What happened to non-boutique inexpensive MO wheels?

[[email protected]]

On Wed, 01 Nov 2006 15:06:04 -0500, Peter Cole
<[email protected]> wrote:


>Sure, surface finish is important -- even high quality spokes often fail
>after taking a small chain nick. Jobst has remarked about the
>improvement in quality of modern spokes, speculating that if old spokes
>had been better he might not have discovered the benefits of stress
>relieving. Modern spokes may have reduced un-relieved breakage rates,
>but not eliminated them.

Dear Peter,

I'm fiddling with a simple vise setup for bending and stretching
spokes to see if any stress relief effects can be demonstrated by
heating the bends afterward:

Here's spoke run through holes drilled in the two right-hand bolts and
curving around the bolt on the left:

http://server5.theimagehosting.com/image.php?img=339a_spoke_rig.jpg
or http://tinyurl.com/y9kmws

Here's the spoke tightened to 165 kgf by tension gauge. The elbow
bends straight and disappears into one bolt, while the nipple cocks
sideways on the point of the other bolt:

http://server5.theimagehosting.com/image.php?img=340a_spoke_rig_165kgf.jpg
or http://tinyurl.com/ycnr2f

Here's the spoke with the elbow end cut off to allow removal (the
u-bend won't fit through the holes drilled in the bolt heads) and
showing the resulting bend:

http://server5.theimagehosting.com/image.php?img=341a_spoke_rig_elbow_cut.jpg
or http://tinyurl.com/yenfz9

I plan to bend a dozen stainless steel spokes up to the same tension,
measure the change in bend angle when they're heated to relieve
residual tensions, and then compare them to a dozen more spokes
treated the same way--but squeezed with a known force reasonably
similar to what a hand squeeze can do.

Right now, I'm working on the squeeze part, since pliers squeeze so
easily and powerfully that impressive bends are left in the spokes:

http://server5.theimagehosting.com/image.php?img=342a_spoke_squeeze_bends.jpg
or http://tinyurl.com/tdkf3

I've been sacrificing old carbon steel spokes, which bend the opposite
way from stainless steel spokes when heated, probably because the
carbon undergoes phase changes that overwhelm residual stress changes.

Anyway, here are some Sapim Leader straight 14 gauge spokes that just
arrived:

http://server5.theimagehosting.com/image.php?img=338a_sap.jpg
or http://tinyurl.com/ya3lzr

Notice the S-A-P stamped into them, a little below the elbow.
Obviously, Sapim doesn't think that these sharp-edged little dents
will lead to spoke failures. As far as I know, the spokes never break
down there.

I wonder if Sapim gets away with banging SAP into the spokes because
the stamping is not near the elbow or the threads, or because the
stamping stresses are mostly compressive.

Cheers,

Carl Fogel

 

[[email protected]]

On Wed, 01 Nov 2006 14:15:01 -0700, [email protected] wrote:

>On Wed, 01 Nov 2006 15:06:04 -0500, Peter Cole
><[email protected]> wrote:
>
>
>>Sure, surface finish is important -- even high quality spokes often fail
>>after taking a small chain nick. Jobst has remarked about the
>>improvement in quality of modern spokes, speculating that if old spokes
>>had been better he might not have discovered the benefits of stress
>>relieving. Modern spokes may have reduced un-relieved breakage rates,
>>but not eliminated them.
>
>Dear Peter,
>
>I'm fiddling with a simple vise setup for bending and stretching
>spokes to see if any stress relief effects can be demonstrated by
>heating the bends afterward:
>
>Here's spoke run through holes drilled in the two right-hand bolts and
>curving around the bolt on the left:
>
>http://server5.theimagehosting.com/image.php?img=339a_spoke_rig.jpg
>or http://tinyurl.com/y9kmws
>
>Here's the spoke tightened to 165 kgf by tension gauge. The elbow
>bends straight and disappears into one bolt, while the nipple cocks
>sideways on the point of the other bolt:
>
>http://server5.theimagehosting.com/image.php?img=340a_spoke_rig_165kgf.jpg
>or http://tinyurl.com/ycnr2f
>
>Here's the spoke with the elbow end cut off to allow removal (the
>u-bend won't fit through the holes drilled in the bolt heads) and
>showing the resulting bend:
>
>http://server5.theimagehosting.com/image.php?img=341a_spoke_rig_elbow_cut.jpg
>or http://tinyurl.com/yenfz9
>
>I plan to bend a dozen stainless steel spokes up to the same tension,
>measure the change in bend angle when they're heated to relieve
>residual tensions, and then compare them to a dozen more spokes
>treated the same way--but squeezed with a known force reasonably
>similar to what a hand squeeze can do.
>
>Right now, I'm working on the squeeze part, since pliers squeeze so
>easily and powerfully that impressive bends are left in the spokes:
>
>http://server5.theimagehosting.com/image.php?img=342a_spoke_squeeze_bends.jpg
>or http://tinyurl.com/tdkf3
>
>I've been sacrificing old carbon steel spokes, which bend the opposite
>way from stainless steel spokes when heated, probably because the
>carbon undergoes phase changes that overwhelm residual stress changes.
>
>Anyway, here are some Sapim Leader straight 14 gauge spokes that just
>arrived:
>
>http://server5.theimagehosting.com/image.php?img=338a_sap.jpg
>or http://tinyurl.com/ya3lzr
>
>Notice the S-A-P stamped into them, a little below the elbow.
>Obviously, Sapim doesn't think that these sharp-edged little dents
>will lead to spoke failures. As far as I know, the spokes never break
>down there.
>
>I wonder if Sapim gets away with banging SAP into the spokes because
>the stamping is not near the elbow or the threads, or because the
>stamping stresses are mostly compressive.
>
>Cheers,
>
>Carl Fogel

D'oh! Forget the pliers.

