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THE GASOLINE AUTOMOBILE
PUBLISHERS OF BOOKS F O R_^
Coal Age ^ Electric Railway Journal
Electrical World v Engineering News-Record American Machinist v The Contractor Engineering 8 Mining Journal ^ Power Metallurgical 6 Chemical Engineering Electrical Merchandising
Geo. B. Selden in his "Benzine Buggy.'
The present day motor car.
(frontispiece)
ENGINEERING EDUCATION SERIES
THE GASOLINE AUTOMOBILE
PREPARED IN THE
EXTENSION DIVISION OF THE UNIVEESITY OF WISCONSIN
BY GEORGE W. HOBBS, B. S.
INSTRUCTOR IN MECHANICAL ENGINEERING IN TH1
UNIVERSITY EXTENSION DIVISION, THB
UNIVERSITY OP WISCONSIN
BEN G. ELLIOTT, M. E.
I PROFESSOR OF MECHANICAL ENGIN THB UNIVERSITY OF NEBRASKA
FIRST EDITION EIGHTH IMPRESSION
TOTAL ISSUE, 18,000
McGRAW-HILL BOOK COMPANY, INC.
239 WEST 39TH STREET. ^ NEW YORK
LONDON: HILL PUBLISHING CO., LTD. 6 & 8 BOUVERIE ST., B. C.
1915
COPYRIGHT, 1915, BY THE MCGRAW-HILL BOOK COMPANY, INC.
PREFACE
The purpose of this book is admirably expressed in the following quotation taken from the Buick instruction book: "To derive the greatest amount of satisfaction and pleasure from the use of his car the driver should have a complete understanding of the mechanical principles underlying its operation. Merely knowing which pedal to press or which lever to pull is not enough. The really competent driver should under- stand what happens in the various parts of the car's mechanism when he presses the pedal or pulls the lever. He should know the cause as well as the result."
When we consider the complexity of modern automobiles from a mechanical standpoint, with the duties that are required of them, together with the fact that the great majority of them are operated by men with little or no experience in the handling of machinery, the automobile stands as one of the most remarkable machines that the ingenuity of man has ever produced. The operating expense of the automobile has already assumed a large place in the budget of the American people. Although it is so built that the owner may secure good service from his automobile with very little knowledge of its construction, still it is evident that an intimate acquaintance with its details should enable him to secure better service at less expense and at the same time to prolong the useful life of the car.
It is with the hope of increasing the pleasure of automobile ownership and reducing the trouble and expense of operation that this book is offered. It is planned primarily for use in the University Extension work in Wisconsin, for the instruction of those who drive, repair, sell, or other- wise have to do with motor cars. It is largely the outgrowth of a series of lectures on the subject which were given in twenty-three cities of Wisconsin during the past winter.
The thanks of the authors are especially due to Mr. M. E. Faber of the C. A. Shaler Co. for assistance in preparing the section dealing with tire troubles, to Prof. Earle B. Norris for much of the chapter on Engines and for editing the manuscript and reading the proof, and to the many manufacturers who have liberally assisted in the preparation of the work by supplying their cuts and other material.
G. W. H. MADISON, Wis., Sept. 15, 1915.
vu
CONTENTS
CHAPTER I GENERAL CONSTRUCTION
ART. PAGE
1. The steam propelled car 1
2. The electric car 1
3. The gasoline car 2
4. Types of cars 2
5. The chassis 2
6. The frame . 6
7. The springs 6
8. The front axle : 8
9. The steering gear 10
10. The rear axle 12
11. The differential 13
12. The power plant and transmission 14
13. The torque arm 15
14. Strut rods 16
15. Brakes 16
16. Wheels 18
17. Tires 19
18. Rims 20
19. The speedometer drive 21
20. Control systemr 23
CHAPTER II
ENGINES
21. What is an explosion? 25
22. Cycles 25
23. The four-stroke cycle 26
24. The order of events in four-stroke engines 27
25. The mechanism of four-stroke engines 28
26. Valve timing and setting 29
27. Valves 30
28. Valve arrangements 33
29. The Knight engine 34
30. The rotary valve 34
31. Two-stroke engines 35
32. The flywheel 38
33. Ignition .39
34. Clearance and compression ' 39
35. Piston displacement 39
36. Cylinder cooling 40
37. The muffler • 40
38. Horse power of engines 41
ix
x CONTENTS
CHAPTER III POWER-PLANT GROUPS AND TRANSMISSION SYSTEMS
39. Single- and multi-cylinder engines 43
40. Power plant and transmission arrangements ". . . . 44
41. Modern automobile power plants 50
42. Constructional features of four- and six-cylinder engines 56
43. Eight- and twelve-cylinder power plants 60
44. Clutches 64
45. Change gear sets 66
46. Planetary gearing 67
47. Universal joints and drive shaft 69
48. Final drive 70
49. Types of live rear axles 71
CHAPTER IV FUELS AND CARBTJRETTING SYSTEMS
50. Hydrocarbon oils 75
51. Fractional distillation of petroleum 75
52. Principles of vaporization 76
53. Heating value of fuels 79
54. Gasoline gas and air mixtures 79
55. Principles of carburetor construction 79
56. Schebler, model L carburetor 82
57. Schebler, model R 84
58. The Holley model H carburetor 86
59. Holley model G 87
60. Stewart model 25 89
61. Kingston model L 90
62. Marvel carburetor 91
63. Stromberg, model H 94
64. Zenith model L 94
65. Rayfield model G 95
66. Carter model C 97
67. General rules for carburetor adjustment 98
68. Carburetor control methods 99
69. The gravity feed system 99
70. The pressure feed system 100
71. The vacuum feed system 100
72. Intake manifolds 102
73. Care of gasoline 102
CHAPTER V LUBRICATION AND COOLING
74. Friction and lubricants 103
75. Cylinder oils 104
76. Viscosity 104
CONTENTS xi
AET. PAGE
77. Flash point 104
78. Fire test and cold test 104
79. General notes on lubrication 104
80. Splash system of engine lubrication 106
81. Splash system with circulating pump 106
82. Full forced feed system Ill
83. Mixing the oil with the gasoline 113
84. Selection of a lubricant 113
85. Directions for lubrication 114
86. Cylinder cooling 117
87. Water cooling systems 117
88. Air cooling 122
89. Cooling solutions for winter use 123
CHAPTER VI
BATTERIES AND BATTERY IGNITION
90. Fundamental electrical definitions 127
91. Direct and alternating current 127
92. Dry batteries 128
93. Storage batteries 128
94. Series and parallel connections 129
95. Battery connections for ignition purposes 130
96. Simple battery ignition system 130
97. The three terminal coil 132
98. Timers 135
99. Spark plugs 135
100. Master vibrators 136
101. The high tension distributor system 137
102. The Connecticut automatic ignition system 139
103. The Atwater Kent system 141
104. The Westinghouse ignition system 144
105. The Delco system of ignition 147
106. The Remy-Studebaker ignition system 149
107. Spark advance and retard 151
108. Automatic spark advance 151
CHAPTER VII
MAGNETOS AND MAGNETO IGNITION
109. Principles of magnetism : 153
110. Mechanical generation of current 155
111. Low and high tension magnetos 156
112. Armature and inductor types 156
113. Remy model P magneto 157
114. The Connecticut magneto 160
115. Dual ignition systems 160
116. Eisemann high tension dual ignition 161
117. Eisemann automatic spark control 163
118. The K-W high tension magneto 163
rii CONTENTS
ABT. PAGS
119. The Dixie magneto 16f>
120. The Bosch high tension magneto 167
121. The Bosch dual system 170
122. Bosch two-independent system 173
123. The Ford magneto and ignition system 174
124. Magneto speeds 175
125. Timing the magneto 176
126. Battery vs. magneto ignition 177
127. General suggestions on magnetos 177
128. Common magneto ignition definitions 177
CHAPTER VIII STARTING AND LIGHTING SYSTEMS
129. Starting on the spark 179
130. Mechanical starters 180
131. Air starters 180
132. Acetylene starters 180
133. Electric starters 181
134. Storage batteries 181
135. Battery charging • 185
136. Wiring systems 187
137. The Ward-Leonard system 187
138. The Delco system 190
139. Gray and Davis starting and lighting systems 193
140. Wagner starting and lighting system 197
141. The Westinghouse single-unit system 199
142. Westinghou.se two-unit system 200
143. The U. S. L. electric starting and lighting system 204
144. Jesco single-unit electric starter and lighter 205
145. Care of starting and lighting apparatus. 207
146. Starting motor troubles 208
147. Generator troubles 209
148. Battery troubles 209
149. Winter care of batteries 209
150. "Don'ta" on starting equipment 210
CHAPTER IX
AUTOMOBILE TROUBLES AND REMEDIES
151. Classification of troubles 213
152. Power plant troubles 214
153. Mechanical troubles in engine 216
154. Carburetion troubles 221
155. Ignition troubles 223
156. Lubricating and cooling troubles 226
157. Starting and lighting troubles 228
158. Transmission troubles 228
159. Chassis troubles . . 229
CONTENTS xiii
CHAPTER X OPERATION AND CARE
ART. PAGE
160. Preparations for starting 231
161. Cranking 231
162. How to drive 232
163. Use of the brakes 233
164. Speeding 234
165. Care in driving 234
166. Driving in city traffic 235
167. Skidding 236
168. Knowing the car 237
169. The spring overhauling 238
170. Washing the car 240
171. Care of tires 240
172. Tire troubles 243
173. Figuring speeds 247
174. Interstate regulations 248
175. Canadian regulations 249
176. Touring helps-route books 250
177. Cost records 250
INDEX . . 255
THE GASOLINE AUTOMOBILE
CHAPTER I GENERAL CONSTRUCTION
Automobiles may be classified according to the type of power plant used, as steam, electric, and gasoline; or they may be divided into two classes according to use, as pleasure cars and commercial cars.
1. The Steam Propelled Car. — The steam engine has the advantage of -flexibility. All operations such as starting, stopping, reversing, and
acquiring changes of speed can be done directly by throttle control. By opening or closing the throttle, more or less steam is supplied to the engine, and the power is increased or decreased in proportion. When climbing a hill, all that is necessary to do is to give the engine more steam and consequently more power. The advantage of the steam engine in being able to start under load eliminates the clutch and also the trans- mission or change speed gears, the engine being connected directly to the rear axle.
The disadvantage of the steam engine is that it is necessary to fire up before starting, in order to generate enough steam to run the engine and propel the car. The steam machine requires large quantities of water to form the steam and that means frequent refilling of the water tank. They also require constant attention to the water and fuel pumps. The burning of the fuel under a boiler to generate the steam introduces an element of danger from fire and also makes the steam plant less efficient than the internal combustion engine.
2. The Electric Car. — The advantages of the electric car are similar to those of the steam car inasmuch as it is very flexible and can be controlled entirely by the controlling levers. By cutting out or in resistance, more or less current is supplied to the motor and the power of the motor is proportional to the flow of the current. The electric car is especially adapted to the use of women and children in cities. It is easy riding, clean, and very quiet.
The disadvantages are that it is not suitable for long drives, heavy roads, or hilly country. On one charge of the battery the average car will run from 50 to 100 miles^ ^depending on the speed and condition of the roads. If the car is run at high speed, the battery will not
1
2 THE GASOLINE AUTOMOBILE
drive the car as far as it will when running at moderate rate. This car is also limited to localities where there are ample facilities for charging the storage batteries.
3. The Gasoline Car. — The gasoline engine is much more economical than either the steam or electric, and after being once started has great flexibility. It is also better adapted for touring purposes than either of the others and does not require any more attention from the operator. The average car carries enough fuel to run it 200 to 400 miles without a stop and then it is necessary to fill the gasoline tank only, with an occasional quart or two of water for the radiator. With proper care, the engine will run as long as the gasoline supply and electrical system will hold out.
The disadvantages of the gasoline engine as compared with the steam engine or electric motor are, first, the gasoline engine is not self-starting; and, second, it lacks overload capacity. This means that some method of changing the speed ratio of the engine to the rear wheels is necessary in order to acquire extra power for climbing hills, for heavy roads, and also for reversing the car, as it is not possible to reverse the ordinary four- stroke automobile engine. The gasoline engine will not start under load, which necessitates the use of a clutch, so that the engine can be started and speeded up before any load is thrown on. Apparently there are a great many disadvantages to the gasoline engine but in reality they are very few, for with the proper handling of the spark and throttle control- ling levers it is not necessary to keep continually changing gears. The speed change lever need not be used except for starting, stopping, hill* climbing, and on bad roads.
4. Types of Cars. — In general, the parts of the pleasure and commercial cars are the same except that the pleasure cars are built much lighter than the commercial cars. In the pleasure car everything is planned for comfort and speed, while the commercial car is built for heavy loads and is generally intended to be driven at low speed.
The principal body types of pleasure cars are, the limousine, the touring car, the coupe, and the roadster, as shown in Fig. 1.
The commercial cars are built for light, medium, and heavy duty. A few of the commercial types are shown in Fig. 2.
The cycle car is a name commonly given to small cars which have less than 70 cu. in. piston displacement or a tread of less than 56 in.
5. The Chassis. — The principal parts of the gasoline automobile are the frame, springs, axles, wheels, power plant and auxiliaries, clutch, transmission system, controlling apparatus and body. The chassis, as shown in Fig. 3, includes all parts with the exception of the body and its accessories. The functions and types of these parts will be taken up separately.
GENERAL CONSTRUCTION
THE GASOLINE AUTOMOBILE
JLJLJ
HEAVY TRUCK
LIGHT TRUCK
MEDIUM TRUCK
2.— Types of commercial canp,
GENERAL CONSTRUCTION
Radiator
Power plant -Clutch •Universal joint
-Control levers -Drive shaft
Torque crrm-
or Torque rod
Muffler
Brake equalizers 3 rake
-Storage baffery
mmmm Universal joint
Change aears Brakes
FIG. 3.— Chassis of the Studebaker "Six.
6 THE GASOLINE AUTOMOBILE
6. The Frame. — The automobile frame is a very important part of the car, due to the fact that it supports the power plant, transmission mechanism, body, etc. The frame is attached to the springs, which in turn are fastened to the axles. Frames are made either of wood or metal .or a combination of the two. The metal frames are usually of channel- section steel. The wooden frames may be either of the solid timber type or of laminated strips glued together and sometimes reinforced by steel strips. This type is very strong and light and does not transmit so much
FIG. 4. — Channel steel frame.
of the vibration as the steel frame. Figure 4 shows a pressed steel channel- section frame. Figure 5 shows a frame made from second-growth ash and used on the Franklin car.
7. The Springs. — The frame of the automobile is supported by laimated leaf springs. Coil springs are used only in places where a great deal of strength is needed in a small space and where quick action is required. The springs under the frame of an automobile must be gradual
FIG. 5. — Franklin wood frame construction.
and easy in their action, and this is why the laminated leaf spring is used. The strength and resilience of the leaf spring can be varied by changing the number of leaves or by varying the width or length of the leaf. It also has an advantage over the coil spring in that if one leaf breaks the spring is still serviceable, while in a coil spring if a coil breaks the spring is no longer of any use.
The laminated spring is built up of a number of leaves varying in length, the longest leaf being on the concave side of the spring and the
GENERAL CONSTRUCTION
g THE GASOLINE AUTOMOBILE
other leaves built on this one in the order of their length. The ends of the long leaf are bent around to form eyes so that they can be fastened to the frame by a clevis or other means.
The laminated leaf springs, as shown in Fig. 6, are built in the follow- ing forms: cantilever, semi-elliptic, three-quarter elliptic, full-elliptic, and platform springs.
The Cantilever spring is fastened flexibly to the frame at one end and the center and carries the axle at the other end. There is another type of (jantilever spring which has a single rigid fastening to the frame. This is also called a quarter-elliptic spring.
The (semi-elliptic spring usually has its center fastened to the axle while thl two ends support the frame. This type of spring is generally used to ^upport the front end of the car, because this type has the least amount of side-sway. Since the front axle is used for steering purposes, a great amount of flexibility is not desired.
The three-quarter elliptic spring consists of a semi-elliptic member, to one end of which is attached a quarter-elliptic member. This type is supported in the middle of the semi-elliptic spring and is connected to the frime at one end of the semi-elliptic and the free end of the quarter- elliptic sbrings.
The ifull-elliptic spring consists of two semi-elliptic springs con- nected together at the end, supported at the middle of one semi-elliptic and carrying the load at the middle of the other. Either the three- quarter or the full-elliptic types have greater flexibility than the semi- elliptic tiype.
The platform spring consists of three semi-elliptic springs fastened together. Two of the members are parallel to the sides of the car arid the third is inverted and is parallel to the cross members. The car frame is attached to the front end of the side members and to the middle of the cross member. The middle of the side members rests on the spring
8. The Front Axle. — The front axle consists of the center, the knuckles, a steering arm, a third arm, a plain arm, and the tie rod. The centers are either I-beam, as shown in Fig. 7 or tubular as in Fig. 8, and they may be either straight or dropped center types. Square centers are sometimes used on heavy trucks.
The }-beam centers are made either of drop forgings or of cast steel and are heat-treated to do away with brittleness and give strength and toughness. The tubular centers and tie rods are made from the best high-grade seamless steel tubing and the yokes are either pinned or brazed on the ends of the tubes. In the I-beam centers the yokes form a part of the forging or casting. The I-beam construction is the strong- est but is not quite so flexible as the tubular center.
GENERAL CONSTRUCTION 9
The front wheels are fastened on the spindle of the knuckle and run on cup-and-cone ball bearings or on roller bearings as shown in Fig. 7. The spindle is set so that the front wheels have a camber of about 2 in., that is, the tops of the wheels are about 2 in. farther apart than the
FIG. 7. — I-beam front axle construction.
bottoms of the wheels. This is to conform to the crown of the road and to bring the point of contact between the tire and the road in line with the king-bolt.
In order to make the car steer easier and have a tendency to run straight ahead, the front wheels should toe in from % to ^ in. This is done by adjusting the length of the tie rod.
FIG. 8. — Tubular front axle.
The knuckles are fastened in the axle yokes by king-bolts and are free to swing about 35° either way from the center line of the axle. This is necessary in order to allow the wheels to follow a curve when turn- ing. Between the top of the axle yoke and the knuckle there should
10
THE GASOLINE AUTOMOBILE
be a ball or roller bearing or a renewable bronze washer to carry the load and yet allow the knuckle to turn easily.
The king-bolt should fit in a bronze bearing in order to insure easy movement and a small amount of wear. The steering and third arms, which are generally combined in a single forging, are keyed to one knuckle. The third arm is connected by the tie rod to the plain arm, which is keyed to the other knuckle. The general layout of the steering apparatus is shown in Fig. 9. The steering arm is connected by the drag link to the pitman arm or steering lever on the base of the steering
gear.
Steerinq wheel
Sfeer/na column -:
« Pitman arm —-Drag link
Fig. 9. — Arrangement of steering apparatus.
9. The Steering Gear. — The steering gear is the part of the mechan- ism that operates on the knuckles to turn the front wheels in response to movements of the hand wheel.
Figure 10 shows the essential parts of a double worm steering gear. Inside the steering column is the steering tube, the upper end of which is connected to the hand wheel while the lower end carries a double- threaded worm. The worm meshes with two half-nuts, one with a right- hand and the other a left-hand thread. Two rollers, which are attached to the yoke that operates the pitman arm or steering lever, bear against the lower ends of the half-nuts. The operation is as follows: Turning the hand wheel turns the tube and worm in the same direction, which causes one half-nut to rise and the other to descend. This pushes one roller down and lets the other rise. The yoke is given the same motion
GENERAL CONSTRUCTION
11
and transmits it to the pitman arm, which pushes or pulls on the drag link and thus turns the knuckle and wheels.
Sector
Spark lever / Throttle, lew
X js'
rod
—Stationary tube
•Throft/e fube
"•Adjusting nut — Grease plug
, Throttle gear
— - -fy&r/c a ear
FIG. 10. — Double worm steering mechanism.
Figure 11 shows the worm-and-gear type. The worm is fastened to the steering tube and is turned with the hand wheel. The gear shaft carries the pitman arm, which connects to the knuckle steering arm by the drag link.
12 THE GASOLINE AUTOMOBILE
These steering gears are non-reversible, because while the action of the hand wheel is readily transmitted to the front wheels the jarring of the front wheels on rough roads can not be transmitted back to turn the hand wheel.
Grease Cup Worm
Gear
FIG. 11. — Worm-and-gear steering mechanism.
10. The Rear Axle. — The rear axle must carry this end of car and also provide means of giving power to the rear wheels to propel the car. This is done in two general ways, and the corresponding types of axles are called "dead" and "live" axles.
Figure 12 shows a truck chassis with a dead rear axle. It is somewhat similar in construction to the ordinary wagon axle, as it is made up of a
FIG. 12. — Heavy truck, chassis with dead rear axle.
solid bar with spindles machined on the ends for the wheel bearings. The wheels have large sprockets on the inside which are driven by chains from other sprockets on the ends of a "jackshaft" near the middle of the car. This type of axle is used principally on heavy trucks where it is
GENERAL CONSTRUCTION 13
necessary to have a solid construction and provide for a large reduction in speed.
