What happened to non-boutique inexpensive MO wheels?

[Johnny Sunset aka Tom Sherman]

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.

 

[landotter]

[email protected] wrote:
> landotter wrote:
> > damyth wrote:
> > > What a good source for Velocity or Alex clincher rims (and are
> > > Alex any good)?
> >
> > I sourced my last rims at aebike.com. Super speedy service and
> > seriously low prices. As far as Alex rims go, I've owned a lot of bike
> > over around 20 years of semi-serious riding and commuting, and Alex
> > rims are the only brand that's never ever let me down. I've had four
> > sets of wheels with them. A lot of people kvetch about them, but I'll
> > venture and guess that their wheels were built poorly, and it wasn't
> > the fault of the rim. Their basic silver eyeletted box section rim is
> > the most reliable rim I've ever used. Model number DM18 (I think).
> > Twenty bucks a pop. Your mileage may vary, offer does not apply on
> > Sundays.
>
> I've been riding a bit the past 25 years and I'd never heard of the
> name "Alex" in the bike industry before about 1 year ago. I'm more
> than a bit surprised to hear they have been around for two decades.

I've been riding them on road and utility bikes for a decade now.
Perfectly decent stuff. They make rims at all price points. You'd have
heard of them earlier had you been into BMX. They came as OEM for many
years before they caught on in catalogs. I'll take Alex over Mavic any
day of the week. Can't be beat for value. Sun and Velocity are nice as
well, but nothing wrong with a properly laced Alex.

 

[landotter]

Qui si parla Campagnolo wrote:
> Dan wrote:
> > landotter wrote:
> > > damyth wrote:
> > >> What a good source for Velocity or Alex clincher rims (and are
> > >> Alex any good)?
> > >
> > > I sourced my last rims at aebike.com. Super speedy service and
> > > seriously low prices. As far as Alex rims go, I've owned a lot of bike
> > > over around 20 years of semi-serious riding and commuting, and Alex
> > > rims are the only brand that's never ever let me down. I've had four
> > > sets of wheels with them. A lot of people kvetch about them, but I'll
> > > venture and guess that their wheels were built poorly, and it wasn't
> > > the fault of the rim. Their basic silver eyeletted box section rim is
> > > the most reliable rim I've ever used. Model number DM18 (I think).
> > > Twenty bucks a pop. Your mileage may vary, offer does not apply on
> > > Sundays.
> > >
> > > I'd say build a set for fun, between some decent Alex rims, stainless
> > > spokes, and hubs sourced from Ebay or craigslist, you should be able
> > > throw some super durable wheels together for around a hundred bucks or
> > > so.
> > >
> > There are cheap Alex wheels out there such as:
> >
> > http://tinyurl.com/ykzavx
>
> spokes and rims are consumables..hubs should be reused. With a $50
> wheel, don't expect a decent hub.

Take a Sora or 2200 low end hub. $10-15 or so. Repack and adjust with
good grease and $1 worth of 25 grade bearings and you'll have a hub
that will last a long time and spin smooth. Won't be good looking, but
in a pinch does the trick. Soras or 2200s will pit and score in just a
few miles out of the box, but the functional quality is due mainly to
adjustment and the bearing quality. Again, they're not pleasant on the
eyes, but for a tenner, whaddaya expect?

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

 

[Qui si parla Campagnolo]

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.

 

[Ozark Bicycle]

[email protected] wrote:
> On 29 Oct 2006 05:45:29 -0800, "Qui si parla Campagnolo"
> <[email protected]> wrote:
>
> >
> >damyth wrote:
> >> [email protected] wrote:
> >> > On 28 Oct 2006 23:43:13 -0700, "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.
> >> >
> >> > [snip]
> >> >
> >> > Dear Damyth,
> >> >
> >> > Possibly you need to sort the Performance Bike wheel page from low to
> >> > high price? Or adjust your notion of inexpensive for inflation? Or
> >> > wait for sales?
> >> >
> >> > http://www.performancebike.com/shop...20&orderby=2&filterby=&view_all=0&searchSize=
> >> >
> >> > Mavic Open Pro CD 32-spoke front $119.99:
> >> > http://www.performancebike.com/shop/profile.cfm?SKU=19030&subcategory_ID=5320
> >> >
> >> > Ultegra Open Pro Silver 32-spoke front $119.9:
> >> > http://www.performancebike.com/shop/profile.cfm?SKU=19027&subcategory_ID=5320
> >> >
> >> > And so on.
> >> >
> >> > Cheers,
> >> >
> >> > Carl Fogel
> >>
> >> Had you read my original post in its entirety (which you snipped)
> >> perhaps you would have realized I'd avoid Mavic like the plague. In
> >> fact I believe my exact words were: "Ever since my Mavic rims started
> >> cracking at eyelets I've stopped using them." Perhaps I could have
> >> been clearer in my writing style, but explain to me why I should go
> >> back using/buying the same rims that cracked once on me already.
> >
> >Gotta excuse Carl, sometimes his whizbang internet connection and
> >typing skills get in the way.
> >
> >$350 gets you Ultegra hubs, Velocity Aero rims, DT db spokes and
> >Vecchio's build-
>
>
> Actually, I read it, but when someone is complaining that they can't
> get cheap mail order rims, worrying about brand seems a bit much.
>

Not if the OP is turned off to the Mavic brand due to premature rim
failures. Why would anyone want to spend over $200 for a pair of wheels
built with rims they think are failure prone?

