removing broken spoke nipples

  • Thread starter Bellsouth Ijit 2.0
  • Start date



ahhh now i unnnerstan ping!! coool. i'll try the musical note
approach.



The following is from sheldonbrown parsec 1. a photo of brown
mangling spokes with a crowbar is missing here but is viewable at his
bicycle website

More informative dialogue comes by searching groups through the
sheldonbrown.com search boxes with the key words eg, spoke windup,
stress relief, sissy method, - often with the wheel devil hizelf at
the helm:

Spoke Torsion

As the wheel begins to come into tension, you start to have to deal
with spoke torsion. When you turn your spoke wrench, the first thing
that happens is that the spoke will twist a bit from the friction of
the threads. Once the nipple has turned far enough, the twist in the
spoke will give enough resistance that the threads will start to move,
but the spoke will remain twisted. What a good wheelbuilder can do
that a robot machine can't do is feel this twist. If you "finish" you
wheel up, and it is perfectly true in your stand, but the spokes are
twisted, the wheel will not stay true on the road. The twist in the
spokes will eventually work itself out, and the wheel will go out of
true.
This problem can be prevented by sensitive use of your spoke wrench.
What you need to do is overshoot and backlash. In other words, suppose
you want to tighten a particular spoke 1/4 turn. You don't just turn
the wrench 1/4 turn, you turn it a little farther, then back it up
that same little bit. The nipple winds up being 1/4 turn tighter, but
the backing up releases the twist in the spoke.
This is much easier to do on straight-gauge spokes, because they are
stiffer torsionally, and it is easier to feel the twist than it is
with butted spokes. This is one of the reasons I like "aerodynamic"
spokes so much; not so much for the aerodynamics, as for the fact that
you can tell visually if they are twisted.

Seating and Stress Relieving the Spokes

Before a wheel is ready for the road it must be stress relieved,
because the bend in the spoke has to accommodate itself to the shape
of the hub flange and vice versa, and a similar process may go on
where the nipple sits in the rim. Some wheelbuilders do this by
flexing the whole wheel, others by grabbing the spokes in groups of 4
and squeezing them together. My preferred technique is to use a lever
to bend the spokes around each other where they cross. My favorite
lever for this is an old left crank:
This particular technique has the added advantage of bending the
spokes neatly around each other at the crossing, so they run straight
from the crossing in both directions. As you go around the wheel this
way you will probably hear creaks and pinging sounds as the parts come
into more intimate terms with each other.
After you do this, you will probably have to do some touch-up truing,
then repeat the stressing process until it stops making noise and the
wheel stops going out of true.
Jobst Brandt , author of the excellent book The Bicycle Wheel points
out a less obvious benefit of this stressing of the spokes:
"...After cold forming, steel always springs back a certain amount
(spokes are entirely cold formed from wire). Spring-back occurs
because part of the material exceeded its elastic limit and part did
not. The disparate parts fight each other in tension and compression,
so that when the spoke is tensioned, it adds to the tensile stress
that can be, and often is, at yield.
"...When spokes are bent into place, they yield locally and addition
of tension guarantees that these places remain at yield. Because
metal, at or near the yield stress has a short fatigue life, these
stresses must be relieved to make spokes durable.
"...These peak stresses can be relieved by momentarily increasing
spoke tension (and stress), so that the high stress points of the
spoke yield and plastically deform with a permanent set. When the
stress relief force is relaxed these areas cannot spring back having,
in effect, lost their memory, and drop to the average stress of the
spoke."
If you have done this, you will wind up with a wheel that is true and
round, and will stay that way better than most machine made wheels. In
addition, you will have learned a lot about truing wheels, and you
will feel more like a real professional mechanic
 
J

jim beam

Guest
[email protected] wrote:
> ahhh now i unnnerstan ping!! coool. i'll try the musical note
> approach.
>
>
>
> The following is from sheldonbrown parsec 1. a photo of brown
> mangling spokes with a crowbar is missing here but is viewable at his
> bicycle website
>
> More informative dialogue comes by searching groups through the
> sheldonbrown.com search boxes with the key words eg, spoke windup,
> stress relief, sissy method, - often with the wheel devil hizelf at
> the helm:
>


sheldon's site is excellent in many respects, but repeating jobstian
mistakes is not one of them. i guess though that they're jobst's words,
not his.

