removing broken spoke nipples

  • Thread starter Bellsouth Ijit 2.0
  • Start date



On Sat, 17 Mar 2007 16:46:41 -0500, Ben C <[email protected]> wrote:

>On 2007-03-17, [email protected] <[email protected]> wrote:
>> On 17 Mar 2007 20:04:39 GMT, [email protected] wrote:
>>
>>>Carl Fogel writes:

>[...]
>>>> Squeezing spoke pairs together usually changes something enough to
>>>> require small truing adjustments:
>>>
>>>> "If, after stress relieving, the wheel is appreciably out of true in
>>>> two smooth waves, then tension was too high, and retruing should
>>>> begin by relaxing tension of all spokes half a turn. Usually, only
>>>> small lateral corrections will be necessary after stress relieving."
>>>
>>>> --"The Bicycle Wheel," 3rd edition, p. 106
>>>
>>>I find that is a misinterpretation. The above citation explains what
>>>occurs if spoke tension it too high, not what stress relieving does.
>>>The issue at hand is whether spokes must be re-tensioned after stress
>>>relieving. The above mentions retruing, not re-tensioning. Spokes do
>>>not require re-tensioning!

>[...]
>> Dear Jobst,
>>
>> "Usually, only small lateral corrections will be necessary after
>> stress relieving."
>>
>> What is the difference between turning a spoke nipple to laterally
>> true a rim and turning a spoke nipple to change the spoke tension?

>
>The difference is in the intention. In one case you adjust one or two
>spokes to make the wheel true; in the other you adjust them all to
>change the wheel's tension.
>
>We still make distinctions between radial truing, lateral truing,
>tensioning and dishing, even though they all consist of turning the
>nipples.
>
>(Conversely, bashing the wheel on a tree-trunk, walking on it, squeezing
>it, leaning on it and mangling it with a crowbar are all called the same
>thing: "stress-relief").
>
>If stress-relief reduced whole-spoke tension significantly you'd expect
>to have to tighten up all the spokes by a bit to compensate, since you
>have stress-relieved all of them. That it may affect the tension of one
>or two enough to require a bit of re-truing just reflects the fact that
>nothing's perfect.


Dear Ben,

Why do sections of the rim move laterally enough to need truing after
spoke pairs are squeezed?

I can think of four possible reasons, any or all of which may be
involved.

First, the rim may not actually change. It could be that the wheel
builder tensions and trues the wheel up, squeezes all the spoke pairs,
gives the wheel a spin, and just can't help himself--the wheel hasn't
actually changed, but it can always be trued a little here or there.
This would be perfectly understandable, nothing dishonest.

(For all I know, the lateral movement is so gross and obvious to
experienced wheel builders that this psychological explanation can be
dismissed. I haven't enough confidence in my truing and tensioning to
have an opinion one way or the other.)

Second, some piece of metal may actually change. The rim, socket,
eyelet, nipple, spoke, or hub could yield here or there, which would
cause the rim to need some lateral truing.

(That's the point that I think is being debated here.)

Third, the rim may be able to move laterally without any metal
yielding on a cross-X laced wheel. When spoke pairs are squeezed,
there may be no noticeable yielding of the kind that would let the rim
move from side to side--but the crossings could shift slightly to a
new position, adding or reducing tension.

If two spokes were stuck at the crossing and squeezing them unstuck
them, then their tension would be slightly reduced and the rim would
move away from their side of the hub.

(No yielding is involved here, just the stubborn friction of crossed
spokes. But the overall tension changes.)

Fourth, the tension of all the spokes and the rim might somehow be
re-arranged without changing the sum. Nothing yields, the total
tension doesn't change, but the rim changes shape--this section bends
a little to one side, but another section bends exactly enough to the
other side to compensate.

(I think that's what you're suggesting, but I may be wrong.)

Cheers,

Carl Fogel
 
M

Michael Press

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

> On 17 Mar 2007 20:04:39 GMT, [email protected] wrote:
>
> >Carl Fogel writes:
> >
> >>>> I think that's true, but if the re-increase is not uniform, but a
> >>>> bending stress, then we will bring the outside of the elbow
> >>>> straight back to yield, and we will be back to square one.

> >
> >>>> Practically speaking if you have to re-tension after stress relief
> >>>> you would be advised to stress relieve again.