For pleasure cars, the live axle is generally used. The general arrangement of a car with a live axle was shown in Fig. 3. In Fig. 13 is shown in detail the construction of a typical live axle. In this type the axle turns and drives the rear wheels with it. The axle is surrounded by a stationary housing which supplies the bearings for the wheels and the axle and which also supports the car through the springs. The live axle receives its power near the center, usually through a set of bevel gears which give the desired speed reduction and also make the necessary right angle change in the power transmission.
BE4R/NG5
DffUM
FIG. 13. — Live rear axle.
11. The Differential. — Some provision has to be made to drive the rear wheels positively in either direction and yet allow one wheel to run ahead of the other when turning a corner. This is done by dividing the live rear axle at the center and connecting the two halves by a differential gear, the details of which are shown in Fig. 14. Each half of the live axle (called the main shaft in Fig. 14) has a bevel gear on its inner end. These bevel gears face each other and are called the differential gears. They are connected by from two to four differential pinions spaced at equal distances around the circle. The power is applied at the centers of these differential pinions so that they act like the doubletrees or eveners on a team of horses, allowing one wheel to run ahead of another or to lag behind but still maintaining an even pull on the two differential gears. Referring to Fig. 14, the power from the engine is brought back to the driving, pinion and this delivers it to the large gear called the bevel ring. This bevel ring is fastened to the differential case, which, therefore, receives the power from the bevel ring. The differential case turns the spider with it and, as this spider carries the differential pinions, these pinions are carried around with a force applied at their centers. On a
14
THE GASOLINE AUTOMOBILE
straight road the differential case, the spider, the differential pinions and the differential gear all revolve as one mass and there is no internal action in the differential. The differential pinions pull equally on the two differential gears on each side of them and they all revolve together. In
FIG. 14. — Differential gear.
turning a corner the outer wheel has farther to go and hence must run faster. This makes the one differential gear turn faster than the other. This causes the differential pinions to revolve on their axes, but they still continue to deliver power equally to the two wheels.
FIG. 15. — Arrangement of power plant and transmission system.
12. The Power Plant and Transmission'.— Figure 15 shows a typical arrangement of the power plant and the power transmission system. The engine is generally placed in the front end of the car, both for ac- cessibility and to balance the weight of the passengers in the rear part
GENERAL CONSTRUCTION 15
of the car. The engine is the most important part of the car. Its purpose is to transform the heat energy of gasoline into mechanical energy at the crank shaft for the purpose of driving the car. The power is delivered to the flywheel, from which the clutch takes it and passes it back to the transmission. In the transmission case is a system of gears for reducing the speed from the engine and increasing the turning force for starting purposes or for heavy driving, as in sand or on hills.
The power plant is mounted on the frame of the car, while the rear wheels which are to finally receive and use the power are flexibly con- nected to the frame by springs. We must, therefore, have a flexible arrangement for taking the power from the power plant to the rear axle. This is usually accomplished by means of a propeller shaft and one or two universal joints (see Fig. 15). A universal joint is merely a double-hinged shaft connection (see Fig. 16) permitting the lower end of the propeller shaft to swing at will with the rear axle and yet receive power from the engine.
In the t,car of Fig. 15 the engine and transmission are carried in the frame of the car and the first universal lies just back of the transmission. In the car of Fig. 3 the trans- mission with its change gears is placed just in „
Tii FlG- I6- — Universal joint, front of the rear axle and is fastened solidly
to the rear axle housing. This places both universal joints and the propeller shaft between the engine and the transmission.
In addition to the engine proper, the power plant contains a number of accessories necessary for the operation of the engine, such as the lubricating system, the ignition system, the carburetor, the cooling system, and the starting system. In the so-called unit power plant the clutch and change gears are contained in a single unit with the engine. All these accessories will be taken up in the later chapters.
In heavy trucks the system of power transmission is somewhat different from the pleasure car system just described. The power from the engine is carried through the clutch and back to the transmission located in the center of the chassis, as shown in Fig. 12. Here the power is turned at right angles in the rear part of the transmission and is given to a jackshaft lying across the car. The sprockets on the outer ends of this jackshaft drive the rear wheels through two chains. No universal joints are needed in the final drive, as the chains allow for the free motion of the rear axle.
13. The Torque Arm. — When the brakes are used in stopping a car, the brakes, being carried by the rear axle housing, tend to carry this Jiousing around with the wheels, likewise, the action of *he propeller
16 THE GASOLINE AUTOMOBILE
shaft and the bevel pinion in driving the rear axle (see Fig. 14) tend to turn the axle housing over backward with the same force that is exerted on the bevel ring. This twisting action or "torque" must be taken care of in some way. This can be done by torsion rods as in Fig 15, or by a single bar called a torque arm or by a torsion tube around the propeller shaft, or it can be left entirely to the springs to take care of this action. If the torque is taken up by a housing around the propeller shaft as in Fig. 17, this tube is called the "third member" of the rear axle system and is securely bolted to the rear axle housing. This system does away with one universal joint, as only one at the front extremity of the propeller shaft is used.
Strut roof-
FIG. 17. — Rear axle with torque tube and strut rods.
14. Strut Rods. — In order to preserve the alignment of the wheels or to keep one wheel from getting ahead of the other, strut rods are fastened to the brake flanges or spring seats, and extend to the front end of the third member as in Fig. 17 or to some part of the frame.
15. Brakes. — Brakes which act on the rear wheels are either of the contracting or expanding band type or the expanding shoe type.
Figure 18 shows the general layout. This is known as a double internal type of brake. A steel brake drum is fastened securely to the wheel. Both bands expand and put pressure on the inside of the drum. The outside band, or the one next the wheel, is the emergency brake and is operated by a hand lever. The other, the service brake, is under the control of the driver through the medium of the foot pedal. The brake bands are carried by brake flanges near the ends of the rear axle housing. The two sets are entirely independent of each other. Another type of
GENERAL CONSTRUCTION
17
internal expanding band brake that uses two brake drums is shown in Fig. 19. The action is similar to the above. In this case the smaller
SERVICE BRAKE
SERVICE BRAKE LEVER
EMERGENCY BRAKE LEVE
FIG. 18. — Double internal brake with single drum.
EMERGENCY BRAKE LEVER
FOOT BRAKE
EMERGENCY BRAKE
NULAfl BALL BEARINGS
RELEASE SPRINGS
FIG. 19. — Double internal brake with two drums.
band is used for the emergency. Figure 20 shows a type of brake known as the internal-external brake. There are two bands working on the
18
THE GASOLINE AUTOMOBILE
Brake facing
same drum. One set contracts around the outside of the drum and the other set expands against the inner circumference. The outer band
constitutes the service or foot brake and the inner band the emergency brake.
All bands, either contracting or ex- panding, are faced on the rubbing side with an asbestos preparation that is capable of standing a great amount of wear and is not easily burned out. Some types that use the expanding shoe have a cast-iron shoe that is pressed against the inside of the steel drum on the wheel. A typical mechanism for operating the expanding shoes or drums is clearly shown in Fig. 18, where the emergency band is shown expanded while the ser- vice brake is in the running position.
16. Wheels. — Automobile wheels are classified as artillery wheels (with wooden spokes), wire wheels, and cast- or pressed- steel wheels, the latter being limited to heavy duty trucks.
Artillery Wheels. — The artillery wheel, shown in Fig. 21, is built of second-growth hickory. The spokes are fastened together at the
Expanding
Contracting "" band
FIG. 20. — Internal-external brake.
Felloe , Demountc
C/arnp \
rim Fe//oe. bane/
Demountable rim Felloe band
FIG. 21.— Artillery wheel.
FIG. 22.— Wire wheel.
hub of the wheel by a series of interlocking mortise-and-tenon joints and the outer ends are turned down to fit in holes in the wooden felloe band.
GENERAL CONSTRUCTION 19
The hub casting, which serves to hold the inner end of the spokes, also acts as the bearing housing for the hub bearings, on which the wheel revolves.
Wire Wheels. — The wire wheel is shown in Fig. 22. On account of the scarcity of second-growth hickory, which is the only acceptable material for artillery wheels, some companies are building wire wheels which are modifications of the bicycle wheel. Wire spokes are inter- laced between the hub and rim in such a manner that the wheel is held rigid and withstands both the direct loads and side strains.
In the artillery wheel, the load is carried by the spokes on the under side. In the wire wheel, the load is carried by the spokes above the hub.
The advantages claimed by the wire wheel manufacturers are that the wheel is reduced in weight about 30 per cent. ; is more resilient, which makes an easier riding car; will stand greater radial strain; and is fully as strong as the artillery wheel.
Wearing Surfa ^^^^ /Breaker Strips
Inner Tube
Piano W:
FIG. 23. — Section of pneumatic tire.
17. Tires. — The tires used on pleasure cars are usually of the pneu- matic rubber type. Some are being filled with a spongy substance that makes them more of a cushion form and some have bridges of para rubber instead of an air cushion. The lighter commercial cars use solid rubber tires, the heavier trucks use steel tires, while some are using wooden blocks. The wooden blocks and steel tires can be used only on the very low-speed trucks on account of there being no resilience in tires of these types.
The pneumatic tire serves as a good shock absorber and eliminates a large portion of the road vibrations and jars before they reach the mechanism of the car.
The general construction of the tire is shown in Fig. 23. Several layers of heavy canvas (friction fabric) are wound around two circular wire cables (beads) in the shape of a tire. This forms the foundation,
20
THE GASOLINE AUTOMOBILE
which is filled with rubber gum to form the carcass of the tire. Around the carcass the cushion is built, which is an extra thickness of com- pounded rubber held in place by a double layer of canvas. This is called the breaker strip. Outside of this comes the tread. The tread is the part that comes into contact with the road and takes the wear. This whole structure is then vulcanized to make a solid unit.
The inner tube, which is merely a rubber bag with a check valve to hold the air, is inserted in the casing and the casing is fitted on the
FIG. 24. FIG. 25.
FIGS. 24 AND 25. — Types of detachable rims.
rim in such a way that when the pressure is applied the bead grips the rim, and the flanges on the rim prevent the tire from sliding off sideways. 18. Rims. — Rims may be classified as clincher, detachable, and demountable, or a combination of two of these. The cuts shown in Figs. 24, 25, and 26 show sections of the Goodyear rims. Figure 24 illustrates the detachable rim of two parts. The side ring can be easily removed from the groove by a screw-driver. The higher the inflation pressure in the tire the harder the side ring hugs the groove. This rim is used to a great extent on electric pleasure cars.
FIG. 26.— Demountable-detachable rim.
Figure 25 shows a heavier type of detachable rim, quite general on gasoline pleasure cars.
Figure 26 shows a rim which has both the demountable and detach- able features combined. With demountable rims, an extra rim with tire fully inflated may be carried. In case of a blow-out, the damaged tire and its rim may be quickly removed and the spare rim and tire put on. This saves considerable time in cases of tire trouble.
Figures 27 and 28 show the rim made by the General Rim Co. This
GENERAL CONSTRUCTION
21
is a demountable rim and is locked on the rim at a single point. To remove the rim from the wheel the toggle nut is turned to its lowest position on the end of the clamping bolt, as shown in Fig. 28. This draws the clamping ring into the groove and the rim is re- leased and ready for removal. To replace the rim merely reverse this operation.
Felloe band
Felloe Demountable rim
Toggle nut FIG. 27.
Felloe \ \ ^^^^ \ Felloe bane/ \ / UlP C/amp Demountable rim Clomping boft FIG. 28.
FIGS. 27 AND 28. — Demountable clincher rim.
Figure 29 shows sections of the clincher rim as used on the Ford car, and also shows the method of removing the tire from the rim.
19. The Speedometer Drive. — Some device for indicating the speed should be installed on every car as the cost of one fine will purchase a reliable speedometer.
Second Position of Tire Tool
FIG. 29. — Method of removing clincher tires.
The drive may be taken from a gear attached to the transmission, as shown in Fig. 30, or from a similar attachment on one of the front wheels.
Figure 31 shows a speedometer drive installed in the spindle of the steering knuckle and driven from a plate under the hub cap. This eliminates the use of an exposed gear and requires no attention except proper lubrication. Care should be used to see that the drive plate is properly replaced if the hub cap is removed for any reason.
22
THE GASOLINE AUTOMOBILE
FIG. 30. — Speedometer drive from transmission.
SPEEDOMETER GEAR
SPEEDOMETER GEAR BUSHING SPEEDOMETER DRIVE SH/
SPEEDOMETER DRIVE PLATE
H
SPEEDOMETER PJNIOM
OOMETER PINION BUSHING
SPEEC
SPEEDOMETER END CONNECTION
FIG. 31. — Speedometer drive through knuckle spindle.
GENERAL CONSTRUCTION
23
20. Control Systems. — Figures 32 and 33 show the two prevailing control systems. Figure 32 shows the left-hand drive and center con- trol system generally used on cars with sliding gear transmissions.
SPARK CONTROL LEVE
IGNITION SWITC
SPEEDOMETER
CLUTCH PEDAL
ACCELERATOR PEDAl
/ REGULATOR
SERVICE BRAKE PEDAL
EMERGENCY BRAKE LEVER ^CONTROL LEVER
FIG. 32. — Left-hand drive, center control.
FIG. 33.— The Ford control.
The operation is as follows: The left-hand pedal operates the clutch and the other pedal the foot or service brake. The right-hand Jever operates the emergency brake. The left-hand lever operates the change gears as follows: To the left and ahead for reverse, to the left and back
24 THE GASOLINE AUTOMOBILE
for low speed ahead, to the right and ahead for second speed ahead, and to the right and back for third or high speed ahead. This order of events is not standard for all cars. Every car has its own system of shifting gears.
Figure 33 shows the Ford control system. This system consists of three foot pedals and one hand lever. The pedal on the left operates the clutch and controls the high and low speed. The hand lever also operates the clutch and when drawn all the way back sets the emergency brake. With the hand lever forward and left pedal up it is then in high gear. To get low speed ahead, the left pedal is pressed all the way forward; halfway in releases the clutch? The second or middle pedal marked "R" operates the reverse mechanism. To reverse the car the hand lever must be in a vertical position or the clutch pedal half- way in; then pressing on the reverse pedal drives the car backward. The right-hand pedal operates the foot or service brake, which is on the transmission.
The chapters to follow will treat in detail of the various parts of the car, their construction, methods of operation, and maintenance.
CHAPTER II ENGINES
21. What is an Explosion? — Practically all gasoline engines are driven by explosions which take place within the cylinder of the engine and drive the piston, thus causing rotation of the revolving parts of the engine. These explosions are in a way very similar to the explosions of gunpowder or dynamite. When a charge of gunpowder is fired in a cannon or gun, the gunpowder burns and produces gases which exert a tremendous pressure on the shell and force it from the gun.
Practically any substance that will burn can be exploded if under the proper conditions. An explosion is merely a burning of some material taking place almost instantaneously, so that a great amount of heat is generated all at once. When any substance burns, it unites rapidly with oxygen from the air. If we want to get an explosion, it is necessary to have the fuel very finely divided and carefully mixed with air, so that the burning can be very rapid. Then, if we start the fuel burning, by an electric spark or any other means, the flame instantly spreads throughout the mixture and an explosion occurs. In a gasoline engine we take in gasoline vapor mixed carefully with air. This mixture is then exploded inside the cylinder of the engine. The force of this explosion drives the piston and the motion is transmitted through the connecting rod to the crank. To make the process continuous and keep the engine going, it is necessary to get rid automatically of the gases from the previous ex- plosion and to get a fresh charge into the cylinder ready for the next explosion. This process must be carried out regularly by the engine, in order to keep it running.
22. Cycles. — As we have just seen, an engine must supply itself with an explosive mixture so that the force of the explosion will cause the engine to move, and it must get rid of these dead gases and get in a fresh charge of gas and air and explode this so as to keep up the motion. There are in use at the present time two principal systems of performing this series of operations. These systems, or rather the series of opera- tions, are called cycles, and the engines are named according to the number of strokes it takes to complete a cycle. These two cycles, or systems of engines, are the four-stroke cycle and the two-stroke cycle.
Remember that a cycle refers to the series of operations the engine goes through. In the four-stroke cycle there are four strokes or two revolutions. In the two-stroke cycle there are two strokes or one revolu- 5 25
26 THE GASOLINE AUTOMOBILE
tion. Many people leave out the word stroke and talk of "four-cycle engines" and "two-cycle engines." This causes the misunderstanding that many people have as to just what a cycle really is. A better way is to call them "four-stroke. engines" and "two-stroke engines."
23. The Four-stroke Cycle.— Figures 34, 35, 36 and 37 show an engine which operates according to the four-stroke cycle. The engine shown here is a vertical engine, that is, the cylinder is placed above the crank shaft (instead of being at one side) and the piston moves up and down in the cylinder. This is the prevailing form for automobile engines.
SPARK PLUG 'INLET VALVE
SUCTION STROKE
FIG. 34.
COMPRESSION STROKE
FIG. 35.
Any engine consists of four principal parts: the cylinder, which is stationary and in which the explosion occurs; the piston, which slides within the cylinder and receives the force of the explosion; the connecting rod, which takes the force from the piston and transmits it to the crank; and lastly the crank, which revolves and receives the force of the explosion as the piston goes in one direction, and which then shoves the piston back to its starting point. A four-stroke engine has a number of other minor parts, whose uses will be brought out presently. This engine uses four strokes of the piston to complete the series of operations from one explosion to the next, and is therefore said to operate on the four-stroke cycle, or it is said to be a "four-stroke" engine. The first illustration, Fig. 34, shows the engine just drawing in a mixture of gas and air. This is continued until the piston gets clear down to the bottom of the stroke,
ENGINES
27
and the cylinder is full of this explosive mixture. This operation is called the suction stroke. Then the valves are shut, as in Fig. 35, and the piston is forced back to its top position. This squeezes or compresses the gas into a space left in the top of the cylinder, and this process of compressing it is called the compression stroke. After the piston gets to the top, the gases are ignited or set fire to and burn so quickly that an explosion results and the piston is driven down again, as in Fig. 36. This is called the expansion or working stroke. When it reaches the bottom of the stroke, another valve is opened, and while the piston is returning to the
WORKING STROKE
FIG. 36.
EXHAUST STROKE
FIG. 37.
top position it forces out through this valve the burned gases which occupy the cylinder space. This is the exhaust stroke. The engine is now ready to repeat this series of operations. These operations have taken two 'revolutions or four strokes. A stroke means a motion of the piston from either end of the cylinder to the other end. Consequently, there are four strokes in the cycle of operations of this engine, and we therefore call it a four-stroke engine.
24. The Order of Events in Four-stroke Engines. — The various parts or events in the four-stroke cycle are shown on the diagram of Fig. 38. This shows the two revolutions of the four -stroke cycle divided up so as to show the crank positions when the different events occur. The diagram is drawn for a vertical engine with the crank revolving to the left, as shown on the engine of Figs. 34 to 37. This is the direction of rotation
28 THE GASOLINE AUTOMOBILE
of an automobile engine to a person in the car looking forward toward the
^Starting at the top of the diagram, we have just exploded the charge and as the crank swings over to the left the gases are expanded. Before the crank reaches the bottom, the exhaust valve is opened. This is kept open while the piston is returned to the top. The inlet valve is then opened and the suction stroke occurs as the crank and piston again descend. Just after the crank passes the bottom, the inlet valve closes. Both valves being now closed, the charge is compressed as the crank and piston rise again to the top. A short time before reaching the top, ignition occurs. This should be just far enough before the top so that the explosion or combustion is taking place as the crank passes the top and starts to descend on the expansion stroke.
FIG. 38. — Order of events in the four-stroke cycle.
25. The Mechanism of Four-stroke Engines. — In addition to the four principal parts previously mentioned, there are a number of other small parts which we will now discuss. First, we must have two valves located in the upper end of the cylinder, one for the purpose of letting in the fresh mixture of gas and air, and the other for the purpose of letting out the burned gases. Each of these valves opens once in a cycle, that is, once in two revolutions. In this engine (Figs. 34 to 37) the valves are shown in the T-head arrangement, the inlet valve being on the left and the exhaust valve on the right. These valves are of a form called poppet valves. They are mushroom shaped, with beveled edges which fit into a beveled seat. The valves are held shut by springs on the outside, which pull on the valve stems and hold them tightly against the seat, so that
ENGINES 29
gases can not leak in or out, except when one of the valves is opened. To operate the valves, there are two push rods, one for each valve. These push rods receive their motion from the cams. On the lower ends of these rods are rollers, and these roll on cams on the cam shaft inside of the crank case. These cams have each a hump or projection on about one-fourth of their circumference. When one of these strikes the roller it raises it up, and this motion is transmitted through the push rod to the valve. After the projection of the cam has passed under the roller, the valve spring will close the valve and force the push rod back to the original position.