<snip>
>
> Jobst Brandt , author of the excellent book The Bicycle Wheel points
> out a less obvious benefit of this stressing of the spokes:
> "...After cold forming, steel always springs back a certain amount
> (spokes are entirely cold formed from wire). Spring-back occurs
> because part of the material exceeded its elastic limit and part did
> not. The disparate parts fight each other in tension and compression,
> so that when the spoke is tensioned, it adds to the tensile stress
> that can be, and often is, at yield.


that is a fundamental misconception and utterly incorrect. springback
is the result of elasticity - springback is not evidence of residual stress.

> "...When spokes are bent into place, they yield locally and addition
> of tension guarantees that these places remain at yield. Because
> metal, at or near the yield stress has a short fatigue life, these
> stresses must be relieved to make spokes durable.


more confused misconception: metal at its yield stress yields. metal
doesn't need to be anywhere near it's yield stress to fatigue.

> "...These peak stresses can be relieved by momentarily increasing
> spoke tension (and stress), so that the high stress points of the
> spoke yield and plastically deform with a permanent set. When the
> stress relief force is relaxed these areas cannot spring back having,
> in effect, lost their memory, and drop to the average stress of the
> spoke."


yet more confused misconception. "cannot spring back" is fundamentally
incorrect - it implied that metals yield to zero - they don't. and
there is no "memory" in stainless steels. elasticity is not memory.

bottom line, jobst attributes spoke fatigue to something he doesn't
adequately understand, residual stress. presumably because he doesn't
understand the real situation, that a traditional spokes shape ensures
that it constantly bends as it goes through its load cycles. given that
this configuration is going to be used for at least a while longer, the
next most important factors to understand in fatigue are configuration
refinement [namely making sure that there's a good fit and the shank is
not too long, etc.], surface finish, material quality, resistance to
corrosion, etc. and if all other factors have been eliminated, then we
can get to residual stress. but even then, given that spokes are
created today in exactly the same way as they were years ago yet are now
highly fatigue resistant, what's changed? answer: it's the material.
to state this another way, if the method hasn't changed, the residual
stress hasn't changed. if the residual stress hasn't changed, but
spokes last longer and happen to be made of better material, it has to
be the material that affects fatigue, not residual stress!
 
M

Michael Press

Guest
In article
<[email protected]>,
Tim McNamara <[email protected]> wrote:

> Huh? This is starting to sound like the delay tactics employed to fend
> off taking action to reduce climate change.


Climate change happens. You cannot change climate
change. There is no normal for the climate. It is
always in a chaotic regime. A bunch of positive
feedback mechanisms driven by a heat source that is
totally unpredictable. Man-made climate change is
hubris. A flea doing back-stroke down the river crying
"Raise the drawbridge."
 
"yet more confused misconception. "cannot spring back" is
fundamentally
incorrect - it implied that metals yield to zero - they don't."

and an experiment to try with a steel bean can top and two vice grips
bending and rebending a fold in the can top.

we knew about climate change in the '30's: a spinoff of asteroids kill
dinosaurs. bicycle to the superduper
 
B

Bill Sornson

Guest
Michael Press wrote:
> In article
> <[email protected]>,
> Tim McNamara <[email protected]> wrote:


>> Huh? This is starting to sound like the delay tactics employed to
>> fend off taking action to reduce climate change.


> Climate change happens. You cannot change climate
> change. There is no normal for the climate. It is
> always in a chaotic regime. A bunch of positive
> feedback mechanisms driven by a heat source that is
> totally unpredictable. Man-made climate change is
> hubris. A flea doing back-stroke down the river crying
> "Raise the drawbridge."


Bravo, Mr. Press.

If man is causing GW today, then why did previous ice ages end?

" " " " " " , then why was it warmer than now
during the Middle Ages? (Not to mention 1998 -- warmest year on record.)

Why are the ice caps shrinking...ON MARS?

Bill "Inconvenient Questions" S.
 
M

Michael Press

Guest
In article <[email protected]>,
"Bill Sornson" <[email protected]> wrote:

> Michael Press wrote:
> > In article
> > <[email protected]>,
> > Tim McNamara <[email protected]> wrote:

>
> >> Huh? This is starting to sound like the delay tactics employed to
> >> fend off taking action to reduce climate change.

