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Another useless gimic?

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Australia and New Zealand
Published
13 October 2003
Last activity
18 October 2003
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Alan Walker
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  1. Mike Holland <[email hidden]> wrote in message news:<[email hidden]>...

    [snip]

    Quoted message said:


    No, not if the flexing is elastic. Then you get the energy back. Just like a diver or gymnast does
    from a springboard.

    [snip]

    Dear Mike,

    I blush to admit that I'm familiar enough with some of your points to imagine that I follow you. I
    assure you that I wasn't arguing for or against any of them (who would listen to the likes of me?),
    just whining that the first flurry of posts about the strange Colnago chain-stay were just calling
    it names, not explaining what was wrong.

    Later posts have offered far more content, the kind that even I can parrot. I'm perfectly willing to
    throw stones at Colnago, but I need help with my aim.

    To put it another way, your post was far more interesting than any snide remark that I can come up
    with (like how those bulging cut-outs resemble tail-fins). They may be useless, but I wanted to read
    about what the use was and why they don't work.

    However, one of your points that I repeated above troubles me a little.

    Elasticity involves restoring absorbed energy, but it's always imperfect and energy is lost in the
    form of heat and sound and so forth, even when steel balls bounce off steel plates.

    I may have snipped too much, but where does your thinking lead? That is, do you favor increasing the
    elastic lateral flex of the metal frame, heading toward the diving board board end of the spectrum?
    Or would the most efficient frame reduce lateral flex as much as possible, which is what Colnago
    claims to be doing?

    Isn't all lateral flex and elasticity wasted in terms of making the bike go forward? Arguments that
    the effort involved doesn't amount to much should address the question of how much actually is
    involved--and my understanding is that it takes a surprising amount of force to deflect the rear
    frame of a bicycle.

    I long for detailed reassurance that Colnago is right or wrong. The voting is strongly against them,
    but I'd hate to have someone who actually addressed the design in question prove me to be wrong.

    Is Colnago's weird frame going to be noticeably better, roughly the same, or noticeably worse than
    good old God-fearing round chain-stays? Why?

    (I admire Sheldon Brown's web site, but I'm not up to applying it to a new design and I'm much too
    impatient to wait for widespread testing. Lord, how I love this business of getting expert opinions
    for free!)

    Thanks,

    Carl Fogel

  2. (Carl Fogel) said:

    to wait for widespread testing. Lord, how I love this business of getting expert opinions
    for free!)

    Yeah...expert...that's the ticket!

    Quoted message said:

    Thanks,

    Carl Fogel


    --
    Rick "Expert In Everything Except Some Things" Onanian

  3. Carl Fogel said:

    Isn't all lateral flex and elasticity wasted in terms of making the bike go forward? Arguments that
    the effort involved doesn't amount to much should address the question of how much actually is
    involved--and my understanding is that it takes a surprising amount of force to deflect the rear
    frame of a bicycle.

    Once. On the next pedal stroke, nearly all the energy comes from it undeflecting back to the
    centre position.
    --
    David Damerell <[email hidden]> Distortion Field!

  4. "Per Elmsäter" <[email hidden]> wrote in message
    "]news:[email hidden]...

    Quoted message said:
    Deep Freud Moors said:

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

    Quoted message said:
    Quoted message said:
    Quoted message said:


    I'm not JB, but according to the chart on the c40 page, a 100kg rider will have 5% less
    vertical flex = 0.05 * 0.06mm = 0.003mm.

    Let me guess... is that worth about 0.0000001psi in the tyre?

    Yeah, that's a good point. There are so many other factors involved, how could you possibly
    notice such a miniscule difference?
    ---
    DFM

    No problem. If you have an appropriate saddle of course.


    Good one :-)

    I was just trying to imagine how small 0.003 mm is. Take 1 mm, divide it into units of 10. Take one
    of those units and divide into units of 10. Take one of *those* units and divide it by 3. I don't
    think you'd pick that up even with a granite saddle.

    5 percent of buggerall is still buggerall.

