Gearbox with adjustable ratios

I had a need to slowly move a pinion gear on a rack. Using a DC Motor controller with my small hobby motors to lower the RPM, I had to sacrifice torque. A gearbox was my solution.

This is a generic but customizable gearbox, that exposes (via arcs in the face) two sides of the "driving" gear so that you can "engage" your motor. Your motor can be attached via your bracket (that you print), through the mounting holes on the faces. A bracket for a "DC 3-12V Gearmotor for ARDUINO Robot Smart Car" has been included.

https://www.youtube.com/watch?v=nSY02jBna0w