q Inner ryipQ q enlarged at thc UppCT it is screwed on. The cap oil from escaping with the into the upper part of the )ject up above the manifold, y in details of construction ley are aU used for the same obtaining the desired result s, as illustrated in Fig. 15, show the general design. 3 design of inlet manifolds nportant considerations are that the incoming fresh charge be equally divided among the various cylinders and that the mixtiu^ going to the cylinders be of uniform richness. These problems are comparatively simple with four-cylinder, four-cycle engines, because the lengths of the branches, or pipes, nmni'ng to the inlet valves can easily be made equal. The ordinary type ines having their cylinders Digitized by Google §3 GASOLINE AUTOMOBILE ENGINES 26 cast in pairs, consists simply of a main inlet pipe leading from the carbureter and two branches leading to the inlet- valve chambers. The manifdd may be in the form of the letter T, like that shown in Fig. 16 (a), or it may be in the fecm of a Y, like that shown in X<&)- The two-branch type of manifold is possible only in motors having the inlet valves of adjacent cylinders placed side by side. With engines having the cylinders cast separately, the manifold is provided with four branches, and where the cylinders are cast en bloc the gas inlet sometimes consists simply of a single pipe leading from the carbureter to the cylinder casting. With a gas inlet of this type, the charge is distributed to the valves through passages in the cylinder casting. 31. In the six-cylinder engine of the four-cyde type, the problem of gas distribution is much more complex than in the Pic. 17 four-cylinder engine, because of the greater number of valve chambers to which the mixture must be conducted. The most efficient form of manifold depends largely on the order of firing and on the grouping of the cylinders. A simple T-shaped manifold for a six-cylinder engine having its cylinders cast in pairs is shown in Fig. 17. It is similar to the T-shaped, four- cylinder manifold, except that there are three branches leading to the cylinders, each branch supplying fuel to the inlet valves of two cylinders. In some engines, the carbureter is located on the opposite side of the engine from the inlet valves, and the inlet manifold extends over the tops of the cylinders. This forms a long inlet passage from the caii>tu^ter to each valve. In other cases, the inlet pipe is very short. A short inlet pipe is generally to be Digitized by Google 26 GASOLINE AUTOMOBILE ENGINES §3 desired on axxxnint of the condensation that is liable to take place in one of considerable length. Six-cylinder manifolds are sometimes made Y-shaped or V-shaped, and the pipes are often curved in order to provide room for accessories. Inlet manifolds are fastened, to the cylinder castings by capscrews or by means of yokes and studs. They are most frequently bolted through a flanged joint to the carbureter. Inlet mani- folds are generally cast of aluminum, brass, or malleable iron. Some manufacturers are water-jacketing their inlet manifolds for part of their length, to assist in vaporizing the fuel and to prevent condensation, connecting the inlet manifold water- jacket to the cooling S3rstem of the engine. 32. Exhaust Manifolds. — ^The manifold that conveys the exhaust gases to the exhaust pipe is usually in the form of a pipe Fig. 18 of large diameter that communicates- with the various exhaust ports and is connected in the rear to the exhaust pipe that runs to the muffler. The manifold usually slopes downwards at an angle approximating 45° at its rear end, where it is joined to the exhaust pipe. In motors having cylinders that are cast separately, one manifold connection from each cylinder is of course necessary. With cylinders cast in pairs or in threes, two different arrange- ments are possible; there may be a single connection for each cylinder, or there may be a connection for each group of Digitized by Google § 3 GASOLINE AUTOMOBILE ENGINES 27 cylinders. In the case of T-head motors with cylinders cast in pairs, a single connection for each pair is customary, although separate connections are also used. In motors with the cylin- ders cask en bloc, there may be a single connection for each cylinder, one for each pair, one for each set of threes, or simply a single connection to the entire bloc. A common form of exhaust manifold for a four-cylinder engine of the T-head type is shown in Fig. 18 (a). The mani- fold is sometimes provided with longitudinal ribs, as shown, to help cool it. A manifold for a six-cylinder engine of the L-head type is shown in Fig. 18 (fc). It has a separate connec- tion for each cylinder. Those connections are spaced as shown to allow room for the connections from the inlet manifold, which is of the three-branch t>'pe. Exhaust manifolds are generally attached to the cylinder castings by means of capscrews that pass through flanges, although they are sometimes secured by yokes and studs. They are generally made of malleable iron or they are steel castings, but sometimes they are made of steel tubing. RECIPROCATING ANB ROTATING PARTS PISTONS 33. The pistons used in automobile engines are made hol- low to receive one end of the connecting-rod, which is joined to the piston by means of a piston pin. Such pistons are of the so-called trunk type, being coiLstructed in this way so as to make - a shorter and more compsict engine. The piston consists of a hollow cylindrical iron casting that is carefully machined in order to have a good working fit in the cylinder. The diam- eter of the piston is slightly less than the bore of the cylinder. If it were the same, the piston would stick when it becomes heated, because the piston becomes hotter and expands more than the cylinder, which is kept relatively cool by the water- jacket. An air-tight joint is made between the-piston and the cylinder wall by means of piston rings that are placed in grooves surrounding the piston. Digitized by Google 28 GASOLINE AUTOMOBILE ENGINES § 3 34. Piston pins are mounted in the piston in two ways: they are either secured to the piston casting at each end, the central part having a bearing in the small end of the connect- ing-rod, or they are fastened to the upper end of the connecting-- rod and have bearings in the piston casting. A piston having the pin attached to the casting is shown in Pig. 19, (a) being an outside view and (fc) a sectional view. The outside of the piston is provided with three rings a, which form an air-tight joint between the piston and the cylinder wall. These rings are parted, as shown at b, so that they can spring M (b) Pig. 19 outwards against the cylinder wall and prevent the gases from escaping from the combustion chamber into the crank-case. Each of the grooves in which the rings are set, except the lower one, is made with square comers. The lower comer c of the groove in which the lower ring fits is beveled to an angle of 45* instead of being square and thus forms an oil groove, or wiper groove. The sharp edge of the lower ring, on the downstroke of the piston, scrapes or wipes all excess oil on the cylinder wall into this wiper groove, whence this oil is conveyed through holes to the piston pin to assist in its proper lubrication. This construction is used in the Northway motors; some other manufacturers do not use this wiper groove. An oil groove d Digitized by Google §3 GASOLINE AUTOMOBILE ENGINES 29 is turned on the bottom end of the piston for collecting the oil that is splashed upwards from the crank-case and distributing it over the cylinder wall. The piston pin e is hollow, and it is secured in the piston cast- ing by means of a setscrew /, which is prevented from backing out by a short wire that is pushed through a hole in the head of the screw. The setscrew prevents the piston pin from turning in the piston and from moving endwise and thus scoring the cylinder wall. The middle part of the pin e fits in a hard bronze bushing g in the upper end of the connecting-rod. 35. There are several additional methods of fastening the piston pin to the piston. Some of these methods are shown in Fig. 20. In (a) the pin is held in place by a locking screw a that screws into the boss b of the piston and extends through a hole in the hollow piston pin c. The locking screw is pre- vented from un- screwing very far by means of a cotter pin d that passes through a hole in the inna: end of the screw. Insome cases a nail or a piece of wire is used instead of a cotter pin. Some- times use is made of two setscrews and a single piece of wire; the wire is made to pass through the holes in both screws, and its ends are ttuned back, as shown in (6). In another method, as shown in (c), the screw passes clear through the piston pin and the end screws into the boss. The screw in this case is prevented from backing out by a short piece of wire or a pin that passes through a hole in its head and strikes against the inside of the piston. In still another method, as shown in (d), Pig. 20 Digitized by Google 30 GASOLINE AUTOMOBILE ENGINES §3 the screw is tapered over part of its length. The tapered part passes through a hole in one side of the piston pin and screws into a hole in the other side. Screwing up the pin draws the tapered part tightly in place. Some pins are held in position by placing a piston ring around the piston and over the ends of the pin. In other cases, various kinds of keys are used for keying the pin in the piston bosses. 36. Two sectional views of a piston having the pin secured to the connecting-rod are shown in Fig. 21. The small end a of the connecting-rod is spUt and clamped to the middle of the piston pin by means of a capscrew 6, which passes through the lugs c. The pin is free to turn in the piston bosses d. The Pig. 21 piston shown is provided with four piston rings e and two oil grooves /. All the rings are located above the piston pin. In some designs, the connecting-rod end is pinned to the pis- ton pin by means of a tapered pin that is fitted with a nut at one end. The pin passes through the end of the connecting-rod and through the piston pin, and is held in place by the nut. 37. The piston pin is usually set as near to the head end of the piston as possible, leaving just room enough for the piston rings beyond the piston pin. The object of thus loca- ting the piston pin is to make the engine as low as possible, and, in the case of the two-cycle engine, to reduce the size of the crank-case so as to give a higher compression in the latter. Digitized by Google §3 GASOLINE AUTOMOBILE ENGINES 31 In two-cyde engines, the shape of the top of the piston is very important, particularly if the transfer port is located in the side of the cylinder. The part of the piston that projects upwards, as shown at a. Fig. 22 (a), and that deflects the incom- ing charge of gas so that it clears the cylinder of the burned gases, is called a deflect^ or, or baffle. Instead of using such a projection, the piston is in some cases so shaped as to deflect the gases in the same manner; such a piston is shown in (6). 