Since we're on the subject of Omni-wheels, I should mention that there is a new white paper on this subject. It's called
TechnoKat Trick Wheel.
This paper includes a detailed mechanical print package for an "omni-wheel" (we call them Trick Wheels). The one in the print package was used in 2003. The designer & developer of this module is Mark Koors, TechnoKat & Delphi engineer.
Andy B.