Biopace Chainrings on 'Bent'

TommyJ said:

Searched this site and found mention, dated 23-10-03, of biopace used on a 'bent'. I'm attempting
to install a set on a Lightning P-38 and wonder what the person posting that last message, or
anyone else might have learned/heard on this subject. Thanking you in advance.

-----------

Hiya Tommy,

I've used a biopace set on a Horizon for about 10K miles and love them. They're not for those who
prefer spinning circles, particularly at higher cadences, but great for "stride riders" who favor
about 17mph on the flats @60rpms for easygoing travel. The biopace feel gives you a steady push from
contracted leg to extended, i.e. smooth power stroke. To me, this is well suited to a bent.

My Horizon setup is 53, 44, 26; 26" rear wheel with 11-32 cassette.

Curiously, I find no advantage of a biopace set on diamond frames, which I've been riding for
the past three years. The difference is not nearly as noticable to me; I most often use round
rings on DFs.

You might experiment by alternating the big ring (easy to swap) between round and biopace, and
compare the feel on several 30-40 mile rides.

Sheldon (better than round) Brown has a nice discussion on biopace.

Bruce Ball, Colo Spgs Waiting for a new Haluzak seat frame

I've used Bio's for decades, and since I also know how they work, I can
tell you they _won't_ work on a recumbent. At least, you wouldn't derive
there benefits, actually, it would be worse than round. Here's why:

The BioPace design is meant to accelerate the pedals on the up-down stroke, and decelerate them
through the forward-back stroke (or "dead spot"😉. This is what a rider's legs do when he's NOT
spinning. Ergo the rider doesn't have to spin in order to match leg motion to the pedal motion as he
would with a round ring.

So both spinning and Biopace achieve better efficiency, but each one does it in a diametrically
opposite way.

However, BioPace was designed for use on an upright bicycle in which the rider's legs are about
90=BA from the chainline, On a recumbent, they are almost parallel. So the action of the rings would
now be 90=BA out of phase of your legs

Not that you can buy them anymore anyway :-3(>.

"May you have the wind at your back. And a really low gear for the hills!"

Chris Zacho ~ "Your Friendly Neighborhood Wheelman"

Chris'Z Corner geocities.comczcornerOpen ↗

Quoted post said:

Originally posted by TommyJ
Searched this site and found mention, dated 23-10-03, of biopace used on a 'bent'. I'm attempting to install a set on a Lightning P-38 and wonder what the person posting that last message, or anyone else might have learned/heard on this subject. Thanking you in advance.

That probably was my Biopace recumbent orientation thread.

To set up you want the pedal at dead spot to coincide with the chainring minor axis being at the chain entry so that the low leverage positions adjacent the dead spot have maximum leverage.

On an upright the rider is standing to seated about to 20 degrees back of vertical over the chainring with a near horizontal chainrun.
My 53T ring is designed for an upright rider with a crank to hip vs. chainrun angle of 72 degrees. I don’t know if differing sizes were designed for differing rider positions, but since 18 degrees permits cranks to have major axis oriented coincident with the arms orientation, I suspect they were all oriented identically. If different, I suspect the smaller rings would be oriented to a more vertical rider as he would likely be standing or in use with a mountain bike.

On a bent, you probably are 30+/15 degrees up from horizontal (60+/- degrees back of vertical).
Chain run probably 0-40 degrees down from horizontal.

The BEC holes are 72 degrees apart, you can adjust as best matches the optimal oreintation. If you have a splined BB, you have more adjustment flexibility.

If you’re off more than 36 degrees, remember rotating the ring 2 or 3 holes is equivalent to adding or subtracting 36 degrees to your phase.

I have a 41 degree angle on the bent hip-crank line vs. chainline on the bent with Biopace.
By rotating two holes, I’m only off by five degrees.

If you’re still dissatisfied with the best available orientation, Highpath Engineering in UK makes elliptical chainrings of custom eccentricities at about $100 each and custom makes each ring orientation to your seat/chainrun position./bcd pattern in your choice of teeth. They can even make you large rings up to 110T at premium prices.

Someone responded over at bikeforums.net that Gardner Martin had posted recumbent biopace setup information used on a world record run, but I never located the post and just measured myself.

