removing broken spoke nipples

  • Thread starter Bellsouth Ijit 2.0
  • Start date



B

Ben C

Guest
On 2007-03-14, jim beam <[email protected]> wrote:
> Ben C wrote:
>> On 2007-03-14, jim beam <[email protected]> wrote:

[...]
>>> to say that mechanical stress is reduced because the origin has
>>> shifted is also incorrect in the context of wheelbuilding because
>>> stress will have to be re-increased back to the desired pre-tension
>>> level.

>>
>> On the whole spoke, yes, but not on the individual "fibres" that have
>> deformed during stress relief? They've strained a bit and are therefore
>> under less tensile stress.
>>
>> Anyway I thought you were supposed to stress-relieve after final
>> tensioning. So there's an overload from desired pre-tension and relax
>> back to desired pre-tension. What's the re-increase?

>
> all the yielding /during/ build and "stress relief" will deform hub
> holes and therefore move origin. after all is seated, there is no more
> deformation so no more "stress relief". "stress relief" /after/ final
> tensioning will achieve nothing if previous work was done right.


Yes indeed, but this is a different scenario. This could happen, the
stress-relief scenario could also happen, or a bit of both depending on
the components used. Whether those elbows remain close to yield after
the build is not currently known. We need an X-ray diffractor and lots
of test wheels to settle that one.
 
want nucleating?
build with generic spokes
go to walmort for those can lids
loadem on the rear rack
and run over 2-3 curbs
gentley
and yagot nucleating big time!
 
BENC: asked JBeam- What's the re-increase?-

when Jbeam wrote:. to say
that mechanical stress is reduced because the origin has shifted is
also
incorrect in the context of wheelbuilding because stress will have to
be
re-increased back to the desired pre-tension level.

well, down here in group 2, sissy method stress relief followed with a
road test is then followed by a retruing and general tightening
usually on the order of a 1/4 turn.

if the relieves let the spokes "set", assume the spokes are setting
taking the shortest route possible, making the spokes effectively
longer than when taking the wheel off the stand.

or did i miss the poitn?
 
J

jim beam

Guest
[email protected] wrote:
> want nucleating?
> build with generic spokes
> go to walmort for those can lids
> loadem on the rear rack
> and run over 2-3 curbs
> gentley
> and yagot nucleating big time!
>
>

indeed.
 
J

jim beam

Guest
[email protected] wrote:
>> indeed. yes. visualizing what's going on there is simpler now.

> have you visited earthquake geology language?
>
>

no, i just live in california.
 
L

Luns Tee

Guest
In article <[email protected]>,
jim beam <[email protected]> wrote:
>Luns Tee wrote:
>> You have a selective memory. If the word 'partial' is a step
>> forward, then it's a step for you alone, though that said, I'm glad to
>> see you catching up with reality. It's been there for years, even in
>> postings that you've yourself responded to, yet up until now, you've
>> been blind to it and omit it time after time in your own
>> representations of what's said.


>but dude, this whole springback thing is "confused" reasoning - that's
>why it's necessary to debate it.


The only thing confused here is your habit of omitting key
elements, misinterpreting what remains, then trying to throw the baby
out with the bathwater.

> as stated before, springback is
>elasticity. "partial" springback is elasticity plus deformation.


Fine.

>it's
>the _deformation_ that "implies" residual stress, _not_ the springback.
> indeed "springback" shouldn't even be in any such argument as it's
>/not/ "evidence" of residual stress.


There you've done it again - once again, you've left out the key
word of _partial_. Nobody's ever claimed that the existance of springback
proves anything. The springback is a given, what proves the residual
stress is the fact that the springback is partial.
Any unyielded material has stress in it unless its allowed to spring
back to zero, and since the springback is partial, this means the unyielded
material is under residual stress. This stress in the unyielded material
is held there by complementary stress in the yielded material.

>and deformation only is by assumption.


What's that supposed to mean? If an elbow is bent into the spoke
in manufacture and does not spring back to being straight, I don't see
how you can call it 'only an assumption' that material in the elbow
has yielded.

