Yet another broken spoke

[Peter Cole]

Ben C wrote:
> On 2007-09-07, Peter Cole <[email protected]> wrote:
> [...]
>> If the spoke has no bending moment (perfectly supported, perfect path),
>> the applied stress from spoke tension will be tensile (uniform) across
>> the cross section.
>
> I think I basically agree with this, though not absolutely. If the spoke
> is perfectly supported, but being pulled around a corner, there will
> surely still be a bending moment on parts of the spoke, but the distance
> component of that moment will never be greater than half the diameter of
> the spoke.
>

It's theoretically possible to have the elbow perfectly supported such
that there would be no moment. In practice, there must be a little slop
to lace with.


> Moments that small (assuming the force is in the range of normal spoke
> tensions) are low enough not to worry about-- they're not bringing
> anything anywhere near dangerously high stress levels for fatigue.
>
>> Whatever bending force that is also present will add
>> to that. The bending force can be either way depending on angular
>> mismatch. If the spoke elbow is too long, another bending force will act
>> to open the spoke angle further, adding to the residual (mfg) stress.
>>
>> The worst case would be an (initial spoke) angle too acute with elbow
>> too long. Both of those factors plus residual stress would all put
>> tension on the inside of the elbow.
>
> Yes, in that case residual stress from forming would be the same way
> around as applied bending from spoke tension-- i.e. compressive outside
> the bend, tensile inside.
>
>> If the spoke elbows are the right length, and the spoke angle is
>> corrected, the only significant stresses should be spoke tension and
>> residual.
>
> But if you correct the spoke angle, you're changing things right? It was
> bent in the factory by a little piston or whatever, and wants to spring
> back, leaving it with residual stresses. Then you go and bend it again
> to make the elbow a bit bigger or smaller. What happens to the residual
> stresses from the factory?

Typically, you're correcting the spoke angle on the outbound spokes,
closing the angle slightly. I doubt that this reduces residual
manufacturing stresses.


> I imagine they reduce greatly in magnitude and move around a bit. I
> imagine you'd have to hunt around quite a bit with the X-ray diffractor
> to find them and distinguish them from the new applied stresses you've
> just put in.

Reversing the bend direction and lowering the magnitude cyclically to
zero is a way of straightening wire. I would imagine that this would
reduce residuals, but I don't know for sure.

>
>> By stress relieving, the residual is reduced to non-fatiguing levels.
>> But, if the spoke has (tensile) stress levels near yield in parts of
>> the cross section, those will be reduced as they are forced to yield
>> by the momentary overload -- whatever the source. It's a "can't lose"
>> proposition.
>
> I would have thought so, yes, unless you really overdo it.

It's pretty impossible to overdo it, your hands aren't strong enough.

 

[jim beam]

