Geof - your earlier reply was gratefully received and understood to be what you know from experience which is exactly the sort of response I was looking for.
Meanwhlie I've been reading up on AC induction motors here:
http://en.wikipedia.org/wiki/Induction_motor
Oddly enough there is a picture of a Clarke motor at the top of that page and a description of why single phase motors need a starting capacitor. I did wonder why there didn't appear to be brushes in the motor and now I know.