>
> > Climate change happens. You cannot change climate
> > change. There is no normal for the climate. It is
> > always in a chaotic regime. A bunch of positive
> > feedback mechanisms driven by a heat source that is
> > totally unpredictable. Man-made climate change is
> > hubris. A flea doing back-stroke down the river crying
> > "Raise the drawbridge."

>
> Bravo, Mr. Press.
>
> If man is causing GW today, then why did previous ice ages end?


Somebody left the refrigerator door open.

> " " " " " " , then why was it warmer than now
> during the Middle Ages? (Not to mention 1998 -- warmest year on record.)


Actually, it is cooler now than during the middle ages.

> Why are the ice caps shrinking...ON MARS?


Ahh, sublimation and migration to interplanetary space?
 
T

Tim McNamara

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

> Tim McNamara wrote:
> > In article <[email protected]>,
> > jim beam <[email protected]> wrote:
> >
> >> Tim McNamara wrote:
> >>> In article <[email protected]>,
> >>> jim beam <[email protected]> wrote:
> >>>
> >>>> Tim McNamara wrote:
> >>>>> In article <[email protected]>,
> >>>>> jim beam <[email protected]> wrote:
> >>>>>
> >>>>>> Tim McNamara wrote:
> >>>>>>> In article <[email protected]>,
> >>>>>>> jim beam <[email protected]> wrote:
> >>>>>>>
> >>>>>>>> Ben C wrote:
> >>>>>>>>> On 2007-03-10, [email protected] <[email protected]>
> >>>>>>>>> wrote:
> >>>>>>>>>>> You mentioned "Finish Line" before-- that's the stuff I
> >>>>>>>>>>> put on my chain. I thought it was basically oil. But
> >>>>>>>>>>> let's not get into a flame war on the difference between
> >>>>>>>>>>> oil, wax and grease
> >>>>>>>>>>> :)
> >>>>>>>>>> http://www.finishlineusa.com/products/teflon-plus-lube.htm
> >>>>>>>>>>> Now that is interesting.
> >>>>>>>>>>>> " The change occurs at any high tensile stress location
> >>>>>>>>>>>> when the spoke is over-tensioned (over its static
> >>>>>>>>>>>> tension)." Q. Is the location manifest in a physical
> >>>>>>>>>>>> form? Does the "yield" maximize as an average when the
> >>>>>>>>>>>> spoke is both straight or near its unstrung state - yet
> >>>>>>>>>>>> strung?
> >>>>>>>>>>> Wait for JB to answer, but I think the yield here would
> >>>>>>>>>>> generally be intended to be a small amount on the outside
> >>>>>>>>>>> of the bend at the elbow.
> >>>>>>>>>> on the outside! heheheheh wait! lube the inside, progress!
> >>>>>>>>>> stress is on the inside, no?
> >>>>>>>>> It's on both sides, but it's compressive on the inside and
> >>>>>>>>> tensile on the outside. It's the tensile stress on the
> >>>>>>>>> outside that's the biggest risk for shortening the fatigue
> >>>>>>>>> life of the spoke.
> >>>>>>>> i've got broken spokes that have fatigue initiating from the
> >>>>>>>> inside as well as the outside.
> >>>>>>>>
> >>>>>>>> my thoughts are that if it's broken on the outside, the
> >>>>>>>> spoke flange was insufficiently indented by over-stress, so
> >>>>>>>> the net exit angle created a tensile stress component on the
> >>>>>>>> outside of the spoke.
> >>>>>>> Or you just failed to correct the spoke line properly. In
> >>>>>>> short, user error.
> >>>>>> you don't understand geometry or you didn't read multiple
> >>>>>> posts on this subject. "correcting the spoke line" is
> >>>>>> unnecessary if the hub hole is adequately indented.
> >>>>> I participated in that thread, jim, in which it was
> >>>>> demonstrated that hub flanges don't deform enough and that
> >>>>> manually correcting the spoke like is necessary.
> >>>> eh? you really don't pay attention do you!!! or you just see
> >>>> what you want to see. wow.
> >>> I see what's plainly in front of me in reality, rather that what
> >>> you speculate reality ought to be.
> >> so you see what's in front of you? what is steel then timmy?
> >> come on. describe it to me. give me your reality.

> >
> > LOL. Nice try.