    Jeff

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

    Quoted message said:
    (Alan Walker) said:

    Saw a very expensive frame in my local bicycle shop with large diamond-shaped holes in the
    chainstays. The carbon fibre tubes split into two, then rejoined, leaving a hole.

    That's what happens when bike buyers let silly people make their bikes out of plastic. (They could
    have shaped the frame like a carousel horse instead, but that would have been interesting, so of
    course they didn't.)

    In an episode of "Scientific American Frontiers"

    pbs.org1309 1.htm

    "In his course called "How to Make (Almost) Anything," Gershenfeld's students fabricate tangible
    objects from the plans they design on computers, using computer-controlled machines to cut through
    materials ranging from plastic to steel. Alan tries out a one-of-a-kind bicycle made by one student
    based on a model of Matisse's Blue Nude Number Two."

  6. David Damerell <[email hidden]> wrote in message
    news:<[email hidden]>...

    Quoted message said:
    Carl Fogel said:

    Isn't all lateral flex and elasticity wasted in terms of making the bike go forward? Arguments
    that the effort involved doesn't amount to much should address the question of how much actually
    is involved--and my understanding is that it takes a surprising amount of force to deflect the
    rear frame of a bicycle.

    Once. On the next pedal stroke, nearly all the energy comes from it undeflecting back to the
    centre position.

    Dear David,

    I'm sorry, but I'm still missing something here.

    Is the idea that as I push down on one pedal, some of my effort goes into flexing the frame
    laterally on the downstroke, but that I get most of this stored energy back on the upstroke of the
    same pedal as the flexed frame returns to its unstressed center position?

    If so, I'm worried about what the other pedal is doing and where the frame is flexing on its
    downstroke.

    Is the frame bending sideways slowly through each downstroke and then snapping back to the center
    position much more quickly (a jolt?) before slowly bending the other way under the pressure on the
    other pedal? That is, slow or sustained bending for most of each down stroke, followed by a quick
    release and snapping back to the center?

    I'm also troubled by the idea of "once." If it takes a lot of energy to bend a frame to one
    side, followed by a slow or quick elastic return to a center position, how does this help the
    next bending?

    Perhaps I'm using the wrong analogy? I'm thinking of a stiff steel rod in a vise being bent from
    side to side fairly slowly and imagining little or no help as I release the rod and it snaps back to
    its unstressed center position. This model seems more like lateral frame flex than a bouncing ball.

    Another model would be a bow and arrow--a slow deflection of the bow followed by a quick release of
    stored energy launches the arrow, but it doesn't seem to help me draw the bow again.

    Again, I'm sorry that I'm not following the physics here and I do appreciate your effort to explain
    it. I suspect that there's something obvious and crucial that I'm missing, like the pre-tensioning
    that's essential to understanding how bicycle wheels work.

    Thanks,

    Carl Fogel

  7. "Carl Fogel" <[email hidden]> wrote in message
    "]news:[email hidden]...

    Quoted message said:


    I don't know whether it actually does so or if such stiffness matters, but I was surprised by how
    much apparently ignorant scoffing your post generated. You'd think that rec.bicycles.tech posters
    would be curious about a weird new frame from a respected manufacturer.

    "Vertical Flex: With the new C40 HP, the rear triangle flexes 5% more in the vertical plane (see
    Figure 1 below); which should result in an increase in comfort for the rider.

    Lateral Flex: In addition, there was 3.5% less lateral flex (see Figure 2 below), thus increasing
    the torsional rigidity of the rear triangle. These results should allow greater power transfer from
    the frame."

    Question: what's 5% of nothing?

    Answer: more than 3.5% of nothing.

    This design is lame by their own admission...

  8. "David L. Johnson" <[email hidden]> wrote in message
    "]news:[email hidden]...

    Quoted message said:

    On Mon, 13 Oct 2003 19:51:48 +0000, Carl Fogel wrote:

    As far as this goes, according to the website you mention:

    Quoted message said:

    trialtir-usa.comc40 testing.html

    Indeed has a chart purporting to list the 5% increase in vertical flex. But the scale is
    revealing, it gives flex in millimeters X 10e4. At the highest mass tested, 100Kg, the new frame
    flexed not 600 mm, but 600/10000
    mm. .06mm. The old frame flexed 580/10000 mm, .058mm That .002mm difference is what they are
    advertising.