> >
> >>> I think you should review what sort of yield stress relief causes.
> >>> These are length changes of microns while the spoke as a whole is
> >>> elastically stretched on the order of a millimeter, there is no
> >>> practically measurable change in length or in tension in spokes
> >>> from stress relieving. Your suggestion that spokes need
> >>> re-tensioning after stress relief is misplaced. Spokes do not sink
> >>> into the flanges further after tensioning when stress relieved
> >>> enough to affect tension. By that point in the wheel build they
> >>> have asymptotically reached home position.

> >
> >> Squeezing spoke pairs together usually changes something enough to
> >> require small truing adjustments:

> >
> >> "If, after stress relieving, the wheel is appreciably out of true in
> >> two smooth waves, then tension was too high, and retruing should
> >> begin by relaxing tension of all spokes half a turn. Usually, only
> >> small lateral corrections will be necessary after stress relieving."

> >
> >> --"The Bicycle Wheel," 3rd edition, p. 106

> >
> >I find that is a misinterpretation. The above citation explains what
> >occurs if spoke tension it too high, not what stress relieving does.
> >The issue at hand is whether spokes must be re-tensioned after stress
> >relieving. The above mentions retruing, not re-tensioning. Spokes do
> >not require re-tensioning!
> >
> >So while you're at it, how about commenting on the nature of the
> >exchange taking place in this thread offered by "jb"? I ask because
> >you are so quick to find fault with content and tenor of my responses.
> >How does content and tone of those exchanges escape your critique?
> >
> >Jobst Brandt

>
> Dear Jobst,
>
> "Usually, only small lateral corrections will be necessary after
> stress relieving."
>
> What is the difference between turning a spoke nipple to laterally
> true a rim and turning a spoke nipple to change the spoke tension?
>
> Cheers,


I don't think so. You know very well the answer
to the question you seem to be asking.
--
Michael Press
 
J

jim beam

Guest
[email protected] wrote:
> Carl Fogel writes:
>
>>>>>> I think that's true, but if the re-increase is not uniform, but
>>>>>> a bending stress, then we will bring the outside of the elbow
>>>>>> straight back to yield, and we will be back to square one.

>
>>>>>> Practically speaking if you have to re-tension after stress
>>>>>> relief you would be advised to stress relieve again.

>
>>>>> I think you should review what sort of yield stress relief
>>>>> causes. These are length changes of microns while the spoke as a
>>>>> whole is elastically stretched on the order of a millimeter,
>>>>> there is no practically measurable change in length or in tension
>>>>> in spokes from stress relieving. Your suggestion that spokes
>>>>> need re-tensioning after stress relief is misplaced. Spokes do
>>>>> not sink into the flanges further after tensioning when stress
>>>>> relieved enough to affect tension. By that point in the wheel
>>>>> build they have asymptotically reached home position.

>
>>>> Squeezing spoke pairs together usually changes something enough to
>>>> require small truing adjustments:

>
>>>> "If, after stress relieving, the wheel is appreciably out of true
>>>> in two smooth waves, then tension was too high, and retruing
>>>> should begin by relaxing tension of all spokes half a
>>>> turn. Usually, only small lateral corrections will be necessary
>>>> after stress relieving."

>
>>>> --"The Bicycle Wheel," 3rd edition, p. 106

>
>>> I find that is a misinterpretation. The above citation explains
>>> what occurs if spoke tension it too high, not what stress relieving
>>> does. The issue at hand is whether spokes must be re-tensioned
>>> after stress relieving. The above mentions retruing, not
>>> re-tensioning. Spokes do not require re-tensioning!

>
>>> So while you're at it, how about commenting on the nature of the
>>> exchange taking place in this thread offered by "jb"? I ask
>>> because you are so quick to find fault with content and tenor of my
>>> responses. How does content and tone of those exchanges escape
>>> your critique?

>
>> "Usually, only small lateral corrections will be necessary after
>> stress relieving."

>
>> What is the difference between turning a spoke nipple to laterally
>> true a rim and turning a spoke nipple to change the spoke tension?

