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I have 2 #290 locomotives with tenders. I have completely serviced reverse units and serviced the engine removing the armature etc clean and lube.   One engine runs fast in reverse and forward the other only fast in reverse and slow in forward. Same issue with both tenders with reversing units.   Any ideas would be helpful.   Roy O

Original Post

It's known as early postwar AF steam "syndrome".  Early in that the armature has flat commutators not the latter barrel-shaped ones.  Assuming all other conditions* are proper, clean, and in good tune, then typically the only lasting "cures" are to 1) re-face the flat comms of the armature on a small lathe,  2) re-face the flat comms of the armature gently and methodically in a drill press using 100 -->1100 grit sand/emory paper (basically #1 w/o a lathe), or 3) replace the armature with one less worn.   Other measures like doubling up brush springs, messing with combinations of fore and aft thrust washers beyond those that ought to be in there can make a difference, but not usually for long.  At least that was my experience with dozens (possibly hundreds) of them over 20+ years of repairs.

*fore and aft armature bearings, axle holes/bearings in the chassis, drive gear teeth and centering, worm gear, brushes, brush springs, brush tubes, brush bracket, fore/aft thrust washer(s), quartering and condition of all 3-piece driver wheels, electrical connections from railheads to motor, etc.   

Last edited by Sgaugian
traindavid posted:

I have often wondered if it is primarily wear on the axle drive gear. Thought of taking one apart and turning it around to see it that makes a difference.

I think this would be a fairly difficult modification.  I'm pretty sure that one of the driving wheels would have to be pressed back on with different quartering.  I'm willing to bet that two times out of three the problem is wear in the rear axle bushing(s).

Thanks all.  Had a spare chassis. my axle felt good. I removed the bearing and armature, cleaned all items and reassembled and all worked fine. I did not find anything different. End play and washer was intact in both, bearing did not feel loose. Right now I don't care as it works OK. Thanks for all the ideas and help. Yes I did use my old chassis and wheels also brush plate.   Roy O.  Nice to have a junk box except when you can not find what you are looking  for and know you have it. LOL

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