SPRINGS AND RIDING QUALITY Front Suspension.—There are two systems of front suspen sion which are used on the chassis of motor vehicles. These are, first, the axle type employing laminated leaf springs which are generally of the semi-elliptic variety, and, second, the independent suspension type wherein each front wheel may move independ ently of the other.
With the axle type, the laminated springs are generally mounted on the axle, being attached thereto by means of spring plates and U bolts. In the designs using semi-elliptic springs, the front end of the spring is usually attached to the frame by means of a pin joint, and the rear end by means of a swinging shackle which allows for the change in length as the spring is straightened under load. A single transverse spring, one that is parallel to the front axle, is also used. With this method it is necessary to guide the front axle by means of radius rods. The laminated leaf springs are generally composed of from 6 to 16 leaves, made of plain or alloy steel. Important among the various types of independent sus pension systems are those using coiled springs and those using transverse leaf springs. The coiled spring type is most used. Many of the coil spring systems use a similar construction employing wish-bone type links, coil springs of silico-manganese steel, and torsional stabilizers. A majority of American cars (1940) incor porate independent front-wheel suspension.
Rear Suspension.—Laminated leaf springs are generally used for the rear suspension of the chassis although other types of springs are sometimes used, particularly with independent rear wheel suspension. The semi-elliptic leaf springs are attached to the rear axle in the same manner as those used on the front. The two types of drives generally used on automobiles are Hotch kiss drive and the torque tube drive. With the Hotchkiss drive, the springs transmit the driving force and braking torque, and are often designed to be nearly straight under average load so that the driving force is directed along them. With the torque
tube drive, the propeller shaft is enclosed in a tube which connects the rear axle housing with the transmission. This tube absorbs the driving force and braking torque, thus relieving the rear springs of that duty.
The cantilever type of spring, often used on higher priced cars, is merely an inverted semi-elliptic spring having the centre at tached to the frame by means of a trunnion bearing and the front end attached to the frame by means of a swinging shackle, the free end resting upon the axle with a pin joint.
The rear springs are generally much longer than the front semi-elliptic springs and are much softer.
Riding Quality.—Independent suspension of the front wheels has done much toward improving the riding qualities of the auto mobile. With such a system it is possible to use very soft front springs, thus making the spring rates of the front and rear equal or nearly so. Since, technically speaking, the front axle has been removed and a. stiff front cross member added to the frame, it is possible to move the engine forward, without encountering inter ference with the front axle. This gives a new distribution of weight to the vehicle and promotes better riding qualities. The unsprung weight, that weight which is not supported by the spring, has been reduced considerably—another factor which im proves the ride.
To prevent continuous oscillations or rapid rebound, some auxiliary damping device such as a shock absorber is mounted be tween the frame and the wheel axle. These shock absorbers are generally of the hydraulic friction or mechanical friction variety. To further increase the riding quality, a roll stabilizer is some times added either at the front or rear end of the chassis or both. The stabilizer consists of a spring steel bar, interconnected be tween the front or rear shock absorbers. The bar tends to reduce the tendency toward roll on curves.