Ok, I heard someone was taking my name in vain!!

Mike,
Astroflight 40s..So were do you want to start?
I could write a dissertation on he pros and cons of this motor, we have 6 (soon to be 10) of these things spread across our feathers.
The 15:1 planetary g/box (model 940P)is a truly superb traction motor check outhttp://www.pillowtorque.com/tech.htmhttp://www.pillowtorque.com/tech.htm for an example of an extreme featherweight drive train. Also take a look at http://www.pillowtorque.com/pillow_fight.htmhttp://www.pillowtorque.com/pillow_fight.htm for a twin motor application using the model 40 motor without the g/box as a spinner drive.
The 940P is a very rugged drive unit but requires mounting properly using the four M4 tapped holes in the face of the gearbox and for best results the motor supported too.
The 12mm output shaft, although quite capable of having a wheel mounted directly to this shaft there is a possible issue with long term repeated shock loads weakening the front bearing. We have found that this can be avoided by using a separate axle for wheel support driven by a belt/chain from a pully/sprocket mounted on the gearbox. (see Pillow Torque) Mounted like this they are entirely reliable, we have had the same units in Pillow Torque for the better part of 2 years completing over 125 fights (mostly at 100% duty) plus many hours of testing and only now are we replacing the motor brushes and repacking the gearbox with new grease. Other than that they have had no maintenance whatsoever. As Gary points out that due to the silly amounts of power they can deliver they do produce a lot of heat, which at first seems quite worrying but we have learned that these motors are quite happy to run at 100 C all day!BUT and its a BIG BUT if you are using the motor alone as a weapons drive, then gear ratio is CRITICAL. These motors run at around 16,300RPM @ 24V We have found that a reduction ratio of a MINIMUM of 3:1 is required to prevent the heat build-up eventually melting the whole thing (ask Ewan what happens to them at 2:1!!) I would prefer a ratio of 4-4.5:1 for peace of mind.
If you want dimensions for the 940P they are herehttp://www.teamwhyachi.com/misc/A40P.pdfhttp://www.teamwhyachi.com/misc/A40P.pdfthe full spec. of the motor alone is here http://www.robotcombat.com/marketplace_astroflight.htmlhttp://www.robotcombat.com/marketplace_astroflight.html You may also want to check out these alternative gear boxes http://www.teamwhyachi.com/Twa40.htmhttp://www.teamwhyachi.com/Twa40.htm
Both Team Whyachi and Robot combat are good sources of the motors and will happily ship to the UK .

If you want any further info e-mail me teamscorpion@aol.com and Ill try to help.

Regards,
Geoff.