spoke fatigue troll

jim beam

http://www.flickr.com/photos/38636024@N00/1346747861/

your homework assignment is to annotate the above showing the location
of the neutral plane, and to indicate the residual stress profile across
the section.

Ben C

On 2008-04-26, jim beam <spamvortex@bad.example.net> wrote:
> http://www.flickr.com/photos/38636024@N00/1346747861/
>
> your homework assignment is to annotate the above showing the location
> of the neutral plane, and to indicate the residual stress profile across
> the section.

How's this: http://i29.tinypic.com/27y4bd4.jpg

Red: tensile residual stress
Blue: compressive residual stress
Green: neutral

Based on the link Peter posted

http://www.lanl.gov/contour/beam.html

Although I'm not sure if they're using negative (blue) to mean
compressive (I am) or which way they're bending their beam.

Ben C

On 2008-04-26, Ben C <spamspam@spam.eggs> wrote:
> On 2008-04-26, jim beam <spamvortex@bad.example.net> wrote:
>> http://www.flickr.com/photos/38636024@N00/1346747861/
>>
>> your homework assignment is to annotate the above showing the location
>> of the neutral plane, and to indicate the residual stress profile across
>> the section.
>
> How's this: http://i29.tinypic.com/27y4bd4.jpg
>
> Red: tensile residual stress
> Blue: compressive residual stress
> Green: neutral

Sorry, I'm an idiot. Attempt 2:

http://i26.tinypic.com/2jeqq7a.jpg

jim beam

Ben C wrote:
> On 2008-04-26, jim beam <spamvortex@bad.example.net> wrote:
>> http://www.flickr.com/photos/38636024@N00/1346747861/
>>
>> your homework assignment is to annotate the above showing the location
>> of the neutral plane, and to indicate the residual stress profile across
>> the section.
>
> How's this: http://i29.tinypic.com/27y4bd4.jpg

the revised one is better!


>
> Red: tensile residual stress
> Blue: compressive residual stress
> Green: neutral
>
> Based on the link Peter posted
>
> http://www.lanl.gov/contour/beam.html

that's not a profile appropriate here [but peter cole never plays it
straight] - it's a beam machined from thick section and the residual
stress profile is completely different from bent wire. here's a better one:
http://www.ncnr.nist.gov/AnnualRepo...99/residual.pdf

bear in mind, that is not severely bent like a spoke elbow, but it's a
much more relevant residual profile.

>
> Although I'm not sure if they're using negative (blue) to mean
> compressive (I am) or which way they're bending their beam.

for a written description, try this:
http://groups.google.com/group/rec....f080b93a59cca03

"cccTCttt", severely bent wire, is closer to appropriate.

naturally, if residual stress is an initiator, you expect fatigue to
start and grow from a point of high tensile residual. that's why, with
a coil spring, where there is a high tensile skin residual, and where
you have high skin torsion load that coincides, you do indeed observe
fatigue to initiate in the high tensile region. that's why thermal or
mechanical stress relief is so important in that application.

but with a spoke, the fatigue is observed to be independent of any high
residual zone [because there's minimal applied loading there], and
indeed independent of either tensile or compressive minor residuals.
therefore the largest concern is applied load, and thus its origination
is in the design, not the material processing.

Ben C

On 2008-04-26, jim beam <spamvortex@bad.example.net> wrote:
> Ben C wrote:
>> On 2008-04-26, jim beam <spamvortex@bad.example.net> wrote:
>>> http://www.flickr.com/photos/38636024@N00/1346747861/
>>>
>>> your homework assignment is to annotate the above showing the location
>>> of the neutral plane, and to indicate the residual stress profile across
>>> the section.
>>
>> How's this: http://i29.tinypic.com/27y4bd4.jpg
>
> the revised one is better!
>
>
>>
>> Red: tensile residual stress
>> Blue: compressive residual stress
>> Green: neutral
>>
>> Based on the link Peter posted
>>
>> http://www.lanl.gov/contour/beam.html
>
> that's not a profile appropriate here [but peter cole never plays it
> straight] - it's a beam machined from thick section and the residual
> stress profile is completely different from bent wire. here's a better one:
> http://www.ncnr.nist.gov/AnnualRepo...99/residual.pdf
>
> bear in mind, that is not severely bent like a spoke elbow, but it's a
> much more relevant residual profile.