Since the valves on an engine each work but once in two revolu- tions, the engine must be arranged so that the cams come around only once in two revolutions. To do this, the general arrangement is to put a small gear on the crank shaft and have this drive another gear, twice as large, on the cam shaft. In this way the cam shaft will run at just half the speed of the crank shaft. These gears are called half- time gears.
26. Valve Timing and Setting. — The exhaust valve of an engine opens on an average of about 45° before the end of the stroke, in order that the pressure may be reduced to atmospheric by the end of the stroke so there will be no back pressure during the exhaust stroke. At the end of the exhaust stroke, the exhaust valve should remain open while the crank is passing the center so that any pressure remaining in the cylinder may have time to be reduced to atmospheric.
The inlet valve very seldom opens before the exhaust closes. Most manufacturers do not open the inlet until the exhaust closes, for fear of back-firing, although there is little danger of this except with slow- burning mixtures. The inlet valve opens, on an average, 10° late (after center). At the end of the suction stroke there is still a slight vacuum in the cylinder and the inlet is kept open for a few degrees past center to allow this to fill up and get the greatest possible quantity of gas into the cylinder. On an average, the inlet valve closes about 35° late, de- pending on the piston speed of the engine.
In studying the valve setting of an engine, the first step, of course, is to observe the timing of the engine as it stands. To do this we must turn the engine by hand. By inserting a thin sheet of tissue paper between a valve stem and its push rod, we can tell when the valve opens and closes by noticing when the paper is gripped in opening the valve and when it is released in closing. The corresponding crank positions should be noted. We can then see whether it is possible to do anything to improve the valve setting. Valve cams are made for a certain valve setting and will give a certain angle of opening. This may become altered in several ways. Any excessive lost motion in the valve motion
30 THE GASOLINE AUTOMOBILE
will result in a valve's opening too late and closing too early. Wear on the cam will have the same effect. If a cam shaft has been removed and replaced, the timing gears may be put together wrong. This would ad- vance or retard the whole series of events and can readily be found out when the timing is observed.
The clearance or lost motion in the valve mechanism between the cam and the valve stem should be about 3^4 in. or less. In order to keep the valves quiet on their engines, some makers use a clearance of the thickness of ordinary writing paper, or about %0oo in- If the clear- ance or lost motion is too great, it will cause the valve to open late and close early, and will also cause the cam to strike the roller a hard blow with the middle of its face, instead of catching it gradually at the beginning of the incline. It will also reduce the valve opening and possibly choke the engine.
In a four-stroke engine the cam shaft revolves once for each two revolutions of the crank shaft. Consequently, a valve opening of 180° will be represented by but 90° on the cam, and, for any given crank angle through which the valve is to be open, the corresponding cam angle will be but one-half the given crank angle. If an exhaust valve is to open 45° before the beginning of the exhaust stroke and close 10° after the end of the stroke, the total crank angle will be
180° + 45° + 10° = 235°
235° The corresponding cam angle = ~ = 117^°. By "cam angle"
we mean the angle on the cam, from the point where it starts to open the valve to the point where the valve is seated again. An inlet valve that is to open 10° late and close 30° late, would have a total crank angle of
180° - 10° + 30° = 200°
200° The corresponding cam angle = — ^— = 100°.
27. Valves. — The prevailing type of valve is what is called the poppet or mushroom type — poppet, from its operation, and mushroom, from its shape. The exhaust valve must be opened by a cam because it must be opened against a pressure of 40 to 60 Ib. in the cylinder and held open while gases are forced out through it. The inlet valve may be opened by a cam or we may use a light spring and depend on the suction to open it. The suction type is, of course, cheaper to build, but it re- duces the capacity of the engine so that for the same power there is no saving. Consequently we find automatic inlets as a rule only on the small farm engines that are built to sell at a low price. To open an automatic valve, there must be a difference in 'pressure on the two sides
ENGINES
31
of the valve equal to the tension of the valve spring. This tension may be reduced or increased by the weight of the valve, if vertical, and opening respectively downward or upward. For' high-speed engines an auto- matic valve is particularly unsuited, since a heavy spring must be used to insure quick closing at high speed.
Poppet valves usually have 45° beveled seats as shown in Fig. 39, though occasionally flat valves are seen which rest on flat seats. The valves must be large enough to let the gases in and out of the cylinders freely. If they are too small they will cut down the power of the engine by not permitting it to get a full charge. The valves usually measure from one-third to one-half of the cylinder diameter. Valve diameters are usually measured by the opening in the valve seat (see dimension marked d in Fig. 39). The diameters of the inlet and exhaust pipes should at least equal this valve diameter and should be larger if possible.
Fia. 39.
FIG. 40.
FIG. 41.
The valve lift should, when possible, be sufficient to give the gases as large a passage between the valve and seat as they have through the opening d, Fig. 39. For a flat valve seat this would require a lift of one- fourth of the valve diameter. With a beveled seat, the gases pass through an opening in the shape of a conical ring having a width of passage equal to hf, Fig. 39. To have the necessary passage area, the lift h of the valve should be about three-tenths of the diameter. In most stationary engines this lift can be given the valve, but in high-speed engines it would be too noisy. This lift would then cause pounding and wear on the cams; it would require very stiff springs to make the valves follow the cams in closing and would be very hard on the valve seats and stems. For automobile engines the valves are made as large as possible and the lift is limited to from % Q to ^ in.
The best materials for valve heads are cast-iron, nickel-steel, and tungsten-steel. Cast-iron is very cheap, easily worked, and stands corrosion well. It is weak, however, and therefore requires a heavier weight than other materials and this is especially objectionable for high- speed engines. The nickel-steel is strong, non-corrosive, and has a very low coefficient of heat expansion. Hence it does not warp so readily
32
THE GASOLINE AUTOMOBILE
as other metals It is rather expensive and when used is generally electrically welded to a carbon-steel valve stem. The tungsten-steel is very hard and will stand high temperatures without pitting. Cast-iron valve heads can be screwed on a steel stem as in Fig. 40, the stem being riveted to prevent loosening. Figure 41 shows a common European form
FIG. 42.— T-head.
FIG. 43.— L-head.
FIG. 44.— I-head.
FIG. 45.— L-and-I head.
for valves which is being rapidly adopted here. The curvature under- neath gives the gases a smooth passage without any of the whirling eddies that occur under the ordinary flat valve.
Any valve needs regrinding into its seat occasionally with oil and emery or ground glass. Exhaust valves require this more often than inlet valves, as they become warped and pitted by the hot gases. After
ENGINES
33
a valve is ground in, the push rods should be readjusted, as the grinding will lower the valve and reduce the clearance in the valve motion.
28. Valve Arrangements. — The possible arrangements of the valves in the cylinder are numerous. Figure 42 shows the T-head arrangement used in many of the large automobiles. This arrangement permits of a large valve and a low lift, and therefore makes a very quiet engine. Fig- ure 43 shows the L-type with both valves on one side. This is the most common type. It requires only one cam shaft and has a very simple,
INNER SLEE
FIG. 46. — Section of Silent Knight engine.
direct-acting valve mechanism. It does not have as much cooling surface to the combustion chamber and is, therefore, more economical in the use of fuel than the T-head. Figure 44 shows the valve-in-the-head arrange- ment. This is sometimes called the I-head arrangement. It is especially popular for racing cars because it gives a short, quick passage into the combustion chamber and gives a simple, compact combustion chamber with a minimum loss of heat to the cooling water. Figure 45 shows an arrangement used on the Reo car that is a combination of the L-type and the valve-in-the-head type, the intake valve being in the top and
34 THE GASOLINE AUTOMOBILE
operated by a rocker arm while the exhaust is on the side and is operated by a direct push rod. Both valves are operated from one cam shaft.
29. The Knight Engine.— The Knight engine is built on the principle of the four-stroke cycle, but the usual poppet valves have been replaced by two concentric sleeves sliding up and down between the piston and cylinder walls. Certain slots in these sleeves register with one another at proper intervals, producing direct openings into the combustion chamber from the exhaust and inlet ports. The construction of the Steams-Knight motor is illustrated in Fig. 46 which shows the general arrangement of the parts and their nomenclature.
FIG. 47. — Action of sleeves in Knight engine.
It will be noted that two sleeves are independently operated by small connecting rods working from an eccentric or small crank shaft running lengthwise of the motor. This eccentric shaft is positively driven by a silent chain at one-half the speed of the crank shaft. The eccentric pin operating the inner sleeve is given a certain lead or advance over that operating the outer sleeve. This lead, together with the rota- tion of the eccentric shaft at half the crank-shaft speed, produces the valve action illustrated in Fig. 47, which shows the relative positions of the piston, sleeves, and cylinder ports at various points in the rotation of the crank shaft.
30. The Rotary Valve.— The rotary valve as used in the Speedwell car consists of two cylindrical shafts in the head of the motor, one for ex-
ENGINES
35
haust and one for the inlet. These shafts are slotted and when rotating register with ports in the cylinder walls, thus opening passageways for intake and exhaust gases. The rotary movement of the valves is con- tinuous in one direction, the valves being driven by a silent chain from the crank shaft. Figure 48 illustrates the different positions of the rotary valves at the beginning of each of the four strokes. The arrows inside show the direction of rotation of the valves and the arrows out- side indicate the direction of the fresh gas going in and the exhaust gas passing out of the cylinder.
31. Two-stroke Engines. — Two-stroke engines as a class are not so flexible as the four-stroke engines under the varying speeds and loads encountered in automobile service. Consequently they have not been used to any great extent in motor cars, although a few satisfactory cars have been built with them.
INDUCTION
COMPRESSION EXPLOSION
FIG. 48. — Speedwell rotary valve engine.
EXHAUST
Since the piston of a four-stroke engine receives an impulse or ex- plosion only once in two revolutions, considerable effort has been ex- pended in trying to develop an automobile engine that would give an explosion in each cylinder every revolution and yet would operate as satisfactorily and economically as the four-stroke engine. An impulse every revolution would make a more powerful engine than one of the same size which received an impulse only once in two revolutions and it would also make the flow of power more continuous for the same number of cylinders.
The Two-port Engine. — Most of the two-stroke engines in use are very much like those shown in Figs. 49 to 52. In appearance, these engines are much simpler than the four-stroke engine, but are not necessarily any simpler in operation. They do not have any valves opening into the combustion chamber, such as are found in the four-stroke engine. The exhaust gases leave the cylinder through a port in the cylinder wall, which is uncovered by the piston at the end of the expansion stroke, as shown in Fig. 50. At the same time, a fresh charge is blown into the cylinder through
36 THE GASOLINE AUTOMOBILE
a similar port on the other side. The top of the piston has a deflector which turns the incoming charge up into the clearance space. The charge then strikes the cylinder head, which turns it down on the other side toward the exhaust port, thus driving the dead gases out ahead of it. The piston then comes back, shuts off both these openings and compresses the fresh charge into the clearance space as shown in Fig. 49. It is then ignited in the usual manner by a spark plug screwed into the cylinder head. This gives the piston an impulse every revolution.
The engines of Figs. 49 to 52 have each crank enclosed all around and they use this case or chamber as a sort of a pump to supply fresh gas to the cylinder. When the piston goes up, the space inside the crank case is increased, and when it comes down the space is reduced, thus main- taining a breathing action inside the crank case. In Fig. 49 the piston
Spark Plug
Exhaust Port Transfer Port / Check Valve (Open) jig Carburetor
/Deflector Transfer
Check Valve (Closed)
FIG. 49. FIG. 50
FIGS. 49 AND 50. — Two-port, two-stroke engine.
is shown traveling toward the top. This motion causes a suction in the crank case and causes air to enter through the carburetor. As the air passes through the carburetor it becomes saturated with gasoline and then passes through the check valve into the crank case. When the piston gets to the top, the suction ceases and the check valve is closed by its spring. Meanwhile, an explosive mixture has been compressed above the piston and at the top of the stroke is ignited by a spark. This produces an explosion or rise in pressure above the piston, just as in the four-stroke cycle and this drives the piston down on its working stroke. As the piston comes down, it compresses the fresh gases in the crank case into a smaller volume and thus raises their pressure. Meanwhile, as the piston nears the bottom of its stroke, it uncovers the exhaust port and the pressure in the cylinder causes a large part of the burned gases
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37
to shoot out through this port. An instant later the piston uncovers a transfer port on the other side and is now in the position shown in Fig. 50. This transfer port is connected into the crank case and therefore allows the gases from the crank case to blow over into the cylinder as shown in Fig. 50.
The piston head is so shaped as to form a deflector, which turns the fresh charge toward the cylinder head so that it can not blow out the exhaust port. The piston then returns, cuts off these ports, and compresses this charge, meanwhile drawing another charge into the crank case. This engine is called a two-port type, because there are only two ports in the cylinder walls to be operated by the piston.
The Three-port Engine. — The only difference between this type and the preceding one is in the method of admitting the gases into the crank
Spark Plug
Met Port
Deflector •Transfer Port
Exhaust
Carburetor \-,
FIG. 51. FIG. 52.
FIGS. 51 AND 52. — Three-port, two-stroke engine.
case. Instead of using a check-valve, the admission of the gases' to the crank case is controlled by the piston, which uncovers a third port in the cylinder walls as it nears the top of the compression stroke. As will be seen in Fig. 51, the carburetor is on the other side of the engine, placed just below the exhaust pipe. As the piston rises, it creates a suction in the crank case, but there is no way for any gas to get in until the piston reaches the top of its stroke. As the piston uncovers this third port, the air enters with a rush through the carburetor, picks up the gasoline on its way through, and enters the crank case. The piston then descends, cuts off the third port, compresses the gases in the crank case, as in Fig. 52, and then blows them over into the cylinder as before.
Against the two-stroke engine we have the facts found from ex- perience that they 'are not as economical in the use of fuel and are more
38 THE GASOLINE AUTOMOBILE
uncertain in their action than the four-stroke engine. Since the fresh charge is depended on to blow out the exhaust gases, it is evident that some of the incoming charge is liable to pass out through the exhaust port. Gases mix very quickly and it is not possible to keep the dead and fresh gases separate, and yet drive the dead gases out and fill the cylinder com- pletely with fresh gases. If a full charge enters through the transfer port, some of it will be lost through the exhaust port without its being utilized. By skillfully proportioning the two ports and the shape of the deflector to the size and speed of the engine, it is possible to largely pre- vent the waste of fuel through the exhaust port.
A two-stroke engine does not get as full a charge of gas as does a four- stroke engine and, consequently, will not be twice as powerful. The horse power of a two-stroke engine is usually about 1% to 1^ times that of a four-stroke engine of the same size and speed.
The small two-stroke engines shown in Figs. 49 to 52 sometimes cause trouble from back-firing or exploding in the crank case. This is caused by the mixture in the crank case becoming ignited and exploding before it goes over into the cylinder. This wastes the energy of the gas and fills the crank case with dead gases, so that the engine will frequently come to a stop. Back-firing is caused by the mixture in the cylinder being still in flames when the piston uncovers the transfer port. The flame shoots through this port into the crank case and fires the mixture there. It has been found by experience that mixtures weak in gas are the ones which burn slowly and therefore cause back-firing. Consequently, the cure for crank-case explosions is to give the engine more fuel.
Any leaks into the crank case are very serious in either of these types. With the slow speed used -in starting an engine by hand, a very small leak may admit air enough to satisfy the suction in the crank case and thus prevent any gas from being drawn in or, at any rate, it may so weaken the mixture as to make it non-explosive.
This brief statement of some of the difficulties of the two-stroke engine will show some of the things that must be overcome in order to make this type of motor generally applicable to automobile service.
32. The Flywheel. — The purpose of the flywheel is to keep the engine running from one explosion to the next, and to make the engine run smoothly. If an engine did not have a flywheel, it would run in a very jerky manner, if it ran at all, and it is more probable that the explosion would simply drive the piston to the other end of the stroke and that it would stop there. Any one knows that the heavier a moving object is and the faster it is going, the harder it is to stop it. The flywheel on an engine is quite heavy and the result is that, once started, it will keep the engine going for some time. A gas-engine flywheel must not only be heavy enough to keep it going from one explosion to the next, but must
ENGINES 39
keep it going without allowing the speed of the engine to drop down too much between explosions.
33. Ignition. — In order to cause the explosions within the cylinder, some means must be provided for lighting the charge of gas. This is usually done by causing an electric spark to pass between two points within the cylinder. The spark sets fire to the mixture and the explosion follows.
There are two general methods of electric ignition. One of these is called the make-and-break system because it requires some moving parts inside the cylinder to make an electric circuit, and then break it quickly so that a spark will occur inside the cylinder. The other system is called the jump-spark system. This is the system used in automo- biles. There are no moving parts which have to pass through the cylinder wall in this system. The spark coil or magneto makes a current powerful enough to jump between two fixed points inside the cylinder. The complete details of these systems of ignition will be taken up in a later chapter.
34. Clearance and Compression. — It was discovered by some of the early inventors of gas engines that compressing a gaseous mixture causes it to give a much more powerful explosion. Consequently, all gas engines draw in a full cylinder charge of gas and air, and then compress this back into a space left at the upper or rear end of the cylinder. This space, which is left for the gas to occupy when the piston is at the top end of its stroke, is called the clearance space or combustion chamber. The amount of this clearance space in relation to the whole cylinder volume determines just how much the gas is compressed. It has been found from experience that different kinds of gases require different amounts of compression and, therefore, the clearance space is made different for different fuels. The clearance is generally spoken of as being a certain per cent, of the piston displacement, varying from 24 to 30 per cent, for automobile engines.
35. Piston Displacement. — This refers to the space swept through by the piston in going from one end of the stroke to the other. It is given this name because, as the piston moves through its stroke, it will either draw in or force out that volume of air or gas. The piston displacement is calculated by multiplying the length of stroke by the area of a circle whose diameter is the inside diameter of the cylinder. For example, a 3j^-in by 5-in. engine (this means 33^ in. inside cylinder diameter and 5 in. stroke) would have a piston displacement as follows:
The area of a 3^-in. circle is 0.7854 X 3>^ X 3>£ = 9.621 sq. in.
The piston displacement is 5 times this, or 48.105 cu. in.
The clearance of such an engine would be from 24 to 30 per cent, of this. If we suppose that it is 25 per cent., then the actual space which must be left for the clearance will be 48.105 X 0.25 = 12.026 cu. in.
40 THE GASOLINE AUTOMOBILE
36. Cylinder Cooling.— When an explosion occurs inside the cylinder of an engine, the gases on the inside reach a temperature somewhere around 3000°. The walls of the cylinder are, of course, exposed to this high heat and would very quickly get red hot if we did not have some way of keeping them cool. The polished surface upon which the piston slides would be very quickly spoiled. The most common way of keeping the cylinder cool is by the use of water, and the arrangement for this is shown in the engines illustrated in this chapter. Surrounding the cylinder is a jacket with a space between for the cooling water. By keeping a supply of water passing through this space, the cylinder can be kept cool enough for the operation of the engine. The cylinder head is also cast with a double wall, especially around the valves, so that these parts will also be kept cool. The cooling fluid used is generally water, although sometimes special anti-freezing solutions are used where there is danger of the engine freezing. Water should not be allowed to remain in the jacket of an engine over night if there is danger of a frost, as the freezing of the water will crack the cylinder. When the supply of water is limited, as in an automobile, the water is cooled in a radiator or system of pipes, and used over again. The water is kept in circulation by a pump or by the thermo-syphon system and the hot water is cooled by the air passing over the radiator.
37. The Muffler. — When the exhaust valve of an engine opens at the end of the expansion stroke the pressure of the gas inside the cylinder is
FIG. 53.— Typical muffler.
still about 50 or 60 Ib. per square inch. The valve must open and let this pressure out before the piston starts back, or else the back pressure will tend to stop the engine. The valve is opened quickly, and the high pressure, being suddenly released into the exhaust pipe, causes the sharp sound which we hear when an engine exhausts. This sound is not the sound of the explosion, as is commonly supposed. The real ex- plosion takes place a little before this sound and can be heard only as a dull thump inside the cylinder. The explosion occurs at the beginning of the working stroke, while the sound that we hear in the exhaust comes at the end of the stroke.
In order to prevent this sudden exhaust from causing too great a
ENGINES 41
noise it is customary to have a muffler. A muffler is generally a chamber in the exhaust pipe which receives the exhaust gases from the engine and expands them gradually into the outside air, thus preventing a loud noise. A common arrangement of an automobile muffler is shown in Fig. 53.
38. Horse Power of Engines. — The horse power of an engine is the measure of the rate at which it can do work. One horse power is a rate of 33,000 ft.-lb. a minute. There are two ways of measuring engine power. We can determine the power developed by the ex- plosions in the cylinder, in which case we have what is called the indi- cated horse power (i.hp.} ; or we can attach a brake to the flywheel and measure the power which the engine actually delivers. This is called the brake horse power (b.hp.). Engines are usually rated by their brake horse power because that is what they are actually capable of delivering. The brake horse power of an automobile engine will usually be from 70 to 85 per cent, of its indicated horse power, the loss being that consumed in the engine mechanism.