-Luns
 
B

Ben C

Guest
On 2007-03-17, jim beam <[email protected]> wrote:
> jim beam wrote:
>> Luns Tee wrote:

[...]
>>> The
>>> unyielded material takes up additional tension as you move from this
>>> origin, this extra tension previously being carried by the now yielded
>>> material.

>>
>> correct.

>
> oops, typo. INcorrect. see reason below.
>
>>
>>> When you get back to the target tension, the unyielded
>>> material carries more of the tension than it started with, and the
>>> yielded material carries that much less.

>>
>> no - that description implies load [tension] being regional - it's the
>> stress /magnitude/, that's regionally affected by residual stress.


Stress is tension per unit of cross-sectional area. In a reasonably
ideal world, total tension and average stress for the whole wire are the
same before and after stress relief, but the distribution of stress
throughout the cross section is what's changed.

If this is right, then if we talk about different regions of the cross
section carrying more or less of the tension, isn't that saying the same
thing? We're just discussing the tension per region of the
cross-section, which is basically the same concept as stress.

>> load strain, unless yielding occurs, is unaffected by residual
>> stress.
 
B

Ben C

Guest
On 2007-03-17, Luns Tee <[email protected]> wrote:
[...]
> No, it's keeping things in the proper perspective. You were
> claiming that stress increases back to where it started when you
> increase tension back to what the structure needs. The tension lost
> is the stress lost by yield times the sectional area of the yielded
> material. Putting the tension back, tensile stress increases by this
> same delta, divided by the sectional area of the entire spoke. Unless
> the entire spoke yielded, this increase in stress is less than the
> reduction from the yield.


I think I've been missing something. Are you suggesting that after
stress relief, the spoke tension is noticeably reduced a bit, and you
need to give the spokes another 1/4 turn or so?

This might be what jim beam meant by the "re-increase".

I didn't think it was necessary though-- stress relief causes almost
immeasurably small deformation, so surely also only a very small change
in tension?

I take your point that even if you do re-tension after stress relief,
the maximum stress over the cross-section should remain lower than it
was before stress relief.
 
J

jim beam

Guest
Ben C wrote:
> On 2007-03-17, jim beam <[email protected]> wrote:
>> jim beam wrote:
>>> Luns Tee wrote:

> [...]
>>>> The
>>>> unyielded material takes up additional tension as you move from this
>>>> origin, this extra tension previously being carried by the now yielded
>>>> material.
>>> correct.

>> oops, typo. INcorrect. see reason below.
>>
>>>> When you get back to the target tension, the unyielded
>>>> material carries more of the tension than it started with, and the
>>>> yielded material carries that much less.
>>> no - that description implies load [tension] being regional - it's the
>>> stress /magnitude/, that's regionally affected by residual stress.

>
> Stress is tension per unit of cross-sectional area. In a reasonably
> ideal world, total tension and average stress for the whole wire are the
> same before and after stress relief, but the distribution of stress
> throughout the cross section is what's changed.


distribution, yes.

>
> If this is right, then if we talk about different regions of the cross
> section carrying more or less of the tension, isn't that saying the same
> thing?


no. because a region has more local stress, doesn't mean it's bearing
more of the applied load. the strain delta dictates load bearing and
the strain delta is the same.

> We're just discussing the tension per region of the
> cross-section, which is basically the same concept as stress.


no, if confused, consider strain instead.

>
>>> load strain, unless yielding occurs, is unaffected by residual
>>> stress.
 
J

jim beam

Guest
jim beam wrote:
> [email protected] wrote:
>> Lateral load CAN increase spoke tension but seldom does. Typically
>> when leaning the bicycle while climbing or sprinting, standing, even
>> with large lean angles, spokes are slackened on the high side while
>> tension does not increase on the low side because it is these spokes
>> that are carrying the vertical load and are naturally slackened.
>>
>> The hazard in this is that as the high side spokes become completely
>> slack, lateral wheel stiffness is cut in half

>
> no, the lateral bracing /offered by spoke support/ is cut in half.


lateral bracing is also a function of the spoke angle.