    Darn, their rear triangles flex .06mm at 100kg? No wonder my Cannondale beats me up so bad, it
    probably only flexes .03mm.

  9. (Carl Fogel) said:

    [email hidden] (Chalo) wrote:

    Quoted message said:
    Quoted message said:
    (Alan Walker) said:

    Saw a very expensive frame in my local bicycle shop with large diamond-shaped holes in the
    chainstays. The carbon fibre tubes split into two, then rejoined, leaving a hole.

    It's much more difficult to include such ugly and worthless contrivances when the maker is
    constrained to a proper material.

    Why is it harder to make these odd frame tubes with their diamond holes out of metal (I assume
    this is your proper material) than carbon fiber?

    Carbon frames are made of strips of carbon cloth which are soaked in epoxy resin and cured under
    pressure (or vacuum) in molds. Once the (expensive and time-consuming) tooling is made, the forms
    available are limited only by the shape of the mold or die, and the limitations of strength and
    stiffness of the fiber that can be laid in it.

    By contrast, a metal version of the Colnago F40 chainstay would be made by welding together either
    segments of shaped tubing or shaped sections that had been stamped or drawn to form halves of the
    desired structure.

    The shape can be had either way. However, in a metal frame it would elevate both the cost and weight
    enough to call into question the benefits of such a design (none) compared to its design tradeoffs.
    It would be difficult to sell most buyers of metal frames a feature that added maybe 25% to the cost
    of a frame, contributed about 1/2 lb. to the weight, and weakened the structure overall.

    Because of the high strength:weight ratio of CFRP, and because of its particular production cost
    considerations, both the weight and cost penalties of their chainstay design are reduced compared to
    a metal frame of like design. But those penalties still exist when compared to a more structurally
    optimized CFRP frame, and the benefit still remains at nothing.

    If that area of a bike frame could benefit from stiffening (and proven designs indicate otherwise),
    then simply increasing the vertical height of the chainstay would contribute much more stiffness at
    a much lower weight than Colnago's silly conceit.

    Colnago chose the design they did because its [censored] factor surpassed anything else they could
    concoct at such a low production cost. Design of this sort has successfully squandered whatever
    respect I might have had for the mainstream of the Italian bike business. It has graduated from
    "style with function" to "style over function", and I think that's a shame.

    Fashion being what it is, Colnago's goofy see-through chainstays will inevitably wind up on the [censored]
    heap with gems like PMP L-shaped cranks and Rigi split seat tubes. Not until after parting a lot of
    fools from their money, though.

    classicrendezvous.comPMP main.htm
    classicrendezvous.comRIGI main.htm

    Chalo Colina

  10. [email hidden] (Chalo) wrote in message
    news:<[email hidden]>...

    Dear Chalo,

    If I were a dog, I'd be lying on my side on the ground with a blissful expression and my hind leg
    twitching helplessly--yes, yes, that's it!

    Mark Twain's "Life on the Mississippi" is still fun to read because it gives the layman the
    comfortable illusion that he understands how to pilot a steamboat.

    Now you've given me the comfortable illusion that I understand why Colnago used carbon-fiber instead
    of metal--a weird shape is easier to create with a mould than by shaping and welding.

    You even topped it all off with those bizarre web pages. That L-shaped crank is marvelous! I'd never
    have known about it without your kind effort.

    Thanks!

    Carl Fogel

  11. Mike Holland said:

    Carl Fogel wrote:

    Quoted message said:
    Quoted message said:

    effort is needed to create that tiny wiggle in such a stiff arrangement of tubing?

    Not much, and you get it back on the upstroke.

    On second thought, that doesnt make sense. The frame absorbs energy by flexing as pedal weight
    increases, and returns energy as stress is reduced on the latter part of each stroke, down or up.