There are a number of quick rules for estimating the power of engines according to their cylinder dimensions and the speed. Those most used for four-stroke engines are given below. The simplest of these and the one most used is known as the S. A. E. formula or Society of Auto- mobile Engineers formula.
Authority Formula
S. A. E. 1 D2N
= hp.
Royal Auto Club 2.5
Brit. Inst. of Auto Engrs. 0.45 (D + L) (D - 1.18) = hp.
D27 7? AT E. W. Roberts -- = hp.
D = diameter of cylinder in inches. R = revolutions per minute of
crank shaft. L = length of stroke in inches. N = number of cylinders.
Derivation of the S. A. E. Horse Power Formula. — The indicated horse power of a single-cylinder, four-stroke engine is equal to the mean ef- fective pressure, P, acting throughout the working stroke, times the area of the piston, A, in square inches, times one-quarter times the piston speed, S, divided by 33,000, thus:
PAS ~ 33,000 X 4
Multiplying this by the number of cylinders, N, gives the indicated horse power for an engine of the given number of cylinders, and further multiplying by the mechanical efficiency of the engine, E, gives the brake horse power.
6
42 THE GASOLINE AUTOMOBILE
Therefore, the complete equation for brake horse power reads:
PASNE b.hp. - 33^000 x 4
The S. A. E. formula assumes that all motor car engines would de- liver or should deliver their rated power at a piston speed of 1000 ft. per minute, that the mean effective pressure in such engine cylinders would average 90 Ib. per square inch, and that the mechanical efficiency would average 75 per cent.
Substituting these values in the above brake horse power equation, and substituting for A its equivalent, 0.7854Z)2, the equation reads:
90 X 0.7854P2 X 1000 X N X 0.75 33,000 X 4
and combining the numerical values it reduces to:
To make it simpler, the denominator has been changed to 2.5 without materially changing the results.
The formula can be simplified, however, for ordinary use by consider- ing the number of cylinders; thus for the usual four-, six-, and eight- cylinder engines it becomes:
1.6 D2 = hp. for all four-cylinder motors.
2.4 D2 = hp. for all six-cylinder motors.
3.2 D2 = hp. for all eight-cylinder motors.
4.8 D2 = hp. for all twelve-cylinder motors.
The S. A. E. formula comes very close to the actual horse power delivered by most automobile engines at the piston speed of 1000 ft. per minute. However, at the present time, most of the engines will deliver the maximum power at speeds higher than this, usually around 1500 ft. per minute. As a result, the power which the engines are capable of delivering is greater than that given by the S. A. E. formula. The formula will serve, however, as a means of comparing engines on a uniform basis.
CHAPTER III
POWER-PLANT GROUPS AND TRANSMISSION SYSTEMS
39. Single- and Multi-cylinder Engines. — The first automobile power plant consisted of a one-cylinder engine which gave power impulses at regular intervals of time for the propulsion of the car. Naturally it operated very jerkily and with considerable noise, due to the size of the cylinder and the time between impulses. These facts led to the adoption
-Two Revolutions-
Compreaalon
1 Cylinder
2 Cylinders
4 Cylinders
6 Cylinders
8 Cylinders
FIG. 54. — Power diagrams.
of the two-, four-, and six-cylinder engines, and quite recently the eight- and twelve-cylinder engines have come into use as automobile power plants. In Fig. 54 can be seen one of the distinct advantages of the multi- cylinder engine for motor car purposes. The length of the diagram represents two revolutions of the engine crank shaft. The curved line 7 43
44 THE GASOLINE AUTOMOBILE
acefg represents the variations in the power from a single cylinder. The line bh represents uniform power requirement of the car. When the power curve goes above bh the engine accelerates and the surplus power is thus stored in the flywheel; when the curve goes below bh the flywheel gives up power and the engine slows down.
As the number of cylinders increases, the impulses increase in fre- quency, the average power is greater, and above four cylinders there is no period during which some cylinder is not delivering power. This means that in a six- or eight-cylinder car, there is no time at which the flywheel must supply all the power required by the car.
The multi-cylinder engine, therefore, furnishes a practically continu- ous flow of power to the car with little vibration. The increase in the number of cylinders has a tendency to reduce the size of each cylinder and this fact combined with the steady operation of the engine, makes the modern automobile engine a very smooth-running, quiet, power-plant unit.
40. Power Plant and Transmission Arrangements. — Figure 55 shows the arrangement of the Studebaker power plant and transmission system. The engine is placed in the front of the frame, being supported at four points. The clutch, which is of the cone type, is built inside the flywheel, and permits the engine to be disengaged from the transmission system. The propeller shaft, which transmits the power from the engine to rear wheels, is connected to the clutch by means of a universal joint which permits the shaft to receive power and to deliver it to the rear axle.
The change-gear set or transmission is placed on the rear axle just in front of the differential housing which carries the differential gear. The change-gear set permits the relative speed of the engine and car to be changed according to conditions. The chassis diagram indicates the location of the other important parts. Notice the three-quarter elliptic rear springs.
The chassis of the Mitchell "Eight" is shown in Fig. 56. The engine in this case is supported at only three points, one at the front and two at the rear. The clutch is of the cone type operating in connection with the flywheel. It will also be noticed that the change-gear set is placed at the front of the propeller shaft, which then goes directly to the final drive on the rear axle. There is a single universal joint, which is between the clutch and gear set.
The Hollier " Eight" chassis is shown in Fig. 57. Here we see the application of the well-known "unit power plant" in which engine, clutch, and change gears are built into one single unit. This arrangement permits the use of only one universal joint between power plant and rear axle. Notice the cantilever type of rear springs.
In the chassis of the Ford Model T, Fig. 58, use is also made of the
POWER-PLANT GROUPS
45
~~Un/ verso/ ,' Joints
FIG. 55.— Chassis of Studebaker "Six,
46
THE GASOLINE AUTOMOBILE
FIG, 56,— Chassis of Mitchell "Eight
POWER-PLANT GROUPS
47
Un/f
FIG. 57.— Chassis of Hollier "Eight."
4g THE GASOLINE AUTOMOBILE
"unit power plant" with three-point support. The engine, clutch, and change gears are built together in a single unit and are supported on the frame at only three points. The connection between power plant and rear axle is made by the use of only one universal joint. As will be seen later, this car is equipped with a "planetary" transmission which is built on a principle entirely different from the usual clutches and change- gear sets. The entire rear of the car is supported by an inverted semi-
Tic. 58.— Chassis of Ford Model T.
elliptic spring extending over the rear axle. A similar but lighter spring is used in front.
The sectional view of the Lyons-Knight four-cylinder car in Fig. 59 shows very clearly the arrangement of the engine and the transmission groups. The engine is of the Knight type and delivers its power through a plate clutch and through the universal joints and propeller shaft to the
POWER-PLANT GROUPS
49
50
THE GASOLINE AUTOMOBILE
change gear set built on the rear axle. The final drive from shaft to axle is of the worm type which will be discussed later in the chapter. The clutch control pedal and the change gear control lever are outlined very clearly.
41. Modern Automobile Power Plants. — The automobile power plant includes the engine and all accessories necessary for the production of power. The transmission system includes the mechanism necessary for taking this power furnished by the power plant and transmitting it to the rear wheels.
In most cases, the power plant includes the engine and its component parts such as carburetor, ignition devices, cooling system, etc. and the
Hot water outlet-,^
Air heater
exhaust Co/a1 water
Cone -~ c/utch
'ater supply to pump
Water pump Magneto
FIG. 60. — Four-cylinder Wisconsin engine.
transmission system includes the clutch, change gears, universal joints, differential, and rear axle. When the unit power plant is used, it includes in addition to the engine and its essential component parts, the clutch and the change gears.
Four-cylinder Power PZante.— Figure 60 illustrates a typical four- cylinder automobile engine with the essential parts indicated. The view shown is the exhaust side of the motor, it having the T-head valve arrange- ment. The cylinders are cast in pairs, two cylinders being in each unit, he water jackets are cast integral with the cylinders. The water con- itions at the top and bottom of each casting are indicated. The clutch,
POWER-PLANT GROUPS
51
•Sfar~f/'n(j motot — generator-
FIG. 61.— The 1914 Cadillac engine.
52
THE GASOLINE AUTOMOBILE
FIG. 62. — Studebaker "Four" engine.
FIG. 63.— Section of Buda engine.
POWER-PLANT GROUPS
III 1 1
54
THE GASOLINE AUTOMOBILE
one member of which is machined in the engine flywheel, is of the cone type, this being the customary method of applying the cone clutch to the engine.
The engine of the 1914 Cadillac is illustrated from both sides in Fig. 61 s of the L-head type, having both intake and exhaust manifolds on
POWER-PLANT GROUPS 55
the right side. The most prominent feature of this engine is that the cylinders are cast singly with copper water jackets fastened securely around the castings. The single-cylinder castings necessitate a longer engine than if cast in pairs or en bloc, but they also make the renewal expense less if a single cylinder is damaged.
Figure 62 is a right-side view of the Studebaker "Four" engine, showing the en bloc cylinder construction, in which all cylinders are cast in one piece. This permits the engine to be much shorter than when cast in any other way. The structure is also more rigid, and can be made considerably lighter than when cast singly.
wafer oaf/ef Removable, cylinder \
head \ ft j. • connection
one clutch Cy/inc/ers cast en- bloc
FIG. 66.— Power plant of MitcheU "Six."
The sectional view of a Buda Model T engine in Fig. 63 shows very clearly the internal construction of an engine. This engine is of the L-head type with only one cam shaft. The crank shaft is of the con- ventional three-bearing type, i.e., with a bearing at each end and one at the center.
The Ford unit power plant is shown in section in Fig. 64 with all parts fully designated. The magneto, change gears and clutching ar- rangement are of considerable interest and will be discussed under the proper headings. As will be remembered, this power plant has three- point support.
56
THE GASOLINE AUTOMOBILE
Six-cylinder Power Plants. — The Jeffrey six-cylinder power plant is shown in section in Fig. 65. The cylinders are cast in pairs, thus permitting the use of a four-bearing crank shaft. In the pair of cylinders at the left, the section is taken through the valves so as to show the cams, push rods, springs, and valves. The center pair is sectioned through the center of the cylinders so as to show the pistons, pins, and con- necting rods. The valve arrangement is of the L-head type.
The engine of the "Mitchell Six of '16," Fig. 66, has the six cylinders cast "en bloc," which gives a very compact and rigid construction of pleasing appearance. The cylinder head can be removed in one piece for the purpose of cylinder and valve examination.
The Franklin motor, Fig. 67, represents a very interesting and unique design, having overhead valves and air-cooling. The cylinders are cast singly and each is air cooled by a system of cast ribs and air cooling, doing away with the water jackets around the cylinders. The
FIG. 67.— The Franklin air-cooled engine.
air is drawn downward around the cylinder ribs by the suction of the flywheel fan.
42. Constructional Features of Four- and Six-cylinder Engines.— The essential differences of construction in the various four- and six-cylinder engines, outside of the methods of cylinder construction and valve arrange- ment, consist in the construction and arrangement of the cam and crank shafts. Figure 68 is a conventional four-cylinder crank shaft, shown with connecting rods and pistons attached. There are three main bearings, as indicated. The connecting rod bearings are all in the same plane, bear- ings Nos. 1 and 4 being just 180° from Nos. 2 and 3. This means that the Nos. 1 and 4 pistons are in the same position in the cylinders at the same time. Likewise Nos. 2 and 3 are in the same position. If No. 1 piston is on the compression stroke, No. 4 must necessarily be on the exhaust stroke and Nos. 2 and 3 on the suction and explosion strokes,
POWER-PLANT GROUPS
57
The order of firing in a four-cylinder engine must be in the order 1, 3, 4, 2 or 1, 2, 4, 3.
The five-bearing crank shaft for a four-cylinder engine has main bear- ings between all the cranks. Figure 69 shows the five-bearing crank shaft
FIG. 68. — Three-bearing, four-cylinder crank shaft.
in place on the 1914 Cadillac four-cylinder engine. This type of crank- shaft construction is especially adapted to an engine with individually cast cylinders.
Chain drive for-
ajneto & oump
FIG. 69. — Five-bearing, four-cylinder crank shaft in position.
The crank shaft for a six-cylinder engine is arranged as shown in Fig. 70. Cranks 1 and 6, 2 and 5, 3 and 4 are in pairs and are spaced 120°
58
THE GASOLINE AUTOMOBILE
apart. The pistons in the paired cylinders are always in the same relative positions in the cylinders. The firing order of the cylinders is usually 1, 5, 3, 6, 2, 4 or 1, 2, 3, 6, 5,4. This crank has four main bearings. The
PISTON RINS PISTON
XNn SHAFT SEAR'NS
CONNECTING WOO BEARHMS •OH- DIPPER
CRANK SHAFT
CRANK SHAFT GBA«
/ 'STARTINS INUT
FIG. 70. — Four-bearing, six-cylinder crank shaft.
shaft shown in Fig. 71 has only three main bearings. The arrangement of the cranks is the same as in the previous case.
Matn bearings
FIG. 71.— Three-bearing, six-cylinder crank shaft.
In Figs. 72 and 73 are illustrated the two general methods of cam shaft construction. Figure 72 is a one-piece cam shaft, the cams and shaft
Fia. 72. — One-piece cam shaft.
being made of one solid bar of steel. This is the more common method of construction. The assembled cam shaft, Fig. 73, on which the individual cams are pinned or keyed is used at present in very few cases. The ob-
POWER-PLANT GROUPS
59
jection to this type of shaft is that the cams may become loose on the shaft and give considerable trouble. For an L-head engine, a single cam shaft on one side of the engine carries both inlet and exhaust cams. For
FIG. 73.— Assembled cam shaft.
FIG. 74. — Cadillac eight-cylinder V-type engine.
a T-head engine, however, one cam shaft carries the inlet cams on one side of the engine and another shaft carries the exhaust cams on the other side
60 THE GASOLINE AUTOMOBILE
The cam shafts are driven at one-half crank shaft speed. The drive can either be by a silent chain, such as shown for the 1914 Cadillac in Fig. 69, by spur gears such as in the Ford Model T shown in Fig. 64, or by helical gears such as shown in Figs. 72 and 73.
43. Eight- and Twelve-cylinder Power Plants. — In the four-cylinder engine, there is a power stroke every one-half revolution, but during a small interval at the end of each power stroke no power is being delivered by the engine. This means short periods in the operation of the engine in which the flywheel must supply all the power. In the six-cylinder engine,
FIG. 75. — Sectional view of Cadillac eight-cylinder engine.
there is a power stroke every one-third revolution and, as a result, there is an overlapping and a more continuous flow of power (see Fig. 54). The impulses come oftener and, consequently, reduce the vibration. The same effect is carried further in the eight-cylinder engine which gives a power stroke every one-fourth revolution. The parts are considerably lighter and this aids in reducing the vibration. Most of the eight-cylinder engines are built in the V-type and this method of construction adds to the smoothness of operation.
Cadillac Eight-cylinder Engine.— Figure 74 is a front-end view of the Cadillac eight-cylinder engine. The cylinders are arranged in blocks of
POWER-PLANT GROUPS
61
four each, placed in a V-shape at an angle of 90°. A cross section of two opposite cylinders is shown in Fig. 75. The engine is of the L-head type with the valves on the inside of the V. One cam shaft placed directly above the crank shaft operates all of the sixteen valves by means of the rockers as shown. Eight cams serve to operate the sixteen valves, as
FIG. 76. — A pair of Cadillac connecting rods.
FIG. 77.
one cam operates a valve in each group. The cam shaft is carried by five bearings and has a silent chain drive as shown in Fig. 74.
The crank shaft is like a conventional four-cylinder shaft with three main bearings. There are only four crank pins, two connecting rods, one from each group, bearing on the same crank. One of the rods, Fig. 76, is forked, while the other is perfectly straight, fitting in between the fork. The split bearing shown at the right fits directly over the pin. The forked
62
THE GASOLINE AUTOMOBILE
rod fits over this bearing and is pinned to it, so that the rod and bearing work together. The other rod fits in the center surface of the bearing and
LJ
FIG. 78.— Top view of Mitchell "Eight" engine.
FIG. 79. — Front view of Mitchell "Eight" engine.
runs on it. The arrangements permit the length of the crank shaft to be no greater than in a four-cylinder engine.
POWER-PLANT GROUPS
63
The order of firing of the eight cylinders alternates from one side to the other. If the cylinders be numbered as shown in Fig. 77 the firing order is as follows: 1-L, 2-R, 3-L, 1-R, 4-L, 3-R, 2-L, and 4-R. The horse power rating of the Cadillac Eight is 31.25 according to the S. A. E. formula. On dynamometer test, however, it has developed 70 hp. at a speed of 2400 r.p.m.
Mitchell Eight. — The Mitchell Eight is constructed on the same gen- eral principle as the type previously mentioned. The cylinder groups are placed in a V of 90°. The valves are placed on the inside of the V and
FIG. 80.— Engine of Packard "Twin Six."
are operated by means of eight cams on a single cam shaft mounted above the crank shaft. The cylinders are slightly staggered and two connecting rods are mounted side by side on each crank instead of using the forked construction.
The engine is rated at 48 hp. The cylinders are 3-in. bore by 5^- in. stroke. The top and front-end views are shown in Figs. 78 and 79.
The Packard Twelve-cylinder Engine. — The twelve-cylinder unit power plant of the Packard car is shown in Fig. 80. The twelve cylinders are cast in two blocks of six, arranged in V-type with an included angle of 60°. The cylinders have a 3-in. bore and a 5-in. stroke with L-head valve ar- rangement. The left block of cylinders is set forward of the right set by
64
THE GASOLINE AUTOMOBILE
\Y± in. in order to permit the lower end of the connecting rods of opposite cylinders to be placed side by side on the same crank pin. In addition, this arrangement permits the use of a separate cam for each valve, making 24 cams on the cam shaft. The single cam shaft is placed directly above the crank shaft. The crank shaft is of the usual six-cylinder type supported by three main bearings.
Advantages Claimed for Eight- and Twelve-cylinder Motors.— The chief advantages claimed by the eight- and twelve-cylinder motors are smooth running, lack of vibration, rapidity of pick-up, and wide range of activity
Flywheel
Clutch teathej
Clutch cone
Clutch release r/ny — — - — \
Transmission \ cose-
Clutch qear--*\ ^
Clutch brake
Clufch thrust bearing-
C/ufch spring
Crank shaft--
FIG. 81. — Buick cone clutch.
on high gear. It is possible with either of these types to run almost entirely on high speed under all conditions.
44. Clutches. — The gasoline engine must be set in motion before it will take up its cycle and generate power. This fact prevents it from being started under load and, consequently, means must be provided for de- taching the engine from the rest of the mechanism for starting before the load is thrown on. This mechanism for detaching the engine from the remaining part of the power and transmission system is called the "clutch." There are in use at the present time two general types of clutches, the cone type and the disc type.
The Cone Clutch. — Figure 81 illustrates the cone clutch as used in the Buick car. It consists of a leather-faced aluminum cone which is held
POWER-PLANT GROUPS 65
tightly against the inside of the tapered rim of the flywheel by four springs carried on a spider. The aluminum cone is mounted on a steel sleeve which can slide back and forth on the clutch gear shaft to disengage or engage the cone with the flywheel. A grooved ring at the rear end of the sleeve connects the clutch to the clutch pedal. A small brake, attached to the transmission case, serves to keep the clutch from spinning after it is released. Four small spring plungers, located under the leather, force it out at these points and prevent grabbing when the clutch is let in.
In operation, pressure on the clutch pedal is transmitted by a con- necting link and clutch release shaft to the yoke operating on the ball- bearing release ring, which pulls the clutch back out of engagement with the flywheel. The small brake now holds the clutch stationary, while the clutch spider and springs continue to turn with the flywheel until the clutch is again engaged. When in full engagement, the clutch and fly- wheel turn as a unit, transmitting the power through the gear set to the rear axle.
Multiple Disc Clutches. — The multiple disc clutch is built in two types — the dry plate and wet plate. Figure 82 is a sectional view of the dry plate type of clutch as used on the Hudson. It consists of a series of alternate driving and driven discs. The driving discs receive their power from the flywheel by four studs, one of which shows in the cut. These discs are steel stampings.
The driven discs are also steel stampings but are somewhat thicker and have holes into which cork inserts are pressed. The driven discs drive the inner drum by means of a series of grooves or slots.
The driven and driving discs are pressed together by the clutch spring shown. When it is desired to release the clutch, the foot pedal compresses the clutch spring and the plates separate, permitting the driving members to run independently of the driven members. As -in all clutches, the power is transmitted entirely through a frictional contact. The cork inserts are used because they are soft and at the same time have a great adhesive property, even if they become soaked with oil. The advantage of this type of clutching arrangement is that a large frictional surface can be obtained with a comparatively small clutch diameter. In the cone type this diameter must necessarily be large in order to get the necessary friction surface on the one surface in contact. In letting in the plain cone type of clutch, there is also the possibility of a more sudden engagement than with the multiple disc type. This has been overcome by the use of the springs under the leather, as shown in Fig. 81.
