It has been my experience the wheels are dirty. It jerks when it gets to dirtiest parts of the wheels.
Double up a paper towel and soak it in 90% alcohol. Put the paper towel across the tracks. Put one set of trucks on the paper towel and one set of trucks in contact with the rails.
Hold the locomotive and crank the transformer wide open and let her buck. Gently slide the locomotive back and forth with the trucks on the paper towel move the paper towel over and keep doing it until the black streaks on the paper towel go away.
Flip the locomotive and repeat. After you do both sets of trucks and there is very little black streaks on the paper towel the locomotive usually runs like a champ.
For a thorough cleaning I usually do this procedure in both directions. You would be surprised when you change directions how much more black crap you get on the paper towel.
Let me know how that works for you
Out of curiosity, was it the worm or was it the worm gear the worm is driving? Both are different gears. If I picture the drive, the worm drives a worm gear.
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
Problem solved. Cleaned magnets but found that one of the worm gears was slipping causing engine to skip/jump.
Atlas GP35 non-decoder model.
Installed TCS CN decoder and it ran great until I filed chassis screws from Atlas which I thought were brass -big goof as I should have checked them with a magnet.
Has anyone ever disassembled an Atlas motor? I can clean it up if I can take it apart. I suspect the flywheels and armature are heat pressed.
more info would help , like is it a can motor or open frame , who made it , what make of loco and type ?
Run with jerks? Hopefully it'll hang out with some really cool model railroaders instead.
Have you tried passing a magnet over/around the motor to try and extract any fillings? If you want to troubleshoot the "poor performance", remove the motor or disconnect the drive and apply power to the motor and see how it runs.
It might even be the driveshaft or other mechanisms causing the "jerkiness"
Terry
Inspired by Addiction
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If a loco motor comes in contact with some small iron filings, will it run with jerks? If it does have some filings, is it history or can it be rescued some way?