Re: Stepper Dissasembly

Art, Ordinarily I would agree with you - however Mariss is a very,
very knowledgeable guy, so I listen carefully when he says something.
Then I know what I'm risking if I go ahead with a "not recommended"
project.

As for your rewiring of the slo-syns, I'm very interested in exactly
what you do. Do you simply seperate the two windings (the catalog
shows them often connected to a common terminal, with the other legs
seperate for the insertion of the phase shift cap) or do you parallel
a number of the individual coils for lower inductance?

I've got a cheap and nearly useless "IBM printer stepper" open at the
moment, and with both ends off I think one could patiently extract the
existing windings and rewind it with fewer turns of heavier guage wire
- WITHOUT removing the rotor. Shoot for the same number of
'ampere-turns' as in the original slow-syn coils and the original
torque figure should be preserved, but with much lower inductance.

Chris

> Just my two cents worth...Never listen when someone tells you

something is

> junk. I have dissassembled and fixed just about anything including

countless

> items that are "Do not take apart. It will never reassemble" able. I

have

> taken apart dozens of stepper motors, reassembled, and run them for

lengthy

> periods of time with no noticeable problem. Its the same thing with

rewiring

> the SloSyns, some folks said, they will never work, you'll only get

one RPM,

> You'd need 400VDC, the formula's prove.....etc.
> I just sit and watch them work great and smile.
> The only rules in hacking something together is...there are no

rules. If it

> works, it works, if it don't, you learn something. Just don't let

the smoke

> out, its hard to buy surplus smoke to replace it with.
>
> Art
> ----- Original Message -----
> From: <stratton@m...>
> To: <CAD_CAM_EDM_DRO@y...>
> Sent: Tuesday, May 29, 2001 5:08 PM
> Subject: [CAD_CAM_EDM_DRO] Re: Stepper Dissasembly
>
>
> > Please elaborate on how damaged motors 'murder drives'?
> > Do they generate excessive back EMF or something?
> >
> > My limited experience with small chopper drives is that they don't
> > seem to care if you short the outputs... they just produce very

short

> > chopping pulses.
> >
> > As for why it was in the trash, academics throw out lots of stuff,
> > especially when their lab space is being renovated. So it is an

open

> > question... I got a lot of goodies from that lab though.
> >
> > thanks,
> >
> > Chris
> >
> > -- In CAD_CAM_EDM_DRO@y..., mariss92705@y... wrote:
> > > Hi,
> > >
> > > Option (1) is my choice.
> > >
> > > If the rotor has been removed, it is probably de-magnetized and

it

> > > will murder drives. Also it is tough to tell if it has a shorted
> > turn
> > > in the winding. The givaway is increased detent torque over a

good

> > > motor. This will also make it a serial killer of drives. It

probably

> > > was in the trash for a reason:)
> > >
> > > Mariss
> > >
> > > --- In CAD_CAM_EDM_DRO@y..., Chris Stratton <stratton@m...>

wrote:

> > > > I've got another size-34 stepper from the trash at MIT, this

one

> > > > without a backplate on it. Electrically it is fine. So I
> > machined
> > > up
> > > > a replacement backplate, however the rotor binds in some
> > positions.
> > > >
> > > > Should I:
> > > >
> > > > 1) use it as a paperweight
> > > > 2) make another backplate with some means of centering the

bearing

> > > > 3) pull out the rotor (possibly weakening magnets?), clean,

and

> > > maybe
> > > > take a very light cut on it in the lathe?
> > > >
> > > > I realize neither 2 or 3 is going to yield a great motor,

question

> > > is
> > > > if it will yield something more than a paperweight.
> > > >
> > > > Chris
> > > >
> > > > --
> > > > Christopher C. Stratton, stratton@m...
> > > > Instrument Maker, Horn Player & Engineer
> > > > 22 Adrian Street, Somerville, MA 02143
> > > > http://www.mdc.net/~stratton
> > > > NEW PHONE NUMBER: (617) 628-1062 home, 253-2606 MIT
> >
> >
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