I should just tighten a dozen spokes to say 100 kgf.

Then do the same to another dozen spokes, but tighten them another 30
kgf to mimic previously measured spoke tension increases when spokes
were squeezed with 60 lb squeeze forces--same effect as squeezing,
with no extra bending.

CF

 

[jim beam]

Peter Cole wrote:
> jim beam wrote:
>> Peter Cole wrote:
>>> jim beam wrote:
>>>> [email protected] wrote:
>>>>> In article <[email protected]>,
>>>>> [email protected] says...
>>>>>
>>>>>> since we have yet to be privileged with sight of the jobstian
>>>>>> research that will revolutionize the world of materials by showing
>>>>>> how fatigue can be eliminated in a material with no endurance limit
>>>>>
>>>>> I thought most spokes were 304 stainless steel?
>>>>>
>>>> there's various grades used for spokes, but none have an endurance
>>>> limit. they have what's called a "fatigue limit" which is an
>>>> attempt to
>>>> quantify the stress they can endure for a given number of fatigue
>>>> cycles, but that's not the same thing. an endurance limit is the
>>>> stress
>>>> at which the material can endure an infinite number of cycles, and is
>>>> characterized by a "knee" in the s-n graph where the line goes
>>>> horizontal. mild steel is the classic material with this property, but
>>>> some titanium alloys also have it. no stainless alloys that i know of
>>>> have it.
>>>
>>> <users.wpi.edu/~cfurlong/me3320/lect13/Lect13.pdf>
>>> <bama.ua.edu/~mweaver/courses/MTE455/MTE455_2006_L26.pdf>
>>>
>>> That's not what they're teaching today.
>>
>> how so?
>>
>> regarding endurance limit, both seem to corroborate the same
>> definition as i, although the second uses fatigue limit and endurance
>> limit interchangeably between diagrams and text.
>>
>> regarding which alloys evidence an endurance limit, the first one says
>> some types of stainless can show it, but i saw no examples. or if
>> they did, and/or you know any, please share. i'm interested because
>> fwiu, endurance limits originate with the same mechanism that causes
>> strain aging, i.e. interstitial elements [carbon in mild steel and
>> oxygen in titanium] locking dislocations. the thing with chromium
>> passivated stainless is that there's very little carbon possible
>> without having chromium carbide precipitate at grain boundaries, a big
>> no-no for fatigue, among other things. there are other types of
>> "stainless", but they're not something you or i would buy off the
>> shelf and i've not heard of their use for fatigue resistance. i
>> definitely don't see them being used in bicycle spokes.
>
> As you say, the first notes claim some stainless steels have a flat S/N
> curve, some don't.

i'm not saying that. i've not seen a stainless steel that evidences an
endurance limit, as defined by a "knee" in the graph. some stainless
steels appear to flatten, but there is no knee, hence no endurance limit.

> The second reference claims that all stainless are
> flat (pg, 4) "Ferrous metals and other strain aging materials --
> Examples: low carbon steel, stainless steel, titanium, etc."

cite the alloys and explain the mechanism. endurance limit is cause by
the mechanism i explained, carbon in ferrous metals, and is problematic
in chromium passivated stainless, again for the reasons i explained.

>
> Another source is:
> <http://www.kuleuven.ac.be/bwk/materials/Teaching/master/wg12/l0200.htm#SEC_6_1>
>
>
> Sec. 5.1
>
> "The S-N curves for ferrous and titanium alloys exhibit a limiting
> stress below which failure does not occur; this is called the fatigue or
> the endurance limit. The branch point or "knee" of the curve lies
> normally in the 105 to 107 cycle range. In aluminium and other
> nonferrous alloys there is no stress asymptote and a finite fatigue life
> exists at any stress level. All materials, however, exhibit a relatively
> flat curve in the high-cycle region, ie. at lives longer than about 105
> cycles."

which supports what i said before.

 

In article <[email protected]>, [email protected] says...
> Peter Cole wrote:

> Just before the section you quoted, the author of that page writes:
>
> > 6.5 Effects of Surface Finish
> > Almost all fatigue cracks nucleate at the surface since slip occurs
> > easier here than in the interior. Additionally, simple fracture
> > mechanics considerations show that surface defects and notches are
> > much more damaging than internal defects of similar size. The
> > physical condition and stress situation at the surface is therefore
> > of prime importance for the fatigue performance.

That fits with an insurance industry article I read earlier this year on
fatigue failures of stainless machine components in harsh environments.

While stainless is corrosion-resistant, it's not corrosion-proof, and
some manufacturers apparently fail to de-rate the fatigue limit of
stainless componenets and fasteners used in corrosive environments.
Can't remember the other details precisely, though I seem to recall they
suggested de-rating the fatigue limit of stainless in corrosive
environments to 1/3 of the nominal fatigue limit because of the surface
imperfections introduced by corrosion.


