I have a Bachmann B1 that has developed a 'wiggle'. I've swapped the chassis with an LNER liveried one I don't run on the layout and it is fine, but any suggestions as to a cure - it it just wear and tear? Would replacing the axles help?
I've also had instance of the plastic wheel centres distorting and fouling the coupling rods. That loco also got failed valve gear and was withdrawn for spares.
The description of the problem suggests to me this might be a split chassis mechanism B1? (Simple diagnostic, won't have a DCC decoder socket or NEM coupler pockets.)
If that is the case, that's what happens with this obsolete construction, the driven wheelsets fall apart as the centre plastic muff
in the wheelset construction becomes loose: can be glued or replaced by muff
s sold by Peter's Spares. (You clearly have already experienced the distorting cosmetic plastic inserts in the driving wheel faces, that can produce this 'wiggle' effect too.)
But if it is the current model, then most likely to be some part of the external rods fouling, or a bent coupling rod on one crankpin of the wheelset that's 'wiggling'. Needs careful inspection, connecting rod fouling on the leading crankpin is a key first place to look because a modern motor can seriously bend a snagged coupling rod, but there's usually an audible click and you don't mention that. Can also be a little piece of foreign material concealed in the cylinder limiting the travel of the piston rod, or a wiper out of place snagging on a wheelback, or a piece of foreign material lodged on a wiper or underframe detail, doing the same. Or if the loco has had a heavy accident, a wheel in the wiggling wheelset no longer true on the axle.