I fixed a broken spoke!
dgk
one was not on the drive side. So I took a spoke from a retired wheel
(rear wheel same bike) and replaced the broken one using the same
pattern as the nearby spokes.
Once I put the wheel on the bike I was able to true it pretty well by
seeing how that section passed the brakes. A few twists and it kept
the same distance as the rest of the wheel. It rode fine this morning.
I was just on the SheldonBrown site looking at freehubs, and it looks
easy enough to remove the cassette. I think I'll almost look forward
to the next broken spoke so I have an excuse to remove the cassette.
It's almost sure to be on the drive side.
Do I have to be concerned about Dish? It seems that if the rest of the
wheel is correct and this one spoke has been adjusted so that the rim
is straight, then the dish is correct?
joseph.sa...@gmail.com
Way to go! Soon you'll be building your own wheels!
Dish cannot be changed by one spoke. It is regulated by the average
tension difference between sides. That means the drive side is usually
a lot tighter to pull the rim that way, instead of having it centered
between the flanges, as on a front wheel (which has even tension, and
thus no dish.)
The cassette tool is a good one to have.
Joseph
joseph.sa...@gmail.com
PS: If you are breaking non-drive side spokes, this indicates without a
doubt that they are crap spokes. (based on info from your previous
posts, that you don't weigh 400lbs,etc)
Joseph
jobst....@stanfordalumni.org
> If you are breaking non-drive side spokes, this indicates without a
> doubt that they are crap spokes. (based on info from your previous
> posts, that you don't weigh 400lbs,etc)
Even the best spokes fail if they are not formed to the hub and stress
relieved. Don't push it off on the spoke manufacturer when it's the
builder who needs to take measures to make the wheel durable.
Jobst Brandt
dgk
Stress relief is just going around the wheel sort of pinching the
spokes?
joseph.sa...@gmail.com
Perhaps, but I was making some assumptions based on previous posts. As
I recall this is an inexpensive machine built wheel as spec'd for a
$350 bike that doesn't see particularly heavy use. I'll bet they are
cheap spokes AND they are not formed to the hub nor stress-relieved.
Joseph
jobst....@stanfordalumni.org
>>> If you are breaking non-drive side spokes, this indicates without
>>> a doubt that they are crap spokes. (based on info from your
>>> previous posts, that you don't weigh 400lbs,etc)
>> Even the best spokes fail if they are not formed to the hub and
>> stress relieved. Don't push it off on the spoke manufacturer when
>> it's the builder who needs to take measures to make the wheel
>> durable.
> Stress relief is just going around the wheel sort of pinching the
> spokes?
There's more to it than that, but yes. A better method of stress
relief is to stand the wheel on its axle and press down on the rim
with hands diametrically opposite, once between each pair of spokes.
However, first the outbound spokes must be manually bent to lie flush
against the flange. Then by grasping pairs of spokes on opposite
sides of the wheel and squeezing them together will make sure that
your wheel is not too tight.
Jobst Brandt
carl...@comcast.net
Dear DGK,
Forgive me, but your innocent response is too good not to cross-post to
rec.bicycles.tech.
While pinching spoke pairs together probably helps to seat the spokes
in the hub and the nipples in the rim, tests showed no further residual
stresses being relieved after ordinary spoke tension, even when tension
was much higher than the typical 60-lb tension increase that other
testing shows can be achieved by pinching.
I pinched spokes together on various wheels with known forces and
measured the tension changes. Despite the impressive bending, the spoke
tension rose only about 55~65 for a 60 lb pinch. (The bending was not
due to the spokes being stretched by tremendous tension increases, but
to the slack gained when the rims bent into faint N or Z shapes.)
I bent new stainless steel spokes into a near-U, tensioned them in a
bench-vise rig up to 394 lbs, and measured how far the spoke ends moved
when the residual stresses in the U-bends were relieved by heating to
glowing orange with a propane torch. As would be expected, the greatest
movement (most residual stress exposed) occurred when the bent spoke
had not been tensioned at all. Modest tension quickly reduced the
amount that the spoke ends would move when the bend was heated,
suggesting that some residual stresses had been relieved by the initial
tension. By the time that tension reached the lowest level of an
ordinary bicycle wheel, scarcely any effect was seen when the bends
were heated.
The most likely explanation for an occasional spoke breaking is
variation in the spoke material. The bending and tensioning and so
forth are quite regular. If pinching the spokes were solving some
residual stress problem, the same problem would be causing all the
other spokes to fail.
There's no question that improvements in spoke material have reduced
spoke failure dramatically. Spokes are still being bent and formed the
same way, but ten years after his book's first edition, Jobst
high-lighted the improvement in spokes in his 3rd edition:
"It appears that the better spokes now available would have made the
discovery of many of the concepts of this book more difficult for lack
of failure data. I am grateful in retrospect for the poor durability of
earlier spokes. They operated so near their limits that durability was
significantly altered by the techniques that I have outlined."
--Jobst Brandt, "The Bicycle Wheel," 3rd Edition, 1993, p.124
So pinch 'em and expect improved seating, but don't expect miracles in
residual stress relief. That's achieved just by raising the tension to
normal levels.
Cheers,
Carl Fogel
jobst....@stanfordalumni.org
>>> If you are breaking non-drive side spokes, this indicates without
>>> a doubt that they are crap spokes. (based on info from your
>>> previous posts, that you don't weigh 400lbs,etc)
>> Even the best spokes fail if they are not formed to the hub and
>> stress relieved. Don't push it off on the spoke manufacturer when
>> it's the builder who needs to take measures to make the wheel
>> durable.
> Stress relief is just going around the wheel sort of pinching the
> spokes?
There's more to it than that, but yes. A better method of stress
Johnny Sunset aka Tom Sherman
Dear Jobst,
What is your opinion of this book:
<http://sheldonbrown.com/harris/books.html#brandt>?
Thank you,
J. Sunset
Werehatrack
>The most likely explanation for an occasional spoke breaking is
>variation in the spoke material. The bending and tensioning and so
>forth are quite regular. If pinching the spokes were solving some
>residual stress problem, the same problem would be causing all the
>other spokes to fail.
No idea if this is relevant or not, but if the spokes in question are
some of those made from the Korean steel which has now been
acknowledged to have been below spec on strength and flaws, then the
breakage is most likely due to that.
>There's no question that improvements in spoke material have reduced
>spoke failure dramatically. Spokes are still being bent and formed the
>same way, but ten years after his book's first edition, Jobst
>high-lighted the improvement in spokes in his 3rd edition:
>
>"It appears that the better spokes now available would have made the
>discovery of many of the concepts of this book more difficult for lack
>of failure data. I am grateful in retrospect for the poor durability of
>earlier spokes. They operated so near their limits that durability was
>significantly altered by the techniques that I have outlined."
>
>--Jobst Brandt, "The Bicycle Wheel," 3rd Edition, 1993, p.124
And the speed with which spoke failures became common again when just
one prolific mill was producing substandard wire, was quite
demonstrative of the accuracy of Jobst's statements.
>So pinch 'em and expect improved seating, but don't expect miracles in
>residual stress relief. That's achieved just by raising the tension to
>normal levels.
OTOH, it couldn't hurt, either, and once in a while it'll be just
enough to reveal the one ready-to-fail spoke lurking in the bunch.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.
jim beam
> someone writes:
>
>>>> If you are breaking non-drive side spokes, this indicates without
>>>> a doubt that they are crap spokes. (based on info from your
>>>> previous posts, that you don't weigh 400lbs,etc)
>
>>> Even the best spokes fail if they are not formed to the hub and
>>> stress relieved. Don't push it off on the spoke manufacturer when
>>> it's the builder who needs to take measures to make the wheel
>>> durable.
>
>> Stress relief is just going around the wheel sort of pinching the
>> spokes?
>
> There's more to it than that, but yes. A better method of stress
> relief is to stand the wheel on its axle and press down on the rim
> with hands diametrically opposite, once between each pair of spokes.
>
> However, first the outbound spokes must be manually bent to lie flush
> against the flange.
doing that before raising spokes to full "stress relief" tension will
ensure the angle to which they will be bent is too acute. the hub holes
will deform [seat] under tension, and it is /that/ angle to which the
spokes must be formed, if any, *NOT* the angle /before/ the hub holes
are seated. but given that the hub flanges are canted and that the
angle which the spoke manufacturer already provides is already
appropriate, there's no point in this exercise in the first place.
spoke quality is item #1 in the fight against fatigue, not witchcraft.
dvt
> but given that the hub flanges are canted and that the
> angle which the spoke manufacturer already provides is already
> appropriate, there's no point in this exercise in the first place.
You never answered this question the first time, so let's try again...
How are the hub flanges canted optimally for all the variations of
wheels? In bound vs. out bound, crossing pattern, and rim size all
affect the angle in question. I don't see hubs marketed for each
variation, and I don't see holes labeled for inbound and outbound
spokes. Do small wheels (think recumbent) usually use the same hubs as
diamond frame bikes? If so, do they have a much higher incidence of
spoke breakage?
--
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)
dgk
>
>dgk wrote:
>> On 04 Dec 2006 20:55:44 GMT, jobst....@stanfordalumni.org wrote:
>>
>> >Joseph Santaniello writes:
>> >
>> >> If you are breaking non-drive side spokes, this indicates without a
>> >> doubt that they are crap spokes. (based on info from your previous
>> >> posts, that you don't weigh 400lbs,etc)
>> >
>> >Even the best spokes fail if they are not formed to the hub and stress
>> >relieved. Don't push it off on the spoke manufacturer when it's the
>> >builder who needs to take measures to make the wheel durable.
>> >
>> >Jobst Brandt
>>
>> Stress relief is just going around the wheel sort of pinching the
>> spokes?
>
>Dear DGK,
>
>Forgive me, but your innocent response is too good not to cross-post to
>rec.bicycles.tech.
>
THANKS! I can't recall the last time someone called anything about me
"innocent". It's almost like being carded.
dgk
Recall correct. Except that, being a hybrid, the rear wheel does get a
lot of weight, Especially since the travel bag sits over it.
joseph.sa...@gmail.com
They weight distribution difference from the hybrid configuration is
minimal. The travel bag could make a difference, but unless you are
carrying around several dehydrated grandfather clocks, your total
weight is still well within range of what should not be a problem for
36 spoke wheels.
Joseph
dgk
Good. I just posted about a Shimano wheel that I'm thinking about
getting. It might be overkill but piece by piece I'm turning my Trek
7100 into a 7300. I broken spoke, causing me to limp home with a
detached brake, is just really annoying.
joseph.sa...@gmail.com
That $120 + shipping wheel looks pretty good, but I think it's maybe
not money well spent. Your hub and rim are probably fine, so replacing
them won't get you any further. I'd get $26 worth of DT spokes from
Performance and swap them out myself. Do them one-by-one and it'll work
out fine. And pretend someone is paying you $100 to do it!
Joseph
dgk
Ah, but it's 20% off! Who can resist that bargin? Plus, it would take
me a lot of time to replace each spoke and true it after each one
since I dare not wait until the end to true it.
Besides, it is the holiday season.
I'm more worried that I may run into a problem because of the spacer
requirement for my bike.
joseph.sa...@gmail.com
The spacer will work fine. But I'd still go for replacing the spokes.
the LBS (even an expensive Manhattan one!) could replace them for less
than that wheel and one would hope that it would be built well, at
least as well and probably much better than the Performance wheel.
Joseph
Johnny Sunset
dvt wrote:
> jim beam wrote:
> > but given that the hub flanges are canted and that the
> > angle which the spoke manufacturer already provides is already
> > appropriate, there's no point in this exercise in the first place.
>
> You never answered this question the first time, so let's try again...
> How are the hub flanges canted optimally for all the variations of
> wheels? In bound vs. out bound, crossing pattern, and rim size all
> affect the angle in question. I don't see hubs marketed for each
> variation, and I don't see holes labeled for inbound and outbound
> spokes. Do small wheels (think recumbent) usually use the same hubs as
> diamond frame bikes?
99+% of recumbents use the same hubs [1], if for no other reason than
cost and availability.
> If so, do they have a much higher incidence of spoke breakage?
No. Typically, smaller wheels are laced 2X or even 1X to avoid large
angles at the rim. In addition, 32 and 36 spoke wheels are common,
which means more spokes per unit length of rim than larger wheels. And
whatever lateral forces the wheels do see are smaller due to shorter
moment arm from contact patch to hub.
[1] I happen to have several recumbents that use OEM custom Phil Wood
hubs, but those are the exception to the rule.
--
Tom Sherman - Post Free or Die!
jim beam
> jim beam wrote:
>> but given that the hub flanges are canted and that the angle which the
>> spoke manufacturer already provides is already appropriate, there's no
>> point in this exercise in the first place.
>
> You never answered this question the first time, so let's try again...
dave, some threads get too long and windy. if you want to /ensure/ i
read a question that's somehow important, post a new thread. and make
sure i'm not on vacation, traveling, otherwise busy or disinterested.
> How are the hub flanges canted optimally for all the variations of
> wheels?
they're not. they're optimized for the commonest configuration 32/36,
3x. road hubs for road rims, mtb hubs for 26" rims, etc. roughly 3°
for drive, 6° for non-drive.
> In bound vs. out bound, crossing pattern, and rim size all
> affect the angle in question. I don't see hubs marketed for each
> variation, and I don't see holes labeled for inbound and outbound
> spokes. Do small wheels (think recumbent) usually use the same hubs as
> diamond frame bikes? If so, do they have a much higher incidence of
> spoke breakage?
>
if you want to demonstrate something dave, do the math for the spoke
angle given that a hub hole may be larger diameter than the spoke and
seated in a flange of given thickness. then compare that to the stock
spoke angle of ~95°.
jta...@nospam.hfx.andara.com
<spamv...@bad.example.net> wrote:
>> In bound vs. out bound, crossing pattern, and rim size all
>> affect the angle in question. I don't see hubs marketed for each
>> variation, and I don't see holes labeled for inbound and outbound
>> spokes. Do small wheels (think recumbent) usually use the same hubs as
>> diamond frame bikes? If so, do they have a much higher incidence of
>> spoke breakage?