>
> no, i mean it. you say "I see what's plainly in front of me in
> reality, rather that what you speculate reality ought to be." now,
> go ahead and stand by your statement. what is your reality of steel?
> you use it every day. it's integral to your life. but what is it
> timmy? share the reality that's "plainly in front of you".


It's a nice strong metal. LOL! You do know a red herring when you cast
one, don't you? Your question is a silly red herring and deserves no
better response.

Ah jimmy beamish old boy, you reduce yourself further with every post as
you desperately try to find somewhere to plunge the dagger home. You
try it with Jobst, you try it with Annan, you try it with Krygowski, you
try it with me. You really ought not to provoke battles of wit when you
are so poorly armed.

> >>>>> You then changed your tune and claimed that
> >>>>> tensioning the spokes would correct the spoke line adequately,
> >>>>> which was also shown to be incorrect. IIRC you called
> >>>>> Krygowski an "idiot" at that point and another thread was
> >>>>> pretty much dead. Maybe you should try building a few dozen
> >>>>> wheels instead of speculating out of your ****.
> >>>> timmy, you're still not a candidate for the krygowski award for
> >>>> contributions to technology, but you're getting pretty freakin'
> >>>> close if you can't read most things and misinterpret the little
> >>>> that you do.
> >>> There you go again, beamish boy. So intent on being right, even
> >>> when you're clueless.
> >> sure i am. but at least i can do math.

> >
> > Yet your grasp of logic is so poor.

>
> sure it is. i can't reason **** for a living.


That's about the size of it on r.b.t. I don't know what you do for a
living now that you are not a metallurgist. Hopefully you're better at
that.
 
T

Tim McNamara

Guest
In article <[email protected]>,
Ben C <[email protected]> wrote:

I just noticed ^^^^^^^^^. Nice reference.

> I do think it's advisable to get that pinging out before you ride off
> round the block though. And if you lube the nipples and overturn and
> turn back when tensioning, you don't get much pinging anyway.


Quite right, it's best if your spokes aren't unwinding as you ride down
the street. If there is a lot of spoke windup your wheels can end up
out of true (a grain of truth in one of jim's invectives). Building
wheels properly (lubricating the threads and contact point between the
nipple and the rim) with good spoke wrench technique will prevent spoke
windup and hence prevents the pinging.
 
T

Tim McNamara

Guest
In article <[email protected]>,
Michael Press <[email protected]> wrote:

> In article <[email protected]>,
> Tim McNamara <[email protected]> wrote:
>
> > Huh? This is starting to sound like the delay tactics employed to
> > fend off taking action to reduce climate change.

>
> Climate change happens. You cannot change climate change. There is no
> normal for the climate. It is always in a chaotic regime. A bunch of
> positive feedback mechanisms driven by a heat source that is totally
> unpredictable. Man-made climate change is hubris. A flea doing
> back-stroke down the river crying "Raise the drawbridge."


Then civilization is doomed. Have a nice day.
 
T

Tim McNamara

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

> Tim McNamara wrote:
> > In article <[email protected]>,
> > Ben C <[email protected]> wrote:
> >
> >> On 2007-03-11, [email protected] <[email protected]> wrote:
> >>> its like a dog chasing his tail!!! art arcane incompre wheel
> >>> building but in the plane of the wheel, if you see what I mean.
> >>>
> >>> why all the hubbub about stress relief and spokeline if all ya
> >>> gotta do is ride around the block?
> >> In theory riding around the block won't stress relieve. For that
> >> you need to overload and then relax. Riding around the block is
> >> just normal load, not overload. I think Tim was saying it will
> >> however seat the elbows in the hub.

> >
> > No, I was saying that the "Mavic method" espoused by jim beam will
> > cause spoke windup to be released and little if anything else. It
> > won't accomplish stress relief nor is it likely to accomplish much
> > by way of spoke seating.

>
> don't let your ignorance or inability to learn get in the way of your
> mouth will you timmy. it's engineering 101 - yielding. if the spoke
> hole yields with a certain load, increasing it with over-tension is
> going to yield it even more! but you're the guy with the math
> problem, so while i don't expect /you/ to grasp that concept, don't
> try to propagate your ignorance.


LOL. What's funny about that is your insistence that it doesn't happen
with spokes.

