Wheelbuilding wisdom for the novice

Discussion in 'Road Cycling' started by Mrbubl, Jun 20, 2003.

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  1. Marcus Coles

    Marcus Coles Guest

    archer wrote:
    > In article <[email protected]>, [email protected] says...
    >
    >>I'll risk this question: The finite element analysis referred to in this thread uses a rim that is
    >>25mm wide and 10mm tall in cross-section. The resulting analysis identifies rim deformation at the
    >>contact zone as the source of tension changes in the spokes. The rims on my bike have
    >>cross-section dimensions of 17mm wide and 35mm tall. Assuming the rims are made of similar
    >>material (aluminium alloy), and all other factors constant (tire, tire pressure, etc.) can I
    >>expect a similar analysis to show less compression (reduction in tension) in the lower spokes on
    >>my loaded rim compared to the one in the example analysis?
    >
    >
    > This is out of my main area of expertise, but I do have a little experience and training in the
    > subject, and I'm never afraid of offering an opinion <Grin>, so here goes: I would expect that,
    > since your rim has a larger box section than the one used in the calculations, that it wouldn't
    > flex quite as much. If that assumption is correct, then I would expect that it wouldn't have as
    > large of an effect on the tension in the bottom spokes. And then you should see a somewhat larger
    > increase in tension in the upper spokes.
    >
    >
    Dangerous ground around here.

    Care to offer an opinion on what happens with the heavy steel rim and "loose" spokes on most of the
    world's bicycles?

    I could not resist ;-)

    Marcus
     


  2. Archer

    Archer Guest

    In article <[email protected]>, [email protected] says...
    > archer wrote:
    > > In article <[email protected]>, [email protected] says...
    > >
    > >>I'll risk this question: The finite element analysis referred to in this thread uses a rim that
    > >>is 25mm wide and 10mm tall in cross-section. The resulting analysis identifies rim deformation
    > >>at the contact zone as the source of tension changes in the spokes. The rims on my bike have
    > >>cross-section dimensions of 17mm wide and 35mm tall. Assuming the rims are made of similar
    > >>material (aluminium alloy), and all other factors constant (tire, tire pressure, etc.) can I
    > >>expect a similar analysis to show less compression (reduction in tension) in the lower spokes on
    > >>my loaded rim compared to the one in the example analysis?
    > >
    > >
    > > This is out of my main area of expertise, but I do have a little experience and training in the
    > > subject, and I'm never afraid of offering an opinion <Grin>, so here goes: I would expect that,
    > > since your rim has a larger box section than the one used in the calculations, that it wouldn't
    > > flex quite as much. If that assumption is correct, then I would expect that it wouldn't have as
    > > large of an effect on the tension in the bottom spokes. And then you should see a somewhat
    > > larger increase in tension in the upper spokes.
    > >
    > >
    > Dangerous ground around here.
    >
    > Care to offer an opinion on what happens with the heavy steel rim and "loose" spokes on most of
    > the world's bicycles?
    >
    > I could not resist ;-)

    Since you ask a rather generic question (define "heavy" and "loose" as they relate to bicycles),
    I'll give you a _very_ generic answer: The same basic type of effects, but of a differing (either
    greater or lesser) amount. How's that for a non-answer <GGGG>?

    --
    David Kerber An optimist says "Good morning, Lord." While a pessimist says "Good Lord,
    it's morning".

    Remove the ns_ from the address before e-mailing.
     
  3. Marcus Coles

    Marcus Coles Guest

    archer wrote:

    >>
    >>Dangerous ground around here.
    >>
    >>Care to offer an opinion on what happens with the heavy steel rim and "loose" spokes on most of
    >>the world's bicycles?
    >>
    >>I could not resist ;-)
    >
    >
    > Since you ask a rather generic question (define "heavy" and "loose" as they relate to bicycles),
    > I'll give you a _very_ generic answer: The same basic type of effects, but of a differing (either
    > greater or lesser) amount. How's that for a non-answer <GGGG>?
    >
    >
    Nobody likes this one.

    How about a nice 3-1/2 lb, 3/4" deep, 622mm steel rim and spokes that go dong as opposed to ping
    when plucked.

    I do have a rideable antique bicycle similar to this, it gets about 10 miles of use a week for the
    past 6 years. Other than tires and lubrication it remains as found. The tires are 1 1/2" wide and
    inflated to 45psi. The 36 spokes are locked to the nipples by corrosion, and will probably
    eventually fail from lost material due to rust. Despite frequent curb drops the wheels appear
    straight with no hops. A complete front wheel and tire tips the scales at over 6-1/2 lb.

    To me it represents the other side of the coin when it comes to bicycle wheels and probably is
    closer to what one finds throught the unenlightened world than the MA2 rimmed model.

    My spoke plucking suggests a hanging hub, but I may be tone deaf and I have been called a liar
    before when I brought this up. So I suggest the doubters find a rusty old utility bicycle in a barn,
    sit a fat friend on it and start plucking.

    BTW most of my bicycles have box or mild aero aluminum alloy rims and plucking those spokes seems to
    fit the model that is widely accepted in this group.

    Marcus
     
  4. On Tue, 24 Jun 2003 20:26:15 -0400, Marcus Coles <[email protected]> wrote:

    >How about a nice 3-1/2 lb, 3/4" deep, 622mm steel rim and spokes that go dong as opposed to ping
    >when plucked.
    ..
    >My spoke plucking suggests a hanging hub, but I may be tone deaf and I have been called a liar
    >before when I brought this up. So I suggest the doubters find a rusty old utility bicycle in a
    >barn, sit a fat friend on it and start plucking.

    Sit a fat enough friend on it (ie, me) for a couple dozen miles and watch the spoke heads come
    flying off.

    Jasper
     
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