Road Cycling · Public discussion

Re: Bicycle dynamics vs. motorcycle dynamics

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Road Cycling
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5 June 2005
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  1. Just zis Guy, you know? wrote, in response to:

    Quoted message said:


    Quoted message said:
    Quoted message said:

    I wonder if difficulty with weighting the wheels
    has anything to do with some recumbent bicycle designs
    being rather sluggish on upslopes?

    Quoted message said:

    Nope, it's being unable to stand.

    Nope, it's partly blood flow dynamics and partly the weight of the
    bike. The ability to stand is more than offset by the ability to push
    against the seat, giving tractive effort greater than your mass alone
    would allow.

    I'm not sure about that last idea. Yes, you can get more force out of
    your legs than your weight, and a recumbent gives you the chance to do
    that.

    But ISTM that on an upright, climbing when standing, you're bringing
    many more muscles into play. I believe I use my arms, etc. to
    partially lift my weight, which I then "deposit" onto the upper pedal.
    I thus put some work done by upper body into forward propulsion.

    It's obvious to me I can do this even when my quads are so fatigued I
    can barely pedal uphill seated, so there's _something_ contributing
    beyond what my quads can produce.

    Quoted message said:

    A lightweight recumbent with a fit rider can climb every bit as well
    as a wedgie (e.g. the hill climb contest at last year's Cyclefest
    which was won by Howard on a recumbent trike with a chainwheel the
    size of a dustbin lid, against a field which included lightweight
    spaceframe Moultons and other uprights).

    This may be true for the very lightest recumbents, but certainly not
    for most of them. And part of the gain may be aerodynamics (depending
    which way the wind was blowing that day). I was surprised when I
    noticed that even a slight breeze still makes a detectable difference
    climbing the hill on my way home. The slope in the steeper parts runs
    from about 5% to 10%, so I'm not moving fast; but a tailwind still
    helps!

    - Frank Krygowski

  2. At 5 Jun 2005 11:56:45 -0700, message
    <[email hidden]> was posted by
    [email hidden], including some, all or none of the following:

    Quoted message said:
    Quoted message said:

    Nope, it's partly blood flow dynamics and partly the weight of the
    bike. The ability to stand is more than offset by the ability to push
    against the seat, giving tractive effort greater than your mass alone
    would allow.

    Quoted message said:

    ISTM that on an upright, climbing when standing, you're bringing
    many more muscles into play. I believe I use my arms, etc. to
    partially lift my weight, which I then "deposit" onto the upper pedal.
    I thus put some work done by upper body into forward propulsion.

    I don't think you put in any meaningful amount of effort through these
    mechanisms. And that's before we even get into the issues of
    differential strength (I can easily leg press several times my own
    weight, which is far more than I can manage with any arm weight
    exercise).

    Quoted message said:

    It's obvious to me I can do this even when my quads are so fatigued I
    can barely pedal uphill seated, so there's _something_ contributing
    beyond what my quads can produce.

    Change of posture - different muscle recruitment. That is an issue on
    a 'bent, and it's one reason you have to build up your 'bent legs,
    because you can't recruit other muscles as they fatigue.

    Quoted message said:
    Quoted message said:

    A lightweight recumbent with a fit rider can climb every bit as well
    as a wedgie (e.g. the hill climb contest at last year's Cyclefest
    which was won by Howard on a recumbent trike with a chainwheel the
    size of a dustbin lid, against a field which included lightweight
    spaceframe Moultons and other uprights).

    Quoted message said:

    This may be true for the very lightest recumbents, but certainly not
    for most of them. And part of the gain may be aerodynamics (depending
    which way the wind was blowing that day).

    The former - up to a point. I believe Howard's trike weighs in at
    well over 30lb, which is heavy for a bike and much heavier than the
    25lb Moulton. In any case, I weigh 180lb, so a couple of lb on the
    bike is hardly going to make a big difference. The latter - not on a
    hill-climb race (Deliberately steep hill), I think. And it was, if I
    recall correctly, a flat calm that evening.

    Quoted message said:

    I was surprised when I
    noticed that even a slight breeze still makes a detectable difference
    climbing the hill on my way home. The slope in the steeper parts runs
    from about 5% to 10%, so I'm not moving fast; but a tailwind still
    helps!

    Why do you think I bought the recumbent? ;-)

    Guy
    --
    May contain traces of irony. Contents liable to settle after posting.
    http://www.chapmancentral.co.uk

    85% of helmet statistics are made up, 69% of them at CHS, Puget Sound

  3. Just zis Guy said:

    At 5 Jun 2005 11:56:45 -0700, message
    <[email hidden]> was posted by
    [email hidden], including some, all or none of the following:

    Quoted message said:

    ISTM that on an upright, climbing when standing, you're bringing
    many more muscles into play. I believe I use my arms, etc. to
    partially lift my weight, which I then "deposit" onto the upper pedal.
    I thus put some work done by upper body into forward propulsion.

    I don't think you put in any meaningful amount of effort through these
    mechanisms. And that's before we even get into the issues of
    differential strength (I can easily leg press several times my own
    weight, which is far more than I can manage with any arm weight
    exercise).

    Quoted message said:

    It's obvious to me I can do this even when my quads are so fatigued I
    can barely pedal uphill seated, so there's _something_ contributing
    beyond what my quads can produce.

    Change of posture - different muscle recruitment.

    "Different muscle recruitment" is, I think, short for what I described!

    - Frank Krygowski

  4. At 5 Jun 2005 13:50:20 -0700, message
    <[email hidden]> was posted by
    [email hidden], including some, all or none of the following:

    Quoted message said:

    "Different muscle recruitment" is, I think, short for what I described!

    Not really; they are still leg muscles. I can get more effort on a
    'bent (I can get wheelspin on the flat in some circumstances).

    Guy
    --
    May contain traces of irony. Contents liable to settle after posting.
    http://www.chapmancentral.co.uk

    85% of helmet statistics are made up, 69% of them at CHS, Puget Sound

  5. Just zis Guy said:

    At 5 Jun 2005 13:50:20 -0700, message
    <[email hidden]> was posted by
    [email hidden], including some, all or none of the following:

    Quoted message said:

    "Different muscle recruitment" is, I think, short for what I described!

    Not really; they are still leg muscles. I can get more effort on a
    'bent (I can get wheelspin on the flat in some circumstances).

    OK. I think I'm recruiting other muscles besides leg muscles.

    - Frank Krygowski

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