Parametric Robot Wheel (Spiral)

NOTE: This has been upgraded to a much more flexible version that incorporates all previous designs and adds lots of new features.

The new version is here: http://www.thingiverse.com/thing:21486

This is a flexible parametric robot wheel with a "spiral" pattern for o-ring tires. It's a variation of the biohazard wheel code here thingiverse.com/thing:21010 -- but it's tweaked a bit to support the spirals design specifically. (At some point I'll probably try to join them all together...)