- Torsion coefficient links here.
A
torsion spring is a
spring that works by
torsion or twisting; that is, a flexible
elastic object that stores
mechanical energy when it is twisted. When it is twisted, it exerts a force (actually
torque) in the opposite direction, proportional to the amount (angle) it is twisted. There are two types. A
torsion bar is a straight bar of metal or rubber that is subjected to twisting (
shear stress) about its axis by torque applied at its ends. A more delicate form used in sensitive instruments, called a
torsion fiber consists of a
fiber of silk, glass, or
quartz under tension, that is twisted about its axis. The other type, a
helical torsion spring, is a metal rod or wire in the shape of a
helix (coil) that is subjected to twisting about the axis of the coil by sideways forces (
bending moments) applied to its ends, twisting the coil tighter. This terminology can be confusing because in a helical torsion spring the forces acting on the wire are actually bending stresses, not
torsional (shear) stresses.