(ET) Chris's motor and rebuild advice

["Steven Naugler" <snaugler earthlink net>]

Chris,
    Larry Elie is right, do be careful when repairing your motors.  However
I've rebuilt 10 motors so far without any problem.  They were:
1.  6 small mower deck motors (permag).  3 needed just bearings, 3 needed
brushes too.
2.  2 E15 traction motors (shunt field).  2 needed just bearings, 1 needed
brushes too.
(The brush failures were due to water getting in the motors and corroding
the copper wire to the brushes.)
3.  1 snow blower motor (shunt or series field, I don't remember which).
Needed just bearings.
4.  1 leaf/grass vacuum blower (permag).  Needed just bearings.
    I've learned that the GE motors are overbuilt.  None of the motors had
any significant commutator wear.  The brushes would have all had more than
50% life if it weren't for the motors that had the water problem.  Even
then, they were otherwise undamaged.

    Here are some rules I now use when rebuilding the GE motors.
Professional motor shop people most likely will have somewhat different
recommendations, but these worked for me.
0.  Most important.  Make a sketch of how the motors come apart.  Shims and
washers need to be in the right place.
1.  Use only emery cloth to polish the commutators.  In one case I used
green Scotchbrite followed by emery cloth.  Green Scotchbrite alone is too
aggressive.
2.  Use only compressed air to clean the rotors.
3.  You can bead blast  the cases if you want to repaint.  Sandblasting
could be used if you are very careful.  Do not blast the inside of a case
with a wound field.  Be extra careful about removing all blast media from a
field winding.  In many cases it might be best to not blast a case with a
wound field, but I have gotten away with it so far.
4.  Replace brushes if they don't have at least 1/2 their length still in
the brush holder.  I usually replace them even if they have 70% life left
because replacing brushes is relatively cheap.
5.  Be careful of a permag motor case.  Also, removing or replacing a rotor
in a permag case is tricky because no matter what, the magnets seem to 
fight
you.  You can dent or damage the insulation of some of the rotor wiring.  
If
you break a big magnet chip off, you should replace the case because you
have permanently weakened the field strength.  If you break a small chip
off, the case is usually still good to use, but if you lose the chip in the
motor it can jam the motor later and cause much more major damage.
6.  Use 320 grit or finer (400 is safer) if you need to remove corrosion
from the rotor shaft or in the end caps where the bearings fit.  Remove all
abrasive dust when through.
7.  Replace all shielded bearings with dual seal bearings, even if they 
seem
good.  Sealed bearings retain grease better.  If you have a motor apart,
replace at least the motor shaft end bearing.  That one has the highest
loads.  I've always replaced both bearings.
8.  Use a hydraulic press and split bearing pullers to remove all old
bearings.  Other tools can damage the shaft.
9.  When pressing on a new bearing, only push on the inner race, and try to
use a hydraulic press.  Pushing on the outer race will cause you to dent 
the
races greatly reducing their lifetimes.  Hammering a bearing, even on the
inner race, can sometimes also dent the races.
10.  If for some reason you start to install a bearing and then have to
remove it, be warned.  Unless you remove by only putting force on the inner
race, you have a large chance of damaging an otherwise new bearing.  If you
are not sure, discard the now questionable new bearing and get another.  
You
don't want to do another rebuild after only one year.
11.  Use your sketch (see step 0) to reassemble things in the right order.
I use a light grease film in the case ends where the bearing go.  Use too
much and it can migrate to places you don't want grease.
12.  Test your motor, preferably before reassembly into the tractor or
accessory.  Careful, it will want to spin away from you if not clamped to
something.  (I know.)
    I have been told that you should test the armature with a growler, but 
I
don't have one.  (If I find a good deal at an auction I'll buy it.)  What I
have found in my limited experience is that is the motor worked before it
came apart, it will work proper after proper reassembly.  If you don't have
all the electrical test equipment AND the motor didn't work before
disassembly, it may be worth having a motor shop check it out before doing
much work to it.  You be the judge of whether it costs more just install 
the
new bearings and brushes or slipping the motor shop guy some beer money.

Chris, hope this helps you.

Steve Naugler