> >> Those of us who are not true believers in stress relief are
> >> inclined to think the benefits of the Mavic method include seating
> >> and taking out windup, and that these may be more significant than
> >> stress relieving. Tim I think was saying that if we did live in
> >> that possible world, the Mavic method would be futile because
> >> spokes seat when you ride round the block anyway.

> >
> > Riding around the block doesn't increase spoke tension, so it won't
> > accomplish spoke seating.

> <snip remaining ****>
>
> eh? lateral load will increase spoke tension.


One one side, yes; already aware of that, jim. The "Mavic method" is
useful for this if you have a hydraulic press and a full support for the
rim. Indeed, it'd be much faster than squeezing four spokes at a time.
Some wheel builders (Rolf, Bontrager) use that method to make it easier
to achieve high spoke tensions.
 
T

Tim McNamara

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

> bottom line, jobst attributes spoke fatigue to something he doesn't
> adequately understand, residual stress. presumably because he
> doesn't understand the real situation, that a traditional spokes
> shape ensures that it constantly bends as it goes through its load
> cycles. given that this configuration is going to be used for at
> least a while longer, the next most important factors to understand
> in fatigue are configuration refinement [namely making sure that
> there's a good fit and the shank is not too long, etc.], surface
> finish, material quality, resistance to corrosion, etc. and if all
> other factors have been eliminated, then we can get to residual
> stress. but even then, given that spokes are created today in
> exactly the same way as they were years ago yet are now highly
> fatigue resistant, what's changed? answer: it's the material. to
> state this another way, if the method hasn't changed, the residual
> stress hasn't changed. if the residual stress hasn't changed, but
> spokes last longer and happen to be made of better material, it has
> to be the material that affects fatigue, not residual stress!


That was actually your best effort yet.
 

> Then civilization is doomed. Have a nice day.


listen, you can flex the can, relate to yield, worry about global
warming, bicycle to the superduper, and watch out for the rats at taco
bell
all at the same time!!
CERAMICS!
 
J

jim beam

Guest
Tim McNamara wrote:
> In article <[email protected]>,
> jim beam <[email protected]> wrote:
>
>> Tim McNamara wrote:
>>> In article <[email protected]>,
>>> Ben C <[email protected]> wrote:
>>>
>>>> On 2007-03-11, [email protected] <[email protected]> wrote:
>>>>> its like a dog chasing his tail!!! art arcane incompre wheel
>>>>> building but in the plane of the wheel, if you see what I mean.
>>>>>
>>>>> why all the hubbub about stress relief and spokeline if all ya
>>>>> gotta do is ride around the block?
>>>> In theory riding around the block won't stress relieve. For that
>>>> you need to overload and then relax. Riding around the block is
>>>> just normal load, not overload. I think Tim was saying it will
>>>> however seat the elbows in the hub.
>>> No, I was saying that the "Mavic method" espoused by jim beam will
>>> cause spoke windup to be released and little if anything else. It
>>> won't accomplish stress relief nor is it likely to accomplish much
>>> by way of spoke seating.

>> don't let your ignorance or inability to learn get in the way of your
>> mouth will you timmy. it's engineering 101 - yielding. if the spoke
>> hole yields with a certain load, increasing it with over-tension is
>> going to yield it even more! but you're the guy with the math
>> problem, so while i don't expect /you/ to grasp that concept, don't
>> try to propagate your ignorance.

>
> LOL. What's funny about that is your insistence that it doesn't happen
> with spokes.
>
>>>> Those of us who are not true believers in stress relief are
>>>> inclined to think the benefits of the Mavic method include seating
>>>> and taking out windup, and that these may be more significant than
>>>> stress relieving. Tim I think was saying that if we did live in
>>>> that possible world, the Mavic method would be futile because
>>>> spokes seat when you ride round the block anyway.
>>> Riding around the block doesn't increase spoke tension, so it won't
>>> accomplish spoke seating.

>> <snip remaining ****>
>>
>> eh? lateral load will increase spoke tension.

>
> One one side, yes; already aware of that, jim.


who cares if it's only on one side??? an increase is an increase.
that'll lead to further spoke seating unless the wheel has been
overstressed. further seating means slack spokes and a wheel out of true.

> The "Mavic method" is and that's no contribution.


> useful for this if you have a hydraulic press and a full support for the
> rim.


eh? don't you feel even a teensy little bit ashamed for such a stupid
extrapolation? did you ever read the pdf from the mavic web site? or
fogel's re-post of the text?

