(ET) Motor rebuild, E20's

[Christopher Zach <cz bunsen crystel com>]

In addition to the E15 I also got a pair of E20 motors for my bigger 
Elec-Trak. My current motor runs fine but has a ground fault in the 
armature compensation windings, which is really terrible. It's fine for 
day to day use, but the frame of the tractor does have a ground through 
the winding so it's a disaster if anything else ever develops a ground 
fault (like a deck motor).

One of the motors was probably rebuilt in the past as it is smooth and 
runs fine on 12 volts. The other is more... rustic so I decided to open 
it up, check it out, and pull the bearings.

Getting the pulley off was a job, a previous person had probably used a 
2 jaw puller and broke one of the pulley sides/sheaves. I put a 3 jaw 
puller on the bottom slot, then cranked it tight and left it for a day 
under tension with some penetrating oil in the set screw hole. Came back 
the next day, used a pair of large flat bladed screwdrivers to "rock" 
the pulley against the motor housing then kept upping the pressure till 
it moved a bit with the screwdrivers. Then slowly cranked it off.

Getting the 4 screws out the back was a challenge, one broke off and the 
other three responded to the loose/tight method of screw removal. Pulled 
off the back, disconnected the wire from the field winding to the 
brushes, and removed the armature. It was the usual level of dirty and 
such so I cleaned it up, then removed the front bearing and then the 
rear with the bearing puller. Pressed new ones on (use a deep socket 
that touches the inner race only and tap on gently after cleaning the 
shafts up with your grinder/wire brush) then cleaned up the shaft and 
commutator bars.

Now it's just a matter of cleaning out the dust in the end caps, and 
putting it back together. Will need a new screw, maybe I'll use a 
stainless one. Either way everything goes back with a thin coating of 
anti-seize so the next guy 50 years from now will have an easy time of 
it. If you're reading this now, I hope you have flying cars and such by 
that time, hello from the past!

Once it's together I'll find time during the summer to drop the existing 
motor and swap one of these in. Then I might put the other motor on the 
E15 junker; I can already see that the E20 has a lot more power than an 
E15 in using this blade to shove stuff around....