When I powered R2 back up tonight, his right motor was not moving. After some troubleshooting, I determined the problem was with the motor itself. I removed the motor and applied 12 volts to it. As I rotated the motor case around in my hand, the motor would occasionally engage. That made my 24 volt conversion inside the motor my primary suspect.
I opened up the motor, and it seemed as though the solder joint was somewhat loose, so I resoldered it. A few minutes later when I reapplied power, I saw a tiny spark from under the motor's circuit board, and the motor was history. I don't know why that happened. I'm slowly frying my droid, one part at a time.
The big bummer of all this is not so much that the motor is trashed, but that it meant all the work I did on the shaft adapter was wasted, since the shaft adapter is JB Welded to the motor shaft. So I had to grab another shaft adapter, open up the base to fit the profile of the motor shaft, and JB Weld it onto a new motor. I'll pin it tomorrow, after the JB Weld has dried. (Hmm... maybe I should have tried 24 volts before JB Welding the shaft adapter onto the shaft, eh?)
I also finally got around to gluing down the new bottom door holders on the outer foot shell doors. I'll nail in the pivot pieces tomorrow, and then the foot shells should be ready for a reprime and paint, although I still need to drill some small holes through the top of the outer foot shells, to allow the wires to pass from the legs on into the feet.