Spring motor remix

A remix of the "PLA Spring Motor Demonstrator".

It adjusts some tolerances and changes the shaft for the main gear so that it is mounted on the frame instead of the spring. I was using this for experimenting with different springs, so the spring is mounted outside the frame to make it easy to change. Two springs are included: one with a 2mm x 6mm cross section and one with a 4mm x 6mm cross section. The second one gives higher power but does not run as long.

https://goo.gl/photos/UP5KTELi2UXVnygN8 to see it running.