38. The piston of a two-cycle engine is made longer than the stroke, because other- (a) wise the exhaust port would not remain completely covered during the compression stroke and the gas in the crank-case would escape to the atmosphere. In three-port, two-cycle engines, a piston ring is placed at the lower end of the piston to prevent the fresh charge in the crank-case from escaping past the piston and out of the inlet port. Such rings are shown in Fig. 22. Fig. 22 PIfirrON RINGS 39. On accoimt of the mechanical impossibility of making a solid piston so that it will have an air-tight and at the same time a free-running fit in the cylinder tmder the conditions met in automobile practice, elastic, expansible piston rings made usually of close-grained, gray cast iron, are used to make a tight joint. For this purpose the piston is grooved and rings of the form shown in Fig. 23 are sprung, or snapped, into the grooves. These rings are commonly called snap' rings. They are split, or cut, in two on one side so that they may have an expansive elastic action to press them close against the cylin- der walls. Piston rings are made of such diameter that they 222B— 14 Digitized by Google 32 GASOLINE AUTOMOBILE ENGINES §3 press lightly against the wall throughout their entire drcum- ference. The joints in the ring where it is spUt are made in several different forms, some of which are illus- trated in Fig. 23. 40. The piston ring shown in Fig. 23 (a) is of uniform cross-section, with the ends lapped at the parting, as shown at a. The type of ring is fre- quently made eccentric; that is, thinner at the ends than at the back b. The parting in the ring shown in (6) is a diagonal spUt, as shown at a; it is less liable to cut or scratch the cylinder than the one shown in (a), as no part of its parting line is parallel with the motion of the piston. The parting of the ring shown in (c) is also diagonal, but it differs from that shown in (6) by having the point a made square and a notch b milled in the opposite comer of the other end, thus forming a rectangular space between the ends of the ring. Into this space fits a pin that holds the ring in place in the groove. A two-piece concentric ring is shown in (d). One ring is placed within the other, and each ring has a flange that extends over Digitized by Google § 3 GASOLINE AUTOMOBILE ENGINES 33 the other, closing each opening. This form of ring is known to the trade as the leakproof ring, A composite ring of the t5rpe shown in (e) is tised in the Marmon engine. This ring consists of a heavy, plain, wide ring a, on the outside of which are two thin rings 6 broken at c on opposite sides and pinned, as shown, quartering the break in the inner ring. The office of the heavy inner ring a is to produce the expansive force, while the thin outer rings conform perfectly to the shape of the cyUnder. In (/) is shown a sectional piston ring used in some Chalmers engines. It consists of an outside ring a, which is parted at 6, and six inner segments c, each of which is provided with a flat spring d. When the ring is placed in its groove, the springs force it outwards against the cylinder wall. The outer ring and the inner segments are of triangular cross-section; hence, when the springs expand the segments, they tend to sUde on the outer ring and fill up the groove endwise. 41. Sometimes an additional ring is placed near the open, or crank, end of the piston. Rings placed in this position are generally called oil rings. They are supposed to aid in dis- tributing the lubricating oil over the surface of the cylinder bore, and also to regulate the amount of oil that passes up from the crank-case into the combustion chamber. In order to accomplish this regulation, they are made in diflferent forms to meet the conditions under which the engine operates with regard to the amount of lubricant that is splashed, or thrown, into the open end of the cylinder. In some cases, they are made with true cylindrical surfaces, in the same manner as the other rings. In other cases, the outer surface of the ring is beveled part way across the surface and the ring is put in place with the beveled side either toward the open end of the piston or away from this end, according to whether the desire is to have the ring allow more or less oil to pass by it than in the case of a ring with a true cylindrical outer surface. The oil rings also aid in making an air-tight joint and thus in preventing loss of pressure due to blowing of the gases past the piston. How- ever, oil grooves are used more extensively than oil rings for distributing the lubricant over the surface of the cylinder walls. Digitized by Google 34 GASOLINE AUTOMOBILE ENGINES S3 CONNECTINO-BODS 42. Connecting-rods for automobile engines are usually made of drop-forged steel and are of I-beam cross-section. The lower, or crank-shaft, end of the connecting-rod is made large and contains a bearing for the crankpin; the upper end is smaller and either forms a bearing for the piston pin or is rigidly secured to it. 43. A common type of comiecting-rod is shown in Fig. 24 (a). It is of I-shaped section, the large end a being spUt at (a) Fig. 24 right angles to the rod through the center of the bearing and having a bronze or other bearing-metal lining 6. The two parts of the bearing are held together by the bolts c and d, which pass through the cap e. The bolts are provided with castellated, that is, slotted nuts, and cotter pins passing through the bolts and nuts, to prevent the latter from loosening. The smaller, or piston-pin, end / is forged solid, then bored out, and a Digitized by Google § 3 GASOLINE AUTOMOBILE ENGINES 35 bearing metal bushing, usually of bronze, pressed into place, as shown at g. A connecting-rod designed so that the small end may be clamped to the piston pin is shown in (fc). The piston-pin end is split in the manner shown, a heavy capscrew being used to draw the parts tightly against the piston pin, which turns in bearings in the piston casting. The head end forms the usual crankpin bearing, the halves of which are held together by two bolts. In some cases the halves of the lower connecting-rod bearings are held together by means of four bolts instead of by two. Fig. 24 (c) shows a hinged crankpin end that is sometimes used on connecting-rods of automobile engines. The end a and the cap b are hinged at c, and a bolt d is provided to hold the parts together. In the more e;cpensive engines, the piston pin and the bush- ing are often made of case-hardened steel, and both pin and bushing are ground to fit. CBANK-SEULFTS 44. Craiik-slia,fts for automobile engines are made of special grades or alloys of steel, so that they may be as Ught as possible and yet be strong enough to resist the twisting and bending action to which they are subjected, the bearing part being made suflBdently ample to withstand the wear due to continuous rotation at high speed. Automobile-engine crank-shafts are always made in one piece, and are either machined from a rough flat forging or drop-forged in dies. 45. Crank-shafts for four-cylinder engines are supported by two, three, or five bearings. A two-bearing crank-shaft is shown in Fig. 25 (a) ; a three-bearing shaft, in (b) ; and a five- bearing shaft, in (c). In each case the journals that turn in the bearings are shown at a, and the crankpins at b. Crank-shafts for four-cylinder, four-cycle engines are always made in one of the three forms shown; that is, with the two outer crankpins in line and the two inner crankpins in line, so that the two pairs of crankpins are 180° apart. Digitized by Google 36 GASOLINE AUTOMOBILE ENGINES §3 Crank-shafts for six-cylinder engines are supported by three, four, or seven bearings. That shown in Fig. 25 (d) is a four- bearing crank-shaft, and that shown in (e) is carried on seven bearings. In each case, the journals are shown at a and the crankpins at b. The cranks are arranged in pairs, one and six f 6rming a pair, two and five forming a pair, and three and four forming a pair. The crankpins of each pair are in line, and the pistons connected to these cranks move in tmison; the several pairs of crankpins are 120° apart. In the four-bearing crank- shaft, illustrated in (d), each end crank is connected to the adjoining crank by means of a dummy journal; in some other cases, the two crankpins are directly connected by a single straight arm. Digitized by Google § 3 GASOLINE AUTOMOBILE ENGINES 37 VALVES AND VALVE MECHANISM VALVES 46« A poppet valve consists of a disk with a stem at right angles to the plane of the disk. Poppet valves are used for the admission of the charge and the control of the exhaust. The valves open in the direction of the axis of the stems, and are held to their seats by springs. As they open inwards, they have no tendency to leave their seats during the explosion, the pres- sure in the cylinder helping to keep them on their seats. The valve seats and valve-stem guides may be located in removable heads or in the cylinder casting. The valve seats are usually made of cast iron. Nickel steel, and of late, tungsten steel, has become quite popular for valves when the head and stem are made in one piece; nickel steel is also used extensively for the heads of built-up valves having the stems made of machinery steel. It is claimed that valves made of nickel steel will neither warp nor scale frgm excessive heat; in addition, valves made of tungsten steel seem to be free from pitting. Cast-iron exhaust valves having steel stems are sometimes used, and also soft steel valves faced with cast iron welded to the head. The valve seats are occasionally flat, though more frequently they are beveled to an angle of 45°. The bevel-seat type of valve is kept tight more easily than the flat-seat type, and for this reason it is generally used. 47. A valve that is opened by mechanical force applied by rigid parts is called a mechanical valve, or, less commonly, a mechanically operated valve. An exhaust valve of the poppet type must always be mechanically operated, because it must be lifted against the pressure in the cylinder at the time the exhaust is to begin. The inlet valve, however, can be so constructed as to be opened by the pumping action of the piston during the suction stroke. When thus opened it is known as an automatic inlet Digitized by Google 38 GASOLINE AUTOMOBILE ENGINES § 3 valve; such valves were formerly used extensively on auto^ mobile engines, but they are now employed in only very rare instances. I inlet valve is shown in place : a rests on the beveled seat b •ds through the guide d to the part of the valve stem, how- ever. The valve spring / is held in compression between the guide d and the cap g, which is held in place by a collar h with a radial slot that fits in a groove around the stem c. As the cam i turns so that its lobe is directly under the valve lifter ; , the valve is raised against the compression of its spring and an opening is formed between the edge of the valve and the seat. The valve lifter / by suitable means is prevented from turning in the valve-lifter guide kf and can be adjusted by screwing the adjusting screw e up or down. A lock- nut / prevents the adjusting screw from turning out of he top of the valve disk is a used when grinding the valve, d in place by means of a key le valve stem, instead of by a md exhaust valves, which are in place in the cylinder head ts against the flat seat 6 when /es open downwards into the Digitized by Google § 3 . GASOLINE AUTOMOBILE ENGINES 39 combustion chamber and are operated by means of the rocker- arms Cy which, in turn, are operated by means of long push rods. The valve stem moves in the guide d. Between a shoulder e on the guide and a cap/, which is screwed on the end of the valve stem, the spring g is compressed and therefore Pig. 27 holds the valve to its seat. The rocker-arms act against adjust- ing nuts h on the end of the valve stem. The cylinder head is shown cut in half in the illustration so as to show the valves in place. In this engine, the cylinder head is cast separate from the cylinder. VALVE MECHANISM 60. Valve sprlng:s are usually made from steel spring wire or from soft cast-steel wire, the former being wound cold and not requiring any heat treatment; when the soft wire is used, the spring is hardened and tempered after it is formed. Springs made from spring wire have the disadvantage of becom- ing set if subjected to hard usage, and hardened and tem- pered springs are liable to break if not tempered just right. Helical springs^ or springs wound in the form of a screw thread, as shown at g, Fig. 27, are used more often than any other on automobile engines. Occasionally, the springs on inlet and Digitized by Google 40 GASOLINE AUTOMOBILE ENGINES §3 exhaust valves are made up in the shape of a cone. Such springs are called cone-shaped springs. 