>>
>
>if you want to demonstrate something dave, do the math for the spoke
>angle given that a hub hole may be larger diameter than the spoke and
>seated in a flange of given thickness. then compare that to the stock
>spoke angle of ~95°.
I think I saw those calculations a while ago - it was in a book called
"The Bicycle Wheel", I think.
Johnny Sunset
LOL ;-)
dvt
> dvt wrote:
>> jim beam wrote:
>>> but given that the hub flanges are canted and that the angle which
>>> the spoke manufacturer already provides is already appropriate,
>>> there's no point in this exercise in the first place.
>> You never answered this question the first time, so let's try again...
> dave, some threads get too long and windy. if you want to /ensure/ i
> read a question that's somehow important, post a new thread. and make
> sure i'm not on vacation, traveling, otherwise busy or disinterested.
Nice try, jim. Here's the record:
<http://groups.google.com/group/rec.bicycles.tech/browse_frm/thread/1c072f5d8b7c8892/83a78e954c0f932d>
Scroll down to messages 103-110. You responded to that exact subthread,
so I know you were reading it. But you failed to answer the question.
>> In bound vs. out bound, crossing pattern, and rim size all affect the
>> angle in question. I don't see hubs marketed for each variation, and I
>> don't see holes labeled for inbound and outbound spokes. Do small
>> wheels (think recumbent) usually use the same hubs as diamond frame
>> bikes? If so, do they have a much higher incidence of spoke breakage?
> if you want to demonstrate something dave, do the math for the spoke
> angle given that a hub hole may be larger diameter than the spoke and
> seated in a flange of given thickness. then compare that to the stock
> spoke angle of ~95°.
You made the claim. It's your job to prove it. Here's the claim you
made, in case you've forgotten:
"the spoke elbow comes pre-formed with the best resultant angle and the
hub flange is canted and drilled also to give the best resultant angle."
You made no reservations about wheel size, lacing pattern, or any of the
other things you tried to add in later when questioned. And what about
dished wheels? Or rims with offset spoke beds?
I'm looking forward to your response.
carl...@comcast.net
Dear J.,
Here's Jobst's diagram in "The Bicycle Wheel," for anyone curious
about specifics, as opposed to the rhetorical questions and
why-don't-you-look-it-up so common on RBT:
http://i12.tinypic.com/2dako69.jpg
Jobst's diagram shows spoke angles from hub to rim of 7.3 and 3.5
degrees.
So a slightly widened 95-degree elbow angle is reasonable for inner
spokes that may be at 97.3~93.5 degrees.
(Various front and rear hub widths probably don't change the angles
much for 700c cross-3 wheels. Spoke elbows on tiny wheels for Moultons
and recumbents may suffer from the orthopedic problems that afflict
many dwarves, but small rims usually make very strong wheels.)
Jobst recommends bending outer spokes enough to lie flat on the hub
flange (and bending all spokes enough at the rim to "correct the spoke
line.")
Sapim disagrees. Here's their FAQ comment on 95 degree elbow angles
and whether spokes should be bent ("forced") to change the angle:
"If material is forced while lacing the hub, the spokes can be pulled
over causing material weakness."
"The original bend angle of 95° should remain intact."
http://www.sapim.be/index.php?st=fa
Elsewhere in "The Bicycle Wheel," Jobst mentions that steel spokes
will bed into aluminum hubs, which have largely replaced the steel
hubs that were popular when his first edition came out:
"When spokes are properly tensioned the aluminum flange material on
which they bear is usually under enough stress to conform to the
spokes." --p. 59, "The Bicycle Wheel," 3rd edition, Jobst Brandt
There's a good drawing of a "Spoke Seating in the Flange" next to the
text quoted above (and oodles more interesting stuff, such as
correcting the spoke line), but anyone interested will need to get
their own copy . . .
http://sheldonbrown.com/harris/books.html#brandt
Cheers,
Carl Fogel
dgk
>
>The spacer will work fine. But I'd still go for replacing the spokes.
>the LBS (even an expensive Manhattan one!) could replace them for less
>than that wheel and one would hope that it would be built well, at
>least as well and probably much better than the Performance wheel.
>
>Joseph
I spoke to the LBS. They said that the wheel I have doesn't really pay
to put good spokes in. It isn't a terrible wheel but putting good
spokes in it would cost more than the thing is worth. They suggested
buying a new wheel, $60 - $75 range. I figured that I'd get the
Shimano one instead. I know that comes with the better spokes. The LBS
gets plenty of other business from me.
Really, the other option was to buy a new bike, say around $500. I'd
do it but I just don't see how I can keep it from getting stolen.
Jasper Janssen
wrote:
>doing that before raising spokes to full "stress relief" tension will
>ensure the angle to which they will be bent is too acute. the hub holes
>will deform [seat] under tension, and it is /that/ angle to which the
>spokes must be formed, if any, *NOT* the angle /before/ the hub holes
>are seated. but given that the hub flanges are canted and that the
>angle which the spoke manufacturer already provides is already
>appropriate, there's no point in this exercise in the first place.
>spoke quality is item #1 in the fight against fatigue, not witchcraft.
Spoke heads are bent at about a 95 degree angle, which is just about
appropriate for the inside spokes, but the outside spokes need to be bent
a bit further than 90 degrees. The fact that the spoke head angle isn't 90
degrees and that the flange is not at the same place in the dimension
along the axle as the rim is means that there is always asymmetry between
inside and outside spokes and therefore they are *not* already perfectly
formed.
Jasper
jobst....@stanfordalumni.org
I agree and in addition, a spoke elbow that is, perhaps, 85° and needs
to be 95° cannot be opened to that angle once in place. That is the
reason for not reusing spokes that have been taken out of a wheel.
The inbound and outbound spokes being difficult to recognize and the
ones with acute angles may not fit the new wheel.
Jobst Brandt
jim beam
they're not "perfectly" formed, but they're good enough given that the
hub flanges are canted and that the hub holes deform! and don't forget
that the spokes interleave making the exit angle of the spoke about the
same for both inbound and outbound spokes at full tension - unlike when
untensioned, the time at with "correcting the spoke like" is
[prematurely] advocated.
jim beam
> On Wed, 06 Dec 2006 11:36:01 GMT, jta...@NOSPAM.hfx.andara.com wrote:
>
>> On Tue, 05 Dec 2006 20:23:10 -0800, jim beam
>> <spamv...@bad.example.net> wrote:
>>
>>
>>>> In bound vs. out bound, crossing pattern, and rim size all
>>>> affect the angle in question. I don't see hubs marketed for each
>>>> variation, and I don't see holes labeled for inbound and outbound
>>>> spokes. Do small wheels (think recumbent) usually use the same hubs as
>>>> diamond frame bikes? If so, do they have a much higher incidence of
>>>> spoke breakage?
>>>>
>>> if you want to demonstrate something dave, do the math for the spoke
>>> angle given that a hub hole may be larger diameter than the spoke and
>>> seated in a flange of given thickness. then compare that to the stock
>>> spoke angle of ~95�.
>>
>> I think I saw those calculations a while ago - it was in a book called
>> "The Bicycle Wheel", I think.
>
> Dear J.,
>
> Here's Jobst's diagram in "The Bicycle Wheel," for anyone curious
> about specifics, as opposed to the rhetorical questions and
> why-don't-you-look-it-up so common on RBT:
>
> http://i12.tinypic.com/2dako69.jpg
thanks carl, but that's not what i was trying to describe - i was
talking about the angle that results from having a 2.0mm spoke in a
2.4mm hub hole for a 3.4mm flange thickness.
>
> Jobst's diagram shows spoke angles from hub to rim of 7.3 and 3.5
> degrees.
which is how the hub is canted.
>
> So a slightly widened 95-degree elbow angle is reasonable for inner
> spokes that may be at 97.3~93.5 degrees.
if the hub flange is canted, the spoke angle is from the point raised
for the spoke not sitting square in the larger hub hole, not from the
angle associated with flange spacing.
>
> (Various front and rear hub widths probably don't change the angles
> much for 700c cross-3 wheels. Spoke elbows on tiny wheels for Moultons
> and recumbents may suffer from the orthopedic problems that afflict
> many dwarves, but small rims usually make very strong wheels.)
>
> Jobst recommends bending outer spokes enough to lie flat on the hub
> flange (and bending all spokes enough at the rim to "correct the spoke
> line.")
>
> Sapim disagrees. Here's their FAQ comment on 95 degree elbow angles
> and whether spokes should be bent ("forced") to change the angle:
>
> "If material is forced while lacing the hub, the spokes can be pulled
> over causing material weakness."
>
> "The original bend angle of 95� should remain intact."
>
> http://www.sapim.be/index.php?st=fa
>
> Elsewhere in "The Bicycle Wheel," Jobst mentions that steel spokes
> will bed into aluminum hubs, which have largely replaced the steel
> hubs that were popular when his first edition came out:
>
> "When spokes are properly tensioned the aluminum flange material on
> which they bear is usually under enough stress to conform to the
> spokes." --p. 59, "The Bicycle Wheel," 3rd edition, Jobst Brandt
they do indeed.
http://www.flickr.com/photos/38636024@N00/104463818/
jim beam
eh? so which side of the fence do you sit here jobst? if the inbound
and outbound spokes can't be told apart after they've been used, there's
no necessity to "correct the spoke line", right?
jim beam
> jim beam wrote:
>> dvt wrote:
>>> jim beam wrote:
>>>> but given that the hub flanges are canted and that the angle which
>>>> the spoke manufacturer already provides is already appropriate,
>>>> there's no point in this exercise in the first place.
>
>>> You never answered this question the first time, so let's try again...
>
>> dave, some threads get too long and windy. if you want to /ensure/ i
>> read a question that's somehow important, post a new thread. and make
>> sure i'm not on vacation, traveling, otherwise busy or disinterested.
>
> Nice try, jim. Here's the record:
>
> <http://groups.google.com/group/rec.bicycles.tech/browse_frm/thread/1c072f5d8b7c8892/83a78e954c0f932d>
is this the 'unanswered' question?
"I've been watching this thread, hoping that I wasn't the only one with
this question. How do you "cant and drill" a hole in the hub flange so
that both inbound *and* outbound spokes are "optimized?" If the hole was
so canted, would that mean that the hubs should not be deformed during
the build?"
if so, i'd have thought the answers obvious. maybe that's why i didn't
bother answering.
>
>
> Scroll down to messages 103-110. You responded to that exact subthread,
> so I know you were reading it. But you failed to answer the question.
>
>>> In bound vs. out bound, crossing pattern, and rim size all affect the
>>> angle in question. I don't see hubs marketed for each variation, and
>>> I don't see holes labeled for inbound and outbound spokes. Do small
>>> wheels (think recumbent) usually use the same hubs as diamond frame
>>> bikes? If so, do they have a much higher incidence of spoke breakage?
>
>> if you want to demonstrate something dave, do the math for the spoke
>> angle given that a hub hole may be larger diameter than the spoke and
>> seated in a flange of given thickness. then compare that to the stock
>> spoke angle of ~95°.
>
> You made the claim. It's your job to prove it. Here's the claim you
> made, in case you've forgotten:
>
> "the spoke elbow comes pre-formed with the best resultant angle and the
> hub flange is canted and drilled also to give the best resultant angle."
>
> You made no reservations about wheel size, lacing pattern, or any of the
> other things you tried to add in later when questioned. And what about
> dished wheels? Or rims with offset spoke beds?
>
> I'm looking forward to your response.
>
unless you want a full custom hub, the economics don't support
accommodating non-standard configurations.
two hub pics for consideration:
http://www.flickr.com/photos/38636024@N00/316202144/
http://www.flickr.com/photos/38636024@N00/316202143/
for the cynics, i didn't happen to have any 2.4mm rod about for the hub
hole pic, but if you don't believe the hub holes are perpendicular to
the flange, do this experiment yourself.
for dave, no, there's nothing sinister about this hub being black or
large flange. it just happened to be a virgin hub at the top of my
parts box.
jim beam
> On Mon, 04 Dec 2006 19:33:43 -0800, jim beam <spamv...@bad.example.net>
> wrote:
>
>> doing that before raising spokes to full "stress relief" tension will
>> ensure the angle to which they will be bent is too acute. the hub holes
>> will deform [seat] under tension, and it is /that/ angle to which the
>> spokes must be formed, if any, *NOT* the angle /before/ the hub holes
>> are seated. but given that the hub flanges are canted and that the
>> angle which the spoke manufacturer already provides is already
>> appropriate, there's no point in this exercise in the first place.
>> spoke quality is item #1 in the fight against fatigue, not witchcraft.
>
> Spoke heads are bent at about a 95 degree angle, which is just about
> appropriate for the inside spokes, but the outside spokes need to be bent
> a bit further than 90 degrees.
no they don't - for this reason:
http://www.flickr.com/photos/38636024@N00/104463818/
you also forget the interleaving of the spokes averaging the angles on
both sides of the flange.
> The fact that the spoke head angle isn't 90
> degrees and that the flange is not at the same place in the dimension
> along the axle as the rim is means that there is always asymmetry between
> inside and outside spokes and therefore they are *not* already perfectly
> formed.
no. see above.
carl...@comcast.net
Dear Jim,
The canting of the outside hub flanges is indeed obvious, once I
looked carefully.
Alas, I can't take very good pictures, but here's a used 1998 Shimano
7-speed cassette hub that shows the canting that you're talking about.
The inside of each flange is as dead-on to the camera as I could
manage, and is 90-degrees to the axle.
The outside of each flange angles noticeably inward, toward a rim.
You can see the dirty spoke holes on the outside of each flange
because of the canting.
An on-screen protractor shows that the outside of the drive-side
flange is angled about 10 degrees inward toward a rim, while the
outside of the non-drive-side flange is angled inward a bit less,
about 7~8 degrees.
In Explorer click on the lower right to enlarge images.
