On Tue, 26 Nov 2013 18:20:54 +0000, Cydrome Leader wrote:

wrote:
I've been looking at the brushless motors used for RC planes and the
like. They are amazingly powerful for their size. And they really spin
up fast! One web site has kits you can buy to wind your own armatures.
Anyway, I have been wanting a rotary tool that is a cross between a
Dremel and an air powered tool I have. Something with an OD of about 1
inch. Like a Foredom handpiece. Faster than any of my Dremels but
slower than my small air powered hanpiece that spins at 80,000 rpm. So
I'm thinking one of the "inrunner" type motors might work. At 80,000
rpm the surface speed is about 2600 SFPM. Even though the speed drops
quickly as soon as the rotary tool contacts the work the speed is still
too high for carbide on steel and the burrs and rotary files dull
quickly, which makes them cut slower. On the other hand, the Dremel and
Foredom rotary tools are too slow and this ends up costing time too.
Something that spins about 40,000 rpm and maintains that speed along
with the smaller diameter would be great. In fact, a tool that was .75
or even .625 diameter would be even better. I have a dental handpiece
that I use for some delicate work and it is just under .5 diameter and
is very easy to hold because of the small diameter. If I could build an
electric rotary tool with the torque of a Dremel, 40,000 rpm, and 1/2
inch in diameter I would be very happy. Even one that matched the
Dremel torque and speed specs but was 5/8 or 1/2 inch diameter would
please me greatly. So, anyone here play with brushless RC motors?
Thanks,
Eric,

you may have problems unless them motor has internal position sensors/
more than three fat power leads. They're mean to run fans or a gearbox
and a fan with no sudden load changes. Brushless fan controllers don't
tend to like loads other than air, or they get confused and lock up and
do other nutty stuff.

The RC controllers may be more tolerant of this, but again, if the motor
lacks position sensors, it's probably not meant for dealing with abrupt
load changes or putting out lots of torque at low speeds.

Damn. I should have thought of that when I made my response. RC
airplane propellers are pretty much fans, as are (well, duh) ducted fans.

RC car motors have sensors, and come in a variety of sizes.

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com