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Hi all,

I just acquired a Lionel PW 628 44 tonner.  I tore the whole thing down, degreased, cleaned, etc.

Having a weird problem and I would like to see a motor parts diagram for that series of engines if anyone has one.  My repair manual does not have a breakdown listed.

When moving the wheels forward (engine moving in reverse) manually they spin smoothly with slight force as you would expect.  When moving the wheels in reverse (engine moving forward) it seems to sort of bind, but more of a subtle drag.

It runs fine in reverse.  It will also sometimes run fine forward.  When it doesn't it runs slower.  Give it more power and it runs fine.  It is like you need to give it enough power to overcome the drag, but not always.  Sometimes it runs fine forward and slow.

With the armature out the gears spin freely in either direction.  Gears look fine as well as the armature and it's worm gear.

The only thing I seem to notice is that the armature rises and lowers more than seems normal to me.  I would say 2-3mm.  When in reverse it is being pulled down towards the ball bearing and runs fine.  When running forward it seems to lift excessively; at least to me.  I wonder if that is causing a drag between the armature worm gear and the "main gear" it is engaging.

There is a plastic thrust washer on the top spindle of the armature and the ball bearing on the bottom in the plastic piece.

I have torn down and rebuilt every engine I own and I have never run into this before.  In my opinion it is definitely a mechanical issue.

If anyone has the motor diagram or any ideas I would really appreciate it!  I will be playing with/working on my trains a lot tomorrow and hope to be able to figure this out.  It seems like it must be something very simple.

Last edited by TrainManMike
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That was a problematic design by Lionel.  There should be a nylon and steel washer between the commutator and brush plate to limit vertical movement.  But the main problem is shifting of the bottom bearing plate in the frame that causes the armature to be drawn into the field when going in one direction that causes it to bind.  Lionel’s fix was to stake the sides of the frame to lock the bearing plate in place.  I’ve had limited success with this fix.  It’s a trial and error to find the best location of bearing plate.  

Lionel improved this design by eliminating the bottom bearing plate and installing the motor bearing in the upper frame.

@Jon G posted:

That was a problematic design by Lionel.  There should be a nylon and steel washer between the commutator and brush plate to limit vertical movement.  But the main problem is shifting of the bottom bearing plate in the frame that causes the armature to be drawn into the field when going in one direction that causes it to bind.  Lionel’s fix was to stake the sides of the frame to lock the bearing plate in place.  I’ve had limited success with this fix.  It’s a trial and error to find the best location of bearing plate.  

Lionel improved this design by eliminating the bottom bearing plate and installing the motor bearing in the upper frame.

There is no steel washer, so I will see if I can find one in my motor parts.

I will also check for movement in the bottom plastic plate.

Thanks!

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