Drive-side hub flange, outside canted inward about 10 degrees:
http://i12.tinypic.com/49fvs3t.jpg
Non-drive-side hub flange, outside canted inward about 8 degrees:
http://i10.tinypic.com/43ykwmx.jpg
Onscreen protractor and ruler:
http://www.markus-bader.de/MB-Ruler/
Cheers,
Carl Fogel
jta...@nospam.hfx.andara.com
<spamv...@bad.example.net> wrote:
>>
>> I agree and in addition, a spoke elbow that is, perhaps, 85° and needs
>> to be 95° cannot be opened to that angle once in place. That is the
>> reason for not reusing spokes that have been taken out of a wheel.
>> The inbound and outbound spokes being difficult to recognize and the
>> ones with acute angles may not fit the new wheel.
>
>eh? so which side of the fence do you sit here jobst? if the inbound
>and outbound spokes can't be told apart after they've been used, there's
>no necessity to "correct the spoke line", right?
How do you get from "difficult" to "can't be told"?
Or are they the same, for you?
Peter Cole
> unlike when
> untensioned, the time at with "correcting the spoke like" is
> [prematurely] advocated.
Who advocates correcting the spoke line on an untensioned wheel?
Peter Cole
>
> The canting of the outside hub flanges is indeed obvious, once I
> looked carefully.
>
>
"Most hubs have their flanges angled inward slightly to reduce the
difference between the elbow bends of inbound and outbound spokes."
The Bicycle Wheel, third edition, page 96.
Peter Cole
> Jasper Janssen wrote:
>> Spoke heads are bent at about a 95 degree angle, which is just about
>> appropriate for the inside spokes, but the outside spokes need to be bent
>> a bit further than 90 degrees.
>
> no they don't - for this reason:
> http://www.flickr.com/photos/38636024@N00/104463818/
> you also forget the interleaving of the spokes averaging the angles on
> both sides of the flange.
>
>> The fact that the spoke head angle isn't 90
>> degrees and that the flange is not at the same place in the dimension
>> along the axle as the rim is means that there is always asymmetry between
>> inside and outside spokes and therefore they are *not* already perfectly
>> formed.
>
> no. see above.
"If the spokes have a good snug fit at the flange, the outbound spokes
may have a slight bow where they emerge from the spoke holes. Push these
spokes down against the flange near their elbows with your thumb so that
they make contact against the flange. Inbound spokes usually lie flat
and need no correction. These adjustments require skills that come with
practice."
"The Bicycle Wheel", third edition, page 96.
The context is for a tensioned wheel.
I can't see what's so controversial about carefully taking the bow out
of a tensioned wheel if one exists. Ditto for bows at the nipples.
dvt
> dvt wrote:
>
> is this the 'unanswered' question?
> 'I've been watching this thread, hoping that I wasn't the only one with
> this question. How do you "cant and drill" a hole in the hub flange so
> that both inbound *and* outbound spokes are "optimized?"'
I snipped the last bit, leaving the specific question.
> if you don't believe the hub holes are perpendicular to
> the flange, do this experiment yourself.
I never doubted that hub flanges were canted. I *don't* understand why
you consider that cant optimal when there are so many different ways to
lace a wheel.
Sheldon Brown
Peter Cole wrote:
> I can't see what's so controversial about carefully taking the bow out
> of a tensioned wheel if one exists.
I don't see it as controversial, but is much _easier_ to do it on an
un-tensioned wheel.
When you try to bend any piece of metal to a particular shape, you must
bend it past the desired position, allowing the elasticity of the metal
to bring it back to the desired shape once the force is removed.
Since you need to bend the spoke temporarily beyond "straight" you will
be fighting the spoke tension if you try to do this on a fully
tensioned wheel. Maybe your thumbs are strong enough for this, but
mine aren't.
Also, when the spoke are un-tensioned, it is easier to see when the
alignment has been optimized.
Sheldon "Sequence" Brown
+---------------------------------------------------+
| If you oppose making marriage legally available |
| to all adults, you are promoting promiscuity. |
+---------------------------------------------------+
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com
Johnny Sunset aka Tom Sherman
Jobst Brandt wrote:
> ...
> I agree and in addition, a spoke elbow that is, perhaps, 85° and needs
Work hardening, "fulcrum" in the wrong place, or a combination of the
two?
jim beam
> jim beam wrote:
>> dvt wrote:
>
>>
>> is this the 'unanswered' question?
>> 'I've been watching this thread, hoping that I wasn't the only one with
>> this question. How do you "cant and drill" a hole in the hub flange so
>> that both inbound *and* outbound spokes are "optimized?"'
>
> I snipped the last bit, leaving the specific question.
>
>> if you don't believe the hub holes are perpendicular to the flange, do
>> this experiment yourself.
>
> I never doubted that hub flanges were canted. I *don't* understand why
> you consider that cant optimal when there are so many different ways to
> lace a wheel.
>
jim beam
> Peter Cole wrote:
>
>> I can't see what's so controversial about carefully taking the bow out
>> of a tensioned wheel if one exists.
>
> I don't see it as controversial, but is much _easier_ to do it on an
> un-tensioned wheel.
but doing it when the hub hole is not yet conformed to the spoke means
that it's being bent too much.
jobst....@stanfordalumni.org
>> ... I agree and in addition, a spoke elbow that is, perhaps, 85°
>> and needs to be 95° cannot be opened to that angle once in
>> place...
> Work hardening, "fulcrum" in the wrong place, or a combination of
> the two?
No fulcrum about which to change the bend. Try it sometime. That is
why the spoke lone must be improved manually, because tension alone
will not change the shape of the elbow.
Spokes do not further work harden in use because that would require
substantial form change while yielding.
Jobst
carl...@comcast.net
Dear Jobst,
"The spoke lone" puzzled me for a moment, so others may wonder, too,
but the explanation is right next to the "o" on the keyboard.
"That is why the spoke line must be improved manually . . ."
It would be nice if someone else would take pity on my moment of
bafflement and confess to drawing a blank, even if only for an
instant.
Cheers,
Carl Fogel
jim beam
> Tom Sherman writes:
>
>>> ... I agree and in addition, a spoke elbow that is, perhaps, 85°
>>> and needs to be 95° cannot be opened to that angle once in
>>> place...
>
>> Work hardening, "fulcrum" in the wrong place, or a combination of
>> the two?
>
> No fulcrum about which to change the bend. Try it sometime.
if there's no fulcrum, what is this "flange" thing about which spokes
are being bent to "correct the spoke line"?
> That is
> why the spoke lone must be improved manually, because tension alone
> will not change the shape of the elbow.
is that not because of hub hole conformance to the spoke???
>
> Spokes do not further work harden in use because that would require
> substantial form change while yielding.
but it's not "substantial". since stainless spoke steels do not strain
age, as demonstrated by the testing in your own book, they most
definitely /do/ work harden from from the slightest deformation while
the spoke line is being "corrected".
Michael Press
<i3shn21utlg92qanr...@4ax.com>,
carl...@comcast.net wrote:
> "That is why the spoke line must be improved manually . . ."
>
> It would be nice if someone else would take pity on my moment of
> bafflement and confess to drawing a blank, even if only for an
> instant.
More than an instant. Almost all Jobst's typographical
errors are a real word. Spell checkers are not what
they used to be. Used to bring me coffee and sit in my
lap.
--
Michael Press
Johnny Sunset
Previous discussions on rec.bicycles.tech have established that most
higher quality spokes (e.g. DT, Sapim, and Wheelsmith) are made from
304 stainless steel.
It is my understanding that the austenitic (FCC) crystalline structure
of 304 is changed to a martensitic crystalline structure that is either
HCP or BCC when cold worked, and that (as expected) the martensite is
harder and less ductile (i.e. work hardened) than the parent austenite.
Is the amount of deformation when installing a new 304 spoke in a wheel
insufficient to significantly work harden the elbow?
jim beam
> Jobst Brandt wrote:
>> Tom Sherman writes:
>>
>>>> ... I agree and in addition, a spoke elbow that is, perhaps, 85�
>>>> and needs to be 95� cannot be opened to that angle once in
>>>> place...
>>> Work hardening, "fulcrum" in the wrong place, or a combination of
>>> the two?
>> No fulcrum about which to change the bend. Try it sometime. That is
>> why the spoke lone must be improved manually, because tension alone
>> will not change the shape of the elbow.
>>
>> Spokes do not further work harden in use because that would require
>> substantial form change while yielding.
>
> Previous discussions on rec.bicycles.tech have established that most
> higher quality spokes (e.g. DT, Sapim, and Wheelsmith) are made from
> 304 stainless steel.
i think that too much of an assumption. sapim describe their material
as "18/8", a broad but common designation which can be included in 304,
but neither d.t. nor wheelsmith say what they use iirc. whatever the
details, a simple magnet test reveals all 3 brands to be different.
sapim is strongly magnetic, wheelsmith very weakly and d.t. in between.
>
> It is my understanding that the austenitic (FCC) crystalline structure
> of 304 is changed to a martensitic crystalline structure that is either
> HCP or BCC when cold worked, and that (as expected) the martensite is
> harder and less ductile (i.e. work hardened) than the parent austenite.
there can indeed be work-induced martensitic transformations, but again,
i'm not comfortable saying that is definitely the case here. 304 is not
commonly designated as a martensitic grade.
http://www.msm.cam.ac.uk/phase-trans/2005/Stainless_steels/stainless.html
>
> Is the amount of deformation when installing a new 304 spoke in a wheel
> insufficient to significantly work harden the elbow?
>
unless it exhibits strain aging, /any/ deformation creates work
hardening. that's why the stress/strain graph *rises* above the yield
point rather than goes sideways.
Pat Lamb
> Tom Sherman writes:
>
>>> ... I agree and in addition, a spoke elbow that is, perhaps, 85°
>>> and needs to be 95° cannot be opened to that angle once in
>>> place...
>
>> Work hardening, "fulcrum" in the wrong place, or a combination of
>> the two?
>
> No fulcrum about which to change the bend. Try it sometime. That is
> why the spoke lone must be improved manually, because tension alone
> will not change the shape of the elbow.
I'm not sure I understand this. Couldn't you slide a big flat-head
screwdriver between the spoke and the flange and bend it back out?
Pat
jobst....@stanfordalumni.org
>>>> ... I agree and in addition, a spoke elbow that is, perhaps, 85°
>>>> and needs to be 95° cannot be opened to that angle once in
>>>> place...
>>> Work hardening, "fulcrum" in the wrong place, or a combination of
>>> the two?
>> No fulcrum about which to change the bend. Try it sometime. That
>> is why the spoke line must be improved manually, because tension
>> alone will not change the shape of the elbow.
> I'm not sure I understand this. Couldn't you slide a big flat-head
> screwdriver between the spoke and the flange and bend it back out?
That doesn't work because the elbow would only rock in its aluminum
bore and change little if any. Besides, there is no gap to insert a
screwdriver. Something thin enough to enter there would be too weak
to bend a spoke.
Jobst Brandt
dvt
On 9 Nov 2006, jim beam wrote:
> the hub holes deform during the build. "correcting the spoke line"
> before this process has occurred is premature and will leave the
> spoke elbow with the wrong resultant angle. the spoke elbow comes
> pre-formed with the best resultant angle and the hub flange is canted
> and drilled also to give the best resultant angle. it may look odd
> when first laced, but when fully tensioned, the net result is
> optimized. i therefore say leave the spoke elbow angle alone - do
> /not/ bend.
On 5 Dec 2006, jim beam wrote:
>> How are the hub flanges canted optimally for all the variations of
>> wheels?
> they're not. they're optimized for the commonest configuration
> 32/36, 3x. road hubs for road rims, mtb hubs for 26" rims, etc.
> roughly 3° for drive, 6° for non-drive.
When building a small wheel, or a wheel that's not 3x, or some other
combination that does not meet your specs, should the user "improve the
spoke line?"
What crossing pattern should be used with <32 spoke hubs?
Johnny Sunset
jim beam wrote:
> Johnny Sunset wrote:
> > Jobst Brandt wrote:
> >> Tom Sherman writes:
> >>
> >>>> and needs to be 95? cannot be opened to that angle once in
> >>>> place...
> >>> Work hardening, "fulcrum" in the wrong place, or a combination of
> >>> the two?
> >> No fulcrum about which to change the bend. Try it sometime. That is
> >> why the spoke lone must be improved manually, because tension alone
> >> will not change the shape of the elbow.
> >>
> >> Spokes do not further work harden in use because that would require
> >> substantial form change while yielding.
> >
> > Previous discussions on rec.bicycles.tech have established that most
> > higher quality spokes (e.g. DT, Sapim, and Wheelsmith) are made from
> > 304 stainless steel.
>
> i think that too much of an assumption. sapim describe their material
> as "18/8", a broad but common designation which can be included in 304,
> but neither d.t. nor wheelsmith say what they use iirc. whatever the
> details, a simple magnet test reveals all 3 brands to be different.
> sapim is strongly magnetic, wheelsmith very weakly and d.t. in between.
>From the Wheelsmith website [1]: "All Wheelsmith spokes are produced
from a specially drawn 304 stainless steel using a variety of cold
forging techniques, some proprietary."
> > It is my understanding that the austenitic (FCC) crystalline structure
> > of 304 is changed to a martensitic crystalline structure that is either
> > HCP or BCC when cold worked, and that (as expected) the martensite is
> > harder and less ductile (i.e. work hardened) than the parent austenite.
>
> there can indeed be work-induced martensitic transformations, but again,
> i'm not comfortable saying that is definitely the case here. 304 is not
> commonly designated as a martensitic grade.
> http://www.msm.cam.ac.uk/phase-trans/2005/Stainless_steels/stainless.html
This is a claim that austenitic 304 will form martensite when
plastically deformed at cold temperatures [2]. Are you differing on
degree of martensitic transformation or suggesting some other mechanism
for work hardening?
> > Is the amount of deformation when installing a new 304 spoke in a wheel
> > insufficient to significantly work harden the elbow?
