Torsion Springs
Definition and Purchasing Considerations
Compare and Contact Manufacturers of Torsion Springs
Discuss torsion springs and other topics on the Message Forums
Springs are mechanical components that have mechanical energy stored in them, capable of undergoing structural changes when subjected to external forces. 
Springs are available in many types. Some important types of springs are: leaf springs, compression springs, extension springs, disc springs, snap spring, torsion springs, etc. Torsion springs are designed to offer resistance to externally applied torque. By definition torque is a force that tends to produce rotation. Torsion springs exert torque in a circular arc and the arms are rotated about the central axis. The ends of a torsion spring are rotated in an angular deflection. Although the name implies otherwise, a torsion spring is subjected to bending stress rather than torsion stress. A torsion spring performs at its best when supported by a rod (mandrel) or tube that is coincident with the hinge line of the final product. This type of spring is normally close wound but can have pitch to reduce friction between the coils.
Common types of ends on torsion springs are hook, hinged, straight offset and straight torsion ends. To produce them requires limited tooling. Space and size utilization is dependant on the torque required and the end formation used. In application determination, the Inside Diameter (I.D.) and the spring length are needed for proper sizing. Torsion springs may either have a right hand coil or a left hand coil.
A unique type of torsion spring is a double torsion spring. This consists of one set of coils coiled right hand and one set of coils coiled left hand. These coils are connected and work in parallel. These sections are designed separately with the total torque being the sum of the two.
Formulas for Torsion Springs:
1. Torque (Moment) is the applied force in pounds pushing at a right angle to the leg times its distance in inches to the centerline of the spring body: Torque = Load x Length
If the torque required to rotate the spring through a given angle is needed, then the Torque formula is: Torque = Rate x Degrees
2. The degrees in the following formula relate to the angular deflection through which the spring leg is required to rotate. This allows you to calculate the spring constant rate: Rate = Torque / Degrees. Rate for round wire, helical torsion springs: Rate = PL / Θ
3. Relative angle orientation of the spring is determined by the number of coils in the spring:
- An even number of coils produces a flat or 180° angle to the spring
- An even number of coils plus an 1/8 of a turn will produce a 45° angle to the spring
- An even number of coils plus 1/4 turn will produce a 90° angle to the spring
- An even number of coils plus 3/4 turn will produce a 270° angle to the spring.
4. Stress in bending in p.s.i.: S = 32PLK / πd3
- P = Load in Lbs.
- L = Moment arm in inches
- Θ (Theta) = Angle of deflection in degrees
- π (pi) = 3.14159
- E = 30 x 106 (28 x 106/stainless), Young's Modulus
- d = Wire diameter in inches
- D = Body mean diameter (O. D. –d) in inches
- O. D. = Outside Diameter in inches
- N = Number of coils
- K = Stress correction factor
- R = Rate in Lbs./degrees
Materials used for Fabricating Torsion Springs:
Alloys of steel are used to manufacture most types of springs. Some of the most common types of spring steels are oil tempered wire, chrome silicon, chrome vanadium, 302 and 17-7 stainless. Depending on the characteristics and need of the applications a few other materials are also used to fabricate springs. Beryllium copper, phosphor bronze, Inconel, Monel, and titanium are some of the other materials used to make springs.
Applications:
As examples of their use, torsion springs are found in garage doors, automotive assemblies, tools, machinery, toys and appliances. Torsion springs come in a wide variety of sizes and strengths.
Search for torsion spring manufacturers in Zycon
Go to the Zycon home page
