Springs - for animation, visualization, interference detection

At Solidworks World, Robert McDonald showed a really terrific sample
animation of a compression spring.
I made the mistake of commenting that, for the sake of an animation, it is
rough to use a helical sweep feature to make the spring because you take a
beating on the rebuild time, and that techniques existed using simple,
fast-rebuilding revolves to simulate a spring (at least well-enough to serve
an animation)

Big mistake - next thing I know, I have a handful of people handing me
business cards so I could send them a sample model.

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.

www.edeaton.com/SwxDownload/Torsion_spring.zip
www.edeaton.com/SwxDownload/Extension_spring.zip
www.edeaton.com/SwxDownload/Compression_spring.zip

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. The spring I did a few
years ago used equal sketch relations to flex the spring, so it would be a
lot of work to make any cahnge. I figured I ought to beat the limitation if
I was going to share it.

-Ed