61. The cams for operating the valves of an automobile engine are usually forged integral with the camshaft, as shown in Fig. 28. In a few cases, however, they are made separate and secured to the cam-shaft by means of tapered pins. Cams vary considerably in shape, or profile, the outline depending to some extent on the tjrpe of cam-follower , which is Fig. 28 the part of the valve-lifting mechanism that is in contact with the cam. An inlet-valve cam designed to be used with a roller follower is shown in Fig. 29 (a), and the corresponding exhaust- valve cam is shown in (fe). Another common form of cam, also used with a roller follower, is shown in {c). In (d) is shown a cam having rising and falling shoulders a and 6 of convex form, giving a gradual opening and closing. This form of cam is used with a mushroom, or flat-bottomed, cam-follower. 62, If the inlet and exhaust valves of an automobile engine are located in the sides of the cylinders, they are usually oper- PiG.29 ated directly from cams acting on valve lifters, which are placed between the cams and the valve stems. There are various designs of valve lifters; some are flat where they rest on the cams, others are rounded off, and still others are pro- vided with rollers at the bottom end. The majority of makes of valve lifters are provided with some means of adjusting their length; usually an adjusting screw is placed in the upper end. Digitized by Google §3 GASOLINE AUTOMOBILE ENGINES 41 53. A simple form of valve lifter is shown in Fig. 30 (a). It cxwisists of the solid cylindrical part a, which has-a flat lower end fc, thus forming a large bearing surface for the cam. The tipper end of the valve lifter supports the valve stem c. No means of adjustment is provided for this lifter, but the valve stem c may be lengthened by drawing it out as shown by the dotted lines d. The valve lifter shown in this view is used on the Ford, model T, engine. Another simple form of valve lifter is that shown in view (fc). It is used on the Maxwell four-cylinder, 25-horsepower engine. The entire lifter is made of pressed steel. The body a is cup-shaped and is pressed with square cor- ners at the bottom, thus forming a large flat con- tact surface for the cam. The top part 6 of the lifter is threaded and screws into a; hence, the length can be adjusted by turn- ing the squared end c, A lodcnut d is provided to prevent the part b from jarring out of adjustment. 64. A valve lifter of *^^ <^> the rounded type is shown '^^- 30 at y. Fig. 26. Instead of being fitted with a roller or having a flat contact surface, the lower end of the lifter is made rect- angular in shape and rounded off. With a lifter of this type, some means must be provided for preventing it from turning in its guide and getting out of alinement with the cam. In the example shown, the guide k is slotted and the rectangular part of the lifter extends into the slots, thus keeping it in line with the cam. 65. The roller type of valve lifter, several forms of which are shown in Figs. 31 to 33, is very extensively used. Digitized by Google 42 GASOLINE AUTOMOBILE ENGINES §3 Two adjacent lifters used on the Northway engine are illus- trated in Fig. 31, which shows an external view of one and a sectional view of the other. On account of operating different valves, these lifters are in different positions, but they are exactly alike and similar parts are lettered the same in the two views. The body a of the lifter is slotted at the lower end to receive a roller 6, which is carried by the pin c. The roller is kept parallel with the cam by means of a slot d in the guide e, into which the roller extends. As the valye lifter is raised and lowered by the cam, the roller is guided by the slot in the guide and hence does not move from its correct position on the Pig. 31 Fig. 32 cam. This valve lifter is made adjustable by means of the adjusting screw /, which can be screwed up or down as required. The locknut g prevents the screw / from being jarred out of adjustment. Washers h and i are placed between the nut g and the upper end. of the lifter. The guide e is held in place by the flange formed on it, which is clamped between the cylinder casting and the crank-case. Digitized by Google § 3 GASOLINE AUTOMOBILE ENGINES 43 56. Another valve lifter that operates on the same prin- ciple as the lifter just described is shown in longitudinal sec- tion in Fig. 32. An important feature of this lifter is that a fiber block a is set in the upper end of the adjusting screw 6 to deaden the sound produced by the end of the lifter striking the end of the valve stem. The roller c moves up and down in the slotted guide rf, which prevents it from coming out of alinement with the cam. The guide is made of bronze, and is held in place by stud bolts e. This type of lifter is used on the Pierce-Arrow engine. 57. In Fig. 33 (a) \ is shown the valve lifter used on the Buick engine. It dif- fers slightly from the preceding. Two ad- jacent lifters are shown with the yoke a in place for holding ^'^* ^ the guides 6 in position. In this form of valve lifter, the ends of the roller pin c extend beyond the lifter d and work in nar- row slots e in the guide &, thus keeping the roller in alinement Digitized by Google 44 GASOLINE AUTOMOBILE ENGINES § 3 with the cam. The lifter is made hollow in order to lighten it and to receive the end / of the push rod, which in this case is used to operate overhead valves. Two adjacent valve lifters used on the Beaver engine are shown in differ- ent positions in Pig. 33 (fe). In this lifter, the roller a is held parallel with the cam by means of a pin b that passes through the lifter and extends into slots c in the guide d. Adjustment is made by means of the com- mon form of adjust- ing screw and lock- nut. The guide is held in place by the cyhnder casting and the crank-case. 58. In some en- gines it is the prac- tice to make use of a cam-lever placed between the cam and the end of the valve lifter, as shown at a, Pig. 34. The purpose of this lever is to eliminate, as far as i lifter. The lever is middle a roller b that Digitized by Google § 3 GASOLINE AUTOMOBILE ENGINES 45 follows the cam c. The side thrust of the cam is therefore taken by this roller and by the lever a, and is not transmitted to the lifter d. The lever is so arranged that it it is at right angles to the lifter when the valve is raised half way. The type of cam lever here illustrated is used in the Rutenb^ motor. 69. Poppet valves loca- ted in the cylinder head and opening downwards are ope- rated by means of tappet rods and levers, as shown in Fig. 36, which illustrates the method used in the engine of the Franklin car. The lever a is pivoted at 6 and is ope- rated by means of the tappet rod c. The rod c is raised by means of a lifter d that moves in a guide e and that in turn is raised by the cam /. A spring g at the base of the tappet rod keeps the lever a constantly in touch with the valve stem and prevents clicking. The mechanism is adjusted by means of an adjusting screw fc, which is prevented from backing out by the locknut i. The tap- pet rod is yoked at its top end and fits over the end of the lever a. ^""'^ In modem engines, the valve stems and springs are covered by a removable housing, excepting in case of overhead valves. 60. Three methods of driving the cam-shaft and the cir- culating pimip and magneto shafts are illustrated in Figs. 36 to 38. Gears or silent chains, or a combination of both, are located at the forward end of the engine, and they connect Digitized by Google 46 GASOLINE AUTOMOBILE ENGINES § 3 the crank-shaft with the various auxiliary shafts. The gears or chains are enclosed in a casing, one part of which is usually Pig. 36 cast integral with the crank-case. The front part is made in the form of a cover-plate and is removable. 61. Fig. 36 shows the timing gears used on the White Fig. 37 40-horsepower engine. The cam-shaft gear a is driven from the crank-shaft gear b through the idler c. Gear a has a diameter Digitized by Google § 3 GASOLINE AUTOMOBILE ENGINES 47 that is twice that of &; hence, its speed is one-half that of the crank-shaft, as is reqtdred for a four-cycle engine. The magneto shaft d is also driven through the idler and rotates at crank- shaft speed. The pump shaft is driven by the small gear e, which meshes with the cam-shaft gear a. Helical gears are used in order to eliminate noise as much as possible. The removable cover is attached by capscrews and bolts that pass through the holes/. In Fig. 37 is shown the silent-chain drive arrangement used on Cadillac engines. The cam-shaft is driven at one-half Fig. 38 crank-shaft speed by the silent chain a running on sprockets 6 and c, and the motor-generator and circulating-pimip shaft is driven by the chain d running on the sprockets b and e. The motor-generator is an electrical machine used for cranking the engine and lighting the car. A combination drive consisting of helical gears and a silent chain is shown in Fig. 38. The cam-shaft is driven from the crank-shaft by a gear a that meshes with a gear on the crank- shaft. The magneto shaft is driven by the gear b meshing with the cam-shaft gear. A silent chain c connects the crank- shaft with the electric starting device shaft. This chain also 222B— 15 Digitized by Google 48 GASOLINE AUTOMOBILE ENGINES § 3 drives the circulating pump and the commutator shaft. The cover is fastened on by means of capscrews. This arrangenient is used on engines built by the Continental Motor Company. The chain c is lubricated by running in a bath of oil. rriNGS Aia> engine rating PBIMINO CUPS means of which an engine may be primed ► the combustion chamber, and which may eve the compression, is shown in Fig. 39. lar plug a carefully groimd to fit the taper- 2t in which this plug is turned by means of the handle h. The cup c is suflBdently large to hold the required amoimt of gas- oline for the priming charge when the engine is to be started. The plug a is held in place by a phosphor-bronze spring d placed between two washers e and /, and a pin g serves to hold the whole together. The tension of the spring d is suflSdent to hold the plug firmly in position and to take up wear, thus preventing loss of compression by leakage. The spring also serves to keep • heavy vibration. In using this plug, the : is poured into the cup c and the cock a ermit the gasoline to flow into the cylinder [ine is started or during the suction stroke, also used for introducing kerosene or any tnce into the cylinders for the piupose of a deposits. AIR-PRESSUBE PUMPS gasoline tank is located at a relatively low lobile, as, for instance, at the rear of the le body line, the gasoline is forced to the Digitized by Google § 3 GASOLINE AUTOMOBILE ENGINES 49 carbureter by means of pressure maintained in the tank. This pressure in most cases is produced either by a hand-driven pump or by a power-driven pump that is driven from the engine. 