Mounting Hub for 3mm D-shaft motor and 16 tooth LEGO gear (Short Version)

thingiverse

I needed a compact way to mount a 16 tooth LEGO gear to a 3mm D-shaft motor, like Pololu's Micro Metal Gearmotors, so I built this hub that uses the 4 circular holes on the gear instead of the cross axle to get a more compact fit. I designed it to fit snugly on A 3mm motor shaft when printed on a Makerbot Dual; if the fit isn't quite right on the motor axle, try changing the print size by a couple percentage points. You may also want to increase the number of shells; the D where the motor shaft mounts was worn to a smooth circle on an early version of the hub by the motor after a few hours of driving. I've also attached the Inventor file if you need to change make the hub longer.