Noisy Gear Trains

[mushroom2]

I'd been working on a locomotive that had a very noisy gear train. I finally traced it to some bad bearings, but I was wondering that if it proved to be just gear mesh noise, how do you quiet that?

[leghome]

I asked a good friend of mine who is known as Dr Loco and he said the only way to quiet gear noise is wiht a light coating of grease. He also told me that grease does not always work.

[Roger Hensley]

Assuming that it is gear noise from hard plastic gears, in the past I have filled the gear case with vaseline and ran it each way for 30 minutes. Then I disassembled the gear case and cleaned out and off ALL of the vaseline (you gotta get it all), lightly lube with a plastic compatible oil like Labelle 108 and reassemble.

This works, but it is a lot of work and you MUST get the gears and gearcase clean. In the 80s when I owned a hobby shop, Model Power had some great E7s with large can motors. They were beautiful, but very noisy. The ones that I sold weren't noisy at all and the above was the reason. I have heard that several of those units are still in service a model rr near here. :-)

[mushroom2]

Vaseline? I thought that was a lube of sorts. What does that do? And by hard plastic do you mean nylon (the white gears)?

[Keith 55]

I have been told more than once, but never tried, using toothpaste instead of Vaseline.
The powdered marble (rock) in the paste acts as an abrasive to gently round corners and otherwise smooth out the gears.
Plus, it's easier to clean out.
What I HAVE done is take trucks completely apart and used alcohol, 400 grit wet/dry sandpaper, Xacto knife and/or needlefiles to clean up the gears.

BTW, Vaseline PETROLEUM Jelly---The name makes me worry about it's long-term effects on plastics.

[kenw]

I've been told by several to use Pearl Drops tooth polish to make them smooth, clean it out with isopropyl alcohol after it gets quiet, then lube with an appropriate grease (not just an oil).

[mushroom2]

I've heard about toothpaste. I've never heard of vasoline. I'm not saying I don't believe it works, just curious how it works.
Toothpaste I can understand since it's abrasive. Just wondering if there was any other way.
Is there a difference between what you use for nylon and metal gears?

[Roger Hensley]

No, hard plastic is NOT white nylon. My technique doesn't work with nylon, nor does it work with "slippery engineering plastic"-Delrin.

The noise with hard plastic gears is caused by the hard surfaces running against each other. The vaseline softens the surface of the plastic and helps promote 'run in' (wear) where the gears wear into a pattern of mating therby lessening the noise.

You are correct to worry about the future effects of the vaseline. That's why it's important to clean it out! As to long term effects, still operating with no problems after 22 years speaks to the fact that it works when done properly.

[kenw]

the pearl drops (ie, toothpaste with abrasive) won't do squat on metal gears. I would think that metal gears would need something like a jewelers' rouge or other "non-edible" polishing compound. But knowing how metal gears are made, the need for polishing should be quite rare. More likely it's just clatter and a decent grease should quiet that up nicely.

Either way, it is important to remove any polish once the gears are smoothed.

Vaseline is a fair lubricant and like greases will quiet gear chatter caused by relative movement btween the gears. But it won't polish or clean rough surfaces that may (or may not...) be causing the noise to begin with.

[mushroom2]

Roger has a good point. I had forgotten about hard plastic gears.
So it sounds like you better know what your gears are made from before you try anything.

Roger another question. I guess you should make sure that there are no gross alignment errors before using vasoline? That could wind up deforming the gears, correct?

[mushroom2]

So the consensus is:
Vasoline for hard plastic.
Tooth polish for nylon. Does it also work on Delrin?
A double bastard file on metal (just kidding) :D

[Roger Hensley]

So the consensus is:
Vasoline for hard plastic.
Tooth polish for nylon. Does it also work on Delrin?
A double bastard file on metal (just kidding) :D

As to distortion, hopefully, you will see this before you begin when you examine the gear train. Poor gears are not going to get better with this type of treatment. I never ran into any, but I have found that there is flashing on the gears at times. Yes, that will need to be cleaned up first. Sometimes, that is the problem, but when it isn't, it is nice to know another method.

To my knowledge, nothing will work well on Delrin. The Pearl Drops will also work on hard plastic, but it will take a very long time to get run in. Probably much longer than most people will give it.

Just be certain that things are clean before you re-assemble them.

[mushroom2]

Thanks for all the info and especially about the vasoline.