mavic rims don't *all* suck

Discussion in 'Cycling Equipment' started by Dvt, Feb 26, 2004.

  1. Jim Beam

    Jim Beam Guest

    G.T. wrote:
    > jim beam wrote:
    >
    <snip>
    >>
    >> i may be wrong, but i doubt /any/ rim is hooped after
    >> anodizing. anodizing is too brittle and the bending will
    >> expose unprotected metal. completely defeats the point.
    >>
    >
    > Anodizing defeats the point in the first place. Do you
    > really think manufacturers that promote anodization would
    > do it the right way?

    we seem to disagree on the value of anodizing! yes, i think
    most manufacturers would know how to do it right. there may
    be exceptions of course, but i honestly doubt that a long
    established company would suddenly decide to jeopardize
    their business by doing something /known/ to be a problem -
    which bending after anodizing would be.

    >
    > The extrusion is usually anodized first in a long tank.

    istr you mentioning this before, but for welded rims like
    mavic open pros, i don't see how it can be. the weld zone is
    clearly anodized after it's been smoothed off. are you
    certain the long tanks weren't for chemically cleaning the
    extrusion lube off?
     


  2. G.T.

    G.T. Guest

    jim beam wrote:
    > G.T. wrote:
    >
    >> jim beam wrote:
    >>
    > <snip>
    >
    >>>
    >>> i may be wrong, but i doubt /any/ rim is hooped after
    >>> anodizing. anodizing is too brittle and the bending will
    >>> expose unprotected metal. completely defeats the point.
    >>>
    >>
    >> Anodizing defeats the point in the first place. Do you
    >> really think manufacturers that promote anodization would
    >> do it the right way?
    >
    >
    > we seem to disagree on the value of anodizing!

    I assume that means you think anodizing has some value other
    than to promote rim sales because of premature cracking?

    >
    >>
    >> The extrusion is usually anodized first in a long tank.
    >
    >
    > istr you mentioning this before, but for welded rims like
    > mavic open pros, i don't see how it can be. the weld zone
    > is clearly anodized after it's been smoothed off. are you
    > certain the long tanks weren't for chemically cleaning the
    > extrusion lube off?

    This was at Sun quite some time before welded rims. I
    probably shouldn't have generalized to Mavic.

    Greg
     
  3. Matt O'Toole

    Matt O'Toole Guest

    dianne_1234 wrote:

    > I meant that a single die may have multiple ports that
    > produce several linear extrusions in one push. These multi-
    > hole dies may have holes that produce variation in walls
    > from one port to the next.

    I guess it's possible. However, all the machines I've seen
    squirt through just one die.

    Matt O.
     
  4. Matt O'Toole

    Matt O'Toole Guest

    carlfogel wrote:

    > I haven't looked into the matter yet, since the original
    > question was whether unanodized and clear/hard anodized
    > rims weighed exactly the same, but what effect do you
    > predict hard anodizing has on a rim's rigidity?
    > Significantly less rigid, a tiny bit less rigid, no
    > effect at all, a tiny bit more rigid, or significantly
    > more rigid?

    Read Jobst's explanation again, in the part of this thread
    where he calls the rigidity claim a "lie of the second
    kind." Therein lies the truth.

    Matt O.
     
  5. Carl Fogel

    Carl Fogel Guest

    "Matt O'Toole" <[email protected]> wrote in message news:<[email protected]>...
    > carlfogel wrote:
    >
    > > I haven't looked into the matter yet, since the original
    > > question was whether unanodized and clear/hard anodized
    > > rims weighed exactly the same, but what effect do you
    > > predict hard anodizing has on a rim's rigidity?
    > > Significantly less rigid, a tiny bit less rigid, no
    > > effect at all, a tiny bit more rigid, or significantly
    > > more rigid?
    >
    > Read Jobst's explanation again, in the part of this thread
    > where he calls the rigidity claim a "lie of the second
    > kind." Therein lies the truth.
    >
    > Matt O.

    Dear Matt,

    Calling people liars is rarely as useful as Jobst imagines,
    particularly in technical matters, where it's often done in
    a spirit of self-congratulatory self-flattery.

    Again, how much rigidity do you predict? Jobst said
    significant, but gave no numbers, and then argued that it
    vanishes the moment a load is put on the wheel.

    It's a harder question to answer than it looks, since
    anodizing is so thin and rims are such an odd shape.

    So how much rigidity vanishes? (Assuming that the theory is
    correct and that rigidity both exists and then vanishes.)

    Does a 20% increase in rim rigidity disappear? Or 10%, 5%,
    1%? I'm always curious about theories presented as
    incontrovertible facts where the numbers seem to be missing.
    (Think of spoke tying and soldering, where a widely accepted
    theory didn't survive the results of Jobst's testing.)

