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reduce friction between the piston and cylinder and the other bearings.

Q. What does a lubrication system consist of?

A. A lubrication system, such as commonly used in connection with the gasoline engine, consists of a container or tank in which oil is stored, some form of pump to supply the oil to the bearing points, and piping to convey the oil from the container to the pump, and from the pump to the motor.

Q. What does the cooling system do?

A. As the power of a gasoline engine depends upon exploding gas in its cylinders, it would soon get very hot, due to the high temperature produced by the rapid burning or combustion of gas, and unless it was cooled in some manner and the surplus heat extracted from the metal of which the cylinders are composed, the high temperature existing would soon produce deformation of parts and woula put the engine out of commission.

Q. How many types of cooling systems are used?

A. Automobile power plants are cooled by two methods, che simplest of which is to direct a stream of air from a fan or blower on the cylinders, which are provided with flanges to increase the radiating surface, or by passing water thru jackets surrounding the cylinders and afterward cooling this water by passing it thru a radiator exposed to the action .of a cooling current of air. Engines are thus cooled either by air directly applied to the heated metal or indirectly utilized when it cools the water which has absorbed the surplus heat of the engine.

Q. What is the purpose of the clutch?

A. The clutch is a simple form of easily operated coupling which makes it possible to run the engine independently of the rear wheels when desired.

Q. Why is change speed gearing needed?

A. Change speed gearing is necessary to provide easily changed ratios of drive between the engine crank shaft and the rear wheels to suit varying road conditions. The gears that give reverse motion to the car are also usually included in the change speed gear set.

Q. How is power usually transmitted to the wheels?

A. The common method of transmitting power from the gear set to the wheels is by means of a shaft and universal joints to a pair of bevel gears or a set of worm gears at the rear axle or by sprockets and chain.

Q. What are the features of chain drive?

A. Power transmission by chains make it possible to obtain varying ratios of drive very easily by merely altering the sizes of the sprockets, and provides for power transmission with minimum loss if the drive is solely by chain.

Q. What are the advantages of enclosed gear drive?

A. Enclosed gearing may be kept free from dirt and grit, and as protected gears may be operated continually in a bath of lubricant, they are not only quiet in operation, but are very enduring and efficient.

Q. Why is the frame needed?

A. The frame is one of the most important parts of an automobile inasmuch as it supports the power plant and power transmission mechanism, forms a connecting link between the axles and the machinery, carries practically all of the controlling elements and power p ant auxiliaries, and serves as supporting member for the body which carries the load or passengers.

Q. How is the frame supported ?

A. The frame is supported by and attached to the axles thru the medium of resilient members called springs.

Q. How do the front and rear axles differ?

A. The front axle is simpler than the rear and is used only for steering. The wheels are mounted on steering knuckles which are attached to the ends of the axle and which may be moved to the angle necessary to allow the wheels to follow a curve when going around a corner.

The rear wheels are attached to the axles in such a way that they cannot move relative to the axle, except to turn around with them, and the general construction of the rear axle on most cars includes the differential and drive gearing.

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Fig. 8.—Touring Body Types Usually Fitted on Pleasure Car Chassis. A-Open Five-Passenger Tor

pedo Body. B-Limousine Body. C-Landaulet. D—Berline.

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Q. How is the automobile steered?

A. A hand wheel which is placed convenient to the driver actuates the front wheels thru suitable gearing and links and is used to alter the position of the wheels for steering.

Q. How is the automobile controlled?

A. An automobile is controlled as far as its direction is concerned by the steering gear; its speed may be varied either by altering the speed of the motor or by changing the ratio of the gearing by means of a gear shift lever. It is started by means of the clutch which connects the engine to the rear wheels thru the medium of the change speed gearing, and it is stopped by suitable brakes or retarding members applied to the rear wheels or some other part of the transmission system by suitable hand or foot operated lever

Q. How many types of automobile wheels are generally used?

A. The wheels of an automobile may be of the usual wood construction so widely used on horse drawn vehicles changed somewhat in detail, or they may be of the wire spoke form similar in principle to those used on bicycles. In both cases it is obvious that the construction is changed so that the required strength is obtained.

Q. How many forms of tires are used?

A. Automobile tires are usually composed largely of rubber and fabric, and may be of the pneumatic or inflated type, of the cushion form, or of solid rubber. Some very heavy commercial vehicles have used wood block tires, others have used steel or iron tires just as utilized on horse drawn vehicles.

The non-resilient forms, such as wood blocks or steel, are not suitable except on very heavy, extremely low speed trucks, because they are not easy riding enough to support the mechanism without undue vibration, which causes rapid depreciation of the parts comprising the power plant and power transmission members.

Q. What are the principal body types?

A The principal body types fitted to pleasure car chasses are shown at Fig. 8. These are the touring, limousine, landaulet and berline. A roadster body is outlined at Fig. 9, while the coupe form, which is usually employed to replace a roadster body when a closed car is desi ed, having a capacity for but two or three passengers, is shown at Fig. 10. Truck bodies vary very widely according to the nature of the work they are intended for. The simplest form is a platform without sides, then stakes may be added to this platform body or various forms of closed wire panel delivery bodies or express wagon types fitted to the chassis.

Q. What are automobile bodies made of ?

A. Peasure car bodies may be made of wood or metal. Sometimes the panels are oʻsheet steel or aluminum attached to a wooden frame, or the body may be made entirely of metal. Motor truck bodies are usually made of wood and well ironed and strengthened by braces and angle pieces of steel or iron. The floors of motor trucks are often reinforced with strips of bar steel and the corners are provided with corner pieces of metal where they are liable to come in contact with a loading platform.

Q. What are "torpedo and stream line" bodies?

A. It is now common practice to make bodies of pleasure cars designed for high speed of such form that air resistance is reduced to a minimum. This is accomplished by the use of gradual curves and unbroken sides. The name torpedo has been applied to this form of body because in the exaggerated forms they resemble a projectile of this nature on wheels.

Q. Under what conditions is air resistance noticed?

A. Air resistance is of little moment on car speeds lower than 30 miles per hour, but as this rate is exceeded, it is a very important factor which must be recognized, and the amount of exposed area of the car which will offer resistance should be reduced to as low a point as possible. The amount of power needed to overcome air res stance varies inversely as the cube of the speed. This means that if the speed of the car is doubled the power needed to overcome air resistance at half that speed is multiplied by eight. For instance, if one horsepower is absorbed at 20 miles per hour, 8 horsepower will be required to overcome the air resistance present at 40 miles per hour. It is for this reason that the torpedo body has been evolved and in most modern cars the frontal area, which means the number

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