I have two Atlas N locomotives, an SD-50 and an H15-44 and both have what appears to be gear lash. By gear lash I mean the drive-train seems to get a bad resonance going and this out of phase vibration both slows down the locos and makes more noise. It happens intermittently while running.
This lash happens mostly when load is “reversed”, that is when the loco is going down hill. It also happens when it is not pulling any load.
Has this problem been identified in locos in general and is there something I can do to fix it? I’ve put Atlas gear lube on the gears (truck gears and worm), bearing lube on the bearings and conducta on the brushes but it still happens. What else can I do?
Hello Eric, Sometimes the problem you describe can be reduced or eliminated by adding thrust washers on the worm shafts, between the ends of the worms and the shaft bearings. The idea is to keep the worm from being able to shift back and forth under pressure from the worm gear. Not being an N scaler myself, I’m not sure what kind of very small thrust washers are available. A thin bronze washer would be ideal, but nylon or Teflon washers would also be good. Good luck, Andy
I’m suspecting you have the excess axial play in the worm shaft(s), just like I described in the thread “finicky little loco”. It is probably one of the more common performance problems in locomotives. For proper performance, the worm has to be held in a very tight relationship to the worm gear. Slop in the bearings or gearbox can allow the worm shaft to slight forward or backward slightly under load, allowing the gear mesh to change from optimum. Of course, the gearbox could have the gears slightly off mesh from the get-go.
Another possibility is universals “catching” or slightly binding as they rotate. Manufacturing imperfections allow a rough surface on the universal to catch on its receiver.
The plastic gear (and sometimes metal ones, too) can have “flash” on the teeth. Carefully check under a magnifying glass and good light to make sure the teeth are uniform and properly shaped. Careful work with a file can usually fix any discrepancies.
I agree with Andy. Old HO open frame motors were notorious for this problem. Washers on the motor shaft were the only thing that I found that worked. Loosening up the lash between the worm and plastic drive gear might help too.
Thanks for all of your replies. I too thought some kind of washer may help. Does anyone know of a online source for washers (brass, teflon, plastic, steel) that may fit on an Atlas N Scale loco drivetrain shaft?
Thanks again, good to know I may be on the right track.
Another thought here. I had the same problem on an SW1 switch engine in HO though. Try running the locos minus the body shell. If you find them quiet this way, as I did, the noise was generated by the motor torque rocking the motor against the body. Mine would run quiet in one direct, but have your symptoms running in the opposite direction. I placed thin foam between the motor and body sides. Ken
That is cause by axle sloop going down grade as other stated a washer should fix the problem.
You see while the train is going down steep grade the cars are pushing the engine and causing the locomotive’s gears to misaligned due to the built in tolerance gear “play”…
With that said I never was to keen on the idea of adding the washer and removing the play in the gears unless the gear play is excessive.
I haven’t yet purchased washers and installed them but I intend to to see what effect it does have for my case.
I did notice though that the “gear lash” seems to be an issue with 3 out of my 4 (just starting out!) locomotives. As the season changes here in California the temperatures are dropping and for the last couple of weeks my unheated basement where I’m building my layout has been in the 50’s in the evening and on some days. Is it possible that the tempurature has just dropped enough to start making the lube stiffer and causing the problem? Any experience out there with low temps and “gear lash”?
I might try heating the engines with a hair dryer (I know, low heat and not close!) to see if that does anything. Thoughts?