> >
>
> unless it exhibits strain aging, /any/ deformation creates work
> hardening. that's why the stress/strain graph *rises* above the yield
> point rather than goes sideways.
I am aware of the strain hardening of 304 steel (having run tension
tests on said material to failure), which is why I used the qualifier
"significantly". Would the degree of work hardening of bending the
elbow of a 304 steel spoke to 85° make it impractical to bend back to
95°?
[1] <http://www.wheelsmith.com/index_files/wsspokes.htm>.
[2]
<http://doc.tms.org/ezMerchant/prodtms.nsf/ProductLookupItemID/MMTA-0606-1875/$FILE/MMTA-0606-1875F.pdf?OpenElement>.
jim beam
in extreme circumstances, probably, yes. but otoh, i'd never use a
hub/rim combo that were that deviant. whatever the situation, if it
were my wheel, i'd do the "mavic method" of stress relief first [which
does not require full spoke tension] to be sure the hub holes were fully
conformed before any consideration of bending.
>
> What crossing pattern should be used with <32 spoke hubs?
>
that's a "how long is a piece of string" question - it depends on the
hub size, rim size, etc. personally, i use 3x on 28 spoke, low flange,
road rim. and i never bend spoke elbows.
jim beam
ok, 2 things:
1. yes, i would want to be sure of degree of transformation rather than
making extreme broad-brush claims. the second paper you cite does
indeed discuss transformation at low temperatures [-50 centigrade] which
accords with my understanding that transformation at more normal
temperatures is much more limited.
2. work hardening occurs regardless of any martensitic transformation.
as cited, extent and type of transformation will affect the degree of
hardening - obviously, but straight, stable austenitic stainless steels
significantly work harden as a function of deformation [increasing
dislocation density], as do most simple ductile metals.
>
>>> Is the amount of deformation when installing a new 304 spoke in a wheel
>>> insufficient to significantly work harden the elbow?
>>>
>> unless it exhibits strain aging, /any/ deformation creates work
>> hardening. that's why the stress/strain graph *rises* above the yield
>> point rather than goes sideways.
>
> I am aware of the strain hardening of 304 steel (having run tension
> tests on said material to failure), which is why I used the qualifier
> "significantly". Would the degree of work hardening of bending the
> elbow of a 304 steel spoke to 85� make it impractical to bend back to
> 95�?
if it remains austenitic, it's less likely to be an issue, but
regardless, it depends on the degree of cold work already performed. if
you're dealing with cold drawn wire, the majority of its strength
derives from cold work. it it's near its ductile limit [full hard],
then yes, additional bending could be a problem, but it's unlikely the
wire would be offered in this condition for general manufacture. and
"304" is a /real/ wide spec. since wheelsmith seem to regard the simple
grinding process they use to butt their spokes as "proprietary", i'd not
want to rely too heavily on accuracy of their disclosure of alloy used.
>
> [1] <http://www.wheelsmith.com/index_files/wsspokes.htm>.
> [2]
> <http://doc.tms.org/ezMerchant/prodtms.nsf/ProductLookupItemID/MMTA-0606-1875/$FILE/MMTA-0606-1875F.pdf?OpenElement>.
>
that second paper is a good cite.
dvt
> dvt wrote:
>> When building a small wheel, or a wheel that's not 3x, or some other
>> combination that does not meet your specs, should the user "improve
>> the spoke line?"
>
> in extreme circumstances, probably, yes. but otoh, i'd never use a
> hub/rim combo that were that deviant. whatever the situation, if it
> were my wheel, i'd do the "mavic method" of stress relief first [which
> does not require full spoke tension] to be sure the hub holes were fully
> conformed before any consideration of bending.
So in some cases, the benefits of "improving the spoke line" outweigh
what you you see as the detriments of that method. I'd like to know
where to draw that line.
Gary Young
According to Wheelsmith, their butted spokes have "center sections [that]
are forged rather than cut, ground or drawn ...."
http://www.wheelsmith.com/index_files/spoketech.htm
Jasper Janssen
>> I agree and in addition, a spoke elbow that is, perhaps, 85° and needs
>> to be 95° cannot be opened to that angle once in place. That is the
>> reason for not reusing spokes that have been taken out of a wheel.
>> The inbound and outbound spokes being difficult to recognize and the
>> ones with acute angles may not fit the new wheel.
>
>eh? so which side of the fence do you sit here jobst? if the inbound
>and outbound spokes can't be told apart after they've been used, there's
>no necessity to "correct the spoke line", right?
How good are you at telling 95 from 85 degrees, visually, on something the
radius of a spoke head bend? In an often dark-ish workshop, of course.
Jasper
Jasper Janssen
wrote:
>jobst....@stanfordalumni.org wrote:
>> No fulcrum about which to change the bend. Try it sometime.
>
>if there's no fulcrum, what is this "flange" thing about which spokes
>are being bent to "correct the spoke line"?
There's a fulcrum for bending it further, but not back, or at least not
without getting the nipple end *way* out of the wheel plane, ie, loosened.
And even then it's damn hard, because the geometry means that the force
you apply tends to rotate the spoke head instead of bending it, whereas
with bending further the head tends to lock in place.
This is incredibly obvious if you actually try it.
Jasper
Jasper Janssen
wrote:
>Sheldon Brown wrote:
>> Peter Cole wrote:
>>
>>> I can't see what's so controversial about carefully taking the bow out
>>> of a tensioned wheel if one exists.
>>
>> I don't see it as controversial, but is much _easier_ to do it on an
>> un-tensioned wheel.
>
>but doing it when the hub hole is not yet conformed to the spoke means
>that it's being bent too much.
Does it matter if the hub flange is alu (and what kind) or chromed steel
as in classic and (still) ultracheap hubs?
Jasper
jim beam
yeah, i saw that too. the appearance of the spoke does not accord with
that statement though - it appears to have been ground and polished.
and i believe that the japanese factory from which wheelsmith spokes
originated uses this process also, producing both polished and
unpolished ground spokes, depending on price point. the only way to
know for sure is metallography. perhaps chas can oblige?
jim beam
steel hubs still conform, just not as much. spoke wire is much harder
than the steel in hub flange material.
jim beam
> On Thu, 07 Dec 2006 21:12:34 -0800, jim beam <spamv...@bad.example.net>
> wrote:
>> jobst....@stanfordalumni.org wrote:
>
>>> No fulcrum about which to change the bend. Try it sometime.
>> if there's no fulcrum, what is this "flange" thing about which spokes
>> are being bent to "correct the spoke line"?
>
> There's a fulcrum for bending it further, but not back, or at least not
> without getting the nipple end *way* out of the wheel plane, ie, loosened.
that makes no sense. if the spoke's loose, it's loose and can be bent.
against the hole in the flange in which it's inserted. which acts as
a fulcrum.
> And even then it's damn hard, because the geometry means that the force
> you apply tends to rotate the spoke head instead of bending it, whereas
> with bending further the head tends to lock in place.
>
> This is incredibly obvious if you actually try it.
i think you're confused.
jim beam
well, i can compare used with new, since i have both in the lab. and i
can compare left with right if i'm repairing a wheel. i can also
measure extension of the straight sections if i want to be really
pedantic. it's not impossible. particularly if i can be bothered to
turn the lab lights on.
jim beam
can't find it on the manufacturer web site], you can determine if the
spoke holes are parallel to the hub axle or perpendicular to the flange
and you can calculate the spoke angle with the rim. from there, you can
make a pretty well informed decision on whether to mutilate your spokes
or not.
Gary Young
What is it about the appearance that leads you to say that? Is it the
abruptness of the transition from the center section to the elbow and
threads? Or something about the surface finish?
dvt
Maybe you could, but I couldn't. What is a reasonable cutoff? 1°? 10°?
--
Dave
dvt at psu dot edu
Everyone confesses that exertion which brings out all the powers of body
jim beam
both, if you mean the transition on the butting. there, the section
transition is very smooth and shows no signs of mechanical work. that
implies post-process polishing. with a forging or drawing process, the
surface finish is usually good enough to not warrant further [cost
increasing] work - see d.t., alpina and sapim for examples. regarding
the section profile, not only is it /not/ like any drawing or cold
forging process seen with any other manufacturer, it /is/ identical to
the profile of the japanese ground section spokes i have. mine are
unpolished, so i know for sure how they were made without having to do
metallography.
jim beam
> jim beam wrote:
>> dvt wrote:
>>> jim beam wrote:
>>>> dvt wrote:
>>>>> When building a small wheel, or a wheel that's not 3x, or some
>>>>> other combination that does not meet your specs, should the user
>>>>> "improve the spoke line?"
>
>>>> in extreme circumstances, probably, yes. but otoh, i'd never use a
>>>> hub/rim combo that were that deviant. whatever the situation, if it
>>>> were my wheel, i'd do the "mavic method" of stress relief first
>>>> [which does not require full spoke tension] to be sure the hub holes
>>>> were fully conformed before any consideration of bending.
>
>>> So in some cases, the benefits of "improving the spoke line" outweigh
>>> what you you see as the detriments of that method. I'd like to know
>>> where to draw that line.
>
>> you can do a pretty good guesstimate of the cant on the flange, [if
>> you can't find it on the manufacturer web site], you can determine if
>> the spoke holes are parallel to the hub axle or perpendicular to the
>> flange and you can calculate the spoke angle with the rim. from
>> there, you can make a pretty well informed decision on whether to
>> mutilate your spokes or not.
>
> Maybe you could, but I couldn't.
why not? you're smart enough to progress your position this far. the
rest is simple geometry.
> What is a reasonable cutoff? 1°? 10°?
>
what's the angle in the bent spoke resulting from where crossed spokes
interleave? spokes never fail there, even though the spoke is under
substantial bending strain. that would be a good place from which to
gauge whether permanent deformation is or is not required. but even
then, this debate is entirely academic for regular rim/hub/crossing
combos since that's what spokes are optimized for out of the box.
Gary Young
> dvt wrote:
>> jim beam wrote:
>>> dvt wrote:
>>>> jim beam wrote:
>>>>> but given that the hub flanges are canted and that the angle which
>>>>> the spoke manufacturer already provides is already appropriate,
>>>>> there's no point in this exercise in the first place.
>>
>>>> You never answered this question the first time, so let's try again...
>>
>>> dave, some threads get too long and windy. if you want to /ensure/ i
>>> read a question that's somehow important, post a new thread. and make
>>> sure i'm not on vacation, traveling, otherwise busy or disinterested.
>>
>> Nice try, jim. Here's the record:
>>
>> <http://groups.google.com/group/rec.bicycles.tech/browse_frm/thread/1c072f5d8b7c8892/83a78e954c0f932d>
>
> is this the 'unanswered' question?
> "I've been watching this thread, hoping that I wasn't the only one with
> this question. How do you "cant and drill" a hole in the hub flange so
> that both inbound *and* outbound spokes are "optimized?" If the hole was
> so canted, would that mean that the hubs should not be deformed during
> the build?"
>
> if so, i'd have thought the answers obvious. maybe that's why i didn't
> bother answering.
>
>>
>>
>> Scroll down to messages 103-110. You responded to that exact subthread,
>> so I know you were reading it. But you failed to answer the question.
>>
>>>> In bound vs. out bound, crossing pattern, and rim size all affect the
>>>> angle in question. I don't see hubs marketed for each variation, and
>>>> I don't see holes labeled for inbound and outbound spokes. Do small
>>>> wheels (think recumbent) usually use the same hubs as diamond frame
>>>> bikes? If so, do they have a much higher incidence of spoke breakage?
>>
>>> if you want to demonstrate something dave, do the math for the spoke
>>> angle given that a hub hole may be larger diameter than the spoke and
>>> seated in a flange of given thickness. then compare that to the stock
>>> spoke angle of ~95°.
I think Dave has a point. Elsewhere you've suggested that spoke
manufacturers optimize the elbow angle based on the average configuration
(number of spokes, cross pattern, type of hub, etc.) Even if that's true,
and if spoke manufacturers really go to the extent you suggest to optimize
their spokes, you would expect things to be different on spokes so short
that they can only be used on smaller wheels. Does anyone have such a
spoke (e.g. a spoke for a bmx hub)? Is the angle different? Are the
flanges on bmx hubs canted at a different angle?
>>
>> You made the claim. It's your job to prove it. Here's the claim you
>> made, in case you've forgotten:
>>
>> "the spoke elbow comes pre-formed with the best resultant angle and the
>> hub flange is canted and drilled also to give the best resultant angle."
>>
>> You made no reservations about wheel size, lacing pattern, or any of the
>> other things you tried to add in later when questioned. And what about
>> dished wheels? Or rims with offset spoke beds?
>>
>> I'm looking forward to your response.
>>
> unless you want a full custom hub, the economics don't support
> accommodating non-standard configurations.
>
> two hub pics for consideration:
> http://www.flickr.com/photos/38636024@N00/316202144/
> http://www.flickr.com/photos/38636024@N00/316202143/
>
> for the cynics, i didn't happen to have any 2.4mm rod about for the hub
> hole pic, but if you don't believe the hub holes are perpendicular to
> the flange, do this experiment yourself.
Is there anyone here who's denied that flanges are canted? Even with
canting, when you build a wheel, you can see that the outbound spokes
don't lie as flat against the flange as inbound spokes. If correcting the
spoke line were merely a premature way of bedding in the spokes, wouldn't
the same bulge be evident on both sides of the flange?
While canting may make a gross correction in the spoke line, it
seems to me that canting in itself introduces a new difference in
the lines of inbound and outbound spokes (at least when using a
non-radial, cross-laced pattern). With a canted or funnel-like flange, as
in inbound spoke runs tangentially along the flange, it will be closer to
the edge of the flange than will an outbound spoke. In other words, it
will take a lesser amount of tension to bring the inbound spoke in contact
with the canted-in edge as it leaves the hub. Is there some way to
compensate for that without drilling the inbound spoke holes in a
different way than the outbound ones? Or making separate sets of inbound
and outbound spokes?
