(ET) Motor rebuilding and ground faults.

[Chris Zach <cz alembic crystel com>]

With the leaves mostly out of the way and with the belts slipping on my 
E20 going up hills with the trailer I decided it was time to drop the 
motor and do a bit of refreshing along with replacing the belts.

Took the motor apart and found that one of the electricity carrying 
studs had broken when I tried to remove the bolt near the motor. Bolts 
were fairly corroded, so it was the usual mess. On the positive side, 
the screws on the back did come out with a lot of pb-blaster and a very 
good flat-head screwdriver, so I was able to open the back of the motor.

Cleaned out all the gunk in there and started working on the other 
parts. Replaced the back bearing after determining the front one was 
more than fine enough, then saw that the brushes were worn almost all 
the way down. Ordered some parts but it's going to take a week so in the 
meantime I looked at the hulk of my E15....

It needs to be fixed up and I never replaced the motor bearings. So into 
the shed it went to have the studs swapped into the E20 motor along with 
the brushes. I noticed on the E15 there are only two screws that hold 
the brush assembly to the back of the motor while on the E20 there are 
four. Also the motor is a bit shorter but still has a double pulley.

The bearings were toast so I pulled the front pulley and started on the 
armature. One sad bit: I could not get the puller between the motor 
housing and the pulley so I had to try pulling on the flanges. Cracked 
the lower flange but got the pulley off, I guess it's good the E15 is 
supposed to only have one belt. I guess if I want to run two I can file 
down the edges of the cracks in the flange and just deal.

Both bearings replaced I put the E20 motor back together. Unfortunately 
with it closed up there is *still* a ground fault somewhere in the 
motor. Not sure if it is in the armature, but the fault appears at all 
positions of the armature so I don't think so. It's possible something 
is bad in the brush area but it has the plastic shield in there so that 
shouldn't be it. Which could leave the compensating series field....

If that turns out to be the problem what would be the impact of 
disabling it? I doubt anyone makes field coils for these motors and I 
don't think I could easily fix it. If I just wire the armature to the 
bolts what would be the issue (other than losing field current being 
very very bad for the motor)?

C