Re: I fixed a broken spoke!

jim beam said:

Gary Young said:

jim beam said:

Gary Young wrote:
> On Sun, 31 Dec 2006 16:55:22 -0800, jim beam wrote: <snip>
>
>> bending spokes can increase residual stress, increase surface
>> defects, increase dislocation density, and if performed prematurely,
>> lead to spoke alignment issues since the spoke is being forced to
>> conform with a hub not yet yielded to its final shape. maybe that's
>> why manufacturers specifically say not to do it.
> As you should know, since it's been pointed out to you before,
> Bontrager recommends correcting the spoke lines on its wheels:
>
> http://tinyurl.com/7fkbv (pdf) -- see page 7.
>
> Gerd Schrander, whose book (the German edition) is sold by DT and
> touted on its website, recommends correcting the spoke line:
>
> "Another small job simply involves bending the spokes at the nipple
> ends - the misalignment of spoke and nipple depends on the number of
> spokes and the spoking method used. Hold crossed pairs of spokes and
> squeeze them together. The spokes are made of flexible wire and so
> bending them in this way does no harm whatsoever."
>
> Page 85 of the English edition.
>
> Eric Hjertberg, one of the founders of Wheelsmith, recommends
> correcting the spoke line:
>
> "Now that each spoke is adjusted to the same length as its neighbors,
> it's time to bend the spokes near their elbow so they fully conform
> to their direction. Do it by inserting a stout screwdriver shaft
> between two spokes, just under one of the crosses. Once in this
> triangle, lever the screwdriver so the handle end rests against the
> outside spoke and the blade end presses against the inside spoke. A
> gentle push will bend them into conformity. Go around the wheel
> "setting in" pairs. This procedure stabilizes the wheel by doing
> immediately what normally occurs during miles of riding. The life of
> each spoke is enhanced because each elbow bends less after it
> conforms to its path. Otherwise, it constantly tries to recover its
> original shape during riding and fatigues more quickly."
>
> www.crazyrides.com/en/mastermechanic/part2.htm
>
> The only evidence I see that manufacturers frown on correcting the
> spoke line is a Sapim FAQ that's riddled with errors.
>
> Do you have some other evidence?
let me repeat:
"bending spokes can increase residual stress, increase surface
defects, increase dislocation density, and if performed prematurely,
lead to spoke alignment issues since the spoke is being forced to
conform with a hub not yet yielded to its final shape."

any questions?

Yeah, when are you going to stop dodging questions?

eh? it's not a dodge! i've repeatedly cited the primary factors in
spoke fatigue, and these are configuration, surface finish material, and
latterly, residual stress. the above explains part of the reasoning why
- bending can increase residual stress and increase surface damage,
higher dislocation density can help initiate fatigue, and premature
bending can affect configuration. if that's not being clear, ask for
clarification. but don't say it's dodging the question because it's
not.

I've made it clear that I'm interested in testing your claim that
manufacturers frown on correcting the spoke line. The paragraph above may
be on-point in some other branch of this thread, but it's not pertinent
to the issue I've raised.

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Do you have any other
evidence that manufacturers frown on correcting the spoke line? (Even
if that hadn't been my question, simply reiterating your assertions
doesn't count as evidence.)

sapim are most specific about it. sapim are also the only manufacturer
that have the minerals to publish fatigue data.

Do you agree with what Sapim says in that FAQ about other points? That one
should replace a hub after a few spokes have failed, for instance?

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regarding your citations, none bar wheelsmith are spoke manufacturers
- they simply assemble wheels from components they buy in.

DT isn't a spoke manufacturer? DT publishes, or at least distributes,
Schraner's book, touts it in its online materials (see, for instance,
the instructions to the DT tensiometer), and Schraner has taught at
DT-sponsored wheelbuilding seminars (at which participants can receive
a diploma as a "DT Certified Wheelbuilder" -- see page 101 of his
book).

but gary, with all due respect to schraner, he's not an engineer. he's
an artisan of the greatest sincerity, but that doesn't mean he knows
what's going on.

I think I've made this clear already, but let me repeat -- I'm not saying
that Schraner is either right or wrong. I'm simply pointing out that DT
endorses his views, to the point of publishing his book and using him as
an instructor. You can't have it both ways. If Schraner is wrong, then DT
is wrong too.

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As for Bontrager being a mere assembler of wheels, presumably it also
has to service its own wheels and thus would have some interest in
learning what leads to failure.

presumably, but they're still using elbowed spokes [last time i
checked]. use of straight pull would reduce fatigue by an order of
magnitude, but they haven't done it. why? the engineering reasons to
do so are compelling. one may therefore question their "interest" in
this subject.

I wasn't very clear in making my point here. If spoke manufacturers
acquire an expertise, it's presumably because they have an incentive to do
so - to build a reputation for quality, best their competition, sell more
spokes, and incur fewer warranty costs. I think the same sort of incentives
are at work at many companies that are primarily assemblers, particularly
when it's a large company like Bontrager/Trek that has engineers of its
own and that has the financial clout to have other manufacturers make
parts to its specifications.

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Besides, I don't think you can get away with limiting

things to spoke

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manufacturers. Your whole theory that spoke lines don't need to be
corrected depends on co-ordination between manufacturers of spokes,
rims, and hubs.

no it doesn't! i don't think you should bend spokes. i've cited the
reasons why. i think straight pull spokes have a serious fatigue
advantage over elbowed. i've cited the reasons why. the information is
out there. if manufacturers don't want to execute, that's their call.

You have a theory that spoke lines don't need to be corrected because
spokes, rims and hubs are optimized as it is. To achieve that optimization
(which you grossly exaggerate), there has to be co-ordination between the
various manufacturers. It won't do for you to say that spoke manufacturers
are on the ball, but makers of hubs, rims and wheels are not.

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In order to achieve the degree of perfection that you claim, they would
all have to understand the issues or at least be in communication with
each other. To say that only spoke makers know what they're doing tends
to cut against your argument.

see above. [some] spoke makers /do/ seem to know what they're doing.
but they'd be damned fools to suddenly stop selling elbowed spokes for
instance, even though it makes a lot more sense to do so.

DT makes not only spokes, but also hubs, rims, and wheels. Many of its
hubs and wheels use elbowed spokes. In other words, DT specifies elbowed
spokes even when it doesn't have to cater to some other hub maker. If, as
you say, elbowed spokes are bad from an engineering standpoint (something
I am not agreeing with), then DT is showing bad judgment that you can't
simply blame on someone else. So, does DT know what it's doing or not?

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it's also

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worth noting that bontrager have been savaged by jobst over the years,
schraner has been excoriated for saying that hubs hang from upper
spokes, and hjertberg is a buddy of jobst.

So what?

the "so what?" is that some people simply kow-tow rather than stand up
for themselves. tom ritchey used to contribute to this group, but got
so badly mauled, he left in disgust. a sad loss. but jobst would
rather have that than concede he'd ever made mistakes, let alone bother
to correct them. the peanut gallery joining in the spectacle and
throwing stones is simply perverse.

As I said before, so what? This neither supports nor counters your claims
about the credibility of manufacturers and their views on Jobst's ideas.
It is irrelevant.

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First you argue that manufacturers know what they're doing (or at
least, know better than Jobst).

some spoke manufacturers, yes.

Let's be clear. There's one spoke manufacturer that recommends against
correcting the spoke line -- Sapim (at least if one very sloppy FAQ really
represents the views of the company).

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Then I present examples in which they disagree with you.

i don't believe wheelsmith "cold forge" the butting on their spokes, no.
from what i can observe, i believe they grind and polish, just like
ashai, the people from whom they bought their manufacturing equipment,
do.

Yes, I'm familiar with your assertions. That's why I said you've presented
no CREDIBLE evidence.

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And now you're arguing that they don't know what they're doing or that
they're just aping what Jobst says? Do you see a problem here?

yes, i see a problem, but it's apparently different from the one you're
hinting at!

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I suspect that some of them are very wrong, just as I've argued that
Sapim's FAQ is filled with errors. But I'm not the one who argues that
manufacturers know what's best.

then discuss the errors! you can even email sapim if you want to. i
have in the past and they've been most pleasant.

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i don't know wheelsmith's

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position on this, but since they tend to be a little coy with details
such as how exactly their spokes are made,

The coyness is in your head. Wheelsmith says that the center sections
of its spokes are forged and you've presented no credible evidence
otherwise.

with respect gary, i have a little experience in observing manufacturing
technique.

Very easy for a sock puppet to say. Again, I'm not disputing that you've
tried to present evidence. However, your say-so is not credible evidence.

these spokes /look/ like they're ground and polished. i

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can't /prove/ that unless i have one under the metallurgical microscope,
but that observation is consistent with what is known of their
manufacturing mentors, ashai.

I've searched the web in vain for information on Asahi's methods. The only
evidence I've heard is your say-so. Once again, not credible.

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By the way, here's another indication that Wheelsmith doesn't frown on
correcting spoke lines:

"The Wheelsmith elbow radius is large so the spoke will require a
minimum of bending to conform to the hub."

www.wheelsmith.com/index_files/spoketech.htm

great.

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they may be choosing to swim
with the tide rather than fight against entrenched jobstian myopia.

Swimming against the tide? Entrenched Jobstian myopia? I thought you
said that all the other spoke makers disagree with Jobst?

no, i said they're probably choosing to swim with the tide and not
argue.

Let me be a little more obvious -- if all the other spoke makers disagree
with Jobst, then in what way can there said to be a tide or an
entrenchment in Jobst's favor?

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If so, in what way
would Wheelsmith be swimming against the tide by disagreeing with him?

how are they disagreeing? the above contradicts your statement.

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there are countless other cases of people mindlessly repeating
jobstian drivel. example: increasing spoke tension increases wheel
strength, rims crack because of anodizing, fatigue can be eliminated
by "stress relief", etc. but all i see that repetition proving is the
willingness of people to believe and take on faith rather than
question and seek fact.

Yada, yada, yada. Completely beside the point. Do manufacturers
repudiate Jobst's views or not?

that precisely /is/ the point. jobstian myths are rampant in the
english speaking industry simply because he's been such a shameless
bully and self-promotionist.

Ah, this is an interesting change in your position. Now it seems Jobst is
not spurned by the industry; instead, his ideas are "rampant" in some
parts of it. Not that that dodge does anything for your argument. After
all, DT is a Swiss company and endorses changing the spoke line. That
can't be explained by Jobst's standing in the English-speaking world.

I suppose it is a shame the way Jobst bullies the poor little bicycle
industry -- why, it's gotten so bad that you can't even buy a machined
rim, or a tire with a color tread, or a paired-spoke wheel, or a ....

but it doesn't mean he's right or that he

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knows what he's doing. the

above are examples often repeated, even

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though they're incorrect. some manufacturers /do/ contradict by action,
but why would they waste time arguing with him on a group like this?

Another dodge. The quotations I pointed to were not from this newsgroup.
They came from websites (and a book) that don't have to give Jobst equal
time or respond to his criticisms. This supposed ability of Jobst
to bully the industry is just another of your inventions to dodge the fact
that spoke manufacturers disagree with you about correcting the spoke
line. What makes the argument particularly unconvincing is how ad hoc it
is. As you've pointed out many times, there are many points on which spoke
companies disagree with Jobst, apparently being able to elude his iron
grip on those occasions.

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did /you/ notice any of jobst's errors in his book? if not, then
you're likely to repeat them too.

Given the fact that I'm not an engineer, I'm at somewhat of a
disadvantage when wading through the issues here on rbt. It's rare that
I have the in-depth knowledge to judge things for myself in real time
(though I do think I've acquired more depth over the years). By
necessity, I'm forced to rely on judgments of credibility.

based on what? if you can't tell fact from fiction, your basing your
judgment on non-factual criteria, in this case, the guy that tells you
he's right, regardless of whether he actually is. kinda scary actually.

Nothing scary about it. Scientists rely on credibility judgments all the
time. That's one reason so much importance is given to peer-reviewed
journals, for instance.

