QBP wheels

Discussion in 'Cycling Equipment' started by Zruk, Jan 18, 2008.

  1. Zruk

    Zruk Guest

    If at first... Does anyone know for a fact whether QBP wheels are
    stress relieved. ... the facts please just give us the facts...dum de
    dum dum dumm
     
    Tags:


  2. Jay Beattie

    Jay Beattie Guest

    On Jan 18, 12:19 pm, Zruk <stank...@gmail.com> wrote:
    > If at first... Does anyone know for a fact whether QBP wheels are
    > stress relieved. ... the facts please just give us the facts...dum de
    > dum dum dumm


    To answer your question . . . no, I don't know if QBP stress relieves
    its wheels, but wheel "stabilization" (mechanical spoke squeezing) is
    a feature available on at least some wheel building machines. See
    http://www.bmd.nl/pages/products/wheel-stabiliser . I guess the
    question is what machine QBP uses. -- Jay Beattie.
     
  3. On Fri, 18 Jan 2008 12:19:25 -0800 (PST), Zruk <stankurz@gmail.com>
    wrote:

    >If at first... Does anyone know for a fact whether QBP wheels are
    >stress relieved. ... the facts please just give us the facts...dum de
    >dum dum dumm


    Dear Stan,

    Of course someone knows . . .

    http://www.qbp.com/contact.html

    You can pay for the phone call or try email first.

    Like most mass wheel suppliers, they just don't think that it's worth
    mentioning, one way or another.

    Cheers,

    Carl Fogel
     
  4. Ben C

    Ben C Guest

    On 2008-01-18, jobst.brandt@stanfordalumni.org <jobst.brandt@stanfordalumni.org> wrote:
    > Jay Beattie writes:
    >
    >>> If at first... Does anyone know for a fact whether QBP wheels are
    >>> stress relieved. ... the facts please just give us the facts...dum
    >>> de dum dum dumm

    >
    >> To answer your question... no, I don't know if QBP stress relieves
    >> its wheels, but wheel "stabilization" (mechanical spoke squeezing)
    >> is a feature available on at least some wheel building machines.

    >
    > http://www.bmd.nl/pages/products/wheel-stabiliser
    >
    >> I guess the question is what machine QBP uses.

    >
    > That's an interesting description of what "stabilizing" is and how it
    > makes durable wheels. No mention of spoke failure appears there and
    > how this process, that is applied at low tension works.


    Well it says lack of stabilization can result in "an untrue wheel or
    early failure of the wheel".

    Early failure could mean spokes breaking.

    There is a hint about how the process is supposed to work: "This force
    sets the spoke elbows in the flange holes of the hub and the nipples in
    the rim".

    The idea that setting the spoke elbows in the flange is one of the
    benefits of spoke-squeezing, crank-wrenching or wood-block-leaning-on is
    not new and has been discussed here before.

    > I see "stress relief" is a bugaboo much like the word "tensiometer"
    > with all its circumlocutions among most wheel building people.


    I don't like calling the process "stress relief".

    It appears to be something that wheelbuilders have been doing for years
    under a variety of completely different and usually unsubstantiated
    theories of why and how it works.

    Out of those theories, relieving residual stress is one, and not one for
    which any convincing evidence has been produced.

    It would be clearer to find a name more descriptive of the process than
    of any particular theory of its underlying mechanism. Actually
    "stabilization" is not too bad a word for it, and better than having to
    say "stress-relief" in quotes with a disclaimer that residual stress may
    not have anything to do with it.

    Tensiometer on the other hand is just a fancy word for "tension gauge".
    I have no problem with it.
     
  5. Ben C? writes:

    >>>> If at first... Does anyone know for a fact whether QBP wheels are
    >>>> stress relieved. ... the facts please just give us the
    >>>> facts...dum de dum dum dumm


    >>> To answer your question... no, I don't know if QBP stress relieves
    >>> its wheels, but wheel "stabilization" (mechanical spoke squeezing)
    >>> is a feature available on at least some wheel building machines.


    http://www.bmd.nl/pages/products/wheel-stabiliser

    >>> I guess the question is what machine QBP uses.


    >> That's an interesting description of what "stabilizing" is and how
    >> it makes durable wheels. No mention of spoke failure appears there
    >> and how this process, that is applied at low tension works.