Peter Cole wrote:
> jim beam wrote:
>> Peter Cole wrote:
>>> Ben C wrote:
>>>> On 2007-09-07, Peter Cole <[email protected]> wrote:
>>>> [...]
>>>>> It was over 4 years ago. I thought Mike Prime (a metallurgist) did
>>>>> a good job. Apparently it didn't stick. I can see why Jobst no
>>>>> longer bothers to respond.
>>>>>
>>>>> http://tinyurl.com/29v4u2
>>>>
>>>> OK I have a question.
>>>>
>>>> jim beam> i have ignored residual stress as a factor in these failures
>>>> jim beam> because the majority of the fractures i've examined initiate
>>>> jim beam> on the /inside/ of the spoke elbow bend, not the outside
>>>> jim beam> [although i have examples of each]. residual stress in this
>>>> jim beam> location is compressive so i'm just looking at the external
>>>> jim beam> [+cyclic] load. Mike Prime> The inside of the spoke elbow
>>>> will have TENSILE residual
>>>> Mike Prime> stress, not compressive, because of the elastic springback
>>>> Mike Prime> after bending. See below. That 0.5 Sy number is for a beam;
>>>> Mike Prime> I'm too lazy to derive the number for a circular cross
>>>> Mike Prime> section right now.
>>>>
>>>> Mike Prime> Since that location has tensile residual stress, tensile
>>>> Mike Prime> applied mean stress from the spoke tension and bending,
>>>> ^^^^^^^
>>>>
>>>> Is the _applied_ stress on the inside of the elbow from spoke tension
>>>> and bending really tensile?
>>>>
>>>> I don't understand that. I thought when you bent a wire you got tensile
>>>> stress on the outside of the bend and compressive on the inside?
>>>>
>>>> I know that the residual stress, after it springs back, is tensile on
>>>> the inside.
>>>
>>> If the spoke has no bending moment (perfectly supported, perfect
>>> path), the applied stress from spoke tension will be tensile
>>> (uniform) across the cross section. Whatever bending force that is
>>> also present will add to that. The bending force can be either way
>>> depending on angular mismatch. If the spoke elbow is too long,
>>> another bending force will act to open the spoke angle further,
>>> adding to the residual (mfg) stress.
>>
>> but you're ignoring the actual residual stress profile. just alluding
>> to residual stress being possible doesn't mean it's actually
>> nucleating fatigue!
>
> No, I'm not. You cited Luns in the context of stress profile, as far as
> I could see he only confirmed Jobst's explanation and rejected yours.
> I'm the only one on this NG (as far as I know) who actually tried to
> measure residual stress, and found my results agreed with predictions:
>
> http://tinyurl.com/356ru7

<snip remaining ****>


eh? are you stupid? if you think that fatigue cracking that initiates
in locations where there is little or no residual stress, either
positive or negative, is /caused/ by that residual stress, you have a
profound lack of understanding. but why am i wasting my time - you
don't understand the difference between plasticity and elasticity -
fatigue is well beyond you.

 

[jim beam]

Peter Cole wrote:
> Ben C wrote:
<snip for clarity>

>> I would have thought so, yes, unless you really overdo it.
>
> It's pretty impossible to overdo it, your hands aren't strong enough.

eh? translation: "it yields to cause 'stress relief' but it doesn't
yield if that interferes with my ability to argue."

what a crock of ****.

 

[Ben C]

On 2007-09-08, jim beam <[email protected]> wrote:
> Ben C wrote:
>> On 2007-09-07, Peter Cole <[email protected]> wrote:
>> [...]
>>> If the spoke has no bending moment (perfectly supported, perfect path),
>>> the applied stress from spoke tension will be tensile (uniform) across
>>> the cross section.
>>
>> I think I basically agree with this, though not absolutely. If the spoke
>> is perfectly supported, but being pulled around a corner, there will
>> surely still be a bending moment on parts of the spoke, but the distance
>> component of that moment will never be greater than half the diameter of
>> the spoke.
>>
>> Moments that small (assuming the force is in the range of normal spoke
>> tensions) are low enough not to worry about-- they're not bringing
>> anything anywhere near dangerously high stress levels for fatigue.
>
> don't forget, virtually every fatigue failure there's ever been is
> because of "unanticipated" factors. just because stress levels aren't
> /thought/ to be high, *observed failures* tell us that there /is/
> bending sufficient to cause fatigue!!!

Yes, although doesn't it depend what you mean by "cause"? There is
always some bending unless you have a straight pull spoke. If the mean
stress in that bending cycle is low then you should get a long life
unless you've got very bad surface defects.

On the other hand if the mean stress is high (e.g. because you have a
big bending moment), but the surface is much better, you might also get
a short life.

It's quite believable to me that wear resulting in corrosion that
nucleated fatigue was a big factor in Clare's failed galvanized spokes,
even if the stress cycle on them wasn't too big. But if someone's nice
new stainless DT spokes in an Al hub fail after a few 100km then
retained stress from the build or a big moment at the elbow look more to
blame.

In both cases there's bending and in both cases presumably the fatigue
starts somewhere. So the same basic mechanism, but it's reasonable to
blame or suspect the surface quality in the first case and the high
stresses in the second.

