Gearbox for FTC Tetrix / AndyMark motors. Slows motor speed down by 9:1. Requires three 6-32 x 1" screws, a Tetrix motor hub, small screws to mount the part to your motor of choice, three standard Tetrix nuts, and one 6200ZZ bearing ($1.49 at vxb.com). Thanks to all the great hypocycloid gearbox references out there and to the hypocycloid examples on Thingiverse. http://youtu.be/xktsFLkfRtoPrint all the pieces. No support required. Screw the mountBottom piece onto the Tetrix or Andymark motor. Push the shaft piece over the motor shaft. Put the bearing in the cam piece. Push the bearing/cam over the shaft piece. Attach the ringAndHubMount piece to a Tetrix motor hub and remove the hub set screw. Put the ringAndHubMount piece over the cam piece. Put the mountTop piece over everything and screw the mountTop and mountBottom pieces together.