Elliptical Chainrings

"none (Yannick Tremblay)" yatremblay@bel1lin202. wrote in message
...
In article ,
Steve Freides wrote:
Mower Man wrote:

Isn't it the point that elliptical chain rings actually vary the gear
ratio? Forget the number of teeth, they're only there 'cos a chain is
used. Think of diameter. Variable diameter. Honest. Think drive belt?
Big pulley vs small pulley?

But big pulley versus small pulley, first of all, means something
different for belt drive than for one with teeth. If one pedal
revolution gets you 39 teeth spaced evenly apart, what's the difference
what the shape is? For a belt driven system, a change in shape could at
least mean a change in circumference.

For 1 complete revolution, there is no difference. Absolutely correct.

However what about 1/4 of a revolution or 1/8 of a revolution? Then
the diameter of the "big pulley" does differs.


True, but *overall* diameter doesn't change as the number
of teeth remains the same. So, the gear ratio remains the
same. And, as long as the chainring radius is no greater than
that of the crank arm there isn't even any leverage difference
as if often the (erroneous) claim, due to the fact that it's
the length of the crank arms that determines the lever arm.

--
Sir Gregory