Highpath Engineering has some good diagrams for their rings since they orient theirs the same as Biopace, could be useful drawings.

Quoted post said:

Originally posted by Chris Zacho "Th
...

The BioPace design is meant to accelerate the pedals on the up-down stroke, and decelerate them
through the forward-back stroke (or "dead spot"😉. This is what a rider's legs do when he's NOT
spinning. Ergo the rider doesn't have to spin in order to match leg motion to the pedal motion as he
would with a round ring.
...

This is off 90 degrees.

The Biopace accelerates motion (lower ratio) at the top/bottom, decelerates in the power stroke (higher ratio). This reduces the torque peaks and raises the torque troughs.

[email hidden] (Chris Zacho "The Wheelman"😉 wrote in message news:<[email hidden]>...

Quoted message said:

I've used Bio's for decades, and since I also know how they work, I can tell you they won't
work on a recumbent. At least, you wouldn't derive there benefits, actually, it would be worse
than round.

Biopace is better than round?

Quoted message said:

Here's why:

The BioPace design is meant to accelerate the pedals on the up-down stroke, and decelerate them
through the forward-back stroke (or "dead spot"😉. This is what a rider's legs do when he's NOT
spinning.

Can you explain this better?

Quoted message said:

Ergo the rider doesn't have to spin in order to match leg motion to the pedal motion as he would
with a round ring.

And this bit? Dont the legs always have to follow pedal motion?

Quoted message said:

So both spinning and Biopace achieve better efficiency, but each one does it in a diametrically
opposite way.

Don't see how spinning, or biopace improve efficiency.

Andrew Bradley

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

Quoted message said:

Chris Zacho 'Th said:

... The BioPace design is meant to accelerate the pedals on the up-down stroke, and decelerate
them through the forward-back stroke (or "dead spot"😉. This is what a rider's legs do when
he's NOT spinning. Ergo the rider doesn't have to spin in order to match leg motion to the
pedal motion as he would with a round ring. ...

This is off 90 degrees.

The Biopace accelerates motion (lower ratio) at the top/bottom, decelerates in the power stroke
(higher ratio). This reduces the torque peaks and raises the torque troughs.

I think you'll find Chris Zacho was right. What you describe is the "traditional" elliptical.

Andrew Bradley

Quoted message said:

From: [email hidden] (meb)

Quoted message said:

This is off 90 degrees. The Biopace accelerates motion (lower ratio) at the top/bottom, decelerates
in the power stroke (higher ratio). This reduces the torque peaks and raises the

torque troughs.

Actually, if I read your post right, your description is actually for _prior_ designs of _eliptical_
chainrings, in which the rider would have to push the pedals harder on the up/ down, and his feet
would skip quickly through the for/aft "dead-spot". Am I right? If I have interperated what you said
backwards, please disregard the rest of this reply and accept my appologies.

If I do have it right...

BioPace does not work this way. it's designed to keep pedaling pressure (more or less) constant
throughout the entire pedal circle, down-back-up-forward. smoothing out the flow of power just like
spinning does on a round ring.

You need to read Sheldon "Better Than Round" Brown's article on this.
sheldonbrown.combiopace.htmlOpen ↗

"May you have the wind at your back. And a really low gear for the hills!"

Chris Zacho ~ "Your Friendly Neighborhood Wheelman"

Chris'Z Corner geocities.comczcornerOpen ↗

Quoted post said:

Originally posted by Chris Zacho "Th
>From: [email hidden] (meb)

Quoted message said:

This is off 90 degrees. The Biopace accelerates motion (lower ratio) at the top/bottom, decelerates
in the power stroke (higher ratio). This reduces the torque peaks and raises the

torque troughs.

Actually, if I read your post right, your description is actually for _prior_ designs of _eliptical_
chainrings, in which the rider would have to push the pedals harder on the up/ down, and his feet
would skip quickly through the for/aft "dead-spot". Am I right? If I have interperated what you said
backwards, please disregard the rest of this reply and accept my appologies.

If I do have it right...

BioPace does not work this way. it's designed to keep pedaling pressure (more or less) constant
throughout the entire pedal circle, down-back-up-forward. smoothing out the flow of power just like
spinning does on a round ring.

