I personally don't like to have to make shafts for all the spare motors, especially for these motors and the task at hand. I try to use motors as they come out of the box. Replacement is much easier. We use double set screws with a Loctite adhesive that is advertised for polycarbonate. In addition, since the motor shaft does not come through the back of the motor, you risk damaging the rear bushing pressing your drive shaft onto the motor shaft. If you still insist on removing the pinion gear, I suggest making a push plate that will go in the area between the back of the pinion and the front of the motor housing. However, you still have the problem pushing the drive shaft onto the motor shaft. I would rather use that same push plate to press the drive shaft directly onto the pinion gear.
Nice design - quick build and effective. However, by St. Louis, consistency with deployment and dependability are likely going to be the deciding factors. You can only lighten so much, push the amps only so far, before you plateau with the minibot design. We're saving our best for St. Louis.
