Cam Pulley Modification

[mack124]

Hello Guy,

I wasn't sure if I should post this on General Discussion or GC Q&A but here goes.
Many years ago I was designing a Gyrocopter that ran with a Subaru engine. When I was working on the reduction drive that bolted where the gearbox was, I spent quite some time getting the setup as efficient as possible. The reduction drive utilised a 100mm wide toothed belt and when running at a constant rpm for prolong periods of time the belts got quite hot.

The solution I came up with was I designed into the pulleys a very small grove that sat on the crest and the root of the tooth form. What this did was allowed the air to rush in and out as the belts tooth went in and out and thus reduced suction. The suction seems to be a minimal concern but it does cause a lot of heat so the result was startling. There was a noticeable reduction in belt temperature and running noise and there was a gain in overall efficiency, over 4% from memory. (it was a while ago)

So my question is has this sort of thing ever been tried on a cam pulley? I know the belt is only 1‚ wide compared to the Gyro¢ž¢s 4‚, but the cam pulley does run at a higher rpm so it might even out a bit. I¢ž¢d love to give it a try but I don¢ž¢t have the equipment available to me any more.

I've added some pictures. I hope it's clear.
Anyway I thought I¢ž¢d share that with you.

Kindest Regards
Gill

[Guy Croft]

Gill, hi

that is really most interesting. Thanks for writing that article. No, it's not something I'd ever known about or considered. But - I always wondered why the Integrale cambelt (see photo) had grooves in it, perhaps that is why.

GC

[mack124]

Guy,
I'd bet that is exactly what the grooves are for on the integrale belt. I might look at experimenting with a couple of pulleys and see what come up.

Thanks for the picture.

Regards
Gill