Biopace Chainrings on 'Bent'

Discussion in 'Cycling Equipment' started by TommyJ, Feb 23, 2004.

  1. TommyJ

    TommyJ New Member

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    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.
     
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  2. bball

    bball Guest

    On Mon, 23 Feb 2004 18:10:31 GMT, TommyJ
    <[email protected]> wrote:

    >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
     
  3. 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 http://www.geocities.com/czcorner
     
  4. meb

    meb New Member

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    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.
     
  5. meb

    meb New Member

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    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.
     
  6. [email protected] (Chris Zacho "The Wheelman") wrote in message news:<[email protected]>...
    > 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?

    > 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?

    >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?

    > 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
     
  7. meb <[email protected]> wrote in message news:<[email protected]>...
    > Chris Zacho "Th wrote:
    > > ... 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
     
  8. >From: [email protected] (meb)

    >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.
    http://www.sheldonbrown.com/biopace.html

    "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 http://www.geocities.com/czcorner
     
  9. meb

    meb New Member

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    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.” :D

    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.
     
  10. A Muzi

    A Muzi Guest

    TommyJ wrote:
    > 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
     
  11. [email protected] (Chris Zacho "The Wheelman") wrote in message news:<[email protected]>...
    > From: [email protected] (Andrew Bradley):
    >
    > Edited for space (this post is long enough already!):

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

    > >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.

    > >Can you explain this better?
    >
    > Sheldon can give you the scientific explination, he has more room on his webpage that I do here:
    > http://www.sheldonbrown.com/biopace.html

    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.

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

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

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

    > 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.

    > 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?

    > Sometimes they can barely even keep up!

    True, but not normally a problem with a round ring

    >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").

    > 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.

    > 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
     
  12. Tom Sherman

    Tom Sherman Guest

    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)
     
  13. Carl Fogel

    Carl Fogel Guest

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

    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
     
  14. bball

    bball Guest

    On Wed, 25 Feb 2004 23:08:40 -0600, Tom Sherman
    <[email protected]> wrote:

    >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? (What's left?)

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

    Tom Sherman Guest

    [email protected] wrote:

    > On Wed, 25 Feb 2004 23:08:40 -0600, Tom Sherman <[email protected]> wrote:
    >
    >
    >>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)
     
  16. Rick Onanian

    Rick Onanian Guest

    On Thu, 26 Feb 2004 18:47:48 -0700, [email protected] wrote:
    >>> ...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
     
  17. bball

    bball Guest

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

    >On Thu, 26 Feb 2004 18:47:48 -0700, [email protected] wrote:
    >>>> ...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
     
  18. bball

    bball Guest

    On Thu, 26 Feb 2004 19:38:39 -0600, Tom Sherman
    <[email protected]> wrote:

    >[email protected] wrote:
    >
    >> On Wed, 25 Feb 2004 23:08:40 -0600, Tom Sherman <[email protected]> wrote:
    >>
    >>
    >>>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
     
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