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.
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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.