> the
> rim's own stiffness is still significant, so while overall stiffness is
> /reduced/, it's not "cut in half".
>
>> and can easily cause
>> collapse...

>
> not unless spoke tension is excessive. the only rim i've ever collapsed
> was one with excess tension. my "205lbs" rim, *unspoked*, will support
> my full body weight, let alone slack spoked.
>
>> and with fewer spokes even more so. Lateral bending
>> strength of deep aero rims, that can bridge large spoke-to-spoke
>> distances for vertical loads, is not significantly higher than
>> rectangular cross section rims, their width being the same.

>
> that's not true either. deeper rims alone are stiffer. measure them.
> for built wheels using deep rims, using fewer spokes merely reduces
> overall wheel stiffness to that of a higher spoked shallower rim wheel.
>
>>
>> This all boils down to that spokes in most loading are acting in
>> tension and that their tension changes behave like compression
>> elements until the preload is exceeded. At that point they no longer
>> contribute to the strength of the wheel.
>>
>> Jobst Brandt
 
J

jim beam

Guest
Ben C wrote:
> On 2007-03-17, Luns Tee <[email protected]> wrote:
> [...]
>> No, it's keeping things in the proper perspective. You were
>> claiming that stress increases back to where it started when you
>> increase tension back to what the structure needs. The tension lost
>> is the stress lost by yield times the sectional area of the yielded
>> material. Putting the tension back, tensile stress increases by this
>> same delta, divided by the sectional area of the entire spoke. Unless
>> the entire spoke yielded, this increase in stress is less than the
>> reduction from the yield.

>
> I think I've been missing something. Are you suggesting that after
> stress relief, the spoke tension is noticeably reduced a bit, and you
> need to give the spokes another 1/4 turn or so?
>
> This might be what jim beam meant by the "re-increase".


yes it is.

>
> I didn't think it was necessary though-- stress relief causes almost
> immeasurably small deformation, so surely also only a very small change
> in tension?


tension change can be significant in the early stages - spokes bedding
into their hub holes is similar to brinell ball indentation.

>
> I take your point that even if you do re-tension after stress relief,
> the maximum stress over the cross-section should remain lower than it
> was before stress relief.


not if the applied stress is re-increased beck to original.
 
T

Tim McNamara

Guest
In article <[email protected]>,
jim beam <[email protected]> wrote:

Oh, dear. There you go again. Your standard practice is to distort
what others say, and then to refute the distorted version rather than
what the person actually wrote, and then you persuade yourself that
you've won the argument. It's called a straw man fallacy, which you use
so much that you had best stay away from open flames.

This is what makes you a liar and a fraud, by the way. It's sad,
because you might be right about stuff. But you are so focused on
taking down Jobst (and also Krygowski and Annan) that you fail to
contribute meaningfully to the discussions. Instead of providing useful
information, you merely aim to discredit.

Ethical and knowledgeable contributors use their knowledge to help
explain things and make it understandable to others, You use yours as a
club to demean others. Your participation here has nothing to do with
advancing the collective understanding and everything to do with your
bitterness and your ego trip.

> you're insane if you think your inability to study and understand math
> and engineering principles give you the ability to write **** like that.


I am quite aware that my knowledge of engineering is minimal, jim.
That's why I appreciate engineers who can write in plain English- after
all, as Feynmann pointed out, "if you can't explain it in plain English
you don't understand it yourself." Fortunately there are plain language
descriptions of most engineering principles that are easily found on the
Internets using the Google, so I can fill in some of the gaps in my
understanding when they present themselves. I also appreciate the
engineers who provide ways to check things out at home in a simple and
straightforward manner- something I don't recall you ever doing.

> your b.s. about "ejection" force exceeding retention force was a
> peach, especially when you kept on repeating it. but your subsequent
> howlers about iso standards being "regulations" and minimums being
> maximums -


More of your distortions and lies. First, I was talking about CPSC
regulations not ISO standards, and I made that very clear in the context
(identifying them specifically as CPSC regulations and providing the
link to the regulations themselves). Second, I never confused minimums
and maximums; you did that in at attempt to discredit and obfuscate when
it was clear that the facts didn't back up your position. You will
never win by lying. Haven't you learned that by now?

