SPRINGS
Fig. 48.—A, Full elliptic spring; B, half elliptic spring.
In addition to tires, an automobile is fitted with springs, which are necessary to absorb the shocks and jolts that are too great to be taken up by the tires. These are usually full or half elliptic (Fig. 48), and made of flat plates, or leaves, of different lengths, the small being placed on the large, and all bound together at the center. The combined action of the springs and tires permits the frame and body of the car to move in a nearly straight line, while the wheels and axles follow the inequalities of the road. When springs break, as is frequently the case, it is from the rebound of the body that results when the wheels drop into a deep hole, the upward movement separating the leaves, and the entire strain coming on the long leaves alone. To prevent this, shock absorbers are recommended, which permit the springs to have a certain amount of action, but check them if they tend to expand or compress to too great an extent. They act either by the friction between metal plates and washers, or by air or oil in a cylinder that permits a piston to move freely to a certain degree, but presents resistance to a greater motion. Shock absorbers are placed between the axles and frame, and there should be four, two to each axle.