64. Two engine-driven air pumps are illustrated in Fig. 40. A perspective view of the air-pressure ptunp used on the North- way motor is shown in (a). The cylinder a is of cast iron and is bolted to the side of the crank-case by means of the flange 6. The piston c is operated by one of the exhaust-valve cams, which bears against the follower d. The follower is kept in contact with the cam by the spring e. As the cam rotates, ra> (b) Pig. 40 the piston moves in and out of the cylinder a. When the pis- ton imcovers the ports / drilled in the cylinder wall, air is taken in, and as the cam rotates the piston is forced inwards, com- pressing the air and driving it out of the delivery pipe g. An adjustable check-valve is located at fe, and the amount of pres- sure carried in the gasoline tank may be varied by screwing this adjustment in or out, as may be riequired. 65. A cross-sectional view of the air pressure pump used on the Steams-Knight engine is shown in Fig. 40 (&). The cylinder a is bolted to the crank-case, as shown, and the piston b Digitized by Google 60 GASOLINE AUTOMOBILE ENGINES §3 is driven through the connecting-rod c from one of the sliding- sleeve connecting-rods of the engine. On the outward, or suc- tion stroke of the piston 6, the air enters the cylinder a through a groove at the top, and on the inward, or compression, stroke the air is forced out through check-valve e and outlet pipe /. The pressure to which the air is compressed may be varied by screwing the adjustable head g in or out, as desired. The head is kept in any adjustment by means of the locknut h. A plug is screwed into the opening shown at d, and is removed to drain excess oil from the cylinder. The pressure to which these ptunps compress the air is gen- erally from i to 3 poimds, although it may be varied at will by means of the adjusting device. HORSEPOWER RATING 66. Gasoline automobiles are rated in the United States according to the horsepower of the engine. This horsepower is calculated by means of a formula called the A. L. A. M. for- mula and also the S. A. E. fonuula, which is so named because it was adopted by the Association of Licensed Auto- mobile Manufacturers and afterwards by the Society of Auto- mobile Engineers for calculating the rated horsepower of a four- cycle gasoline automobile engine. The formiila does not give the exact power delivered under every condition nor the exact theoretical horsepower, but it offers a means of comparison between different engines. It is based on a piston speed of 1,000 feet per minute, an average pressure in the cylinder of 90 pounds per square inch of piston area, and a mechanical efficiency of 75 per cent. The A. L. A. M. formiila is as follows : H.P. = ^, 2.5 in which H . P. = horsepower ; -D = cylinder diameter, in inches; A/'=nimiber of cylinders. Expressed in words, the horsepower of a four-cycle gasoline automobile engine is equal to the diameter of the cylinder, in Digitized by Google § 3 GASOLINE AUTOMOBILE ENGINES . 51 inches, multiplied by itself and by the number of cylinders, and the product divided by 2.5. For example, the rated horsepower of a four-cylinder, four- cycle engine having a bore of 5 inches may be found by this formula as follows: H.P. = ^, 2.5 in which Z>=5; Therefore H.P. = — - 2.5 _25X4 2.5 2.5 Hence, the horsepower of the engine is 40. For two-cycle engines, the horsepower may be taken as approximately 1.65 of that of a four-cycle engine of the same dimensions calculated by the formula just given. From the fact that there are twice as many explosions per minute in the cylinder of a two-cycle engine as in the cylinder of a four- cycle engine running at the same speed and having the same dimensions, it might be supposed that the power developed would also be twice as great instead of about 1.65 times as great. However this is not the case because of certain features of the two-cycle engine that tend to lower its horsepower out- put and cause it to vary more than that of the four-cycle engine. These are, usually, lower compression and lower mean effective pressure due to inefficient scavenging, or cleaning, of the cylinders after each working stroke. There are, of coiu-se, exceptional cases where the output of a two-cycle fengine is nearly twice that of a four-cycle engine of the same dimen- sions but the ratio given is usually considered as the average. 67. The horsepower of four-cycle engines having from one to six cylinders and a bore varying from 2^ inches to 6 inches, as computed by the A. L. A. M. formula, is given in Table I. Digitized by Google 52 GASOLINE AUTOMOBILE ENGINES §3 TABLE I HOBSBPOWBB BT A. L. A. M. FOBmJLA Bore Horsepower Inch MiUi- One Two Four Six meters Cylinder Cylinders Cylinders Cylinders 2i 64 2-5 • 500 10.00 1500 2| 68 2.81 5.61 11.23 16.83 2i 70 302 6.04 12.08 18.13 2j 73 3-34 6.68 1337 20.00 3 76 360 7.20 14.40 21.60 3i 79 3.92 783 15.64 2350 3l 83 4.22 8.45 16.92 2539 3f 85 456 9.12 18.21 27.30 3i 89 4.91 9.82 19.61 29-45 3f 92 527 10.53 21.08 31-57 3i 95 5-62 11.25 22.50 33-75 3i . 99 6.05 12.11 24.22 3632 4 102 6.40 12.80 25.60 38.40 4i 105 6.80 1360 27.20 40.80 4l 108 7-25 1450 29.00 43-50 4i III 765 1532 3065 46.00 4J 114 8.10 16.20 32.40 48.60 4f 118 8.57 17.14 34.28 51.41 4i 121 905 18.10 36.15 54.20 4J 124 9-55 19.12 38.25 57-21 5 127 10.00 20.00 40.00 60.00 5i 130 10.55 21.10 42.20 6330 5i 133 11.04 22.10 44.20 66.40 5l 137 "•59 2318 46.34 69.50 5i 140 12.12 24.24 48.48 72.72 5f 143 12.68 2538 50.80 76.10 5i ' 146 1325 26.50 5300 7950 5i 149 13-81 27.62 55-28 82.88 6 152 14.42 28.53 5770 86.64 Digitized by Googk AUTOMOBILE-ENGINE AUXILIARIES COOLING, MUFFLING, AND GOVERNING COOLING SYSTEMS INTRODUCTION 1. In an internal-combustion engine, unless provision were made for cooling, the heat from the explosion of the charge would raise the temperature of the cylinder walls and piston so high as to render lubrication impossible. The devices employed for cooling purposes comprise what is known as the cooUng system of the automobile. Most automobile engines are cooled by circulating water through the space between the outer wall of the cylinder and a jacket casing that surrounds the cylinder head and the part of the cylinder barrel nearest, the head. Air is used for cooling in only a comparatively small proportion of automobile engines. About the only objection to the use of water for cooling is that it is liable to freeze in cold weather. In order to over- come this objection, however, various substances are added to the water or dissolved in it so as to form a mixture that will not freeze until the temperature is considerably below that at which pure or nearly pure water freezes. 2. When water is used for cooling, it enters the jacket space generally either at its lowest part, or just below the COPYNIOHTBD 0Y INTERNATIONAL TEXTBOOK COMPANY. ALL illOHTS RBBBRVBD §4 ^ t J^ ^ ' ' •-' ' ^'^i^'z^cl b; yGoogk 2 AUTOMOBILE-ENGINE AUXILIARIES §4 exhaust valve, and flows out at the highest part. It is extremely important to have the water flow from the highest part of the jacket space, because an air pocket or steam pocket would be formed if a part of the enclosed space were higher than the outlet. It is also very important that the jacket space should be shaped so that there is no part from which the water cannot flow upwards toward the outlet. The hot water from the jacket passes through connecting pipes to a radiator^ where it is cooled, and from the radiator it passes back to the jacket space of the engine again. It then repeats its cycle of cooling the engine and being cooled in the radiator. Circulation is maintained either by a pimip, which forces the water through the system, and which on this account is called a forced-circulation system, or by what is known as thermal circulation, which means circulation due to the heating of the water. WATER COOLING 3. Forced-Circulation Cooling System. — In Fig. 1 is shown the water-cooling system of the Studebaker "20" car, which system serves well to illustrate the tjqjical arrangement of the cooling-system parts in automobiles using monobloc cylinder castings, and having the engine at the forward end of the car, as is now the tmiversal practice. In order to show the cooling system clearly, part of the water-jacket is broken away and the radiator, as well as the pump, is illustrated in section. The cooling water passes from the top of the water- jacket a surrounding the upper end of the fotu* cylinders through a flexible hose connection b to the upper tank c of the radiator; it then passes downwards through the radiator tubes d, which are surrounded by horizontal fins soldered to them, to the bot- tom tank e of the radiator. This bottom tank e is connected by a pipe, which cannot be seen in the view given, to the casing of the circulating pump/, which pimip is driven from the engine cam-shaft and delivers the cooling water through the pipe g to a manifold h attached to the bottom of the water-jacket. This manifold has two outlets into the water-jacket in order to insure a better distribution of the cooled water than is Digitized by Google § 4 AUTOMOBILE-ENGINE AUXILIARIES 3 possible with a single outlet. The fan i, which is rotated at a high speed by the engine, draws air over the tubes d of the radiator and their surrounding fins, thereby abstracting heat from the cooling water; that is, cooling it. 4. With an engine having monobloc cylinders, as shown in Fig. 1, a single outlet from the top of the water-jacket is usually sufficient. When the engine has individual cylinders or twin cylinders or triple cylinders, there must be a manifold Fig. 1 to convey the cooling water to and from the water-jackets of the cylinders. This is clearly shown in Fig. 2, which illus- trates the water-cooling system of a six-cylinder Packard car. In the engine of this car, the cylinders a are cast in groups of two; hence, there are three top outlets b from the water-jackets, the outlets being connected to each other by hose connections c and finally to the top of the radiator d by a hose connection e. Instead of connecting the outlets from the top of the water- Digitized by Google 4 AUTOMOBILE-ENGINE AUXILIARIES §4 jackets with rubber hose, as is done in the Packard engine illustrated, many manufacturers use a metallic manifold with the piping and outlets cast or otherwise formed as a single piece ; the final connection to the radiator is made with a rubber hose, however. The hot water coming from the top of the water-jackets flows through the upwardly inclined manifold into the top water tank of the radiator and passes downwards through numerous narrow water passages into the bottom water tank of the radiator, from which it passes through an elbow / and Pic. 2 a hose connection g to a circulating pump h and thence past a hydraulic governor i to the manifold ;, which has three branches, one leading to the bottom of the water-jacket of each cylinder casting. The