It looks like I guessed right that blue is compressive and red is
tensile.

The profiles look similar but for the thicker beam, the regions of
highest residual stress are nearer the centre of the beam. They
alternate in the same sort of way, but it's as though the effect is sort
of rippling out and becoming weaker by the time you get to the edge.

Fatigue can start in the interior, but there are more things to get it
started on the exterior, like surface imperfections. So you would think
tensile residual stress at the exterior would be the biggest problem--
as the coil spring has.

[...]
> for a written description, try this:
> http://groups.google.com/group/rec....f080b93a59cca03
>
> "cccTCttt", severely bent wire, is closer to appropriate.

That looks more like the bar-- regions of highest T (bright red) and C
(dark blue) nearer the interior.

> naturally, if residual stress is an initiator, you expect fatigue to
> start and grow from a point of high tensile residual. that's why, with
> a coil spring, where there is a high tensile skin residual, and where
> you have high skin torsion load that coincides, you do indeed observe
> fatigue to initiate in the high tensile region.
>
> that's why thermal or mechanical stress relief is so important in that
> application.
>
> but with a spoke, the fatigue is observed to be independent of any high
> residual zone [because there's minimal applied loading there]

Are you saying spoke fatigue usually starts in the region of high
tensile loading-- i.e. the outside of the bend for outbound spokes? I
thought no-one really knew where it started because we haven't looked at
enough failed spokes.

For outbound spokes the small compressive residual on the outside of the
bend will mitigate fatigue (if only a little bit).

For inbound spokes it won't though-- they get a tensile loading on the
inside of the bend in use, where there is the small tensile residual.

Although not the highest region of tensile residual, it still might
accelerate fatigue that starts on the surface due to a surface
imperfection. I think that's Cole's point.

That all sounds reasonably logical provided one is careful not to make
unfounded claims about how significant that tensile skin residual on the
inside of inbound spokes is compared to other factors (which to be fair
Cole doesn't).

I doubt very much that it is very significant at all, but if it were,
how about this for a wheel-building technique:

Take 18 of your 36 spokes and bend their elbows inwards to about 75
degrees (you might have to go to 65 and let them spring back).

Then bend them back out to 90 degrees (you might have to go 95 or 100
and let them spring back).

They now should have compressive residual stress on the insides of the
elbows. Perfect! Use them for the inbound spokes. The other 18 should be
good to go out of the box for the outbound spokes.

Then whatever you do DON'T stress-relieve and ruin everything.

Since there is now compressive residual stress on all spokes protecting
you from fatigue, I predict that they will last even longer than usual--
at least 600000 miles.

jim beam

Ben C wrote:
> On 2008-04-26, jim beam <spamvortex@bad.example.net> wrote:
>> Ben C wrote:
>>> On 2008-04-26, jim beam <spamvortex@bad.example.net> wrote:
>>>> http://www.flickr.com/photos/38636024@N00/1346747861/
>>>>
>>>> your homework assignment is to annotate the above showing the location
>>>> of the neutral plane, and to indicate the residual stress profile across
>>>> the section.
>>> How's this: http://i29.tinypic.com/27y4bd4.jpg
>> the revised one is better!
>>
>>
>>> Red: tensile residual stress
>>> Blue: compressive residual stress
>>> Green: neutral
>>>
>>> Based on the link Peter posted
>>>
>>> http://www.lanl.gov/contour/beam.html
>> that's not a profile appropriate here [but peter cole never plays it
>> straight] - it's a beam machined from thick section and the residual
>> stress profile is completely different from bent wire. here's a better one:
>> http://www.ncnr.nist.gov/AnnualRepo...99/residual.pdf
>>
>> bear in mind, that is not severely bent like a spoke elbow, but it's a
>> much more relevant residual profile.
>
> It looks like I guessed right that blue is compressive and red is
> tensile.
>
> The profiles look similar but for the thicker beam, the regions of
> highest residual stress are nearer the centre of the beam. They
> alternate in the same sort of way, but it's as though the effect is sort
> of rippling out and becoming weaker by the time you get to the edge.

yup.