I suppose the beveling of the spoke holes could compensate for that to a
certain degree, but it doesn't seem to do so entirely. I just put a spoke
in a unlaced LX front hub, first inbound and then outbound. It takes
noticeably greater force to bring the outbound spoke in contact with the
edge of the flange when the spoke leaves the hole tangentially. It seems
to me that your assertions only make sense when the wheel is laced
radially.
> for dave, no, there's nothing sinister about this hub being black or
> large flange. it just happened to be a virgin hub at the top of my
> parts box.
Gary Young
Please ignore everything below this point. I clearly wasn't thinking
things through very well.
Gary Young
> carl...@comcast.net wrote:
>> On Wed, 06 Dec 2006 11:36:01 GMT, jta...@NOSPAM.hfx.andara.com wrote:
>>
>>> On Tue, 05 Dec 2006 20:23:10 -0800, jim beam
>>> <spamv...@bad.example.net> wrote:
>>>
>>>
>>>>> In bound vs. out bound, crossing pattern, and rim size all
>>>>> affect the angle in question. I don't see hubs marketed for each
>>>>> variation, and I don't see holes labeled for inbound and outbound
>>>>> spokes. Do small wheels (think recumbent) usually use the same hubs as
>>>>> diamond frame bikes? If so, do they have a much higher incidence of
>>>>> spoke breakage?
>>>>>
>>>> if you want to demonstrate something dave, do the math for the spoke
>>>> angle given that a hub hole may be larger diameter than the spoke and
>>>> seated in a flange of given thickness. then compare that to the stock
>>>> spoke angle of ~95�.
>>>
>>> I think I saw those calculations a while ago - it was in a book called
>>> "The Bicycle Wheel", I think.
>>
>> Dear J.,
>>
>> Here's Jobst's diagram in "The Bicycle Wheel," for anyone curious
>> about specifics, as opposed to the rhetorical questions and
>> why-don't-you-look-it-up so common on RBT:
>>
>> http://i12.tinypic.com/2dako69.jpg
>
> thanks carl, but that's not what i was trying to describe - i was
> talking about the angle that results from having a 2.0mm spoke in a
> 2.4mm hub hole for a 3.4mm flange thickness.
>
>>
>> Jobst's diagram shows spoke angles from hub to rim of 7.3 and 3.5
>> degrees.
>
> which is how the hub is canted.
>
>>
>> So a slightly widened 95-degree elbow angle is reasonable for inner
>> spokes that may be at 97.3~93.5 degrees.
>
> if the hub flange is canted, the spoke angle is from the point raised
> for the spoke not sitting square in the larger hub hole, not from the
> angle associated with flange spacing.
I'm not sure what this means. Did you mean to say "sitting square" instead
of "not sitting square"? If it didn't matter whether the spoke was sitting
square, what would be the relevance of canting?
>
>>
>> (Various front and rear hub widths probably don't change the angles
>> much for 700c cross-3 wheels. Spoke elbows on tiny wheels for Moultons
>> and recumbents may suffer from the orthopedic problems that afflict
>> many dwarves, but small rims usually make very strong wheels.)
>>
>> Jobst recommends bending outer spokes enough to lie flat on the hub
>> flange (and bending all spokes enough at the rim to "correct the spoke
>> line.")
>>
>> Sapim disagrees. Here's their FAQ comment on 95 degree elbow angles
>> and whether spokes should be bent ("forced") to change the angle:
>>
>> "If material is forced while lacing the hub, the spokes can be pulled
>> over causing material weakness."
>>
>> "The original bend angle of 95� should remain intact."
>>
>> http://www.sapim.be/index.php?st=fa
>>
>> Elsewhere in "The Bicycle Wheel," Jobst mentions that steel spokes
>> will bed into aluminum hubs, which have largely replaced the steel
>> hubs that were popular when his first edition came out:
>>
>> "When spokes are properly tensioned the aluminum flange material on
>> which they bear is usually under enough stress to conform to the
>> spokes." --p. 59, "The Bicycle Wheel," 3rd edition, Jobst Brandt
>
> they do indeed.
> http://www.flickr.com/photos/38636024@N00/104463818/
>
>>
>> There's a good drawing of a "Spoke Seating in the Flange" next to the
>> text quoted above (and oodles more interesting stuff, such as
>> correcting the spoke line), but anyone interested will need to get
>> their own copy . . .
>>
>> http://sheldonbrown.com/harris/books.html#brandt
>>
>> Cheers,
>>
>> Carl Fogel
Gary Young
> dvt wrote:
>> jim beam wrote:
>>> dvt wrote:
>>>> jim beam wrote:
>>>>> but given that the hub flanges are canted and that the angle which
>>>>> the spoke manufacturer already provides is already appropriate,
>>>>> there's no point in this exercise in the first place.
>>
>>>> You never answered this question the first time, so let's try again...
>>
>>> dave, some threads get too long and windy. if you want to /ensure/ i
>>> read a question that's somehow important, post a new thread. and make
>>> sure i'm not on vacation, traveling, otherwise busy or disinterested.
>>
>> Nice try, jim. Here's the record:
>>
>> <http://groups.google.com/group/rec.bicycles.tech/browse_frm/thread/1c072f5d8b7c8892/83a78e954c0f932d>
>
> is this the 'unanswered' question?
> "I've been watching this thread, hoping that I wasn't the only one with
> this question. How do you "cant and drill" a hole in the hub flange so
> that both inbound *and* outbound spokes are "optimized?" If the hole was
> so canted, would that mean that the hubs should not be deformed during
> the build?"
>
> if so, i'd have thought the answers obvious. maybe that's why i didn't
> bother answering.
>
>>
>>
>> Scroll down to messages 103-110. You responded to that exact subthread,
>> so I know you were reading it. But you failed to answer the question.
>>
>>>> In bound vs. out bound, crossing pattern, and rim size all affect the
>>>> angle in question. I don't see hubs marketed for each variation, and
>>>> I don't see holes labeled for inbound and outbound spokes. Do small
>>>> wheels (think recumbent) usually use the same hubs as diamond frame
>>>> bikes? If so, do they have a much higher incidence of spoke breakage?
>>
>>> if you want to demonstrate something dave, do the math for the spoke
>>> angle given that a hub hole may be larger diameter than the spoke and
>>> seated in a flange of given thickness. then compare that to the stock
>>> spoke angle of ~95°.
>>
>> You made the claim. It's your job to prove it. Here's the claim you
>> made, in case you've forgotten:
>>
>> "the spoke elbow comes pre-formed with the best resultant angle and the
>> hub flange is canted and drilled also to give the best resultant angle."
>>
>> You made no reservations about wheel size, lacing pattern, or any of the
>> other things you tried to add in later when questioned. And what about
>> dished wheels? Or rims with offset spoke beds?
>>
>> I'm looking forward to your response.
>>
> unless you want a full custom hub, the economics don't support
> accommodating non-standard configurations.
>
> two hub pics for consideration:
> http://www.flickr.com/photos/38636024@N00/316202144/
> http://www.flickr.com/photos/38636024@N00/316202143/
>
> for the cynics, i didn't happen to have any 2.4mm rod about for the hub
> hole pic, but if you don't believe the hub holes are perpendicular to
> the flange, do this experiment yourself.
On my XT rear hub, the outer faces of the flanges are canted, but the
inner faces are perpendicular to the hub axle or very nearly so. (The same
may be true of my LX front hub, but I'm much less sure; on the rear
hub, the difference in canting between the inner and outer faces is
unmistakable even when eyeballing it.)
I can't find a picture of an XT hub that shows this, but if you go to the
end of this pdf where there are a series of drawings of hubs, they all
appear to have one canted face and one perpendicular face:
http://www.dtswiss.com/data/files/MAN_EN_41201162428.pdf
If the spoke holes were drilled perpendicular to the canted outer face, I
would expect them to exit the 90-degree inner face at a point further from
the edge of the flange. But both the outer and inner exit points appear to
be the same distance from the edge. That leads me to believe that the
holes are drilled parallel to the hub axle, contrary to the caption on the
second photo you link to above.
There may be a difference in the way the holes are beveled (if that's the
right term) on the inside versus the outside, but not that I can see.
The effect of the difference in canting is that the inbound spokes exit at
what appears to be an optimized angle when their heads are seated squarely
in the canted outer face (that is, when the heads lie flat against the
face, with no lifting of any part of the circumference).
However, when the outbound spokes are seated squarely against the
90-degree inner face, they exit perpendicular to the hub axle, or nearly
so.
I'm not sure why the hub is designed that way. Is there a reason inbound
spokes need to have their seating optimized more than outbound spokes?
Maybe because the elbow angle tends to open up as they are pulled, whereas
the angle of outbound spokes becomes more acute?
In any event, this does seem to fly in the face of your argument that the
spoke/hub combination results in an optimized spoke line.
jim beam
spokes angle towards a rim at say 6 degrees both sides front, and say 6
+ 3 for rears. and that is what hub flanges are canted to. in
addition, hub holes are angled perpendicular to the flange, so they too
are aligned for optimal spoke position.
see:
http://www.flickr.com/photos/38636024@N00/316202144/
http://www.flickr.com/photos/38636024@N00/316202143/
carl...@comcast.net
wrote:
[snip]
Dear Gary,
For what it's worth, Sapim disagrees with the common practice of
"correcting the spoke line."
Here's their FAQ comment on 95 degree elbow angles and whether spokes
should be bent ("forced") to change the angle:
"If material is forced while lacing the hub, the spokes can be pulled
over causing material weakness."
"The original bend angle of 95° should remain intact."
http://www.sapim.be/index.php?st=fa
Cheers,
Carl Fogel
Gary Young
Carl,
Unlike "jim beam," I'm not inclined to take what manufacturers say on
faith. (For that matter, neither is jim beam, it seems -- for instance, he
thinks the center sections of Wheelsmith spokes are ground despite
what they say on their website.)
Furthermore, just on its face this faq doesn't inspire a whole lot of
confidence.
Examples -- sapim recommends that if you break one or two spokes, it's
best to replace all of the spokes (apparently even if the broken spokes
failed because of surface nicks). Better yet, you should replace the
entire hub!
"SAPIM draws wire in such way that no change in molecular material
structure occurs." Seems a little oversweeping to this layman. No change
in structure even when the spoke is butted and the elbow, head and threads
are formed?
"The spoke does not twist much when it is built into a wheel." This
sentence immediately follows the one above. Are they trying to say that
twisting is a function of the molecular structure? I thought it was a
function of the thickness and cross-section of the spoke. Indeed, the faq
goes on to say that elliptical spokes like sapim's CX-Ray are prone to
twisting.
A break at the thread "often occurs as a result of nipple/rim and spoke
mis-alignment." I believe that's the reason that Jobst suggests correcting
the spoke line at the nipple. What does sapim propose be done about
misalignment?
"If spokes are used which are too long, new threads in the nipple will be
made. Under heavy pressure the spoke threads will be stressed too
greatly." Huh? If anything, it would be the nipple making new threads in
the spoke (though wouldn't the nipple be too soft?). Maybe they mean that
as the unthreaded part of the spoke is drawn up, it would destroy the
threads inside the nipple.
carl...@comcast.net
wrote:
Dear Gary,
For what it's worth, posters on RBT often recommend replacing all
spokes if one or two break.
You might also try to pin down some actual explanations for what the
pros and cons are for trying to hand-bend spokes to touch (or come
close to) hub flanges.
But don't hope for any actual testing or statistics.
Cheers,
Carl Fogel
Gary Young
True -- if one has reason to believe that the first couple of spokes
failed because of fatigue without any outward signs of damage. It was my
impression, however, that if the broken spokes were visibly damaged (e.g.,
by the chain jamming between the cassette and spokes), then there's no
reason to replace the spokes that aren't so damaged.
And what about replacing the hub? How do fatigue failures damage the
spoke holes?
>
> You might also try to pin down some actual explanations for what the
> pros and cons are for trying to hand-bend spokes to touch (or come
> close to) hub flanges.
>
> But don't hope for any actual testing or statistics.
Well, I can't say I understand the crux of your disagreement with
Jobst, but I'm trying to work my way through it.
>
> Cheers,
>
> Carl Fogel
doug....@gmail.com
Gary Young wrote:
> Well, I can't say I understand the crux of your disagreement with
> Jobst, but I'm trying to work my way through it.
Carl is an ex-teacher who readily admits that he can't stop grading
folks here. Teachers, of course, choose to spend their career
surrounded by persons who are known to be inferior to themselves; in
other words, in flight from the normal situation in which we are
surrounded by peers at work and will be judged by our deeds and
abilities.
Of course, after decades of anything, it's hard to decompress; hence
his endless attempts to turn r.b.t. readers into his students by
pretending to teach them things which they already know. This bit of
self-deceipt works well but not 100% - much to his dismay, Carl cannot
shut out the realization that Jobst knows more and also is smarter -
and it drives him crazy.
Of course, Jobst is here as a teacher as well. In ten years of reading
I have yet to see him ask a [non-sarcastic or non-rhetorical] question
here. He is not here to learn anything, so why is he here? It can
only be to teach.
At the crux of these recent disagreements that Carl has initiated is
competition for self-perception.
Doug
jim beam
shame he doesn't teach the truth. shame others don't ask questions.
carl...@comcast.net
wrote:
[snip]
>Well, I can't say I understand the crux of your disagreement with
>Jobst, but I'm trying to work my way through it.
[snip]
Dear Gary,
So am I.
For decades, riders usually carried a few spare spokes on tours
because they expected spokes to break. Jobst has mentioned this
practice.
In the early 1980's, Jobst wrote "The Bicycle Wheel" and theorized
that squeezing spoke pairs together would relieve residual stress in
spoke bends.
But ten years later, Jobst wrote
"It appears that the better spokes now available would have made the
discovery of many of the concepts of this book more difficult for lack
of failure data. I am grateful in retrospect for the poor durability
of earlier spokes. They operated so near their limits that durability
was significantly altered by the techniques that I have outlined."