--
[email protected] is Joshua Putnam
<http://www.phred.org/~josh/>
Braze your own bicycle frames. See
<http://www.phred.org/~josh/build/build.html>

 

[jim beam]

Peter Cole wrote:
> Another interesting quote from
>
> <http://www.kuleuven.ac.be/bwk/materials/Teaching/master/wg12/l0200.htm#SEC_6_1>
>
> Sec. 6.6
>
> "Residual stresses or internal stresses are produced when a region of a
> part is strained beyond the elastic limit while other regions are
> elastically deformed. When the force or deformation causing the
> deformation are removed, the elastically deformed material springs back
> and impose residual stresses in the plastically deformed material.
> Yielding can be caused by thermal expansion as well as by external
> force. The residual stresses are of the opposite sign to the initially
> applied stress. Therefore, if a notched member is loaded in tension
> until yielding occurs, the notch root will experience a compressive
> stress after unloading. Welding stresses which are locked in when the
> weld metal contracts during cooling are an example of highly damaging
> stresses that cannot be avoided during fabrication. These stresses are
> of yield stress magnitude and tensile and compressive stresses must
> always balance each other, as indicated in Figure 26. The high tensile
> welding stresses contribute to a large extent to the poor fatigue
> performance of welded joints."
>
> "Residual stresses have a similar influence on fatigue life as
> externally imposed mean stresses, ie. a tensile stress reduces fatigue
> life while a compressive stress increases life. There is, however, an
> important difference which relates to the stability of residual
> stresses. While an externally imposed mean stress, eg. stress caused by
> dead weight always acts (as long as the load is present), residual
> stress may relax with time, especially if there are high peaks in the
> load spectrum that cause local yielding at stress concentrations."

dude, with respect, residual stress has NOTHING to do with endurance
limits!!!

 

[jim beam]

dvt wrote:
> Peter Cole wrote:
>> Another interesting quote from
>>
>> <http://www.kuleuven.ac.be/bwk/materials/Teaching/master/wg12/l0200.htm#SEC_6_1>
>>
>>
>> Sec. 6.6
>>
>> "Residual stresses or internal stresses are produced when a region of
>> a part is strained beyond the elastic limit while other regions are
>> elastically deformed. When the force or deformation causing the
>> deformation are removed, the elastically deformed material springs
>> back and impose residual stresses in the plastically deformed
>> material. Yielding can be caused by thermal expansion as well as by
>> external force. The residual stresses are of the opposite sign to the
>> initially applied stress. Therefore, if a notched member is loaded
>> in tension until yielding occurs, the notch root will experience a
>> compressive stress after unloading. Welding stresses which are locked
>> in when the weld metal contracts during cooling are an example of
>> highly damaging stresses that cannot be avoided during fabrication.
>> These stresses are of yield stress magnitude and tensile and
>> compressive stresses must always balance each other, as indicated in
>> Figure 26. The high tensile welding stresses contribute to a large
>> extent to the poor fatigue performance of welded joints."
>>
>> "Residual stresses have a similar influence on fatigue life as
>> externally imposed mean stresses, ie. a tensile stress reduces fatigue
>> life while a compressive stress increases life. There is, however, an
>> important difference which relates to the stability of residual
>> stresses. While an externally imposed mean stress, eg. stress caused
>> by dead weight always acts (as long as the load is present), residual
>> stress may relax with time, especially if there are high peaks in the
>> load spectrum that cause local yielding at stress concentrations."
>
> That's a great link, Peter! Thanks.
>
> Just before the section you quoted, the author of that page writes:
>
>> 6.5 Effects of Surface Finish
>> Almost all fatigue cracks nucleate at the surface since slip occurs
>> easier here than in the interior. Additionally, simple fracture
>> mechanics considerations show that surface defects and notches are
>> much more damaging than internal defects of similar size. The
>> physical condition and stress situation at the surface is therefore
>> of prime importance for the fatigue performance.
>
> Combining these factors, any surface defect near a region with residual
> tensile stress would be a very weak point. A spoke elbow certainly has
> residual stress,

do we have evidence for that? a stress corrosion test is simple to do.
none of my test spokes have broken. have any of yours?

> and Jobstian theory (in agreement with section 6.6 of
> the link) says that the residual tensile stresses can be ameliorated by
> overload. Combining this with improved spoke processing to reduce
> surface defects (jim beamian theory, section 6.5 of the link), would
> result in a great reduction of broken spokes.

since /all/ fatigue initiates at free surfaces, regardless of residual
stress, the most important production consideration is surface finish
quality and other factors that can give rise to surface initiation.
residual stress is all well and good to worry about if other factors
have been eliminated, but they haven't. factors not least of which
being the fundamental design of a traditional spoke that requires it to
be loaded in bending mode at the critical elbow!!!

>
> Summary: perhaps both effects (residual stress and surface defects) play
> interactive roles in reducing spoke life. Treating either of these may
> be sufficient to all but eliminate broken spokes.
>
> Comments?
>

sure, if residual stress is sufficient to be a factor, it can help to
reduce it. but the necessary supposition that spoke manufacturers are
incompetent in order to take that position is something of a stretch.
since these supposed incompetents, the ones with the research budgets
and microscopes, spend their time worrying about surface finish and
material quality, /i/ don't think i'm going to back the supposition of a
guy that can't distinguish between materials that strain age and those
that don't or thinks that head set bearings can't true brinell.

 

[Paul Hobson]

landotter wrote:
> For inexpensive track hubs, I've been blown away by the quality of the
> Formulas on my new fixie.
>

Same here! (though one of the two pairs is branded /IRO/)

\\paul

 

[dvt]

jim beam wrote:
> dvt wrote:
>> Combining these factors, any surface defect near a region with
>> residual tensile stress would be a very weak point. A spoke elbow
>> certainly has residual stress,
>
> do we have evidence for that?