hydraulic governor i, although inserted in the water-cooling system, has no connection with the cooling of the engine; its purpose will be explained in the proper place. In order to aid in cooling the water passing through the radiator, a fan k driven by a belt / from the engine draws air through the square openings between the water pas- sages joining the top and bottom tank of the radiator. A drain cock m is placed at the lowest point of the water-cooling Digitized by Google § 4 AUTOMOBILE-ENGINE AUXILIARIES 5 S3rstem; when this cock is opened, all water can be drained from the system. The carbureter used with the Packard engine here illustrated is water-jacketed in order to keep it warm and thus aid vapor- ization of the gasoline; hot water is taken from the cooling system through the pipe n txom the top of the water-jacket of one pair of cylinders. This water cools somewhat in passing downwards through the carbureter jacket and is discharged through a pipe o into the engine-cooling system directly above the water-circulating pump h. The water system of a water-cooled engine is filled through an opening on top of the radiator, and this opening, when not in use, is closed by a filler cap, as shown at p. 5. Thermo-Siplion Cooling Systems. — ^Although most automobile manufacturers seem to prefer to use the forced- circulation system of water cooling, there are some who use successfully the thermal system, or as it is better known, the thermO'Siphon system of water cooling. This cooling system is characterized by the absence of a circulating pump, the cir- culation being established and maintained by heating the water to a higher temperature in the water-jacket of the cylinders than in the remainder of the cooUng system. Inasnmch as hot water is lighter than cold water, it tends to flow upwards; conversely, cold water is heavier than hot water and tends to flow downwards. 6. The most widely known example of a thermo-siphon cooling system is found in all Ford, model T, cars having a manufacturer's number higher than 2,500. Cars of this model bearing a lower number were fitted with a forced-circulation system. The radiator consists of an upper tank a. Fig. 3, and a lower tank b tmited by a lai^ge number of vertical tubes supplied with horizontal cooling fins. The water-jacket c surrounds the upper part of the four cylinders, which, together with the upper half of the crank-case, are a monobloc casting. The heated water passes from the water-jacket through the upwardly Digitized by Google Drougnx aooui in xne same manner as m xne rora car, ana is shown by the arrows. A fan d driven by the engine assists the cooling of the water by drawing air through the radiator. Digitized by Google §4 AUTOMOBILE-ENGINE AUXILIARIES 8. In the thermosiphon cooling system employed first in the Renault car, which system has since been adopted by several other manufacturers, the radiator, instead of being placed on the chassis in front of the engine, is moimted back of the engine; that is, just in front of the dashboard. Three views of the Renault cooUng system are shown in diagram- matic form in Fig. 5. The radiator a consists of the usual top and bottom tanks, which are united by numerous plain vertical tubes. The top of the cylinder water-jackets is con- nected to the top radiator tank by the manifold 6; the bottom of the water-jackets is connected by the manifold c to the bot- tom radiator tank. Circulation of the cooling water is estab- PlG. 4 lished and maintained in the manner explained in Art. 6. The engine is enclosed by the hood d, which has sloping sides and a sloping top and front; this hood extends backwards to the radiator. The bottom of the engine is protected by the sod pan e, which, like the hood, is closed at the front end and open at the rear. No separate fan is employed to draw air through the radiator; the flywheel/, however, is cast with vanes on its outside, and these drive air to the rear. The circulation of air through the radiator is as follows : Air enters at the sides of the radiator, as shown by the arrows g, and also at the front through the part of the radiator that is not covered by the hood d, as shown by the arrows fe. This air passes from both Digitized by Google t* i Digitized by Google §4 AUTOMOBILE-ENGINE AUXILIARIES 9 sides of the radiator toward the central part covered by the hood and then forwards imder the hood, as shown by the arrows i\ the air then passes downwards under the hood, as shown by the arrows ;', past the flywheel, and out at the rear of the sod pan, the circulation being kept up by the vanes of the flywheel. 9. In a thermo-siphon cooling system, the opening through which the water from the engine enters the upper radiator tank should not be located above its bottom. If this is done, the circulation will stop as soon as the level of the water falls below the bottom of the opening, even if a considerable amount of water is still retained in the tank and the upper ends of the cool- ing tubes are covered with water to a considerable depth. The proper place to connect the pipe coming from the top of the water-jacket is at the bottom of the upper tank, as shown in Fig. 3. In all cases, the cooling system should not be air-tight, but should have an orifice or, overflow^ above the normal level of the water to allow the escape of air, water, or steam. The water expands by heating, and in case it boils, steam is formed. 10. Tyi)es of Radiators. — ^As previously explained, the cooling water heated in the water-jackets of the engine is cooled by passing it through a radiator. In order to cool the water effectually, radiators are usually made of thin metal, with as much surface exposed to the air as possible, and they are arranged so that the air can circulate through them easily. There are two general types of radiators, which are named in accordance with their construction. One of these types is spoken of as the tubular radiator, the cooling being done by passing the heated water through round or flat tubes around which air circulates to abstract heat and carry it away. The second type is known as the cellular radiator, from the general resemblance it bears to a mass of cells; in this type of radiator the water to be cooled surrounds the cells and the air that abstracts and carries away heat passes through the cells. Radiators are always mounted at right angles to the frame of the car, and usually in front of the engine, although some Digitized by Google DMOBILE-ENGINE AUXILIARIES §4 them at the rear of it. As a general rule radiators . some cases radiators, when viewed from above, nth the apex to the front, or are slightly roimded ; ons are adopted only in order to give a distinctive the front of the car. sir radiators nearly always have the tubes sur- large number of thin fins, or gills, that are sol- dered to them, the object of these fins being to in- crease the radiating surface to an extent sufficient to produce satisfactory cooling of the water. Radiators of the tubular type may be divided into two general classes; name- ly, (1) radiators in which each tube has its own fins, and (2) radiators in which the fins are common to all the tubes. At one time ra- diators belonging to the first class were very extensively used, but of late years radi- ators of the second class have displaced them to a large extent. 12. Tubular - Radla- % tor Construction. — Ra- ^ diator tubes with individual ^^ fins are made in two ways, ^c. 6 as is clearly illustrated in 5W (a) is presented a plain radiator tube, in a are circular, being pimched from sheet metal. inese nns are strung over a circular tube 6, after which the tube and fins are dipped into molten solder in order to solder them together. The disks, or fins, are made in various ways. Digitized by Google § 4 AUTOMOBILE-ENGINE AUXILIARIES 11 Sametimes they are simply plain, like washers, in which case their attachment to the tube is rather flimsy; sometimes a col- lar is formed on the disks, as shown at (b) ; and some makers punch the center of the disk in such a way that triangular lugs are formed, as shown at (c). Either of the methods shown in views (6) and (c) permits the fins to be attached to the tube in a substantial manner. In view (d) a part of a Long spirally wound radiator tube is shown. In this radiator tube, the fin is continuous, being formed from a flat strip of copper that is crimped in such a manner that it can be wound spirally around the central tube, as shown. 13« Radiators having tubes with individual fins were at one time made up in the form of coils, the tubes running horizontally and being connected by return bends in such a manner as to form a con- tinuous tube, with the cool- ing water entering at one end and leaving at the other. This method of construction is obsolete, however. In modem practice, when tubes with individual fins are employed, the tubes are placed vertically between a top and a bottom water tank and each tube is independent of the other. The appearance of such a radiator is shown in Fig. 7, which presents a front view. In this illtistration, a is the top water tank, b the bottom water tank, c the filler opening closed by a removable cap, and d are lugs by which the radiator is supported on the side members of the frame of the car. In some cases the lugs are at the rear of the radiator. In no case do the sides form water connections between the top and bottom tanks. The part of the radiator between the two tanks and sides is commonly called the radiator core. 2223—16 Digitized by Google 12 AUTOMOBILE-ENGINE AUXILIARIES §4 which a comparatively small pig. 9 number of flat vertical tubes are used is shown in section in Fig. 10. The tubes a are placed with their narrow sides to Digitized by Google §4 AUTOMOBILE-ENGINE AUXILIARIES 13 the front and the rear, and are soldered into the bottom of the top tank b and into the top of the bottom tank c. The tubes form the water passages in which the water passes downwards, air circulating aroimd them. The two sides of the radiator, as d, for instance, do not form water passages. A nozzle e is attached to the rear of the top tank and is connected to the pipe leading to the top of the engine-cylinder water-jackets. In some cases the tubes are left plain; in other cases, fins of various kinds are soldered to the tubes in order to increase their radiating surface. One way in which the surface is extended is shown at /; a flat strip of sheet metal is punched and corrugated, as shown, and is soldered to one or both sides of the tubes. The corrugated strips then extend the whole length of the tubes. Some- times a false front, made as indicated at g, is fitted into the front end of the radiator in order to convey the impres- sion that the radiator belongs to the cellular type, which is a far more expensive form. An angle h made of sheet metal is usually attached to the rear of the top tank and to the rear of the two sides, forming ^*<=- ^° a ledge for the hood over the engine; this angle is known as a hood ledge. To prevent rattling of the hood on the hood ledge, this ledge is usually perforated and a strip of rawhide belt lacing or some similar material is fastened to its outside. An overflow pipe, whose opening is at i, is usually attached to the upper tank and led along the back of the radiator to a point below the upper end of the lower tank; its lower end is open. This overflow pipe prevents filling the radiator too full, and Digitized by Google 14 AUTOMOBILE-ENGINE AUXILIARIES §4 also provides for free expansion of the cooling water on becoming heated. <c) (d) Pig. 11 agonal cross-section that are laid side by side in such a manner that there is a water space aroimd them. In another widely used construction, sheets of metal are bent to form cells that have water spaces arotind them when suitably assembled It is urged in favor of the individual-tube construction that, Digitized by Google § 4 AUTOMOBILE-ENGINE AUXILIARIES 15 in case of leakage, repairs can be executed with great facility by any one expert in the use of a soldering iron, as a tinsmith, for instance. 