The wet plate clutch is constructed on the same general principles as the dry plate clutch, the essential difference being that it runs in a bath of oil. When the clutch is released, an oil film covers the entire surface of the plates and, when the clutch is thrown in, this film of oil is gradually
66 THE GASOLINE AUTOMOBILE
squeezed out, permitting a very easy and gradual engagement. In the winter time, the oil may be unusually heavy and this prevents a quick engagement. This can be overcome by thinning the clutch oil with kerosene.
FIG. 82. — Hudson dry plate clutch.
45. Change Gear Sets. — The change gear set is for the purpose of permitting different speed ratios between the engine and the car. When starting, the engine must run comparatively fast and the car slow. When the car gets under way, the relative speed of car and engine must be changed in order to get efficient operation.
Figure 83 is the gear set used on the Jeffrey car. The right shaft is driven by the clutch; attached to this shaft is the drive gear which at all time drives the lay-shaft drive gear fastened to the lay-shaft. The lay shaft in addition carries four fixed gears as shown. The main drive shaft has one end bearing rotating within the main drive gear. Con- sequently the drive gear and main shaft can run independently of each other. The main shaft carries two sets of sliding gears, the names and purposes of which are indicated. These two sets are operated by two
POWER-PLANT GROUPS
67
shifter yokes which lead to the gear control lever in the car. This gear set provides four forward speeds and a reverse speed. This type is known as the "selective sliding gear set," because, as the name in- dicates, any one of the speeds can be selected at will, in contrast to the "progressive sliding gear set" in which the speeds must be taken in succession.
Figure 84 illustrates the gear positions for the various speeds obtained in the Studebaker three-speed-and-reverse gear set. The white arrows indicate the gears through which the power is transmitted for the different speeds.
SHIFTS R BOO C»P f ROOT
IDtNGGCAR )**
FIG. 83. — Jeffrey gear set.
46. Planetary Gearing. — This type of combined clutch and change gears, such as used on the Ford Model T, is especially adapted to light cars in which two forward speeds are sufficient. The gears are not shifted into or out of mesh for the different speeds, as in the sliding gear set, but they are always in mesh, as shown in Fig. 85. On high gear, the entire mechanism is clamped solidly together by the clutch and revolves as a single mass with the flywheel. The clutch is of the multiple disc type, running in oil. The flywheel has three studs, each of which carries three gears of different sizes fastened together to form what is called a "triple gear." These triple gears mesh with three gears of different sizes in line with the engine shaft. The inner one, next to the flywheel face, is fast-
68
THE GASOLINE AUTOMOBILE
TE
' REVERSE IDLER GEAR L"
'"---PINION SHAFT C
FIRST SPEED OR" LOW"
OR INTERMEDIATE
THIRD OR "HIGH" SPEED
REVERSE
FIG. 84. — Positions of gears in Studebaker three-speed-and-reverse gear set.
POWER-PLANT GROUPS
69
ened to the drive shaft which delivers the power through to the rear axle. The other two central gears float on the drive shaft and are connected to the two drums nearest to the engine. Surrounding these drums, but not shown in the figure, are brake bands which can be tightened by foot pedals. These can be seen in Fig. 64. If the slow-speed drum is gripped, the second of the three central gears will be held stationary. This makes the triple gears rotate on their studs as the flywheel revolves. In doing this, they drive the inner central gear, or the driving gear, slowly forward,
FIG. 85. — Ford planetary transmission.
due to the differences in the sizes of the gears. If the middle drum is gripped instead, by pushing on the reverse pedal, the larger of the central gears is held. This makes the triple gears revolve again on their studs as the flywheel revolves, but since this reverse gear is larger than the drive gear, the motion of these triple gears will turn the drive gear slowly back- ward. For high speed, the entire mechanism is gripped solidly together so that it revolves at engine speed. The third drum is used for a service brake.
47. Universal Joints and Drive Shaft. — The use of one or more univer- sal joints between the power plant and the rear axle is necessary, as can be seen in Fig. 59, in order to provide for the lower position of the rear axle and also to allow for the spring action between the axle and the frame which carries the power plant. The universal joint permits this to be done with very little loss of power. Figure 86 shows the propeller shaft or drive shaft of the Jeffrey car with its universal joints. A square block in the center of the universal joint fits between the jaws of two forks, one of which is connected to the power plant and the other is attached to the
70
THE GASOLINE AUTOMOBILE
end of the drive shaft. The flexible connection of these forks to the block permits the drive shaft to oscillate freely with the rear axle and yet con- tinue to receive and transmit power.
ftANOE YOKE
COMPLETE UNIVERSAL JOINT
LOCIT RIN8 D
FIG. 86. — Jeffrey propeller shaft and universal joints.
48. Final Drive. — The final drive to the rear axle is accomplished by means of bevel, spiral-bevel, or worm gearing. The direction of the power transmission must be changed through a right angle at this point. Figure 87 shows the bevel gear final drive as used on the Jeffrey car. Both the bevel pinion and the differential housing which carries the driving gear or ring gear are carried by ball bearings. The action of the bevel gears
FIG. 87.— Jeffrey final drive.
produces a side thrust, caused by the inclination of the faces of the teeth, tending to separate the gears. This makes it necessary that the bearings of these gears be capable of resisting this thrust. Either ball bearings or tapered roller bearings are employed. If the straight rollers are used for bearings, special thrust bearings must be provided.
"Figure 88 shows a spiral-bevel gear drive with the Timken tapered
POWER-PLANT GROUPS
71
roller bearings, as used on the Cadillac car. The chief claims for the spiral-bevel drive are that the spiral teeth give a more continuous driving action between the teeth and overcome any possible inaccuracies in the teeth or any tendencies to wear irregularly; also that they overcome the thrust, to a more or less extent, by producing a counteracting pull.
Fig. 89 shows the worm drive to the rear axle. This has the worm placed above the gear. The worm drive in Fig. 59 shows one with the
worm placed underneath. The worm drive is very quiet running, but requires careful lubrication because of the con- stant sliding action between the teeth of the worm and gear. One of the two gears should run in an oil bath. The worm drive is especially popular in
FIG. 88.— Cadillac spiral-bevel drive.
FIG. 89. — Worm drive used on Jeffrey "Chesterfield Six."
heavy truck service where there is a large reduction in speed. The worm is generally made of steel and the gear of bronze to keep down the friction.
49. Types of Live Rear Axles. — The dead rear axle was illustrated and explained in Chap. I. The live axle is used on practically all makes of pleasure cars, with only one or two exceptions. Live rear axles are clas- sified according to their methods of construction as simple, semi-floating, three-quarter floating, and full floating.
Simple Live Axle. — The simple live axle used on the Ford Model T is shown in Fig. 90. This type of rear axle performs two functions in that it carries the entire weight of the rear of the car in addition to transmitting the power. The rear wheel is keyed to the axle as shown. The weight
72
THE GASOLINE AUTOMOBILE
is carried by roller bearings directly on the live axles both at the wheel and differential ends.
Semi- floating Axle. — Figure 91 is of the semi-floating type and shows
ICJOiif
the essential difference between a simple and semi-floating live axle. In
the semi-floating axle the inner bearings are carried on an extension of the
Qtial.case, thus relieving this end of the live axle of considerable
POWER-PLANT GROUPS 73
stress. The wheel as in the other case is keyed to the axle. The con- struction at the outer end of the semi-floating axle is the same as in the simple axle. In either of these types the weight of the car produces a bending stress in the axle.
Three-quarter Floating Axle. — Figure 92 shows the change in this type of construction from the semi-floating type. The weight is carried by the bearings on the housing and directly in line with the spokes, thus re- lieving the axle of all bearing stresses. The wheel is keyed onto the shaft.
FIG. 91. — Semi-floating rear axle.
Although in the three-quarter type the live axle is relieved of all weight, nevertheless the bending strains due to a possible side movement of the wheel, or the distortion due to a bent housing are still thrown on the axle due to the fact that the wheel is keyed onto the axle. Also, in this type, if the live axle breaks, the wheel can come off and let the car drop. This is prevented only by the full-floating construction.
Full-floating Rear Axles. — Figure 93 shows the full-floating construc- tion as used on the Buick car. The wheel is carried on a double ball or roller bearing on the axle housing, in such a way as to retain the wheel on the housing regardless of what may happen to the live axle. In this construction, the live shaft receives only the torsional strains of driving the car, all other loads being taken by the axle housing. The live shaft may be removed and replaced without disturbing either the wheel or the
74
THE GASOLINE AUTOMOBILE
differential. The inner ends of the axle shafts are grooved and slide into corresponding grooves in the differential gears. The entire drive shaft on either side may be removed by merely removing a hub cap and sliding the shaft out. In the form shown in Fig. 93, the shaft is keyed into the
FIG. 92. — Three-quarter floating axle construction.
GIVING YOKE
ADJUSTM£MJ
- PROPELLER SHAFT HOUSING BRACE fiODS PROPELLER SHAFT
SRAKC. OPERATING SHAFTS
BRAKE DRUM """
CREASE PLUC
DRIVtMC FLANGE HUB BEAR/NO
FIG. 93.— Buick full-floating rear axle.
hub cap. In another form, the outer end of the shaft has a toothed clutch which fits into corresponding recesses in the outer face of the hub. This permits a certain amount of play and relieves the shaft from any distor- tion if the axle housing becomes bent.
CHAPTER IV FUELS AND CARBURETT1NG SYSTEMS
One of the most important operations in a gas engine is that of getting an explosive mixture inside of the engine cylinder at the proper time. This explosive mixture is formed by the thorough mixing of air and a gas formed by the evaporation of a volatile liquid fuel, usually gasoline.
50. Hydrocarbon Oils. — Most of the liquid fuels are known as "hydrocarbon" oils, because they are made from crude mineral oil con- taining as its principal parts, hydrogen and carbon. One of the hydro- carbon fuels, viz., alcohol, is not of mineral derivation, but is made by the distillation of vegetable matter.
The crude oil or petroleum from which the hydrocarbon fuels are made is found in natural deposits several hundred feet below the earth's surface. In some places it has to be pumped out, while in others it is forced out by natural gas pressure. Most of the crude oil found in the United States comes from Pennsylvania, Ohio, Illinois, Kansas, Texas, Oklahoma and California. These crude oils are of two general types, that coming from Texas, Oklahoma, and California having what is known as an "asphalt" base, and that from Pennsylvania and Ohio having a "paraffin" base. Crude oil having an "asphalt" base is a heavy dark liquid, which when boiled, leaves a black tarry residue. If the crude oil has a "paraffin" base, it is much lighter in weight and color and, when boiled, leaves a residue from which is made the white paraffin or wax with which everyone is familiar.
Formerly, gasoline made from crude oil with a paraffin base was sup- posed to be of a higher grade than the other, but with the modern proc- esses of refining, the gasoline from the two kinds of crude oil gives equally good results.
51. Fractional Distillation of Petroleum. — The crude oil is heated in large retorts or "stills," provided with accurate temperature recording devices. When the temperature has reached about 100°F. a vapor be- gins to rise from the oil. This vapor is collected from the top of the retort and condensed in cooling coils, from which the liquid is collected in vessels. As the temperature in the retort rises, the vapor becomes heavier and, when condensed, gives the heavier and less volatile liquid fuels. The following table gives, approximately, the products of this method of distillation :
75
76 THE GASOLINE AUTOMOBILE
Distilling at IOO°F to I25°F Hiqhly Volatile oils -qasoline, benzine, naphtha, ICTtolB%.
Distilling at 125* F to 350*F. Kerosene and light lubricat- ing oils; 65 to
Distilling at over 35O'F Heavy oils, paraffin wax, etc, 15 to 20%
FIG. 94. — Approximate fractions in the distillation of crude oil.
Temperature in the retort
Kind of oil after condensing the vapor
Percentage
|
100°F to 125°F. 125°F. to 350°F. Over 350°F. |
Highly volatile oils (gasoline, benzine and naphtha). Kerosene and light lubricating oils. Heavy oils, paraffin wax and residue. |
10 to 15 per cent. 65 to 75 per cent. 15 to 20 per cent. |
It will be noticed that there is from three to five times as much kerosene and light lubricating oils produced under this method as there is gasoline. This accounts for the late scarcity of gasoline and the more volatile fuels, and the overproduction of kerosene and the less volatile fuels, which can not be used successfully in an automobile engine.
In order to utilize a part of these less volatile fuels, the Standard Oil Co. has developed the Burton process by which these less volatile fuels are redistilled under pressure. This process gives an additional amount of volatile fuel very much like the gasoline obtained from the first distilla- tion. This process has increased the percentage of gasoline from the crude oil to such an extent that the market is now liberally supplied.
The Bureau of Mines has recently developed the new Rittman process for increasing the amount of gasoline produced from the crude oil. It is a continuous process, in contrast to the "batch" Burton process. The two processes are somewhat similar in character and have as their end an increase in the production of gasoline from the crude oil.
62. Principles of Vaporization. — Before an explosive mixture can be formed, the liquid fuel must first be turned into a gas and then mixed with the proper amount of air to burn it. As we know, it requires heat to
FUELS AND CARBURETTING SYSTEMS 77
change water into steam or vapor. If the water is out in the open, it will evaporate rapidly, or boil, at a temperature of 212°. Likewise, in order to change a liquid fuel into a gas or vapor, it is necessary that heat be added to it, but the temperature at which this heat is added is different for different fuels. For instance, gasoline will evaporate under the usual atmospheric pressure and temperature and will, in some cases, evaporate at a temperature close to 0° F. This can be tested by exposing a pan of gasoline to the air. In a short time the liquid will have evaporated. That heat has been absorbed can be verified by feeling of the dish before it is filled and again after evaporation has been taking place.
Kerosene and alcohol, on the other hand, will not evaporate until heat is added from an external source at a higher temperature, the same as is done when steam is made from water. This explains the difficulty of evaporating these fuels for use in a gas engine.
From the above considerations, the general principles of vaporization are formulated :
1. The heavier a liquid and the higher its boiling point, the harder it will vaporize; for example, kerosene as compared with gasoline.
2. A liquid fuel will vaporize easier and faster under a suction, or re- duction of pressure than under pressure ; for example, gasoline is more dif- ficult to vaporize at low than at high altitudes.
3. The closer the temperature of a liquid fuel is to its boiling point, the easier and faster it will vaporize; for example, gasoline will vaporize more readily in summer than in winter.
The Baume Test. — Gasoline is usually spoken of as high or low test. By reference to the principles of vaporization, we see that the heavier a liquid, the harder it is to evaporate. This principle explains the reason for the use of the Baume" test. A hydrometer, such as shown in Fig. 95 is graduated in degrees, the numbers reading from the bottom up. These degrees have nothing to do with thermometer degrees, but are named after Baume, who originated the idea. When the hydrometer is placed in a quantity of gasoline, it will sink to a depth corresponding to the density of the liquid. It will sink deeper in a light gasoline than in a heavier one. The deeper the hydrometer sinks, the higher the scale read- ing will be. This scale, reading from 45 to 95° Baume", indicates in an indirect way the ease and rapidity with which the gasoline will evapo- rate. It is not a direct and absolute test unless the nature and the boiling points of the crude oil from which the gasoline has been distilled are known. For most purposes, however, it merely serves as a guide as to the way the gasoline will act in service.
Gasoline. — The commercial gasoline of today has a Baume" test of from 50 to 65°, the better or high test being in the neighborhood of 65° and the poorer, or low test, in the neighborhood of 50°. For summer
78
THE GASOLINE AUTOMOBILE
use, the low test or heavier gasoline can be used very .well because it will evaporate with comparative ease at the usual summer temperatures, but in the winter the high test or light gasoline is to be preferred because it will evaporate more easily at the low temperatures. More work can be obtained from a gallon of the heavier or low test gasoline, providing it is completely vaporized, but it is very difficult to vaporize at low tempera- tures and consequently makes starting very hard in cold weather.
Kerosene Gasoline
FIG. 95. — Baum6 hydrometer in kerosene and gasoline.
Occasionally, a low grade, impure gasoline is sold which lacks sufficient refinement and purification, the sulphur and other impurities not having been eliminated. The use of this may result in carbon deposits in the cylinders. A gasoline that readily carbonizes should be avoided and a higher grade used.
Kerosene and Alcohol. — To use either of these fuels requires the heating of the fuel or the air, or both, in order to secure vaporization. At pres- ent, the price of alcohol is too high to warrant giving any serious con- sideration to its use. Several more or less successful devices have been tried for using kerosene, but the varying speeds and loads of the auto-
FUELS AND CARBURETTING SYSTEMS 79
mobile engine make the problem of controlling the heat very difficult. The reductions in the price of gasoline in the past 2 or 3 years and the very promising prospects for a greater increase in the supply and corre- sponding reduction in the price, make it unlikely that any great develop- ment in the use of kerosene will take place. Consequently, the discussion to follow will deal only with gasoline and its vaporization.
53. Heating Value of Fuels. — The heating value, or the amount of heat energy contained in a liquid fuel, is given in British thermal units per pound; a British thermal unit, or a B.t.u., being the quantity of heat energy required to raise the temperature of 1 Ib. of water 1° on the Fahrenheit scale. The following table gives the heating values of the common fuels:
Gasoline 18,000 to 19,500 B.t.u. per pound. Kerosene about 20,000 B.t.u. per pound, grain about 10,000 B.t.u. per pound.
Alcohol ^ wQod about 7)5(X) B t u per pound
Inasmuch as the heavier fuel contains more pounds per gallon, and as gasoline and kerosene are sold by the gallon, a gallon of heavy or low test gasoline or of kerosene contains more energy and gives more power than a gallon of light, or high test gasoline.
54. Gasoline Gas and Air Mixtures. — It is necessary when the gaso- line is vaporized that it be mixed with the proper amount of air to form an explosive mixture. If too little air is furnished, there will not be enough oxygen to burn the carbon and hydrogen in the fuel and the fuel will be wasted, as will be indicated by black smoke coming from the exhaust. If too much air is furnished, the mixture is weak in fuel, giving a very slow combustion. This results in lost power. A weak mixture, or an excess of air, is indicated by back-firing through the carburetor.
A definite mixture of gasoline gas and air is necessary for the efficient operation of a gasoline engine. The function of the carburetor is to take the gasoline, vaporize it, and furnish the proper mixture of gas and air to the cylinders under all conditions of temperature, speed, load, power and varying atmospheric conditions.
55. Principles of Carburetor Construction. — Most of the modern types of carburetors are of the spray or nozzle type, in which a jet of gaso- line is sprayed into a current of air to form an explosive mixture. Figure 96 illustrates an elementary spray carburetor. The gasoline supply tank is placed below the carburetor and the gasoline is pumped up through the supply pipe. The overflow pipe maintains the level of the liquid at a constant height. The standpipe T is connected with the supply chamber C by means of the connection N and the flow is regulated by the needle valve S. The gasoline level in the standpipe T is always the same. The flange B is fastened onto the intake passage of the engine. The sue-
80
THE GASOLINE AUTOMOBILE
tion of the piston draws air through the opening A upward past the stand- pipe, and at the same time draws a spray of gasoline from T. The but- terfly valve D is for the purpose of regulating the suction upon the stand- pipe T when starting the engine; when running, the valve D should be wide open. The mixture is changed by regulating the needle valve 8. This type of carburetor can be used only on constant speed engines, the reason for which we will see later. Figure 97 shows another elementary type of carburetor which illustrates the application of two modern ideas. In this case, the gasoline supply is maintained at a constant level by means of a hollow metal or a cork float operating a ball valve. The
Fro. 96.
FIG. 97.
arrangement requires the gasoline supply tank to be placed above the carburetor or that some other means be provided for supplying gasoline under pressure. It will also be noticed that the passage surrounding the standpipe or spray nozzle is contracted, giving the inside surface a convex shape. This is the application of the well known Venturi tube principle. By contracting the section near the opening of the nozzle the velocity of the incoming air and consequently the suction at that point are increased, making it much easier for the gasoline to be taken up and greatly facili- tating the starting of an engine when the suction is low.
This type of carburetor could be used on constant speed engines only. If a carburetor such as shown in Figs. 96 or 97 was put on a variable speed engine and the proper adjustment made by means of the needle valve so that the mixture proportions were correct at low speed, and the engine should then be speeded up, we would discover black smoke coining from the exhaust, indicating an excess of gasoline over the air supplied. This is due to the fact that under the increased suction due to the higher speeds of the piston, the air drawn in past the standpipe expands and increases in volume and velocity faster than it increases in weight; while the gasoline drawn from the nozzle, being a liquid, increases in weight just as its velocity and volume are increased. This means that under an increased suction too much gasoline is supplied for the amount of air drawn in.