You guys went round and round on that one in an earlier thread (others
can look to
<http://groups.google.com/group/rec.bicycles.tech/browse_frm/thread/e4d1cf4c90ae456b>
for the gory details). I don't have anything to add to that discussion,
but I don't think you came out on top.

How would you design a test for residual stress in spoke elbows? I have
access to some equipment, but not "neutron/x-ray inferometry" [sic] that
you mentioned in the above-mentioned thread.

> a stress corrosion test is simple to do.
> none of my test spokes have broken.

Can you share details of your test? I don't know how this is relevant.

> have any of yours?

I don't think I've suggested that I've done any such test, nor have I
implied that I would know how to do such a test.

I have broken a few spokes in the past few years. All have failed at the
beginning of the threads, not at the elbow. This is anecdotal, not a
"test." I haven't kept any records of my spokes. I might have one of
those broken spokes around, if that helps.

> sure, if residual stress is sufficient to be a factor, it can help to
> reduce it. but the necessary supposition that spoke manufacturers are
> incompetent in order to take that position is something of a stretch.

I don't think it takes a supposition of incompetence. I'd wager that
spoke manufacturers use the cheapest possible method to get surface
finish good enough that 99+% of the spokes will survive their intended
use. But that leaves a few spokes with surface defects right at (or even
outside) the limit. Perhaps the life of these 3-sigma spokes could be
enhanced via reduction in residual stress.

--
Dave
dvt at psu dot edu

Everyone confesses that exertion which brings out all the powers of body
and mind is the best thing for us; but most people do all they can to
get rid of it, and as a general rule nobody does much more than
circumstances drive them to do. -Harriet Beecher Stowe, abolitionist and
novelist (1811-1896)

 

[Qui si parla Campagnolo]

Johnny Sunset aka Tom Sherman wrote:
> Qui si parla Campagnolo aka Peter Chisholm wrote:
> > Johnny Sunset aka Tom Sherman wrote:
> > > Qui si parla Campagnolo aka Peter Chisholm wrote:
> > > >
> > > > spokes and rims are consumables..hubs should be reused....
> > >
> > > Jobst Brandt writes <http://yarchive.net/bike/spoke_reuse.html>.
> > >
> > > --
> > > Tom Sherman - Here, not there.
> >
> > If the ERD is the same.
>
> True.
>
> How common are non-bearing hub failures, and of those, are most from
> radial spoking the wheel?
>
> --
> Tom Sherman - Here, not there.

Non bearing, flange destruction, a few. last one was a radial White
Industries hub. I would say not common, not unheard of tho. Depends on
the hub. If it is a high end one, like shimano, Campagnolo, Phil DT,
they will last a long time, can be rebuilt many time. I recently
rebuilt 25 yr old Phils into wheels and a Campag Tipo into wheels...I
ride a 1985 C-Record wheelset every dry day(Phils on my fixie).

Propriatary stuff spells the doom of many wheels. Protons, Heliums,
7700, Rolfs, the l;ist will get longer as time goes on. IF riders will
listen, most will opt for a handbuiult wheelset, regardless of who
builkds them, built well, of course. Less money, same weight, more
reliability but as we all know, marketing, bling, coffee shop points,
mean a whole lot. Peer pressure doesn't go away after HS.

 

[monkeyboy]

damyth wrote:
> OK, so I'm in the market for some nice but inexpensive pre-built
> traditional (32 spoke) 700c non-boutique wheels. I go over to the
> usual mail order places like Nashbar and Performance, but there are
> none to be found! All they have now are boutique wheels and
> non-boutique 650c.
.....

take a look at cbike.com, they have campy scrirroco wheels for $299,
great wheels at a great price...I guess they could be considered
boutique...?

 

[Peter Cole]

