Torsion springs are helical coil springs that exert a torque or rotary force and are subjected to bending stresses.
These torsion springs are wound right or left hand so that the deflection causes the spring to wind up from the free position.
The diameter of the torsion spring reduces in diameter when they wind up.
Most torsion springs have a center rod going through the coil for added support.
Torsion spring designs require the following as listed in the spring drawing below.