 

[Ben C]

On 2007-09-08, jim beam <[email protected]> wrote:
> Ben C wrote:
>> On 2007-09-08, jim beam <[email protected]> wrote:
>>> [email protected] wrote:
>> [...]
>>>> As I mentioned, don't fly your kite on every breeze that comes along,
>>>> especially those sent aloft by jb.
>>> as opposed to red herrings by JB?
>>
>> Please both of you calm down. I'm not about to fly any kites OR swallow
>> any herrings. You are both much better at explaining things when you
>> aren't blinded by paranoia or rage respectively.
>
> so what's the question?

See the other thread, which you already have done. Thank you.

 

[Ben C]

On 2007-09-08, Peter Cole <[email protected]> wrote:
> Ben C wrote:
>> On 2007-09-07, Peter Cole <[email protected]> wrote:
>> [...]
>>> If the spoke has no bending moment (perfectly supported, perfect path),
>>> the applied stress from spoke tension will be tensile (uniform) across
>>> the cross section.
>>
>> I think I basically agree with this, though not absolutely. If the spoke
>> is perfectly supported, but being pulled around a corner, there will
>> surely still be a bending moment on parts of the spoke, but the distance
>> component of that moment will never be greater than half the diameter of
>> the spoke.
>>
>
> It's theoretically possible to have the elbow perfectly supported such
> that there would be no moment.

If the spoke goes round a corner and you pull on it, then the corner
will resist the pull and you will have (I think) compression on that
side-- the inside of the bend-- and tension on the outside. So that is a
sort of moment, depending on where you measure things from.

If you have a bad surface covered uniformly with defects, but a well
supported spoke you still might see fatigue starting on the outside of
the bend where the tensile stress in use is the highest. I think this is
what jim beam was saying in another post.

> In practice, there must be a little slop to lace with.

Yes, and in practice nothing's ever perfect anyway.

[...]
>> But if you correct the spoke angle, you're changing things right? It was
>> bent in the factory by a little piston or whatever, and wants to spring
>> back, leaving it with residual stresses. Then you go and bend it again
>> to make the elbow a bit bigger or smaller. What happens to the residual
>> stresses from the factory?
>
> Typically, you're correcting the spoke angle on the outbound spokes,
> closing the angle slightly. I doubt that this reduces residual
> manufacturing stresses.

But isn't the residual manufacturing stress on the skin of the spoke
on the outside of the elbow compressive? So tightening the angle will
put a tensile stress there, overcoming the residual compressive stress
and then yielding the material in a tensile way?

[...]
>>> By stress relieving, the residual is reduced to non-fatiguing levels.
>>> But, if the spoke has (tensile) stress levels near yield in parts of
>>> the cross section, those will be reduced as they are forced to yield
>>> by the momentary overload -- whatever the source. It's a "can't lose"
>>> proposition.
>>
>> I would have thought so, yes, unless you really overdo it.
>
> It's pretty impossible to overdo it, your hands aren't strong enough.

Yes I think so, as you're only going to yield the portions that are
close to yield already. To yield a well supported spoke takes much more
force.

 

[Ben C]

On 2007-09-08, jim beam <[email protected]> wrote:
> Peter Cole wrote:
>> Ben C wrote:
><snip for clarity>
>
>>> I would have thought so, yes, unless you really overdo it.
>>
>> It's pretty impossible to overdo it, your hands aren't strong enough.
>
> eh? translation: "it yields to cause 'stress relief' but it doesn't
> yield if that interferes with my ability to argue."

Isn't the point that if part of the spoke is close to yield, because
it's just been bent while you were building the wheel, then you can
bring that part up to yield with a relatively small amount more force?

Of course the only reason you can ever yield a spoke with your hands is
by bending it. As you yield it some more, the configuration changes and
the moment is reduced. So it's difficult to over-yield it. It's not like
bending a coathanger backwards and forwards.

 

[Peter Cole]

jim beam wrote:
> but why am i wasting my time - you
> don't understand the difference between plasticity and elasticity -
> fatigue is well beyond you.


Don't go away mad....