> well dude, you do ahead and shroud your fragile little mind
> in all kinds of excuse, but the fact is, you're not qualified to endorse
> the use of toilet paper, let alone anything with numbers attached to it.


Back to base ad hominem and invective, evidence again of the weakness of
your position and your logical armamentarium. And perhaps also evidence
of some some things about your personality and character as well.

> you're utterly innumerate.


Not utterly, no. I can do arithmetic, basic algebra and have a good
understanding of statistics (since that applies directly to my field of
science, it was required in graduate school). I have never had a need
to learn advanced mathematics so I can't do that stuff, and as a result
can't always follow Luns's math. From what you've posted it looks like
you can't follow it either. In fact, come to think of it, your
participation pretty much disappears when the heavy math comes out.
What's up with that? Perhaps you are not as numerate as you pretend.
 
J

jim beam

Guest
Tim McNamara wrote:
> In article <[email protected]>,
> jim beam <[email protected]> wrote:
>
> Oh, dear. There you go again. Your standard practice is to distort
> what others say, and then to refute the distorted version rather than
> what the person actually wrote, and then you persuade yourself that
> you've won the argument. It's called a straw man fallacy, which you use
> so much that you had best stay away from open flames.
>
> This is what makes you a liar and a fraud, by the way. It's sad,
> because you might be right about stuff. But you are so focused on
> taking down Jobst (and also Krygowski and Annan) that you fail to
> contribute meaningfully to the discussions. Instead of providing useful
> information, you merely aim to discredit.


i present facts. the facts peak for themselves. i contest ********.
and brown nosing.

>
> Ethical and knowledgeable contributors use their knowledge to help
> explain things and make it understandable to others, You use yours as a
> club to demean others. Your participation here has nothing to do with
> advancing the collective understanding and everything to do with your
> bitterness and your ego trip.
>
>> you're insane if you think your inability to study and understand math
>> and engineering principles give you the ability to write **** like that.

>
> I am quite aware that my knowledge of engineering is minimal, jim.


no ****. but it sure doesn't stop you expressing underinformed opinion!

> That's why I appreciate engineers who can write in plain English- after
> all, as Feynmann pointed out, "if you can't explain it in plain English
> you don't understand it yourself."


that's ******** you sycophantic brown nose. by your twisted logic,
jobst writing "in plain english" [and quoting feynmann] that bearings
don't brinell is acceptable [to pick just one example], even when it's
fact that they do. utter ****-sucking ********.

> Fortunately there are plain language
> descriptions of most engineering principles that are easily found on the
> Internets using the Google, so I can fill in some of the gaps in my
> understanding when they present themselves. I also appreciate the
> engineers who provide ways to check things out at home in a simple and
> straightforward manner- something I don't recall you ever doing.


no, you get bamboozled by ******** because you don't know any different.
and worse, you defend your ignorance!

>
>> your b.s. about "ejection" force exceeding retention force was a
>> peach, especially when you kept on repeating it. but your subsequent
>> howlers about iso standards being "regulations" and minimums being
>> maximums -

>
> More of your distortions and lies. First, I was talking about CPSC
> regulations not ISO standards, and I made that very clear in the context
> (identifying them specifically as CPSC regulations and providing the
> link to the regulations themselves).


really? you cited cpsc linkage? funny, my news reader seems to have
edited that out. and annan doesn't cite cpsc, he quotes iso.

> Second, I never confused minimums
> and maximums; you did that in at attempt to discredit and obfuscate when
> it was clear that the facts didn't back up your position. You will
> never win by lying. Haven't you learned that by now?


********.

"Those regulations set a minimum standard for the maximum practical
clamping force that can be achieved with the skewer."

there's nothing maximal about a minimal standard.

>
>> well dude, you do ahead and shroud your fragile little mind
>> in all kinds of excuse, but the fact is, you're not qualified to endorse
>> the use of toilet paper, let alone anything with numbers attached to it.