>
> Fatigue can start in the interior,

that's /ultra/ rare.



> but there are more things to get it
> started on the exterior, like surface imperfections.

almost /all/ failures start at the exterior.


> So you would think
> tensile residual stress at the exterior would be the biggest problem--
> as the coil spring has.

indeed. and on spokes too.


>
> [...]
>> for a written description, try this:
>> http://groups.google.com/group/rec....f080b93a59cca03
>>
>> "cccTCttt", severely bent wire, is closer to appropriate.
>
> That looks more like the bar-- regions of highest T (bright red) and C
> (dark blue) nearer the interior.

theoretical bar, not actual. the actual on that test was somewhat skewed.


>
>> naturally, if residual stress is an initiator, you expect fatigue to
>> start and grow from a point of high tensile residual. that's why, with
>> a coil spring, where there is a high tensile skin residual, and where
>> you have high skin torsion load that coincides, you do indeed observe
>> fatigue to initiate in the high tensile region.
>>
>> that's why thermal or mechanical stress relief is so important in that
>> application.
>>
>> but with a spoke, the fatigue is observed to be independent of any high
>> residual zone [because there's minimal applied loading there]
>
> Are you saying spoke fatigue usually starts in the region of high
> tensile loading-- i.e. the outside of the bend for outbound spokes?

either inside or outside, but definitely a region of high loading
[caused by bending].


> I
> thought no-one really knew where it started because we haven't looked at
> enough failed spokes.

who hasn't? just go to a bike shop and ask them to save some for you.



>
> For outbound spokes the small compressive residual on the outside of the
> bend will mitigate fatigue (if only a little bit).

theoretically, yes, but in practice they break pretty evenly both ways.

>
> For inbound spokes it won't though-- they get a tensile loading on the
> inside of the bend in use, where there is the small tensile residual.
>
> Although not the highest region of tensile residual, it still might
> accelerate fatigue that starts on the surface due to a surface
> imperfection. I think that's Cole's point.

peter cole is just fixated on the fact that because there may be a
residual stress, there will definitely be fatigue. which is not the
case here because it's not observed to be initiating in that high
residual zone.


>
> That all sounds reasonably logical provided one is careful not to make
> unfounded claims about how significant that tensile skin residual on the
> inside of inbound spokes is compared to other factors (which to be fair
> Cole doesn't).
>
> I doubt very much that it is very significant at all, but if it were,
> how about this for a wheel-building technique:
>
> Take 18 of your 36 spokes and bend their elbows inwards to about 75
> degrees (you might have to go to 65 and let them spring back).
>
> Then bend them back out to 90 degrees (you might have to go 95 or 100
> and let them spring back).
>
> They now should have compressive residual stress on the insides of the
> elbows. Perfect! Use them for the inbound spokes. The other 18 should be
> good to go out of the box for the outbound spokes.
>
> Then whatever you do DON'T stress-relieve and ruin everything.

but you can't. if you don't overload/stabilize/"stress relieve", the
wheel will go out of true in a few miles as the spokes bed in to the hub
holes. you can prove that to yourself next time you build.
particularly rears.


>
> Since there is now compressive residual stress on all spokes protecting
> you from fatigue, I predict that they will last even longer than usual--
> at least 600000 miles.

easier to just use a fatigue resistant material in the first place, or
better yet, use straight pull spokes.

