[tjwolter]

drill motors for this application are touchy. You need to very firmly support the "outboard" end of the shaft or the planetary gearbox will strip. If I recall some prior misadventures you also have to lock the clutch by putting in some set screws. Or find older drills without clutches. These are harder to find and tend to be 7.2 volts. They are nice and frisky at 12v. But unless you are sold on drill motors may I suggest the humble Barby Jeep gearbox? Cheap. Durable. Can handle 24 volts for a while. So many around that a four wheel drive machine, which you will want, will be bargain basement.

You would be happier with the end result


T. Wolter