    I'm not arguing against the theories about rim rigidity,
    just wondering what the numbers are, which would indicate
    that the theories had been tested. You know, the kind of
    curiosity expected in any high-school science class, where
    calling people liars is rarely used as an argument.

    Carl Fogel
     
  6. Rick Onanian

    Rick Onanian Guest

    On 8 Mar 2004 11:05:12 -0800, [email protected] (Carl Fogel)
    wrote:
    >Again, how much rigidity do you predict? Jobst said
    >significant, but gave no numbers, and then argued that it
    >vanishes the moment a load is put on the wheel.
    >
    >So how much rigidity vanishes? (Assuming that the theory is
    >correct and that rigidity both exists and then vanishes.)
    >
    >Does a 20% increase in rim rigidity disappear? Or 10%,

    I think the issue isn't rim rigidity at all. Who cares
    how rigid a rim is? _Wheel_ rigidity is what matters,
    which is why rim rigidity seems to "disappear". A
    tensioned spoked bicycle wheel is definitely much more
    than the sum of it's parts.

    I bet if I took a Mavic CXP-21 rim off my bike (and off it's
    spokes and hub), I could crush it easily with just part of
    my weight (even with an inflated tire on it, if possible).
    The same rim, however, can rigidly survive high-speed
    potholes, bumps, and bunny hops (when I see the bump before
    I hit it) repeatedly, when built into a wheel.

    I therefore submit that the rigidity of a quality modern
    lightweight rim has such an insignificant effect on the
    rigidity of the wheel that it is effectively zero. The
    exception being that a more rigid rim could conceivably
    make it easier to build the wheel strongly, as it
    tolerates higher uneven spoke tensions as you go around
    tightening spokes.

    Speaking of revolving circular things...is this thread going
    around in circles?
    --
    Rick Onanian
     
  7. Jim Beam

    Jim Beam Guest

    G.T. wrote:
    > jim beam wrote:
    >
    >> G.T. wrote:
    >>
    >>> jim beam wrote:
    >>>
    >> <snip>
    >>
    >>>>
    >>>> i may be wrong, but i doubt /any/ rim is hooped after
    >>>> anodizing. anodizing is too brittle and the bending
    >>>> will expose unprotected metal. completely defeats the
    >>>> point.
    >>>>
    >>>
    >>> Anodizing defeats the point in the first place. Do you
    >>> really think manufacturers that promote anodization
    >>> would do it the right way?
    >>
    >>
    >>
    >> we seem to disagree on the value of anodizing!
    >
    >
    > I assume that means you think anodizing has some value
    > other than to promote rim sales because of premature
    > cracking?

    yes. corrosion protection and in the case of "cd" rims, wear
    resistance.

    i don't dispute that marketing hype is frequently
    implausible rubbish, but since when did the sales droids
    ever connect with the nerd in the back room that did the
    /real/ design work? i say give the nerd a break.

    >
    >>
    >>>
    >>> The extrusion is usually anodized first in a long tank.
    >>
    >>
    >>
    >> istr you mentioning this before, but for welded rims like
    >> mavic open pros, i don't see how it can be. the weld zone
    >> is clearly anodized after it's been smoothed off. are you
    >> certain the long tanks weren't for chemically cleaning
    >> the extrusion lube off?
    >
    >
    > This was at Sun quite some time before welded rims. I
    > probably shouldn't have generalized to Mavic.
    >
    > Greg
     
  8. Almost Fast

    Almost Fast Guest

    jim beam <[email protected]> wrote in message news:<[email protected]>...
    > from what i understand, for extruded meatals, you only
    > have one port per extrusion because the microstructure of
    > the "in" affects the microstructure of the "out". just
    > like a striped toothpaste tube - if you had multiple outs,
    > you'd have a real hard time making sure they all extruded
    > the same stripes in the same way. and consistency of
    > output is essential.
    >
    > dianne_1234 wrote:
    > > I meant that a single die may have multiple ports that
    > > produce several linear extrusions in one push. These multi-
    > > hole dies may have holes that produce variation in walls
    > > from one port to the next.

    Perhaps some failed rims that display unexpected fracture
    surfaces came from rim makers who didn't care to insist on
    single port dies?
     
