Spring for Rotation? I have a question about rigid body constraints.

Generic spring constraints can be used for a normal spring that tries to return to an original length by setting the stiffness.

However, what I want is a spring for rotation that tries to return to it's original rotation state. It seems that the generic spring's stiffness 
parameter is only for length and not for rotation.
I can limit the rotation angle, but, that's just a limit setting and not for spring strength or anything.

Is there a way to make a rotational spring?
If you're like me and wanted to make a rotational spring C between points A and B, such that it can rotate around point B, then you can make this construction with three objects. Two icospheres (for example), one at point B and one at point A. A cylinder is your rotational spring, and goes between the points. You add a spring constraint between icospheres A and B. Affix the cylinder C and icosphere A together with a fixed constraint. Affix the cylinder C and icosphere B together with a generic constraint, with all translation axes limited to 0 - 0. Then attach B to whatever object your rotational spring needs to be attached to.