Lego Technics 37.5mm Gearmotor Adaptor

This is an easy way to add a 37.5mm gear motor to to your lego technics mechanical prototype.  I use this to quickly mockup a mechanical system so that I can work on the electronics and software to drive the system.  A press fit 21t XL belt pulley is also included for the gear motor.  It can use a 3mm set screw with either square or hex nut.

For a strong motor like this I highly recommend using axles to attach it to a thick plate, although pins will also work.