FUELS AND CARBURETTING SYSTEMS 81
In order to keep the mixture of the proper proportions at all speeds of the engine, it is necessary to have an auxiliary air entrance, such as indicated at X in Fig. 98, to admit an additional amount of air at the higher engine speeds. This entrance is usually in the form of a valve controlled by a spring, the tension on which can be changed to control the air admission. For low speed adjustments the gasoline needle valve is to be used, and for high speed adjustments the auxiliary air valve is to be adjusted. That is, when the engine is running comparatively slowly, the air is taken in through the ordinary air opening A shown below the valve in Fig. 98.
FIG. 98. FIG. 99.
FIGS. 98 AND 99. — Sections of typical variable speed carburetors.
The mixture is then proportioned by means of the needle valve NV. When the engine speeds up, and the suction is increased, the auxiliary air valve S in Fig. 98 comes into action and opens. If it is found that the mixture at high speeds is too rich, that is if there is too much fuel for the air furnished, it indicates that the tension on the valve spring is too great, which prevents sufficient air from entering. By reducing the tension, the valve opens wider, letting in sufficient air to keep the mixture uniform. If the mixture is too weak at high speeds, the spring tension is too weak. It should be tightened so as to permit less air to enter and to increase the suction on the gasoline.
The following general description applies to Fig. 98.
G = gasoline feed from tank. FV = float valve controlling flow of gasoline to carburetor.
F = float, the height of which is regulated by the level of gasoline in the float
chamber. The float controls the float valve FV.
NV = gasoline needle valve for regulating the amount of gasoline furnished to the air in the mixing chamber.
N = gasoline nozzle.
X = auxiliary air valve, to admit additional air at the high speeds.
S = spring for X.
A = primary air opening, which supplies all air at low speeds.
T = throttle valve for regulating supply of mixture from carburetor to cylinder.
P = primer for depressing float and flooding carburetor to insure rich mixture when starting.
82
THE GASOLINE AUTOMOBILE
Figure 99 shows another carburetor, in which the auxiliary air is ad- mitted through ports X controlled by steel balls B.
Some of the modern types of carburetors are water-jacketed, taking the hot water from the cooling system, in order to heat the carburetor and assist the vaporization. Another method of assisting the vapori- zation, and one almost necessary when the low grade gasoline of today is considered, is that of heating the air which goes into the carburetor. This is usually done by taking it through a jacket surrounding the ex- haust pipe. Figure 100 shows such a device.
FIG. 100. — Hot-air connection used with Master carburetor.
Another scheme used in several of the carburetors built for high powered, high speed machines is the double-jet, which makes it easier for the engine to draw the desired amounts of gasoline and air when it becomes necessary for the engine to carry heavy loads at high speed. Several of these are illustrated in the following articles, which describe some of the leading carburetors now in use.
FIG. 101.— Schebler Model L carburetor.
56. Schebler Model L Carburetor.— The Model L carburetor, Figs. 101 and 102, is of the lift-needle type and is so designed that the amount of fuel entering the motor is controlled by means of a raised needle work- ing automatically with the throttle. The flow of gasoline can be adjusted
FUELS AND CARBURETTING SYSTEMS
83
for closed, intermediate, or open throttle positions, each adjustment being independent and not affecting either of the others. This carburetor has an automatic air valve, shown at the left in Fig. 102. At high speeds or heavy loads, the suction raises this valve and admits an extra supply of air. The opening of the throttle for high speed or a heavy pull raises the needle and increases the supply of gasoline to correspond with the increased air supply.
The Model L can be furnished with a bend for connecting or taking warm air from around the exhaust manifold into the initial air opening at the base of the carburetor, by means of a hot air drum and tubing.
FIG. 102. — Section of Shebler Model L carburetor.
This carburetor is also manufactured with a dash-control to the air valve spring, this being operated by a lever which is controlled by a switch on the dashboard or steering post of the car. This control is shown on Fig. 102.
Rules for Adjusting Schebler Model L. — The carburetor should be connected to the intake manifold so that it is located below the bottom of the gasoline tank a sufficient distance to be filled by gravity under all running conditions. Where pressure feed is used, it is unnecessary to locate the carburetor below the gasoline tank; also, when pressure is used, it is never advisable to carry over 2 Ib.
Before adjusting the carburetor, make sure that the ignition is prop- erly timed; that there is a good hot spark at each plug; that the valves are properly timed and seated; that all connections between the intake valves and the carburetor are tight; and that there are no air leaks of any kind
84 THE GASOLINE AUTOMOBILE
in these connections. The carburetor should be adjusted to the motor under normal running temperature, and not to a cold motor.
In adjusting the carburetor, first make the adjustments on the auxili- ary air valve so that the air valve seats lightly but firmly. The lever on the dash control should be set in the center of the dashboard adjuster, and with this setting of the lever, the tension on the air valve should be light, yet firm. Close the needle valve by turning the adjustment screw to the right. until it stops. Do not use any pressure on this adjustment screw after it meets with resistance. Then turn it to the left about four or five turns and prime or flush the carburetor by pulling up the priming lever and holding it up for about 5 seconds; Next, open the throttle about one-third and start the motor; then close the throttle slightly, retard the spark, and adjust the throttle lever screw and the needle valve adjusting screw, so that the motor runs at the desired speed and hits on all cylinders.
After getting a good adjustment with the motor running idle do not touch the needle valve adjustment again, but make your intermediate and high speed adjustments on the dials. Adjust the pointer on the first dial about half way between figure 1 and figure 3. Advance the spark and open the throttle so that the roller on the track running below the dials is in line with the first dial. If the motor back-fires with the throttle in this position and the spark advanced, turn the indicator a little more toward figure 3; if the mixture is too rich, turn the indicator back, or toward figure 1, until you are satisfied that the motor is running properly with the throttle in this position, or at intermediate speed. Now open the throttle wide and make the adjustment on the second dial for high speed in the same manner as you have made the adjustments for intermediate speed on the first dial.
67. Schebler Model R.— The Model R Schebler carburetor, Fig. 103, is designed for use on both four- and six-cylinder motors. It is a single-jet raised-needle type of carburetor, automatic in action. The air valve controls the lift of the needle so as to automatically proportion the amount of gasoline and air at all speeds.
The Model R carburetor is designed with an adjustment for low speed. As the speed of the motor increases, the air valve opens, raising the gaso- line needle and thus automatically increasing the amount of fuel. This carburetor has but two adjustments, the low speed needle adjustment, which is made by turning the air valve cap, and an adjustment on the air valve spring for changing its tension.
The Model R carburetor has an eccentric which acts on the needle valve, intended to be. operated either from the steering column or from the dash, and insures easy starting, as, by raising the needle from the seat, an extremely rich mixture is furnished for starting and for heating up the
FUELS AND CARBURETTING SYSTEMS
85
motor in cold weather. A choke valve in the air bend is also furnished. The dashboard control or steering column control must be used with this carburetor; it cannot be operated satisfactorily without them.
Rules for Adjusting Model R Carburetor. — When the carburetor is installed, see that lever B is attached to the steering column control or dash control so that when boss D of lever B is against stop C the lever on the steering column control or dash control will register "Lean" or "Air." This is the proper running position for lever B.
FIG. 103.— Schebler Model R carburetor.
To adjust the carburetor turn the air valve cap A clockwise or to the right until it stops, then turn it to the left or anti-clockwise one complete turn.
To start the engine, open the throttle about one-eighth or one-quarter way. When the engine is started, let it run till it is warmed, then turn the air valve cap A to the left or anti-clockwise until the engine hits perfectly. Advance the spark three-quarters of the way on the quadrant; then if the engine back-fires on quick acceleration, turn the adjusting screw F up (which increases the tension on the air valve spring) until acceleration is satisfactory.
Turning the air valve cap A to the right or clockwise lifts the needle E out of the nozzle and enriches the mixture; turning to the left or anti- clockwise lowers the needle into the nozzle and makes the mixture lean.
86 THE GASOLINE AUTOMOBILE
When the motor is cold or the car has been standing, move the steer- ing column or dash control lever toward "Gas" or "Rich." This oper- ates the lever B and lifts the needle E out of the gasoline nozzle and makes a rich mixture for starting. As the motor warms up, move the control lever gradually back toward "Air" or "Lean" to obtain best running conditions, until the motor has reached normal temperature. When this temperature is reached, the control lever should be at " Air " or "Lean." For best economy, the slow speed adjustment should be made as lean as possible.
68. The Holley Model H Carburetor. — This carburetor is shown in Fig. 104. Before the fuel enters the float chamber, it passes a strainer
FIG. 104.— Holley Model H carburetor.
disc A which removes all foreign matter that might interfere with the seating of the float valve B under the action of the cork float, and its lever C.
Fuel passes from the float chamber D into the nozzle well E through a passage F drilled through the wall separating them. From the nozzle well, the fuel enters the cup G through the hole H, and rises past the needle valve, /, to a level which partially submerges the lower end of a small tube, J, having its outlet K at the edge of the throttle disc.
FUELS AND CARBURETTING SYSTEMS 87
Cranking the engine, with the throttle kept nearly closed, causes a very energetic flow of air through the tube J and its calibrated throttling plug K. But with the engine at rest the lower end of this tube is partially submerged in fuel. Therefore, the act of cranking automatically primes the motor. With the motor turning over under its own power, flow through the tube J takes place at very high velocity, thus causing the fuel entering the tube with the air to be thoroughly atomized upon its exit from the small opening at the throttle edge. This tube is called the "low speed tube" because, for starting and idle running, all of the fuel and most of the air in the working mixture are taken through it.
As the throttle opening is increased beyond that needed for idling of the motor, a considerable volume of air is drawn down around the outside of the strangling tube L and then upward through this tube. In its pas- sage into the strangling tube, the air is made to assume an annular, con- verging stream form, so that the point in its flow at which it attains its highest velocity is in the immediate neighborhood of the upper end of the ' ' standpipe " M . The velocity of air flow being highest at the upper or outlet end of the standpipe, the pressure in the air stream is lowest at the same point. For this reason, there is a pressure difference between the top and bottom openings of the pipe M , thus causing air to flow through it from bottom to top, the air passing downward through the openings N in the bridge supporting the standpipe and then up through the standpipe.
With a very small throttle opening, the action through the standpipe keeps the nozzle cup thoroughly cleaned out, the fuel being carried directly from the needle opening into the entrance of the standpipe. . To secure the best vaporization of the fuel, the passage through the standpipe is given an aspirator form, which further increases the velocity of flow through it, and insures the greatest possible mixing of the fuel with the air. A further point is that the vaporized discharge of the standpipe enters the main air stream at the point at which the latter attains its highest velocity and lowest pressure.
There is but one adjustment, that of the needle valve /. The effect of a change in its setting is manifest over the whole range of the motor.
59. Holley Model G. — This carburetor, Fig. 105, is a special design for Ford cars.
The operation of this carburetor is the same as the regular Model H already illustrated and described. The chief differences are the structural ones giving a horizontal instead of a vertical outlet, a needle valve con- trolled from above instead of from below, and a simplification of design to secure compactness.
Fuet enters the carburetor by way of a float mechanism in which a hinged ring float, in rising with the fuel, raises the float valve into contact
88 THE GASOLINE AUTOMOBILE
with its seat. This seat is removable and the float valve is provided with a tip of hard material.
From the float chamber the gasoline passes through the ports E to the nozzle orifice, in which is located the pointed end of the needle F. The ports E are well above the bottom of the float chamber, so that, even should water or other foreign matter enter the float chamber, it would have to be present in very considerable quantity before it could interfere with the operation of the carburetor. A drain valve D is provided for the purpose of drawing off whatever sediment or water may accumulate in the float chamber.
FIG. 105.— Holley Model G carburetor.
The float level is so set that the gasoline rises past the needle valve F and sufficiently fills the cup G to submerge the lower end of the small tube H. Drilled passages in the casting communicate the upper end of this tube with an outlet at the edge of the throttle disc. The tube and passage give the starting and idling actions, as described in connection with the Holley Model H.
The strangling tube / gives the entering air stream an annular con- verging form, in which the lowest pressure and highest velocity occur immediately above the cup G; thus it is seen that the fuel issuing past the needle valve F is immediately picked up by the main air stream, at the point of the latter's highest velocity.
The lever L operates the throttle in the mixture outlet. A larger disc with its lever S forms a spring-returned choke valve in the air intake, for starting in extremely cold weather.
FUELS AND CARBU RETTING SYSTEMS
89
60. Stewart Model 25. — This carburetor, which is manufactured by the Detroit Lubricator Company, involves an interesting principle of operation.
Figure 106 gives a cross section of this carburetor and shows the posi- tion of the air valve with engine running and air and gasoline being admitted.
With the engine at rest and no air passing through the carburetor, the air valve A rests on the seat B, closing the main air passage. The gasoline rises to a height of about 1^ in. below the top of the central aspirating
FIG. 106. — Stewart Model 25 carburetor.
tube L. As soon as the engine starts to rotate, a partial vacuum is formed above the air valve, causing it to lift from its seat and admit air, at the same time gasoline being drawn up through the aspirating tube L. The lower end of the air valve extends down into the gasoline and around the metering pin P. Due to the decreasing diameter of this pin, the higher the air valve is lifted the larger will be the opening into the tube L, and the more gasoline will be drawn up. The upper end of the air valve meas- ures the air, the lower end measures the gasoline; therefore, as the suction varies, the air valve moves up or down and the volume of air and the amount of gasoline admitted to the mixing chamber increase or decrease in the same ratio. Most of the air passing through the carburetor goes through the air passages as indicated by the black arrows. A -small amount is drawn through the drilled holes HH and past the end of the
90
THE GASOLINE AUTOMOBILE
tube L. The flared end of this tube deflects the air through a small an- nulus, thereby increasing the velocity of air at this point so as to aid in atomizing the fuel.
The air valve is restrained from any tendency to flutter, caused by the intermittent suction of the cylinders, by the dash pot D. Due to the greater inertia of the gasoline and because it flows comparatively slowly through the small opening and into the dash pot, the air valve can rise or fall only as liquid is expelled or admitted and thus the air valve is held steady. The Stewart carburetors have but one adjustment, which raises or lowers the metering pin, thereby decreasing or increasing the amount of gasoline admitted to the mixing chamber. The correct position of the metering pin is determined with the motor running at idling speed. This adjustment may be manipulated at the dash to compensate for extreme changes in atmospheric temperatures and for use in starting in cold weather.
61. Kingston Model L. — Figure 107 shows the construction of this car- buretor. Gasoline enters the carburetor from the tank at the connection A and is maintained at a constant level, through the agency of the float.
A pool of gasoline forms in the base of the U-shaped mixing tube and will always be present when the motor is not run- ning. This aids in positive starting. When the motor starts, this pool is quickly lowered to the point of adjust- ment of the needle valve and continues to feed from this point till the motor is stopped.
When the motor is running slowly, the air valve B rests lightly on its seat, allowing no air to pass through; con- sequently all air must pass through the low speed mixing tube C. Due to the lower end of this tube being close to the spray nozzle and all the low speed air having to pass this point, the atomized gasoline drawn from nozzle D becomes thoroughly mixed with air in its upward course and is carried in this state to the motor. When the throttle is opened slowly, the following action takes place. The motor now requires a greater volume of mixture. The air valve B slowly leaves its seat, permitting an extra air supply to enter and compen- sate for the increased flow of gasoline produced by the greater suction of the motor. In this carburetor the extra amount of gasoline for the starting and warming up period can be obtained by opening the needle valve .adjustment at the dash or by the use of the choke throttle E placed in the air passage,
FIG. 107.— Kingston Model L carburetor.
FUELS AND CARBURETTING SYSTEMS 91
When starting with a cold motor, this choke throttle can be closed by pulling the wire forward. This cuts off nearly all the air supply and pro- duces a very strong suction at the spray nozzle, which causes the gasoline to jet up and be carried with the incoming rush of air to the cylinders.
A drain cock G is placed at the lowest point in the bowl and should be opened from time to time to free the bowl of all water and foreign matter.
Rules for A djusting Kingston Model L. — Retard the spark fully. Open the throttle about five or six notches of the quadrant on the steering post. Loosen the needle valve binder nut on the carburetor until the needle valve turns easily.. Turn the needle valve (with dash adjustment) until it seats lightly. Do not force it. Adjust it away from its seat one com- plete turn. This will be slightly more than necessary but will assist in easy starting.
Start the motor and open or close the throttle until the motor runs at fair speed, not too fast, and allow it to run long enough to warm up to service conditions. Now make the final adjustment. This carburetor has but one adjustment — the needle valve. Close the throttle until the motor runs at the desired idling speed. This can be controlled by ad- justing the stop screw in the throttle lever.
Adjust the needle valve toward its seat slowly until the motor begins to lose speed, thus indicating a weak or lean mixture. Now adjust the needle valve away from its seat very slowly until the motor attains its best and most positive speed. This should complete the adjustment. Close the throttle until the motor runs slowly, then open it rapidly. The motor should respond strongly. Should the acceleration seem slightly weak or sluggish, a slight adjustment of the needle valve may be advisable to correct this condition. With the adjustment completed, tighten the binder nut until the needle valve turns hard.
62. Marvel Carburetor. — The Marvel, shown in Fig. 108, is of the double nozzle type, the second nozzle coming into action at high speeds. At low speeds all the air is drawn through the venturi tube, where it takes up gasoline from the primary nozzle. At high speeds after the air has passed the choke damper, it divides, part of it going through the venturi tube around the low speed spray nozzle, and the remainder passing to one side and opening the auxiliary valve against the pressure of its spring. Near the top of the auxiliary air valve is the secondary or high speed spray nozzle.
The rush of air through the venturi tube picks up and vaporizes the gasoline from the low speed nozzle and carries it in suspension past the throttle and to the cylinders. When the suction at the auxiliary air valve has increased sufficiently to open this valve and create a high velocity at this point, gasoline is also picked up from the high speed nozzle and car- ried to the cylinders in like manner, 10
92
THE GASOLINE AUTOMOBILE
The choke damper in the air inlet is used only for starting the motor, by partially shutting off the air supply and forcing the motor to suck in a rich mixture.
To the throttle is connected a hot air damper, which when open al- lows the exhaust gas from the motor to flow through a cored passage around the throttle, where it heats the mixture of gasoline and air. A tube connects this passage with another which surrounds the venturi tube and spray nozzle, and provides heat for the incoming fuel and air.
Hot air jacket
xing chamber ^
,7~hr
ottle
throttle / . Hot air damper
Auxiliary air valve Auxiliary spray nozzle
~Neea'/e valve "A"
FIG. 108. — The Marvel carburetor.
Rules for Adjusting the Marvel Carburetor. — The following rules for adjustment are given by the manufacturers:
Start by turning the needle valve A to the right until it is completely closed, and the air adjustment B to the left until it stops. Now give the air adjusting screw B three complete turns to the right, and open the needle valve A two complete turns to the left. Start the motor as usual, using the strangler button to get a rich mixture at first. Close the throttle until the motor runs slowly and verify the needle valve adjust- ment A by turning it to the right a little at a time (% to % of a turn should be sufficient) until the motor runs smoothly and evenly. At this point the motor should be allowed to run until thoroughly warmed up.
After the motor has warmed up, turn the air valve adjusting screw B to the left, a little at a time, until the motor begins to slow down. This indicates that the air valve spring is too loose. Turn it back to the right just enough to make the motor run well.
To test the adjustment, advance the spark and open the throttle quickly. The motor should "take hold" instantly and speed up at once.
FUELS AND CARBURETTING SYSTEMS
93
If it misses or pops back in the carburetor, open needle valve A slightly by turning to the left. Do not move the air adjusting screw B any more un- less it appears absolutely necessary.
The best possible adjustment has been secured when the air adjust- ment B is turned as far as possible to the left and the needle valve A is turned as far as possible to the right, providing the motor runs smoothly and picks up quickly when the throttle is opened.
Mixture RCGULATOfl TUBE HCU» t SCREW
•* AUXILIARY GASOUNE WELL f
t GASOUNC WELL PLUG GASKET [PRMARV NOZZLE NEEDLE VALVE (COMPLETE)
FIG. 109. — Stromberg Model H carburetor.
If the motor runs too fast with throttle closed, turn the small set screw in throttle stop to the left. If the motor stops when the throttle is fully closed, turn the set screw to the right.
As the throttle opens, the hot air damper, which is connected to it by a link, gradually closes, the greatest amount of hot air passing through the jackets when the throttle is nearly closed. The position of the hot air damper at any time is indicated by the slot at the end of the damper shaft. By loosening the set screw in the damper lever, this can be set
94 THE GASOLINE AUTOMOBILE
for any desired relation between the damper and the throttle. Ordinarily the hot air damper should be nearly horizontal when the throttle is closed.
63. Stromberg Model H. — The Stromberg Model H carburetor, shown in Fig. 109, is of the double-jet type with two adjustments, for high and low speed, both working on the gasoline supply.
The gasoline in the glass float chamber is regulated by the hollow metal float. The fuel for low speed is furnished by the spray nozzle in the ven- turi tube, through which the low speed air passes. The adjustment for this nozzle is by means of the needle valve, as shown.
At high speed, the auxiliary air comes through the auxiliary air valve, which in turn automatically regulates the gasoline flow from the auxiliary gasoline valve. This supplies the extra gasoline for high speed and heavy duty service.
