Is it just one of those things but I have 2 Bachmann 9 F's, Evening Star & a Modelzone weathered version. I have used Peco code 75 track and whilst the black 9F runs very well Evening Star quite oftens derails at points. Is there anything I can do ?
*** you need to check the back-to-back of all wheels - Bachmann can be a little careless with them - for example my own 9f ran fine out of the box through my very fine scale points driving-wheel wise (which surprised me as I didn;t expect it to!) but its tender wheels needed moving out on their axles almost a full millimetre.
Most often the offending wheels are too close together. Try setting all pony and tender wheels to 14.5mm exactly... if its the driving wheels its a bit harder to do, but if you take the drivers out, and properly support the wheel, you can gently tap them out to the correct spacing if very careful.
Since you have the pair, and the black one runs successfully, with both locos inverted sight along the wheel running surfaces on both, and see if the Evening Star chassis has any visible discrepancies from the good runner. Measure the back to back on each of the wheels on the good loco, compare to what you find on Evening Star's chassis. Richard's suspicion of one or more tight back-to-backs is likely correct, best to only adjust those that really need it, which you can help ensure by using the good runner as a benchmark.
I too had a similar problem with my Bachmann 9F with constant de railing, I bought a new pony truck and wheels and spent hours watching it to see why it derailed.
Then I found the problem, the sand pipes were fouling on the wheel. A quick tweak with the pliers to remove the sandpipes and it goes over anything now.
Its worth checking if you have the sand pipes fitted.
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