Dave,
Belts have a number of advantages. But one problem is the large diameter wheel required on the engine because a belt cant bend around a small shaft. I want a large speed reduction ratio in one stage to avoid the problems with secondary shafts.
The R-22, S-300 and Enstrom all use belts, then they employ a gearbox for reduction. Seems redundant to me.
Enstrom has a wide poly V (I think) (about 8" wide), looks like about 1 to 1 ratio. So the belt is not used for speed reduction.
For my low rpm rotor I will need about 18 to 1 speed reduction. Easy huh!
slowrotor