The spring rate [R] indicates the force generated by the spring, depending on the compression / stretch / angular rotation. For an extension and compression spring, the spring rate is expressed in [Newton per millimetre] and for torsion springs in [Newton per grade angular rotation].
For an extension or compressing spring:
With G= Rigidity modulus, d=wire thickness, n= number of active coils, D= heartmean diameter of the spring.Met G= afschuivingsmodulus, d=draaddikte, n= aantal werkzame wikkelingen, D= hart op hart diameter van de veer.
For a torsion spring:
With E= elasticity modulus, d=wire thickness, L1 and L2 are arm lengths, n= number of active coils, D= mean diameter of the spring.