RE: [CAD_CAM_EDM_DRO] Re: Adding a Tail shaft to servo's with no tail shaft

> Tony,
> Per Marriss@gecko (ultimate authority on most everything motors):
>
> "The point was you do not want to remove the rotor from the stator.
> Resist the impulse to slip the rotor out just to see what it
> looks like when the motor end cap is off. If you do, you will
> demagnetize it even if it's for only a 2 second peek.
> Otherwise you are OK so long as the motor doesn't sweep any
> magnetic chips and dust into the gap. Do this stuff on a
> clean benchtop."
> <http://finance.groups.yahoo.com/group/geckodrive/message/1949>
>
> I don't know the physics on refrigerator doors but I know it
> was an issue with slot car motors back in the day and I have
> seen this referenced elsewhere.
>
> Roger

Well, he was talking about steppers, not your typical motor. I guess -
didn't read the link as it needs membership, but I've heard the comments
before. AFAIK, steppers are assembled then magnetised, so that may be the
reason.

It depends on the type of magnets used in the motors. The newer rare earth
ones are pretty tough. The older ones (like iron) would demagnetise if you
looked at them funny, or they got a bit too hot.

I'm dubious that a motor with modern (say rare earth) magnets will
demagnetise when you dismantle it. However, since most motors don't have
rare earth magnets, why not. Slot cars had crappy ferrites, and I don't
think AlNiCo (NiCo?) were that great either. I still doubt it, they're not
called permanent for nothing. If they were that easy to demagnetise,
stalling the motor would probably kill it.

What exactly is the cause? Pulling out the rotor while it's energised might
do something, but that's not easy to do. (An energised rotor shouldn't a
problem anyway...)

Unless someone has some docs on this happening to modern motors, I think
most of this falls under "Well, Faraday might have had a bit of trouble, but
things have gotten better since his day".

Tony