What happens when engineers or scientists encounter problems that fall
partly outside their area of expertise? Do you suppose they go back to
school to learn the new area? Why not rely on the experts in that field
and spend one's own time on the things that fall within one's own
expertise? (In other words, the division of labor contributes to
scientific advancement.)

How does one go about determining who's an expert if the subject matter is
opaque? By indicators of credibility -- institutional affiliations,
reputation, awards and recognition from peers, etc.

Science as a collective enterprise may need to prove every one of its
presuppositions and not simply rely on authority, but individual
scientists by necessity have to rely on credibility and authority as a
provisional matter.

In fact, you make credibility arguments all the time -- Jobst should
consult this textbook or that; manufacturers are more credible sources of
information than Jobst, etc. It's your misfortune that you so often
contradict yourself when you do so.

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In fact, since you've obviously had more engineering training than I, I
wouldn't ordinarily be sparring with you. What gives me the courage to
do so are your errors in simple logic, self-contradictions,
unwillingness to admit error, sock-puppetry, and refusal to state the
training or experience that gives you warrant to lecture us.

That's why I don't put much credibility in what you say.

you don't have to believe /anything/ i say. i'm not forcing you. but
i'm not selling you either and i have no vested interest in creating an
illusion of competence to support any meager living. if you want to
check facts, i'll give you references and you can go to the library and
check for yourself.

I've found non sequiturs in a very high percentage of your references
(e.g., charts and photos that don't prove what they purport to prove), so
I think I'll decline your invitation to a wild-goose chase.

alternatively, you can invest a little time and

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energy like carl fogel and do your own research.

As I've said, I'm a firm believer in the division of labor. While carrying
out experiments might be a good way to educate myself, I'm not convinced
that it would give me the means to referee disagreements among experts (or
would-be experts, in your case).

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Is this screwdriver technique like Sheldon's twisting on the outside
of the spoke crossing with a smooth pedal arm, only with the much
smaller lever of a screwdriver shaft on the inside of the crossing?

I have a tough time visualizing what Sheldon is doing there, but the
idea is probably the same, only he is doing it on the other side of the
crossing.

After putting my wheel together I was not satisfied with the way the
spokes were coming out of the hub on either side. Because I wasn't
using washers anymore, they weren't as snug to the hub. At first I
tried using a channel lock with a piece of old tire on the jaws,
pulling the spokes on either side of the hub towards each other. That
worked but it wasn't easy... and a little risky. Then I noticed that
wedging a screw driver in as close to the hub as possible would achieve
the same thing... and it was much easier as well.

I didn't know if what I was doing was helping or hurting... it was just
an experiment really... but it might make the stress worse. Instread of
curving out at the hub, the spokes wrap around an extra small amount so
that they look more like this ? on the end rather than a J. The spoke
runs more towards the center of the flange than the side. When I saw
the photo of Hjertberg doing the same thing to a wheel before it had
been fully tensioned, I was surprised... though I'm pretty sure he
didn't bend the spokes as far as I did.

Higher tension will act to straighten the spoke, opening up the ? a
bit. I would expect this to increase tensile stress on the inside
rather than the outside of the ?. Frankly, I haven't followed the
discussion on residual stresses well enough to know if this is good or
bad. Ideally, I think you wouldn't want any bends in the spoke.

A bad photo here: http://tinyurl.com/ygsu7z

jim beam said:

the "so what?" is that some people simply kow-tow rather than stand up
for themselves. tom ritchey used to contribute to this group, but got
so badly mauled, he left in disgust. a sad loss. but jobst would
rather have that than concede he'd ever made mistakes, let alone bother
to correct them. the peanut gallery joining in the spectacle and
throwing stones is simply perverse.

I isolated this passage because it seems to imply that
Tom Ritchey used to post here, and that Jobst is somehow
responsible for a bad atmosphere that caused TR to leave.
This seems distorted to the point of being irresponsible.
So far as I know, Tom Ritchey was never a regular poster
to r.b.tech, although I haven't been here forever. Perhaps you
could Google up some examples of his posts. Or were you
thinking of Keith Bontrager (and/or Gary Helfrich)? I rather
doubt Jobst drove KB off the group. It would be hard to drive
KB to do something he didn't want to do. I bet he doesn't have
time to post here though.

Here's a old quote (not a post) about Tom Ritchey and Jobst:
http://groups.google.com/group/rec.bicycles.tech/msg/fb3b8ed332022787
Here's Keith Bontrager on rim anodizing:
http://groups.google.com/group/rec.bicycles.tech/msg/ec15e59ebab85a31

Jobst's conversational style is not one I would choose
for myself. It's still more attractive than making [censored] up,
though.

Ben

quote='Ron Ruff said:

Is this screwdriver technique like Sheldon's twisting on the outside
of the spoke crossing with a smooth pedal arm, only with the much
smaller lever of a screwdriver shaft on the inside of the crossing?

I have a tough time visualizing what Sheldon is doing there, but the
idea is probably the same, only he is doing it on the other side of the
crossing.

After putting my wheel together I was not satisfied with the way the
spokes were coming out of the hub on either side. Because I wasn't
using washers anymore, they weren't as snug to the hub. At first I
tried using a channel lock with a piece of old tire on the jaws,
pulling the spokes on either side of the hub towards each other. That
worked but it wasn't easy... and a little risky. Then I noticed that
wedging a screw driver in as close to the hub as possible would achieve
the same thing... and it was much easier as well.

I didn't know if what I was doing was helping or hurting... it was just
an experiment really... but it might make the stress worse. Instread of
curving out at the hub, the spokes wrap around an extra small amount so
that they look more like this ? on the end rather than a J. The spoke
runs more towards the center of the flange than the side. When I saw
the photo of Hjertberg doing the same thing to a wheel before it had
been fully tensioned, I was surprised... though I'm pretty sure he
didn't bend the spokes as far as I did.

Higher tension will act to straighten the spoke, opening up the ? a
bit. I would expect this to increase tensile stress on the inside
rather than the outside of the ?. Frankly, I haven't followed the
discussion on residual stresses well enough to know if this is good or
bad. Ideally, I think you wouldn't want any bends in the spoke.

A bad photo here: http://tinyurl.com/ygsu7z[/QUOTE]
I think you are going in the correct direction:
From an older Barnett's Chapter 16 on wheel building
"As can be observed, spokes do not naturally take
a straight line from the hub flange to the rim. They
tend to arc on their way out of the flange, although
they will straighten up when tensioned. Once the tension
is gone, they will go back to being bowed. When
a wheel is in use, the spokes are constantly getting
tighter and looser. If they are also bowing and straightening
when riding, then they will fatigue much faster.
The following group of steps is designed to get the
spokes to follow a straight line from the hub to the
nipple, even when the spokes are relaxed, so that as
they loosen and tighten under use, they will not be
bowing and straightening as well."
"On right side of wheel, insert broad flat tool
(such as a cone wrench or large combination
wrench) between cross of spokes A1 and
C1 and the right hub flange, then apply leverage
in direction that forces A1 away
from central plane of wheel and C1 toward
central plane of wheel. Repeat for A2 and
C2 pair, A3 and C3 pair, etc."
"16.45 Just inside of the point where they cross each other, lever
each A–C pair with the same number so that the A spoke is moved
out and the C spoke is moved in to preset the spoke bends where the
spokes come out of the flange."
They go on to describe the same procedure for the other sided.
They suggest using the back side of a flat tool like a single-ended cone wrench. Their instructions call for doing it when the wheel is fully tensioned. As in the Bontrager instructions they expect a second round on tensioning.
I follow a similar set of steps before I move to the stabilizing steps.

Quoted message said:

Here's a old quote (not a post) about Tom Ritchey and Jobst:
http://groups.google.com/group/rec.bicycles.tech/msg/fb3b8ed332022787

Aha! I always wondered why Ritchey has such a unattractive logo. Some
things you better not leave to engineers ;-)

Lou

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Ben C? writes:

[snip]

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4. That adding tension to the spoke guarantees that the stress at
the outside of the elbow remains at yield, that being the
highest load it can withstand.

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I don't understand this.

OK, the outside of the elbow is at yield. Additional tension makes it
stretch while it remains at yield (by definition of yield) the stress
at which the steel stretches. Therefore tensioning a spoke cannot
alone reduce that stress but can only insure that it remain.

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I would have thought all of the spoke would be at less than yield
throughout the entire build process except for the moment at which
you plastically deform it at the elbow, after which it springs back
a bit, not remaining at yield while you carry on truing and
tensioning etc.

It does not spring back a bit after it is tensioned. As was just
established above, the elbow is yielding as it is bent to an acute
angle and remains there in the absence mechanical stress relief
(overloading it momentarily because it cannot be over-bent beyond
flush to the flange.) A stress relief overload can be applied after
the wheel is built because the rest of the spoke, except for small
regions that were plastically deformed are far below yield stress.

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5. Therefore, adding tension to a spoke cannot relieve that
condition unless an overload is applied and relaxed.

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I think I follow this, given 4, but 4 is the sticking point.

I hope I cleared that hurdle.

I still have some trouble believing that the elbow is at yield in either
a finished wheel or between correcting the spoke line and tensioning,
but I will think about it.

Doesn't this also imply that if the tension ever increases during use
(it has been suggested that this can happen when climbing out of the
saddle for example), the spokes would plastically deform at the elbow
with disastrous results?

[snip]

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My two top explanations are (a) flexing at the elbow because the spoke's
too loose and the load exceeds its pretension in normal use and (b)
surface imperfections in the elbow in poor quality spokes.

As I said, flexing is part of stress relief by improving the spoke
line.

I think we're talking about a different flexing. I'm referring to
flexing in use.

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Loose spokes do not accelerate spoke failure. If you believe so, you
should present a mechanism that would cause this.

If the pretension is less than the load then the bottom spokes are
pushed towards the rim by the hub, which bends them elastically at the
elbow. They are pulled back into pretension as the spokes pass through
the contact patch. This "flexion cycle" fatigues them quickly.

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It fails because there are high stress points at that place and
that spokes that don't break must have lower stress. The lower
stress is achieved by stress relief and that this is possible by
mechanical means has also been explained in great detail.

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I do believe it's possible. But so are alien abductions, and I don't
think they happen.

Why don't you believe that is possible?

I said I _do_ believe it's possible.

[snip]

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and what's wrong with the other explanations for spoke failure.

They lie remote possibilities as causes of failures in these spokes,
and I take DT as the prime example, they having one of the best wire
suppliers and have been working on reliability as long as any. Their
wire is not full of random flaws and other chemical anomalies cited as
spoke failure causes under the guise of metallurgical jargon. If that
were so, there would be systematic failure of their spokes and not
only at the elbow and threads.

You'd expect the flaws to be at the elbows and threads though, because
they'd be left by the operations of forming those features.

Ron Ruff said:

Quoted message said:

Is this screwdriver technique like Sheldon's twisting on the outside
of the spoke crossing with a smooth pedal arm, only with the much
smaller lever of a screwdriver shaft on the inside of the crossing?

I have a tough time visualizing what Sheldon is doing there, but the
idea is probably the same, only he is doing it on the other side of the
crossing.

[snip]

Dear Ron,

From the side of a wheel, stick a smooth pedal arm between a pair of
crossing spokes.

Slide the pedal arm down toward the hub, deep into the vee of the
spokes.

Turn the pedal arm to try to twist the two spokes around each other.

From where you're sitting, the pedal arm goes straight into the
screen, half-way, at the xx. If the left spoke is closer to you, then
you push the pedal arm to your left. You can only turn the pedal arm a
little ways, but you get impressive leverage without hurting your
hands, tension rises, and both spokes tend to pull their hub ends
toward the hub flange.

left
spoke
\ /
\ /
\xx/
\/
/\
/ \
hub

Cheers,

Carl Fogel

Ron Ruff said:

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It IS about forming the spoke at the elbow because even though it
might seem to be static, as mentioned above, it springs back from
residual stress. Overloading tension in the outer radius yields
that area and gives it a form that does not flex with each wheel
rotation.

