SPRINGS, elastic contrivances of any kind having the power of recovering, by their elas ticity, their natural state after being bent or otherwise forced — interposed between two ob jects in order to impart or check motion or permit them to yield relatively to each other. A common variety of spring is the carriage or automobile spring which diminishes concus sion between the body and the frame or wheels. Another variety is the helical spring used to operate valves, etc. Modern carriage (car riages, automobiles, railway cars, etc.) springs consist of finely tempered pieces of steel so formed and fastened together that they strengthen each other, while allowing free play for the natural spring of each plate or leaf to act, and by so doing to absorb a large por tion of the vibration and jolting caused by the wheels passing over inequalities in the road. The springs are mounted between the axles and framework, so that the wheels when passing over an obstruction or sinking into a hollow, compress or expand them, in the first instance, the motion being thus partly absorbed and partly passed on to the frame in a much lessened degree, and with the shock consider ably deadened by passing through this elastic medium. Carriage and automobile springs are made in a variety of shapes. The elliptic spring consists of two halves fastened together with bolts; the top half is attached to the frame and the bottom half to the axle by bolts or slips in the centre. Varieties of the elliptic are the half-elliptic or semi-elliptic and the three-quarter-elliptic, in which an iron attached to the frame takes the place of one-half or more of the upper part of the ellipse. The grasshopper spring is arc-shaped with linking plates for attaching to shackle The volute spring is a type now in favor for heavy vehicles.
When a spring made up of several leaves, plates or laminations is compressed, the various leaves must slide upon each other. This sliding motion is constantly taking place while the vehicle is traveling. To facilitate the slide
movement the leaves are lubricated. The top member of the ordinary auto or carriage spring is of stout spring steel, with lugs forged on each end of it, by means of which it is attached to the shackles. It is furnished with lubrica tors and slots through which the oil flows to the various grooves. For high-speed vehicles it has been found advisable to lengthen the spring considerably and increase the circle of which the spring forms an arc. Consequently the spring is more nearly horizontal. In power driven road vehicles radius rods are used to take up the drive and other thrusts which tend to alter the position of the rear axle in regard to the frame. The rods tend to locate the axle relatively to the frame. Horn plates are used to prevent the side movement of the springs, while in some cases rollers are used to prevent the axle from moving laterally relatively to the frame. The rollers come up against the surface of the horn plates. The helical spring is a length of metal of either round or rect angular section, wound round an imaginary cylinder. It is commonly miscalled a spiral spring. The corkscrew gives an idea of the helical spring. The spiral spring is a length of metal wound in a curve of continually decreasing or increasing radius. When wound it is quite flat. The main-spring and the hair-spring of a watch are spiral springs. The trembler spring is a flat spring used in coils and in contact breakers in order to make and break contact. The volute spring is a combination of the helical and the spiral spring. Helical and volute springs are in general use in modern machinery of several types, but are especially used in in ternal combustion engines to return the valves to their seatings. Other uses of the helical spring will instantly occur to every reader.