 

[jim beam]

Ben C wrote:
> On 2007-09-08, jim beam <[email protected]> wrote:
>> Ben C wrote:
>>> On 2007-09-07, Peter Cole <[email protected]> wrote:
>>> [...]
>>>> If the spoke has no bending moment (perfectly supported, perfect path),
>>>> the applied stress from spoke tension will be tensile (uniform) across
>>>> the cross section.
>>> I think I basically agree with this, though not absolutely. If the spoke
>>> is perfectly supported, but being pulled around a corner, there will
>>> surely still be a bending moment on parts of the spoke, but the distance
>>> component of that moment will never be greater than half the diameter of
>>> the spoke.
>>>
>>> Moments that small (assuming the force is in the range of normal spoke
>>> tensions) are low enough not to worry about-- they're not bringing
>>> anything anywhere near dangerously high stress levels for fatigue.
>> don't forget, virtually every fatigue failure there's ever been is
>> because of "unanticipated" factors. just because stress levels aren't
>> /thought/ to be high, *observed failures* tell us that there /is/
>> bending sufficient to cause fatigue!!!
>
> Yes, although doesn't it depend what you mean by "cause"? There is
> always some bending unless you have a straight pull spoke. If the mean
> stress in that bending cycle is low then you should get a long life
> unless you've got very bad surface defects.
>
> On the other hand if the mean stress is high (e.g. because you have a
> big bending moment), but the surface is much better, you might also get
> a short life.
>
> It's quite believable to me that wear resulting in corrosion that
> nucleated fatigue was a big factor in Clare's failed galvanized spokes,
> even if the stress cycle on them wasn't too big. But if someone's nice
> new stainless DT spokes in an Al hub fail after a few 100km then
> retained stress from the build or a big moment at the elbow look more to
> blame.

but this is not a matter of faith.

1. all traditional spokes of all qualities, of all materials, regardless
of manufacturer, are all have the elbow bent in a way that has the same
metallurgical result regarding residual stress. yet they all have
dramatically different fatigue lives that correspond with the other
variables such as material, surface finish, etc.

2. stress necessary to provide mechanical stress relief is achieved
simply from wheel pre-tension. carl fogel illustrated this well some
time ago.

3. regardless of 1. & 2., fatigue initiation is always from a region of
low/zero residual stress but high load stress.

>
> In both cases there's bending and in both cases presumably the fatigue
> starts somewhere. So the same basic mechanism, but it's reasonable to
> blame or suspect the surface quality in the first case and the high
> stresses in the second.

yes there's bending, yes there's stress, and residual stress doesn't
explain observed failures.

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

i regret that my magnification equipment doesn't allow me to take actual
pics.

 

[Jambo]

"jim beam" <[email protected]> wrote in message
news:[email protected]...
> clare at snyder.on.ca wrote:
>> All this talk about "stress relieving" spokes - I thought "stress
>> relieving" was a heat treatment. Dig out the Bernzo-Matic and heat 'em
>> up cherry red. Quench. Heat to (straw or whatever temper temperature)
>> and let air cool. NOW the spokes are stress relieved.
>
> they are, but they're also now softer and weaker - not strong enough for
> their application. that's why manufacturers don't do this.

Hey dumbass, do you really think this sounds anywhere at all credible?
"softer and weaker" indeed, just like AL alloys having young's modulus a
magnitude less than CFRP, eh?

>> But better de-bur the holes (on both sides) and polish all the tooling
>> marks out of the spokes to elininate "stress rizers" too.
>
> you could, but we're talking bikes - economics prevail. better to just
> take reasonable steps on initial formation rather than rely on
> refinishing.

What utter nonsense.
>
>> All standard aircraft building technique.
>
> indeed.

As if you know.

>>
>> Na- easier to just make sure the spokes are tensined propery and the
>> wheel is overdesigned and underengineered like a German car.
>>
>> (ducking and running for shelter)
>
> no need - the stupidity contestants will bleat themselves into a stupor
> eventually. they're harmless.

Yah, you prove that all the time.

Just stay quiet, little turd.