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Makes me wonder what danger there would be in *over* bending the
elbow to conform to the hub. Seems like this would be preferable...

That would require selling inside and outside spokes for a specific
hub width and wheel dish. In mass production that might be possible
but for users or bicycle shops greatly impractical.

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The Eric Hjertberg method of bending the spokes around with a screw
driver *inside* the crossing would certainly achieve this.

I don't see the benefit. I need no extra tools and my method works as
expected and with good results.

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I just rebuilt a wheel, reusing 1.8/1.55mm spokes that previously
had DT washers under the heads. Some of the washers cracked in two
when I moved the spokes, so I decided to get rid of them... only now
the spokes are not shaped to fit the hub so well. I bent the spokes
inside the cross (2x 32 hole) using a screw driver, *after* the wheel
was fully tensioned, so that now the J resembles the the hook that
goes on the end of chains... ie the spoke wraps around the flange a
bit, and the center of the spoke line for both inside and outside
spokes heads to the center of the hub flange.

That is classically what is wrong with mixing inside and outside
spokes. The over-bent spokes could rock in their hub holes and often
do so causing failures.

Jobst Brandt

Ben C? said:

[snip] >>> 4. That adding tension to the spoke guarantees that the
stress at >>> the outside of the elbow remains at yield, that being
the >>> highest load it can withstand.

Quoted message said:

Quoted message said:

Quoted message said:

I don't understand this.

Quoted message said:

Quoted message said:

OK, the outside of the elbow is at yield. Additional tension makes
it stretch while it remains at yield (by definition of yield) the
stress at which the steel stretches. Therefore tensioning a spoke
cannot alone reduce that stress but can only insure that it remain.

Quoted message said:

Quoted message said:

Quoted message said:

I would have thought all of the spoke would be at less than yield
throughout the entire build process except for the moment at which
you plastically deform it at the elbow, after which it springs
back a bit, not remaining at yield while you carry on truing and
tensioning etc.

Quoted message said:

Quoted message said:

It does not spring back a bit after it is tensioned. As was just
established above, the elbow is yielding as it is bent to an acute
angle and remains there in the absence mechanical stress relief
(overloading it momentarily because it cannot be over-bent beyond
flush to the flange.) A stress relief overload can be applied
after the wheel is built because the rest of the spoke, except for
small regions that were plastically deformed are far below yield
stress.

Quoted message said:

Quoted message said:

Quoted message said:

> 5. Therefore, adding tension to a spoke cannot relieve that
> condition unless an overload is applied and relaxed.

Quoted message said:

Quoted message said:

Quoted message said:

I think I follow this, given 4, but 4 is the sticking point.

Quoted message said:

Quoted message said:

I hope I cleared that hurdle.

Quoted message said:

I still have some trouble believing that the elbow is at yield in
either a finished wheel or between correcting the spoke line and
tensioning, but I will think about it.

Do you believe that outbound spokes, while changing from an obtuse
angle elbow to an acute one must yield? After all, the have a new
shape that does not straighten when removed from a wheel.

That means that the elbow reached yield stress either while improving
the spoke line or during tensioning. Either way, tensioning force
insures that the stress achieved remains as high as it was (if no
stress relieving is done).

Quoted message said:

Doesn't this also imply that if the tension ever increases during
use (it has been suggested that this can happen when climbing out of
the saddle for example), the spokes would plastically deform at the
elbow with disastrous results?

Momentary overloads cause yielding that relaxes peak stress but riding
does not cause any significant tension increases. You can see that in
the deflection diagrams in "the Bicycle Wheel". Therefore no failure
will occur from one or more stress increases even if these exceed
yield. You can't go any higher than that so nothing changes except
possibly alignment. However, since these high stress zones are so
small, a few thousandths of an inch, no significant length change
occurs so trueness also shows practically no change.

Quoted message said:

[snip]

Quoted message said:

Quoted message said:

Quoted message said:

My two top explanations are (a) flexing at the elbow because the
spoke's too loose and the load exceeds its pretension in normal
use and (b) surface imperfections in the elbow in poor quality
spokes.

Quoted message said:

Quoted message said:

As I said, flexing is part of stress relief by improving the spoke
line.

Quoted message said:

I think we're talking about a different flexing. I'm referring to
flexing in use.

I am talking about flexing in use.

Quoted message said:

Quoted message said:

Loose spokes do not accelerate spoke failure. If you believe so,
you should present a mechanism that would cause this.

Quoted message said:

If the pretension is less than the load then the bottom spokes are
pushed toward the rim by the hub, which bends them elastically at
the elbow. They are pulled back into pretension as the spokes pass
through the contact patch. This "flexion cycle" fatigues them
quickly.

This does not buckle spokes, spokes that are free to lift their
nipples off the rim bed... which they are. Besides, a spoke so loose
that it rattles is not under discussion here. That is a wheel near
collapse.

Quoted message said:

Quoted message said:

Quoted message said:

> It fails because there are high stress points at that place and
> that spokes that don't break must have lower stress. The lower
> stress is achieved by stress relief and that this is possible by
> mechanical means has also been explained in great detail.

Quoted message said:

Quoted message said:

Quoted message said:

I do believe it's possible. But so are alien abductions, and I
don't think they happen.

Quoted message said:

Quoted message said:

Why don't you believe that is possible?

Quoted message said:

I said I _do_ believe it's possible.

As possible as alien abductions... I don't understand what you mean.

Quoted message said:

[snip]

Quoted message said:

Quoted message said:

Quoted message said:

and what's wrong with the other explanations for spoke failure.

Quoted message said:

Quoted message said:

They lie remote possibilities as causes of failures in these
spokes, and I take DT as the prime example, they having one of the
best wire suppliers and have been working on reliability as long as
any. Their wire is not full of random flaws and other chemical
anomalies cited as spoke failure causes under the guise of
metallurgical jargon. If that were so, there would be systematic
failure of their spokes and not only at the elbow and threads.

Quoted message said:

You'd expect the flaws to be at the elbows and threads though,
because they'd be left by the operations of forming those features.

The flaws cited are material anomalies and rough textures that would
be readily evident if present on the straight part of the spoke, or
for that matter on the outside of the elbow... but they are not.

Jobst Brandt

Carl Fogel asked:

Quoted message said:

Quoted message said:

Is this screwdriver technique like Sheldon's twisting on the outside
of the spoke crossing with a smooth pedal arm, only with the much
smaller lever of a screwdriver shaft on the inside of the crossing?

Ron Ruff said:

I have a tough time visualizing what Sheldon is doing there, but the
idea is probably the same, only he is doing it on the other side of the
crossing.

There's a photo and description at:

http://sheldonbrown.com/wheelbuild.html#seating

Sheldon "Old Crank" Brown

Gary Young wrote:
<snip for brevity>

Quoted message said:

I'm tired of chasing you in circles. I'll just note a couple of your more
obvious errors. This is one of them. DT and Wheelsmith are not silent on
the issue. See the quotations and references above.

gary, with respect, by that rationale, avocet are responsible for the
errors in "the book", not its author. that's clearly illogical nonsense.

<snip for brevity>

Quoted message said:

The only reason straight-pull spokes came into this discussion is because
you brought them up to question Bontrager's credibility.

no, i pointed out that straight pull spokes are available, that they
address the issue of elbow bending and thus elbow fatigue, and therefore
they are the choice of wheel manufacturers that are serious about wheel
endurance. that means /all/ manufacturers.

Quoted message said:

I take it by this
little dodge that you recognize that Bontrager may have practical reasons
to use elbowed-spokes and that that use doesn't reflect badly on its
credibility? Aside from that, your explanation doesn't address why DT uses
elbowed-spokes in some of its complete wheels.

yes i did. what part of:

"to suddenly /only/ sell straight pull spokes would therefore alienate
part of your sales market - it makes no business sense, even if it makes
engineering sense."

didn't you understand?

<snip for brevity>

Quoted message said:

What came up in that thread are your assertions and no other evidence. Are
you under the misapprehension that repeating the same thing over and over
again adds to the weight of the evidence?

no, but i'm sure reaching the conclusion that you don't read or don't
understand what i say.

<snip for brevity>

Quoted message said:

So your new line is that Jobst's bullying does not explain why DT and
Wheelsmith recommend correcting the spoke line? Around and around we go,
and where we stop....

see above.

<snip for brevity>

Quoted message said:

As I've said before, Schraner's ideas are used in DT's training courses
for wheelbuilders and are referenced in their technical literature -- as
in their instructions on using their tensiometer.

how old are you gary? have you ever heard of "marketing"? what's going
to sell more - the folksy old dude that has spent a lifetime doing what
the target market is doing, or the thrusty exec that's jamming
non-compete clauses down the throats of retailers? or maybe you think
the nerdy boffin is going to sell? i can hear the head of the sales
team shouting "sure, let's tell the market they don't know what they're
doing - that'll /really/ boost revenues." can you?

<snip for brevity>

Quoted message said:

Individuals scientists and technicians don't just rely on physical
evidence; they also rely on what other scientists and technicians SAY
about the physical evidence. An individual scientist doesn't replicate
every study on which he relies

he sure does if it doesn't agree with other research that precedes it!

Quoted message said:

(if he did, his career would be mired in a
crawl through the basics). It's true that scientists attach a great deal
of importance to replication, but by that they usually mean that a finding
has been replicated by at least two credible researchers, NOT that it is
incumbent on every individual scientist to replicate everything for
himself.

er, so when jobst brandt comes along with no research, no data but
hypotheses based on assumptions known to the world of matsci to be
false, are you saying that the previous 100 years of research should be
re-written just because of a stanford alumni email address? because
that sure is what it looks like!

<snip for brevity>

Quoted message said:

If I had the time to learn materials science in depth, I would try to get
admitted to a reputable school, not just any old fly-by-night institution.
Since you refuse to reveal your educational and employment history, you
are the equivalent of the fly-by-night school.

well gary, good luck to you. i hope you get there some day. btw, /i/
am not a school. not even a fly-by-night one.

Quoted message said:

Ben C? writes:

[snip]

Quoted message said:

Quoted message said:

I still have some trouble believing that the elbow is at yield in
either a finished wheel or between correcting the spoke line and
tensioning, but I will think about it.

Do you believe that outbound spokes, while changing from an obtuse
angle elbow to an acute one must yield?

Not 100% certain of "must", but that they often do I am sure of having
looked at spokes from a used wheel and seeing the difference in elbow
angle.

Quoted message said:

After all, the have a new shape that does not straighten when removed
from a wheel.

That means that the elbow reached yield stress either while improving
the spoke line or during tensioning. Either way, tensioning force
insures that the stress achieved remains as high as it was (if no
stress relieving is done).

It reached yield stress, I have troubling with it staying at yield
stress. You can correct the spoke line by pushing in with your thumb
while the spokes are still at much less than full tension (although not
everyone would recommend this). Since the spokes are not very tight,
it's hard to see how their tension is enough to keep the elbows at
yield.

It takes a considerable amount of tension to yield the elbow much just
by turning the nipple, that's why people bend the spoke with their
thumbs, old crank arms, etc., or with overtensioning (the Mavic method).

Quoted message said:

Quoted message said:

Doesn't this also imply that if the tension ever increases during
use (it has been suggested that this can happen when climbing out of
the saddle for example), the spokes would plastically deform at the
elbow with disastrous results?

Momentary overloads cause yielding that relaxes peak stress but riding
does not cause any significant tension increases. You can see that in
the deflection diagrams in "the Bicycle Wheel". Therefore no failure
will occur from one or more stress increases even if these exceed
yield. You can't go any higher than that so nothing changes except
possibly alignment. However, since these high stress zones are so
small, a few thousandths of an inch, no significant length change
occurs so trueness also shows practically no change.

Hmm, there is also the point that jim beam made that if the elbows were
at yield stress or close to it in use, fatigue failure would be very
rapid and frequent.

