aluminium

Could anyone advise the most suitable alloy spec to use for timing gears 0n a model aero engine please?

I might be wrong, but I would think any alloy of aluminium is going to be short lived as a gear, maybe hard anodised, or chromed would be ok, maybe someone else knows better. Ian S C

Unless you have a real weight issue I would go with steel, most of the published designs have steel gears. If you do want to keep the weight down then you can thin out the area between hub and teeth, drill a series of holes or a bit of both. Something along these lines

Basic gear

Drilled & turned

The 1000cc Vincent motorbike uses an aluminium timing gear (idler). Colin

Thanks for the response everyone,many years ago Colin I had a Vincent Comet,this had an alloy large idler timing gear,which triggered the question.

Peter,

Reputedly, the Vincent used RR56 alloy for the large idler.

Do a Google search for RR56 and you will find details.

MichaelG.

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P.S.   There was a chap used to write in MPH, who always referred to his son as ET50

Edited By Michael Gilligan on 24/04/2014 21:05:24

I wonder if the fact it was only the idler that was aluminium was why it was OK as there would be much less risk of the metal picking up like you would expect alloy on alloy?

J

.

Very probably ...

Also, the lubrication system is very well done.

MichaelG.

Thanks Michael,Will google that material.Sadly at 83 I have'nt got the balls to ride any more,had avelo Viper until 2 years ago,did'nt get round to restoring it so sold it to a mate.Happy days.

I make timing gears for Triumph motorbikes and others they seem to run no problem, I also make rear sprockets out of Ali, I use 7075 T6 but I have used 2014 and 6082 the later is readily available but not as good as the others, you could get them hard anodised for longevity if you feel the need.

HTH

Shaun

For the record, the original Vincent idler gear was a bronze casting, and it tended to clatter and clang. The factory 'solution' was to use a forged light-alloy wheel which would expand along with the crankcase. But they still sounded like a dustbin being dragged across cobbles. I had one.

The rest of the train (crank input & camshafts) was steel gears.

cheers, Tim

Thanks for the ali spec involute curve,will try and source some of that.Graham the tufnol sounds good,many of the motor cycle auto advance & retard mag gears were made of this,my main gear on the model is a ring gear so I will need to plane the teeth I guess,not sure if I could do that with tufnol?