I had a broken micro RC car that used a gearbox with a tiny potentiometer on it for controlling the steering angle. I thought it would be interesting to replace the little potentiometer with a regular sized version so I could set the position either manually or from a microcontroller by driving the motor.
I drilled a bit of brass rod to fit over the gearbox output and to fit the stub of shaft on the back of the pot. I used some loctite and epoxy to connect the shafts together, and ran it a bit to get it all concentric, then epoxied a bit of aluminum strap to both.
The next step is to come up with some code to read the pot and drive the motor to the commanded position. Since it holds position without power to the motor, the h-bridge can be left idle except when it is moving to a commanded position, so that a user can turn the knob to adjust a setting.