[snip]

Quoted message said:

Quoted message said:

If the pretension is less than the load then the bottom spokes are
pushed toward the rim by the hub, which bends them elastically at
the elbow. They are pulled back into pretension as the spokes pass
through the contact patch. This "flexion cycle" fatigues them
quickly.

This does not buckle spokes, spokes that are free to lift their
nipples off the rim bed... which they are.

Still, I imagine being lifted out of the rim bed and yanked back into it
again every time around can't good for fatigue life.

[snip]

Quoted message said:

Quoted message said:

Quoted message said:

>> It fails because there are high stress points at that place and
>> that spokes that don't break must have lower stress. The lower
>> stress is achieved by stress relief and that this is possible by
>> mechanical means has also been explained in great detail.

Quoted message said:

Quoted message said:

> I do believe it's possible. But so are alien abductions, and I
> don't think they happen.

Quoted message said:

Quoted message said:

Why don't you believe that is possible?

Quoted message said:

I said I _do_ believe it's possible.

As possible as alien abductions... I don't understand what you mean.

Alien abductions _are_ possible, it's just that the evidence for them is
very poor and that there are many more probable explanations for the
accounts people give.

Ben C? said:

[snip]

Quoted message said:

Quoted message said:

Quoted message said:

I still have some trouble believing that the elbow is at yield in
either a finished wheel or between correcting the spoke line and
tensioning, but I will think about it.

Quoted message said:

Quoted message said:

Do you believe that outbound spokes, while changing from an obtuse
angle elbow to an acute one must yield?

Quoted message said:

Not 100% certain of "must", but that they often do I am sure of
having looked at spokes from a used wheel and seeing the difference
in elbow angle.

I think there is where we have a problem. A spoke must yield to
change its elbow bend. That is part of the definition of yield. As
has been shown in pictures the spoke shows an acute angle at the elbow
on removal from a wheel.

Quoted message said:

Quoted message said:

After all, the have a new shape that does not straighten when
removed from a wheel.

Quoted message said:

Quoted message said:

That means that the elbow reached yield stress either while
improving the spoke line or during tensioning. Either way,
tensioning force insures that the stress achieved remains as high
as it was (if no stress relieving is done).

Quoted message said:

It reached yield stress, I have troubling with it staying at yield
stress. You can correct the spoke line by pushing in with your thumb
while the spokes are still at much less than full tension (although
not everyone would recommend this). Since the spokes are not very
tight, it's hard to see how their tension is enough to keep the
elbows at yield.

How do you propose it not stay at yield when it is taken to yield to
make the bend and no overload applied and released. Tensioning the
spoke only adds to the tensile load on the elbow so the yield location
just stretches a little as it remains at yield.

Quoted message said:

It takes a considerable tension to yield the elbow much just by
turning the nipple, that's why people bend the spoke with their
thumbs, old crank arms, etc., or with over tensioning (the Mavic
method).

Because this cannot over-bend (temporary overload) the elbow, it is at
yield when the spoke is tensioned further. Besides, it need not be
exactly at yield to accelerate fatigue failure. Close is good enough.

Quoted message said:

Quoted message said:

Quoted message said:

Doesn't this also imply that if the tension ever increases during
use (it has been suggested that this can happen when climbing out
of the saddle for example), the spokes would plastically deform at
the elbow with disastrous results?

Quoted message said:

Quoted message said:

Momentary overloads cause yielding that relaxes peak stress but
riding does not cause any significant tension increases. You can
see that in the deflection diagrams in "the Bicycle Wheel".
Therefore no failure will occur from one or more stress increases
even if these exceed yield. You can't go any higher than that so
nothing changes except possibly alignment. However, since these
high stress zones are so small, a few thousandths of an inch, no
significant length change occurs so trueness also shows practically
no change.

Quoted message said:

Hmm, there is also the point that jim beam made that if the elbows
were at yield stress or close to it in use, fatigue failure would be
very rapid and frequent.

They are! We have reports of failures in less than 100 miles of use,
but as I said, just being near the yield stress is good enough to
cause early fatigue failures, let's say in a thousand miles or so. As
I said, I have ridden the same DT spokes for around 300,000 miles with
failures of ones that got nicked by the chain falling into the spokes
or a stick in the wheel causing a kink.

Quoted message said:

[snip]

Quoted message said:

Quoted message said:

Quoted message said:

If the pretension is less than the load then the bottom spokes are
pushed toward the rim by the hub, which bends them elastically at
the elbow. They are pulled back into pretension as the spokes pass
through the contact patch. This "flexion cycle" fatigues them
quickly.

Quoted message said:

Quoted message said:

This does not buckle spokes, spokes that are free to lift their
nipples off the rim bed... which they are.

Quoted message said:

Still, I imagine being lifted out of the rim bed and yanked back
into it again every time around can't good for fatigue life.

Spokes are not human and don't consider stress changes in the
millisecond sudden changes causing distress. Consider valve springs
in an auto engine making stress cycles at about 3000/min for many
millions of cycles. They do not have localized high stress zones.

Quoted message said:

[snip]

Quoted message said:

Quoted message said:

Quoted message said:

>>> It fails because there are high stress points at that place and
>>> that spokes that don't break must have lower stress. The lower
>>> stress is achieved by stress relief and that this is possible
>>> by mechanical means has also been explained in great detail.

Quoted message said:

Quoted message said:

Quoted message said:

>> I do believe it's possible. But so are alien abductions, and I
>> don't think they happen.

Quoted message said:

Quoted message said:

Quoted message said:

> Why don't you believe that is possible?

Quoted message said:

Quoted message said:

Quoted message said:

I said I _do_ believe it's possible.

Quoted message said:

Quoted message said:

As possible as alien abductions... I don't understand what you

mean.

Quoted message said:

Alien abductions _are_ possible, it's just that the evidence for
them is very poor and that there are many more probable explanations
for the accounts people give.

OK, that fits the description of spurious failure causes adequately.

Jobst Brandt

jim beam said:

Gary Young wrote:
<snip for brevity>

Quoted message said:

I'm tired of chasing you in circles. I'll just note a couple of your
more obvious errors. This is one of them. DT and Wheelsmith are not
silent on the issue. See the quotations and references above.

gary, with respect, by that rationale, avocet are responsible for the
errors in "the book", not its author. that's clearly illogical
nonsense.

Avocet publishes and distributes the book. If there are errors in it, then
Avocet is clearly responsible for spreading and perpetuating those errors.
That seems like common sense to me.

Quoted message said:

<snip for brevity>

Quoted message said:

The only reason straight-pull spokes came into this discussion is
because you brought them up to question Bontrager's credibility.

no, i pointed out that straight pull spokes are available, that they
address the issue of elbow bending and thus elbow fatigue, and therefore
they are the choice of wheel manufacturers that are serious about wheel
endurance. that means /all/ manufacturers.

Reasonable readers can look above in this thread, where you brought up
this point -- whether it's a universal principle or not -- as an
indication that Bontrager's recommendations on correcting the spoke line
are not credible.

Quoted message said:

Quoted message said:

I take it by this
little dodge that you recognize that Bontrager may have practical
reasons to use elbowed-spokes and that that use doesn't reflect badly
on its credibility? Aside from that, your explanation doesn't address
why DT uses elbowed-spokes in some of its complete wheels.

yes i did. what part of:

"to suddenly /only/ sell straight pull spokes would therefore alienate
part of your sales market - it makes no business sense, even if it makes
engineering sense."

didn't you understand?

You said that DT sells elbowed spokes to cater to the home-build market,
where such spokes have some practical advantages. That does not explain
why DT uses such spokes in some of its pre-built wheels. Get it? Hand
built vs. pre-built?

If Bontrager's credibility is diminished because it uses elbowed spokes,
then the same is true of DT. If, on the other hand, DT has good reasons
for sometimes using elbowed spokes in its pre-built wheels, then Bontrager
presumably has good reasons for using them too, with no stain on its
reputation. So, which is it? Are elbowed spokes in pre-built wheels a sign
of lack of credibility or not?

Quoted message said:

<snip for brevity>

Quoted message said:

What came up in that thread are your assertions and no other evidence.
Are you under the misapprehension that repeating the same thing over
and over again adds to the weight of the evidence?

no, but i'm sure reaching the conclusion that you don't read or don't
understand what i say.

If you care to point out where in that thread there is "evidence" other
than your assertions, I'm all ears.

Quoted message said:

<snip for brevity>

Quoted message said:

So your new line is that Jobst's bullying does not explain why DT and
Wheelsmith recommend correcting the spoke line? Around and around we
go, and where we stop....

see above.

<snip for brevity>

Quoted message said:

As I've said before, Schraner's ideas are used in DT's training courses
for wheelbuilders and are referenced in their technical literature --
as in their instructions on using their tensiometer.

how old are you gary? have you ever heard of "marketing"? what's going
to sell more - the folksy old dude that has spent a lifetime doing what
the target market is doing, or the thrusty exec that's jamming
non-compete clauses down the throats of retailers? or maybe you think
the nerdy boffin is going to sell? i can hear the head of the sales
team shouting "sure, let's tell the market they don't know what they're
doing - that'll /really/ boost revenues." can you?

Hey, I think we've actually come to a point of agreement. I have indeed
heard of marketing. In fact, it's one of the reasons I'm not inclined to
put much stock in what manufacturers say on their websites and sometimes
even in their technical documentation.

But first I'd like to point to some additional evidence that DT's
relationship with Gerd Schraner is not merely one of publisher and author.

At several points in his book, Schraner acknowledges that the assistance
of DT in its preparation. Among others, Schraner thanks "Alan Schiff, the
latest member of the DT SWISS Instructors Team. We're all wheelaholics and
we all, as we say in Switzerland 'have our hay in the same loft,' meaning
tht we all use the same working and instruction methods." Page 101 of the
English edition.

Evidently, the relationship is not just a one-way street. On page 58, he
says that two spoke-length calculation products "have been included in the
DT PROLINE catalog at my suggestion."

Finally, UBI is a school that works together with DT to train "DT
Certified Wheel Builders." Here's what they say about DT -- and Schraner
-- on their website:

"DT Swiss, makers of DT spokes for almost 50 years and also the creators
of the Gerd Schraner Wheel Building course, has collaborated with UBI to
offer certification to a new generation of wheel builders."

www.bikeschool.com/dtrelease.htm

(I'm curious if there are any DT Certified people here who can say whether
or not spoke-line correction is taught in those classes.)

Now, I'm perfectly willing to acknowledge that there's probably an element
of marketing in all of this -- "Wheel builder to the stars endorses DT
products!" At the same time, Schraner is quite humble about his own
technical qualifications and acknowledges the help he's received from DT,
so I doubt DT would fail to correct him on the point of spoke-line
correction, particularly if it would lead -- as you claim -- to the
failure of its products in the field and the mis-training of DT Certified
Wheel Builders.

But let's not let that minor quibble come between us. I'm happy to agree
that marketing comes into play even in a technical training course. And
that, of course, means that what manufacturers say about their products is
not necessarily credible from a technical standpoint.

Quoted message said:

<snip for brevity>

Quoted message said:

Individuals scientists and technicians don't just rely on physical
evidence; they also rely on what other scientists and technicians SAY
about the physical evidence. An individual scientist doesn't replicate
every study on which he relies

he sure does if it doesn't agree with other research that precedes it!

Quoted message said:

(if he did, his career would be mired in a crawl through the basics).
It's true that scientists attach a great deal of importance to
replication, but by that they usually mean that a finding has been
replicated by at least two credible researchers, NOT that it is
incumbent on every individual scientist to replicate everything for
himself.

er, so when jobst brandt comes along with no research, no data but
hypotheses based on assumptions known to the world of matsci to be
false, are you saying that the previous 100 years of research should be
re-written just because of a stanford alumni email address? because
that sure is what it looks like!

Of course not.