> Indeed, it'd be much faster than squeezing four spokes at a time.
> Some wheel builders (Rolf, Bontrager) use that method to make it easier
> to achieve high spoke tensions.


actually, trying to do all the spokes at once in this way assumes all
spokes of equal tension, and that spoke holes will yield equally - which
is overly simplistic. "mavic method" makes no such assumptions and
ensures all are treated equally, even slack spokes.
 
A

A Muzi

Guest
>> In article <[email protected]>,
>> Tim McNamara <[email protected]> wrote:
>>> Huh? This is starting to sound like the delay tactics employed to
>>> fend off taking action to reduce climate change.


> Michael Press <[email protected]> wrote:
>> Climate change happens. You cannot change climate change. There is no
>> normal for the climate. It is always in a chaotic regime. A bunch of
>> positive feedback mechanisms driven by a heat source that is totally
>> unpredictable. Man-made climate change is hubris. A flea doing
>> back-stroke down the river crying "Raise the drawbridge."



Tim McNamara wrote:
> Then civilization is doomed. Have a nice day.


Huh? We survived the warm Roman era, the cooler Medieval, the warm
settling of Greenland and their later cold demise, the Year of No Summer
and every other normal variant so why are we doomed now?

p.s. Martian Warming just has to be caused by the Rovers - "Technology
Is Bad" and all that . . .
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971
 
A

Andrew Lee

Guest
jim beam wrote:
>> "...These peak stresses can be relieved by momentarily increasing
>> spoke tension (and stress), so that the high stress points of the
>> spoke yield and plastically deform with a permanent set. When the
>> stress relief force is relaxed these areas cannot spring back having,
>> in effect, lost their memory, and drop to the average stress of the
>> spoke."

>
> yet more confused misconception. "cannot spring back" is fundamentally
> incorrect - it implied that metals yield to zero - they don't. and there
> is no "memory" in stainless steels. elasticity is not memory.


I pointed the same thing out a few weeks ago, but again, you have really
poor reading comprehension and logic, and you can't even interpret the most
basic stress-strain graphs. Maybe that's why are you're an EX-metallurgist?
Look at your own drawing in photo number 3 here:

http://www.flickr.com/photos/[email protected]/327752060/

See how that yielded metal goes back down along the Hooke's Law line? Where
does it end up? It doesn't end up at the origin. It's in a parallel track
because there is plastic deformation. It should be blatantly obvious to a
materials person that that separation cannot be closed by relaxing the
stress relief force. Thus, Jobst can accurately say that those high stress
areas cannot spring back. In the context of that passage, it is clear that
"spring back" means that the material cannot reach the initial position, not
that the material does not obey Hooke's Law. I'll bet even non-engineers
and materials people can interpret what Jobst wrote correctly. What does
that say about your reading comprehension and understanding of materials?
Or is it a willful misreading?

Here's my drawing:

http://img215.imageshack.us/img215/1736/img3480wr8.jpg

Do you agree that stress within a spoke is not uniform? In my drawing,
Point 1 represents the position in the graph of the material at highest
stress within a spoke, such as the outside of the spoke elbow. Area 4 is
the average stress of the other regions of the spoke that typically don't
break from fatigue. Point 1 is more likely to break from fatigue because it
is at a higher percentage of yield stress than Area 4. If the material at
Point 1 can be made to relax to a lower stress level, the service life of
the spoke will improve. It does not matter if 304 stainless has an actual
endurance limit or not. (Modern stainless spokes have demonstrated
capability to be considered lifetime spokes, if not infinite life spokes).

During stress relieving, Point 1 is brought to yield. When the spoke is
relaxed it passes through Point 2, a position of equal stress to Point 1's
initial stress. It doesn't stop there because it has yielded and the
dimension of the yielded region is larger in the direction of the stress.
The material that was initially at Point 1 on the stress-strain graph
relaxes to approximately Point 3 after stress relief because it can be
assumed that the bulk of the spoke surrounding the high stress region did
not yield. During stress relieving, Area 4 also travels up the Hooke's law
line, "following" Point 1, but since it follows at a lower stress level, it
doesn't reach yield. Upon relaxation of the stress relief force, Area 4
returns down the initial Hooke's Law line back to it's initial position (or
close enough for you nitpickers) because the stress relief force only yields
a small portion of cross section of the spoke - the spoke does not
measureably lengthen from the stress relief procedure.

