A couple things come to mind:
Motor out of alignment
Flanges making contact with the ties
Something on the wheel itself
I'd start diagnostics by checking the wheels. If you hold a piece of
track to the wheels and take a good look (usually I do this with the
locomotive upside down for better light), that will tell you if the
flanges might be rubbing. Be sure to use the same stuff as what's
I'd then check the wheels with the NMRA standards gauge. Just follow
the instructions that came with the gauge for doing that.
If those items don't solve your problem, take a look at the motor and
mechanism. Most (decent) locomotives use a ball-and-socket connection
to power all the wheels. If the motor's not aligned properly or loose,
this can cause the locomotive to sway. I found this out on a recent DCC
decoder installation. Once I reseated the motor properly, the engine
Drivers: The big wheels on steam locomotives; Also the middle numbers
when talking about wheel arrangements such as 2-8-2. Quarter: The side
rod on one side is 90 degrees out of alignment with the other. So, if
the left side is at the top center, the right side is halfway down.
Marching to the beat of a different drum is great... unless you're in
Does it have traction tires (sort of like small rubber bands around
some of the wheels)?
I once had an old Tyco diesel that would waddle because the traction
tires seemed to be nothing more than just that, cheap little rubber bands.
Because those "traction tires" were not of consistent thickness or
width, they would be thicker and thinner at various points around the
wheel. That in turn caused the loco to wobble at regular intervals as
it went down the track.
The cure was to appoint it Shelf Queen status...
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