>
> One is adding tension the other is truing the wheel, which in this
> case is loosening and tightening appropriate spokes, in contrast to
> restoring lost tension to the wheel.


so it's semantics then! love it! new engineering technology! the
jobstian semantic wrench! the jobstian semantiometer [that makes no
account of spoke stiffness]! this is going to revolutionize the world!
anyone know a patent lawyer?

>
> So what do you have to offer about the rude epithets appearing on this
> thread? I hear sounds of silence.
>
> Jobst Brandt
 
G

Gary Young

Guest
On Sat, 17 Mar 2007 20:42:04 -0700, carlfogel wrote:

> On Sat, 17 Mar 2007 16:46:41 -0500, Ben C <[email protected]> wrote:
>
>>On 2007-03-17, [email protected] <[email protected]> wrote:
>>> On 17 Mar 2007 20:04:39 GMT, [email protected] wrote:
>>>
>>>>Carl Fogel writes:

>>[...]
>>>>> Squeezing spoke pairs together usually changes something enough to
>>>>> require small truing adjustments:
>>>>
>>>>> "If, after stress relieving, the wheel is appreciably out of true in
>>>>> two smooth waves, then tension was too high, and retruing should
>>>>> begin by relaxing tension of all spokes half a turn. Usually, only
>>>>> small lateral corrections will be necessary after stress relieving."
>>>>
>>>>> --"The Bicycle Wheel," 3rd edition, p. 106
>>>>
>>>>I find that is a misinterpretation. The above citation explains what
>>>>occurs if spoke tension it too high, not what stress relieving does.
>>>>The issue at hand is whether spokes must be re-tensioned after stress
>>>>relieving. The above mentions retruing, not re-tensioning. Spokes do
>>>>not require re-tensioning!

>>[...]
>>> Dear Jobst,
>>>
>>> "Usually, only small lateral corrections will be necessary after
>>> stress relieving."
>>>
>>> What is the difference between turning a spoke nipple to laterally
>>> true a rim and turning a spoke nipple to change the spoke tension?

>>
>>The difference is in the intention. In one case you adjust one or two
>>spokes to make the wheel true; in the other you adjust them all to
>>change the wheel's tension.
>>
>>We still make distinctions between radial truing, lateral truing,
>>tensioning and dishing, even though they all consist of turning the
>>nipples.
>>
>>(Conversely, bashing the wheel on a tree-trunk, walking on it, squeezing
>>it, leaning on it and mangling it with a crowbar are all called the same
>>thing: "stress-relief").
>>
>>If stress-relief reduced whole-spoke tension significantly you'd expect
>>to have to tighten up all the spokes by a bit to compensate, since you
>>have stress-relieved all of them. That it may affect the tension of one
>>or two enough to require a bit of re-truing just reflects the fact that
>>nothing's perfect.

>
> Dear Ben,
>
> Why do sections of the rim move laterally enough to need truing after
> spoke pairs are squeezed?
>
> I can think of four possible reasons, any or all of which may be
> involved.
>
> First, the rim may not actually change. It could be that the wheel
> builder tensions and trues the wheel up, squeezes all the spoke pairs,
> gives the wheel a spin, and just can't help himself--the wheel hasn't
> actually changed, but it can always be trued a little here or there.
> This would be perfectly understandable, nothing dishonest.
>
> (For all I know, the lateral movement is so gross and obvious to
> experienced wheel builders that this psychological explanation can be
> dismissed. I haven't enough confidence in my truing and tensioning to
> have an opinion one way or the other.)


I think you have to draw a distinction between two kinds of lateral
movement. Ordinarily, out-of-trueness is asymmetrical -- you may have one
high-spot at 3 o'clock, and another at 5 o'clock, or 6 or 7, or at some
other arbitrary point.

However, there's a different kind of out-of-trueness that occurs when the
spoke tension is so high that stress relieving raises the tension above
the level that the rim can bear. See page 105: "Stress relieving ...
increases tension enough to overload the rim if the spokes are too
tight." If I understand things correctly, the rim is actually on the
threshold of buckling. As in buckling or potato-chipping, "two large
waves" appear.

That second kind of out-of-trueness is in fact "gross and obvious"
because the two waves are symmetrical. There will be high spots at 12 and
6 o'clock and low spots at 3 and 9 o'clock. I usually use heavier rims
(e.g., Sun CR-18s), so the amplitude of the waves is small, but they are
large and unmistakable in that each covers half the rim.