 

[Jambo]

"jim beam" <[email protected]> wrote in message
news:[email protected]...
> Ben C wrote:
>
> only parts of it. read this from luns tee:
> http://groups.google.com/group/rec.bicycles.tech/msg/af080b93a59cca03
>
> most notably:
> "For a more severely bent wire, the yielded layers extend deeper,
> and the residual stress pattern becomes more like:
>
> cccTCttt "
>
> so here's the problem - that [simplified but useful] depiction shows where
> the residual stress profiles would be. if residual stress were causing
> fatigue, we would observe fatigue initiating at a "T" point. instead, we
> observe it initiating at /both/ "c"'s and "t"'s.

As if you understand it - take someone else's idea and run with it, eh?
Because it's just more ammunition to get JB.

> "engineers" can argue all they want about what they think should be
> happening, but if observed facts tell a different story, it's just so much
> hot air.

But you're full of hot air - you don't even understand the mechanisms, and
yet you bleat like you're an expert! How funny!


> truth is, outside of the lab and in carefully controlled environments,
> fatigue is *always* observed to initiate at surface defects.

******** again. A simple Google of aircraft component failures proves this
is not so! Don't you ever get embarrassed by your stupidity?

> these can be from processing, corrosion, or even inclusions within the
> material. addressing each of these is observed to directly affect fatigue
> life.
> among these, electron microscopy shows inclusion content to be a
> significant fatigue initiator. removing inclusions is _proven_ to extend
> fatigue life considerably.

Wow, well cut and pasted from an introductory chapter of some publication
(wikipedia, maybe? the poor [stupid] man's reference?)

> that's why spoke manufacturers spend lots of money on expensive vacuum
> degassed materials. if cheap materials could offer superior fatigue life
> by way of simple stress relief, you'd better believe they'd be used.

AH, sometimes it's just not worth the stink of your ****...

 

[Jambo]

"jim beam" <[email protected]> wrote in message
news:[email protected]...
> Ben C wrote:
>> On 2007-09-08, jim beam <[email protected]> wrote:
>>> [email protected] wrote:
>> [...]
>>>> As I mentioned, don't fly your kite on every breeze that comes along,
>>>> especially those sent aloft by jb.
>>> as opposed to red herrings by JB?
>>
>> Please both of you calm down. I'm not about to fly any kites OR swallow
>> any herrings. You are both much better at explaining things when you
>> aren't blinded by paranoia or rage respectively.
>
> so what's the question?

Why are you such a hallucinating moron?

 

[jim beam]

Ben C wrote:
> On 2007-09-08, jim beam <[email protected]> wrote:
>> Peter Cole wrote:
>>> Ben C wrote:
>> <snip for clarity>
>>
>>>> I would have thought so, yes, unless you really overdo it.
>>> It's pretty impossible to overdo it, your hands aren't strong enough.
>> eh? translation: "it yields to cause 'stress relief' but it doesn't
>> yield if that interferes with my ability to argue."
>
> Isn't the point that if part of the spoke is close to yield, because
> it's just been bent while you were building the wheel, then you can
> bring that part up to yield with a relatively small amount more force?

but you can do that just by tensioning the spokes in the first place.
and you'll never eliminate residual stress unless you do so thermally.
that's not acceptable because it destroys the materials strength. and
it makes no practical difference since the fatigue is not initiating
from a region of high residual stress.


>
> Of course the only reason you can ever yield a spoke with your hands is
> by bending it. As you yield it some more, the configuration changes and
> the moment is reduced. So it's difficult to over-yield it.

but yield /introduces/ residual stress!!!

> It's not like
> bending a coathanger backwards and forwards.

 

[jim beam]

Peter Cole wrote:
> jim beam wrote:
>> but why am i wasting my time - you don't understand the difference
>> between plasticity and elasticity - fatigue is well beyond you.
>
>
> Don't go away mad....

i'm not. but you're apparently leaving still ignorant.

 

[Jambo]

"jim beam" <[email protected]> wrote in message
news:[email protected]...