The horizontal distance between Point 1 and Point 2 (marked in red in my
drawing) is what can't be closed by the relaxing the stress relief force.
After stress relief, you can reset the origin of yielded return-track
Hooke's Law back to zero. Thus, formerly high stress region will be mapped
out somewhere near or within Area 4. Maybe at the top of Area 4, or even a
bit higher, but in any case, the stress in the region will be below what it
was at Point 1 before stress relief.

By the way, I have also have a materials background (a B.S. in Materials
Engineering from way back, though I don't work in the field - but neither do
you). You occasionally provide some good information regarding materials,
but more often than not, they are irreverant to the topic, diversions
really. You get many basic engineering concepts wrong and are so delusional
that you call others out when you are the one who usually has it wrong. And
you pick nicks (Jobst helps by making absolutist statements) and miss the
main points. (Such as brinelling vs. fretting in headsets... so what if you
can brinell a lousy headset? They generally fail by frettting.)
 
A

Andrew Lee

Guest
Andrew Lee wrote:
> main points. (Such as brinelling vs. fretting in headsets... so what if
> you can brinell a lousy headset? They generally fail by frettting.)


Since you are a nit picker, I should say that I don't know how headsets
generally fail. May water intrustion? But indexed headsets are generally a
result of fretting...
 
B

Ben C

Guest
On 2007-03-12, Andrew Lee <> wrote:
[...]
> Here's my drawing:
>
> http://img215.imageshack.us/img215/1736/img3480wr8.jpg

[...]
> During stress relieving, Point 1 is brought to yield. When the spoke is
> relaxed it passes through Point 2, a position of equal stress to Point 1's
> initial stress. It doesn't stop there because it has yielded and the
> dimension of the yielded region is larger in the direction of the stress.


Is this something like "Poisson's ratio"-- basically when you pull
things they stretch out long and thin?

So to clarify, could it be said that the reason Point 1 ends up
somewhere around Point 3 is because that part of the spoke has got a
little bit longer, so ends up held under a little bit less tension?
That's how it finds its way to a lower point on the stress axis.

But in that case I might expect it to find it somewhere on the line
between 3 and 2-- under a bit less stress, because it's strained a bit,
so I think I haven't understood.

> The material that was initially at Point 1 on the stress-strain graph
> relaxes to approximately Point 3 after stress relief because it can be
> assumed that the bulk of the spoke surrounding the high stress region did
> not yield.


It's this part that I'm not following.
 

dabac

Well-Known Member
Sep 16, 2003
2,298
288
83
52
Michael Press said:
In article <[email protected]>,
"Bill Sornson" <[email protected]> wrote:

> Michael Press wrote:
> > In article
> > <[email protected]>,
> > Tim McNamara <[email protected]> wrote:

>
> >> Huh? This is starting to sound like the delay tactics employed to
> >> fend off taking action to reduce climate change.

>
> > Climate change happens. You cannot change climate
> > change. There is no normal for the climate. It is
> > always in a chaotic regime. A bunch of positive
> > feedback mechanisms driven by a heat source that is
> > totally unpredictable. Man-made climate change is
> > hubris. A flea doing back-stroke down the river crying
> > "Raise the drawbridge."

>
> Bravo, Mr. Press.
>
> If man is causing GW today, then why did previous ice ages end?


Somebody left the refrigerator door open.

Nah, they began when someone left the fridge door open, and ended when someone else closed it. Makes perfect sense.
 
J

jim beam

Guest
Andrew Lee wrote:
> jim beam wrote:
>>> "...These peak stresses can be relieved by momentarily increasing
>>> spoke tension (and stress), so that the high stress points of the
>>> spoke yield and plastically deform with a permanent set. When the
>>> stress relief force is relaxed these areas cannot spring back having,
>>> in effect, lost their memory, and drop to the average stress of the
>>> spoke."

>> yet more confused misconception. "cannot spring back" is fundamentally
>> incorrect - it implied that metals yield to zero - they don't. and there
>> is no "memory" in stainless steels. elasticity is not memory.