17. In the Fedders cellular radiator, individual copper tubes, either A or i ^^ch square, are employed. These, as shown in Fig. 11 (a), are enlarged at both ends and are assembled either staggered, as shown in (6), or in straight Unes, the ends being soldered fig. 12 together. A cross-section through a few tubes of a stag- gered assembly is presented in {c)\ this view clearly shows the tortuous water passages formed by staggering the tubes. When a staggered-tube assembly is used, it is generally placed so that the straight water passages a are horizontal, thus forcing the water to follow a zigzag path in passing downwards through the radiator. A cross-section through a tube assembly in which the tubes are set in straight lines is shown in {d). Here, the water pas- sages are in line both vertically and horizontally, and hence the water passes downwards through the radiator in straight lines. This arrangement of the tubes permits a freer water circula- tion, but is not so efficient, as far as cooling the water is concerned, as the staggered-tube assembly. The water spaces are about ^ inch in width and about 3 J inches deep, the individual tubes being about 4 inches long. In Fig. 12 is shown the appear- ance of a complete Fedders radia- FiG. 13 tor using the straight-line tube arrangement, the particular radiator illustrated being used in the Winton car. The radiator is supported on the side mem- bers of the frame by the two lugs a. Digitized by Google 16 AUTOMOBILE-ENGINE AUXILIARIES § 4 18. When hexagonal tubes are used in the construction of cellular radiators of the individual-tube tjrpe, these tubes are enlarged at the ends in the same manner as square tubes; the individual tubes are then nested, as is shown in Fig. 13, so that the tubes lie in horizontal rows. When thus nested, the water spaces, shown black in the illustration, between adjacent tubes in the horizontal rows are vertical, and a bet- ter water circulation is instu-ed than is possible if the tubes Fig. 1 are nested so they are staggered. As an inspection of Fig. 13 shows, a cross-section of the tubes greatly resembles a honey- comb; this resemblance has led to calling this type honeycomb radiators. Strictly, the term honeycomb radiator should be appjied only to those constructed with hexagonal individual tubes nested as shown; it is common practice, however, to apply the term to all cellular radiators. Digitized by Google § 4 AUTOMOBILE-ENGINE AUXILIARIES 17 19. Celltilar radiators in which the cells are formed by bending long strips of sheet metal, usually sheet copper or sheet brass, frequently have their cores made from strips bent as shown in Fig. 14 (a). These strips have a width equal to the desired depth of the radiator core, and are assembled as shown in (6), thus forming vertical water spaces ranging from A to t*^ inch in width and having a depth about J inch less than the depth of the core. The ends of the water spaces are closed by soldering. The construction shown is employed in the Mayo radiators. Pig. 15 Radiators constructed as shown in Fig. 14 naturally do not have 90 much cooling surface per tmit of area as cellular radi- ators with individual tubes, since there are no horizontal or inclined water spaces joining the vertical water spaces. 20. The radiator core used in the Livingston radiator is bent up from strips of sheet metal in such a manner,, and is so assembled that it overcomes the objection mentioned in Art. 19 ; in this radiator core, the water spaces surroimd the four sides of each cell, which is square in cross-section. Digitized by Google 18 AUTOMOBILE-ENGINE AUXILIARIES §4 The construction of the Livingston radiator core is illustrated in Fic^- 15- In view (a) is shown one of the strips from which from sheet copper having a art of each bend being oor- All horizontal bends are left / wide and narrow, so that shown in the cross-sectional them a water space through Bction of the arrows a. The y side, as shown in (6), which view clearly indicates that the four sides of each cell are surroimded by water. The ends of the water spaces are dosed by soldering, and the whole assembly is held together by solder. 21. Radiator Over- floWf Drain, Connec- tlonsy and Supports. Practically all modem radi- ators aie fitted with an overflow pipe that carries off surplus water, due either to filling the cooling system too full or to expansion of the water, and also any steam formed while the engine is in operation. The overflow-pipe location was explained in con- nection with Fig. 10, but is shown better at a, Fig. 16, which is a rear view of the Mayo radiator used in some Cole cars. 22. Provision for draining the radiator of all the contained water is usually made by fitting a drain cock 6, Fig. 16, to the bottom of the bottom tank, although in some cases, where part of the cooling system is located at a lower level than the bottom of the lower tank, the drain cock is applied to the lowest point of this part. Generally, the drain cock is located where it will surely drain the entire cooling system. Digitized by Google § 4 AUTOMOBILE-ENGINE AUXILIARIES 19 23* The top and bottom connections of the radiator to the inetallic pipes connected to the top and the bottom of the cylin- der water-jacket or water-jackets are always made by means of rubber-lined and rubber-covered hose that is fastened on by hose clips of the same form as those used with ordinary garden hose. The hose makes a flexible connection that pre- vents the transmitting of engine vibration to the radiator; likewise, the hose, being flexible, prevents tmdue stresses, such as those due to any swaying of the radiator or engine on account of distortion of the chassis frame in running the car over rough roads, from coming on the radiator. 24. Some radiators are supported by lugs incorporated in their construction. These lugs usually rest on the side members erf the frame, to which they are bolted. A fairly thick leather pad or a soft-rubber pad is usually inserted between the lugs and the frame to prevent vibrations from being trans- mitted to the radiator, which action would tend to destroy the soldered joints and thus cause the radiator to leak. Some manufacturers do not bolt the lugs tightly to the frame, but hold them by the pressure erf springs placed between the heads or nuts o! the holding-down bolts and the lugs or frame, thus forming a connection that can yield slightly if the frame is distorted. This is done in the model T Ford car, for instance. In many cases the radiator is set on top of a front cross- member of the frame and is bolted thereto by bolts c, Fig. 16, with a leather or rubber strip placed between the cross-member and the radiator. In most cars, the top of the radiator is prevented from sway- ing lengthwise of the car by running a brace rod from the rear of the top tank to the front of the dash. In Pig. 16, a bracket d is shown attached to the rear of the top radiator tank. This bracket forms part of the same casting containing the top radiator inlet pipe, and is used for attaching a brace rod run- ning to the dash. At ^ is shown the hood ledge, and at / a socket receiving the center hinge pin of the hood, which is usually made with three longitudinal hinges, one being in the center of the top and one at each upper comer of the radiator. Digitized by Google 20 AUTOMOBILE-ENGINE AUXILIARIES § 4 25. Circulating Pumps. — ^All pumps used on auto- mobiles for circulating the cooling water are probably of the rotary type, as distinguished from the reciprocating, or plimger, type. There are two general classes of rotary pimips; namely, the centrifugal and the positive, or fixed-wlufpte-per-revolution, class. Positive circulating pumps are either of the gear or the sliding'Vane type. 26. In Fig. 17 are shown two views of the centrifugal circulating pump used in the Studebaker "20*' car. View (a) Pig. 17 is taken from the front of the car, the front cover of the casing being taken oflf in order to show the inside of the pvmip; view (6) is a side view, the ptimp casing being shown in section. The pimip has a rotor a that is rigidly fastened to the driving shaft 6, which in this case is driven through a tmiversal coupling (not shown) from the cam-shaft of the engine. The rotor consists of two disks a' and a", between which are six curved vanes ai. These vanes are clearly shown in view (a), in which view the disk a' is removed in order to show the vanes. The Digitized by Google §4 AUTOMOBILE-ENGINE AUXILIARIES 21 two disks and the vanes of the rotor are cast in one piece. The rotor is enclosed in a housing c fitted with a removable cover d. The housing has a water inlet e connected to the bot- tom of the radiator, and a water outlet / leading to the bottom - of the cylinder water-jacket. The disk a" of the rotor is cut away at the center to admit to the inside of the rotor water that comes through the passage g connected to the inlet e. As the driving shaft 6 is turned in the direction of the arrow A, the rotor cairies the water around and dischai^es it from the outlet /, provided the passage outside the ptmip is open. The discharge of water is due to both the centrifugal action and the peripheral velocity of the water in the ptunp. To prevent leakage, the bearing through which the driving shaft h enters the pimip casing c has a stuflBngbox i that is packed with fibrous , packing, usually a prepared hemp packing. 