jim beam wrote:
> Peter Cole wrote:
>> jim beam wrote:
>>> Peter Cole wrote:
>>>> jim beam wrote:
>>>>> [email protected] wrote:
>>>>>> In article <[email protected]>,
>>>>>> [email protected] says...
>>>>>>
>>>>>>> since we have yet to be privileged with sight of the jobstian
>>>>>>> research that will revolutionize the world of materials by
>>>>>>> showing how fatigue can be eliminated in a material with no
>>>>>>> endurance limit
>>>>>>
>>>>>> I thought most spokes were 304 stainless steel?
>>>>>>
>>>>> there's various grades used for spokes, but none have an endurance
>>>>> limit. they have what's called a "fatigue limit" which is an
>>>>> attempt to
>>>>> quantify the stress they can endure for a given number of fatigue
>>>>> cycles, but that's not the same thing. an endurance limit is the
>>>>> stress
>>>>> at which the material can endure an infinite number of cycles, and is
>>>>> characterized by a "knee" in the s-n graph where the line goes
>>>>> horizontal. mild steel is the classic material with this property,
>>>>> but
>>>>> some titanium alloys also have it. no stainless alloys that i know of
>>>>> have it.
>>>>
>>>> <users.wpi.edu/~cfurlong/me3320/lect13/Lect13.pdf>
>>>> <bama.ua.edu/~mweaver/courses/MTE455/MTE455_2006_L26.pdf>
>>>>
>>>> That's not what they're teaching today.
>>>
>>> how so?
>>>
>>> regarding endurance limit, both seem to corroborate the same
>>> definition as i, although the second uses fatigue limit and endurance
>>> limit interchangeably between diagrams and text.
>>>
>>> regarding which alloys evidence an endurance limit, the first one
>>> says some types of stainless can show it, but i saw no examples. or
>>> if they did, and/or you know any, please share. i'm interested
>>> because fwiu, endurance limits originate with the same mechanism that
>>> causes strain aging, i.e. interstitial elements [carbon in mild steel
>>> and oxygen in titanium] locking dislocations. the thing with
>>> chromium passivated stainless is that there's very little carbon
>>> possible without having chromium carbide precipitate at grain
>>> boundaries, a big no-no for fatigue, among other things. there are
>>> other types of "stainless", but they're not something you or i would
>>> buy off the shelf and i've not heard of their use for fatigue
>>> resistance. i definitely don't see them being used in bicycle spokes.
>>
>> As you say, the first notes claim some stainless steels have a flat
>> S/N curve, some don't.
>
> i'm not saying that. i've not seen a stainless steel that evidences an
> endurance limit, as defined by a "knee" in the graph. some stainless
> steels appear to flatten, but there is no knee, hence no endurance limit.
>
>> The second reference claims that all stainless are flat (pg, 4)
>> "Ferrous metals and other strain aging materials -- Examples: low
>> carbon steel, stainless steel, titanium, etc."
>
> cite the alloys and explain the mechanism. endurance limit is cause by
> the mechanism i explained, carbon in ferrous metals, and is problematic
> in chromium passivated stainless, again for the reasons i explained.
>
>>
>> Another source is:
>> <http://www.kuleuven.ac.be/bwk/materials/Teaching/master/wg12/l0200.htm#SEC_6_1>
>>
>>
>> Sec. 5.1
>>
>> "The S-N curves for ferrous and titanium alloys exhibit a limiting
>> stress below which failure does not occur; this is called the fatigue
>> or the endurance limit. The branch point or "knee" of the curve lies
>> normally in the 105 to 107 cycle range. In aluminium and other
>> nonferrous alloys there is no stress asymptote and a finite fatigue
>> life exists at any stress level. All materials, however, exhibit a
>> relatively flat curve in the high-cycle region, ie. at lives longer
>> than about 105 cycles."
>
> which supports what i said before.

I cited 3 sources, 2 of which said all stainless steels have an
endurance limit, the other said some did, some didn't.

From:
<www.stainless-steel-world.net/pdf/11021.pdf>

Page 30 shows an S/N graph for 2 types of stainless, one of which is
common 316. There is clearly a fatigue limit for both alloys.

 

[Peter Cole]

jim beam wrote:
> Peter Cole wrote:
>> Another interesting quote from
>>
>> <http://www.kuleuven.ac.be/bwk/materials/Teaching/master/wg12/l0200.htm#SEC_6_1>
>>
>> Sec. 6.6
>>
>> "Residual stresses or internal stresses are produced when a region of
>> a part is strained beyond the elastic limit while other regions are
>> elastically deformed. When the force or deformation causing the
>> deformation are removed, the elastically deformed material springs
>> back and impose residual stresses in the plastically deformed
>> material. Yielding can be caused by thermal expansion as well as by
>> external force. The residual stresses are of the opposite sign to the
>> initially applied stress. Therefore, if a notched member is loaded in
>> tension until yielding occurs, the notch root will experience a
>> compressive stress after unloading. Welding stresses which are locked
>> in when the weld metal contracts during cooling are an example of
>> highly damaging stresses that cannot be avoided during fabrication.
>> These stresses are of yield stress magnitude and tensile and
>> compressive stresses must always balance each other, as indicated in
>> Figure 26. The high tensile welding stresses contribute to a large
>> extent to the poor fatigue performance of welded joints."
>>
>> "Residual stresses have a similar influence on fatigue life as
>> externally imposed mean stresses, ie. a tensile stress reduces fatigue
>> life while a compressive stress increases life. There is, however, an
>> important difference which relates to the stability of residual
>> stresses. While an externally imposed mean stress, eg. stress caused
>> by dead weight always acts (as long as the load is present), residual
>> stress may relax with time, especially if there are high peaks in the
>> load spectrum that cause local yielding at stress concentrations."
>
> dude, with respect, residual stress has NOTHING to do with endurance
> limits!!!

No, it doesn't, but you were the one who put them together upthread:

"Since we have yet to be privileged with sight of the jobstian research
that will revolutionize the world of materials by showing how fatigue
can be eliminated in a material with no endurance limit and, we're
somewhat thin on evidence for this supposition that spokes are sent from
the factory containing residual stress"

My cite above was intended as a rebuttal to your (frequent) denial that
mechanical stress relieving doesn't reduce residual stress.

 

[Peter Cole]

[email protected] wrote:
> In article <[email protected]>, [email protected] says...
>> Peter Cole wrote:
>
>> Just before the section you quoted, the author of that page writes:
>>
>>> 6.5 Effects of Surface Finish
>>> Almost all fatigue cracks nucleate at the surface since slip occurs
>>> easier here than in the interior. Additionally, simple fracture
>>> mechanics considerations show that surface defects and notches are
>>> much more damaging than internal defects of similar size. The
>>> physical condition and stress situation at the surface is therefore
>>> of prime importance for the fatigue performance.
>
> That fits with an insurance industry article I read earlier this year on
> fatigue failures of stainless machine components in harsh environments.
>
> While stainless is corrosion-resistant, it's not corrosion-proof, and
> some manufacturers apparently fail to de-rate the fatigue limit of
> stainless componenets and fasteners used in corrosive environments.
> Can't remember the other details precisely, though I seem to recall they
> suggested de-rating the fatigue limit of stainless in corrosive
> environments to 1/3 of the nominal fatigue limit because of the surface
> imperfections introduced by corrosion.
>
>

This is pretty common knowledge in marine environments.

