# HSM16 Torsion of a Spiral Spring

Spiral springs are used to provide a resisting or restoring torque to a shaft when it is rotated through an angular displacement. They exhibit similar stiffness characteristics to linear springs, except that the effect is one of torque rather than force. The stiffness of a spiral spring depends on its physical dimensions and the rigidity of the steel strip from which it is formed. With this apparatus the student can easily calculate the theoretical stiffness of the spring, and compare the value with simple experimental results. The wall mounted unit consists of a spiral spring coiled from a length of steel strip. One end of the spring is attached to a shaft mounted in ball bearings. A load hanger and calibrated weights is used to incrementally load the spring. Spring deflection is measured with an attached 360° scale.

Spiral springs are used to provide a resisting or restoring torque to a shaft when it is rotated through an angular displacement. They exhibit similar stiffness characteristics to linear springs, except that the effect is one of torque rather than force. The stiffness of a spiral spring depends on its physical dimensions and the rigidity of the steel strip from which it is formed.

• To compare the experimental stiffness of a plane spiral spring with theoretical predictions.
• To observe if the spring exhibits a linear elastic behaviour.