--Jobst Brandt, "The Bicycle Wheel," 3rd Edition, 1993, p.124
I agree that spokes have become much more durable. The evidence is
overwhelming. Few riders bother to carry spare spokes any more, partly
because they have cell phones, but mostly because they don't expect
spokes to break very often. The 36-spoke wheels of the past have been
replaced by wheels with fewer and fewer spokes. Despite the obvious
increase in stress, the spokes last longer.
The spokes are the same length and thickness. The threading and elbow
bends are made in the same way. The only real change has been years of
steady improvement in the quality of the stainless steel wire.
After all, the most likely explanation for an occasional spoke
breaking is variation in the spoke material. The bending and
tensioning and so forth are quite regular. If squeezing spoke pairs
was solving some residual stress problem by raising tension, the same
problem would be causing all the other spokes to fail.
I see Jobst's comment in 1993 that spokes somehow became much more
durable as strong evidence that he was mistaken about how efffective
spoke-sqeezing is.
I also see the lack of variation in results as evidence that
spoke-squeezers are fooling themselves. The repeated claim that
squeezing makes spokes immortal implies that there is no level at
which the spokes are merely given longer lifespans. Everyone seems to
believe that they squeeze just as strongly with their weak hand as
they do with their strong hand, and just as strongly the ninth time as
they do the first time.
I'm unable to find any testing or evidence that supports the claim, as
opposed claims that one step out of many in building a wheel must be
responsible for anecdotal improvements. Again, look at the strange
comment in the 3rd edition. Spokes somehow became so durable in a
decade that Jobst wrote that it would have been hard to "discover" his
theory. I see it as evidence that his theory was wrong.
The lack of testing and measuring to confirm the theory is curious.
Until I started hanging weights from spokes and measuring the tension
changes with a gauge, RBT posters would make good-faith theoretical
calculations that showed huge tension increases.
This illustrates how easily we fool ourselves and how easy it is to
make huge mistakes. I have never doubted the good faith of the last
such calculation that appeared on RBT. A 30 pound side force moved a
spoke a certain distance and bent the spoke at such and so an angle,
which in turn allowed calculations for steel of specifc thickness to
indicate that the spoke tension would rise approximately 150 pounds, a
5 to 1 ratio.
The calculations were correct, but they were based on the assumption
that the rim and the hub would stay in fixed positions.
How could a newsgroup full of wheel-builders assume that the rim would
stay in a fixed position when tension increased 150 pounds?
I'm just as guilty as everyone else who read such posts over the years
without raising an eyebrow. The huge tension increase seemed plausible
and certainly supported Jobst's theory. But I was curious enough to
fiddle around until I finally figured out an obvious way to measure
the tension increase directly.
Oops!
A 30-pound squeeze force on a left and a right spoke-pair will raise
the spoke tension only about 30 pounds, not 150. A 60-pound squeeze
will raise tension only about 55~65 pounds. Higher squeeze forces are
unlikely for most RBT posters. A 100-pound squeeze will leave a faint
permanent bend in a spoke.
The impressive bend angles are due mostly to the slack gained as the
four obviously unbalanced spokes twist the rim into a slight N or Z
shape.
(A weird detail is that spoke tension actually drops as you start to
squeeze. In addition to the rim deforming, the spokes are bent across
other spokes in a cross-3 pattern, and they gain a little initial
slack as they press into the other spoke and straighten a little at
that point. The low-squeeze-force tension drop startled the hell out
of me, but was so consistent that I finally had to admit that it was
real. Noticing the bend where the spokes cross took an embarrassingly
long time.)
All of this could have been figured out and predicted as theory, but
no one was trying to figure out what might be wrong with Jobst's
theory. Most of us set out with an unconscious bias toward working
things out in accordance with the theory.
That's how sensible people can end up calculating a 150-pound spoke
tension increase from 250 to 400 pounds with a 30-pound squeeze force.
A moment's thought would raise the obvious objection. No one ever
complains that he squeezed his spokes so hard that they stretched like
taffy or pulled through the rim. But there are a number of posters who
could squeeze with 100 pounds of force--which the mistaken calculation
predicts would raise the spoke tension over 450 pounds, from 250 to
700. Jobst's tensile tests showed that spokes yield at around 600
pounds.
I tested various wheels and had fun staring at odd details and working
out better and better techniques, but most of my elaborate testing was
a waste of time--the results were immediately obvious.
Anyone who supports one spoke with a ceiling rope, hangs a known
weight on a rope tied to the spoke above it, and measures the tension
with a Park gauge can see how much a 60-pound squeeze force wil raise
the spoke tension. It's not a matter of great precision or poring over
reams of data. It's about like weighing sacks of dog food.
So spoke-squeezing didn't actually raise spoke tension anywhere near
as high as people had been thinking. Their mistake was thinking
instead of testing and letting theory and what they'd like to prove
lead them to where they wanted to go.
The next thing to test was the effect of tension on residual stress.
Everyone agrees that residual stresses exist when a spoke is bent to
form the elbow.
The usual method of relieving residual stress is heating.
Bend a stainless steel spoke 90 degrees, heat the bend to a glowing
orange with a propane torch, and you can see the end of the spoke move
as the bend expands.
So I cobbled together a crude vise rig and started bending spokes into
U shapes.
A spoke bent but not stretched expands considerably when heated.
A spoke bent and tensioned slightly in the vise will expand noticeably
less.
A spoke bent and tensioned more will expand even less.
A spoke bent and tensioned to normal bicycle wheel levels (~200 lbs)
will hardly expand at all.
A spoke bent and tensioned to ~400 pounds will hardly expand at all,
just like the spoke tensioned to ~200 pounds.
I think that heating the whole bend to a glowing orange relieves any
residual stresses. The spoke that was never tensioned has lots of
residual stresses and its bend expands a lot. The spoke that was
lightly tensioned has had its strongest residual stresses relieved byt
the tension, so it bends less. By the time that tension has reached
200 pounds, practically all residual stresses have been relieved, so
there's practically nothing left for the heat to change, and the spoke
bend scarcely changes.
The bending after heating clearly depends on how much tension is
applied to the spoke.
Note that rather than pursuing the testing and trying to think of ways
to change the test and confirm or refute it, Jobst just complains that
it's destructive. I'm willing to listen to suggestions and arguments
about whether what happens is explained by stress relief, but red
herrings about the destruction of a few dollars worth of spokes are
absurd.
My problem with the spoke-squeezing theory is that it seems to be a
lot of theory developed to support preconceived and self-flattering
conclusions about how we can cure the King's Evil by the laying on of
hands.
My counter-argument is subject to the same criticism in that I
naturally want my tests and interpretations to be right.
But I think that it's obvious who's interested in actual testing and
measuring. There's not only a lack of interest in testing and
confirmation on one side, but an explicit bias against any testing or
confirmation. Anyone can read through the endless posts on the subject
and see commment after comment about how no tests would be convincing
evidence against the theory, how no tests are needed, and how we don't
need no stinkin' tests.
Of course, the stress-relief question is just a tempest in a tea-cup.
But it does shed some interesting light on how prone RBT is to typing
and defending theories instead of trying to test them.
Cheers,
Carl Fogel
jim beam
carl, i gotta say, that's an excellent summary of the situation. in
terms of theory, you are 100% correct about the influence of materials
on fatigue vs. unsubstantiated supposition, and you are 100% correct
about your heating experiments being illustrative of residual stress
relaxation - no bending on heating, no residual stress. finally, your
experiments on spoke tension increase on squeezing are excellent. i
would have always thought it obvious that when the usual bleatings about
"wheels stand on their bottom spokes" were being batted around, we were
simply observing rim deformation [hopefully it's obvious that if the rim
were perfectly rigid, spoke tension pattern would be totally different],
but apparently not.
i only have one other comment; it is /not/ correct to say that "all rbt
posters agree" that spokes contain residual stress just because they're
bent however - that's the jobstian assumption that seems to have
propagated into the vacuum that is the mind of the unquestioning.
but all in all, a great summary, and i applaud your willingness to ask
the difficult question "why?" - it seems to be a dirty word around these
parts. i guess because most people that dare ask it are derided as
charlatans and [understandably] take their learning elsewhere. a very
regrettable state of affairs.
Peter Cole
> spokes angle towards a rim at say 6 degrees both sides front, and say 6
> + 3 for rears. and that is what hub flanges are canted to. in
> addition, hub holes are angled perpendicular to the flange, so they too
> are aligned for optimal spoke position.
>
> see:
> http://www.flickr.com/photos/38636024@N00/316202144/
> http://www.flickr.com/photos/38636024@N00/316202143/
I find your "pencil test" a bit unconvincing.
I have a new, never spoked, LX rear hub (Shimano SH-FHM570-32). I found
that a 8d finish nail is almost an interference fit in the spoke holes.
I can state with absolute certainty that the holes are drilled parallel
to the axle, not perpendicular to the flange.
Peter Cole
> After all, the most likely explanation for an occasional spoke
> breaking is variation in the spoke material. The bending and
> tensioning and so forth are quite regular. If squeezing spoke pairs
> was solving some residual stress problem by raising tension, the same
> problem would be causing all the other spokes to fail.
>
> I see Jobst's comment in 1993 that spokes somehow became much more
> durable as strong evidence that he was mistaken about how efffective
> spoke-sqeezing is.
I think you're missing the point. Spoke failure is from fatigue. Fatigue
life is shortened both by poor material quality and residual stress.
Removing residual stress will make poor spokes and good spokes last
longer. That even modern, presumably better made, spokes can benefit
from stress relief is supported by the observation that spoke failures
still occur.
> This illustrates how easily we fool ourselves and how easy it is to
> make huge mistakes. I have never doubted the good faith of the last
> such calculation that appeared on RBT. A 30 pound side force moved a
> spoke a certain distance and bent the spoke at such and so an angle,
> which in turn allowed calculations for steel of specifc thickness to
> indicate that the spoke tension would rise approximately 150 pounds, a
> 5 to 1 ratio.
I think you're mis-remembering that thread. Phil Holman reported
measuring that 5:1 ratio on his wheel. After much posting, all concluded
that little could be improved in Jobst's description in his book. The
reason you found such a surprising (to yourself) ratio of 1:1 was
because your rims were not very stiff.
> The next thing to test was the effect of tension on residual stress.
> So I cobbled together a crude vise rig and started bending spokes into
> U shapes.
>
> A spoke bent but not stretched expands considerably when heated.
>
> A spoke bent and tensioned slightly in the vise will expand noticeably
> less.
>
> A spoke bent and tensioned more will expand even less.
>
> A spoke bent and tensioned to normal bicycle wheel levels (~200 lbs)
> will hardly expand at all.
>
> A spoke bent and tensioned to ~400 pounds will hardly expand at all,
> just like the spoke tensioned to ~200 pounds.
I had trouble following this "experiment". I assume that after
tensioning the spokes had very different "starting angles" before heat
was applied? It's very difficult to know exactly what was going on,
specifically if the various changes in angle with heating have anything
to do with residual stresses at all.
> My problem with the spoke-squeezing theory is that it seems to be a
> lot of theory developed to support preconceived and self-flattering
> conclusions about how we can cure the King's Evil by the laying on of
> hands.
This method of relieving residual stress is well known and used in
various industrial processes.
carl...@comcast.net
<peter...@comcast.net> wrote:
[snip]
>I think you're mis-remembering that thread. Phil Holman reported
>measuring that 5:1 ratio on his wheel. After much posting, all concluded
>that little could be improved in Jobst's description in his book. The
>reason you found such a surprising (to yourself) ratio of 1:1 was
>because your rims were not very stiff.
[snip]
Dear Peter,
No, I tested various wheels, including a box-section Mavic MA3, and
found the same results. You must have missed those details.
Apparently, you also missed my more recent test, in which I hung
weights on a horizontal spoke tensioned in a massive pipe-clamp rig,
far stiffer than any bicycle wheel:
http://groups.google.com/group/rec.bicycles.tech/msg/bce241a75595fbed
A 60-pound weight produced only a 90-pound tension rise when hung from
the middle of horizontal spoke whose original tension was 235 pounds.
Of course, no bicycle rim will ever approach the stiffness of a pair
of steel clamps on a 3/4" steel pipe whose walls are thicker than the
spoke itself.
Again, the impressive bend angles seen when pairs of bicycle spokes
are squeezed are not signs of huge tension increases. The bends are
the result of the slack gained when the rim distorts into a faint N or
Z shape and the slack gained when the squeezed spoke presses down
against the unsqueezed spoke in a 3-cross patter.
Feel free to do some actual testing instead of just asserting that
stiffer rims will produce the results that you want.
The pipe clamp cost eight bucks, the spoke was about fifty cents. A
tension gauge costs about $50, but no one really interested in this
kind of thing can consider that a barrier.
Cheers,
Carl Fogel
Peter Cole
> On Wed, 20 Dec 2006 16:59:12 -0500, Peter Cole
> <peter...@comcast.net> wrote:
>
> [snip]
>
>> I think you're mis-remembering that thread. Phil Holman reported
>> measuring that 5:1 ratio on his wheel. After much posting, all concluded
>> that little could be improved in Jobst's description in his book. The
>> reason you found such a surprising (to yourself) ratio of 1:1 was
>> because your rims were not very stiff.
>
> [snip]
>
> Dear Peter,
>
> No, I tested various wheels, including a box-section Mavic MA3, and
> found the same results. You must have missed those details.
You apparently assume the MA3 is a stiff rim. A box section does not
improve stiffness, as it adds material in the neutral plane (something
Jobst has pointed out before). Rim stiffness is pretty much a function
of cross section height.
> Apparently, you also missed my more recent test, in which I hung
> weights on a horizontal spoke tensioned in a massive pipe-clamp rig,
> far stiffer than any bicycle wheel:
>
> http://groups.google.com/group/rec.bicycles.tech/msg/bce241a75595fbed
>
> A 60-pound weight produced only a 90-pound tension rise when hung from
> the middle of horizontal spoke whose original tension was 235 pounds.
>
> Of course, no bicycle rim will ever approach the stiffness of a pair
> of steel clamps on a 3/4" steel pipe whose walls are thicker than the
> spoke itself.