The dash pot with the piston riding in gasoline prevents all fluttering of the air valve on its seat when opening and closing.
This type of carburetor is fitted with a strangling or choke valve in the primary air inlet, for starting in cold weather. This assists in the vaporization of the gasoline by increasing the suction on the liquid.
The spring tension on the air valve and auxiliary needle valve is con- trolled either from the dash or from the steering post, depending upon the style of control installed. This permits adjustments to be made in order to compensate for varying conditions of weather, fuel, and operation.
64. Zenith Model L. — This carburetor, shown in Fig. 110, differs from most conventional types in the absence of auxiliary air valves. It is a "fixed" adjustment carburetor, and has as its particular feature the "compound nozzle." The compound nozzle consists of an inner nozzle, the gasoline for which is furnished direct from the float chamber. The amount of gasoline leaving this nozzle varies with the suction and conse- quently the mixture from this nozzle would be too rich at high speeds. To compensate for this rich mixture, the compensating nozzle surround- ing the main nozzle furnishes a mixture "too weak " at high speeds. This is because the gasoline feed to this jet is constructed so as to be constant at all speeds. When the engine speeds up, the amount of air increases and the compensating mixture is a weak one. This answers the purpose of the auxiliary air valve on other types of carburetors and keeps the mixture of constant proportions. By a proper selection of the two nozzles a well balanced mixture can be secured through the entire range.
In addition to the compound nozzle, the Zenith is equipped with a starting and idling well. This well terminates in a priming hole at the edge of the butterfly valve, where the suction is greatest when the valve is slightly open. The gasoline is drawn up by the suction at the priming hole and, mixed with the air rushing by the butterfly, gives a rich slow speed mixture. The slow speed mixture is regulated by the regulating
FUELS AND CARBURETTING SYSTEMS
95
screw, which admits air to the priming well. At higher speeds with the butterfly valve opened, the priming well ceases to operate and the com- pound nozzle drains the well and compensates for any engine speed.
Fia. 110.— Zenith Model L carburetor.
65. Rayfield Model G. — This carburetor is illustrated in Figs. Ill and 112. It has two jets and the gasoline is drawn through them into the mixing chamber, the quantity being controlled by adjustments on the outside of the carburetor. As will be noticed, there are no air valve ad- justments, but two gasoline adjustments, a low speed adjustment and a high speed adjustment. The names of the lettered parts on Fig. Ill are as follows:
D —Throttle Arm. G — Priming Lever. H —Gas Arm.
M — Regulating Cam. S — Drain Cock. U — Needle Valve Arm. X —Drain Cocks.
The suction created by the downward motion of the motor pistons draws air into the mixing chamber through the primary and auxiliary air inlets. This air rushes through the mixing chamber, around the nozzle
96
THE GASOLINE AUTOMOBILE
and the metering pin, and picks up the gasoline which leaves the nozzle and jet in the form of a spray. Thus the action of the mixing chamber is not unlike that of an ordinary atomizer in which the air, forced from the rubber bulb, picks up a certain amount of the liquid in the bottle and sprays it out in the form of a fine vapor.
That the proportion of air and gasoline in the mixture may be correct for all motor speeds, one fixed air inlet and two variable auxiliary air inlets are provided. The lower air valve opens and closes with the main or upper automatic air valve, giving a greater volume of air in proportion to the greater amount of gasoline to be vaporized. In other words, at high motor speeds or when the throttle is fully opened, the motor requires more gas and consequently a greater volume of air to vaporize the gasoline
HIGH SPEED ADJUSTMENT
FIG. 111.— Rayfield Model G carburetor.
which comes through the spray nozzles; at low mo tor speeds, less gas is required and consequently less air is necessary to vaporize the gasoline.
At the front end of the carburetor is the main auxiliary air valve. This is controlled by a spring and dashpot. At low speeds, when only a small amount of air is being drawn through the carburetor, the spring and dashpot hold this valve almost shut. As the speed increases and more air is needed, the suction operating against the tension of the spring draws the valve further and further open, thus giving an increased supply of air in proportion to the need for the increased speed. The motion of this valve moves the metering pin and admits an additional supply of gasoline at this second nozzle.
Rules for Adjusting Rayfield Model G.— With throttle closed, and dash control down, close the nozzle needle by turning the low speed adjustment
FUELS AND CARBURETTING SYSTEMS
97
to the left until block U slightly leaves contact with the cam M . Then turn to the right about three complete turns. Open the throttle not more than one-quarter. Prime the carburetor by pulling steadily a few seconds on the priming lever G. Start the motor and allow it to run until warmed up. Then with retarded spark, close the throttle until the motor runs slowly without stopping. Now, with the motor thoroughly warm, make the final low speed adjustment by turning the low speed screw to the left until the motor slows down and then turn to the right a notch at a time until the motor idles smoothly.
To make the high speed adjustment, advance the spark about one- quarter. Open the throttle rather quickly. Should the motor back-fire, it indicates a lean mixture. Correct this by turning the high speed ad- justing screw to the right about one notch at a time, until the throttle can be opened quickly without back-firing.
FIG. 112. — Section of Rayfield Model G carburetor.
If "loading" (choking) is experienced when running under heavy load with throttle wide open, it indicates too rich a mixture. This can be overcome by turning the high speed adjustment to the left.
66. Carter Model C. — The Carter carburetor, shown in section in Fig. 113, is of unconventional design and construction in many ways. The float is of copper and is spherical in shape. The float valve is pro- vided with a shock absorber to prevent the valve from pounding on its seat when the car is being driven over rough roads.
There are three adjustments, for low, intermediate, and high speeds. The adjustable fuel tube gives the advantages of multiple jets. For low speeds the air taken in just above the bottom of the fuel tube takes gasoline from around the bottom of the tube. Under increased suction the gasoline is sucked higher in the tube and is sprayed through a number of openings in the side of the fuel tube into the air coming through the
98 THE GASOLINE AUTOMOBILE
intermediate air valve. The high speed air adjustment is made from a lever connection on the dash.
67. General Rules for Carburetor Adjustment.— Very few general rules can be given for the adjustment of a carburetor. It is usually a very wise plan to let well enough alone, but if adjustments are necessary, it is very essential that they be made by someone familiar with the carbu-
FIG. 113.— Carter Model C carburetor.
retor, or that the manufacturers' instructions be followed out in detail. The common carburetor troubles and remedies will be taken up in Chap. IX.
On most types of carburetors, there are two adjustments to be made, a low speed adjustment and a high speed adjustment. The low speed adjustment is made with the engine running idle, the spark retarded, and the throttle about one-quarter open. This is usually the gasoline adjust- ment. The high speed, or auxiliary air adjustment, is made with the en- gine running with throttle open and spark advanced. In all cases the adjustment should be made after the engine has warmed up to its normal running temperature.
Judging the mixture is largely a matter of experience. A rich mixture is indicated by the overheating of the cylinders, waste of fuel, choking of the engine and mis-firing at low speeds, and by a heavy black exhaust smoke with a very disagreeable odor. A weak mixture manifests itself by back-firing through the carburetor and by loss of power. A proper mixture will give little or no smoke at the exhaust. Blue smoke is caused by the burning of excess lubricating oil and has no relation to the quality of the mixture.
FUELS AND CARBVRETTING SYSTEMS
99
68. Carburetor Control Methods.— The carburetor is controlled from the driver's seat. The hand throttle on the steering post regulates the amount of mixture to the cylinders, thus regulating the engine and car speed. In conjunction with the throttle connection, is the ac- celerator on the toe-board, which permits the throttle to be opened by the foot, independently of the hand lever. The accelerator must be held open by the pressure of the foot. As soon as pressure is removed from it, the throttle closes to the point set by the hand lever. The air and gasoline adjustments are usually made from the dash of the car.
69. The Gravity Feed System.— There are numerous systems for feeding the gasoline to the carburetor from the gasoline tank, which may be placed at tho rear of the frame, in the cowl, or under the seat. These feed systems are classified as gravity, pressure, and vacuum systems.
FIG. 114. — Studebaker gravity feed system.
In the gravity system of gasoline feed, the fuel flows to the carburetor by gravity alone. The tank may be placed either under the seat or in the cowl. If under the seat, there is the disadvantage of having to remove the cushions before being able to fill the tank. There is also the possi- bility in some cases that the tank will become lower than the carburetor when going up hill, and consequently the gasoline will not flow. Both of these disadvantages are done away with by placing the tank in the cowl. In either case, however, the pressure on the carburetor float valve varies as the level in the tank varies. When filling the tank, any gaso- line which spills or leaks either falls around the seat, in the car, or on the engine. The advantage of the gravity system is that it is simple and always ready. Figure 114 shows the gravity system used on the Stude-
100 THE GASOLINE AUTOMOBILE
baker car, with the tank in the cowl. This shows the float operating the gasoline indicator.
70. The Pressure Feed System.— When the gasoline tank is placed at the rear of the frame, it is obviously impossible to use the gravity system. By putting a pressure in the gasoline tank, the gasoline may be forced by pressure to the carburetor. The pressure is maintained by a small air pump operated by the engine, or by a hand pump, or both. After filling the tank, a hand pump is used to get up pressure until the engine has been started. A safety valve in the pressure system keeps the pressure from getting too high. A particular advantage of this type of feed
W..-SJ,,
Shut.0« G»olta.
tor Check'
FIG. 115. — Pressure feed system.
system is that gasoline feeds to the carburetor regardless of the position of the car. As in the gravity system, the pressure on the float valve is liable to vary. The filler cap is placed away from the engine and pas- sengers, and gasoline may be put in without disturbance. A typical pressure feed system is illustrated in Fig. 115.
71. The Vacuum Feed System. — Several systems have been developed in which the gasoline is transferred from the main tank at the rear of the car by vacuum, or suction, to a small auxiliary tank near the engine. From this small tank it flows by gravity to the carburetor. Figures 116 and 117 show the installation of the Stewart vacuum system in a car, and Fig. 118 indicates the construction of the auxiliary vacuum tank.
This system comprises a small round tank, mounted on the engine side of dash. This tank is divided into two chambers, upper and lower. The upper chamber is connected to the intake manifold, while another pipe connects it with the main gasoline tank. The lower chamber is connected with the carburetor.
FUELS AND CARBURETTING SYSTEMS
101
The intake strokes of the motor create a vacuum in the upper cham- ber of the tank, and this vacuum draws gasoline from the supply tank. As the gasoline flows into this upper chamber, it raises a float valve. When this float valve reaches a certain height, it automatically shuts off the vacuum valve and opens an atmospheric valve, which lets the gasoline flow down into the lower chamber. The float in the upper
FIG. 116. — The Stewart vacuum feed system.
chamber drops as the gasoline flows out, and when it reaches a certain point it in turn reopens the vacuum valve, and the process of refilling the upper chamber begins again. The same processes are repeated continuously and automatically. The lower chamber is always open to the atmosphere, so that the gasoline always flows to the carburetor as required and with an even pressure.
FIG. 117. — Under the hood. — The Stewart vacuum feed system.
The amount of gasoline always remaining in the tank gets some heat from the motor and thereby aids carburetion; it also makes starting easier, by reason of supplying warm gasoline to the carburetor. The lower chamber of the tank is constructed as a filter, and prevents any water or sediment that may be in the gasoline from passing into the carburetor. A petcock, in the bottom of the tank, permits drawing off
102
THE GASOLINE AUTOMOBILE
this sediment and also allows the drawing of gasoline, if required for
priming or cleaning purposes.
72. Intake Manifolds.— The tendency in present engine design is
to make the intake manifold of such shape and proportions that the path from the carburetor to the engine cylin- ders shall be as short and smooth as possible. Being close to the cylinders, the manifold as well as the carburetor is heated, greatly aiding the vaporization of the gasoline. The short manifold gives the gas very little chance to condense between the carburetor and the cylinders. It is also desirable to have the distance from the carburetor to the different cylinders the same in all cases. This insures the same amount of mixture to each cylinder. 73. Care of Gasoline. — Gasoline, being a volatile liquid, is very dangerous if not properly handled, but if proper care and at- tention are given to it there should be no danger whatever. It should never be ex- posed in a closed room, as it will evaporate, mix with the air, and form a very explosive mixture. Open lights should always be kept away from gasoline in all cases. When it is necessary to handle gasoline at night, it should be done with an electric light. Do not under any conditions use an open light.
In putting out a gasoline fire, water will only spread the fire, as the gasoline, being FIG. 118. — Stewart vacuum lighter than water, floats on it. The only successful method of extinguishing a gasoline
fire is to smother it, either by sand, or a blanket, or by the gases from a
fire extinguisher.
The exhaust gases from a gasoline engine are very deadly. Do not
breathe them for any length of time. If it becomes necessary to run
your engine in a small garage with the doors closed, arrangement should
be made to pipe the exhaust to the outside air.
CHAPTER V LUBRICATION AND COOLING
74. Friction and Lubricants. — The purpose of lubrication is to reduce friction between moving surfaces. If parts moving on each other were not separated by a film of lubricant, the surfaces would rapidly rub away. Friction is a force that tends to retard the motion of one surface over another. The frictional force depends on the nature of the surface, and also on the kind of material. It is caused by the small projecting particles which extend from the surface. The rougher the surface and the softer the material, the greater the friction; or, the harder the material and the smoother the surface, the less the friction. The more friction there is, the greater the loss of power, as it requires power to overcome friction. A great amount of friction is necessary in certain parts of the car in order that they be efficient, such as in the brakes, the clutch, and the outer surface of the tires. On the other hand, it is essential that all friction possible be eliminated from the bearings in order to have as little of the motive power lost as possible.
The principal lubricants used are fluid oils, semi-solids, and sometimes solids, such as graphite. There are three general sources of lubricants: animal oils, such as lard, fish oil, etc.; vegetable oil, such as olive oil, linseed oil, etc.; and mineral oils, which are secured from petroleum. These lubricating mediums should each be used where they are best adapted. An oil that is suitable for one part of the mechanism may not be suited for another part. Only mineral oils should be used in gasoline engine cylinders, as they alone meet the requirements. For this reason the oils used for steam engine cylinders are not good for gasoline engine use, as they do not withstand the high temperature which rises in the gas engine cylinder. There are two main requirements for good cylinder oil. It should have a high flash point, that is, it should not break down and give off inflammable gases at low temperatures; and, second, it should retain its body and not become so thin as to be worthless as a lubricant at high temperatures. It should have sufficient body to maintain a positive film between piston and cylinder, yet should not be so heavy as to retard the free motion of the piston and rings. It should also be free from acids or any form of vegetable or animal matter. The vegetable or animal matter will decompose at high temperatures and gum up the cylinder. The acid will etch the smooth surface of the
103
104 THE GASOLINE AUTOMOBILE
cylinder and cause excess friction. A simple method to test for acid is to dissolve a little of the oil in warm alcohol and then dip a piece of blue litmus paper in the solution. If there is any acid present, the paper will turn red. The litmus paper can be obtained at any drug store.
76. Cylinder Oils. — Cylinder oils are usually classified in three grades; light, medium, and heavy. Light cylinder oil looks something like the ordinary machine oil, and is slightly more viscous. The medium is somewhat heavier than the light, and might be compared to warm maple syrup. Light and medium oils should be used only on engines which have close-fitting pistons. The heavy oil is used in air-cooled engines and in engines that have loose pistons or that become too hot to use the lighter grade of oil. A good gas engine oil should have a high degree of viscosity at 100°F., a flash point not under 400°, and a fire test of over 500°.
76. Viscosity. — Viscosity is the property of a liquid by which it has a tendency to resist flowing. Oils are tested for viscosity by being put in a container and allowed to flow through a small opening. The oil that flows the fastest has the least viscosity. In some parts of the automobile it is necessary to use oil with less viscosity than in other parts. Tight fitting bearings should use oil with very little viscosity, while meshed gears should have semi-solid lubricants because the pressure on the rubbing surfaces is very high.
77. Flash Point.^-The flash point is the temperature at which, if an oil be heated and a flame held over the surface, the- vapor rising from the oil will burst into flame, but will not continue to burn. A thermometer is placed in the oil bath and the temperature taken at this point.
78. Fire Test and Cold Test. — Fire test is merely a continuation of the flash point test; that is, the temperature at which the vapor which rises from the oil will continue burning, and not merely flash for a second. Both these tests are used only on cylinder oil.
There is another test that is called the "cold test," which indicates the temperature at which the oil hardens, or becomes so stiff as not to flow. Good cylinder oil should not become so stiff as to prevent reaching the desired points at zero temperature.
79. General Notes on Lubrication. — There is no one thing which is the primary cause of more trouble and the cause of more expense in maintenance to the mechanism of an automobile than insufficient lubrication.
All moving parts of a car are usually manufactured with a high degree of accuracy and the parts are carefully assembled. In order to maintain the running qualities of the car it becomes necessary to introduce sys- tematically suitable lubricants between all surfaces which move in con- tact with one another.
LUBRICATION AND COOLING 105
The special object of this chapter is to point out the places in the car which require oiling. While it is manifestly impossible to give exact instructions in every instance as to just how frequently each individual point should be oiled or exactly how much lubricant should be applied, we can give this approximately, based on average use.
It should be borne in mind that friction is created wherever one part moves upon or in contact with another. Friction means wear, and the wear will be of the metal itself unless there is oil, and oil is much cheaper than metal. The use of too much oil is better than too little, but just enough is best.
Proper lubrication not only largely prevents the wearing of the parts, but it makes the car run more easily, consequently with less expense for fuel and makes its operation easier in every way.
The oiling charts shown in this chapter indicate the more important points which require attention. But do not stop at these. Notice the numerous little places where there are moving parts, such as the yokes on the ends of various connecting rods, and pull rods, etc. A few drops of oil on these occasionally will make them work more smoothly.
Oil holes sometimes become stopped up with dirt or grease. When they do, clean them out and be careful not to overlook them. Also be careful not to allow dirt or grit to get into any bearings.
Judicious lubrication is one of the greatest essentials to the satisfac- tory running and the long life of the motor car. Therefore lubricate, and lubricate judiciously.'
The auto engine should be lubricated by some means that will insure a definite supply of lubricant to the moving parts and that will supply the loss caused from vaporizing, burning and leakage.
The differential, axle bearings and shift gears are lubricated with semi- solid grease. The rear axle is not oil-tight, and therefore a fluid oil should not be used. Semi-solid lubricants also help to cut down the noise and wear where the pressure is heavy, and have sufficient cushion so that they adhere to the gear teeth. The lighter oils are better adapted for the high speed close-fitting parts. Other moving parts may be lubricated with the ordinary oil can, but are generally lubricated by the compression cup system. These cups may be screwed up from time to time to add more lubricant to the bearing surfaces.
The transmission should always contain sufficient lubrication to bring it up to the level of the drain plug on the side of the case, or so that the under teeth of the smallest gear will enter to their full depth.
The differential case should contain enough lubricant to bring it up to the filling hole, or should be about one-third full.
Wheel bearings should be packed with a thin cup grease. Do not use a heavy grease because it will work away from the path of the roller
106 THE GASOLINE AUTOMOBILE
or ball and will not return. In each hub there is usually a small oil hole. Inject some engine oil here whenever you are oiling the car. It will keep the grease soft and in good condition. Before lubricating any part, wipe all dirt from it so that the dirt will not get into the bearings.
The steering gear is perhaps one of the most important parts of the car to keep properly lubricated. Failure of the steering apparatus is a dangerous thing and a few drops of oil given to the oil cups and the various steering connections constitute a cheap and safe means of avoid- ing accidents. Most types of steering apparatus are packed with grease which, having no outlet, will remain. However, the grease will become dry and a little oil should be added from time to time.
Few motorists think of lubricating their brake connections. Mud and water will find their way into the brake mechanism and a squeeze of the oil can and a turn of the grease cups, given daily will keep them in good working condition.
The principal engine lubricating systems can be grouped under the following heads: first, splash system; second, splash with circulating pump, which maybe either a "forced feed" or a "pump-over" system; third, full forced feed; fourth, mixing the oil with the gasoline.
80. Splash System of Engine Lubrication. — The splash system is used in the Ford engine, as shown in Fig. 119. The oil is poured directly into the crank case until it comes above the lower oil cock. The level of the oil should be maintained somewhere between the two oil cocks. The flywheel runs in the oil and picks up some of it and throws it off by cen- trifugal force; some of the oil is caught in a tube and carried to the front end of the crank case where it lubricates the timing gears. As the oil flows back to the rear part of the crank case, it fills the small wells in the crank case under each connecting rod. As the connecting rod comes around, a small spoon or dipper on the bottom scoops up the oil, so that there is a regular shower of oil all the time. The pistons, cylinder walls, and bearings are lubricated in this manner and the oil is kept in continuous circulation. All parts of the clutch and transmission are lubricated in the same manner as the engine.
The oil level should never get below the lower oil cock and should never get above the upper oil cock. Never test the level of the oil when the engine is running.
