This is a Moebius gear I printed on my 3D printer. It has 11 gears. Usually odd numbers of gears can't be made into a circle because the last gear spins in the same direction as the first and they clash. This solves that problem by giving the gears a half twist along their length so the last one spins in the opposite direction to the first. These Moebius gears can also rotate in the polar direction.

These Moebius Gears were designed by Blake Courter. You can see his design here:
https://blog.grabcad.com/blog/2014/10...

This 3D print is his Moebius Gears version 4, which you can download here: https://grabcad.com/library/mobiusv4...

I also have a remixed version of them at half size on Thingiverse:
https://www.thingiverse.com/thing:362...

Dave