>
> Back to base ad hominem and invective, evidence again of the weakness of
> your position and your logical armamentarium. And perhaps also evidence
> of some some things about your personality and character as well.
>
>> you're utterly innumerate.

>
> Not utterly, no.


really? so is 1600N > 5000N?

> I can do arithmetic, basic algebra and have a good
> understanding of statistics (since that applies directly to my field of
> science, it was required in graduate school). I have never had a need
> to learn advanced mathematics so I can't do that stuff, and as a result
> can't always follow Luns's math. From what you've posted it looks like
> you can't follow it either. In fact, come to think of it, your
> participation pretty much disappears when the heavy math comes out.
> What's up with that? Perhaps you are not as numerate as you pretend.


yeah, i'm a real dumb-ass. and a photo fraud. and you're real useful
with all those fine technical contributions you make. go back to the
bedroom brown-nose. your master awaits.
 
B

Ben C

Guest
On 2007-03-17, jim beam <[email protected]> wrote:
> Ben C wrote:
>> On 2007-03-17, Luns Tee <[email protected]> wrote:
>> [...]
>>> No, it's keeping things in the proper perspective. You were
>>> claiming that stress increases back to where it started when you
>>> increase tension back to what the structure needs. The tension lost
>>> is the stress lost by yield times the sectional area of the yielded
>>> material. Putting the tension back, tensile stress increases by this
>>> same delta, divided by the sectional area of the entire spoke. Unless
>>> the entire spoke yielded, this increase in stress is less than the
>>> reduction from the yield.

>>
>> I think I've been missing something. Are you suggesting that after
>> stress relief, the spoke tension is noticeably reduced a bit, and you
>> need to give the spokes another 1/4 turn or so?
>>
>> This might be what jim beam meant by the "re-increase".

>
> yes it is.
>
>>
>> I didn't think it was necessary though-- stress relief causes almost
>> immeasurably small deformation, so surely also only a very small change
>> in tension?

>
> tension change can be significant in the early stages - spokes bedding
> into their hub holes is similar to brinell ball indentation.


Not only that but in the early stages doing something like the Mavic
method may also be changing the elbow bend angles which will drop the
tension quite a bit.

I should have made it clearer, but I thought we were talking about a
final overload after full tensioning, just to yield the outside of the
elbows in case they've ended up held close to yield stress by spoke
tension.

>> I take your point that even if you do re-tension after stress relief,
>> the maximum stress over the cross-section should remain lower than it
>> was before stress relief.

>
> not if the applied stress is re-increased beck to original.


If we're talking about bending stress at the elbow, then, yes,
increasing spoke tension may bring the elbows back to yield. It might be
harder this time around to reach yield though because bedding/bending
might have reduced the moment on the elbow.

My understanding of what Luns was saying is that if we had an uneven
distribution of stress in the wire, which we evened out a bit by stress
relief, then when we load the wire again tension will increase, but
uniformly, resulting in lower peak regional stress for the same tension
when we've finished.

I think that's true, but if the re-increase is not uniform, but a
bending stress, then we will bring the outside of the elbow straight
back to yield, and we will be back to square one.

Practically speaking if you have to retension after stress relief you
would be advised to stress relieve again.
 
B

Ben C

Guest
On 2007-03-17, Tim McNamara <[email protected]> wrote:
> In article <[email protected]>,
> jim beam <[email protected]> wrote:

[...]
> Second, I never confused minimums and maximums;


I nearly always get min and max the wrong way around the first time I
use them. I think I suffer from a kind of min/max dyslexia. I heard
somewhere though that if you actually go through all the maths in a
maths paper carefully you invariably find a large number of sign errors
(-x instead of x, etc.), but always an even number of them!
 
B

Ben C

Guest
On 2007-03-17, jim beam <[email protected]> wrote:
> Ben C wrote:

[...]
>> Stress is tension per unit of cross-sectional area. In a reasonably
>> ideal world, total tension and average stress for the whole wire are the
>> same before and after stress relief, but the distribution of stress
>> throughout the cross section is what's changed.

