spring, in mechanics, any of several elastic devices used
variously to store and to furnish energy, to absorb shock, to
sustain the pressure between contacting surfaces, and to resist
tensional or compressional stress. Springs are made of an
elastic material, e.g., specially formulated steel alloys or
certain types of rubber or plastic. A torsion spring that stores
energy, e.g., for operating a watch, is a metal strip wound
spirally around a fixed center. For reducing concussion in some
heavy trucks and railroad cars, helical, or coil, springs are
used. Coil springs are commonly used for the same purpose in
automobiles, as are leaf springs that consist of flat bars
clamped together. These have been replaced in some vehicles by
torsion bars that absorb stresses by twisting. The helical-coil
compression spring provides the force to keep the operating
surfaces together in the friction clutch (see transmission). The
extension spring is employed for the spring balance; the
distance through which it is extended dep