Here are the 3D printed prototypes. Super small we made them really dense so we could do performance testing with wheel tuning and gearing on that.
Supper small the whole bottom yoke is smaller then your standard 4 inch wheel.
http://imgur.com/a/spJtM
On a side note you could put this on a ftc robot.... with ease they sell plastic gears identical to the ones we would use and the 3d print with some fine tunning could print something i would put on a robot.