>
> distribution, yes.
>
>>
>> If this is right, then if we talk about different regions of the cross
>> section carrying more or less of the tension, isn't that saying the same
>> thing?

>
> no. because a region has more local stress, doesn't mean it's bearing
> more of the applied load.
>
> the strain delta dictates load bearing and the strain delta is the
> same.


I think I get it: the key point here is that not all of the stress comes
from the load. Suppose you do have residual stresses from forming, those
give you localized regions of higher and lower stresses inside the wire
even when there's no external load on it at all. Apply some load, and it
doesn't follow that the higher stressed regions are bearing more of that
load. In fact it's probably borne fairly evenly across the wire,
although you've got details like the fact that the nipple is gripping
the spoke on its outside surface.

The applied stress is just superimposed on top of any stresses that
might already be there (from bits of the interior fighting each other
for example).
 
Ben C? writes:

> Not only that but in the early stages doing something like the Mavic
> method may also be changing the elbow bend angles which will drop
> the tension quite a bit.


> I should have made it clearer, but I thought we were talking about a
> final overload after full tensioning, just to yield the outside of
> the elbows in case they've ended up held close to yield stress by
> spoke tension.


>>> I take your point that even if you do re-tension after stress
>>> relief, the maximum stress over the cross-section should remain
>>> lower than it was before stress relief.


>> not if the applied stress is re-increased beck to original.


> If we're talking about bending stress at the elbow, then, yes,
> increasing spoke tension may bring the elbows back to yield. It
> might be harder this time around to reach yield though because
> bedding/bending might have reduced the moment on the elbow.


> My understanding of what Luns was saying is that if we had an uneven
> distribution of stress in the wire, which we evened out a bit by
> stress relief, then when we load the wire again tension will
> increase, but uniformly, resulting in lower peak regional stress for
> the same tension when we've finished.


> I think that's true, but if the re-increase is not uniform, but a
> bending stress, then we will bring the outside of the elbow straight
> back to yield, and we will be back to square one.


> Practically speaking if you have to re-tension after stress relief
> you would be advised to stress relieve again.


I think you should review what sort of yield stress relief causes.
These are length changes of microns while the spoke as a whole is
elastically stretched on the order of a millimeter, there is no
practically measurable change in length or in tension in spokes from
stress relieving.

Your suggestion that spokes need re-tensioning after stress relief is
misplaced. Spokes do not sink into the flanges further after
tensioning when stress relieved enough to affect tension. By that
point in the wheel build they have asymptotically reached home
position.

Jobst Brandt
 
Ben C? writes:

>>> Stress is tension per unit of cross-sectional area. In a
>>> reasonably ideal world, total tension and average stress for the
>>> whole wire are the same before and after stress relief, but the
>>> distribution of stress throughout the cross section is what's
>>> changed.


>> distribution, yes.


>>> If this is right, then if we talk about different regions of the
>>> cross section carrying more or less of the tension, isn't that
>>> saying the same thing?


>> no. because a region has more local stress, doesn't mean it's
>> bearing more of the applied load.


>> the strain delta dictates load bearing and the strain delta is the
>> same.


> I think I get it: the key point here is that not all of the stress
> comes from the load. Suppose you do have residual stresses from
> forming, those give you localized regions of higher and lower
> stresses inside the wire even when there's no external load on it at
> all. Apply some load, and it doesn't follow that the higher stressed
> regions are bearing more of that load. In fact it's probably borne
> fairly evenly across the wire, although you've got details like the
> fact that the nipple is gripping the spoke on its outside surface.


> The applied stress is just superimposed on top of any stresses that
> might already be there (from bits of the interior fighting each
> other for example).


What you say is based on the assumption that spoke tension increases
in a wheel in use. Unless you are using too few spokes for a reliable
wheel, spoke tension does not increase in a wheel enough to have any
effect on residual stress. You can review the relative stresses in
graphs and data in "the Bicycle Wheel" to reassure yourself of that.

Jobst Brandt