MOTOR VEHICLE 330 MOTOR VEHICLE plosion is absorbed by an expansion chamber or muffler. The motor is usually cooled by circu- lating water around the outside of the cylinders which are jacketed for this purpose. The water is passed from the cylinder to a radiator where it is cooled by air, then to a reservoir and back through the system. The water is kept in circulation either by a rotary pump or by a thermo syphon system. A motor- driven fan is mounted at the rear of the radiator for the purpose of drawing air through the radiator. In many high- grade cars a thermostatic device either cuts off the circulation of the water through the radiator or operates a shut- ter which prevents the passing of air through the radiator until the motor is heated to its point of highest thermal efficiency. Air-cooling, which would do away with many parts and much weight as well as do away with the possibility of freezing, has not been successfully introduced except by one manufacturer. SEDAN The lubrication system of the motor is either the mechanical or the splash system. Ignition may be by battery, low or high tension magneto, or by one of the generator-charged battery systems which are very popular at the present day. The difficulty in cranking or starting the gasoline soon led to efforts to overcome this drawback. Heavy springs which were wound by the motor when in opera- tion, various priming devices, some op- erating with acetylene gas and likely to be dangerous in unexperienced hands, and compressed air systems were used with indifferent success. The introduc- tion of the motor-generator system, which operated as a motor and draws power from a storage battery when the motor is to be started, and then operates as a generator and charges the storage battery, is one of the great advances of modern motor-vehicle engineering, and seems to have satisfactorily solved the problems of starting, lighting, and igni- tion. For the car of not extremely high price, the idea in designing the modern motor-vehicle engine is to produce a motor with high efficiency and powur, vdth smaller fuel consumption, and lighter weight. To this end the small bore, long stroke, high-speed motor has been perfected, and is often fitted with aluminum pistons and a counterbalanced crank shaft. The motor is engaged or disengaged from the driving system by a common COUPE mechanical device called a clutch, which is held in the engaged position by a spring, and may be disengaged by the operation of a foot pedal. The most common types of clutch are the cone and the multiple disk, either of the dry or oil type. A clutch is necessary in order that the motor may be started without the car moving, and that the gears may be shifted. With but one possible exception, the selective type of gear system is used. The application of the power generated by the motor is controlled by the use of gears of various sizes, usually ranging from one which gives the motor a great power advantage, without high speed, called low, through an intermediate step, to direct drive, or high gear, A reverse ELECTRIC COUPE gear is also provided. By disengaging the clutch and moving a hand lever any desired gear can be engaged by the opera- tor, which counteracts _ the low speed range of efficient operation of this gaso- line motor. The gears are inclosed in a housing, and should run in a heavy oil
