I would like to repair a 12 VDC PM field motor which has one field
piece
loose. The adhesive yielded and one pole fell off. In the process of
cleaning off the old adhesive I lost track of the correct orientation
of the
loose field piece. It can go into the motor frame in either of two
ways. Both of
the field pieces are marked with a dot on one end. Do the dots go in
the
same direction or in the opposite direction.

Desperate in LA

"eeeeees" wrote in message
...
I would like to repair a 12 VDC PM field motor which has one field
piece
loose. The adhesive yielded and one pole fell off. In the process of
cleaning off the old adhesive I lost track of the correct orientation
of the
loose field piece. It can go into the motor frame in either of two
ways. Both of
the field pieces are marked with a dot on one end. Do the dots go in
the
same direction or in the opposite direction.

Desperate in LA

Generally speaking, dots indicate phase orientation; or in your case
magnetic orientation. As a WAG (wild assed guess) I'd say the dots must go
in the same direction. Since the adhesive is loose, why not try placing the
dots in both directions as a test?

Bob Swinney

Hi Bob

Its hard to "try" since the motor won't run with a loose
pole piece. It must be glued in place. I would guess that the dots
would go on opposite ends since you want the poles to be additive (N
to S, N to S) and all the poles would be made in a seperate process
and all marked the same. The installer would select the correct
direction.

I only get one try and I would like to not screw it up. Ceramic
magnet pole pieces crack real easy.

Eric

eeeeees wrote:
Hi Bob

Its hard to "try" since the motor won't run with a loose
pole piece. It must be glued in place. I would guess that the dots
would go on opposite ends since you want the poles to be additive (N
to S, N to S) and all the poles would be made in a seperate process
and all marked the same. The installer would select the correct
direction.

I only get one try and I would like to not screw it up. Ceramic
magnet pole pieces crack real easy.

Well, then, look really carefully at the glue pattern on the piece that came
out, and at the glue pattern in the socket, and see which way it went in. Might
need strong light and 10X magnification, but maybe you'll get lucky and can
figure it out. The other night I had to figure out which way two wires went into
an auxiliary power connector on my BMW motorcycle, figured if I hooked them up
backwards I might fry hundreds of dollars worth of German electronics,
absolutely no reference material anywhere, looked real carefully, saw something,
put it in consistent with what I resolved optically, and it worked. Whew.

GWE

eeeeees wrote:
I would like to repair a 12 VDC PM field motor which has one field
piece
loose. The adhesive yielded and one pole fell off. In the process of
cleaning off the old adhesive I lost track of the correct orientation
of the
loose field piece. It can go into the motor frame in either of two
ways. Both of
the field pieces are marked with a dot on one end. Do the dots go in
the
same direction or in the opposite direction.

Desperate in LA


Think about a simple two pole electromagnet field motor with a single
winding on the crosspiece of a "U" shaped magnetic structure, so the
ends of the "U" form the two poles. With DC applied to the field, one
pole will be north and the other south.

So, orient your loose magnet so that it is trying to pull toward the
other pole piece, not push away from it.

HTH,

Jeff

--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"Truth exists; only falsehood has to be invented."

I may be mistaken but I do not think that you can change the polarization by
rotating the magnet. I think the poles are at the faces of the magnet. The
concave side would be one pole and the convex side the other. Checking the
glue pattern is the best way to know which way it was installed. Clean it
good, use a good epoxy and clamp it good while hardening. I have repaired
automobile window and seat motors this way. Be sure you have the frame and
rotor well under control when reassembling or you may damage something when
the rotor is suddenly pulled in.

Don Young
"eeeeees" wrote in message
m...
Hi Bob

Its hard to "try" since the motor won't run with a loose
pole piece. It must be glued in place. I would guess that the dots
would go on opposite ends since you want the poles to be additive (N
to S, N to S) and all the poles would be made in a seperate process
and all marked the same. The installer would select the correct
direction.

I only get one try and I would like to not screw it up. Ceramic
magnet pole pieces crack real easy.

Eric

On Fri, 10 Feb 2006 18:26:09 -0500, Jeff Wisnia
wrote:

eeeeees wrote:
I would like to repair a 12 VDC PM field motor which has one field
piece
loose. The adhesive yielded and one pole fell off. In the process of
cleaning off the old adhesive I lost track of the correct orientation
of the
loose field piece. It can go into the motor frame in either of two
ways. Both of
the field pieces are marked with a dot on one end. Do the dots go in
the
same direction or in the opposite direction.

Desperate in LA


Think about a simple two pole electromagnet field motor with a single
winding on the crosspiece of a "U" shaped magnetic structure, so the
ends of the "U" form the two poles. With DC applied to the field, one
pole will be north and the other south.

So, orient your loose magnet so that it is trying to pull toward the
other pole piece, not push away from it.

HTH,

Right! And cover the other magnet with a rag or piece of wood. If
that loose magnet gets away from you and crashes into the other one,
you're out of luck.

Jeff

On Thu, 09 Feb 2006 08:01:57 GMT, lid (eeeeees)
wrote:

I would like to repair a 12 VDC PM field motor which has one field
piece
loose. The adhesive yielded and one pole fell off. In the process of
cleaning off the old adhesive I lost track of the correct orientation
of the
loose field piece. It can go into the motor frame in either of two
ways. Both of
the field pieces are marked with a dot on one end. Do the dots go in
the
same direction or in the opposite direction.

Desperate in LA

If the magnets are simple 'C' shaped items it doesn't matter
which way round they are installed.

Unless the magnets are mechanically assymmetric the ONLY thing
that matters is that the magnets are radially magnetised with one
magnet with an inner North pole and the other with an inner South
pole.

Jim