Armature burning in AC motor

[klem kedidelhopper]

On Apr 26, 5:04 pm, "Michael A. Terrell" <mike.terr...@earthlink.net>
wrote:

Rheilly Phoull wrote:

There used to be a specific abrasive 'stone' used for that process and
it was very effective, especially where a high power tool had to be
ready for use immediately (seating the brushes that is).

   I heard about them about 30 years ago, but cound never find anyone
with them in stock, so I came up with the other method.  I would get
catalogs of motor parts that listed them, but they were always on
backorder.

--
You can't have a sense of humor, if you have no sense.

I think your idea is very interesting Michael and it certainly is
worth a try but I guess I'm a bit skeptical though. I have rebuilt
many motors myself, (probably not hundreds though) and I've never run
into a brush seating problem. That doesn't say that it doesn't exist.
Historically I've found that if the commutator was good the new
brushes would contour themselves. I did many Electrolux canister
motors like this in fact without a problem. Electrolux made a great
motor. You could wear those commutators down to almost a valley and
even without turning them a set of new brushes would make them run
well again. In fact I have an old cardboard box labeled "National
Brush Assortment". This is slightly larger than a cigar box but not as
deep with compartments in it. It contains many different sizes of
carbon brushes. This was part of a load of stuff I got when I was a
kid from a hardware store that was going out of business. It's
probably from the 40's or 50's. None of these brushes were contoured
and I've used them in almost everything that's walked in here needing
brushes over the years without any problems. The motor is presently in
my son's house and he's on vacation for the next two weeks so I won't
be able to revisit this project until then. But I will post my results
after. Thanks everyone for your input. Lenny

 

[klem kedidelhopper]

On Apr 26, 5:04 pm, "Michael A. Terrell" <mike.terr...@earthlink.net>
wrote:

Rheilly Phoull wrote:

There used to be a specific abrasive 'stone' used for that process and
it was very effective, especially where a high power tool had to be
ready for use immediately (seating the brushes that is).

   I heard about them about 30 years ago, but cound never find anyone
with them in stock, so I came up with the other method.  I would get
catalogs of motor parts that listed them, but they were always on
backorder.

--
You can't have a sense of humor, if you have no sense.

I just had another thought. I repaired many GM S1 alternators for
myself and friends over the years. Usually the problem was the diode
trio, the brushes or the internal regulator. We would get old
alternators from junk yards and scrounge them for parts. The case half
would separate and you had the front half with the rotor and pulley
attached. The bearing was rarely a problem and I couldn't remove them
or the pulley anyway. I would mount the front half on my bench so that
the belt from my bench grinder turned the pulley and rotor. If I
carefully held a file against the rotor as it was spinning I could
"turn" the commutator. This was by no means precision machining, but
it seemed to work every time. You can't do this to a modern GM
alternator anymore. The commutators on the new ones are about the size
of a dime. Lenny

 

[N_Cook]

klem kedidelhopper <captainvideo462009@gmail.com> wrote in message
news:8fe71aa9-295a-4939-a231-317aced22c4c@21g2000vbh.googlegroups.com...
On Apr 26, 5:04 pm, "Michael A. Terrell" <mike.terr...@earthlink.net>
wrote:

Rheilly Phoull wrote:

There used to be a specific abrasive 'stone' used for that process and
it was very effective, especially where a high power tool had to be
ready for use immediately (seating the brushes that is).

I heard about them about 30 years ago, but cound never find anyone
with them in stock, so I came up with the other method. I would get
catalogs of motor parts that listed them, but they were always on
backorder.

--
You can't have a sense of humor, if you have no sense.

I just had another thought. I repaired many GM S1 alternators for
myself and friends over the years. Usually the problem was the diode
trio, the brushes or the internal regulator. We would get old
alternators from junk yards and scrounge them for parts. The case half
would separate and you had the front half with the rotor and pulley
attached. The bearing was rarely a problem and I couldn't remove them
or the pulley anyway. I would mount the front half on my bench so that
the belt from my bench grinder turned the pulley and rotor. If I
carefully held a file against the rotor as it was spinning I could
"turn" the commutator. This was by no means precision machining, but
it seemed to work every time. You can't do this to a modern GM
alternator anymore. The commutators on the new ones are about the size
of a dime. Lenny

+++++

In the UK that stone was sold by Martindale and still do it seems
http://martindaleco.com/pdfs/Abrasives/Diamond_D_BrushSeaters.pdf
You just cut down a bit to matchstick size to chase any remnant sparking
(not fault overcurrent situation). I don't think its a pateneted formulation
just a specific mineral , IIRC a variety of tufa of volcanic origin?. White
and a bit gritty to the touch