Re: A little experiment on demagnetization

Jeff,

That's jumping to conclusions. I only know for sure about the 53 in-
oz motor because I monkeyed with it. It's my conjecture the 82 in-oz
motor "may" have been disassembled. How much, how far, I have no clue
because I wasn't there. The evidence is circumstantial.

Just removing the end cap should have no negative effect as long as
the rotor stays entirely within the stator. I can't say what effect
partially removing it would have but it certainly can't help.
Touching the stator isn't the problem, opening the air-gap is. You
can have the rotor touch the stator all day.

I'll stand behind the 33% number though I have reason to suspect it's
more like 50%. The consequence is either bad or worse; it's a
distinction without a difference.

Mariss

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "jeffalanp <xylotex@h...>"
<xylotex@h...> wrote:

> Hi Mariss,
>
> It looks like your emperical evidece:
>
> 106 in-oz Unmolested Motor
> 82 in-oz Opened (but perhaps rotor not removed? <NEAT>)
> 53 in-oz Opended (rotor removed)
>
> suggests that
> 1) Just openeing the motor to look at/play with the wires (leaving
> rotor remaining inside?) can cause a significant torque loss.
> Question: Is this possibly becasue the rotor was allowed to touch

the

> stator? If the the rotor were somehow kept from comming in contact
> with the stator when opened, might it retain full magnetization?
>
> 2) Disassembling it essentailly can cut torque in half. Again the
> question: if the rotor were to be removed without touching the
> stator, would is loose as much torque.
>
> Any comments on the above?
>
> Thanks,
>
> Jeff
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Mariss Freimanis
> <mariss92705@y...>" <mariss92705@y...> wrote:
> > Hi,
> >
> > An addendum to the previous post. Something bothered me about the
> > data. The motors I used for the test came from a very nice 4" X,Y
> > table I got from Tim Goldstein made by New England Associates
> > Technology.
> >
> > Both motors had been modified by NEAT so that the wires came out
> the
> > front of the motors rather than the rear as is usual. That is the
> > reason I didn't want the motors after I re-motored the table with
> > some really nice Vexta PK268-03A "square" motors (sorry Tim).
> >
> > The thing that troubled me was 82 in-oz is low for that motor.
> >
> > I looked thru my vast motor harem until I found another 23D6209
> > motor, this time with conventional leads.
> >
> > I ran the same setup on this motor and got 23.5W at 5 revs per
> second
> > for a torque of 106 in-oz. That is more in line with what I would
> > expect for that motor.
> >
> > I would conclude both motors had been partially disassembled (and
> > demagnetized) to make the wiring modifications. The actual torque
> > loss is more like 50% rather than 33% when compared to a know

good

> > motor (106 in-oz vs. 53 in-oz).
> >
> > Mariss
> >
> > --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Mariss Freimanis
> > <mariss92705@y...>" <mariss92705@y...> wrote:
> > > Hi,
> > >
> > > When I don't know for sure, I run an experiment:-)
> > >
> > > 1) I took two identical motors, (Rapidsyn 23D6209, 4.7A @

1.7VDC)

> > > connected in full-winding mode and set the current to 2.4A per
> > phase
> > > on a G201. The power supply was 25VDC.
> > >
> > > 2) I removed the rotor from one motor, waited 5 seconds, then
> > > replaced it. The other motor was unmolested and would serve as
> the
> > > baseline unit.
> > >
> > > 3) Both motors were then run on a dyno and data was taken at 5
> revs
> > > per second (1,000 full steps per second).
> > >
> > > 4) The baseline motor delivered 18.25W to the dyno at that

speed

> > for
> > > a torque of 82.3 in-oz.
> > >
> > > 5) The molested motor delivered 11.75W for a torque of 52.9 in-

oz.

> > >
> > > 6) The calculated torque (and power) output for the

disassembled

> > > motor was 64% of the intact motor.
> > >
> > > 7) I removed the rotor again, leaving it out overnight before
> > > reassembling it for the second time and ran the above tests
> again.
> > > There was no additional deterioration in performance.
> > >
> > > Conclusions:
> > >
> > > 1) Demagnetization occurs immediately on disassembly.
> > >
> > > 2) The motor loses about 1/3 of its holding torque and and

power

> as
> > a
> > > consequence.
> > >
> > > This experiment applies to standard magnet motors. I have not
> tried
> > > it on the newer, rare-earth magnet motors. I like the ones I

have

> > too
> > > much to find out. Any volunteers?
> > >
> > > Mariss