> From: "William Beaty" <bi...@eskimo.com> > Sent: Friday, April 12, 2013 12:16:29 PM
> I don't know if such a thing is even possible. But from the history > of the "magnet motor" crowd, probably it can be done, just as long as > the rotor has near zero load and only must supply frictional losses to > some extremely low-friction bearings. Except that it has usually been demonstrated with a propeller attached to the shaft, currently a 10 (diameter) x 16 (pitch) http://www.modellbau-hp.de/xtcommerce/Flugzubehoer/Luftschrauben/APC-Elektro/APC-Luftschraube-16-x-10-Elektro-Propeller-40-6-x-25-4-in-cm::1286.html It ran 5 1/2 hours around 2500 rpm. (In previous public demos the fan was pointed into a tube, and the velocity measured at the exit. The mass of air accelerated (velocity * area) can be used to calculate the power. ISTR it was about 1/2 horsepower -- with a different fan. I guess you could get a motor and the same fan and see what HP is needed to get it to 2500 rpm. (There should be thrust v rpm data somewhere for similar propellers). Definitely non-zero. Thrust calculator http://members.jcom.home.ne.jp/4223215501/staticthrust.htm Plugging diameter 10" pitch 16" 2500 rpm and 100% efficiency gives 12W = 0.02 HP (Seems a bit low? ) They are now demonstrating with a smaller, less controllable motor.
