Torsion Springs are helical springs that exert a torque or rotary force. The ends of torsion springs are attached to other components, and when those components rotate around the center of the spring, the spring tries to push them back to their original position. Common torsion springs are used in clothes pins, clipboards, swing-down tailgates and garage doors. Torsion springs are used for hinges, counterbalances and lever return applications. Sizes range from miniature, used in electronic devices, to large torsion springs used in chair control units to push them back to their original position.
When Ordering a Torsion Spring,Remember to Give The Following Information As Completely As Possible:
- Inside or Outside Diameter.
- If spring works on a rod, give size of same, as spring must not bind when wound up to its limit of travel.
- Free length and number of coils. If spring cannot increase in length as wound up, allow sufficient space between coils.
- Right or Left Hand Wound.
- Wire Size. Decimal size if possible. Material, Kind and Grade.
- Style of Ends, (see illustrations). Number of turns deflection to hold given load and radius of loaded arm. This length may be the length of the arm, or the arm may be attached to a movable machine member, in which case the length to point of application of load is given.
- Finish, Plain unless otherwise specified.
Torsion Spring Design Formulas and Specifications
The basic formulas for torque or Moment (M) and bending stress (S) used in designing torsion springs are shown below.
D = Mean Coil diameter, in. (mm)
d = Diameter of round wire, in. (mm)
Nt = Number of coils
E = Modulus of elasticity, psi (MPa)
T = Deflection, number of turns or revolutions of spring
S = Bending Stress, psi (MPa)
M = Momment of torque, lb*in (N*mm)
b = Width, in. (mm)
t = Thickness, in. (mm)
Material:
- Music Wire per ASTM A228, DIN 17223 or JIS-G-3522
- Stainless Steel Type 301/302/304 OR Type 316 per ASTM A313, DIN 17224,or JIS-G-4314
- Oil Tempered MB per ASTM A229, DIN 17223
- Oil Tempered Chrome Silicon per ASTM A401, DIN 17223
Special material are also available upon request.