27. A centrifugal piunp is not positive in its action; that is, it does not deliver a definite voltune of water per revolu- tion tmder all conditions. Thus, if by any mishap the water outlet is closed, the water in the pump will only be whirled around with the rotor. The pressure will not be much greater under this condition than when the pump is discharging at a moderate rate; it never becomes high enough to injure any properly constructed part. This fact has led to the almost universal adoption of the centrifugal ptunp for circulating the cooling water. The quantity of water that the pump wiU discharge per minute is in a measure proportional to the size, or resistance, of the external passage for a given speed. The qiiantity increases as the speed incieases. A centrifugal pump will continue to give fair service even after the parts are considerably worn. A loose fit between the edges of the vanes and the casing will allow some of the water to flow back toward the center of the pump, however, and the eddy currents thus set up will cause a loss of eflSiciency. By placing a disk on each side, or edge, of the vanes, so that the vanes are between the disks and connected to them, as in Fig. 17, the wearing surfaces are made qtiite durable. In Digitized by Google 22 AUTOMOBILE-ENGINE AUXILIARIES §4 cheap centrifugal pumps, the vanes project from the hub with- out a disk on either side of them. This fonn of centrifugal pump is the least dtirable and effident. ihown in diagrammatic form in extent for circulating the cooling of ordinary spiu* gears a enclosed outlet openings b and c opposite each other. One gear is driven by a shaft and transmits motion to its mate by means of the in- termeshing teeth. The directions of rotation of the gears and the divided path of the liquid are indicated by arrows. The teeth of the gears fit closely together so as to prevent any flow of liquid between them, and the ends of the gears fit snugly against the casing. A pump of this type delivers the same amoimt of liqtiid per revolution, whether the speed and pressure aie high or low. If a stoppage occurs in the pipes of a pump that is closely fitted, the pressure between the discharge side of the ptmip and the obstruc- tion will increase tmtil either the pump ceases to operate or some- thing breaks. A gear-pump oper- ations. water in the Peerless car use is I gears of the herring-bone tj^pe, „**.w* V.XV. WX.S,,,., ^. **t,. ^^ removed from the pump casing. The operation of the ptmip is the same as that of the gear- pvmip described in Art. 28 ; it is much more quiet in its action, however, as the heUcal gear-teeth slide into engagement with Digitized by Google §4 AUTOMOBILE-ENGINE AUXILIARIES 23 each other instead of roUing into engagement. To prevent breakage of any important part of the power plant that may be caused by a stoppage on the discharge side of the pump, the manufacturers of the Peerless car provide a safety coupling on the driving shaft of the pump, making this coupling so weak that it will break and thereby stop the ptmip before any more serious damage is done. Obviously, the car should not be operated when this safety coup- ling is broken. 30. On a number of cars, among which may be mentioned the Haynes and the Apperson automobiles, a so-called sllding- vane pump is employed for circulating the cooling water. A pump of this kind is shown in Fig. 20 (a). It is composed of a casing a, a piston 6, and two vanes, or wings, c and c' with springs d between them. The piston 6 is rotated by a shaft e, shown dotted, which is usually driven from either the engine cam-shaft or the magneto shaft; the piston b is concentric with pig. 19 the shaft e. The piston and the shaft are motmted eccen- trically in a circular machined chamber of the pump casing, as shown. The water coming from the radiator flows to the pump through a pipe connected at / and leaves through a pipe connected at g, which pipe, in turn, communicates with the bottom of the cylinder water-jacket or water-jackets. An inlet port h and an outlet port i are cut through the wall of the circular chamber of the casing. The two vanes c and c' are flat and free to slide in a slot machined directly across the piston; they are shown in perspective at {e). The one wing has driven in it two pins that enter corresponding holes in the second wing; when the two wings are assembled in the piston. Digitized by Google 24 AUTOMOBILE-ENGINE AUXILIARIES §4 each pin is surrounded by a spring, shown at d, view (a). A perspective view of the piston is shown at (d), in which view the slot previously mentioned can be clearly seen. A perspec- tive view of the casing is shown at (6), and of the cover that closes the casing at (c). The lowest part of the casing is fitted with a drain cock. The action of the pump depends on the motion of the vanes or wings, in the circular chamber of the casing. Suppose that the piston 6 is in the position shown in view (a) and that it starts to rotate in the direction of the arrow /. As soon as the vane c has covered the lower edge of the intake port A, it diives (e) (00 Pig. 20 the water in the crescent-shaped space between the piston b and casing a before it and out through the outlet port i. In the meantime, as soon as the vane c has covered the lower edge of the inlet port h, water is diawn through the port into the space behind the vane c until it has nearly reached the posi- tion of the vane c\ As soon as the vane c' passes the lower edge of the port h, it drives water before it and draws in water behind it; the two blades thus alternate in driving the water before them, thereby producing an almost continuous flow of water, 31. Antifreezing Mixtures for Cooling System. — If a car is to be used in very cold weather, it is advisable to fill the cooling system with some liquid that will not readily freeze. Digitized by Google §4 AUTOMOBILE-ENGINE AUXILIARIES 25 In weather not colder than l(f F. above zero, especially if a wind is blowing, it requires only a short time for watei to freeze in the radiator if the engine is stopped out of doors. The freezing may be prevented for a considerable time, how- ever, by covering the radiator with a blanket or a robe. Various substances may be mixed with water in order to lower its freezing point; those most commonly used are wood alcohol, denatured alcohol, calcitmi chloride, and glycerine. Grain alcohol that is not denatured may also be used, the only objection to it being its very high price. In emergencies, when none of the substances just named are obtainable, whisky, brandy, rum, gin, or any other equivalent Uquid very rich in alcohol may be added to the cooling water. TABLE I FREEZING POINT OF MIXTURES OF WOOD ALCOHOL AND WATER Percentage of Percentage of Freezing Point of Mixture Alcohol Water Degrees F. lO 90 18 above zero 20 80 5 above zero 25 75 2 below zero 30 70 9 below zero 35 65 15 below zero 50 50 35 below zero 32. Table I gives the approximate freezing temperatures for various proportions of alcohol and water. Alcohol vapor- izes and passes out of the cooling system more rapidly than does water. It is therefore necessary in order to maintain the proper proportions to add more alcohol than fresh water. The vapor of the alcohol is inflammable. Care should therefore be taken not to bring a naked light near the filler opening of the radiator when the filler cap has been removed. None of the alcohol solutions will injure rubber 01 attack the different metals in the cooling system. 33« Calciimi chloride {not chloride of lime) dissolved in water fonns a solution that will not freeze so rapidly as water Digitized by Google 26 AUTOMOBILE-ENGINE AUXILIARIES §4 e. Only chemically ptire calcium chloride should be used, 3ver. The impurities in ordinary commercial caldtun ride are apt to attack some of the metals or alloys of the ng system, especially zinc and solder. Table II gives the x)ximate freezing points of various proportions of calcium ride and water. rfore using a calcium-chloride solution it is advisable to e a test for acidity. This may be done by placing a strip lue litmus paper, which can be bought at any drug store, a sample of the solution. If this litmus paper turns red, TABLE n SZINO POINT OF HIXTUBES OF CALCIUM CHLOBIDB AND WATER alciiim Chloride per Gallon, 231 Cubic Inches, of Water Potmds Freezing Point Degrees F. I.O 27.0 above zero 2.0 18.0 above zero 30 1,5 above zero 3.5 8.0 below zero 4.0 17.0 below zero 5.0 30.0 below zero solution is acid and mtist not be used without first neutral- ly it. Neutralizing is done by adding slaked lime, a little L time, imtil a strip of blue litmus paper remains blue, iimi-chloride solutions are used very little at present. 34. Glycerine and water also form a mixttu-e that stays liquid at a lower temperature than water alone. The glycer- ine, however, attacks and destroys the rubber in hose connec- tions, etc. Instead of using a mixture of just these two liquids, alcohol is often added. The glycerine is liable to deposit on the walls of the cooling system if the cooling mixttu-e becomes very hot. Table III gives the approximate freezing points of various mixtiu*es of this kind. Digitized by Google §4 AUTOMOBILE-ENGINE AUXILIARIES 27 35. Draining tbe Cooling System. — If water alone is used for cooling during cold weather, it should be drained off completely when the car is left standing in a cold place over- night. No water should be allowed to remain in any pocket from which the water cannot drain as the radiator empties. Although nearly all modem cooling systems will drain per- fectly by gravity upon opening a drain cock located at the low- est point of the system, many of the older cooling systems will not. Some of these S5rstems cannot be emptied perfectly except by applying air pressure to the highest point. If avail- able, compiessed air from a storage tank should be used for TABLE in FRBBZ^O POINT OF MIXTURES OF GLYCERINE, ALCOHOL, AND WATER WOOD Percenta|;e of Glycerine Percentage of Wood Alcohol Percentage of Water Freezing Point Degrees F. 5.0 5.0 90 25 above zero 1 0.0 lO.O 80 15 above zero 12.5 12.5 75 8 above zero 15.0 15.0 70 5 below zero 12.0 25.0 63 10 below zero 20.0 20.0 60 23 below zero this purpose; otherwise, blowing into the system with the mouth or using a tire air pump will do. AIR COOLING 36. In order that a cylinder may be cooled sufficiently with air to keep the temperattu-e down to a working limit, it is necessary to provide a greater radiating surface with which the air can come into contact than is presented to the atmos- phere by a cylinder having a smooth exterior. The increased radiating surface is secured by placing projections on the parts of the cylinder that need the most cooling. These projections are usually in the form of fins, and may be either thin, flat 222B>-17 Digitized by Google 28 AUTOMOBILE-ENGINE AUXILIARIES §4 rings at right angles to the cylinder, or thin, flat strips placed radially and running lengthwise of the cylinder. In either case, the inner edge of the fins forms an integral or a substantially integral part of the cylinder casting. Other methods of form- ing an increased radiating surface, such as using radial pins either cast integral with the cylinder or substantially attached thereto, were formerly employed, but they have become obso- lete so far as pleasure automobiles are concerned. Under normal conditions of operation, the air-cooled engine runs much hotter than one cooled by water or some other liqtiid. It is not unusual for an air-cooled engine to become hot enough at the cylinder head and exhaust port to glow in the dark. Engines of this class have operated successfully for long periods at this high temperature. However, unless the fuel supply can be completely cut off, difficulty is some- times met in stopping engines when they are so hot. 37. There are three methods of bringing air into contact with the radiating surfaces of the cylinders. In the first method, the passage of the car through the air is relied on; in the second method, air is blown against the radiating sur- faces by a rotating fan; and in the third method, the parts with which the air is to be brought into contact are enclosed in a casing and a current of air is either forced through or drawn through the casing by means of a fan. A greater amount of air can be brought into contact with the radiating surfaces in this manner than when they are not enclosed by a casing. The air-cooling method first mentioned is used in the Duryea car. The second method has been used in the Cameron car, in some models of the Franklin cars, and in a number of other now obsolete pleasure cars. The method in which air is forced by a fan or a blower through a casing sunoimding the cylinders has been used on the Frayer-Miller cars. 38. In the Franklin air-cooled automobiles, there is em- ployed the variation of the third method mentioned