Hello all...I am trying to create a more realistic spring simulation.  What I have seen so far are simulations which just allow the helical portion to move, or attach closed ends in a discontinuous fashion.  The last ones can look quite good, but I am hoping to go further, to create a continuous spring from the shallow closed ends to to the helix which compresses and expands proportionally.  An older forum entry on this site showed me how I might go about this, by wrapping a sketch around a cylinder, then converting the result into a 3d sketch. 

I've had some initial success.  I can rebuild the attached spring at different heights, but when I try to save as an animation several frames show the spring as blank.  Please keep in mind that the model is in a very crude state, I did not want to get too complex with the closed end details until I'd proved the procedure to myself.

Please let me know if you have seen this before and if there is a simple solution.

This is in SolidWorks 2013.

Thanks in advance.