On Fri, 24 Oct 2008 18:17:44 -0700, "Michael Koblic"
wrote:

I have a vague memory of reading about rules that govern the design of
pulley and belt transmission, specifically the optimum distance between
centres of the pulleys and the maximum recommended ratio of pitch diameters.
I cannot find the reference and I am beginning to wonder if I dreamt it.

Clearly there is going to be some power loss if the angle of belt contact
with the small pulley is much less than 180 degrees but are there any math
formulae which would help in optimum design? I have been through Google
(again!) as well books and all I am finding is old stuff related to flat
belts made of cowhide and such.

Thanks,

Try the Gates Rubber website. I think it's www.gates.com. They have
excellent downloadable PDF catalogs with good engineering sections.
You have to register first. There is also a downloadable belt drive
design application that does center distance, horsepower capability,
belt type selection, pulley selection, etc. It's Design Flex Pro. I
used it about two weeks ago. Works very well. You get a PDF report
with part numbers for output.

Pete Keillor