Quoted message said:

<snip for brevity>

Quoted message said:

If I had the time to learn materials science in depth, I would try to
get admitted to a reputable school, not just any old fly-by-night
institution. Since you refuse to reveal your educational and employment
history, you are the equivalent of the fly-by-night school.

well gary, good luck to you. i hope you get there some day. btw, /i/
am not a school. not even a fly-by-night one.

Oops, I should have known better than to attempt to push an artsy-fartsy
thing like a Metaphor past a hard-headed materials-science guy.

Quoted message said:

Ben C? said:

[snip]

Quoted message said:

Quoted message said:

> I still have some trouble believing that the elbow is at yield in
> either a finished wheel or between correcting the spoke line and
> tensioning, but I will think about it.

Quoted message said:

Quoted message said:

Do you believe that outbound spokes, while changing from an obtuse
angle elbow to an acute one must yield?

Quoted message said:

Not 100% certain of "must", but that they often do I am sure of
having looked at spokes from a used wheel and seeing the difference
in elbow angle.

I think there is where we have a problem. A spoke must yield to
change its elbow bend. That is part of the definition of yield. As
has been shown in pictures the spoke shows an acute angle at the elbow
on removal from a wheel.

I agree, I posted some pictures like that recently myself, which came
from a wheel built with a Veloce hub which has canted flanges and holes
drilled normal to the flanges. There were clearly visible differences in
elbow angle comparing inbound and outbound spokes.

It is possible that this is not true of all wheels though, depending
possibly on the components and build method. jim beam for one seems
convinced it is not, and he posted a picture of a couple of spokes that
were bent about the same at the elbow.

Quoted message said:

Quoted message said:

Quoted message said:

After all, the have a new shape that does not straighten when
removed from a wheel.

Quoted message said:

Quoted message said:

That means that the elbow reached yield stress either while
improving the spoke line or during tensioning. Either way,
tensioning force insures that the stress achieved remains as high
as it was (if no stress relieving is done).

Quoted message said:

It reached yield stress, I have troubling with it staying at yield
stress. You can correct the spoke line by pushing in with your thumb
while the spokes are still at much less than full tension (although
not everyone would recommend this). Since the spokes are not very
tight, it's hard to see how their tension is enough to keep the
elbows at yield.

How do you propose it not stay at yield when it is taken to yield to
make the bend and no overload applied and released.

I think an overload probably is applied and released-- you push with
your thumb and bend the spoke, and, yes it does spring back a bit.

I can't back this up with anything other than that it's my perception,
but I'll have a closer look the next time I'm doing this.

[snip]

Quoted message said:

Quoted message said:

It takes a considerable tension to yield the elbow much just by
turning the nipple, that's why people bend the spoke with their
thumbs, old crank arms, etc., or with over tensioning (the Mavic
method).

Because this cannot over-bend (temporary overload) the elbow, it is at
yield when the spoke is tensioned further.

Just to clarify, the "Mavic method" (holding the rim and pressing the
end of the hub on a block of wood) I thought _was_ supposed to provide
temporary overload and stress relief (just like squeezing)?

The crank-arm method is also presented on Sheldon's page as a method of
stress relief and as an alternative to spoke squeezing.

Quoted message said:

Besides, it need not be exactly at yield to accelerate fatigue
failure. Close is good enough.

Agreed. But it is also one of the premises of your account of residual
stress, as I understand it, that it be held close to yield.

[snip]

Quoted message said:

Quoted message said:

Hmm, there is also the point that jim beam made that if the elbows
were at yield stress or close to it in use, fatigue failure would be
very rapid and frequent.

They are! We have reports of failures in less than 100 miles of use,
but as I said, just being near the yield stress is good enough to
cause early fatigue failures, let's say in a thousand miles or so.

You're saying that after I put the spokes in, correct their line, and
tension them up, they remain at yield stress in the elbow.

If I momentarily overload them (by squeezing etc.), this relieves
residual stresses. But won't they still be close to yield? The momentary
overload isn't supposed to deform them significantly, so they should be
under roughly the same amount of stress as they were before, just
without the residual stress. If not at yield, still close to it:
shouldn't this still mean very rapid fatigue failure?

In other words, if the spokes really are close to yield at the elbow,
with or without stress relief, they will surely fail quickly?

[snip]

Quoted message said:

Quoted message said:

Quoted message said:

>>>> It fails because there are high stress points at that place and
>>>> that spokes that don't break must have lower stress. The lower
>>>> stress is achieved by stress relief and that this is possible
>>>> by mechanical means has also been explained in great detail.

Quoted message said:

Quoted message said:

>>> I do believe it's possible. But so are alien abductions, and I
>>> don't think they happen.

Quoted message said:

Quoted message said:

>> Why don't you believe that is possible?

Quoted message said:

Quoted message said:

> I said I _do_ believe it's possible.

Quoted message said:

Quoted message said:

As possible as alien abductions... I don't understand what you

mean.

Quoted message said:

Alien abductions _are_ possible, it's just that the evidence for
them is very poor and that there are many more probable explanations
for the accounts people give.

OK, that fits the description of spurious failure causes adequately.

Good, so we agree on that then.

Ben C? said:

Quoted message said:

Quoted message said:

[snip]

Quoted message said:

Quoted message said:

Quoted message said:

>> I still have some trouble believing that the elbow is at yield
>> in either a finished wheel or between correcting the spoke line
>> and tensioning, but I will think about it.

Quoted message said:

Quoted message said:

Quoted message said:

> Do you believe that outbound spokes, while changing from an
> obtuse angle elbow to an acute one must yield?

Quoted message said:

Quoted message said:

Quoted message said:

Not 100% certain of "must", but that they often do I am sure of
having looked at spokes from a used wheel and seeing the
difference in elbow angle.

Quoted message said:

Quoted message said:

I think there is where we have a problem. A spoke must yield to
change its elbow bend. That is part of the definition of yield.
As has been shown in pictures the spoke shows an acute angle at the
elbow on removal from a wheel.

Quoted message said:

I agree, I posted some pictures like that recently myself, which
came from a wheel built with a Veloce hub which has canted flanges
and holes drilled normal to the flanges. There were clearly visible
differences in elbow angle comparing inbound and outbound spokes.

Quoted message said:

It is possible that this is not true of all wheels though, depending
possibly on the components and build method. jim beam for one seems
convinced it is not, and he posted a picture of a couple of spokes
that were bent about the same at the elbow.

That's a slim "possible" considering all the wheels I and others have
built, all of then showing a change in elbow bend. I have taken apart
enough wheels to be sure that outbound spokes no longer have obtuse
angle if it wasn't built on a thin steel flange (where spokes break
anyway for other reasons).

Quoted message said:

Quoted message said:

Quoted message said:

> After all, the have a new shape that does not straighten when
> removed from a wheel.

Quoted message said:

Quoted message said:

Quoted message said:

> That means that the elbow reached yield stress either while
> improving the spoke line or during tensioning. Either way,
> tensioning force insures that the stress achieved remains as high
> as it was (if no stress relieving is done).

Quoted message said:

Quoted message said:

Quoted message said:

It reached yield stress, I have troubling with it staying at yield
stress. You can correct the spoke line by pushing in with your
thumb while the spokes are still at much less than full tension
(although not everyone would recommend this). Since the spokes
are not very tight, it's hard to see how their tension is enough
to keep the elbows at yield.

Quoted message said:

Quoted message said:

How do you propose it not stay at yield when it is taken to yield
to make the bend and no overload applied and released.

Quoted message said:

I think an overload probably is applied and released-- you push with
your thumb and bend the spoke, and, yes it does spring back a bit.

You can only push it up against the flange, no farther, so
over-bending is not an option. This is about the elbow, not farther
up the spoke.

Quoted message said:

I can't back this up with anything other than that it's my
perception, but I'll have a closer look the next time I'm doing
this.

I think you can also derive this logically, the geometry being
straight forward.

Quoted message said:

[snip]

Quoted message said:

Quoted message said:

Quoted message said:

It takes a considerable tension to yield the elbow much just by
turning the nipple, that's why people bend the spoke with their
thumbs, old crank arms, etc., or with over tensioning (the Mavic
method).

Quoted message said:

Quoted message said:

Because this cannot over-bend (temporary overload) the elbow, it is
at yield when the spoke is tensioned further.

Quoted message said:

Just to clarify, the "Mavic method" (holding the rim and pressing
the end of the hub on a block of wood) I thought _was_ supposed to
provide temporary overload and stress relief (just like squeezing)?

Hold it!!! That IS stress relieving with a large overload with
subsequent relaxation.

Quoted message said:

The crank-arm method is also presented on Sheldon's page as a method
of stress relief and as an alternative to spoke squeezing.

I get the feeling something got lost here. The claim was that stress
relieving is not necessary. Now you introduce mechanical stress
relief to reduce residual stress. What happened?

Quoted message said:

Quoted message said:

Besides, it need not be exactly at yield to accelerate fatigue
failure. Close is good enough.

Quoted message said:

Agreed. But it is also one of the premises of your account of
residual stress, as I understand it, that it be held close to yield.

The higher the steady state stress, the greater the effect of cyclic
loading on fatigue. Therefore, the lower the stress in the elbow (the
most obvious and common point of such failures) the more durable the
wheel. No doubt there.

Quoted message said:

[snip]

Quoted message said:

Quoted message said:

Quoted message said:

Hmm, there is also the point that jim beam made that if the elbows
were at yield stress or close to it in use, fatigue failure would
be very rapid and frequent.

Quoted message said:

Quoted message said:

They are! We have reports of failures in less than 100 miles of
use, but as I said, just being near the yield stress is good enough
to cause early fatigue failures, let's say in a thousand miles or
so.

Quoted message said:

You're saying that after I put the spokes in, correct their line,
and tension them up, they remain at yield stress in the elbow.

Yes. As I explained, there is no way that the yield stress that
changes the shape of the elbow can relax unless it it overloaded
temporarily. Without stress relief overloading, stress remains nearly
as high as it was when introduced. If you look at the deflection
plots and data in "the Bicycle Wheel" you can see that the user cyclic
loadings barely cause increased loads on spokes, certainly not enough
to constitute stress relief.

Quoted message said:

If I momentarily overload them (by squeezing etc.), this relieves
residual stresses. But won't they still be close to yield? The
momentary overload isn't supposed to deform them significantly, so
they should be under roughly the same amount of stress as they were
before, just without the residual stress. If not at yield, still
close to it: shouldn't this still mean very rapid fatigue failure?

The overload is in addition to spoke tension and together these forces
cause yielding (loss of memory) for the high stress locations that are
only a few thousandths of an inch long. There is no significant
elongation but the high stress point being the primary tensile support
yields greatly, its neighbors not doing much of anything because the
outer skin of the elbow is carrying most of the tension. After
relaxation more of the cross section bears the load.

Quoted message said:

In other words, if the spokes really are close to yield at the
elbow, with or without stress relief, they will surely fail quickly?

Yes and we hear about those here off and on. As I mentioned, in the
days before DT and other new spokes, we used Stella, Robergel,
Redaelli, Berg and others whose fatigue resistance was poor and most
riders carried spare spokes if they rode any longer rides. The stress
relief methods I outlined were developed because improved durability
was so striking. The threshold between spokes that broke and ones
that didn't was so narrow that the benefits of stress relief was
obvious. With better spokes that can operate closer to yield stress
this is less apparent but still present.

Quoted message said:

[snip]

Quoted message said:

Quoted message said:

Quoted message said:

>>>>> It fails because there are high stress points at that place
>>>>> and that spokes that don't break must have lower stress. The
>>>>> lower stress is achieved by stress relief and that this is
>>>>> possible by mechanical means has also been explained in great
>>>>> detail.

Quoted message said:

Quoted message said:

Quoted message said:

>>>> I do believe it's possible. But so are alien abductions, and
>>>> I don't think they happen.

Quoted message said:

Quoted message said:

Quoted message said:

>>> Why don't you believe that is possible?

Quoted message said:

Quoted message said:

Quoted message said:

>> I said I _do_ believe it's possible.

Quoted message said:

Quoted message said:

Quoted message said:

> As possible as alien abductions... I don't understand what you

mean.

