wrote:

So let me get this straight. The consensus now is that it has nothing
to do with the thickness of the belt but is to avoid resonance,
Logically resulting in less wow and flutter I would assume.



** The OP also posted his Q on sci.electronics.design and in my first reply there I pointed out the possible resonance issue as the reason for differing flywheel diameters.

A rubber belt and flywheel system has a resonant frequency - resulting from the springiness of the belt and the inertia of the wheel. I figured that where two flywheels are coupled by the same belt, it is better if their inertias are non identical so the resonant frequencies differ and so do not reinforce.



Really, on the surface is seemed that the thickness of the belt was
the reason for this but that has been eliminated.


** A really dopey idea based on a fallacy.


..... Phil