You need to read Sheldon "Better Than Round" Brown's article on this.
sheldonbrown.combiopace.htmlOpen ↗

"May you have the wind at your back. And a really low gear for the hills!"

Chris Zacho ~ "Your Friendly Neighborhood Wheelman"

Chris'Z Corner geocities.comczcornerOpen ↗

I read Sheldon’s page.
You have it right Chris.

Soooooo: re-label than setup procedure “How to Mount a Biopace Chainring as a Traditional Elliptical Chainring.” 😄

And for the how to set up a Biopace chainring per Shimano’s objective: substitute major axis and minor axis.

With that orientation I now understand the cadence specific limits Biopace had. Seems it would in part be ratio specific with Shimano’s orientation as well.

The allegation of that orientation reducing loss of traction on mountain bikes seems counterintuitive. With a low effective gear on the max power portion of the circle you should get bigger torque peaks and longer torque troughs at the wheel-more likely to break the tires loose. Can anyone explain that?

I’m still digesting Sheldon’s report about Shimano’s momentum and energy storage principle.

TommyJ said:

Searched this site and found mention, dated 23-10-03, of biopace used on a 'bent'. I'm attempting
to install a set on a Lightning P-38 and wonder what the person posting that last message, or
anyone else might have learned/heard on this subject. Thanking you in advance.

Should be straightforward. Actually many parts from bicycles can fit recumbents, too.

Why wouldn't it?

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

[email hidden] (Chris Zacho "The Wheelman"😉 wrote in message news:<[email hidden]>...

Quoted message said:

From: [email hidden] (Andrew Bradley):

Edited for space (this post is long enough already!):

Space no problem. Think you over-edited a bit, Chris.

Quoted message said:

Quoted message said:

Biopace is better than round?

Not better. Just another way of achieving the same thing as spinning on a round ring, a smooth,
even flow of power to the wheels.

I would like to see power readings to confirm that but don't see any advantage unless in low
traction conditions when my experience was biopace made things worse.

Quoted message said:

Quoted message said:

Can you explain this better?

Sheldon can give you the scientific explination, he has more room on his webpage that I do here:
sheldonbrown.combiopace.htmlOpen ↗

Mechanical energy is stored and released near the "dead spot" (as indeed it is with a round ring to
some extent) but there's more to it than that. I'd like to see some real world power data or a more
detailed explanation taking into account the effect of muscle work.

Quoted message said:

Quoted message said:

Don't the legs always have to follow pedal motion?

Quoted message said:

Only in that they have to move in a circular path.

What you mean, they can chose a different speed or something?

Quoted message said:

The human leg wasn't "designed" to move in a circle. It was meant to :
1. Support and lift the body against gravity, and:
2. Move it forwards.

Since the first requires more force, the muscles which do this are stronger. Hence when they are
used to turn a bicycle crank, the apply more force when they are in use. This happens when the
up/down half of the pedaling cycle, and the pedals speed up.

It doesn't speed the pedals up to any degree unless you are on a steep hill, in which case you get a
biopace effect for free. I don't see the point you are making.

Quoted message said:

When the pedals move through the for/aft motion, the weaker muscles are used. However, they are
not as strong, and therefore cannot push as hard.

If they are not as powerful, they are not as powerful- nothing to be done, is it a good idea to hang
around in that sector?

Quoted message said:

Sometimes they can barely even keep up!

True, but not normally a problem with a round ring

Quoted message said:

The result is an interrupted "push-coast-push-coast" transmission of power to the wheels.

Think of trying to drive your car by rapidly stepping on the gas, then lifting your foot off it,
again and again and again for the entire trip. How do you think this would affect it's efficiency
(gas mileage, if you wish)?

This seems to describe the feel of biopace to me. You'll have a hard time convincing people there's
an efficiency gain unless it's due to lower cadence (there isn't an efficiency gain with
"spinning"😉.

Quoted message said:

Spinning reduces this interrupted power by causing the feet to move at a more even rate around
the entire circle, the way the pedals move with round rings. Result; an even flow of power to
the wheels.