The second kind of out-of-trueness indicates that the spokes are
dangerously tight and Jobst recommends that every spoke be loosened half
a turn and that no more tensioning be done (except small increases here
and there to eliminate asymmetrical out-of-trueness and to equalize
tension among the spokes).

(I don't quite understand why the two waves don't disappear after one
stops squeezing spoke pairs. I'm guessing that passing the threshold into
buckling is such a major transition that only fairly gross changes can
reverse it.)

I sometimes get asymmetrical out-of-trueness after stress-relieving. I
think the main cause is that I haven't been entirely successful in
eliminating windup. A byproduct of stress relieving (but not its main
purpose) is to release the windup, thus causing the rim to go out of true.

I think these effects are distinct enough that "the wheelbuilder is
fooling himself" can be eliminated as an explanation.

>
> Second, some piece of metal may actually change. The rim, socket,
> eyelet, nipple, spoke, or hub could yield here or there, which would
> cause the rim to need some lateral truing.
>
> (That's the point that I think is being debated here.)


I don't think so. I think you're conflating two different things. Even
jim beam, who thinks that stress relieving causes yielding that leads to
out-of-trueness, would -- I believe -- say that the yielding occurs only
in the hub and perhaps the rim as the steel spokes bite into aluminum.

As I understand it, yielding plays no part in Jobst's explanation of why
stress-relieving produces out-of-trueness.

In Jobst's view, stress-relieving does lead to yielding, but it occurs at
the elbows and threads in movements so small (indeed, movements mostly
internal to the spoke) that there's no appreciable effect on rim
alignment.

To sum up:

jim beam -- there's no yielding at the elbow and threads (or at least no
yielding that would lead to the relief of residual stress). However,
there is yielding, in the form of bedding-in, that causes changes in rim
alignment.

Jobst -- The purpose of stress relieving is to produce yielding of a
small magnitude at the elbows and threads, thus relieving residual
stress. As a byproduct, stress relieving sometimes produces changes in
rim alignment that are caused by increases in tension and not yielding.

>
> Third, the rim may be able to move laterally without any metal yielding
> on a cross-X laced wheel. When spoke pairs are squeezed, there may be no
> noticeable yielding of the kind that would let the rim move from side to
> side--but the crossings could shift slightly to a new position, adding
> or reducing tension.
>

I haven't been following this discussion very closely, but who, other
than yourself, suggests that spoke crossings play a role here? I don't
see why it's necessary to add that to the mix.


> If two spokes were stuck at the crossing and squeezing them unstuck
> them, then their tension would be slightly reduced and the rim would
> move away from their side of the hub.
>
> (No yielding is involved here, just the stubborn friction of crossed
> spokes. But the overall tension changes.)


Again, I think you're overlooking changes in alignment that occur as a
byproduct of stress-relieving but that aren't caused by yielding of the
elbows and threads -- i.e., by taking the rim beyond its safe limit or
releasing windup.

Its true that jim beam thinks that changes in alignment occur through
yielding, but it's the bedding-in kind of yielding, not the yielding
mostly internal to the spoke that Jobst thinks is important.

If I may go on a bit of a tangent, I think jim beam's position in this
discussion may be at odds with one he took in an earlier thread. In a
discussion of Sapim's fatigue testing, he suggested that butted spokes
have longer fatigue lives because the flexible mid-section exerts less
bending moment at the elbows. He said that's true even when the spoke is
largely immobilized by conforming closely to the hub flange. Again, I
haven't followed this discussion closely, but jim beam seems to be
dismissing the efficacy of effects that aren't obvious to the unaided
eye. By contrast, his earlier bending-moment explanation seems to rely on
forces of the same scale.