 

[SYJ]

Michael Press wrote:

>
> What is done _now_ is not evidence that such is traditional.
>
> --
> Michael Press

You're right. When I refer to 'traditional' wheels, I'm generally
talking about something made of stone with a wooden axel ;-)

SYJ

 

[Johnny Sunset aka Tom Sherman]

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.

 

[David L. Johnson]

On Mon, 30 Oct 2006 17:19:48 -0800, Johnny Sunset aka Tom Sherman wrote:

> How common are non-bearing hub failures, and of those, are most from
> radial spoking the wheel?
>
Not, is the first answer. But, if most hub failures are bearing failures,
and the cups are not replaceable, then it does not matter. I have seen
pictures of hub flanges tearing out, but it's not obvious that these
failures are due to radial spoking. I used a front hub for several years
that had the spoke holes sliced to admit bladed spokes, which was not
Shimano's original intent, and the hub worked fine. I personally do not
believe that radial spoking is that horrible a thing to do, although the
name brands void their warrantee for it. For front wheels there is no
harm, and no advantage aside from coolness, to use radial spoking. For
the rear, right side, it is not a good idea although lots of boutique
wheels use it -- if they do, they have to beef up the hub shell, which
adds weight needlessly. Using radial spoking on the left side seems to be
a slight advantage, in that it helps deal with the extreme dish of modern
wheels.

--

David L. Johnson

__o | Do not worry about your difficulties in mathematics, I can
_`\(,_ | assure you that mine are all greater. -- A. Einstein
(_)/ (_) |

 

[jim beam]

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>.
>
why recirculate myth & lore?

choice quotes from that linkage:

* [they] "do not fatigue age with use"

* "they have residual locked in high stresses"

but here's the real peach:

"Once a set of spokes has been stress relieved and is working well, you
do yourself a great disservice by throwing them away when rebuilding
with a new rim because you must go through the weeding out of spokes
that will break due to peculiarities that leave them with residual
stress."

translation:
"so, having discarded the spokes that previous broke, we can now set up
to make claims about having eliminated fatigue".

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 [jobst has declined to provide
the results of his x-ray, neutron diffraction or even stress-corrosion
testing], i'd say it's time to stop propagating bad advice about
re-using spokes. sure, you can re-use at a pinch, but as a matter of
economics and engineering principle, it's an exercise in pointlessness.

 

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?

--
[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]

[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.

 

[Ted P.]

SYJ wrote:
> Michael Press wrote:
>
>> What is done _now_ is not evidence that such is traditional.
>>
>> --
>> Michael Press
>
> You're right. When I refer to 'traditional' wheels, I'm generally
> talking about something made of stone with a wooden axel ;-)
>
> SYJ
>
Those cavemen types had it rough. Draggin' home a new wife you bonked
over the head and makin' wheels outa big rocks with nothin' but a wooden
axe(l).

--

Ted
Don't forget to take out the trash

 

[Peter Cole]

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.

 

[Rick]

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.
>
> I always used to get pre-built wheels via MO since those places offered
> wheelsets at lower prices than the cost of individual of components.
> Is this a fluke (maybe these places ran out traditional wheels since
> it's end of the season) or the wave of the future? I really hope it's
> not the latter. I remember even 6 months ago Nashbar was selling
> Ritchey OCR wheelsets at extremely low prices. I'm kicking myself now
> for not having bought some then.
>
> In any case, please recommend decently durable rims for riders less
> than 165 lbs. Need the right balance between durability and weight.
> Ever since my Mavic rims started cracking at eyelets I've stopped using
> them. What a good source for Velocity or Alex clincher rims (and are
> Alex any good)?

Nasbar is Performance's surplus house; they sell what they get cheap as
surplus. Those Ritchey OCR wheels you saw meant some supplier or
vendor had an overstock Performance could pick up on the cheap and sell
at low prices. Not a reliable way to find parts.

As for Mavic rims, I too have had issues with MA3's and will not use
them. But the Open Pro and T520/A719 are rock solid components and I
would not hestitate to use either; in fact I will probably be looking
from some A719's soon as my wife has 14K miles on the wheels on her
commuter which are based on T520 (same rim, different name/number).
Why not just get a good set of wheels on a rock solid hub you can use
for years?

- rick

 

[jim beam]

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.

 

[Peter Cole]

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. 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."

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."

 

[[email protected]]

On Wed, 01 Nov 2006 10:20:42 -0500, Peter Cole
<[email protected]> 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. 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."
>
>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."


This is "jim beam" you're arguing with - he's the guy that thinks that
you tighten a cotter pin with the nut. You'd best give up; if you
don't, eventually he'll suggest trial by combat is the best way to
decide the truth.

 

[Peter Cole]

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."

 

[dvt]

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, 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.

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?

--
Dave
dvt at psu dot edu

 

[Peter Cole]

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, 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.
>
> 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, 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.