Quoted message said:

Quoted message said:

Quoted message said:

Alien abductions _are_ possible, it's just that the evidence for
them is very poor and that there are many more probable
explanations for the accounts people give.

Quoted message said:

Quoted message said:

OK, that fits the description of spurious failure causes
adequately.

Quoted message said:

Good, so we agree on that then.

Onward!

Jobst Brandt

Quoted message said:

Ben C? said:

Quoted message said:

> [snip]

Quoted message said:

Quoted message said:

>>> I still have some trouble believing that the elbow is at yield
>>> in either a finished wheel or between correcting the spoke line
>>> and tensioning, but I will think about it.

Quoted message said:

Quoted message said:

>> Do you believe that outbound spokes, while changing from an
>> obtuse angle elbow to an acute one must yield?

Quoted message said:

Quoted message said:

> Not 100% certain of "must", but that they often do I am sure of
> having looked at spokes from a used wheel and seeing the
> difference in elbow angle.

Quoted message said:

Quoted message said:

I think there is where we have a problem. A spoke must yield to
change its elbow bend. That is part of the definition of yield.
As has been shown in pictures the spoke shows an acute angle at the
elbow on removal from a wheel.

Quoted message said:

I agree, I posted some pictures like that recently myself, which
came from a wheel built with a Veloce hub which has canted flanges
and holes drilled normal to the flanges. There were clearly visible
differences in elbow angle comparing inbound and outbound spokes.

Quoted message said:

It is possible that this is not true of all wheels though, depending
possibly on the components and build method. jim beam for one seems
convinced it is not, and he posted a picture of a couple of spokes
that were bent about the same at the elbow.

That's a slim "possible" considering all the wheels I and others have
built, all of then showing a change in elbow bend. I have taken apart
enough wheels to be sure that outbound spokes no longer have obtuse
angle if it wasn't built on a thin steel flange (where spokes break
anyway for other reasons).

how many wheels have you disassembled that were built with care /not/ to
prematurely bend the spokes?

Quoted message said:

Quoted message said:

Quoted message said:

>> After all, the have a new shape that does not straighten when
>> removed from a wheel.

Quoted message said:

Quoted message said:

>> That means that the elbow reached yield stress either while
>> improving the spoke line or during tensioning. Either way,
>> tensioning force insures that the stress achieved remains as high
>> as it was (if no stress relieving is done).

Quoted message said:

Quoted message said:

> It reached yield stress, I have troubling with it staying at yield
> stress. You can correct the spoke line by pushing in with your
> thumb while the spokes are still at much less than full tension
> (although not everyone would recommend this). Since the spokes
> are not very tight, it's hard to see how their tension is enough
> to keep the elbows at yield.

Quoted message said:

Quoted message said:

How do you propose it not stay at yield when it is taken to yield
to make the bend and no overload applied and released.

Quoted message said:

I think an overload probably is applied and released-- you push with
your thumb and bend the spoke, and, yes it does spring back a bit.

You can only push it up against the flange, no farther, so
over-bending is not an option. This is about the elbow, not farther
up the spoke.

how does that address your assertion that the elbow remains at yield?

Quoted message said:

Quoted message said:

I can't back this up with anything other than that it's my
perception, but I'll have a closer look the next time I'm doing
this.

I think you can also derive this logically, the geometry being
straight forward.

see above.

Quoted message said:

Quoted message said:

[snip]

Quoted message said:

Quoted message said:

> It takes a considerable tension to yield the elbow much just by
> turning the nipple, that's why people bend the spoke with their
> thumbs, old crank arms, etc., or with over tensioning (the Mavic
> method).

Quoted message said:

Quoted message said:

Because this cannot over-bend (temporary overload) the elbow, it is
at yield when the spoke is tensioned further.

Quoted message said:

Just to clarify, the "Mavic method" (holding the rim and pressing
the end of the hub on a block of wood) I thought _was_ supposed to
provide temporary overload and stress relief (just like squeezing)?

Hold it!!! That IS stress relieving with a large overload with
subsequent relaxation.

it's bedding spokes into the hub and allowing any wind-up to release,
but is it metallurgical stress relief? according to fogel's
experiments, ordinary spoke tension achieves that. do you have any
evidence to support your assumption? have you tested spokes before and
after?

Quoted message said:

Quoted message said:

The crank-arm method is also presented on Sheldon's page as a method
of stress relief and as an alternative to spoke squeezing.

I get the feeling something got lost here. The claim was that stress
relieving is not necessary.

the process is necessary to build a wheel that stays true.

Quoted message said:

Now you introduce mechanical stress
relief to reduce residual stress. What happened?

er, by definition, mechanical relief as opposed to thermal relief,
/requires/ mechanical stress does it not?

Quoted message said:

Quoted message said:

Quoted message said:

Besides, it need not be exactly at yield to accelerate fatigue
failure. Close is good enough.

Quoted message said:

Agreed. But it is also one of the premises of your account of
residual stress, as I understand it, that it be held close to yield.

The higher the steady state stress, the greater the effect of cyclic
loading on fatigue. Therefore, the lower the stress in the elbow (the
most obvious and common point of such failures) the more durable the
wheel. No doubt there.

sorry, but there is doubt there - you need to clarify. from your
snippage, you state:

"4. That adding tension to the spoke guarantees that the stress at the
outside of the elbow remains at yield, that being the highest load
it can withstand."

the spoke is /not/ operating with the elbow at yield. if it were,
fatigue lives would be dramatically short.

Quoted message said:

Quoted message said:

[snip]

Quoted message said:

Quoted message said:

> Hmm, there is also the point that jim beam made that if the elbows
> were at yield stress or close to it in use, fatigue failure would
> be very rapid and frequent.

Quoted message said:

Quoted message said:

They are! We have reports of failures in less than 100 miles of
use, but as I said, just being near the yield stress is good enough
to cause early fatigue failures, let's say in a thousand miles or
so.

Quoted message said:

You're saying that after I put the spokes in, correct their line,
and tension them up, they remain at yield stress in the elbow.

Yes. As I explained, there is no way that the yield stress that
changes the shape of the elbow can relax unless it it overloaded
temporarily. Without stress relief overloading, stress remains nearly
as high as it was when introduced. If you look at the deflection
plots and data in "the Bicycle Wheel" you can see that the user cyclic
loadings barely cause increased loads on spokes, certainly not enough
to constitute stress relief.

but that's a wildly disconnected assumption. use loading is one thing.
the assumption that spoke elbows are at yield is quite another.

Quoted message said:

Quoted message said:

If I momentarily overload them (by squeezing etc.), this relieves
residual stresses. But won't they still be close to yield? The
momentary overload isn't supposed to deform them significantly, so
they should be under roughly the same amount of stress as they were
before, just without the residual stress. If not at yield, still
close to it: shouldn't this still mean very rapid fatigue failure?

The overload is in addition to spoke tension and together these forces
cause yielding (loss of memory) for the high stress locations that are
only a few thousandths of an inch long.

1. there is no "memory" in steel jobst. not ever. there is elasticity,
there is cold work, there is even phase transformation due to cold work,
but there is no "memory".
2. where does this assumption about "few thousandths of an inch" come
from??? have you done any microscopy? have you any evidence???? and
have you done any residual stress testing?

Quoted message said:

There is no significant
elongation but the high stress point being the primary tensile support
yields greatly, its neighbors not doing much of anything because the
outer skin of the elbow is carrying most of the tension. After
relaxation more of the cross section bears the load.

1. the whole structure bears the load.
2. different parts have differing strain.

under load, the outer skin of the elbow, because of the nature of
bending, means the outer skin bears the load. that's why fatigue
/always/ initiates at the extreme of the bend.

Quoted message said:

Quoted message said:

In other words, if the spokes really are close to yield at the
elbow, with or without stress relief, they will surely fail quickly?

Yes and we hear about those here off and on.

that's fudge. /all/ spokes would be affected if they were operated at
yield. instead, the failures that get reported most frequently here are
those for spokes made of inferior material. there /is/ a connection!

Quoted message said:

As I mentioned, in the
days before DT and other new spokes, we used Stella, Robergel,
Redaelli, Berg and others whose fatigue resistance was poor and most
riders carried spare spokes if they rode any longer rides.

yes, and they were made of inferior material, no vacuum degassing, and
worse, a lot were chrome plated, a guaranteed fatigue initiator.

Quoted message said:

The stress
relief methods I outlined were developed because improved durability
was so striking.

evidence. do not confuse subsequent improvement in material quality
with effects of "stress relief". you need proper "before and after"
statistics for that.

Quoted message said:

The threshold between spokes that broke and ones
that didn't was so narrow that the benefits of stress relief was
obvious.

data. stats. must publish, not make presumption masquerade for fact.

Quoted message said:

With better spokes that can operate closer to yield stress
this is less apparent but still present.

less apparent???

Quoted message said:

Quoted message said:

[snip]

Quoted message said:

Quoted message said:

>>>>>> It fails because there are high stress points at that place
>>>>>> and that spokes that don't break must have lower stress. The
>>>>>> lower stress is achieved by stress relief and that this is
>>>>>> possible by mechanical means has also been explained in great
>>>>>> detail.

Quoted message said:

Quoted message said:

>>>>> I do believe it's possible. But so are alien abductions, and
>>>>> I don't think they happen.

Quoted message said:

Quoted message said:

>>>> Why don't you believe that is possible?

Quoted message said:

Quoted message said:

>>> I said I _do_ believe it's possible.

Quoted message said:

Quoted message said:

>> As possible as alien abductions... I don't understand what you
mean.

Quoted message said:

Quoted message said:

> Alien abductions _are_ possible, it's just that the evidence for
> them is very poor and that there are many more probable
> explanations for the accounts people give.

Quoted message said:

Quoted message said:

OK, that fits the description of spurious failure causes
adequately.

Quoted message said:

Good, so we agree on that then.

Onward!

unfortunately, not much progress is evident.

i think the reason for your preoccupation with residual stress stems
from your belief that elasticity is evidence of it. that is incorrect.

reality is, elasticity is just that, elasticity. residual stress, being
entirely internal, cannot manifest itself outside the structure unless
there is a means by which it can express itself. this includes things
like heat, machining and corrosion. it can potentially also be
expressed with a depressed yield point on plastic deformation, but that
would have to be in conjunction with another agent since the unyielded
structure must be in equilibrium.

again, springback is /not/ evidence of residual stress. the primary
causes of spoke fatigue are bending which is affected by mechanical
configuration, surface finish/process quality and material quality.

Quoted message said:

You can only push it up against the flange, no farther, so
over-bending is not an option. This is about the elbow, not farther
up the spoke.

You can wrap the spoke around the flange a bit quite easily by wedging
a screw driver in between crosses near the flange. I'm not saying that
this is a good idea... but it seems like it would solve the problem of
having the outside of the J under high stress.

jim beam said:

Quoted message said:

Ben C? said:

>> [snip]

Quoted message said:

>>>> I still have some trouble believing that the elbow is at yield
>>>> in either a finished wheel or between correcting the spoke line
>>>> and tensioning, but I will think about it.

Quoted message said:

>>> Do you believe that outbound spokes, while changing from an
>>> obtuse angle elbow to an acute one must yield?

Quoted message said:

>> Not 100% certain of "must", but that they often do I am sure of
>> having looked at spokes from a used wheel and seeing the
>> difference in elbow angle.

Quoted message said:

> I think there is where we have a problem. A spoke must yield to
> change its elbow bend. That is part of the definition of yield.
> As has been shown in pictures the spoke shows an acute angle at the
> elbow on removal from a wheel.

Quoted message said:

I agree, I posted some pictures like that recently myself, which
came from a wheel built with a Veloce hub which has canted flanges
and holes drilled normal to the flanges. There were clearly visible
differences in elbow angle comparing inbound and outbound spokes.

Quoted message said:

It is possible that this is not true of all wheels though, depending
possibly on the components and build method. jim beam for one seems
convinced it is not, and he posted a picture of a couple of spokes
that were bent about the same at the elbow.