    > Well it says lack of stabilization can result in "an untrue wheel or
    > early failure of the wheel".


    > Early failure could mean spokes breaking.


    > There is a hint about how the process is supposed to work: "This
    > force sets the spoke elbows in the flange holes of the hub and the
    > nipples in the rim".


    > The idea that setting the spoke elbows in the flange is one of the
    > benefits of spoke-squeezing, crank-wrenching or
    > wood-block-leaning-on is not new and has been discussed here before.


    Spoke alignment is not improved by stress relief, the macro part of
    the spoke being unaffected by these various ways of increasing
    tension. The only effect it has is to yield those areas (that are
    microscopic) that have high residual stress, the cause of spoke
    fatigue failure.

    >> I see "stress relief" is a bugaboo much like the word "tensiometer"
    >> with all its circumlocutions among most wheel building people.


    > I don't like calling the process "stress relief".


    Why? That's the only thing it does. If you measure spoke tension
    when performing this process, you'll notice that tension does not rise
    enough to change the bend of an elbow or the alignment of a spoke into
    the spoke nipple. As I said, it strikes me that people avoid these
    words, stress relief and tensiometer, possibly because the fear verbal
    retribution by the persistent attackers of anything I have written.

    > It appears to be something that wheelbuilders have been doing for
    > years under a variety of completely different and usually
    > unsubstantiated theories of why and how it works.


    Why is yield of high stress points with increased tension a mystery
    and why do spokes fail if it is not from residual high stress at
    inflexion points?

    > Out of those theories, relieving residual stress is one, and not one
    > for which any convincing evidence has been produced.


    Oh? Then why do spokes break in fatigue there if the stress in those
    points is not near yield? It is exactly that effect by which manual
    stress relief is possible without otherwise affecting the wheel.
    Mechanical stress relief is best visible on a wavy spoke that is taken
    to yield in a tensile tester. The spoke comes out perfectly straight.
    I think I have explained how bending a steel wire enough to make it
    take a set works. It always results in residual stress. this is
    apparent with thermal stress relief because that causes a change in
    shape unless the work piece is restrained... which it most often is in
    such procedures.

    > It would be clearer to find a name more descriptive of the process
    > than of any particular theory of its underlying mechanism. Actually
    > "stabilization" is not too bad a word for it, and better than having
    > to say "stress-relief" in quotes with a disclaimer that residual
    > stress may not have anything to do with it.


    Why not call it "smoothing" or "stroking". Stress relief is its
    purpose and stress relief is what it produces.

    > Tensiometer on the other hand is just a fancy word for "tension
    > gauge". I have no problem with it.


    Look it up in the dictionary. It is like any other tool. It has a
    name. We also call them pliers, not a "two jawed scissors holding
    device." But it's not that, it's that most choose to call it a
    "tensionometer", a word not found in Webster's. They seem to not use
    the proper term to avoid being attacked by anonymous rude contributors
    to this forum, as you must have seen.

    Jobst Brandt
     
  6. Tom Sherman

    Tom Sherman Guest

    jobst.brandt@stanfordalumni.org aka Jobst Brandt wrote:
    > Ben C? writes:
    >
    > ...
    >> Tensiometer on the other hand is just a fancy word for "tension
    >> gauge". I have no problem with it.

    >
    > Look it up in the dictionary. It is like any other tool. It has a
    > name. We also call them pliers, not a "two jawed scissors holding
    > device." But it's not that, it's that most choose to call it a
    > "tensionometer", a word not found in Webster's. They seem to not use
    > the proper term to avoid being attacked by anonymous rude contributors
    > to this forum, as you must have seen.
    >

    Tension-O-meter works well for those nostalgic for 1950's marketing.

    --
    Tom Sherman - Holstein-Friesland Bovinia
    "And never forget, life ultimately makes failures of all people."
    - A. Derleth
     
  7. Zruk wrote:
    > If at first... Does anyone know for a fact whether QBP wheels are
    > stress relieved. ... the facts please just give us the facts...dum de
    > dum dum dumm


    The description page for the "Quality Wheelhouse" front wheel built with
    a Campy Centaur hub and Velocity Aerohead rim says:

    Features and Information
    Campy Centaur

    * Includes quick-release skewer
    * Wheels are built with DT Swiss spokes and nipples
    * Hand-trued, stress-relieved, dished, and tensioned to the highest
    industry standards
    * Weights do not include QR

    So, according to their product descriptions, the QBP wheels are
    stress-relieved. You can also try sending email to QBP directly by
    sending email to sales@qbp.com and asking the question.

