Coil springs
A torsion spring is a helical elastic component designed to generate torque and store angular energy in rotational mechanisms. Wire diameter typically ranges from 0.3 to 18 millimeters, and mean coil diameter varies between 5 and 180 millimeters. The shear modulus of spring steel is approximately 79 gigapascals, and allowable bending stress ranges from 600 to 1200 megapascals. Effective working angle is defined between 30 and 270 degrees depending on design. The torque rate is calculated using k equals Ed to the fourth power divided by 10.8nD. The spring index is commonly selected between 4 and 12 to control stress concentration.
The structure consists of a helical body with two straight or angular legs measuring 5 to 250 millimeters in length. The number of active coils typically ranges from 2 to 15 to achieve required angular stiffness. Stress relief heat treatment is performed between 250 and 420 degrees Celsius. Final hardness of carbon steel after treatment ranges from 44 to 52 HRC. Maximum allowable stress at the leg junction is limited to less than 80 percent of yield strength. Quality control includes torque angle testing, fatigue evaluation up to 10^6 cycles, and angular deviation measurement within ±1 degree.