That's a slim "possible" considering all the wheels I and others have
built, all of then showing a change in elbow bend. I have taken apart
enough wheels to be sure that outbound spokes no longer have obtuse
angle if it wasn't built on a thin steel flange (where spokes break
anyway for other reasons).

how many wheels have you disassembled that were built with care /not/ to
prematurely bend the spokes?

Quoted message said:

Quoted message said:

>>> After all, the have a new shape that does not straighten when
>>> removed from a wheel.

Quoted message said:

>>> That means that the elbow reached yield stress either while
>>> improving the spoke line or during tensioning. Either way,
>>> tensioning force insures that the stress achieved remains as high
>>> as it was (if no stress relieving is done).

Quoted message said:

>> It reached yield stress, I have troubling with it staying at yield
>> stress. You can correct the spoke line by pushing in with your
>> thumb while the spokes are still at much less than full tension
>> (although not everyone would recommend this). Since the spokes
>> are not very tight, it's hard to see how their tension is enough
>> to keep the elbows at yield.

Quoted message said:

> How do you propose it not stay at yield when it is taken to yield
> to make the bend and no overload applied and released.

Quoted message said:

I think an overload probably is applied and released-- you push with
your thumb and bend the spoke, and, yes it does spring back a bit.

You can only push it up against the flange, no farther, so
over-bending is not an option. This is about the elbow, not farther
up the spoke.

how does that address your assertion that the elbow remains at yield?

Quoted message said:

Quoted message said:

I can't back this up with anything other than that it's my
perception, but I'll have a closer look the next time I'm doing
this.

I think you can also derive this logically, the geometry being
straight forward.

see above.

Quoted message said:

Quoted message said:

[snip]

Quoted message said:

>> It takes a considerable tension to yield the elbow much just by
>> turning the nipple, that's why people bend the spoke with their
>> thumbs, old crank arms, etc., or with over tensioning (the Mavic
>> method).

Quoted message said:

> Because this cannot over-bend (temporary overload) the elbow, it is
> at yield when the spoke is tensioned further.

Quoted message said:

Just to clarify, the "Mavic method" (holding the rim and pressing
the end of the hub on a block of wood) I thought _was_ supposed to
provide temporary overload and stress relief (just like squeezing)?

Hold it!!! That IS stress relieving with a large overload with
subsequent relaxation.

it's bedding spokes into the hub and allowing any wind-up to release,
but is it metallurgical stress relief? according to fogel's
experiments, ordinary spoke tension achieves that. do you have any
evidence to support your assumption? have you tested spokes before and
after?

Quoted message said:

Quoted message said:

The crank-arm method is also presented on Sheldon's page as a method
of stress relief and as an alternative to spoke squeezing.

I get the feeling something got lost here. The claim was that stress
relieving is not necessary.

the process is necessary to build a wheel that stays true.

Quoted message said:

Now you introduce mechanical stress
relief to reduce residual stress. What happened?

er, by definition, mechanical relief as opposed to thermal relief,
/requires/ mechanical stress does it not?

Quoted message said:

Quoted message said:

> Besides, it need not be exactly at yield to accelerate fatigue
> failure. Close is good enough.

Quoted message said:

Agreed. But it is also one of the premises of your account of
residual stress, as I understand it, that it be held close to yield.

The higher the steady state stress, the greater the effect of cyclic
loading on fatigue. Therefore, the lower the stress in the elbow (the
most obvious and common point of such failures) the more durable the
wheel. No doubt there.

sorry, but there is doubt there - you need to clarify. from your
snippage, you state:

"4. That adding tension to the spoke guarantees that the stress at the
outside of the elbow remains at yield, that being the highest load
it can withstand."

the spoke is /not/ operating with the elbow at yield. if it were,
fatigue lives would be dramatically short.

Quoted message said:

Quoted message said:

[snip]

Quoted message said:

>> Hmm, there is also the point that jim beam made that if the elbows
>> were at yield stress or close to it in use, fatigue failure would
>> be very rapid and frequent.

Quoted message said:

> They are! We have reports of failures in less than 100 miles of
> use, but as I said, just being near the yield stress is good enough
> to cause early fatigue failures, let's say in a thousand miles or
> so.

Quoted message said:

You're saying that after I put the spokes in, correct their line,
and tension them up, they remain at yield stress in the elbow.

Yes. As I explained, there is no way that the yield stress that
changes the shape of the elbow can relax unless it it overloaded
temporarily. Without stress relief overloading, stress remains nearly
as high as it was when introduced. If you look at the deflection
plots and data in "the Bicycle Wheel" you can see that the user cyclic
loadings barely cause increased loads on spokes, certainly not enough
to constitute stress relief.

but that's a wildly disconnected assumption. use loading is one thing.
the assumption that spoke elbows are at yield is quite another.

Quoted message said:

Quoted message said:

If I momentarily overload them (by squeezing etc.), this relieves
residual stresses. But won't they still be close to yield? The
momentary overload isn't supposed to deform them significantly, so
they should be under roughly the same amount of stress as they were
before, just without the residual stress. If not at yield, still
close to it: shouldn't this still mean very rapid fatigue failure?

The overload is in addition to spoke tension and together these forces
cause yielding (loss of memory) for the high stress locations that are
only a few thousandths of an inch long.

1. there is no "memory" in steel jobst. not ever. there is elasticity,
there is cold work, there is even phase transformation due to cold work,
but there is no "memory".
2. where does this assumption about "few thousandths of an inch" come
from??? have you done any microscopy? have you any evidence???? and
have you done any residual stress testing?

Quoted message said:

There is no significant
elongation but the high stress point being the primary tensile support
yields greatly, its neighbors not doing much of anything because the
outer skin of the elbow is carrying most of the tension. After
relaxation more of the cross section bears the load.

1. the whole structure bears the load.
2. different parts have differing strain.

under load, the outer skin of the elbow, because of the nature of
bending, means the outer skin bears the load.

rephrase! the outer skin has the most strain.

Quoted message said:

that's why fatigue
/always/ initiates at the extreme of the bend.

Quoted message said:

Quoted message said:

In other words, if the spokes really are close to yield at the
elbow, with or without stress relief, they will surely fail quickly?

Yes and we hear about those here off and on.

that's fudge. /all/ spokes would be affected if they were operated at
yield. instead, the failures that get reported most frequently here are
those for spokes made of inferior material. there /is/ a connection!

Quoted message said:

As I mentioned, in the
days before DT and other new spokes, we used Stella, Robergel,
Redaelli, Berg and others whose fatigue resistance was poor and most
riders carried spare spokes if they rode any longer rides.

yes, and they were made of inferior material, no vacuum degassing, and
worse, a lot were chrome plated, a guaranteed fatigue initiator.

Quoted message said:

The stress
relief methods I outlined were developed because improved durability
was so striking.

evidence. do not confuse subsequent improvement in material quality
with effects of "stress relief". you need proper "before and after"
statistics for that.

Quoted message said:

The threshold between spokes that broke and ones
that didn't was so narrow that the benefits of stress relief was
obvious.

data. stats. must publish, not make presumption masquerade for fact.

Quoted message said:

With better spokes that can operate closer to yield stress
this is less apparent but still present.

less apparent???

Quoted message said:

Quoted message said:

[snip]

Quoted message said:

>>>>>>> It fails because there are high stress points at that place
>>>>>>> and that spokes that don't break must have lower stress. The
>>>>>>> lower stress is achieved by stress relief and that this is
>>>>>>> possible by mechanical means has also been explained in great
>>>>>>> detail.

Quoted message said:

>>>>>> I do believe it's possible. But so are alien abductions, and
>>>>>> I don't think they happen.

Quoted message said:

>>>>> Why don't you believe that is possible?

Quoted message said:

>>>> I said I _do_ believe it's possible.

Quoted message said:

>>> As possible as alien abductions... I don't understand what you
> mean.

Quoted message said:

>> Alien abductions _are_ possible, it's just that the evidence for
>> them is very poor and that there are many more probable
>> explanations for the accounts people give.

Quoted message said:

> OK, that fits the description of spurious failure causes
> adequately.

Quoted message said:

Good, so we agree on that then.

Onward!

unfortunately, not much progress is evident.

i think the reason for your preoccupation with residual stress stems
from your belief that elasticity is evidence of it. that is incorrect.

reality is, elasticity is just that, elasticity. residual stress, being
entirely internal, cannot manifest itself outside the structure unless
there is a means by which it can express itself. this includes things
like heat, machining and corrosion. it can potentially also be
expressed with a depressed yield point on plastic deformation, but that
would have to be in conjunction with another agent since the unyielded
structure must be in equilibrium.

again, springback is /not/ evidence of residual stress. the primary
causes of spoke fatigue are bending which is affected by mechanical
configuration, surface finish/process quality and material quality.

jim beam said:

Quoted message said:

Quoted message said:

>> [snip]

Quoted message said:

Quoted message said:

Quoted message said:

>>>> I still have some trouble believing that the elbow is at yield
>>>> in either a finished wheel or between correcting the spoke
>>>> line and tensioning, but I will think about it.

Quoted message said:

Quoted message said:

Quoted message said:

>>> Do you believe that outbound spokes, while changing from an
>>> obtuse angle elbow to an acute one must yield?

Quoted message said:

Quoted message said:

Quoted message said:

>> Not 100% certain of "must", but that they often do I am sure of
>> having looked at spokes from a used wheel and seeing the
>> difference in elbow angle.

Quoted message said:

Quoted message said:

Quoted message said:

> I think there is where we have a problem. A spoke must yield to
> change its elbow bend. That is part of the definition of yield.
> As has been shown in pictures the spoke shows an acute angle at
> the elbow on removal from a wheel.

Quoted message said:

Quoted message said:

Quoted message said:

I agree, I posted some pictures like that recently myself, which
came from a wheel built with a Veloce hub which has canted flanges
and holes drilled normal to the flanges. There were clearly
visible differences in elbow angle comparing inbound and outbound
spokes.

Quoted message said:

Quoted message said:

Quoted message said:

It is possible that this is not true of all wheels though,
depending possibly on the components and build method. jim beam
for one seems convinced it is not, and he posted a picture of a
couple of spokes that were bent about the same at the elbow.

Quoted message said:

Quoted message said:

That's a slim "possible" considering all the wheels I and others
have built, all of then showing a change in elbow bend. I have
taken apart enough wheels to be sure that outbound spokes no longer
have obtuse angle if it wasn't built on a thin steel flange (where
spokes break anyway for other reasons).

Quoted message said:

how many wheels have you disassembled that were built with care
/not/ to prematurely bend the spokes?

As I said, enough to know that none had inbound and outbound spokes
with the same shape elbow. In addition, other wheel builders have
reported the same but you doubt everything said here in spite of
photographs.

Quoted message said:

Quoted message said:

Quoted message said:

>>> After all, the have a new shape that does not straighten when
>>> removed from a wheel.

Quoted message said:

Quoted message said:

Quoted message said:

>>> That means that the elbow reached yield stress either while
>>> improving the spoke line or during tensioning. Either way,
>>> tensioning force insures that the stress achieved remains as
>>> high as it was (if no stress relieving is done).

Quoted message said:

Quoted message said:

Quoted message said:

>> It reached yield stress, I have troubling with it staying at
>> yield stress. You can correct the spoke line by pushing in with
>> your thumb while the spokes are still at much less than full
>> tension (although not everyone would recommend this). Since the
>> spokes are not very tight, it's hard to see how their tension is
>> enough to keep the elbows at yield.

Quoted message said:

Quoted message said:

Quoted message said:

> How do you propose it not stay at yield when it is taken to yield
> to make the bend and no overload applied and released.

Quoted message said:

Quoted message said:

Quoted message said:

I think an overload probably is applied and released-- you push
with your thumb and bend the spoke, and, yes it does spring back a
bit.

