Spur gears

[rod335]

I have a couple of chassis I have built over the years which have Branchlines 3:1 straight cut brass spur gears driving the layshaft from the motor. Both chassis are very noisy. All other components, motor, final drive gears, are known to be quiet. Has anyone else used these gears? If so, have they experienced excessive noise and do they know of any alternative, quieter, gears? For reasons of my own I do not wish to replace them with a belt drive.

Rod

[tedp]

Rod - I am guessing but I suppose most straight cut spur gear driven chassis using a layshaft are noisy.

I have the same problem in the Fleischmann 0-6-0 diesel chassis I use in several of my locos, and I remember the old Arnold 0-6-0 tank with the layshaft drive had the same problem. I think it is the high RPM and coarse teeth that cause it - spur gears in the end drive are usually much quieter.

Even the use of plastic gears won't solve it - the Fleischmann chassis has nylon on metal gearing. All I can suggest is to find gears with the teeth cut at an angle, or with very fine teeth.

[rod335]

Thank you Ted, what you say makes sense of course. I had an old Arnold chassis of the type you describe which was also a real coffee grinder, deeply unpleasant bit of kit in many other ways as well! However, the Branchlines gears appear to be far more than averagely noisy so I was hoping someone else had used them and come up with a solution. Probably a bit of a vain hope though.

[tedp]

Although it won't solve your problem, here is an article that gives an insight in possible causes for gears noise. The article suggests pinion teeth should be 'crowned' or 'barreled' so the thickness of each tooth varies along its length. Tapered ends to the teeth.

I suspect the teeth of your gears are the culprit. Probably they are sensitive to very tiny alignment errors. Re-cutting them is obviously not a practical idea.

What you might try however is smear them with polishing paste instead of oiling them, and running the motor for a few minutes. The noise will be frightful but chances are that any offending tooth surface will be ground down to a better fit. I use this approach to even out slight quartering mistakes in rod-driven chassis.

[rod335]

Using a cutting agent is something I tried, long ago! Didn't seem to make any difference. Maybe I'm just too fussy.