Ben C

On 2008-04-26, jim beam <spamvortex@bad.example.net> wrote:
> Ben C wrote:
[...]
>> For inbound spokes it won't though-- they get a tensile loading on the
>> inside of the bend in use, where there is the small tensile residual.
>>
>> Although not the highest region of tensile residual, it still might
>> accelerate fatigue that starts on the surface due to a surface
>> imperfection. I think that's Cole's point.
>
> peter cole is just fixated on the fact that because there may be a
> residual stress, there will definitely be fatigue. which is not the
> case here because it's not observed to be initiating in that high
> residual zone.

Well I think you're right about that.

But I'm not sure Peter Cole has claimed the presence of residual stress
means there will definitely be fatigue (premature fatigue that is-- that
there will be fatigue in cyclically loaded aluminium is as certain as
death and taxes).

But Brandt _does_ appear to claim that residual stress causes spoke
failure and that stabilization works by stress-relieving. That's a step
too far for me.

jim beam

Ben C wrote:
> On 2008-04-26, jim beam <spamvortex@bad.example.net> wrote:
>> Ben C wrote:
> [...]
>>> For inbound spokes it won't though-- they get a tensile loading on the
>>> inside of the bend in use, where there is the small tensile residual.
>>>
>>> Although not the highest region of tensile residual, it still might
>>> accelerate fatigue that starts on the surface due to a surface
>>> imperfection. I think that's Cole's point.
>> peter cole is just fixated on the fact that because there may be a
>> residual stress, there will definitely be fatigue. which is not the
>> case here because it's not observed to be initiating in that high
>> residual zone.
>
> Well I think you're right about that.
>
> But I'm not sure Peter Cole has claimed the presence of residual stress
> means there will definitely be fatigue (premature fatigue that is-- that
> there will be fatigue in cyclically loaded aluminium is as certain as
> death and taxes).
>
> But Brandt _does_ appear to claim that residual stress causes spoke
> failure and that stabilization works by stress-relieving. That's a step
> too far for me.

the thing for me is that it's not like he couldn't go out and acquire
evidence if he really believed it to be true. hard data is where it's
at, not assertion based on fundamental misconception such as the belief
that he can eliminate fatigue from a material with no fatigue endurance
limit.

Peter Cole

Ben C wrote:
> On 2008-04-26, jim beam <spamvortex@bad.example.net> wrote:
>> Ben C wrote:
> [...]
>>> But Brandt _does_ appear to claim that residual stress causes spoke
>>> failure and that stabilization works by stress-relieving. That's a step
>>> too far for me.
>> the thing for me is that it's not like he couldn't go out and acquire
>> evidence if he really believed it to be true.
>
> Agreed. If it were anyone else they would say, "I know maybe residual
> stress is a factor", and people would say "yes, interesting, perhaps",
> discuss it a bit, and move on.
>
> But because it's Brandt's pet herring it refuses to die and people go
> around believing that "residual stress causes spoke failure".
>
> This is particularly ironic as Brandt is himself the proud slayer of the
> previous generation's myth and lore.

Before you catapult from your ad hominem to a broader indictment of the
engineering skills on this forum, you might (at least) familiarize
yourself with what Jobst actually wrote on the subject.

Residual stresses do exist, but they are only one part of the picture.
The debate (here) on this issue has evolved from a denial that residual
stresses existed, to an acceptance that they did, but played no part in
spoke fatigue, to now claiming they may play a minor role. All this is
rather beside the point.

The technique Jobst describes in his book is called "stress relief", not
"residual stress relief". Obviously, residual stress is added to
operational stress to predict fatigue. When a wheel is laced and
tensioned, some areas may be operating near yield. By momentarily
overloading, those areas will yield, and upon removal of the overload,
the (operating) stress will be lowered. That's all. There will be no
effect on any area other than one that's close to yield. That's all he says.

It is impossible to predict, given the various combinations of hubs and
spokes; forming and bending histories, exactly where the critical stress
areas are. There may not even be any. But we can not be sure of that. We
do know that if there are any tension stresses close to yield -- from
all the various sources: residual, spoke tension, bending moment, stress
raisers -- those critical stresses (and only those stresses) will be
lowered and the fatigue life will be improved. Jobst describes this as
"correcting the spoke line at the microscopic level". I don't think I
can improve upon that description.