    To go back to the topic, don't worry too much about stiffness, as a little flex won't hurt. A
    touring frame needs to be stiffer to avoid wobbles under heavy load.

    The real trick in frame design is the strength-vs-weight tradeoff. And of course, cost.

  12. Peter Cole said:

    "David L. Johnson" <[email hidden]> wrote

    Quoted message said:
    Quoted message said:

    Indeed has a chart purporting to list the 5% increase in vertical flex. But the scale is
    revealing, it gives flex in millimeters X 10e4. At the highest mass tested, 100Kg, the new frame
    flexed not 600 mm, but 600/10000
    mm. .06mm. The old frame flexed 580/10000 mm, .058mm That .002mm difference is what they are
    advertising.

    Darn, their rear triangles flex .06mm at 100kg? No wonder my Cannondale beats me up so bad, it
    probably only flexes .03mm.

    Oh, the humanity....

    Mark Hickey Habanero Cycles habcycles.comhabcycles.com Home of the $695 ti frame

  13. Carl Fogel said:


    Is the idea that as I push down on one pedal, some of my effort goes into flexing the frame
    laterally on the downstroke, but that I get most of this stored energy back on the upstroke of the
    same pedal as the flexed frame returns to its unstressed center position?

    Sorry, that was my mistake. See other post. The frame absorbs a little energy in the early part of
    a stroke, and releases it in the later part, as your power decreases. Its only of theoretical
    interest really.

    Quoted message said:

    If so, I'm worried about what the other pedal is doing and where the frame is flexing on its
    downstroke.

    If you are riding hard, the other foot is pulling up and adding to the flex.

    Quoted message said:

    Is the frame bending sideways slowly through each downstroke and then snapping back to the center
    position much more quickly (a

    no. no snapping.

  14. Chalo <[email hidden]> scribed in
    <[email hidden]>:

    Quoted message said:

    classicrendezvous.comPMP main.htm

    ROFLMAO!

    Quoted message said:

    classicrendezvous.comRIGI main.htm

    well, nice if you want a shorter bike that you can't ride nohands

    swarf, steam and wind

    --
    David Forsyth -:- the email address is real /"\ terrapin.ru.ac.zawelcome.html \
    / ASCII Ribbon campaign against HTML E-Mail > - - - - - - -> X If you receive email saying
    "Send this to everyone you know," / \ PLEASE pretend you don't know me.

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

    [snip]

    Dear Jobst,

    To paraphrase a movie that I missed, you had me at the tetrahedron.

    The rest of your explanation of how the rear frame works was just as nice, so clear that I could
    half-close my innumerate eyes and fondly imagine that I followed the final cosines (I have to take
    that stuff for granted).

    This is the kind of comment that I was hoping for, something that explains why the odd Colnago
    chain-stays are unlikely to be practical.

    Thanks,

    Carl Fogel

  16. Carl Fogel said:

    This is the kind of comment that I was hoping for, something that explains why the odd Colnago
    chain-stays are unlikely to be practical.

    It's not particularly that they would be impractical, no more than the ridges they put on the main
    tubes, or any of their other marketing gimmicks. But they offer no advantage, so are just tail fins.
    (I even have a car with tail fins, too.)

    --

    David L. Johnson

    __o | "What am I on? I'm on my bike, six hours a day, busting my ass. _`\(,_ | What are you on?"
    --Lance Armstrong (_)/ (_) |

  17. Peter Cole said:

    In an episode of "Scientific American Frontiers"

    pbs.org1309 1.htm

    "In his course called "How to Make (Almost) Anything," Gershenfeld's students fabricate tangible
    objects from the plans they design on computers, using computer-controlled machines to cut through
    materials ranging from plastic to steel. Alan tries out a one-of-a-kind bicycle made by one
    student based on a model of Matisse's Blue Nude Number Two."

    Check these bikes made out of Lexan on a laser cutter:

    web.media.mit.eduicycle.htm web.media.mit.eduparts.htm

    That's certainly not "proper" materials, but it's cool as all get-out.

    Chalo Colina

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