    Hope this helps.

    Mike Johnson
     
  8. Ben C

    Ben C Guest

    On 2008-01-19, jobst.brandt@stanfordalumni.org <jobst.brandt@stanfordalumni.org> wrote:
    > Ben C? writes:

    [...]
    >> The idea that setting the spoke elbows in the flange is one of the
    >> benefits of spoke-squeezing, crank-wrenching or
    >> wood-block-leaning-on is not new and has been discussed here before.

    >
    > Spoke alignment is not improved by stress relief, the macro part of
    > the spoke being unaffected by these various ways of increasing
    > tension. The only effect it has is to yield those areas (that are
    > microscopic) that have high residual stress, the cause of spoke
    > fatigue failure.
    >
    >>> I see "stress relief" is a bugaboo much like the word "tensiometer"
    >>> with all its circumlocutions among most wheel building people.

    >
    >> I don't like calling the process "stress relief".

    >
    > Why? That's the only thing it does. If you measure spoke tension
    > when performing this process, you'll notice that tension does not rise
    > enough to change the bend of an elbow or the alignment of a spoke into
    > the spoke nipple.


    Oh? How much tension is needed to change the bend of an elbow?

    > As I said, it strikes me that people avoid these words, stress relief
    > and tensiometer, possibly because the fear verbal retribution by the
    > persistent attackers of anything I have written.


    Unlikely. You have to stop making this personal. What you write is very
    interesting and informative, but you can't expect people to just swallow
    everything.

    >> It appears to be something that wheelbuilders have been doing for
    >> years under a variety of completely different and usually
    >> unsubstantiated theories of why and how it works.

    >
    > Why is yield of high stress points with increased tension a mystery
    > and why do spokes fail if it is not from residual high stress at
    > inflexion points?


    Just because something is _possible_ doesn't mean it's necessarily what
    happens or what is significant.

    I shouldn't need to tell you that.

    There are plenty of reasons why spokes can fail: poor quality, poor
    surface finish and bad spoke line are top of my list as the _most
    likely_. But I don't have the evidence either so I make no further claim
    than that.

    >> Out of those theories, relieving residual stress is one, and not one
    >> for which any convincing evidence has been produced.

    >
    > Oh? Then why do spokes break in fatigue there if the stress in those
    > points is not near yield?


    They could be near yield because of bad spoke line rather than because
    of residual stress.

    You tell me: why does spoke fatigue ever start in regions of compressive
    residual stress if residual stress is the only factor here? Or do you
    deny that it does?

    [...]
    >> It would be clearer to find a name more descriptive of the process
    >> than of any particular theory of its underlying mechanism. Actually
    >> "stabilization" is not too bad a word for it, and better than having
    >> to say "stress-relief" in quotes with a disclaimer that residual
    >> stress may not have anything to do with it.

    >
    > Why not call it "smoothing" or "stroking". Stress relief is its
    > purpose and stress relief is what it produces.


    I actually think some people out there may be using the word "stress
    relief" in a completely different sense, to mean tension relief in order
    to unwind windup. That's why people are confused by the idea of
    stress-relief by spoke-squeezing since its purpose is to overload spokes
    not to momentarily reduce tension in them.

    >> Tensiometer on the other hand is just a fancy word for "tension
    >> gauge". I have no problem with it.

    >
    > Look it up in the dictionary.


    The dictionary tells me it's for measuring how damp soil is :)

    > It is like any other tool. It has a name. We also call them pliers,
    > not a "two jawed scissors holding device." But it's not that, it's
    > that most choose to call it a "tensionometer", a word not found in
    > Webster's. They seem to not use the proper term to avoid being
    > attacked by anonymous rude contributors to this forum, as you must
    > have seen.


    I really doubt that's the reason.
     