> don't forget, virtually every fatigue failure there's ever been is because
> of "unanticipated" factors.

Just like "almost every bike uses CF forks"?

> just because stress levels aren't /thought/ to be high, *observed
> failures* tell us that there /is/ bending sufficient to cause fatigue!!!

Then in that case stress levels are INDEED high, that's the only reason to
cause fatigue, dumbass.

> see other post on profiles. since residual stress profiles are observed
> /not/ to be a factor in fatigue, further discussion is pointless - unless
> applied stresses are discussed also.

******** again. Residual stresses figure prominently in fatigue, especially
if the stress levels are high. Ever hear of shot peening?

>> I would have thought so, yes, unless you really overdo it.

Well we all know what your thoughts are worth (clue: it ain't above zilch).

 

[Jambo]

"jim beam" <[email protected]> wrote in message
news:[email protected]...
> but this is not a matter of faith.

With you, it's all a matter of ******** baffles brains.

> 1. all traditional spokes of all qualities, of all materials, regardless
> of manufacturer, are all have the elbow bent in a way that has the same
> metallurgical result regarding residual stress. yet they all have
> dramatically different fatigue lives that correspond with the other
> variables such as material, surface finish, etc.

And of course, how they're used don't figure in the equation, do they?
Dumbass.

> 2. stress necessary to provide mechanical stress relief is achieved simply
> from wheel pre-tension. carl fogel illustrated this well some time ago.

Yeah, bandy about a term picked up from someone else. What does that even
mean, do you know?

> 3. regardless of 1. & 2., fatigue initiation is always from a region of
> low/zero residual stress but high load stress.

******** again.

> yes there's bending, yes there's stress, and residual stress doesn't
> explain observed failures.
>
> http://www.flickr.com/photos/38636024@N00/1346747861/
>
> i regret that my magnification equipment doesn't allow me to take actual
> pics.

Because you'll be open to scrutiny, and your ******** will show!

 

[jim beam]

Jambo wrote:
> "jim beam" <[email protected]> wrote in message
> news:[email protected]...
>> Ben C wrote:
>>> On 2007-09-08, jim beam <[email protected]> wrote:
>>>> [email protected] wrote:
>>> [...]
>>>>> As I mentioned, don't fly your kite on every breeze that comes along,
>>>>> especially those sent aloft by jb.
>>>> as opposed to red herrings by JB?
>>> Please both of you calm down. I'm not about to fly any kites OR swallow
>>> any herrings. You are both much better at explaining things when you
>>> aren't blinded by paranoia or rage respectively.
>> so what's the question?
>
> Why are you such a hallucinating moron?
>
>

are you missing your meds?

 

[Ben C]

On 2007-09-08, jim beam <[email protected]> wrote:
> Ben C wrote:
>> On 2007-09-08, jim beam <[email protected]> wrote:
>>> Ben C wrote:
>>>> On 2007-09-07, Peter Cole <[email protected]> wrote:
>>>> [...]
>>>>> If the spoke has no bending moment (perfectly supported, perfect path),
>>>>> the applied stress from spoke tension will be tensile (uniform) across
>>>>> the cross section.
>>>> I think I basically agree with this, though not absolutely. If the spoke
>>>> is perfectly supported, but being pulled around a corner, there will
>>>> surely still be a bending moment on parts of the spoke, but the distance
>>>> component of that moment will never be greater than half the diameter of
>>>> the spoke.
>>>>
>>>> Moments that small (assuming the force is in the range of normal spoke
>>>> tensions) are low enough not to worry about-- they're not bringing
>>>> anything anywhere near dangerously high stress levels for fatigue.
>>> don't forget, virtually every fatigue failure there's ever been is
>>> because of "unanticipated" factors. just because stress levels aren't
>>> /thought/ to be high, *observed failures* tell us that there /is/
>>> bending sufficient to cause fatigue!!!
>>
>> Yes, although doesn't it depend what you mean by "cause"? There is
>> always some bending unless you have a straight pull spoke. If the mean
>> stress in that bending cycle is low then you should get a long life
>> unless you've got very bad surface defects.
>>
>> On the other hand if the mean stress is high (e.g. because you have a
>> big bending moment), but the surface is much better, you might also get
>> a short life.
>>
>> It's quite believable to me that wear resulting in corrosion that
>> nucleated fatigue was a big factor in Clare's failed galvanized spokes,
>> even if the stress cycle on them wasn't too big. But if someone's nice
>> new stainless DT spokes in an Al hub fail after a few 100km then
>> retained stress from the build or a big moment at the elbow look more to
>> blame.
>
> but this is not a matter of faith.
>
> 1. all traditional spokes of all qualities, of all materials, regardless
> of manufacturer, are all have the elbow bent in a way that has the same
> metallurgical result regarding residual stress. yet they all have
> dramatically different fatigue lives that correspond with the other
> variables such as material, surface finish, etc.

