Hi, I am having a little trouble creating a motion for a spring. What I wanted is that when the center piece rotates, the spring stretchs or collapses based on distance from the center to the elipstical part. In other word, the lenght of the spring changes as the center piece rotate. When I rotate the center piece manually, everything seems fine, but I just can't achieve it in motion study.
I attached the assembly as a zip file. If anyone know how to fix this, please let me know.

I use SW 2012, and I really don't have access to SW 2013.