How can you be sure of the stiffness of your fixture without measuring
it? How can you be sure that your spoke mounting/support exactly
replicates a hub and rim? There are many ways for errors to creep in.
> Again, the impressive bend angles seen when pairs of bicycle spokes
> are squeezed are not signs of huge tension increases. The bends are
> the result of the slack gained when the rim distorts into a faint N or
> Z shape and the slack gained when the squeezed spoke presses down
> against the unsqueezed spoke in a 3-cross patter.
As said so many times before, the spoke angle only reveals the ratio of
forces. To say you get low ratios and large angles is just repeating
yourself. The real question is why the angles are large. This can only
be from something in the path that is less stiff than the spoke itself.
Likely candidates are the rim and the spoke path/end support. You
generalize from your measurements on your wheels to predict that all of
us get less tension increases than you, despite at least one report to
the contrary.
This is, of course, a tempest in a teapot, since it makes little
difference what the precise amount of spoke overload is as long as it
falls within the rough bounds of being enough to improve the residual
stresses but not so much as to damage the rim.
> Feel free to do some actual testing instead of just asserting that
> stiffer rims will produce the results that you want.
I would be perfectly happy with 60 lbf that your worst case tests seem
to predict.
jim beam
ok, i accept that. maybe it's a high flange vs. low flange thing.
maybe it's a quality level thing - mine was xt. but my hub /definitely/
has holes perpendicular to the canted flange.
but all this is dodging the fundamental questions:
1. does or does not hub hole conformation lessen the required spoke angle?
2. does or does not "correcting the spoke line" /prior/ to hub hole
conformation exaggerate the "correction", i.e. make it excessive?
3. how does elastic stress from an undeformed spoke bending toward the
rim compare to that where the spoke bends around its interleaving
partner? from what i can see, the angle is very similar so skin stress
has to be of similar magnitude.
jim beam
> carl...@comcast.net wrote:
>
>> After all, the most likely explanation for an occasional spoke
>> breaking is variation in the spoke material. The bending and
>> tensioning and so forth are quite regular. If squeezing spoke pairs
>> was solving some residual stress problem by raising tension, the same
>> problem would be causing all the other spokes to fail.
>>
>> I see Jobst's comment in 1993 that spokes somehow became much more
>> durable as strong evidence that he was mistaken about how efffective
>> spoke-sqeezing is.
>
>
> I think you're missing the point. Spoke failure is from fatigue. Fatigue
> life is shortened both by poor material quality and residual stress.
> Removing residual stress will make poor spokes and good spokes last
> longer. That even modern, presumably better made, spokes can benefit
> from stress relief is supported by the observation that spoke failures
> still occur.
sure they do. and it's almost always inferior no-name spokes. one
of my coworkers was breaking spokes every week earlier this year and
gave me the broken ones to examine. sure enough, no-name and serious
surface quality issues. all he needed was a rebuild with a quality
brand spoke and his breakage issues have been eliminated.
absolutely they do! that's why frames need to be re-set after heat
treatment for example.
>
>
>> My problem with the spoke-squeezing theory is that it seems to be a
>> lot of theory developed to support preconceived and self-flattering
>> conclusions about how we can cure the King's Evil by the laying on of
>> hands.
>
> This method of relieving residual stress is well known and used in
> various industrial processes.
indeed. but with a quality material without residual stress, it's
pointless and can initiate fatigue, not eliminate it. when's the last
time you saw a bridge being "stress relieved"?
Peter Cole
> Peter Cole wrote:
>> I find your "pencil test" a bit unconvincing.
>>
>> I have a new, never spoked, LX rear hub (Shimano SH-FHM570-32). I
>> found that a 8d finish nail is almost an interference fit in the spoke
>> holes. I can state with absolute certainty that the holes are drilled
>> parallel to the axle, not perpendicular to the flange.
>
> ok, i accept that. maybe it's a high flange vs. low flange thing.
> maybe it's a quality level thing - mine was xt. but my hub /definitely/
> has holes perpendicular to the canted flange.
>
> but all this is dodging the fundamental questions:
If you say so, but I'd still like to see evidence of a hub drilled
perpendicular to the flange.
> 1. does or does not hub hole conformation lessen the required spoke angle?
> 2. does or does not "correcting the spoke line" /prior/ to hub hole
> conformation exaggerate the "correction", i.e. make it excessive?
> 3. how does elastic stress from an undeformed spoke bending toward the
> rim compare to that where the spoke bends around its interleaving
> partner? from what i can see, the angle is very similar so skin stress
> has to be of similar magnitude.
First, I'm not aware of anyone (other than Sheldon, & I don't agree with
him) correcting the spoke line before the wheel is tensioned, so I'm not
sure who you're arguing with.
In all of the above cases, the only important thing is that the spoke
take as straight a line as possible. If the spoke has a bend in it, the
spoke will flex under change of tension, accelerating fatigue. If, after
the wheel is tensioned, the spokes have a bow in them where they exit
the flange, it is necessary to correct the line to prevent flex in
operation. If they don't, it isn't. The elbow is a critical fatigue
location, the crossover is not. The only spokes I have ever seen break
at places other than the elbow or threads were chain-nicked.
Peter Cole
> Peter Cole wrote:
>> I think you're missing the point. Spoke failure is from fatigue.
>> Fatigue life is shortened both by poor material quality and residual
>> stress. Removing residual stress will make poor spokes and good spokes
>> last longer. That even modern, presumably better made, spokes can
>> benefit from stress relief is supported by the observation that spoke
>> failures still occur.
>
> sure they do. and it's almost always inferior no-name spokes. one
> of my coworkers was breaking spokes every week earlier this year and
> gave me the broken ones to examine. sure enough, no-name and serious
> surface quality issues. all he needed was a rebuild with a quality
> brand spoke and his breakage issues have been eliminated.
I have had a few DT spokes fail (at elbows) before I began stress
relieving, none since.
>> I had trouble following this "experiment". I assume that after
>> tensioning the spokes had very different "starting angles" before heat
>> was applied? It's very difficult to know exactly what was going on,
>> specifically if the various changes in angle with heating have
>> anything to do with residual stresses at all.
>
> absolutely they do! that's why frames need to be re-set after heat
> treatment for example.
Carl didn't "heat treat". Thermal warping has many causes. If even the
direction (never mind the magnitude) revealed residual stresses, why did
carbon steel spokes bend the other way?
>> This method of relieving residual stress is well known and used in
>> various industrial processes.
>
> indeed. but with a quality material without residual stress, it's
> pointless and can initiate fatigue, not eliminate it.
You assume that spokes are delivered w/o residual stresses and that none
are introduced in wheel building. The only way the first could be true
is if the manufacturer annealed the spokes -- I have seen no claims of
this -- you? If, after unlacing a tensioned wheel, spoke elbow angles
are no longer equal, there must be residual stresses introduced.
> when's the last
> time you saw a bridge being "stress relieved"?
Perhaps not bridges, but I posted a link to an overload stress relief
procedure required by the Coast Guard for large pressure tanks. At least
some companies market equipment for vibrational stress relief of large
structures. The principle is the same. I don't know what parts of a
bridge you think might need stress relief, but for known problems like
welds, mitigation is done.
Gary Young
Peter,
On your hub, are the inner faces of the flanges perpendicular to the axle,
or are they canted at the same angle as the outer faces (that is, are they
parallel to the outer faces)?
On my XT rear hub, they are perpendicular to the axle. I suspect that's a
compromise made because of the difficulty of making a concave surface in a
forged hub, at least without subsequent machining.
The reason I ask is that if some of the commonest hubs out there don't
have optimized inner faces, then jim beam's theory that spoke lines don't
need adjusted doesn't hold water.
dvt
> The reason I ask is that if some of the commonest hubs out there don't
> have optimized inner faces, then jim beam's theory that spoke lines don't
> need adjusted doesn't hold water.
jim beam has admitted that his theory is limited to special cases. It's
so limited as to have little application in real life.
jim beam
> jim beam wrote:
>> Peter Cole wrote:
>
>>> I find your "pencil test" a bit unconvincing.
>>>
>>> I have a new, never spoked, LX rear hub (Shimano SH-FHM570-32). I
>>> found that a 8d finish nail is almost an interference fit in the
>>> spoke holes. I can state with absolute certainty that the holes are
>>> drilled parallel to the axle, not perpendicular to the flange.
>>
>> ok, i accept that. maybe it's a high flange vs. low flange thing.
>> maybe it's a quality level thing - mine was xt. but my hub /definitely/
>> has holes perpendicular to the canted flange.
>>
>> but all this is dodging the fundamental questions:
>
> If you say so, but I'd still like to see evidence of a hub drilled
> perpendicular to the flange.
i gave you a pic peter! the pencil may not have been a wise choice of
indicator for a hardened disbeliever like you, but i assure you, it's
jammed in so it's perpendicular to the hole - the wood deforms to a
cylinder that perfectly fits and is square to the pencil axis on removal.
>
>
>> 1. does or does not hub hole conformation lessen the required spoke
>> angle?
>> 2. does or does not "correcting the spoke line" /prior/ to hub hole
>> conformation exaggerate the "correction", i.e. make it excessive?
>> 3. how does elastic stress from an undeformed spoke bending toward the
>> rim compare to that where the spoke bends around its interleaving
>> partner? from what i can see, the angle is very similar so skin stress
>> has to be of similar magnitude.
>
> First, I'm not aware of anyone (other than Sheldon, & I don't agree with
> him) correcting the spoke line before the wheel is tensioned, so I'm not
> sure who you're arguing with.
jobst brandt!!! its specifically stated in "the book"!
>
> In all of the above cases, the only important thing is that the spoke
> take as straight a line as possible. If the spoke has a bend in it, the
> spoke will flex under change of tension, accelerating fatigue.
no, the spoke elbow is fundamentally going to flex regardless. the
elbow's offset means load is non-axial, hence the elbow /will/ bend.
and it is /that/ which causes fatigue, not the ethereal dragon that is
alleged to be "stress relief".
> If, after
> the wheel is tensioned, the spokes have a bow in them where they exit
> the flange, it is necessary to correct the line to prevent flex in
> operation.
but if that's true, it should also include the necessity to "correct"
the bow at interleaving crossover!
> If they don't, it isn't. The elbow is a critical fatigue
> location, the crossover is not.
agreed. but we may have different reasoning for that. to me, the
crossover is subcritical because the straightening of the loading cycle
runs /with/ it's natural shape and is /not/ fighting an offset like the
elbow. additionally, it's not subject to the surface defects that
inevitably accompany a bending operation like elbow forming. "orange
peel effect".
> The only spokes I have ever seen break
> at places other than the elbow or threads were chain-nicked.
indeed. and they are surface defects.
Peter Cole
The inner faces of the flanges on my LX hub are perpendicular to the
axle, yes.
jim beam
> jim beam wrote:
>> Peter Cole wrote:
>
>>> I think you're missing the point. Spoke failure is from fatigue.
>>> Fatigue life is shortened both by poor material quality and residual
>>> stress. Removing residual stress will make poor spokes and good
>>> spokes last longer. That even modern, presumably better made, spokes
>>> can benefit from stress relief is supported by the observation that
>>> spoke failures still occur.
>>
>> sure they do. and it's almost always inferior no-name spokes. one
>> of my coworkers was breaking spokes every week earlier this year and
>> gave me the broken ones to examine. sure enough, no-name and serious
>> surface quality issues. all he needed was a rebuild with a quality
>> brand spoke and his breakage issues have been eliminated.
>
> I have had a few DT spokes fail (at elbows) before I began stress
> relieving, none since.
were they from the famous "long shank" era? they broke rapidly because
of geometry issues.
>
>>> I had trouble following this "experiment". I assume that after
>>> tensioning the spokes had very different "starting angles" before
>>> heat was applied? It's very difficult to know exactly what was going
>>> on, specifically if the various changes in angle with heating have
>>> anything to do with residual stresses at all.
>>
>> absolutely they do! that's why frames need to be re-set after heat
>> treatment for example.
>
> Carl didn't "heat treat".
no. but he demonstrated the effect of residual stress.
> Thermal warping has many causes.
not many at those temperatures and that quickly. #1 candidate is
thermal stress relief. nothing else is close.
> If even the
> direction (never mind the magnitude) revealed residual stresses, why did
> carbon steel spokes bend the other way?
it's undergoing a phase change at the same time. austenitic stainless
is not.
>
>
>>> This method of relieving residual stress is well known and used in
>>> various industrial processes.
>>
>> indeed. but with a quality material without residual stress, it's
>> pointless and can initiate fatigue, not eliminate it.
>
> You assume that spokes are delivered w/o residual stresses and that none
> are introduced in wheel building. The only way the first could be true
> is if the manufacturer annealed the spokes -- I have seen no claims of
> this -- you?
with respect, the years of argument on this topic have all been
concerned with the efficacy of mechanical stress relief. why then
eliminate it and say that only thermal is possible?
> If, after unlacing a tensioned wheel, spoke elbow angles
> are no longer equal, there must be residual stresses introduced.
fogel has demonstrated that mechanical relief occurs are low levels.
mere bending is not evidence of residual stress.
>
> > when's the last
> > time you saw a bridge being "stress relieved"?
>
> Perhaps not bridges, but I posted a link to an overload stress relief
> procedure required by the Coast Guard for large pressure tanks.
and like i told you, i do not accept that explanation. every fracture
mechanics student will tell you that that procedure is done to reveal
crack flaws. there is no evidence that it performs mechanical relief,
and that's not the true objective. i can only assume that piece was
written by a well intentioned but mistaken intern.
> At least
> some companies market equipment for vibrational stress relief of large
> structures.
indeed. and they precipitate yielding. but weren[t you just arguing
that stress relief has to be thermal?
> The principle is the same. I don't know what parts of a
> bridge you think might need stress relief, but for known problems like
> welds, mitigation is done.
yes, it's thermal. elevated temperature allows hydrogen to diffuse out
before welds crack.