  9. Uneasy rests The Head that thinks it wears the crown:

    On Jan 18, 6:19 pm, jobst.bra...@stanfordalumni.org wrote:

    <snipped for clarity>

    > As I said, it strikes me that people avoid these
    > words, stress relief and tensiometer, possibly because the fear verbal
    > retribution by the persistent attackers of anything I have written.
    >


    < snip, snip, snip>


    > Look it up in the dictionary.  It is like any other tool.  It has a
    > name.  We also call them pliers, not a "two jawed scissors holding
    > device."  But it's not that, it's that most choose to call it a
    > "tensionometer", a word not found in Webster's.  They seem to not use
    > the proper term to avoid being attacked by anonymous rude contributors
    > to this forum, as you must have seen.
    >


    What happens when paranoia and megalomania meet?
     
  10. jim beam

    jim beam Guest

    jobst.brandt@stanfordalumni.org wrote:
    > Ben C? writes:
    >
    >>>>> If at first... Does anyone know for a fact whether QBP wheels are
    >>>>> stress relieved. ... the facts please just give us the
    >>>>> facts...dum de dum dum dumm

    >
    >>>> To answer your question... no, I don't know if QBP stress relieves
    >>>> its wheels, but wheel "stabilization" (mechanical spoke squeezing)
    >>>> is a feature available on at least some wheel building machines.

    >
    > http://www.bmd.nl/pages/products/wheel-stabiliser
    >
    >>>> I guess the question is what machine QBP uses.

    >
    >>> That's an interesting description of what "stabilizing" is and how
    >>> it makes durable wheels. No mention of spoke failure appears there
    >>> and how this process, that is applied at low tension works.

    >
    >> Well it says lack of stabilization can result in "an untrue wheel or
    >> early failure of the wheel".

    >
    >> Early failure could mean spokes breaking.

    >
    >> There is a hint about how the process is supposed to work: "This
    >> force sets the spoke elbows in the flange holes of the hub and the
    >> nipples in the rim".

    >
    >> The idea that setting the spoke elbows in the flange is one of the
    >> benefits of spoke-squeezing, crank-wrenching or
    >> wood-block-leaning-on is not new and has been discussed here before.

    >
    > Spoke alignment is not improved by stress relief, the macro part of
    > the spoke being unaffected by these various ways of increasing
    > tension. The only effect it has is to yield those areas (that are
    > microscopic) that have high residual stress, the cause of spoke
    > fatigue failure.
    >
    >>> I see "stress relief" is a bugaboo much like the word "tensiometer"
    >>> with all its circumlocutions among most wheel building people.

    >
    >> I don't like calling the process "stress relief".

    >
    > Why? That's the only thing it does.


    "stress relief" is metallurgical. you are presuming this to be the case
    but presenting no evidence. and given that the observed facts of
    fatigue initiation contradict this presumption, reality is, you're
    simply bullshitting because you don't know enough about this subject.


    > If you measure spoke tension
    > when performing this process, you'll notice that tension does not rise
    > enough to change the bend of an elbow or the alignment of a spoke into
    > the spoke nipple. As I said, it strikes me that people avoid these
    > words, stress relief and tensiometer, possibly because the fear verbal
    > retribution by the persistent attackers of anything I have written.


    "retribution" is pointing out your factual errors??? jobst, you need
    therapy. or to stop bullshitting.


    >
    >> It appears to be something that wheelbuilders have been doing for
    >> years under a variety of completely different and usually
    >> unsubstantiated theories of why and how it works.

    >
    > Why is yield of high stress points with increased tension a mystery
    > and why do spokes fail if it is not from residual high stress at
    > inflexion points?


    jeepers - how many more times do you need to be told? the elbow is
    offset from the spoke axis. when loaded, it bends. end of story!

    presumptive nonsense about "residual stress", something you read about
    50 years ago, briefly, and have not bothered to research since, is both
    asinine and offensive.



    >
    >> Out of those theories, relieving residual stress is one, and not one
    >> for which any convincing evidence has been produced.

    >
    > Oh? Then why do spokes break in fatigue there if the stress in those
    > points is not near yield?


    1. fatigue occurs well below yield. that is a fundamental error on your
    part.
    2. they fatigue because of /applied/ stress, not residual. get out the
    microscope and observe the facts.

