Re: (ET) Mower motor stuff

["The Nauglers" <snaugler earthlink net>]

Chris

It sounds like one of the magnets came unglued from your motor shell.  I
have had that happen on two DC motors in the past, although neither were 
for
the Elec-Trak.  One had a broken magnet which I fixed by gluing the magnet
pieces as close together as possible.

I was able to repair both of those motors with epoxy.  I used the normal
cure high strength like you can find in Home Depot, but do not use the 5
minute stuff.  It cures faster at the expense of lower strength.

I VERY, VERY thoroughly cleaned the motor shell and the magnet with 
solvent,
smeared the epoxy on, and placed the magnet back in its original postion.
This may take some doing because sometimes the magnets will fight you.  You
need enough epoxy to leave no gaps between the magnet and the shell, but as
little as possible so that the magnet is as close to the shell as possible.

You will want to clamp the magnets in position for a two reasons.

1.  The first is that once glued you can't get the magnet off.  You need to
get the right position the first time.

2.  The second is that you actually want extra epoxy to be squeezed out.  
It
is important that the magnets are as close to the shell as possible.  Use a
spring clamp so that clamping force is maintained as the magnets move 
closer
to the shell.

Now wait for the epoxy to cure hard, at least overnight.  The clamps can
come off and they stay off.

Think you're done?  Nope.  This epoxy will be highly stressed, so I
recommend a post cure.  What I did was place the shell on one of those
electric oil filled radiators set on low, covered the shell with a box
making a mini oven, and let it stay there for 24 hours.  The shell reached
about 150 to 160 degrees and stayed there for the entire time.

You can also use a kitchen oven if your spouse or significant other will 
let
you.  (Mine didn't, hence the radiator style heater.)  Use two cookie 
trays,
one on the lower rack, and one on the upper rack,  Place the motor shell on
the upper tray.  The lower tray protects the motor shell from radiant heat
which could get the shell too hot.  Set the oven to warm, and "bake" for 
12-
24 hours.

Bill Gunn had bad luck with fixing magnets, so he wouldn't do it at all
after a few failed attempts.  But in Bill's case a 25% failure rate would
have been intolerable.  In our cases, if the option is trashing the motor
shell, I'd go for it.

Steve Naugler
snaugler earthlink net

----- Original Message ----- 
From: "Chris Zach" <czach computer org>
To: "Elec-trak list" <elec-trak cosmos phy tufts edu>
Sent: Friday, June 11, 2004 5:30 PM
Subject: (ET) Mower motor stuff


> Since I couldn't get my mower motor flange off, I figured I'd try and
> clean it out. A bit of brake cleaner rinsing got a lot of gunk out of
> the bottom bearing and now it spins more freely.
>
> Problem is this: Still doesn't spin when put together. In fact it feels
> as if the armature is rubbing against the magnets for some reason. There
> is no side-to-side play, it's just rubbing and I think this is part of
> the cause of the extreme friction and the "chug chug" operation under 12
> volts (with insane current draws)
>
> What happened with these motors? They sat all winter; that's the only
> thing I can think of that happened.
>
> Chris
>
>
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