Hmmm. A perm. magnet motor. "Suddenly one day" it ran away too fast for the horse. It would have to be shunt wound, (no field windings to series). If the pot* was dead-shorted, it's got a new one now. A wiring problem causing a short-circuit of the potentiomer* perhaps? Difficult to envisage how, but it is possible. For this use though, traction, I would have thought a 'series' type the obvious motor choice.
Alan
ps. * Afterthought. More a rheostat than a pot if all the current has to flow through a resistance for speed control.
[This message has been edited by Alan Belson (edited 08-09-2005).]
