buzzing sound

Model Railroader General Discussion (Model Railroader)
1

hi guys

I bought a athearn gp-7 on sunday and Im starting to notice that it makes kind of a buzzing or a zzzzzzzzz sound when going around corners. i have taken the model apart a couple of times and I still can;t find the problem. any thoughts to what it could be.

thanks
jeremy

2

One possibility is that the motor is sitting incorrectly inside the shell, causing the flywheels to hit the inside of the shell as they turn. Run the locomotive without the shell, and if you do not hear the buzzing, make sure the motor is fully seated and sitting flat.

If you still hear the sound without the shell, inspect the drive shafts, and dissassemble the trucks and inspect the gears for any flaws or excess plastic.

Josh Ziegler
Spokane WA

3

I had this problem after repowering an Athearn recently. I was having vibration resonate from the shell, like a speaker. First do waht camodude suggested and run it without the shell. If it still makes the noise:

  1. Remove the trucks and check all the gears for flash or burrs. Do the same with the drive train. (this was one of two problems I found with mine, flash on the shafts were causing binding in turns)

  2. Check the worm gear at the top of the gear tower. It should have a bronze nut and a steel washer on each end. If a washer is missing or there is excessive play in the worm gear it can cause issues particularly in turns. (this was the other)

  3. Check the side frames to see if they are on tightly.

If it doesn’t make the noise without the shell on the something a vibrating against it. If you have installed DCC, some of the wires may be being pushed by the trucks against the shell in turns creating noise.

Other than that, if you go back and look at some previous posts, folks talk about running it with toothpaste in the gearing for awhile then cleaining it out and lubing it up.

4

I had/have this with a Dash 9 and an AC4400. Tried dismantling the trucks, has reduced but not cured it. Am planning to try putting grease on each end of driveshafts in an effort to stop them wobbling, as I think this is causing the noise - interestingly it only happens when running backwards, not when running forwards for some reason. The situation has also improved since I changed my power unit - was using a Gaugemaster D, now using a Hammant and Morgan Duette (over 20 years old, bought by my dad in the late '70s!). This old beast seems to be ideally suited to Athearn drive units - a lot quieter and with better slow running! I suspect the Duette gives more current (amps?) at low voltages - just what’s needed for multi-loco formations.