A more surprising fact is the loss of fatigue strength in many steels
upon exposure to even pure water. The often cited "infinite fatigue
life" may disappear completely. People forget that the S/N behavior
usually referenced is for small, highly polished samples.

 

[Donald Gillies]

"Qui si parla Campagnolo" <[email protected]> writes:
>>
>> How common are non-bearing hub failures, and of those, are most from
>> radial spoking the wheel?
>>

>Non bearing, flange destruction, a few. last one was a radial White
>Industries hub.

Just goes to show that CNC'ing a hub (as White Industries does) is no
substitute for real cold-forging. Forged hubs are much less likely to
have a failure in the flanges. I have a garage full of bikes, with no
hub newer than 1980, and most of them are wide-flange forged hubs,
which may actually be stronger since the 36 spoke holes are much
farther apart.

- Don Gillies
San Diego, CA

 

[bill]

Michael Press wrote:
> In article
> <[email protected]>,
> John Forrest Tomlinson <[email protected]>
> wrote:
>
> > On Sun, 29 Oct 2006 09:15:44 GMT, Michael Press <[email protected]> wrote:
> >
> > >In article
> > ><[email protected]>,
> > > "damyth" <[email protected]> wrote:
> > >
> > >> OK, so I'm in the market for some nice but inexpensive pre-built
> > >> traditional (32 spoke) 700c non-boutique wheels. I go over to the
> > >> usual mail order places like Nashbar and Performance, but there are
> > >> none to be found! All they have now are boutique wheels and
> > >> non-boutique 650c.
> > >
> > >So, now 32 spoke wheels are traditional?
> >

Yes, 32x is traditional light racing. Has been for like decades. Was
normal for light racing when I started in the 70s. 36x standard, 32x
light, 28x specialty/ front/pursuit, 40 touring, 48 tandem. All
traditional.

He's talking traditional, not standard. Many different configurations
and spoke arrangements are traditional. Hi, low, 2,3,4, straight cross.
All methods have been used traditionally.

Compared to 17 spoke superwhizbang reverse cross pushrod cantilever
sidewinder ergopower wheels, 32x is traditional. Absolutely. Built with
the same parts and methods as wheels built in the 1920s. Just new
aluminum instead of wood. Number of spokes per se has nothing to do
with traditional.

OK enough ranting

 

[jim beam]

Peter Cole wrote:
> jim beam wrote:
>> Peter Cole wrote:
>>> jim beam wrote:
>>>> Peter Cole wrote:
>>>>> jim beam wrote:
>>>>>> [email protected] wrote:
>>>>>>> In article <[email protected]>,
>>>>>>> [email protected] says...
>>>>>>>
>>>>>>>> since we have yet to be privileged with sight of the jobstian
>>>>>>>> research that will revolutionize the world of materials by
>>>>>>>> showing how fatigue can be eliminated in a material with no
>>>>>>>> endurance limit
>>>>>>>
>>>>>>> I thought most spokes were 304 stainless steel?
>>>>>>>
>>>>>> there's various grades used for spokes, but none have an endurance
>>>>>> limit. they have what's called a "fatigue limit" which is an
>>>>>> attempt to
>>>>>> quantify the stress they can endure for a given number of fatigue
>>>>>> cycles, but that's not the same thing. an endurance limit is the
>>>>>> stress
>>>>>> at which the material can endure an infinite number of cycles, and is
>>>>>> characterized by a "knee" in the s-n graph where the line goes
>>>>>> horizontal. mild steel is the classic material with this
>>>>>> property, but
>>>>>> some titanium alloys also have it. no stainless alloys that i
>>>>>> know of
>>>>>> have it.
>>>>>
>>>>> <users.wpi.edu/~cfurlong/me3320/lect13/Lect13.pdf>
>>>>> <bama.ua.edu/~mweaver/courses/MTE455/MTE455_2006_L26.pdf>
>>>>>
>>>>> That's not what they're teaching today.
>>>>
>>>> how so?
>>>>
>>>> regarding endurance limit, both seem to corroborate the same
>>>> definition as i, although the second uses fatigue limit and
>>>> endurance limit interchangeably between diagrams and text.
>>>>
>>>> regarding which alloys evidence an endurance limit, the first one
>>>> says some types of stainless can show it, but i saw no examples. or
>>>> if they did, and/or you know any, please share. i'm interested
>>>> because fwiu, endurance limits originate with the same mechanism
>>>> that causes strain aging, i.e. interstitial elements [carbon in mild
>>>> steel and oxygen in titanium] locking dislocations. the thing with
>>>> chromium passivated stainless is that there's very little carbon
>>>> possible without having chromium carbide precipitate at grain
>>>> boundaries, a big no-no for fatigue, among other things. there are
>>>> other types of "stainless", but they're not something you or i would
>>>> buy off the shelf and i've not heard of their use for fatigue
>>>> resistance. i definitely don't see them being used in bicycle spokes.
>>>
>>> As you say, the first notes claim some stainless steels have a flat
>>> S/N curve, some don't.
>>
>> i'm not saying that. i've not seen a stainless steel that evidences
>> an endurance limit, as defined by a "knee" in the graph. some
>> stainless steels appear to flatten, but there is no knee, hence no
>> endurance limit.
>>
>>> The second reference claims that all stainless are flat (pg, 4)
>>> "Ferrous metals and other strain aging materials -- Examples: low
>>> carbon steel, stainless steel, titanium, etc."
>>
>> cite the alloys and explain the mechanism. endurance limit is cause
>> by the mechanism i explained, carbon in ferrous metals, and is
>> problematic in chromium passivated stainless, again for the reasons i
>> explained.
>>
>>>
>>> Another source is:
>>> <http://www.kuleuven.ac.be/bwk/materials/Teaching/master/wg12/l0200.htm#SEC_6_1>
>>>
>>>
>>> Sec. 5.1
>>>
>>> "The S-N curves for ferrous and titanium alloys exhibit a limiting
>>> stress below which failure does not occur; this is called the fatigue
>>> or the endurance limit. The branch point or "knee" of the curve lies
>>> normally in the 105 to 107 cycle range. In aluminium and other
>>> nonferrous alloys there is no stress asymptote and a finite fatigue
>>> life exists at any stress level. All materials, however, exhibit a
>>> relatively flat curve in the high-cycle region, ie. at lives longer
>>> than about 105 cycles."
>>
>> which supports what i said before.
>
> I cited 3 sources, 2 of which said all stainless steels have an
> endurance limit, the other said some did, some didn't.

