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K.F. WENDT LIBRARY UW COLLEGE OF ENGR.
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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
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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
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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
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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
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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
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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
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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
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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
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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
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222B— a
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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
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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
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§ 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
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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.
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§ 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
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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
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§ 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.
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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
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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
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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
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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
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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.
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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
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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.
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Summed up briefly, the arrangment of the driving mechanism is as follows: The engine and the clutch form a unit that
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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.
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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.
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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
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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.
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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
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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
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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
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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
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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.
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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.
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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
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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
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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.
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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
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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).
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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).
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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.
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41.' An ordinary folding wind sMeld attached to the dash of a touring car is shown in Fig. 19 (fe). This syle of
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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
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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
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§ 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.
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'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
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§ 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
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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
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§ 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
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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.
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§ 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
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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.
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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
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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
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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
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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
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§ 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
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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.
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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. .
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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.
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§ 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.
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Q; nfiiiiniiiiii'aiimHiiiiiiij QaOiE
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§ 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
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60
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§ 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-
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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.
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§ 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
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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
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§ 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
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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.
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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
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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.
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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
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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
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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
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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.
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[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
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§ 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.
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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
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§ 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
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§ 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
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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
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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
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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
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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
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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
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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
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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
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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.
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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
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§ 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
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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
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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
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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
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§ 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.
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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
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§ 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'-«
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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.
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Pig. 43
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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
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§ 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).
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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
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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
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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
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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.
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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.
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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
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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
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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
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i
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§ 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.
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Pig. 2
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§ 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
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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
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§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
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-
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§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.
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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
11
Digitized by
: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
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§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
^
s:
^
14
Digitized by
§ 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
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.
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§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
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
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§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
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-
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§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