Garden Railway Forum

Hello all,

I am pretty sure there may be a thread detailing this somewhere, but 40 minutes of looking, has not found it!

I have a second hand loco, with worn gears:
A worm on the motor, and a straight-cut gear on the axle..
The teeth on the wheel, are worn concave in the middle, and it looks like someone has moved the gear on the axle, to try to get a better mesh, of worm and wheel?

How do you calculate gear diameters and spacing, to source replacements?
Ideally, I would like to keep the noise down, so wonder if plastics gears might be a better option?

Thanks in advance,
Phil.P

Worm wheels are sometimes manufactured concave to get a better mesh with the worm, so it may just be that they need lining up properly and then the motor/axle gap adjusting to get the mesh, rather than moving the worm wheel sideways which is what it sounds like has happened.

When I was trying to work out the modulus of the gears on my Bachmann Lyn, I tracked down an online calculator - basically you enter the diameter of the gear wheel and the number of teeth. However, a discrepancy of a tenth of a millimetre on the diameter will give different readings on the modulus - tricky when the gear wheel is worn like yours.

I found this forum discussion enlightening, but in the end just struck lucky when I found the gears on another Bachmann model meshed.

https://www.model-engineer.co.uk/forums ... ?th=118117


Rik

As part of a previous life I built and assembled rear axles for for (1:1) buses and trucks, and the tolerance to get the correct mesh on the pinion and wheel was very fine less than 0.005" (obviously a long time ago), not quite a worm and wheel but the same principle. so in modelling a lot of "hit and miss" work