with respect, one of those two uses "endurance limit" and "fatigue
limit" interchangeably. where i come from, the words "endurance limit"
are reserved for graphs showing the knee, "fatigue limit" is for those
that don't. engineers don't seem to regard materials definitions as
important as materials people, hence the dearth of engineering papers
perpetuating the confusion.

>
> From:
> <www.stainless-steel-world.net/pdf/11021.pdf>
>
> Page 30 shows an S/N graph for 2 types of stainless, one of which is
> common 316. There is clearly a fatigue limit for both alloys.

ok, that's a good link, citing specific alloys. i have two comments:

1. endurance limit at 20-25% of yield is not really a reliable benefit.
2. fatigue is statistical. i'm not saying the publishers of this paper
don't know what they're doing, but be honest peter, there are not a lot
of other materials out there supporting this position - most to the
contrary in fact. therefore, in this portion of the graph, whether you
want to fit one curve or another is open to debate. the determinant,
imo, is whether a mechanism for endurance limit can be identified. in
mild steel, it's carbon diffusion. in titanium, it's oxygen. what is
it here? nitrogen?

 

[jim beam]

Peter Cole wrote:
> jim beam wrote:
>> Peter Cole wrote:
>>> Another interesting quote from
>>>
>>> <http://www.kuleuven.ac.be/bwk/materials/Teaching/master/wg12/l0200.htm#SEC_6_1>
>>>
>>> Sec. 6.6
>>>
>>> "Residual stresses or internal stresses are produced when a region of
>>> a part is strained beyond the elastic limit while other regions are
>>> elastically deformed. When the force or deformation causing the
>>> deformation are removed, the elastically deformed material springs
>>> back and impose residual stresses in the plastically deformed
>>> material. Yielding can be caused by thermal expansion as well as by
>>> external force. The residual stresses are of the opposite sign to the
>>> initially applied stress. Therefore, if a notched member is loaded in
>>> tension until yielding occurs, the notch root will experience a
>>> compressive stress after unloading. Welding stresses which are locked
>>> in when the weld metal contracts during cooling are an example of
>>> highly damaging stresses that cannot be avoided during fabrication.
>>> These stresses are of yield stress magnitude and tensile and
>>> compressive stresses must always balance each other, as indicated in
>>> Figure 26. The high tensile welding stresses contribute to a large
>>> extent to the poor fatigue performance of welded joints."
>>>
>>> "Residual stresses have a similar influence on fatigue life as
>>> externally imposed mean stresses, ie. a tensile stress reduces
>>> fatigue life while a compressive stress increases life. There is,
>>> however, an important difference which relates to the stability of
>>> residual stresses. While an externally imposed mean stress, eg.
>>> stress caused by dead weight always acts (as long as the load is
>>> present), residual stress may relax with time, especially if there
>>> are high peaks in the load spectrum that cause local yielding at
>>> stress concentrations."
>>
>> dude, with respect, residual stress has NOTHING to do with endurance
>> limits!!!
>
> No, it doesn't, but you were the one who put them together upthread:
>
> "Since we have yet to be privileged with sight of the jobstian research
> that will revolutionize the world of materials by showing how fatigue
> can be eliminated in a material with no endurance limit and, we're
> somewhat thin on evidence for this supposition that spokes are sent from
> the factory containing residual stress"
>
> My cite above was intended as a rebuttal to your (frequent) denial that
> mechanical stress relieving doesn't reduce residual stress.

context: i was contrasting the credibility of someone that claims they
can eliminate fatigue in a situation where they can't, with the fact
that they're making unsupported suppositions.

i've never said you cannot mechanically relieve residual stress. i
/have/ however questioned whether spokes leave the factory with
sufficient residual stress to initiate fatigue /and/ i've questioned the
efficacy of "stress relief" applied after spoke manufacture. mechanical
stress relief is typically only effective a short time after initial
deformation. waiting more than a few hours [as will be necessary to
ship from the spoke manufacturer to the wheel builder] will render this
method useless. and then we can get into the debate of spoke squeezing
itself and whether a process that produces no detectable deformation is
actually yielding the material sufficiently to work as is being
supposed, [timing issues aside of course].