Quoted message said:

Quoted message said:

You can only push it up against the flange, no farther, so
over-bending is not an option. This is about the elbow, not
farther up the spoke.

Quoted message said:

how does that address your assertion that the elbow remains at
yield?

If it was at yield when bent to its position in the wheel and is
subsequently tensioned it can only return to that state, there having
been no significant over-shoot in the bend. So when it is again flush
with the flange, it is back where it was when bent.

Quoted message said:

Quoted message said:

Quoted message said:

I can't back this up with anything other than that it's my
perception, but I'll have a closer look the next time I'm doing
this.

Quoted message said:

Quoted message said:

I think you can also derive this logically, the geometry being
straight forward.

Quoted message said:

see above.

Thanks.

Quoted message said:

Quoted message said:

Quoted message said:

[snip]

Quoted message said:

Quoted message said:

Quoted message said:

>> It takes a considerable tension to yield the elbow much just by
>> turning the nipple, that's why people bend the spoke with their
>> thumbs, old crank arms, etc., or with over tensioning (the Mavic
>> method).

Quoted message said:

Quoted message said:

Quoted message said:

> Because this cannot over-bend (temporary overload) the elbow, it
> is at yield when the spoke is tensioned further.

Quoted message said:

Quoted message said:

Quoted message said:

Just to clarify, the "Mavic method" (holding the rim and pressing
the end of the hub on a block of wood) I thought _was_ supposed to
provide temporary overload and stress relief (just like
squeezing)?

Quoted message said:

Quoted message said:

Hold it!!! That IS stress relieving with a large overload with
subsequent relaxation.

Quoted message said:

it's bedding spokes into the hub and allowing any wind-up to
release, but is it metallurgical stress relief? according to
fogel's experiments, ordinary spoke tension achieves that. do you
have any evidence to support your assumption? have you tested
spokes before and after?

That's your claim. How about a new spokes in the same hub as in
rebuilding a wheel? The way you say that the spoke must keep sinking
farther and farther until it breaks through. You'll find that as was
explained earlier, a maximum contact area is reached after which
spokes do not sink farther into the flange. That point is reached
merely by tensioning the wheel before stress relief. And you say
bedding-in is what stops spokes from failing at the elbow? I doesn't
affect trueness because all spokes sink in equally withing a couple of
thousandths and do so before the wheel is fully tensioned.

Quoted message said:

Quoted message said:

Quoted message said:

The crank-arm method is also presented on Sheldon's page as a
method of stress relief and as an alternative to spoke squeezing.

Quoted message said:

Quoted message said:

I get the feeling something got lost here. The claim was that
stress relieving is not necessary.

Quoted message said:

the process is necessary to build a wheel that stays true.

....because otherwise spokes break.

Quoted message said:

Quoted message said:

Now you introduce mechanical stress relief to reduce residual
stress. What happened?

Quoted message said:

er, by definition, mechanical relief as opposed to thermal relief,
/requires/ mechanical stress does it not?

That's to cryptic. Please explain what that is about.

Quoted message said:

Quoted message said:

Quoted message said:

> Besides, it need not be exactly at yield to accelerate fatigue
> failure. Close is good enough.

Quoted message said:

Quoted message said:

Quoted message said:

Agreed. But it is also one of the premises of your account of
residual stress, as I understand it, that it be held close to
yield.

Quoted message said:

Quoted message said:

The higher the steady state stress, the greater the effect of
cyclic loading on fatigue. Therefore, the lower the stress in the
elbow (the most obvious and common point of such failures) the more
durable the wheel. No doubt there.

Quoted message said:

sorry, but there is doubt there - you need to clarify. from your
snippage, you state:

Quoted message said:

"4. That adding tension to the spoke guarantees that the stress at
the outside of the elbow remains at yield, that being the highest
load it can withstand."

Quoted message said:

the spoke is /not/ operating with the elbow at yield. if it were,
fatigue lives would be dramatically short.

.... and they fail as I mentioned.

Quoted message said:

Quoted message said:

Quoted message said:

[snip]

Quoted message said:

Quoted message said:

Quoted message said:

>> Hmm, there is also the point that jim beam made that if the
>> elbows were at yield stress or close to it in use, fatigue
>> failure would be very rapid and frequent.

Quoted message said:

Quoted message said:

Quoted message said:

> They are! We have reports of failures in less than 100 miles of
> use, but as I said, just being near the yield stress is good
> enough to cause early fatigue failures, let's say in a thousand
> miles or so.

Quoted message said:

Quoted message said:

Quoted message said:

You're saying that after I put the spokes in, correct their line,
and tension them up, they remain at yield stress in the elbow.

Quoted message said:

Quoted message said:

Yes. As I explained, there is no way that the yield stress that
changes the shape of the elbow can relax unless it it overloaded
temporarily. Without stress relief overloading, stress remains
nearly as high as it was when introduced. If you look at the
deflection plots and data in "the Bicycle Wheel" you can see that
the user cyclic loadings barely cause increased loads on spokes,
certainly not enough to constitute stress relief.

Quoted message said:

but that's a wildly disconnected assumption. use loading is one
thing. the assumption that spoke elbows are at yield is quite
another.

For you maybe, but it is evident both from the mechanics of changing
(yielding) the elbow bend and from observed resulting failures.

Quoted message said:

Quoted message said:

Quoted message said:

If I momentarily overload them (by squeezing etc.), this relieves
residual stresses. But won't they still be close to yield? The
momentary overload isn't supposed to deform them significantly, so
they should be under roughly the same amount of stress as they
were before, just without the residual stress. If not at yield,
still close to it: shouldn't this still mean very rapid fatigue
failure?

Quoted message said:

Quoted message said:

The overload is in addition to spoke tension and together these
forces cause yielding (loss of memory) for the high stress
locations that are only a few thousandths of an inch long.

Quoted message said:

1. there is no "memory" in steel jobst. not ever. there is
elasticity, there is cold work, there is even phase transformation
due to cold work, but there is no "memory".

Oh? You may be operating under a narrow definition, but springs
remember where they were before being loaded. If they exceed yield,
the lose that memory and return to another home position. In your
definition, all cars would be riding around as low-riders, sitting on
the bottoming stops.

Quoted message said:

2. where does this assumption about "few thousandths of an inch"
come from??? have you done any microscopy? have you any
evidence???? and have you done any residual stress testing?

Well, you'd better give a better number but the radius of bend and the
sector of that bend that yields is close to that size. Yielding the
highest stressed portion of that bend is a few thousandths.

I had no idea we were down to splitting hairs. What are you getting
at?

Quoted message said:

Quoted message said:

There is no significant elongation but the high stress point being
the primary tensile support yields greatly, its neighbors not doing
much of anything because the outer skin of the elbow is carrying
most of the tension. After relaxation more of the cross section
bears the load.

Quoted message said:

1. the whole structure bears the load. 2. different parts have
differing strain.

Quoted message said:

under load, the outer skin of the elbow, because of the nature of
bending, means the outer skin bears the load. that's why fatigue
/always/ initiates at the extreme of the bend.

How about not repeating what I just wrote as your contribution.

Quoted message said:

Quoted message said:

Quoted message said:

In other words, if the spokes really are close to yield at the
elbow, with or without stress relief, they will surely fail
quickly?

Quoted message said:

Quoted message said:

Yes and we hear about those here off and on.

Quoted message said:

that's fudge. /all/ spokes would be affected if they were operated
at yield. instead, the failures that get reported most frequently
here are those for spokes made of inferior material. there /is/ a
connection!

By that you mean if any spoke breaks for residual stress, all should
break and at roughly the same time. Not all spokes are equally highly
stressed and when they break in a few thousand miles, their cycles to
failure can be broad enough to obscure their relative condition. Not
many things in nature occur all at the same time because the had the
same start. Not all blades of grass are the same height nor spoke
exactly the same diameter or tension.

Quoted message said:

Quoted message said:

As I mentioned, in the days before DT and other new spokes, we used
Stella, Robergel, Redaelli, Berg and others whose fatigue
resistance was poor and most riders carried spare spokes if they
rode any longer rides.

Quoted message said:

yes, and they were made of inferior material, no vacuum degassing,
and worse, a lot were chrome plated, a guaranteed fatigue initiator.

The ones I mentioned offered stainless spokes that were not chromed.

Quoted message said:

Quoted message said:

The stress relief methods I outlined were developed because
improved durability was so striking.

Quoted message said:

evidence. do not confuse subsequent improvement in material quality
with effects of "stress relief". you need proper "before and after"
statistics for that.

The same spoke complement in wheels that previously had spokes fail
ceased to fail. You might look that up. I have repeated that for you
a few times because you conveniently forget that it was so.

Quoted message said:

Quoted message said:

The threshold between spokes that broke and ones that didn't was so
narrow that the benefits of stress relief was obvious.

Quoted message said:

data. stats. must publish, not make presumption masquerade for

fact.

I haven't seen anything that you measured, computed or published. It
may be time to do so instead of sniping endlessly from anonymity.

Quoted message said:

Quoted message said:

With better spokes that can operate closer to yield stress this is
less apparent but still present.

Quoted message said:

less apparent???

Let's say it doesn't jump out at someone who is not keeping track of
the sequence of events that reduced spoke failure on a set of wheels.

Quoted message said:

Quoted message said:

Quoted message said:

[snip]

Quoted message said:

Quoted message said:

Quoted message said:

>>>>>>> It fails because there are high stress points at that place
>>>>>>> and that spokes that don't break must have lower stress.
>>>>>>> The lower stress is achieved by stress relief and that this
>>>>>>> is possible by mechanical means has also been explained in
>>>>>>> great detail.

Quoted message said:

Quoted message said:

Quoted message said:

>>>>>> I do believe it's possible. But so are alien abductions,
>>>>>> and I don't think they happen.

Quoted message said:

Quoted message said:

Quoted message said:

>>>>> Why don't you believe that is possible?

Quoted message said:

Quoted message said:

Quoted message said:

>>>> I said I _do_ believe it's possible.

Quoted message said:

Quoted message said:

Quoted message said:

>>> As possible as alien abductions... I don't understand what you
>mean.

Quoted message said:

Quoted message said:

Quoted message said:

>> Alien abductions _are_ possible, it's just that the evidence for
>> them is very poor and that there are many more probable
>> explanations for the accounts people give.

Quoted message said:

Quoted message said:

Quoted message said:

> OK, that fits the description of spurious failure causes
> adequately.

Quoted message said:

Quoted message said:

Quoted message said:

Good, so we agree on that then.

Quoted message said:

Quoted message said:

Onward!

Quoted message said:

unfortunately, not much progress is evident.

Quoted message said:

i think the reason for your preoccupation with residual stress stems
from your belief that elasticity is evidence of it. that is
incorrect.

Don't put your beliefs in my basket. The way you go about this is an
entirely negative manner, offering no solutions or explanations for
your beliefs. I use the term residual stress for stresses not caused
by spoke tension or relaxation of it, but built in spring loads
remaining from forming. You may be aware of the experiment of a
relaxed spring and a stressed spring in an acid bath in which the
stressed one dissolved faster. That is residual stress at work. In
fact a freshly formed coil spring dissolves faster than one that has
been heat treated and thereby stress relieved.

Some residual stress remains in the threads and most in the elbow, it
being the most stretched part in the spoke, having been bent in a
small radius to near 90° and then bent further under tension.

Quoted message said:

reality is, elasticity is just that, elasticity. residual stress,
being entirely internal, cannot manifest itself outside the
structure unless there is a means by which it can express itself.
this includes things like heat, machining and corrosion. it can
potentially also be expressed with a depressed yield point on
plastic deformation, but that would have to be in conjunction with
another agent since the unyielded structure must be in equilibrium.

Quoted message said:

again, springback is /not/ evidence of residual stress. the primary
causes of spoke fatigue are bending which is affected by mechanical
configuration, surface finish/process quality and material quality.

It is if it is not a working stress of the spoke but introduced by
forming. A loaded spring has stress and if that is not caused by its
operating load, it is a residual stress.

Jobst Brandt