    > It is exactly that effect by which manual
    > stress relief is possible without otherwise affecting the wheel.
    > Mechanical stress relief is best visible on a wavy spoke that is taken
    > to yield in a tensile tester. The spoke comes out perfectly straight.
    > I think I have explained how bending a steel wire enough to make it
    > take a set works. It always results in residual stress. this is
    > apparent with thermal stress relief because that causes a change in
    > shape unless the work piece is restrained... which it most often is in
    > such procedures.


    rubbish.


    >
    >> It would be clearer to find a name more descriptive of the process
    >> than of any particular theory of its underlying mechanism. Actually
    >> "stabilization" is not too bad a word for it, and better than having
    >> to say "stress-relief" in quotes with a disclaimer that residual
    >> stress may not have anything to do with it.

    >
    > Why not call it "smoothing" or "stroking". Stress relief is its
    > purpose and stress relief is what it produces.


    it beds the spokes n and this, to use the word introduced to this thread
    earlier, "stabilizes" the structure. you want your wheels to remain
    true first and foremost. fatigue can be cured by design or materials.


    >
    >> Tensiometer on the other hand is just a fancy word for "tension
    >> gauge". I have no problem with it.

    >
    > Look it up in the dictionary. It is like any other tool. It has a
    > name. We also call them pliers, not a "two jawed scissors holding
    > device." But it's not that, it's that most choose to call it a
    > "tensionometer", a word not found in Webster's. They seem to not use
    > the proper term to avoid being attacked by anonymous rude contributors
    > to this forum, as you must have seen.


    bullshitters are the rudest. you're both a bullshitter and a bloody fool.
     
  11. On Jan 19, 4:29 am, Ben C <spams...@spam.eggs> wrote:
    >
    >
    > Just because something is _possible_ doesn't mean it's necessarily what
    > happens or what is significant.
    >
    > I shouldn't need to tell you that.
    >
    > There are plenty of reasons why spokes can fail: poor quality, poor
    > surface finish and bad spoke line are top of my list as the _most
    > likely_. But I don't have the evidence either so I make no further claim
    > than that.


    Ben, for those with background in mechanical design, most of what
    Jobst says regarding stress relief in spokes is easily understood, and
    pretty obviously correct. It's well known that cold bending induces
    residual stresses. It's well known that residual stresses add
    (algebraically) to the overall stress level a part sees. It's well
    known that residual stresses can be difficult to detect, and are often
    overlooked. It's well known that neglecting their contribution can
    lead to fatigue (or other) failures.

    To illustrate the importance of these points: Strain gage companies
    sell special strain gages that are adhesively applied to a site on a
    workpiece, then balanced to zero, then re-read after a hole has been
    drilled in the workpiece. The new reading is used to compute the
    residual stresses. Obviously, this method is somewhat destructive and
    quite tedious. The fact that its used at all is evidence of the
    importance, and difficulty, of assessing residual stresses.

    Mechanical stress relief is used in other fields. It's not nearly as
    well known as thermal stress relief, and in fact I once had a
    conversation with a respected metallurgical engineer (_not_ jim beam)
    who had never heard of it. But from what I understand, the method
    works quite well.

    Of course, this doesn't mean that material, surface finish, etc. have
    no bearing. And I seriously doubt that Jobst has ever claimed that.
    But bringing microscopic high-tension-stress areas beyond yield, then
    relaxing them, leaving a fatigue-resistant compressive stress in their
    place, is certainly likely to help. And despite the fact that lots
    of people are familiar with the concepts, many of us didn't think in
    detail about their application to spokes and wheels until Jobst's
    explanations. I give him credit for that.

    > You have to stop making this personal.


    It's obvious to me that for at least a couple individuals, it is
    _very_ personal. While some of it may be triggered by Jobst's
    sometimes abrupt manner, their rudeness and abuse goes to extremes,
    and comes without any substantial contributions to our knowledge.

    > What you write is very
    > interesting and informative, but you can't expect people to just swallow
    > everything.


    I don't think one should "swallow" absolutely everything Jobst
    claims. But I think he's got a good record for stating things that
    make other mechanical engineers say "Hmm. I never thought of that
    point, but he's absolutely right." And conversely, I think some
    people are over-skeptical largely because they lack the background to
    evaluate his claims.