81. Splash System with Circulating Pump. — This system has an oil reservoir or sump below the main crank case bottom. The oil from the sump in the lower half of the crank case is sucked through a strainer into the pump, usually at the rear end of the reservoir. The oil pump of the Buick engine is shown in Fig. 120. This pumps the oil up through a pipe to a sight feed on the dash so that the circulation can be observed by the driver. From here the oil returns to the splash trays in the lower
LUBRICATION AND COOLING
108
THE GASOLINE AUTOMOBILE
half of the crank-case through the distributor pipe. As the crank comes around, the spoons or dippers on the connecting rods dip into these trays and force some of the oil up into the crank pin bearings and splash the remainder over the interior of the crank case and up into the cylinders and pistons. As the oil drains back, it is caught in ducts and led to all the bearings of the motor, the excess running back into the sump to be used again.
The oil circulating pump consists of two small gears enclosed in a close fitting housing attached to the lower half of the crank case and
driven by a vertical shaft and spiral gears from the cam shaft. As the gears turn, they take the oil into the spaces between the teeth and carry it around to the outlet where the action of the teeth meshing together squeezes the oil out of the spaces and forces it to flow to the sight feed on the dash. The pump requires no attention or adjustment ex- cept the addition of fresh oil to the crank case reservoir as often as is necessary to keep the oil level up to the oil cock. The sight feed on the dash merely shows whether or not the oil is circulating and does not show when the supply in the crank case is running low. Test the oil level at frequent intervals by opening the oil cock and see that the oil is kept up to this level. To remove the pump, draw off all the oil and take the pump out from below.
The motor lubrication on the Overland car is shown in Fig. 121, ' and is the splash and pump-over system. The oil reservoir is located m the bottom of the crank case and is filled through the combination breather pipe and oil filler on the right side of the engine. The glass gauge on the side of the crank case close to the breather pipe indicates the oil level. The oil pump, which is located in the rear of the crank case, is driven from the cam shaft. The lubricant is drawn from the base and, after passing through a strainer, runs through a sight feed on the dash, and from there it runs into the troughs and is splashed into the bearing surfaces. It is very important that the oil strainer be kept clean at all ;imes so that proper circulation of the 'oil is insured. For this reason B removal of the oil strainer has been made easy. By unscrewing the large plug on the side of the crank case right opposite the oil pump, the
FIG. 120, — Buick oil pump.
LUBRICATION AND COOLING
109
cylindrical screen may be drawn out 'and cleaned by dipping into a pail of gasoline. The^ owner should see that the oil screen is cleaned every 200 miles of the first 1000 miles and after that every 500 miles.
The lubricant circulates freely through the system as long as the small wheel in the dash sight-feed revolves. But as soon as the wheel stops or the sight-feed glass shows clear, this is an indication that the oil supply is exhausted, or that there is an obstruction in the circulation of the oil which should be located and remedied immediately, since serious and expensive trouble will result from running the motor with an in- sufficient supply of oil.
FIG. 121. — Overland splash system with circulating pump.
The wrist pin is lubricated from the cylinder walls, through the opening in the piston through which the wrist pin is inserted, as well as through a slot cut into the connecting rod over the wrist pin bushing.
The lubrication system of the Studebaker Four, Fig. 122, is called the constant level splash system combined with a forced feed to. the timing gears. A quantity of oil is carried in a reservoir F, which is formed by the crank case of the motor. A pump B of the plunger type draws the oil from this reservoir and sprays it (G) over the connecting rod bearings. It also pumps surplus oil through a sight feed J or indi- cator on the dash, from which it flows over the timing gears D at the
110
THE GASOLINE AUTOMOBILE
front of the motor and returns to the reservoir through the pipe U. The oil draining from the spray collects in troughs E which maintain a constant level of oil just under the connecting rods. At each revolu- tion short projections M from the connecting rods dip into these troughs and splash oil over the lower ends of the pistons, and over the cam and crank shaft bearings.
To fill the oil reservoir of the motor, pour the oil in through a funnel shaped tube H, which you find on the left side of the motor. This funnel shaped tube is called the "breather pipe." At the side of the "breather pipe" there is a gauge / which shows the amount of oil in the
FIG. 122. — Studebaker splash system with forced feed.
reservoir. The' oil is poured into the breather pipe until the gauge indicator rises to the highest point of the gauge, being careful that there is no more oil poured into the motor than just enough to bring the in- dicator to the highest point shown on the gauge. The only attention necessary to keep the motor perfectly lubricated is to see that the gauge indicator shows that there is oil in the reservoir.
When the motor is running, oil drops through a glass indicator or "sight feed" J on the dash. This "sight feed" can be seen from the seat. and should not be forgotten by the driver. If the oil should cease to flow through the "sight feed" when the motor is running, the motor should be stopped and hood lifted to ascertain if the gauge I shows oil in the reservoir. If it does show oil in the reservoir, then either the oil pump or the connecting oil pipes are clogged and should be cleaned out.
LUBRICATION AND COOLING
111
82. Full Forced Feed System. — A full forced feed as used on the Cadillac Eight is shown in Fig. 123. A gear pump located at the for- ward end of the motor and driven from the crank shaft takes the oil up from the oil pan in the lower part of the crank case and forces it through a reservoir pipe running along the inside of the crank case, from which pipe there are leads to each of the main bearings. The crank shaft and webs are drilled and oil is forced from these main bearings to the con- necting rod bearings through the drilled holes. The forward and rear bearings supply the rod bearings nearest them, while the center bearing
PBESSURE GAUGE ON DASH' ADJUSTABLE PEESSUI2E VALVI
FIG. 123. — Cadillac forced feed oiling system.
takes care of the rod bearings on either side of it. The oil is then forced from the main reservoir pipe up to the relief valve, which maintains a uniform pressure above certain speeds, and overflows from this valve to a pipe extending parallel with the cam shaft and above it. Leads from this latter pipe carry lubricant by gravity to the cam shaft bearings and front end chains. Pistons, cylinders and piston pins get their oiling by the oil thrown from the lower ends of the connecting rods.
A gauge indicating the level of the oil is attached to the upper cover of the crank case. Whenever the indicator reaches the space marked "fill," oil should be added until the indicator returns to "full." A filling hole is provided in each block between the second and third cylinders. If the hand on the pressure gauge on the cowl vibrates or returns to zero on the dial when the engine is running, it indicates that the oil level is very
H2 THE GASOLINE AUTOMOBILE
low. Should this occur through neglect to add oil at the proper time, the
engine should immediately be stopped and sufficient oil added to bring
the pointer up to the top of the gauge before the engine is again started.
The hollow crank shaft oiling system as used by the Wisconsin Motor
Mfg. Co. is shown in Fig. 124 and operates as follows:
The oil is carried in an inde- pendent chamber at the bottom of the crank case, and the con- necting rods are not allowed to dip into this, thus preventing the oil from being whipped to a froth, and preserving its viscosity.
It is pumped by means of a gear pump located at the lowest point of the oil reservoir into a main duct, which is cast integral with the crank case, and from here distributed by means of ducts, drilled into the webs, to the main bearings. From here it is forced through a hollow crank shaft to the connecting rod bearings, and a sufficient amount of oil is forced out of the ends of the bearings to lubricate the pistons, piston pins, and cam shafts. A separate lead runs directly over the timing gears, and all oil is thoroughly filtered before it is pumped over again. An oil gauge indicates by means of a ball and float the exact amount of oil contained in the reservoir, and distinct marks on the glass gauge show the high and low mark, and if the oil is maintained be- tween these two levels no burnt oil smoke will be emitted, and the spark plugs will not be fouled.
The pressure of the oil increases with the speed of the motor, so the faster the motor is run the more oil is forced to it, and vice versa. The location of the oil reservoir permits the proper cooling of the oil, thus minimizing the danger of burning out bearings.
LUBRICATION AND COOLING 113
The lubricating system for Knight sliding sleeve motors is also of the forced feed type. The following description is of the system used on the Moline-Knight car. Oil is drawn from the sump by a gear pump driven off the end of the eccentric shaft, and is delivered to the three main bear- ings, and the magneto drive shaft bearing under a pressure determined by the settings of a spring controlled by-pass valve, through which the excess oil is delivered. This excess oil is led to the chain driving the eccentric shaft and magneto, and flows thence to a trough and through a screen to the sump. Part of the oil delivered to the main bearings passes through holes in the crank shaft web to the crank pins, and thence through the tubular connecting rod to the hollow piston pins. From the two ends of the latter it flows to the sleeves and is distributed through holes and oil grooves in the latter over their circumference and the cylinder walls. All parts requiring lubrication not mentioned above are oiled by splash from the crank shaft and connecting rods. The flow of oil delivered under pressure is determined by a valve which is so connected as to open and close with the throttle. There are no oil grooves in any of the crank shaft bearings. The entire bottom of the crank case is covered by a screen, through which the oil returns to the sump.
83. Mixing the Oil with the Gasoline. — Another system that is used to some extent in two-stroke marine engines is to mix the lubricating oil with the gasoline, in the proportion of 1 pt. of oil to 5 gal. of gasoline. The easiest way is to thoroughly mix 1 pt. of oil with 1 gal. of gasoline, pour it into the fuel tank and then add 4 gal. of gasoline. The oil stays in solution with the gasoline. This system is very simple, as the lubri- cating becomes automatic and there are no regulators to adjust.
When the piston is on the up stroke, a charge of gasoline and oil is drawn through the carburetor. Here the oil and gasoline separate because the oil does not evaporate and the gasoline does. The gasoline mixes with the air in the form of a gas. The oil collects in the form of small globules which float in the mixture of gas and air and are carried into the crank case by the suction of the motor. Here some of the oil settles on the connecting rod and crank and flows through a special oil duct to the crank pin.
On the down stroke of the piston, the gas and oil are forced through the by-pass into the cylinder where the remainder of the oil is deposited on the cylinder walls. This operation' is repeated every revolution of the engine, a new film of oil being supplied each time.
84. Selection of a Lubricant. — The proper lubrication of the motor car is more important than any other item in its care. Only the best high grade oils should be used to lubricate the engine. Some engines require lighter oils than others on account of the close-fitting pistons and rings. It is better to follow the instructions sent out by the manufac-
114 THE GASOLINE AUTOMOBILE
turers in regard to the kind of oil to use rather than for the motorist to make his choice or to be directed by an oil salesman. The different com- panies run extensive tests and find out in that way which oil is best suited for their type of engine. The only way to get the best lubricants is to pay the price. Money saved by cheap oils or grease may be more than lost in worn-out bearings or cylinders.
The multiple-disc type of clutch is the only one in which any lubrica- tion should be used, and the oil here should be drained off about every 1000 miles, the clutch well cleaned out with kerosene, and then filled with light machine oil, the amount, of course, depending upon the capacity of the case. All clutches that use any kind of facing, such as asbestos, raybestos, or leather, should never be lubricated, as the oil decreases the friction and causes slipping. Clutch leathers will retain their life and softness better if given an occasional treatment of neatsfoot oil and then wiped dry.
The planetary transmission system in the Ford automobile is encased so as to revolve in an oil bath.
The differential housing and sliding gear transmissions and all other parts that use either heavy cylinder oil, transmission oil, or graphite grease, should be thoroughly cleaned every 1000 miles, or thereabouts, and well flushed out with kerosene in order to remove all sediment and metallic dust that may be in the old grease. All wheel bearings are of the ball or roller anti-friction type, and are packed with semi-fluid grease which should be renewed about every 1000 miles.
An excess of grease in the transmission or differential case will be shown by leaking at the joints, on account of the difficulty of keeping these members absolutely tight and still free to run. If there is too much grease in the differential case, it will run along the axle shaft and out over the oil guard, which is to prevent it from getting on the tire and also from interfering with the action of the internal brake.
Excess of lubrication in the engine will produce carbon deposits and dirty spark plugs. It may also cause the piston rings to gum up and stick. It can be detected by the color of the exhaust smoke, which will have a bluish tinge, or it may be detected by a sticky black coating on the spark plug.
A small amount of graphite and oil or grease should be supplied be- tween the leaves of the springs. This can generally be done by jacking up the frame so that all weight is taken off the wheels, and by using a small clamping device with wedge-shaped jaws, which can be used to spread the leaves apart.
85. Directions for Lubrication.— A very good chart for lubrication purposes is sent out by the Chalmers Motor Car Co., and of course can be used for other standard makes of cars. This chart is as follows:
LUBRICATION AND COOLING
115
DIRECTIONS FOR LUBRICATION
EVEBT DAY CAB is IN USE, OB EVEBY 100 MILES:
Part
Crank case.
Steering knuckle grease cups. Steering cross rod grease cups. All spring bolt grease cups. Speedometer driving gears. Eccentric bushing of steering gear. Wheel hub oilers.
Quantity
Keep oil at level of top try cock. One complete turn. One complete turn. Two complete turns. One complete turn. 10 or 15 drops. 10 drops.
TWICE A WEEK, OB ABOUT EVEBY 200 MILES:
Part Quantity
Fan hub bearing. Few drops.
Pump shaft grease cups. Two complete turns.
Steering gear case oiler. Fill.
Steering gear case grease cup. Two complete turns.
Steering wheel oil hole. 8 or 10 drops.
Steering column. 10 or 15 drops.
EVEBY WEEK, OB ABOUT EVEBY 300 MILES:
Part
Spark and throttle shafts.
Control bracket bearings.
Transmission case.
Pedal fulcrum pin.
Brake pull rods and connections.
Brake cross rod grease cups.
Torque rod grease cups, front and rear.
Brake shafts on rear wheels.
Rear spring perch grease cups.
Quantity Few drops. Thoroughly.
Enough to cover lower shaft. Thoroughly. Thoroughly. Two complete turns. Two complete turns. Thoroughly. Two complete turns.
TWICE A MONTH, OB EVERY 500 MILES:
Part Quantity
Magneto bearings (3 oil holes). 3 or 4 drops each.
Dynamo drive shaft universal joints. Fill one-half full. EVEBY MONTH, OB EVERY 1000 MILES:
Lubricant Motor oil. Cup grease. Cup grease. Cup grease. Cup grease. Motor oil. Motor oil.
Lubricant Motor oil. Cup grease. Motor oil. Cup grease. Motor oil. Motor oil.
Lubricant Motor oil. Motor oil. Motor oil. Motor oil. Motor oil. Cup grease. Cup grease. Motor oil. Cup grease.
Lubricant
High grade light ma- chine oil. Cup grease.
Part Crank case.
Reach rod boots.
Spring leaves. (Jack up frame and
pry leaves apart.) Hub caps. Universal joints.
Gasoline pressure hand pump.
Quantity Drain off dirty oil; clean oil screen at
left of motor thoroughly; fill to
level of top try cock. Pack thoroughly. Thoroughly.
Pack thoroughly.
Remove grease hole plug and fill one- half full. 4 or 5 drops on leather plunger.
Lubricant Motor oil.
Cur
Graphite grease.
Cup grease. Cup grease.
Light machine oil.
EVEBY 2000 MILES:
Part
Differential housing. Transmission case.
Quantity
3pt.
Drain thoroughly, flush with kero- sene, refill to cover top lower shaft try cock.
Lubricant
Special axle compound. Motor oil.1
Dynamo should be lubricated every 3000 to 5000 miles.
When changing tires, put a few drops of oil on inside sliding ring of demountable rims to insure easy detaching.
116
THE GASOLINE AUTOMOBILE
QREAiftg
LUBRICATION AND COOLING 117
Figure 125 shows the location of the various places to be lubricated and the proper intervals for lubrication. This is the chart for the Case car.
86. Cylinder Cooling. — When an explosion occurs inside the cylinder of a gas engine, the gases on the inside reach a temperature of from 2000° to 3000°F. The walls of the cylinder are, of course, exposed to this high heat and would very quickly get red hot if we did not have some way of keeping them cool. The polished surface upon which the piston slides would be very quickly spoiled. The most common way of keeping a cylinder cool is by the use of water. Surrounding the cylinder is a metal jacket enclosing a space for the cooling water. By keeping a supply of water passing through this space, the cylinder can be kept cool enough for the operation of the engine. The cylinder head is also cast with a double wall, especially around the valves, so that these parts will also be kept cool. The cooling fluid used is generally water.
Water should not be allowed to remain in the jacket of an engine over night if there is danger of a frost, as the freezing of the water will crack the cylinder. When the supply of water is limited, as in an automobile, the water is cooled in a radiator or system of pipes, and then is used over again. The water is kept in circulation by a pump, or by the thermo- syphon system, and the hot water is cooled by the air passing over the radiator.
The circulation in the thermo-syphon system is based on the fact that cold water is heavier than hot water, and consequently, the water heated in the cylinder jackets flows up and over into the top part of the radiator, where it is cooled and then flows from the lower portion of the radiator back to the engine cylinder. Circulation is automatically maintained as long as the engine is hot and there is enough water in the radiator so that the return connection from the cylinder to the radiator contains water. This means that the radiator must be kept practically full all the time, or else there will be no circulation and the water will merely boil away.
When the pump system of circulation is used, the radiator may be lighter than in the syphon system, as less water is needed to do the same amount of cooling. The pump is driven from the engine, and the faster the motor runs the faster the water circulates. The centrifugal type of pump is generally used for circulating cooling water.
87. Water Cooling Systems. — Radiators differ in design. In some types the water flows through tubes of very small diameter. In this type it is necessary to have a circulating pump of some kind. In radia- tors having tubes of larger diameter, the thermo-syphon system may be used. The radiators using the small pipes have a greater capacity for their size because they have more exposed area for cooling in comparison with the amount of water they carry. The small tubes have the dis-
118 THE GASOLINE AUTOMOBILE
advantage of increased resistance. This is why it is necessary to use a
pump.
The air for cooling purposes is usually drawn through the radiator by a fan placed directly back of it. This fan may be driven with a bevel or spur gear, with a silent chain, or with a wire or leather belt. In some cases, however, the engines are air-cooled, the cylinders being cast with a large 'number of fins or rings on the outer surfaces to increase the cooling effect of the air. In this case there is no water jacket.
The cooling system of the Overland is the thermo-syphon system, which eliminates the circulation pump and its gears, glands, stuffing boxes,
FIG. 126. — Overland thermo-syphon cooling system.
etc. The thermo-syphon system is automatic, as the speed with which the cooling water circulates is increased or decreased with every increase or decrease in jacket temperature. The action of the system is, briefly, as follows: The water enters the cylinder jackets A, Fig. 126. Upon becoming heated by the explosions within the cylinders, the water ex- pands and, being lighter, rises to the top. It then enters the pipe B and passes into the radiator at C, where it is brought into contact with a large cooling surface, D, in the shape of the cellular radiator. On being cooled, and thereby contracting and becoming heavier, the water sinks again to the bottom of the cooling system, to enter the cylinders once more and to repeat its circulation. The cooling action is further increased by a belt- driven fan which draws air through the radiator spaces.
LUBRICATION AND COOLING
119
Figure 127 shows the cooling system on the Ford. This is also a thermo-syphon system, the principle of operation being the same as on the Overland. The arrows indicate the path of the cooling water.
The cooling system used on the Studebaker Four is the pump system shown in Fig. 128. The water system, which contains 10 qt. of water, consists of a radiator, hose connections, water line, pump, and water jackets which are incorporated with the cylinders. The radiator D being filled with water and the motor running, the centrifugal pump C forces the water to circulate as follows: From the pump it is driven
FIG. 127. — Ford cooling system.
through the lower water line into the cylinder water jacket, directly at the valve seats, where perfect cooling is most needed. Here it absorbs the heat and goes on to the upper water line and thence to the radiator. In the radiator D the water percolates slowly down through many fine tubes F and is cooled by the air rushing between the fins surrounding the tubes and thence returns to the pump. A fan G on the front of the motor, belted to the crank shaft, draws the air through the radiator and facilitates the cooling operation. Figure 128 also shows a standard design of tubular radiator. The pump, which is of the centrifugal type, requires no attention other than to see that it does not become choked by using dirty water. There is a packing nut on the shaft which should be repacked if the pump should ever leak around the shaft entrance.
12o THE GASOLINE AUTOMOBILE
This can very easily be done by turning off the packing nut, removing the old packing and rewinding the shaft with a few inches of well graphited packing and tightening up the packing nut. The packing should be wound on in the same direction as the nut is turned to tighten it.
The cooling system on the Cadillac Eight is of the forced circulation type. The radiator is of the tubular and plate type, with rotating fan mounted on the forward end of the generator driving shaft, the latter
DRAIN COCK. A-
FIG. 128. — Studebaker cooling system.
being driven by silent chain from the cam shaft. Each set of cylinders is cooled separately. Due to the angle of jackets, the water does not lodge in the pockets. The natural tendency is for the water to flow upward and to rise to the hottest points.
There are two centrifugal water pumps, one on each side of the forward end of the engine. These are driven by a transverse shaft which is driven by spiral gears from the crank shaft. Within each pump hous- ing is a thermostat shown in Fig. 129, which controls a valve that is between the radiator and the pump.
When the temperature of the cooling water drops below a pre- determined temperature, the thermostats contract,