Peter Cole
> Peter Cole wrote:
>> jim beam wrote:
>>> Peter Cole wrote:
>>
>>>> I find your "pencil test" a bit unconvincing.
>>>>
>>>> I have a new, never spoked, LX rear hub (Shimano SH-FHM570-32). I
>>>> found that a 8d finish nail is almost an interference fit in the
>>>> spoke holes. I can state with absolute certainty that the holes are
>>>> drilled parallel to the axle, not perpendicular to the flange.
>>>
>>> ok, i accept that. maybe it's a high flange vs. low flange thing.
>>> maybe it's a quality level thing - mine was xt. but my hub /definitely/
>>> has holes perpendicular to the canted flange.
>>>
>>> but all this is dodging the fundamental questions:
>>
>> If you say so, but I'd still like to see evidence of a hub drilled
>> perpendicular to the flange.
>
> i gave you a pic peter! the pencil may not have been a wise choice of
> indicator for a hardened disbeliever like you, but i assure you, it's
> jammed in so it's perpendicular to the hole - the wood deforms to a
> cylinder that perfectly fits and is square to the pencil axis on removal.
I tried a pencil first, too, and I could believe that the hole was
canted. I tried various other things that weren't a tight fit and found
them equally ambiguous. It wasn't until I found something with an
interference fit that I became convinced that the holes were not canted.
>
>>
>>
>>> 1. does or does not hub hole conformation lessen the required spoke
>>> angle?
>>> 2. does or does not "correcting the spoke line" /prior/ to hub hole
>>> conformation exaggerate the "correction", i.e. make it excessive?
>>> 3. how does elastic stress from an undeformed spoke bending toward the
>>> rim compare to that where the spoke bends around its interleaving
>>> partner? from what i can see, the angle is very similar so skin stress
>>> has to be of similar magnitude.
>>
>> First, I'm not aware of anyone (other than Sheldon, & I don't agree
>> with him) correcting the spoke line before the wheel is tensioned, so
>> I'm not sure who you're arguing with.
>
> jobst brandt!!! its specifically stated in "the book"!
Not from my reading (which I quoted earlier). The step is described
after the section on tensioning. Furthermore, he expressed it in terms
of the spoke "may" need correction.
If a wheel is brought up to tension, and the spokes still have an overly
obtuse angle (as evidenced by bowing out from the flange), I think that
needs correction -- the spoke path is not in line with the load path.
It's Mavic who seem to propose stress relieving a partially tensioned
wheel -- for reasons I don't understand (nor do they, I'm willing to bet).
If you claim that all failed elbows you've examined failed from the
outside (as BenC says), then I don't understand why you're concerned
about an over acute elbow angle. That would put extra tension on the
inside of the bend. Perhaps all your spokes fail on the outside because
you haven't corrected the spoke line an have an over obtuse angle.
>> In all of the above cases, the only important thing is that the spoke
>> take as straight a line as possible. If the spoke has a bend in it,
>> the spoke will flex under change of tension, accelerating fatigue.
>
> no, the spoke elbow is fundamentally going to flex regardless. the
> elbow's offset means load is non-axial, hence the elbow /will/ bend. and
> it is /that/ which causes fatigue, not the ethereal dragon that is
> alleged to be "stress relief".
If the spoke line matches the load line the spoke won't bend with
changes in load.
>> If, after the wheel is tensioned, the spokes have a bow in them where
>> they exit the flange, it is necessary to correct the line to prevent
>> flex in operation.
>
> but if that's true, it should also include the necessity to "correct"
> the bow at interleaving crossover!
Since spokes have finite thickness, the spoke line has to deviate
slightly from the load line, there's no way to correct for that.
>
>> If they don't, it isn't. The elbow is a critical fatigue location, the
>> crossover is not.
>
> agreed. but we may have different reasoning for that. to me, the
> crossover is subcritical because the straightening of the loading cycle
> runs /with/ it's natural shape and is /not/ fighting an offset like the
> elbow. additionally, it's not subject to the surface defects that
> inevitably accompany a bending operation like elbow forming. "orange
> peel effect".
I think it's because the bend angle is much smaller and the spokes
support each other and prevent much bending.
jim beam
well, i accept that it may be different for different hubs, but i am
certain of the situation regarding the hub i tested.
>
>
>
>>
>>>
>>>
>>>> 1. does or does not hub hole conformation lessen the required spoke
>>>> angle?
>>>> 2. does or does not "correcting the spoke line" /prior/ to hub hole
>>>> conformation exaggerate the "correction", i.e. make it excessive?
>>>> 3. how does elastic stress from an undeformed spoke bending toward the
>>>> rim compare to that where the spoke bends around its interleaving
>>>> partner? from what i can see, the angle is very similar so skin stress
>>>> has to be of similar magnitude.
>>>
>>> First, I'm not aware of anyone (other than Sheldon, & I don't agree
>>> with him) correcting the spoke line before the wheel is tensioned, so
>>> I'm not sure who you're arguing with.
>>
>> jobst brandt!!! its specifically stated in "the book"!
>
> Not from my reading (which I quoted earlier). The step is described
> after the section on tensioning. Furthermore, he expressed it in terms
> of the spoke "may" need correction.
>
> If a wheel is brought up to tension, and the spokes still have an overly
> obtuse angle (as evidenced by bowing out from the flange), I think that
> needs correction -- the spoke path is not in line with the load path.
but again, "correcting" prior to hub hole deformation has the spoke out
of the load line too! do you dispute the geometry i illustrated?
>
> It's Mavic who seem to propose stress relieving a partially tensioned
> wheel -- for reasons I don't understand (nor do they, I'm willing to bet).
presumably because, just like they were smart enough to figure out that
j-bend spokes are fundamentally fatigue challenged, they also realized
that seating was essential /before/ anything else that could influence
final spoke line.
>
> If you claim that all failed elbows you've examined failed from the
> outside (as BenC says), then I don't understand why you're concerned
> about an over acute elbow angle.
i don't claim that. it's roughly 4:1 outside to inside. and again,
"outside" the elbow is different from the skin which is where 100% of
fatigue initiates.
> That would put extra tension on the
> inside of the bend. Perhaps all your spokes fail on the outside because
> you haven't corrected the spoke line an have an over obtuse angle.
see above.
>
>
>>> In all of the above cases, the only important thing is that the spoke
>>> take as straight a line as possible. If the spoke has a bend in it,
>>> the spoke will flex under change of tension, accelerating fatigue.
>>
>> no, the spoke elbow is fundamentally going to flex regardless. the
>> elbow's offset means load is non-axial, hence the elbow /will/ bend.
>> and it is /that/ which causes fatigue, not the ethereal dragon that is
>> alleged to be "stress relief".
>
> If the spoke line matches the load line the spoke won't bend with
> changes in load.
but it fundamentally /cannot/ match the load line for a j-bend spoke,
only straight pull.
>
>
>>> If, after the wheel is tensioned, the spokes have a bow in them where
>>> they exit the flange, it is necessary to correct the line to prevent
>>> flex in operation.
>>
>> but if that's true, it should also include the necessity to "correct"
>> the bow at interleaving crossover!
>
> Since spokes have finite thickness, the spoke line has to deviate
> slightly from the load line, there's no way to correct for that.
straight pull spokes address it as effectively as you could wish.
j-bend fundamentally cannot.
>
>
>>
>>> If they don't, it isn't. The elbow is a critical fatigue location,
>>> the crossover is not.
>>
>> agreed. but we may have different reasoning for that. to me, the
>> crossover is subcritical because the straightening of the loading
>> cycle runs /with/ it's natural shape and is /not/ fighting an offset
>> like the elbow. additionally, it's not subject to the surface defects
>> that inevitably accompany a bending operation like elbow forming.
>> "orange peel effect".
>
> I think it's because the bend angle is much smaller and the spokes
> support each other and prevent much bending.
do the math for the stress in the outer skin at the bend [3-point] -
you'll be surprised.
Peter Cole
> Peter Cole wrote:
>> I have had a few DT spokes fail (at elbows) before I began stress
>> relieving, none since.
>
> were they from the famous "long shank" era? they broke rapidly because
> of geometry issues.
I don't think so.
>> Thermal warping has many causes.
>
> not many at those temperatures and that quickly. #1 candidate is
> thermal stress relief. nothing else is close.
I don't think thermal "opening up" of bends proportional to the degree
of bend is a slam-dunk demonstration of residual stresses.
>> If even the direction (never mind the magnitude) revealed residual
>> stresses, why did carbon steel spokes bend the other way?
>
> it's undergoing a phase change at the same time. austenitic stainless
> is not.
You're guessing.
>> You assume that spokes are delivered w/o residual stresses and that
>> none are introduced in wheel building. The only way the first could be
>> true is if the manufacturer annealed the spokes -- I have seen no
>> claims of this -- you?
>
> with respect, the years of argument on this topic have all been
> concerned with the efficacy of mechanical stress relief. why then
> eliminate it and say that only thermal is possible?
With equal respect, why should DT, or any other, mess about with
mechanical stress relief in formed parts when annealing would be so much
easier? On the other hand, annealing a built wheel presents some thorny
issues. I thought those arguments were obvious.
>> If, after unlacing a tensioned wheel, spoke elbow angles are no longer
>> equal, there must be residual stresses introduced.
>
> fogel has demonstrated that mechanical relief occurs are low levels.
> mere bending is not evidence of residual stress.
I think he showed thermal deformation, the cause of which is unclear.
>> > when's the last
>> > time you saw a bridge being "stress relieved"?
>>
>> Perhaps not bridges, but I posted a link to an overload stress relief
>> procedure required by the Coast Guard for large pressure tanks.
>
> and like i told you, i do not accept that explanation. every fracture
> mechanics student will tell you that that procedure is done to reveal
> crack flaws. there is no evidence that it performs mechanical relief,
> and that's not the true objective. i can only assume that piece was
> written by a well intentioned but mistaken intern.
Sure, if you say so.
>
>> At least some companies market equipment for vibrational stress relief
>> of large structures.
>
> indeed. and they precipitate yielding. but weren[t you just arguing
> that stress relief has to be thermal?
No, just that it's the easier way sometimes.
>> The principle is the same. I don't know what parts of a bridge you
>> think might need stress relief, but for known problems like welds,
>> mitigation is done.
>
> yes, it's thermal. elevated temperature allows hydrogen to diffuse out
> before welds crack.
So bridges are stress relieved?
jim beam
> jim beam wrote:
>> Peter Cole wrote:
>
>>> I have had a few DT spokes fail (at elbows) before I began stress
>>> relieving, none since.
>>
>> were they from the famous "long shank" era? they broke rapidly
>> because of geometry issues.
>
> I don't think so.
>
>
>>> Thermal warping has many causes.
>>
>> not many at those temperatures and that quickly. #1 candidate is
>> thermal stress relief. nothing else is close.
>
> I don't think thermal "opening up" of bends proportional to the degree
> of bend is a slam-dunk demonstration of residual stresses.
i'm not saying it quantifies because it doesn't, but it reliably
demonstrates.
>
>
>>> If even the direction (never mind the magnitude) revealed residual
>>> stresses, why did carbon steel spokes bend the other way?
>>
>> it's undergoing a phase change at the same time. austenitic stainless
>> is not.
>
> You're guessing.
it's definitely undergoing phase change. the "guess" is whether it
explains the difference, but it's an educated guess based on facts i
know, not stuff i've made up. can you explain better?
>
>>> You assume that spokes are delivered w/o residual stresses and that
>>> none are introduced in wheel building. The only way the first could
>>> be true is if the manufacturer annealed the spokes -- I have seen no
>>> claims of this -- you?
>>
>> with respect, the years of argument on this topic have all been
>> concerned with the efficacy of mechanical stress relief. why then
>> eliminate it and say that only thermal is possible?
>
> With equal respect, why should DT, or any other, mess about with
> mechanical stress relief in formed parts when annealing would be so much
> easier?
because it will soften the steel! spoke steel is worked to ~1000N/mm^2
yield. annealed, i doubt it would be 400N/mm^2.
> On the other hand, annealing a built wheel presents some thorny
> issues. I thought those arguments were obvious.
apparently not.
>
>>> If, after unlacing a tensioned wheel, spoke elbow angles are no
>>> longer equal, there must be residual stresses introduced.
>>
>> fogel has demonstrated that mechanical relief occurs are low levels.
>> mere bending is not evidence of residual stress.
>
> I think he showed thermal deformation, the cause of which is unclear.
there is no impetus to deform other than that caused by [internal]
residual stress. unless he fabricated results of course. but i doubt
that since his results are consistent with materials theory.
>
>>> > when's the last
>>> > time you saw a bridge being "stress relieved"?
>>>
>>> Perhaps not bridges, but I posted a link to an overload stress relief
>>> procedure required by the Coast Guard for large pressure tanks.
>>
>> and like i told you, i do not accept that explanation. every fracture
>> mechanics student will tell you that that procedure is done to reveal
>> crack flaws. there is no evidence that it performs mechanical relief,
>> and that's not the true objective. i can only assume that piece was
>> written by a well intentioned but mistaken intern.
>
> Sure, if you say so.
>
>>
>>> At least some companies market equipment for vibrational stress
>>> relief of large structures.
>>
>> indeed. and they precipitate yielding. but weren[t you just arguing
>> that stress relief has to be thermal?
>
> No, just that it's the easier way sometimes.
depends on application. you /don't/ want to thermally stress relieve
cold drawn wire unless you want to soften it too.
>
>
>>> The principle is the same. I don't know what parts of a bridge you
>>> think might need stress relief, but for known problems like welds,
>>> mitigation is done.
>>
>> yes, it's thermal. elevated temperature allows hydrogen to diffuse
>> out before welds crack.
>
> So bridges are stress relieved?
no - temperature is insufficient for that. usually they're pre-heated
to a few hundred degrees to minimize stress gradient on weld pool
solidification and retro-heated to allow hydrogen to diffuse out. you
can argue that hydrogen presence causes internal stress, but it's not
the result of weld pool phase change or contraction.