Re: (ET) Brush issue...

["RJ Kanary" <rjkanary nauticom net>]

That can be a concern, as the brushes get shorter.As the brush shortens, 
the
spring tension that keeps it against the commutator is reduced. This, in
conjunction with the shorter brush more readily transferring heat to the
brush holder, makes sticking a possibility. Add to this, increased armature
run out, caused by fair wear & tear, of both the commutator bars, and the
armature bearings, and the recipe is complete. This input was gleaned for 
my
Dad's many years of maintaining DC operated overhead cranes, and small
Diesel / Electric switch engines.


RJ Kanary
Member TRNi  Since 1998
ASE® Certified Master Auto Technician

rjkanary nauticom net

----- Original Message -----
From: "Christopher Meier" <mr23 mn rr com>
To: <elec-trak cosmos phy tufts edu>
Sent: Tuesday, May 28, 2002 8:49 PM
Subject: Re: (ET) Brush issue...


> Could the brush be expanding just a hair due to heating from the motor
> operation?
>
> ----- Original Message -----
> From: "Christopher Zach" <czach computer org>
> To: "Elie, Larry (L.D.)" <lelie ford com>;
<elec-trak cosmos phy tufts edu>
> Sent: Tuesday, May 28, 2002 12:52 PM
> Subject: Re: (ET) Brush issue...
>
>
> > Personally, I had the same problem with one of my small diameter 
> > motors.
> The
> > brush appeared to be "hung up" on the metal brush holder (stamped 
> > metal)
> >
> > In addition to tapping the brush, I also went and slightly widened the
> > holder and flared the edges a *tiny* bit. Think very small changes.
> >
> > My guess is the brush holder is a wee bit tight, and as a result 
> > natural
> > motor vibrations will cause the brush to migrate away from the 
> > armature.
> > Kind of like it ratcheting out. Opening up the holder a smidgen 
> > prevents
> it
> > from ratcheting.
> >
> > HTH
> > Chris
> >
> > ----- Original Message -----
> > From: "Elie, Larry (L.D.)" <lelie ford com>
> > To: <elec-trak cosmos phy tufts edu>
> > Sent: Tuesday, May 28, 2002 1:20 PM
> > Subject: (ET) Brush issue...
> >
> >
> > > You would think I had seen it all.  Nope.
> > >
> > > One of my large diameter deck motors quit spinning.  I poped the
cover,
> > > unbolted the casting that holds the brushes and found a brush not
> > touching.
> > > The brush itself was not badly worn, and the springs seemed good.  A
tap
> > > poped the brush out where it belonged, and I re-assembled.  It mowed
> fine,
> > > for a few hours, then I had a repeat.  It isn't working now, and I'm
not
> > > sure what the 'fix' is.  The graphite of the brush should be fine for
a
> > > lubricant, and everything seems to be sliding properly.  Any
> suggestions?
> > >
> > > Larry Elie
> > >
> >
>
>