RE: (ET) E-20 rebuild report

["Elie, Larry (L.D.)" <lelie ford com>]

-----Original Message-----
From: Christopher Zach [mailto:czach computer org]
Sent: Saturday, January 26, 2002 2:34 PM
To: Elec-trak
Subject: (ET) E-20 rebuild report

"snips"

Thoughts:

The mower motors are drop-dead simple. If they don't run, and they turn,
there are really only two possibilities:

1) The brushes are either stuck or burned out
2) The armature is burned out.

Given the size of the armature wires, I think it would take a lot for #2 to
happen. Thus I'd be willing to bet that most motor problems might be
traceable to a stuck brush. It's possible that one could wear the brushes
down, but it doesn't look likely.
"


Someone else answered the rest, I'll go for these two.

Yes, the brushes can get stuck.  Yes, you can free them.  No, I've never 
seen an armature burned BUT I have seen;

Broken magnets (I have 3 shells with broken magnets sitting in the barn) 
and Bill gets $90 I think for new magnets.  Often it is from taking them 
apart wrong, but I have had some break on their own.  I find enough junked 
machines to always rebuild with a good shell.

Bent shaft.  The motor was 'adapted' by GE with second shaft to get the 
height of the blade right.  Hit something heavy enough and the shaft 
bends.  This includes a loose baffle.  Lots of loose baffles.

Thermal interlock rivet gets loose; results in poor thermal contact, wires 
melt.  In heavy grass the interlock WILL trip, especially if the battery 
is low or the blades are dull.

Cracked mounting flange.  Lots of these.  If you have at least 2 good 
ears, you can have a shop make a large ring or washer with four holes in 
thin steel or aluminum, and put that over the flange.  I also did this 
once with a thicker (3/4") aluminum ring on the center motor to damp a 
vibration in a deck.  It can break up a 'beat' frequency between the 3 
motors.  The deck floats; it can get vibrating pretty easy.  If you don't 
have a problem, ignore that.

Leaks.  Water gets in.  Clean and dry.  Connections all get bad.  I have 
seen motors (the small diameter with the dome top) get so rusted that I 
couldn't get the tops off, even in a degreaser.

Loose bolt on blade.  Spins, but gets REAL hot when you get to the grass.

Yes, I test the motors on 12V just fine.  Actually, you may hear a bad 
bearing or bent shaft or blade BETTER at 12V; at 39V you may be above that 
harmonic.  Anyway, a bad bearing has a low pitched rumble.  Another test 
is run all 3 on 12V (you need about 10A) and see which one comes up to 
speed last.  When you drop to 0V, that one will often stop first.  The 
bearing may be bad.  If you try this off the tractor, the blade brake 
stops the blades too fast.

BTW, the bearings are a standard series.  I get sealed ones from Motion 
Industries (used to be Detroit Ball Bearing) that fit and have a better 
seal than GE used.  I lost the part number, but any good bearing supplier 
can help.  I have never had a replaced bearing fail in 6+ years.


Larry Elie