Fig. 8.-Touring Body Types Usually Fitted on Pleasure Car Chassis. A-Open Five-Passenger Torpedo Body. B-Limousine Body. C-Landaulet. D-Berline. 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 l'nks 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 desired, 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. Pleasure car bodies may be made of wood or metal. Sometimes the panels are of sheet 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 of square feet in the radiator, dash, wind shield, mudguards, and other parts that would offer resistance to motion, is kept as low as possible. A It takes a certain amount of power to overcome the friction existing between the wheels and the ground due to the car weight, and to produce movement of the vehicle. This is known as traction resistance and depends largely upon the nature of the road surfaces, the size of the driving wheels and the type of tire with which they are fitted. Fig. 9.-Typical Two-Passenger Roadster Body on Pleasure Car Chassis. Q. What is the resistance of grades? A. When an automobile is climbing a hill, it must lift its weight in opposition to the force of gravity, which exerts no retarding influence when the automobile is operated on the level, and which really accelerates car motion when the automobile is descending an incline. It requires an effective effort or push at the point of contact between the rear wheels and the ground equal to one per cent of the car weight for each one per cent increase in gradient. Q. How much power does an automobile need? A. The amount of power required to propel an automobile de pends upon the nature of service for which it is intended. A high speed car of comparatively light weight may require more power than a heavily loaded, slow moving truck. An automobile that is to be used in hilly country or where road conditions are not good, needs more power than a machine of the same type operated under more favorable conditions. This is a point that is hard to decide, and no general rules can be given. If an automobile has too much power, it will use an excess of fuel over the amount actually needed to propel the vehicle and will rack itself to pieces sooner than one that is lacking in power. The under-powered car, however, usually performs very well on the level and under favorable conditions, but it is very unsatisfactory when used on hills or bad roads. Much depends upon the general design of the automobile, and the efficiency of the power transmission and driving elements. Fig. 10-Coupe Body, a Closed Type Suitable for Two or Three Passengers Fitted to Roadster Chassis. Q. What is the usual proportion of power to weight? A. Pleasure cars that are intended for touring or high speed |