    - Frank Krygowski
     
  12. Tom Sherman

    Tom Sherman Guest

    frkrygow@gmail.com aka Frank Krygowski wrote:
    >
    > ... I once had a
    > conversation with a respected metallurgical engineer (_not_ jim beam)...
    >

    How can you be sure? ;)

    --
    Tom Sherman - Holstein-Friesland Bovinia
    "And never forget, life ultimately makes failures of all people."
    - A. Derleth
     
  13. Tom Sherman

    Tom Sherman Guest

    frkrygow@gmail.com aka Frank Krygowski wrote:
    >
    > ... I once had a
    > conversation with a respected metallurgical engineer (_not_ jim beam)...
    >

    How can you be sure? ;)

    --
    Tom Sherman - Holstein-Friesland Bovinia
    "And never forget, life ultimately makes failures of all people."
    - A. Derleth
     
  14. Matt O'Toole

    Matt O'Toole Guest

    On Sat, 19 Jan 2008 09:48:27 -0800, frkrygow wrote:

    > And conversely, I think some
    > people are over-skeptical largely because they lack the background to
    > evaluate his claims.


    Such is the way of the world!

    From a local, um, public official:

    "How do ah know you ain't shittin' me? You gotta degree in that or
    sumpthin'?"

    Matt O.
     
  15. Ben C

    Ben C Guest

    On 2008-01-19, frkrygow@gmail.com <frkrygow@gmail.com> wrote:
    > On Jan 19, 4:29 am, Ben C <spams...@spam.eggs> wrote:
    >>
    >>
    >> Just because something is _possible_ doesn't mean it's necessarily what
    >> happens or what is significant.
    >>
    >> I shouldn't need to tell you that.
    >>
    >> There are plenty of reasons why spokes can fail: poor quality, poor
    >> surface finish and bad spoke line are top of my list as the _most
    >> likely_. But I don't have the evidence either so I make no further claim
    >> than that.

    >
    > Ben, for those with background in mechanical design, most of what
    > Jobst says regarding stress relief in spokes is easily understood,
    > and pretty obviously correct.


    I understand the idea, and it is reasonable. And as you say later,
    credit to Jobst for thinking of it. But I don't believe we can say more
    than "it may be a factor in some failures."

    > It's well known that cold bending induces residual stresses. It's
    > well known that residual stresses add (algebraically) to the overall
    > stress level a part sees. It's well known that residual stresses can
    > be difficult to detect, and are often overlooked. It's well known
    > that neglecting their contribution can lead to fatigue (or other)
    > failures.
    >
    > To illustrate the importance of these points: Strain gage companies
    > sell special strain gages that are adhesively applied to a site on a
    > workpiece, then balanced to zero, then re-read after a hole has been
    > drilled in the workpiece. The new reading is used to compute the
    > residual stresses. Obviously, this method is somewhat destructive and
    > quite tedious. The fact that its used at all is evidence of the
    > importance, and difficulty, of assessing residual stresses.


    They are difficult to detect, but not impossible, and that doesn't
    change the fact that do you have to actually detect them before you can
    claim that they are a factor, rather than just a possible factor.

    The Loch Ness Monster is also difficult to detect. That's no excuse for
    presuming it's there.

    > Mechanical stress relief is used in other fields. It's not nearly as
    > well known as thermal stress relief, and in fact I once had a
    > conversation with a respected metallurgical engineer (_not_ jim beam)
    > who had never heard of it. But from what I understand, the method
    > works quite well.
    >
    > Of course, this doesn't mean that material, surface finish, etc. have
    > no bearing. And I seriously doubt that Jobst has ever claimed that.


    Well he gives a pretty good impression of someone who repeatedly insists
    that residual stress is the primary or only cause of broken spokes.

    > But bringing microscopic high-tension-stress areas beyond yield, then
    > relaxing them, leaving a fatigue-resistant compressive stress in their
    > place, is certainly likely to help. And despite the fact that lots
    > of people are familiar with the concepts, many of us didn't think in
    > detail about their application to spokes and wheels until Jobst's
    > explanations. I give him credit for that.


    So do I, but that doesn't make it true, just an interesting theory.

    [...]
    > I don't think one should "swallow" absolutely everything Jobst
    > claims. But I think he's got a good record for stating things that
    > make other mechanical engineers say "Hmm. I never thought of that
    > point, but he's absolutely right." And conversely, I think some
    > people are over-skeptical largely because they lack the background to
    > evaluate his claims.