And for the record, Jobst's book recommends correcting the spoke line
(carefully, and only when needed) after the wheel has been tensioned.
Also, peak residual stresses may exist on the surface after a bend (it
depends on the depth of the plastic/elastic transition) as described
here: http://www.doitpoms.ac.uk/tlplib/be...ing/plastic.php

Also, "direct pull" spokes have been around for a hundred years or so,
like almost all current "innovations", there are reasons for their
historical lack of popularity.

Finally, the "Mavic method" and cruder versions of stress relief have
been around for many years. Jobst never claimed to have invented wheel
stress relieving, only to have explained it and devised a better way to
do it. As for the claim that the benefit of these exercises is only to
provide "bedding in", I'd think it should be obvious (even after
building only a few wheels) that the final stresses in a wheel are
something of a crap shoot, not guaranteed to be improved or worsened by
bedding in.

All this straw man bashing could be avoided by simply reading the book.
Do you critique all books without reading them?

Michael Press

In article <UFnRj.2152$Zs1.2046@trndny07>,
Peter Cole <peter_cole@verizon.net> wrote:

> Finally, the "Mavic method" and cruder versions of stress relief have
> been around for many years. Jobst never claimed to have invented wheel
> stress relieving, only to have explained it and devised a better way to
> do it. As for the claim that the benefit of these exercises is only to
> provide "bedding in", I'd think it should be obvious (even after
> building only a few wheels) that the final stresses in a wheel are
> something of a crap shoot, not guaranteed to be improved or worsened by
> bedding in.

Jobst once spoke of being in a bicycle shop in Italy where
the guy building the wheel put the tensioned wheel on the
floor and stood on it. This was in the days before spokes
became much better.

--
Michael Press

Ben C

On 2008-04-28, Peter Cole <peter_cole@verizon.net> wrote:
> Ben C wrote:
>> On 2008-04-26, jim beam <spamvortex@bad.example.net> wrote:
>>> Ben C wrote:
>> [...]
>>>> But Brandt _does_ appear to claim that residual stress causes spoke
>>>> failure and that stabilization works by stress-relieving. That's a step
>>>> too far for me.
>>> the thing for me is that it's not like he couldn't go out and acquire
>>> evidence if he really believed it to be true.
>>
>> Agreed. If it were anyone else they would say, "I know maybe residual
>> stress is a factor", and people would say "yes, interesting, perhaps",
>> discuss it a bit, and move on.
>>
>> But because it's Brandt's pet herring it refuses to die and people go
>> around believing that "residual stress causes spoke failure".
>>
>> This is particularly ironic as Brandt is himself the proud slayer of the
>> previous generation's myth and lore.
>
> Before you catapult from your ad hominem to a broader indictment of the
> engineering skills on this forum, you might (at least) familiarize
> yourself with what Jobst actually wrote on the subject.
>
> Residual stresses do exist, but they are only one part of the picture.
> The debate (here) on this issue has evolved from a denial that residual
> stresses existed, to an acceptance that they did, but played no part in
> spoke fatigue, to now claiming they may play a minor role. All this is
> rather beside the point.
>
> The technique Jobst describes in his book is called "stress relief", not
> "residual stress relief". Obviously, residual stress is added to
> operational stress to predict fatigue. When a wheel is laced and
> tensioned, some areas may be operating near yield. By momentarily
> overloading, those areas will yield, and upon removal of the overload,
> the (operating) stress will be lowered. That's all. There will be no
> effect on any area other than one that's close to yield. That's all he says.
>
> It is impossible to predict, given the various combinations of hubs and
> spokes; forming and bending histories, exactly where the critical stress
> areas are. There may not even be any. But we can not be sure of that. We
> do know that if there are any tension stresses close to yield -- from
> all the various sources: residual, spoke tension, bending moment, stress
> raisers -- those critical stresses (and only those stresses) will be
> lowered and the fatigue life will be improved. Jobst describes this as
> "correcting the spoke line at the microscopic level". I don't think I
> can improve upon that description.
>
> And for the record, Jobst's book recommends correcting the spoke line
> (carefully, and only when needed) after the wheel has been tensioned.
> Also, peak residual stresses may exist on the surface after a bend (it
> depends on the depth of the plastic/elastic transition) as described
> here: http://www.doitpoms.ac.uk/tlplib/be...ing/plastic.php
>
> Also, "direct pull" spokes have been around for a hundred years or so,
> like almost all current "innovations", there are reasons for their
> historical lack of popularity.
>
> Finally, the "Mavic method" and cruder versions of stress relief have
> been around for many years. Jobst never claimed to have invented wheel
> stress relieving, only to have explained it and devised a better way to
> do it. As for the claim that the benefit of these exercises is only to
> provide "bedding in", I'd think it should be obvious (even after
> building only a few wheels) that the final stresses in a wheel are
> something of a crap shoot, not guaranteed to be improved or worsened by
> bedding in.
>
> All this straw man bashing could be avoided by simply reading the book.
> Do you critique all books without reading them?