 

[jim beam]

dvt wrote:
> jim beam wrote:
>> dvt wrote:
>>> Combining these factors, any surface defect near a region with
>>> residual tensile stress would be a very weak point. A spoke elbow
>>> certainly has residual stress,
>>
>> do we have evidence for that?
>
> You guys went round and round on that one in an earlier thread (others
> can look to
> <http://groups.google.com/group/rec.bicycles.tech/browse_frm/thread/e4d1cf4c90ae456b>
> for the gory details). I don't have anything to add to that discussion,
> but I don't think you came out on top.
>
> How would you design a test for residual stress in spoke elbows? I have
> access to some equipment, but not "neutron/x-ray inferometry" [sic] that
> you mentioned in the above-mentioned thread.

chlorides are well known for their stress corrosion in stainless steel.
google will help you identify other agents as well. simply leave a
spoke in a jar of the requisite solution and wait.

>
>> a stress corrosion test is simple to do. none of my test spokes have
>> broken.
>
> Can you share details of your test? I don't know how this is relevant.

see above.

>
>> have any of yours?
>
> I don't think I've suggested that I've done any such test, nor have I
> implied that I would know how to do such a test.
>
> I have broken a few spokes in the past few years. All have failed at the
> beginning of the threads, not at the elbow. This is anecdotal, not a
> "test." I haven't kept any records of my spokes. I might have one of
> those broken spokes around, if that helps.

since spoke elbows are the commonest failure point, let's focus on
those. fatigue at threads is common enough in other fastener applications.

>
>> sure, if residual stress is sufficient to be a factor, it can help to
>> reduce it. but the necessary supposition that spoke manufacturers are
>> incompetent in order to take that position is something of a stretch.
>
> I don't think it takes a supposition of incompetence.

i disagree. according to jobstian theory, the supposition is that
spokes leave the factory with residual stress, ergo the manufacturer is
incompetent for not relieving it.

> I'd wager that
> spoke manufacturers use the cheapest possible method to get surface
> finish good enough that 99+% of the spokes will survive their intended
> use.

indeed.

> But that leaves a few spokes with surface defects right at (or even
> outside) the limit. Perhaps the life of these 3-sigma spokes could be
> enhanced via reduction in residual stress.
>
perhaps, but we'd then have to show that residual stress was a factor
and that material quality was not. seriously, if spoke squeezing was
able to eliminate fatigue regardless, don't you think manufacturers
would just do that and use cheaper materials and cheaper processing
rather than what they do now?

 

[jim beam]

Peter Cole wrote:
> [email protected] wrote:
>> In article <[email protected]>, [email protected] says...
>>> Peter Cole wrote:
>>
>>> Just before the section you quoted, the author of that page writes:
>>>
>>>> 6.5 Effects of Surface Finish
>>>> Almost all fatigue cracks nucleate at the surface since slip occurs
>>>> easier here than in the interior. Additionally, simple fracture
>>>> mechanics considerations show that surface defects and notches are
>>>> much more damaging than internal defects of similar size. The
>>>> physical condition and stress situation at the surface is therefore
>>>> of prime importance for the fatigue performance.
>>
>> That fits with an insurance industry article I read earlier this year
>> on fatigue failures of stainless machine components in harsh
>> environments.
>> While stainless is corrosion-resistant, it's not corrosion-proof, and
>> some manufacturers apparently fail to de-rate the fatigue limit of
>> stainless componenets and fasteners used in corrosive environments.
>> Can't remember the other details precisely, though I seem to recall
>> they suggested de-rating the fatigue limit of stainless in corrosive
>> environments to 1/3 of the nominal fatigue limit because of the
>> surface imperfections introduced by corrosion.
>>
>>
>
> This is pretty common knowledge in marine environments.
>
> A more surprising fact is the loss of fatigue strength in many steels
> upon exposure to even pure water. The often cited "infinite fatigue
> life" may disappear completely. People forget that the S/N behavior
> usually referenced is for small, highly polished samples.

thank you.

 

[Michael Press]

In article
<[email protected]>
,
"bill" <[email protected]> wrote:

> Michael Press wrote:
> > In article
> > <[email protected]>,
> > John Forrest Tomlinson <[email protected]>
> > wrote:
> >
> > > On Sun, 29 Oct 2006 09:15:44 GMT, Michael Press <[email protected]> wrote:
> > >
> > > >In article
> > > ><[email protected]>,
> > > > "damyth" <[email protected]> wrote:
> > > >
> > > >> OK, so I'm in the market for some nice but inexpensive pre-built
> > > >> traditional (32 spoke) 700c non-boutique wheels. I go over to the
> > > >> usual mail order places like Nashbar and Performance, but there are
> > > >> none to be found! All they have now are boutique wheels and
> > > >> non-boutique 650c.
> > > >
> > > >So, now 32 spoke wheels are traditional?
> > >
>
> Yes, 32x is traditional light racing. Has been for like decades. Was
> normal for light racing when I started in the 70s. 36x standard, 32x
> light, 28x specialty/ front/pursuit, 40 touring, 48 tandem. All
> traditional.
>
> He's talking traditional, not standard. Many different configurations
> and spoke arrangements are traditional. Hi, low, 2,3,4, straight cross.
> All methods have been used traditionally.
>
> Compared to 17 spoke superwhizbang reverse cross pushrod cantilever
> sidewinder ergopower wheels, 32x is traditional. Absolutely. Built with
> the same parts and methods as wheels built in the 1920s. Just new
> aluminum instead of wood. Number of spokes per se has nothing to do
> with traditional.
>
> OK enough ranting

S'allright. My question was at least 50% serious. I am
not stuck on tradition. I bought a frame with a
thread-less steering tube, but built 36 spoke wheels.
The answer is a qualified yes. Thanks.

--
Michael Press