Good point. I was careful though to say "retained stress from the
build", not "residual stress" [from manufacture].

The latter I have mostly put in the red herring bucket so far but keep
an open mind as I am not an expert on these things.

Retained stress from the build, which really I would lump together with
poor spoke line (i.e. bending moment at the elbow) is what I suspect may
be a significant factor in some failures where good quality spokes are
used.

If there is high stress in the elbow after the build it follows that
there's enough moment present for spoke tension to maintain that stress.
I'd be inclined to say that the moment is the real problem: it will
allow a high-stress bending cycle in use, even if you stress-relieve, if
stress relief doesn't also have the effect of also reducing that moment.

But I think stress-relief probably _does_ reduce the moment by bending
the elbow a bit more and by conforming it to the hub (_pace_ Peter
Cole's and Jobst's well-reasoned arguments why hub conformance is not
likely to happen much after tensioning).

 

[jim beam]

Jambo wrote:
> "jim beam" <[email protected]> wrote in message
> news:[email protected]...
>> clare at snyder.on.ca wrote:
>>> All this talk about "stress relieving" spokes - I thought "stress
>>> relieving" was a heat treatment. Dig out the Bernzo-Matic and heat 'em
>>> up cherry red. Quench. Heat to (straw or whatever temper temperature)
>>> and let air cool. NOW the spokes are stress relieved.
>> they are, but they're also now softer and weaker - not strong enough for
>> their application. that's why manufacturers don't do this.
>
> Hey dumbass, do you really think this sounds anywhere at all credible?
> "softer and weaker" indeed, just like AL alloys having young's modulus a
> magnitude less than CFRP, eh?

er, look into cold work some time and learn what effect it has on
hardness and strength. you /do/ know how to define "hardness" and
"strength" don't you mr. modulus?


>
>>> But better de-bur the holes (on both sides) and polish all the tooling
>>> marks out of the spokes to elininate "stress rizers" too.
>> you could, but we're talking bikes - economics prevail. better to just
>> take reasonable steps on initial formation rather than rely on
>> refinishing.
>
> What utter nonsense.
>>> All standard aircraft building technique.
>> indeed.
>
> As if you know.
>
>>> Na- easier to just make sure the spokes are tensined propery and the
>>> wheel is overdesigned and underengineered like a German car.
>>>
>>> (ducking and running for shelter)
>> no need - the stupidity contestants will bleat themselves into a stupor
>> eventually. they're harmless.
>
> Yah, you prove that all the time.
>
> Just stay quiet, little turd.

learn to use a killfile!

 

[Ben C]

On 2007-09-08, jim beam <[email protected]> wrote:
> Ben C wrote:
[...]
>> Of course the only reason you can ever yield a spoke with your hands is
>> by bending it. As you yield it some more, the configuration changes and
>> the moment is reduced. So it's difficult to over-yield it.
>
> but yield /introduces/ residual stress!!!

If you (a) bend a wire round a bolt the way Carl did for his heating
experiments, and then, having bent it, you (b) give it a further good
hard pull on both ends, and then relax that to (c) just enough pull to
hold the wire in place, won't you end up with fewer regions of high
stress than if you did (a) and (c) without (b)?