Son of Biopace?

[pH]

I remember the old Shimano Biopace chainrings and, for that matter, some
aftermarket chainrings that were pretty extreme ovals/elipsoids.

I saw a mountain/hybrid bike going by on the road today and could not help
but notice that the single chainring was "biopace-like". Not round.

I'm not up on the latest greatest, but since history repeats itself and
bicycles always re-invent the wheel (much to Jobst's annoyance) I would not
be surprised that another iteration is wending its way through.

Anyone else see any?

I notice more and more electric bikes out there.
I think that's great if you're doing it because you want to or think it's
keen and not to be green or reduce one's "carbon footprint." (Stop me
before I rant again!)

A registered curmudgeon and contrarian, I am very concerned with my
potassium and sulfur footprints instead...just because.

Well, anyway...Biopace wobbles again! (maybe)

Pureheart in Aptos

[Tom Kunich]

Biopace and the like, were a wet dream of a mechanical engineer, no doubt one of Krygowski's students. I never understood what they thought they could gain and careful testing showed that they gained nothing and probably lost since Biopace really interfered with smooth pedaling.

[AMuzi]

They're discussed in Sharp's 'Bicycles and Tricycles' from
1899. They are periodically 'rediscovered', and then
abandoned, in a regular cycle.

--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971

[funkma...@hotmail.com]

It depends on who you want to believe. Elliptical chainrings _do_ work for some people, but not everyone. Every rider has a somewhat different biomechanical efficiency. The elliptical chainrings may help, or even hurt depending on the individual. For the vast majority there isn't much of a difference.

Further to the point that your physiology is a major factor on the effectiveness, https://pubmed.ncbi.nlm.nih.gov/16846753/ "The use of an eccentric chainring during an outdoor 1 km all-out cycling test" states:"when time was saved with the eccentric chainring, it was significantly correlated with estimated lower limb muscle volume.....The physical variables associated with eccentric chainring performance were muscle anthropometric parameters. We have interpreted our results cautiously and suggest that the subjects who had greater lower limb muscle volume and greater calf muscle volume, seem to have had a significant advantage in performing with the eccentric chainring."

But in general, there isn't much of an effect. Most studies find no benefit.

https://pubmed.ncbi.nlm.nih.gov/21266731/ "The influence of elliptical chainrings on 10 km cycling time trial performance "
From the abstract: "Elliptical chainrings do not appear to provide a performance benefit over traditional circular chainrings during a mid-distance time trial. "

https://pubmed.ncbi.nlm.nih.gov/12955523/ "Physiological responses during cycling with noncircular "Harmonic" and circular chainrings "
From the abstract: "comparison of the physiological response in this study did not translate into an advantage of the Harmonic over circular chainring during submaximal and maximal pedaling in trained cyclists. "

http://www.ijsei.com/papers/ijsei-88619-19.pdf "Optimally Positioned Elliptical Chainrings Show No
Performance or Physiological Effects in 30s Sprints"
From the conclusion:"elliptical chainrings benefited neither performance nor blood lactate production during 30s Wingate tests. "

Even a study sponsored by Q-Rings saw no overall benefit. from https://triathlonmagazine.ca/training/bike/pedal-power-do-elliptical-chainrings-really-work/ "The study found no conclusive performance advantage to using Q-Rings, ...."

But, there are claims of success. Chris Froome, Bradley Wiggins, Magnus Backstedt, and Sara Storey have all won championships with them, and many professional riders (though a substantial minority) prefer them. I have a Wolf Tooth elliptical on my FS MTB. The only difference I can see is that it feels a little funny when I first get on the bike, but after a few minutes I don't notice.

[Frank Krygowski]

Anecdotes don't beat studies, but: I had an avid cycling friend who,
when they were new, claimed that Biopace cured his knee problems. He
continued using them long after they'd gone out of fashion.

I've never been a fan of Biopace, but I know that unlike simple
ellipses, Biopace was a result of some serious engineering by Shimano.
And given the fairly complex motion of the human leg while pedaling, it
would seem to be an amazing coincidence if a simple circular chainring
was the most efficient shape.

But then, amazing coincidences do exist. When things were first forming,
what were the odds that the moon would have almost exactly the same
apparent size as the sun?

--
- Frank Krygowski

[funkma...@hotmail.com]

I've head anecdotes about then helping with knee pain as well. It would be nice to see a study somewhere that looked at people with biomechanical issues that seemed to be fixed with non-round chainrings.

On that note, I have a set of Power Cranks - the design with the clutch bearings. The website bounces, I suspect he folded. That said, there was a _lot_ of data on his website that extolled them as a a useful tool for knee rehab. I'll tell you though, those things are _not_ for the squeamish.

[Jeff Liebermann]

On Mon, 24 Oct 2022 10:06:26 -0700 (PDT), "funkma...@hotmail.com"
<funkma...@hotmail.com> wrote:

>On that note, I have a set of Power Cranks - the design with the clutch bearings. The website bounces, I suspect he folded. That said, there was a _lot_ of data on his website that extolled them as a a useful tool for knee rehab. I'll tell you though, those things are _not_ for the squeamish.

Looks like the Power Cranks web site went offline in Mar 2022:
<https://web.archive.org/web/20220000000000*/http://powercranks.com>

I think this is the most recent:
<https://web.archive.org/web/20220325165653/http://powercranks.com/>

Studies of Power Cranks:
<https://web.archive.org/web/20220321141531/https://www.powercranks.com/studies.html>


--
Jeff Liebermann je...@cruzio.com
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558

[funkma...@hotmail.com]

On Monday, October 24, 2022 at 2:42:25 PM UTC-4, jeff.li...@gmail.com wrote:
> On Mon, 24 Oct 2022 10:06:26 -0700 (PDT), "funkma...@hotmail.com"
> <funkma...@hotmail.com> wrote:
>
> >On that note, I have a set of Power Cranks - the design with the clutch bearings. The website bounces, I suspect he folded. That said, there was a _lot_ of data on his website that extolled them as a a useful tool for knee rehab. I'll tell you though, those things are _not_ for the squeamish.

This is the one, good stuff there...Thanks

[Sir Ridesalot]

i still have Original Bio-Pace rings on a couple of my bikes. I like them.

Cheers

[William Crowell]

I have a Supergo Access MTB that I bought by mail order in 1987 that still has its original Shimano Biopace chainrings, and which I ride only occasionally because I prefer road riding. The bike was made in Taiwan from Tig-welded Columbus Cromor tubing.