An even rate of foot movement, how do you mean? If the rate does get significantly uneven up a
decent hill, it tends towards biopace. That's either good or it isn't.

Quoted message said:

Biopace works "diametrically opposite" (the other way around) by changing the speed of the pedals
as they rotate, repeatedly speeding them up and slowing them down in time with your feet (when not
spinning). Result; an even flow of power to the pedals.

Surely the pedals are always in time with your feet, no?

Andrew Bradley

A Muzi said:

...Actually many parts from bicycles can fit recumbents, too....

That is good to know, in case I ever need to replace something. 😉

Tom Sherman - Quad Cities (Illinois Side)

Tom Sherman <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

A Muzi said:

...Actually many parts from bicycles can fit recumbents, too....

That is good to know, in case I ever need to replace something. 😉

Tom Sherman - Quad Cities (Illinois Side)

Dear Tom,

It is indeed surprising how many parts from bicycles will fit recumbents.

Some claim that this demonstrates a genetic relationship not apparent at first glance.

But this notion is obviously mistaken, since it is well known that no part from a recumbent can be
transplanted into a bicycle without serious side-effects and rejection.

Carl Fogel

Tom Sherman said:

A Muzi said:

...Actually many parts from bicycles can fit recumbents, too....

That is good to know, in case I ever need to replace something. 😉

Tom Sherman - Quad Cities (Illinois Side)

D'ya suppose standard wheels, derailleurs, cranksets, cassettes, shifters, brakes, headsets, bb's,
chains, actually work on them dork bikes? (What's left?)

bball, colo spgs today, back on the blue Horizon after 3yr DF hiatus, on biopace

Quoted message said:

Tom Sherman said:

A Muzi said:

...Actually many parts from bicycles can fit recumbents, too....

That is good to know, in case I ever need to replace something. 😉

Tom Sherman - Quad Cities (Illinois Side)

D'ya suppose standard wheels, derailleurs, cranksets, cassettes, shifters, brakes, headsets, bb's,
chains, actually work on them dork bikes?

There have been confirmed sightings of recumbents with Campagnolo parts on them - such blasphemy!

Tom Sherman - Quad Cities (Illinois Side)

Quoted message said:

Quoted message said:

Quoted message said:

...Actually many parts from bicycles can fit recumbents, too....

That is good to know, in case I ever need to replace something. 😉

D'ya suppose standard wheels, derailleurs, cranksets, cassettes, shifters, brakes, headsets, bb's,
chains, actually work on them dork bikes? (What's left?)

*snicker*

*giggle*

Saddles?

*big, dumb grin*
--
Rick Onanian

On Fri, 27 Feb 2004 16:29:12 -0500, Rick Onanian <[email hidden]>

Quoted message said:

Quoted message said:

Quoted message said:

> ...Actually many parts from bicycles can fit recumbents, too....
That is good to know, in case I ever need to replace something. 😉

D'ya suppose standard wheels, derailleurs, cranksets, cassettes, shifters, brakes, headsets, bb's,
chains, actually work on them dork bikes? (What's left?)

*snicker*

*giggle*

Saddles?

*big, dumb grin*

----------------

Bars are usually weird, too

bball, colo spgs most comfortably back on the lawn-chair cruiser, the blue Horizon (and biopace, but
of course) 7500 to go for '04

Tom Sherman said:

Quoted message said:

Tom Sherman said:

A Muzi wrote:

>...Actually many parts from bicycles can fit recumbents, too....

That is good to know, in case I ever need to replace something. 😉

Tom Sherman - Quad Cities (Illinois Side)

D'ya suppose standard wheels, derailleurs, cranksets, cassettes, shifters, brakes, headsets,
bb's, chains, actually work on them dork bikes?

There have been confirmed sightings of recumbents with Campagnolo parts on them - such blasphemy!

Tom Sherman - Quad Cities (Illinois Side)

------------

The horror, the horror!

One suspects the super-rich recipients of the Bush tax cuts or the poor-mouthing Rolex
wearing LBSers

bball, colo spgs, of 105, 600, SunTour calibre once stealthcamped on the Davenport side while
hitchhiking thru, washed my underwear & clothes in the Mississippi. on the blue Horizon