Manufacture of torsion springs

Made-to-measure torsion springs

A torsion spring generally consists of a helical body with two legs or ends that hook onto two parts, one fixed and one mobile. The torsion spring stores energy when it is twisted, i.e. when torque is applied around its axis. Unlike compression or tension springs, it neither extends nor compresses, but twists.

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Typology of torsion springs

Single and double body

There are several types of torsion spring.

The simple torsion spring is the most common. It consists of a helical body with two arms (or legs) that exert a torque when rotated relative to each other.
The double torsion spring consists of two single bodies connected at the centre. They can be wound in opposite directions and their outer legs are connected to one or two different elements.
Spiral torsion springs are specific forms of torsion springs. The wire is wound flat in a spiral, as in a mechanical watch. For more information on spiral springs, see the corresponding page.

Specific features of the torsion spring

Left or right

Depending on the application, torsion springs can be left-handed, right-handed or double. The latter configuration corresponds to two springs (left and right) wound from the same wire. To hold them in place, torsion springs are often mounted on a mandrel, axle or pin, which fits inside the coils.
CGR relies on its STRAIN advanced research laboratory to develop specific technical solutions for complex torsion spring dimensioning and manufacturing problems.

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FAQs

1How is the torque in a torsion spring calculated?

The rate of a torsion spring is the change in load over the change in angle. If we don’t have the information regarding the required loads and deflection but we have a sample for example, we use a formula that you can see here.

2Can torsion springs operate in both directions?

Yes. We can work the torsion springs in the unwind direction on rare occasions, to do this we need to use a different manufacturing process. The advice on materials also changes. This is down to the residual stress caused through manufacturing. Stress is beneficial for wind-up torsion springs and has an adverse effect on unwind torsion springs.

3What causes torsion spring failure?

This would be the same list as compression or tension springs: fatigue, relaxation, corrosion, embrittlement, wear, cracking and overload. With the addition of binding on the mandrel being a common cause.

4What are the best materials for high-cycle torsion springs?

Carbon steel and stainless steel are considered best for wind-up torsion springs with SiCr wire being considered for unwind applications. For high cycle torsion springs the design of the spring is more important. Open coiled springs with internal radial legs with as large mandrel as possible considering the maximum deflection (min diameter) the spring will achieve when working.