Oppie wrote:

"nesesu" wrote in message
...
On Feb 9, 7:57 pm, DaveC wrote:

After you turned the commutator, did you undercut the mica between the
commutator segments? It is critical that the insulation be below the
surface of the copper to ensure good contact between the brushes and
the copper. If there is still sufficient undercutting [you only
skimmed the surface of the comm] then be sure that there is no copper
shorting between commutator bars. The copper often 'smears' a bit when
being turned and will bridge the gaps here and there. A "pole growler"
will show up any such shorts.

Neil S.


Been there, did that...
My wife's grandmother was the only person I've ever known that wore out an
old Electrolux vacuum cleaner. When the motor was disassembled, there was a
noticeable groove in the commutator. Put it on a lathe and turned it down in
very small steps, finishing off with very fine grit on a wet cloth to smooth
to a near mirror finish. Complete by removing any copper flash that wound up
in the gaps between commutators.


I used to turn down commutators on lots of vacuum cleaner motors
without taking them apart. I would run them on a variable DC supply and
use a hard ink eraser, with it running. Some were so bad that I had to
hit the worst spots with emery paper, but I didn't have a lathe and it
worked.


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