In article ,
Sir Gregory Hall, Esq· åke wrote:
"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.

Please, this is pure mathematics and mechanics.

The "active" "current" diameter of the front rig changes dynamically
during a rotation which means that the current amount of rotation
of the pedal that is needs to achieve some specific rotation of
the rear wheel with the pedal-crank-rig-chain-cog-wheel assembly
changes dynamically. In average over 360 degree it is the same but
instantaneously it differs.

The problem and complexity occurs when you start introducing a bloody
human in the equation and these pesky things are pretty much impossible
to model mathematically and are notoriously irregular between
individuals.

Serously, by all mean disagree that it has any benefits to humans (I
am certainly not convinced either) but lets not disagree on
mathematics.

Yan