    The reason for my skepticism is very simple and requires no specific
    background: where's the evidence?

    All I'm disagreeing with here is the position that residual stress is
    known to be the only or the primary cause of broken spokes.
     
  16. Ben C? writes:

    > All I'm disagreeing with here is the position that residual stress is
    > known to be the only or the primary cause of broken spokes.


    Those are your words, not mine. Willful misinterpretation often
    arises from a poor defensive position in a discussion.

    Jobst Brandt
     
  17. On Jan 19, 7:17 pm, Ben C <spams...@spam.eggs> wrote:
    > On 2008-01-19, frkry...@gmail.com <frkry...@gmail.com> wrote:
    >
    > > Ben, for those with background in mechanical design, most of what
    > > Jobst says regarding stress relief in spokes is easily understood,
    > > and pretty obviously correct.

    >
    > I understand the idea, and it is reasonable. And as you say later,
    > credit to Jobst for thinking of it. But I don't believe we can say more
    > than "it may be a factor in some failures."


    I think that statement is far too limited. And I think most people
    with extensive background in mechanical design principles would also
    think it's too limited.

    >
    > > It's well known that cold bending induces residual stresses. It's
    > > well known that residual stresses add (algebraically) to the overall
    > > stress level a part sees. It's well known that residual stresses can
    > > be difficult to detect, and are often overlooked. It's well known
    > > that neglecting their contribution can lead to fatigue (or other)
    > > failures.

    >
    > > To illustrate the importance of these points: Strain gage companies
    > > sell special strain gages that are adhesively applied to a site on a
    > > workpiece, then balanced to zero, then re-read after a hole has been
    > > drilled in the workpiece. The new reading is used to compute the
    > > residual stresses. Obviously, this method is somewhat destructive and
    > > quite tedious. The fact that its used at all is evidence of the
    > > importance, and difficulty, of assessing residual stresses.

    >
    > They are difficult to detect, but not impossible, and that doesn't
    > change the fact that do you have to actually detect them before you can
    > claim that they are a factor, rather than just a possible factor.


    Not at all. If:

    1) you had a situation known to normally produce residual stresses in
    parts that routinely failed by fatigue, and

    2) you applied techniques known to cause stress relief in those parts,
    and

    3) you observed a significant improvement in fatigue life,

    then it doesn't require the actual detection or measurement of those
    residual stresses to logically conclude they were an important factor,
    and are now lessened or eliminated.

    Yes, I understand there could be confounding factors. But IMO, what
    we see here are fairly desperate attempts to come up with _some_ way,
    _any_ way, to suggest that stress relief either doesn't exist, or
    doesn't work. In view of the logic behind it and the evidence in
    favor of it, neither the effort nor the motivation make much sense to
    me.

    > All I'm disagreeing with here is the position that residual stress is
    > known to be the only or the primary cause of broken spokes.


    Hmm. Be careful of setting up straw men. I think those of us that
    accept the benefits of stress relief believe merely that it
    significantly increases the fatigue life of spokes.

    The list of causes of spoke failure can be very long, and the "primary
    cause" can depend a lot on certain definitions. As an example,
    someone might claim the "primary cause" of breakage is that we don't
    use motorcycle spokes.

    - Frank Krygowski
     
  18. jim beam

    jim beam Guest

    jobst.brandt@stanfordalumni.org wrote:
    > Ben C? writes:
    >
    >> All I'm disagreeing with here is the position that residual stress is
    >> known to be the only or the primary cause of broken spokes.

    >
    > Those are your words, not mine. Willful misinterpretation often
    > arises from a poor defensive position in a discussion.


    so present /evidence/ for your position!!! you've never done that.
    /evidence/ is easily defended against "misinterpretation".
     
  19. jim beam

    jim beam Guest

    frkrygow@gmail.com wrote:
    > On Jan 19, 7:17 pm, Ben C <spams...@spam.eggs> wrote:
    >> On 2008-01-19, frkry...@gmail.com <frkry...@gmail.com> wrote:
    >>
    >>> Ben, for those with background in mechanical design, most of what
    >>> Jobst says regarding stress relief in spokes is easily understood,
    >>> and pretty obviously correct.