in Art. 37 in which air is drawn through a casing surrounding the cylin- ders. This system, as carried out in the Franklin six-cylinder cars, is illustrated in Fig. 21, where some of the parts of the Digitized by Google § 4 AUTOMOBILE-ENGINE AUXILIARIES 29 car are cut away in order to show the cooling system more clearly. Each cylinder of the engine has vertical thin metal fins, or flanges, that are cast in the cylinder walls; also, each engine cylinder is surroimded by a short cylindrical sheet- metal air jacket a that is open at the top and the bottom. These air jackets are set through a horizontal metal deck b that touches the front of the dashboard c and is touched by a ledge on the sides of the hood d. A vertical sheet-metal shield e reaches from the front of the horizontal deck 6 down- PlG.21 wards to the front cover of the engine boot, or sod pan, /, which is open at the rear. The space under the hood is thus divided into two compartments by the horizontal deck b and the ver- tical shield e; the upper compartment is in communication with the outer air through a large grilled opening d' in the front of the hood, the griUe-work being formed from flat strips of metal. The flywheel g of the engine is a suction fan. It draws air through the opening in the front of the hood into the upper air compartment and thence down through the air jackets Digitized by Google 30 AUTOMOBILE-ENGINE AUXILIARIES § 4 of the cylinders into the lower compartment, discharging the air through the rear end of the sod pan /. The air in passing over the cooling flanges of the cylinder walls cools these walls by absorbing heat and carrying it away, the course of the air being clearly shown by the arrows in the illustration. EXHAUST MUFFLERS PURPOSE OF MUFFLING 39. Gases exhausting Unrestricted from the cylinder of an internal-combustion engine pass into the atmosphere at a high velocity, so high, especially at high engine speeds, that the result is a continuous noise that can be likened to a series of sharp detonations. This noisy exhausting of the gases is decidedly objectionable, and for this reason many efforts have been made by inventors to produce a device that will muffle the detonations to a degree that will render them unobjection- able. The device used for this purpose is called an exhaust muffler. Generally, the exhaust may be muffled by leading the exhaust gases into a chamber, or chambers, where they can expand to a low pressure and cool at the same time. In most mufflers, the single large stream of exhaust gases coming from each cylinder is broken up into numerous small streams, or thin sheets, to insure rapid cooling and reduction in velocity. In some mufflers, the cooled exhaust gases are discharged into the atmosphere in a series of fine streams, and in others, especially the most modem mufflers, the discharge is in a single stream. It is common practice either to place a valve of some suitable form between the muffler and the engine, or to incorporate a valve directly with the muffler, the valve being operated by a conveniently located foot-pedal. This valve, known as the muffler cut-out, opens directly to the atmosphere, and when open, it allows the engine to exhaust directly into the air, either for testing the regularity of the explosions or to gain a Digitized by Google § 4 AUTOMOBILE-ENGINE AUXILIARIES 31 sUght increase of power by eliminating the back pressure created by the mtiflfler. A good muflBier, in eff ectivdy muflBing the sound of the esca- ping exhaust gases, will not create an excessive back pressure on the engine. CONSTBUCnON OP MUFFLERS 40. Fig. 22 illustrates in section a typical modem exhaust muflBer of the type that breaks up the exhaust gases into ntuner- ous fine streams. It has two cast-iron heads a and 6, and four concentric cylindrical shells c, d, e, and / that are held in position by grooves in the two heads. The assembly is held together by long bolts that pass through both heads. The exhatist pipe g is attached to the head a and discharges into the inside of the shell c. The gases pass through small perforations at the left end of the shell c into the larger shell d, expanding in doing so, because the volume of the shell d is much larger than that of the shell c. The gases in the shell d 7 Fig. 22 pass through perforations at the right end of this shell and expand into the shell e. Then they pass through holes in the left end of the shell e into the outer shell /, expanding therein and, finally, they escape into the atmosphere through the nozzle h. This type of muffler has a cut-out valve i fitted into the head 6. This valve is opened by pulling on a cable attached to the cut-out lever /, when the exhaust gases can pass from the exhaust pipe g through the inside shell c and the openings in the valve seat of i into the atmosphere. 41. The muffler used in many Stevens-Duryea cars belongs to the type that breaks the solid stream of exhaust gases into thin sheets; it is shown disassembled in Fig. 23. It has an Digitized by Google 32 AUTOMOBILE-ENGINE AUXILIARIES §4 outer shell a that is closed, when assembled, by the heads b and c. The head b is fitted with a cut-out valve J, and to this head is connected the exhaust pipe. Placed inside of the shell a Pig. 23 is a'series of cones e and /. The cones e aie closed at the apex and the cones / have the apex open; that is, they are really frustums of cones. These sheet-metal cones are held in place by three supporting shafts g and tubular distance pieces h. The exhaust gases on entering the mufHer strike the first closed cone e and pass over its inside surface up to its edge; they then pass over the outside surface into the cone /, which delivers the gases into the inside of the second closed cone e; and so on. The gases finally escape through a passage in the head c into a tube and thence into the atmosphere. 42. Fig. 24 illtistrates, in longitudinal and in cross-section, a muflBer of the type that breaks the exhaust gases into numer- ous small streams. In this form of muffler there are six cylin- drical steel shells, three of which are placed eccentric to the Fig. 24 center of the muffler. The exhaust gases enter the central chamber a of the muffler, and pass through perfoiations at the top to the first expansion chamber formed by the anntilar Digitized by Google §4 AUTOMOBILE-ENGINE AUXILIARIES 33 space between the first and second shells. The gases pass through perforations in the bottom of the second shell into the second expansion chamber, and leave this through perfora- tions in the top of the third shell, entering the third expansion chamber, and so on. The gases finally leave the mufSer through the exhaust port b and pass into the atmosphere. 43. Mufflers are liable to fill gradually with soot (loose carbon). For this reason, they should be taken apart occa- sionally and cleaned. When a muffler is apart, the shells or cones, especially those which first receive the exhaust gases, should be examined for corrosion. If a cut-out valve is incor- porated in the muffler, it also should be cleaned and examined, and, if necessary, repair should be made. MUFFLER CUT-OUTS 44. Although many cars are fitted with a muffler cut-out, there are some that are not provided with this device. To meet the demand of owners who desire to place a muffler cut- out on the exhaust pipe, nimierous cut- out devices have been placed on the market. Some of them can be applied with very little labor. 45. Fig. 25 illus- trates a form of muf- fler cut-out that will open automatically if an explosion occurs in the muffler, thus acting as a safety Fig. 25 valve. It consists of a T-shaped body a that is threaded internally at b and c to fit threads cut on the exhaust pipe. At d is formed a valve seat that is normally closed by the valve e, which is held to its seat by a spiing /. A light wire Digitized by Google 34 AUTOMOBILE-ENGINE AUXILIARIES §4 cable is attaxiied to the lever g. When this cable is ptilled in the direction shown by the arrow, the valve e is pushed away from its seat d and a direct passage to the atmosphere is pro- vided for the exhaust gases. If at any time the pressure in the exhaust pipe is great enough to overcome the tension of the spring/, the valve e will automatically open outwards. Fig. 26 46, The form of muffler cut-out illustrated in Fig. 26 is intended to be clamped to the exhaust pipe after cutting a V-shaped notch into this pipe. For this purpose the body a is made in halves. The cut-out valve 6, which is a butterfly valve, is fastened to a shaft c. This shaft also carries a crank d that serves to turn the valve 6, which is shown in its open position. GOVERNING DEVICES GOVERNING BY HAND OB FOOT 47, Most automobile engines are controlled by manipu- lation of the throttle valve and the position of the spark. More accurately, the control proper is accomplished by regulation of the throttle, and the spark advance is regulated to keep the ignition at its most advantageous point for developing the maximum power of the charges received. Digitized by Google § 4 AUTOMOBILE-ENGINE AUXILIARIES 35 The maniptilation of the spark alone is sometimes, but wrongfully, employed to modify the speed of the engine, because, with the spark retarded to cause ignition to occur later than it should, the power of the engine is very mate- rially reduced. This, is a most objectionable practice for sev- eral reasons: In the first place, it evidently wastes gasoline, because the same result as r^ards power may be obtained with smaller charges and an earlier spark. Second, the inflam- mation is so prolonged that it probably is not completed at the time the exhaust valves open, so that the valve seats are exposed to streams of gas still btuiiing. This not only over- heats the valves and is liable to warp them, but it soon bums and cuts their ground faces and their seats. Third, the engine is overheated, and preignition of the incoming charge may result, producing explosions in the carbureter and intake pipe. It is, however, pennissible to retard the spark to prevent racing, that is, running too fast, when the throttle is nearly closed and the engine is running light, with the car standing still. 48. Inasmuch as automobile engines are operated under wide variations of speed and load, it follows that for correct action the throttle and the spark cannot always be operated together. For example, a rarefied charge, such as is obtained with the engine running at meditmi speed, with the throttle nearly closed, will bum in a comparatively slow manner and requires an advanced spark for its prompt combustion. Sup- pose, now, that the car is running at moderate speed tmder these conditions, as it may when descending a slight grade, or even on level ground. If a slight up-grade is encountered, the oper- ator will open the throttle to increase the power. Under such conditions the speed of the engine will probably not increase, but it will be found that the spark advance suitable for the pre- vious conditions is too early for the increased charges. This will be indicated by the laboring soimd and possible pounding of the engine, either of which sounds may be stopped at once by slightly retarding the spark. 49. The manipulation of the throttle valve is eflfected either by means of a hand throttle lever carried as a general Digitized by Google 36 AUTOMOBILE-ENGINE AUXILIARIES § 4 rule at or near the top of the steering-gear column, or by a foot throttle lever moiinted