While the chain is not directly connected to the chainwheel it's full weight
has to be accelerated. Consider a chain on a sprocket that was the same
circumference as the sprocket. You would certainly consider that part of the
rotating mass. Making the chain longer doesn't reduce the mass.
>
> Umm, technically, the only rotating mass added to the crank is the extra row
of teeth on the crank chain drive, so the additional amount is actually rather
small (taking an extra ounce or so off the periphery of the flywheel would
more than compensate). The chain isn't considered as part of the rotating
mass since it's an independent member which both slides and rotates on its own
(at a much lower rate than either crank or cam), and the cam is operating at
half speed, so mass effects due to rotation are quite a bit less than for the
crank assembly. The dual chain does create a bit of additional frictional
drag, so it would consume a bit more power.
>
>
> Still, I agree--if reliability is not an issue, and the cam can be properly
degreed without an adjustable sprocket, why go to the additional expense?
>
>
> Cheers.
>
> --
>
>
> Michael Porter
> Roswell, NM
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