As on many other occasions, you make a much more reasonable case than
Jobst.

I find little to disagree with in the above.

Recently I said I thought stabilization mostly worked by bending the
spokes but in some cases may also work by deforming the hub. daveornee's
recent pictures, which are very similar to those posted long ago by jim
beam, tip things a bit towards hub deformation in my mind. But I think
it still may be a bit of both and that it depends what hub and spokes
you're using.

I am not criticizing the book. I did not mention the book. I am talking
about Jobst's posts here, from which I have got the distinct impression
of a misleading emphasis on residual stress as a cause of spoke failure.

But as I have better things to do than go around digging up references
to prove this, to be fair I probably shouldn't have written what I did.

jobst.brandt@stanfordalumni.org

Michael Press wrote:

>> Finally, the "Mavic method" and cruder versions of stress relief
>> have been around for many years. Jobst never claimed to have
>> invented wheel stress relieving, only to have explained it and
>> devised a better way to do it. As for the claim that the benefit
>> of these exercises is only to provide "bedding in", I'd think it
>> should be obvious (even after building only a few wheels) that the
>> final stresses in a wheel are something of a crap shoot, not
>> guaranteed to be improved or worsened by bedding in.

> Jobst once spoke of being in a bicycle shop in Italy where the guy
> building the wheel put the tensioned wheel on the floor and stood on
> it. This was in the days before spokes became much better.

Mara was a small man who wore flexible rubber soled athletic shoes
with which he carefully walked around on the spokes of a new wheel
after tensioning, and turning the wheel over to do the same on the
other side. His comment was "makes the wheel last a long time" as my
Italian speaking friend translated. This was in Florence Italy and
Mara was Gastone Nencini's mechanic.

Jobst Brandt

Peter Cole

Ben C wrote:

> Recently I said I thought stabilization mostly worked by bending the
> spokes but in some cases may also work by deforming the hub. daveornee's
> recent pictures, which are very similar to those posted long ago by jim
> beam, tip things a bit towards hub deformation in my mind. But I think
> it still may be a bit of both and that it depends what hub and spokes
> you're using.

Holes typically deform as shown in the pictures. Just from eyeballing
those, it looks like about 0.5mm. Taken over an elbow length of 6mm,
that works out to a (rough) angle change of 5 deg. The depth of deform
should be less than linear with spoke tension, so the nominal 50% over
load of stress relief should represent less than a third of the depth.
Even that amount will reduce the spoke tension significantly (full spoke
tension = 0.75mm). Stress relief may reduce problems with tension loss
caused by spokes bedding in, but it's unlikely that has any impact on
spoke fatigue failure. There isn't even a plausible hypothesis for that.

Bottom line is that the deformation, both the majority that comes from
initial tension as well as whatever smaller contribution that may come
from over loading, doesn't predict the direction or degree of bending
stress in the tensioned spoke. The residual stresses may be beneficial
or harmful, the beauty of the over loading method of stress relief is
that you don't have to know all that, it will just improve things if
they're bad and not change things if they're not.