  9. Carl Fogel

    Carl Fogel Guest

    dianne_1234 <[email protected]> wrote in message news:<[email protected]>...
    > On 6 Mar 2004 17:24:22 -0800, [email protected] (Carl
    > Fogel) wrote:
    >
    > >But his tables show no drillings,
    >
    > Campagnolo's catalog several years ago listed weights,
    > with the footnote that every spoke hole added 1.4 grams
    > for rims with ferrules (or whatever word they used). IIRC,
    > these were for rims with sockets and eyelets.
    >
    > So variation in rim weight (due to hole count) between 32
    > and 36 hole rims might be on the order of 4 * 1.4 = 5.6
    > grams, with the 36 hole rim weighing more than the 32
    > hole rims.
    >
    > When was the last time you saw a 28 hole MA2? I suspect
    > most rim weights are quoted for either 32 or 36 holes.

    Dear Dianne,

    Sorry for the delayed reply--I've lost track of a few
    threads.

    Your 28-hole question puzzled me at first, so I wondered
    whether I'd somehow mistakenly typed 28-hole somewhere. Then
    I realized that I must have mentioned the three drilling
    patterns without specifying them.

    Here are the BikePro table's MA 2 hole-patterns and weights:

    32 464.0 36 473.5 40 485.5

    http://www.bikepro.com/products/rims/rimtables.html

    The 40 hole was probably for clydesdales or tandems. I
    don't know of any 28-hole versions, though I suppose that
    very late models might have dropped to the newer and fewer
    spoke count.

    Just above the MA 2 entry, the Campagnolo Atek shows a 28-32-
    36 pattern, so reduced spoke counts were becoming available.

    Just below the MA 2 entry, the Mavic Module 4 shows a 36-40-
    48 pattern, the first two weighing in at 539 and 571.5
    grams, which suggests tandem.

    I think that we're in agreement that the weight of the four
    eyelet pieces may account for the listed 10-gram weight
    gain. Several posts (including yours) have added what seem
    to me to be increasingly plausible claims that the rims vary
    more than I originally thought as the dies wear--which, if
    I'd bothered to remember what I'd read, was also mentioned
    in the BikePro rim overview page.

    I'm still a bit shocked by the idea of 450 gram rims varying
    almost 40 grams according to the day that they were
    extruded, but that and the weight gain of four eyelets seems
    to be the most likely explanation for a range of claimed
    weights that would cause eyebrows to raise at a
    WeightWatchers meeting.

    Carl Fogel
     
  10. Jim Beam

    Jim Beam Guest

    from what i know, multiport extrusion is limited to material
    much nearer its liquid state than is aluminum extrusion
    which is done at raised temperature, but is still definitely
    solid. i would therefore expect to see /all/ aluminum rim
    extruders be single port.

    but i wouldn't have expected to see rims anodized /before/
    hooping, but it would appear that some are, so what do i
    know? you definitely have a point!

    almost fast wrote:
    > jim beam <[email protected]> wrote in message news:<DzM2c.35247-
    > [email protected]>...
    >
    >>from what i understand, for extruded meatals, you only
    >>have one port per extrusion because the microstructure of
    >>the "in" affects the microstructure of the "out". just
    >>like a striped toothpaste tube - if you had multiple outs,
    >>you'd have a real hard time making sure they all extruded
    >>the same stripes in the same way. and consistency of
    >>output is essential.
    >>
    >>dianne_1234 wrote:
    >>
    >>>I meant that a single die may have multiple ports that
    >>>produce several linear extrusions in one push. These multi-
    >>>hole dies may have holes that produce variation in walls
    >>>from one port to the next.
    >
    >
    > Perhaps some failed rims that display unexpected fracture
    > surfaces came from rim makers who didn't care to insist on
    > single port dies?
     
  11. Jim Beam

    Jim Beam Guest

    from what i know, multiport extrusion is limited to material
    much nearer its liquid state than is aluminum extrusion
    which is done at raised temperature, but is still definitely
    solid. i would therefore expect to see /all/ aluminum rim
    extruders be single port.

    but i wouldn't have expected to see rims anodized /before/
    hooping, but it would appear that some are, so what do i
    know? you definitely have a point!

    almost fast wrote:
    > jim beam <[email protected]> wrote in message news:<DzM2c.35247-
    > [email protected]>...
    >
    >>from what i understand, for extruded meatals, you only
    >>have one port per extrusion because the microstructure of
    >>the "in" affects the microstructure of the "out". just
    >>like a striped toothpaste tube - if you had multiple outs,
    >>you'd have a real hard time making sure they all extruded
    >>the same stripes in the same way. and consistency of
    >>output is essential.
    >>
    >>dianne_1234 wrote:
    >>
    >>>I meant that a single die may have multiple ports that
    >>>produce several linear extrusions in one push. These multi-
    >>>hole dies may have holes that produce variation in walls
    >>>from one port to the next.
    >
    >
    > Perhaps some failed rims that display unexpected fracture
    > surfaces came from rim makers who didn't care to insist on
    > single port dies?
     
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