Animtion/ Rigging a spring toy

fade1

I need to animate a moving spring. Any tips how to rig this, as the joint hierachy reverses after one turn(if animeted straight forward with FK)

example picture of a toy spring
http://www.lispring.com/photo/pc229384-metal_slinky_spring_toy.jpg

Mrfred

I'd try using a custom spline Ik setup. The only downward/issue I can think of with this solution is the possible lost of shape but I think this can be fixed by using either a shape template to help the animator track the position in space ( bone should move in a arc shape) or use path constraint...