    >> I understand the idea, and it is reasonable. And as you say later,
    >> credit to Jobst for thinking of it. But I don't believe we can say more
    >> than "it may be a factor in some failures."

    >
    > I think that statement is far too limited. And I think most people
    > with extensive background in mechanical design principles would also
    > think it's too limited.


    and yet others that /claim/ to have extensive backgrounds in certain
    subjects are shown to be either bullshitters or grossly incompetent.
    odd how that gets in the way of "limitation".



    >
    >>> It's well known that cold bending induces residual stresses. It's
    >>> well known that residual stresses add (algebraically) to the overall
    >>> stress level a part sees. It's well known that residual stresses can
    >>> be difficult to detect, and are often overlooked. It's well known
    >>> that neglecting their contribution can lead to fatigue (or other)
    >>> failures.
    >>> To illustrate the importance of these points: Strain gage companies
    >>> sell special strain gages that are adhesively applied to a site on a
    >>> workpiece, then balanced to zero, then re-read after a hole has been
    >>> drilled in the workpiece. The new reading is used to compute the
    >>> residual stresses. Obviously, this method is somewhat destructive and
    >>> quite tedious. The fact that its used at all is evidence of the
    >>> importance, and difficulty, of assessing residual stresses.

    >> They are difficult to detect, but not impossible, and that doesn't
    >> change the fact that do you have to actually detect them before you can
    >> claim that they are a factor, rather than just a possible factor.

    >
    > Not at all. If:
    >
    > 1) you had a situation known to normally produce residual stresses in
    > parts that routinely failed by fatigue, and
    >
    > 2) you applied techniques known to cause stress relief in those parts,
    > and
    >
    > 3) you observed a significant improvement in fatigue life,


    bullshit. there has never been any evidence other than hearsay. and
    /that/ is conveniently ignoring changes in spoke metallurgy.


    >
    > then it doesn't require the actual detection or measurement of those
    > residual stresses to logically conclude they were an important factor,
    > and are now lessened or eliminated.
    >
    > Yes, I understand there could be confounding factors. But IMO, what
    > we see here are fairly desperate attempts to come up with _some_ way,
    > _any_ way, to suggest that stress relief either doesn't exist, or
    > doesn't work. In view of the logic behind it and the evidence in
    > favor of it, neither the effort nor the motivation make much sense to
    > me.


    then you're not bothering to pay attention to the "evidence" to which
    you're so desperately clinging. fatigue is not observed to initiate in
    the regions of the spoke that may have high residual stress. want to
    argue that it doesn't?


    >
    >> All I'm disagreeing with here is the position that residual stress is
    >> known to be the only or the primary cause of broken spokes.

    >
    > Hmm. Be careful of setting up straw men. I think those of us that
    > accept the benefits of stress relief believe merely that it
    > significantly increases the fatigue life of spokes.


    you're accepting presumption, not evidence - no evidence has ever been
    presented. and the evidence that /can/ be observed, contradicts the
    presumption. how inconvenient.


    >
    > The list of causes of spoke failure can be very long, and the "primary
    > cause" can depend a lot on certain definitions. As an example,
    > someone might claim the "primary cause" of breakage is that we don't
    > use motorcycle spokes.


    what an idiotic statement. oh, it's frank krygowski. that's to be
    expected then...
     
  20. Ben C

    Ben C Guest

    On 2008-01-20, jim beam <spamvortex@bad.example.net> wrote:
    > jobst.brandt@stanfordalumni.org wrote:
    >> Ben C? writes:
    >>
    >>> All I'm disagreeing with here is the position that residual stress is
    >>> known to be the only or the primary cause of broken spokes.

    >>
    >> Those are your words, not mine. Willful misinterpretation often
    >> arises from a poor defensive position in a discussion.

    >
    > so present /evidence/ for your position!!! you've never done that.
    > /evidence/ is easily defended against "misinterpretation".


    As far as I can tell, Jobst is now admitting there is no evidence and
    saying that neither does he claim that residual stress is known to be
    the only or the primary cause of broken spokes.

    He could have fooled me, and it would be better if he could come out and
    clarify his position with more definiteness rather than by an
    implication wrapped in an insult. But on the whole it's progress.
     
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