Problem with Motor in Intermountain F unit.

[Doug G.]

That's OK,Max. I kind of figured it was that, being my mention of brushes was toward the end of my post. And if bill has a three-sided coin...



Doug

[randgust]

FWIW I'll vote brush wear/seating/position.

I've got one of those F's, but I haven't torn it apart to look at the motor and brushes, so I don't know if you can reverse and reset the brushes or not.

My only point of reference is that happened all the time on old Trix units as they had very sloppy brush holders; brush alignment and drag would change depending on the rotation direction of the motor, and it really messed up MU'ing.   It was the N scale equivalent of rotating tires.

[skytop35]

Not knowing my way around motors like everyone helping out here. I failed to get the brushes out. I tried prying the brass cap off but that didn't seem to help although it moved a little. However while doing this, I noticed black particles on my fingers. I tried the battery again and it now seems to be working equally well in both directions. I didn't have time to put it back in the engine to test as that will have to wait until after I get back from TrainFest. Thanks all for the help so far.

[mmagliaro]

Not knowing my way around motors like everyone helping out here. I failed to get the brushes out. I tried prying the brass cap off but that didn't seem to help although it moved a little. However while doing this, I noticed black particles on my fingers. I tried the battery again and it now seems to be working equally well in both directions. I didn't have time to put it back in the engine to test as that will have to wait until after I get back from TrainFest. Thanks all for the help so far.

That REALLY points toward brushes now.
By prying on that cap, you probably jostled the brush under it.  It may have been stuck in its cavity, so it wasn't smoothly riding up and down in there under the spring pressure, against the commutator.  If it was sticking, that could definitely cause
bad behavior in only one direction.   A brush really has to have a very smooth, curved surface that lays exactly mated up against that round commutator, and it has to be able to maintain constant, but not to hard, pressure.
Any sticking, or a broken chip at the edge of the brush, etc, can make them act very badly.

And as this is an old motor, the brush and its spring might be getting near the end of its life.

[MK]

How about blasting it with a cleaner like DeOxit to get the gunk out and lubricate everything?

[peteski]

I agree.  A problem with brushes could have symptoms akin to a shifted commutator - changes the angle/timing of the power delivery to the commutator, thus to the windings.  I just  have never seen this happen to one of those standard Kato-type motors since they usually have well-designed tight brush holders).  What Bill describes sounds like a carbon powder dust buildup. That happens during normal operation as the brushes wear down. If there is some oil around the area (like there always is in factory-overlubricated models) the dust clumps and becomes a greasy conductive ball. If that ball is in contact with the commutator on one side of the brush, that will affect the power delivery to the commutator.

[Doug G.]

Yeah, too much oil in that area is bad.



Doug