Obviously, if an outbound spoke has a noticeable bow away from the
flange after tensioning, it has a bending stress that will create
additional tension. Less obviously, a spoke that was pulled flat from
initial tension might have just as much bending tension. You can't just
look at a laced and tensioned wheel and diagnose stress levels by
inspection.

> I am not criticizing the book. I did not mention the book. I am talking
> about Jobst's posts here, from which I have got the distinct impression
> of a misleading emphasis on residual stress as a cause of spoke failure.

As I said before, these threads have gone through an evolution that
began with a denial of the presence of residual stress and have morphed
into a grudging admission with the dismissal for irrelevance. Residual
stresses are present, they may or may not be a factor in any given spoke
failure, but that's impossible to know without knowing all the operating
stresses. No postmortem is going to tell you whether the failure was
caused by a raiser, bending stress, residuals or any combination
thereof. All you do know is that stress relief will mitigate harmful
stresses from any/all of those causes.

These (endless) arguments follow the same pattern. Something is taken
out of context and a straw man is created. Like spoke tension and wheel
strength. The FEA leaves no doubt about what happens when a wheel is
overloaded, it doesn't matter that an unspoked rim will support body
weight without collapsing, the loads we're talking about are the several
g's that happen when the wheel hits a pothole, that's when strength
becomes important. Normally tensioned wheels loose spoke tension at
about the same magnitude of deflection as rim damage starts, looser
tension will mean impact damage will happen earlier. As the loaded area
of the rim becomes slack, the rim looses lateral stiffness while still
under compression and therefore is susceptible to buckling. Instead of
focusing on those important issues the threads degenerate into a
critique of spoke bed cracking, despite the fact that this is a problem
for only a few rims and the straw man is raised that Jobst advised
builders to exceed manufacturer's specs. When several sources are found
that confirm the anodization fatigue connection, all that is dismissed
with talk of anisotropy and extrusion flaws -- factors (obviously) still
there whether anodization is or is not.

For the last time, Jobst didn't say that spoke fatigue is caused
exclusively from residual stress, nor that spokes should be tightened
beyond published limits. He only said that stress relief reduces harmful
stresses and that, for a particular type of rim (with explicit caveats),
the maximum spoke tension as determined by buckling margin could be
found with the same process.

Michael Press

In article <slrng1c592.81v.spamspam@bowser.marioworld>,
Ben C <spamspam@spam.eggs> wrote:

> On 2008-04-28, Peter Cole <peter_cole@verizon.net> wrote:

[...]

> As on many other occasions, you make a much more reasonable case than
> Jobst.

Yeah, ain't he an unreasonable curmudgeon.

> I find little to disagree with in the above.

Oh, bless you.

> Recently I said I thought stabilization mostly worked by bending the
> spokes but in some cases may also work by deforming the hub. daveornee's
> recent pictures, which are very similar to those posted long ago by jim
> beam, tip things a bit towards hub deformation in my mind. But I think
> it still may be a bit of both and that it depends what hub and spokes
> you're using.
>
> I am not criticizing the book. I did not mention the book. I am talking
> about Jobst's posts here, from which I have got the distinct impression
> of a misleading emphasis on residual stress as a cause of spoke failure.

You criticize what you do not fully apprehend.
"distinct impression of a misleading emphasis
on residual stress as a cause of spoke failure"
is no basis for advancing categorical denials
of what is clearly laid out. Good people here
have spoon fed you all the details repeatedly,
and you spit up as would an unruly child. Get
a grip, exert yourself, and be man.

> of a misleading emphasis on residual stress as a cause of spoke failure"

> But as I have better things to do than go around digging up references
> to prove this, to be fair I probably shouldn't have written what I did.

These better things are to promote unsupported assertions
contrary to well supported findings? Do some work on your
own. You presume too much upon the good will advanced to you.

--
Michael Press