I posted the following a month ago - maybe it would help:
The links below will allow you to download the compression spring, and an
extension and torsion spring I had laying around. The models are for
education on modeling strategy only - I did not look up any springs for
real, nor did I take a ton of time to clean up the models the way I would if
I was doing them for a customer/delivering to a customer.
By the way, the compression spring is kind of cool because it shows a trick
for getting equations to evalaute betwen frames in an animation. I needed
the spring to be equation driven so anyone could use it to add coils, change
diameter, etc without doing a lot of reconstruction.