>
> I pointed the same thing out a few weeks ago, but again, you have really
> poor reading comprehension and logic, and you can't even interpret the most
> basic stress-strain graphs. Maybe that's why are you're an EX-metallurgist?
> Look at your own drawing in photo number 3 here:
>
> http://www.flickr.com/photos/[email protected]/327752060/
>
> See how that yielded metal goes back down along the Hooke's Law line? Where
> does it end up? It doesn't end up at the origin. It's in a parallel track
> because there is plastic deformation. It should be blatantly obvious to a
> materials person that that separation cannot be closed by relaxing the
> stress relief force. Thus, Jobst can accurately say that those high stress
> areas cannot spring back. In the context of that passage, it is clear that
> "spring back" means that the material cannot reach the initial position, not
> that the material does not obey Hooke's Law. I'll bet even non-engineers
> and materials people can interpret what Jobst wrote correctly. What does
> that say about your reading comprehension and understanding of materials?
> Or is it a willful misreading?
>
> Here's my drawing:
>
> http://img215.imageshack.us/img215/1736/img3480wr8.jpg


the features of that graph are identical to mine, right up to point 3
where you're not releasing stress completely.

regarding your questions, jobst cites springback as being evidence of
residual stress. that is incorrect. if he wants to cite anything, he
should cite deformation. springback is simply elasticity.

>
> Do you agree that stress within a spoke is not uniform? In my drawing,
> Point 1 represents the position in the graph of the material at highest
> stress within a spoke, such as the outside of the spoke elbow. Area 4 is
> the average stress of the other regions of the spoke that typically don't
> break from fatigue. Point 1 is more likely to break from fatigue because it
> is at a higher percentage of yield stress than Area 4. If the material at
> Point 1 can be made to relax to a lower stress level, the service life of
> the spoke will improve. It does not matter if 304 stainless has an actual
> endurance limit or not. (Modern stainless spokes have demonstrated
> capability to be considered lifetime spokes, if not infinite life spokes).


yes, stress is un-uniform. yes, something laded to a higher portion of
yield will fatigue sooner.

>
> During stress relieving, Point 1 is brought to yield. When the spoke is
> relaxed it passes through Point 2, a position of equal stress to Point 1's
> initial stress. It doesn't stop there because it has yielded and the
> dimension of the yielded region is larger in the direction of the stress.


no, points 1 & 2 are equal stress.

> The material that was initially at Point 1 on the stress-strain graph
> relaxes to approximately Point 3 after stress relief because it can be
> assumed that the bulk of the spoke surrounding the high stress region did
> not yield. During stress relieving, Area 4 also travels up the Hooke's law
> line, "following" Point 1, but since it follows at a lower stress level, it
> doesn't reach yield. Upon relaxation of the stress relief force, Area 4
> returns down the initial Hooke's Law line back to it's initial position (or
> close enough for you nitpickers) because the stress relief force only yields
> a small portion of cross section of the spoke - the spoke does not
> measureably lengthen from the stress relief procedure.


ok, let's be clear about this. for mechanical stress relief to work,
there are conditions that need to be met, i.e. it's done right after
initial forming, not after aging. in addition, it results from
yielding. if there's no yielding, there's no stress relief. yielding
requires permanent deformation which is therefore measurable.

>
> The horizontal distance between Point 1 and Point 2 (marked in red in my
> drawing) is what can't be closed by the relaxing the stress relief force.


indeed. see point above.

> After stress relief, you can reset the origin of yielded return-track
> Hooke's Law back to zero.


you can set stress back to zero, but not strain - it's yielded.

> Thus, formerly high stress region will be mapped
> out somewhere near or within Area 4.


area 3, not 4. it's yielded.

> Maybe at the top of Area 4, or even a
> bit higher, but in any case, the stress in the region will be below what it
> was at Point 1 before stress relief.


see above.

>
> By the way, I have also have a materials background (a B.S. in Materials
> Engineering from way back, though I don't work in the field - but neither do
> you). You occasionally provide some good information regarding materials,
> but more often than not, they are irreverant to the topic, diversions
> really. You get many basic engineering concepts wrong and are so delusional
> that you call others out when you are the one who usually has it wrong. And
> you pick nicks (Jobst helps by making absolutist statements) and miss the
> main points. (Such as brinelling vs. fretting in headsets... so what if you
> can brinell a lousy headset? They generally fail by frettting.)


with respect andrew, you're showing some confusion on your theory
basics. it's great to have another materials person onboard, but we
need to get some clarity here.