The independent suspension of front wheels presents several safety features. Since the springing of the front wheels is not allied with the steering of the wheels, a broken front spring only results in a bumpy ride. With the conventional system, the steer ing mechanism is thrown out of order. This is due to the fact that the front springs are not used as structural members. These members are built sturdier and more rugged, promoting greater safety. The danger resulting from a front tire blowout has been lessened considerably. In the event of front tire failure while driving, less correction with the steering wheel is necessary to maintain control, than is necessary with a conventional type of front wheel suspension.
Accessories.—The air to the carburettor, fuel and lubricating oil supply of an engine must be kept free from sharp particles of dust and other foreign matter, to prevent excessive wear of the moving parts or the plugging of the oil or fuel lines. To do this gasoline filters, oil filters and air cleaners are used. Air cleaners also reduce the amount of carbon deposit in the combustion chamber, as much of this deposit is composed of road dust. Air cleaners are made in the centrifugal, inertia, screen and liquid types. To indicate the operating conditions to the driver, oil pressure gauges, ammeters, gasoline gauges and speedometers are mounted on the dash. The four main types of speedometers are air friction, air blower, centrifugal and magnetic, the latter being by far the most common. As automobiles have become more numerous, theft prevention has become a problem of increasing importance. Numerous types of locks operating on the steering gear, transmission, throttle, intake manifold, ignition coil, ignition distributor, breaker or clutch are in use. A lock may operate on two or more parts of a car to give increased protection. The mod em automobile is fitted with many accessories to make it more attractive and convenient. These may include bumpers, wind shield wipers, rear view mirrors, radiator ornaments, cigar lighters, vanity cases, ventilators, heaters, direction signals, etc.
some vehicles, it is necessary that some of these members have over 200,000 lb. per sq.in. elastic limit and 250,000 lb. per sq.in. tensile strength. Most of the parts of an automobile made of steel have, as their primary function, resistance to distortion under load and ability to transmit considerable power without failure. Grey cast or malleable iron is used for castings of intricate and com plicated shapes. Cast iron is used for cylinder blocks because of its resistance to wear and low friction. Malleable castings are used in certain places where shock is encountered, to insure against abrupt failure.
Copper is used, on account of its high electrical conductivity, in the electrical equipment, including lighting, ignition and start ing motor circuits. It is also used for gaskets, which are washers of various shapes and sizes consisting of a soft material such as asbestos sandwiched between metal sheets. Brass and bronze are used as castings or rolled sheets. These metals are used as bearing materials to reduce friction between moving parts. Low unit weight is an important advantage of aluminium. Because of the comparatively high cost, its use is confined in most cars to pistons where its high thermal conductivity and low weight contribute to the efficient performance of the engine. Use of plastics for ornamental body parts and body hardware has acceler ated rapidly and extensive experiments are exploring the possi bilities of such materials for larger areas, particularly non-stressed body panels such as trunk lids, hood covers, etc.
Nickel is used for the electrodes of the spark-plug. The high melting point, electrical and thermal conductivity, as well as resistance to corrosion, are the properties which cause its selection for this service. It is also plated on radiator shells, lamp rims, etc., as a protective coating and for appearance, and in some cars the radiator shell is made entirely of this metal. Tungsten is used as contact points in the ignition circuit where the spark is timed to synchronize with the position of the piston. The re sistance of tungsten to corrosion and to the pitting which results from the electric spark is its principal recommendation. In the high tension magneto (q.v.) platinum points are generally used for the contact breaker.