biopace & harmonic chainset

"Rik O'Shea" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

I never used a biopace chainset. In theory the idea seemed good - helping your pedal stroke thru
the deadspot. Can anyone tell me why this idea never really took off and why we are not all riding
around on biopace chainsets ?

Is a completely circular pedal stroke really best - any studies to support this ? (Please, no
replies about "pedaling in circles not squares" !).

I recall in the Tour De France about 10 years ago, one team had a chainset with a big chainring
that was circular but completely mis-shapen. I think is was an ad-hoc French design called
"harmonic" designed by an engineer who said that it allowed the pedal stroke to follow some
harmonic pattern that improved pedalling efficiency. The chainset was banned by the UCI (maybe it
was too ugly, Dura Ace 2004 chainset is another story/thread). Does anyone have any info on this
and whether there is any validity to this harmonic pedal stroke idea ?

-R

As for why we're all still riding around on round rings, it's really pretty simple. Just about every
other design has been tried (by many end users) and abandoned as ineffective in delivering on its
claims, or at least the gains in some situations proved unworthy of the overall tradeoffs. Yet a few
people actually did prefer the alterna-rings, just enough that new devices to eliminate the dreaded
"dead spot" continue to turn up; witness the current Rotor Cranks.

And if the UCI banned the Harmonic chainrings, somebody forgot to tell the guys who still make and
sell them, or Bobby Julich, who rode some in the Worlds TT this year. So the truly curious can just
buy some and test the theory for themselves. Don't forget to share your results here... ;-)

SB

If you really look, biopace actually does the opposite of shortening the dead spot. It speeds up the
downstroke. Shimano's research only produced marginal gains with novice cyclists at 50 and lower
cadences which might explain the phasing; it supposedly mimics running. Tom

--
Bruni Bicycles "Where art meets science" brunibicycles.com
410.426.3420 Steve Blankenship <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

"Rik O'Shea" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

I never used a biopace chainset. In theory the idea seemed good - helping your pedal stroke thru
the deadspot. Can anyone tell me why this idea never really took off and why we are not all
riding around on biopace chainsets ?

Is a completely circular pedal stroke really best - any studies to support this ? (Please, no
replies about "pedaling in circles not squares" !).

I recall in the Tour De France about 10 years ago, one team had a chainset with a big chainring
that was circular but completely mis-shapen. I think is was an ad-hoc French design called
"harmonic" designed by an engineer who said that it allowed the pedal stroke to follow some
harmonic pattern that improved pedalling efficiency. The chainset was banned by the UCI (maybe
it was too ugly, Dura Ace 2004 chainset is another story/thread). Does anyone have any info on
this and whether there is any validity to this harmonic pedal stroke idea ?

-R

As for why we're all still riding around on round rings, it's really

pretty

Quoted message said:

simple. Just about every other design has been tried (by many end users) and abandoned as
ineffective in delivering on its claims, or at least the gains in some situations proved unworthy
of the overall tradeoffs. Yet a few people actually did prefer the alterna-rings, just enough
that new devices to eliminate the dreaded "dead spot" continue to turn up; witness the current
Rotor Cranks.

And if the UCI banned the Harmonic chainrings, somebody forgot to tell the guys who still make and
sell them, or Bobby Julich, who rode some in the Worlds TT this year. So the truly curious can
just buy some and test the theory for themselves. Don't forget to share your results here... ;-)

SB

"Bruni" <[email hidden]> wrote in message "]news:[email hidden]...

Quoted message said:

If you really look, biopace actually does the opposite of shortening the dead spot. It speeds up
the downstroke. Shimano's research only produced marginal gains with novice cyclists at 50 and
lower cadences which might explain the phasing; it supposedly mimics running. Tom

That's exactly right; I remember when BP first came out there was some confusion about the design.
Simple elliptical rings had just placed the major axis of the rings at the 3-9 o'clock positions
where you had the most leverage, and the minor at the 12-6 where you had the least. Shimano took a
different approach and looked at the variation in leg speed during each pedal stroke, trying to
match the ring profile with the natural fast/slow spots; a big gear for the slow spots and a smaller
one in the fast sections. They ended up with irregular, non-symmetrical shapes with the highest
"bump" in the rings near the bottom of the stroke. Different profiles for different size rings, as
well. They were intended for people who didn't have a well-developed pedal stroke and used lower
cadences than what was generally recognized as optimum for racers. But even Biopace rings got
rounder on the rings that were intended for higher cadences, so Shimano already recognized the
limitations of non-round rings when they first made them.

SB