Strange electric motor problem...
 

A friend had a strange problem today and it has me stumped... He was
driving a XXX buggy w/ Team Orion 17x2 motor. No problems whatsoever,
then it just stopped. After checking for rocks or binding in the drivetrain, he
went to the pits and removed the motor from the buggy. The motor was
'locked up' and could not be turned by hand (didn't try using pliers, etc...).

The armature & brushes were removed to check for any debris but it was
clear... Looking closely at the armature, it appears it has rubbed the magnets
inside the can at some point??? I'm wondering if it is in contact at all times
and is causing the motor to be locked up??? But here's a strange bit of info:
As you install the endbell, you can turn the motor by hand until the 2 screws
are nearly tight... If I hadn't seen the motor running perfectly, I'd think the
screws were too long and hitting the armature...
HELP?!

Thanks,
Scott

Could have been debris in there before you took it apart. A small rock getting in there can make markings on the armature. Shorten the screws and give it another go.

I'm going with the screw being too long, but odd that it worked for a while.
Check how far the screw goes through the end bell, then measure how far from the edge of the can to the ring when it's seated. The screw should only go through the other side of the ring by 1 or 2 mm.
You could add some washers to the screws if you don't have shorter ones.

Just an update for anyone interested...

1) The screws were not causing a problem. They could be 1 inch
long and not interfere. I don't know how/why tightening them affected
the armature/magnet, though.

2) The problem was caused by one of the magnets seperating from the can.
I guess the epoxy failed and one end of the magnet was making full contact
with the armature. I'm not sure if how to fix it properly or if it is worth
fixing, but it's 'rigged' right now. ;)

To the users above: Thanks for taking the time to reply...


Scott