The basic design of torsion springs means that they exert pressure along a circular path—in other words, they provide torque. This may be confusing to users who look at the stresses of compression and extension springs and compare them to the stresses of a torsion spring, which are subject to “bending stresses”. A spring manufacturer may also create these torsion products under the product names of flat coil, motor, or power springs.
When a manufacturer discusses torsion spring products, they are usually talking about a helical spring that is made with round, square or rectangular wire that has been loaded by a torque. Round wire is the most common type of wire used; however, rectangular wire is sometimes more efficient to this type of stress loading. There are so many different applications for torsion springs that none are actually standards. When clients contacts a manufacturer, they will need to have a drawing or a sample that demonstrates the type of ends required, as well as spell out any dimension specifications, including maximum outside diameter, minimum interior diameter, length, coil numbers, wire size and whether the spring should be right or left-handed. Sometimes these specifications are not actually known by the customer, in which case the spring manufacturer should be able to fabricate the necessary springs by receiving the following information:
- The torque, in inch-pounds, at the loaded position
- The angular relation of the spring’s ends when they are at this load
- The angular relation of the ends when the spring is free, if necessary
- The degrees of travel beyond the torsion spring’s loaded position
- The diameter of the shaft, or hub, the spring must fit over during the application
Often, a torsion spring is closed coiled, which means there is not space between the coils. As a result, variations in length occur when there is a variation in the wire’s diameter and the actual number of coils. It is also important to remember that when the spring is wound up onto one coil, it has increased in length by a wire size; for two coil winding, it increases by two wire sizes. Users will need to allow clearance of this extra length. Torsion springs should always activate their load in a direction that actually increases the diameter of the coils, but in a few applications the springs are activated by “unwinding” them. These applications are always performed with small travel under confined conditions that will prevent the end coils from bending outward. Finally, when a torsion spring is designed to operate by reducing coil diameter, the hub or shaft the spring operates over needs to be about 90% of the smallest inside diameter that the spring is reduced to. Without this good support, the spring will be prone to fail early.
Katy Spring and Manufacturing, Inc. is a full service custom metal forming and Houston spring manufacturer company with years of experience in fabricated many types of springs and metal components. We can create the torsion spring you need for your application, just call us today at 281-391-1888 with your specifications.