The standard motor is 48 mm diameter. The holes it fits through are not much bigger, 52 mm I think, and there is not much scope to open them up. Once the motor gets much bigger their is nowhere to put it except outside the headstock. I should mention that I know where to find a suitable motor, but I think it costs too much. Maxon do a range of motors at 45 mm diameter, 12, 18, 24, 36 & 48 V, max revs from about 5000 to about 10000, but they cost over ?500 and need a separate drive circuit which I think costs another ?70. Say ?600 for the pair. Then the motor has a large terminal box on the end but I think it would just about fit. The 250 W version would fit better in a sense, in that it is longer, but unless such a motor turns up in someone's junk box it's all a bit academic.
I did find a website which gave some motor details in sensible numbers, but then I could see no way to relate a suitable drive to the motors. Unfortunately our local RC shop, which used to be large and comprehensive, has turned to mainly mail order. I'm sure they have something on the shelf that would do the job, but they no longer chat to customers over the counter.
Years ago someone here said he had successfully used an RC motor on a Unimat, I think a DB/SL, but never gave details of what he had used. It's all a bit frustrating.
Keith
