"Peter Dohm" wrote in message
. ..

I was only thinking of the exact ratios that place the same teeth in use
on each successive rotation of the belt.

Torsional resonance can be extremely difficult to monitor andI am glad
that you were able to identify it before it became a dissaster. For the
moment, my own project and the decision to build around a PSRU or use a
direct drive aircraft engine has been pushed further into the future. But
I have wondered whether the elimination of critical speeds might be the
true purpose of those little springs in the driven plate of a manual
clutch.


I think their primary purpose it simply to reduce or eliminate chatter when
engaging the clutch. Most high performance clutches don't even use them.