>
> Fourth, the tension of all the spokes and the rim might somehow be
> re-arranged without changing the sum. Nothing yields, the total tension
> doesn't change, but the rim changes shape--this section bends a little
> to one side, but another section bends exactly enough to the other side
> to compensate.
>
> (I think that's what you're suggesting, but I may be wrong.)
>
> Cheers,
>
> Carl Fogel
 
G

Gary Young

Guest
On Sun, 18 Mar 2007 00:56:24 -0500, Gary Young wrote:

> On Sat, 17 Mar 2007 20:42:04 -0700, carlfogel wrote:
>
>> On Sat, 17 Mar 2007 16:46:41 -0500, Ben C <[email protected]> wrote:
>>
>>>On 2007-03-17, [email protected] <[email protected]> wrote:
>>>> On 17 Mar 2007 20:04:39 GMT, [email protected] wrote:
>>>>
>>>>>Carl Fogel writes:
>>>[...]
>>>>>> Squeezing spoke pairs together usually changes something enough to
>>>>>> require small truing adjustments:
>>>>>
>>>>>> "If, after stress relieving, the wheel is appreciably out of true
>>>>>> in two smooth waves, then tension was too high, and retruing should
>>>>>> begin by relaxing tension of all spokes half a turn. Usually, only
>>>>>> small lateral corrections will be necessary after stress
>>>>>> relieving."
>>>>>
>>>>>> --"The Bicycle Wheel," 3rd edition, p. 106
>>>>>
>>>>>I find that is a misinterpretation. The above citation explains what
>>>>>occurs if spoke tension it too high, not what stress relieving does.
>>>>>The issue at hand is whether spokes must be re-tensioned after stress
>>>>>relieving. The above mentions retruing, not re-tensioning. Spokes
>>>>>do not require re-tensioning!
>>>[...]
>>>> Dear Jobst,
>>>>
>>>> "Usually, only small lateral corrections will be necessary after
>>>> stress relieving."
>>>>
>>>> What is the difference between turning a spoke nipple to laterally
>>>> true a rim and turning a spoke nipple to change the spoke tension?
>>>
>>>The difference is in the intention. In one case you adjust one or two
>>>spokes to make the wheel true; in the other you adjust them all to
>>>change the wheel's tension.
>>>
>>>We still make distinctions between radial truing, lateral truing,
>>>tensioning and dishing, even though they all consist of turning the
>>>nipples.
>>>
>>>(Conversely, bashing the wheel on a tree-trunk, walking on it,
>>>squeezing it, leaning on it and mangling it with a crowbar are all
>>>called the same thing: "stress-relief").
>>>
>>>If stress-relief reduced whole-spoke tension significantly you'd expect
>>>to have to tighten up all the spokes by a bit to compensate, since you
>>>have stress-relieved all of them. That it may affect the tension of one
>>>or two enough to require a bit of re-truing just reflects the fact that
>>>nothing's perfect.

>>
>> Dear Ben,
>>
>> Why do sections of the rim move laterally enough to need truing after
>> spoke pairs are squeezed?
>>
>> I can think of four possible reasons, any or all of which may be
>> involved.
>>
>> First, the rim may not actually change. It could be that the wheel
>> builder tensions and trues the wheel up, squeezes all the spoke pairs,
>> gives the wheel a spin, and just can't help himself--the wheel hasn't
>> actually changed, but it can always be trued a little here or there.
>> This would be perfectly understandable, nothing dishonest.
>>
>> (For all I know, the lateral movement is so gross and obvious to
>> experienced wheel builders that this psychological explanation can be
>> dismissed. I haven't enough confidence in my truing and tensioning to
>> have an opinion one way or the other.)

>
> I think you have to draw a distinction between two kinds of lateral
> movement. Ordinarily, out-of-trueness is asymmetrical -- you may have
> one high-spot at 3 o'clock, and another at 5 o'clock, or 6 or 7, or at
> some other arbitrary point.
>
> However, there's a different kind of out-of-trueness that occurs when
> the spoke tension is so high that stress relieving raises the tension
> above the level that the rim can bear. See page 105: "Stress relieving
> ... increases tension enough to overload the rim if the spokes are too
> tight." If I understand things correctly, the rim is actually on the
> threshold of buckling. As in buckling or potato-chipping, "two large
> waves" appear.
>
> That second kind of out-of-trueness is in fact "gross and obvious"
> because the two waves are symmetrical. There will be high spots at 12
> and 6 o'clock and low spots at 3 and 9 o'clock. I usually use heavier
> rims (e.g., Sun CR-18s), so the amplitude of the waves is small, but
> they are large and unmistakable in that each covers half the rim.
>
> The second kind of out-of-trueness indicates that the spokes are
> dangerously tight and Jobst recommends that every spoke be loosened half
> a turn and that no more tensioning be done (except small increases here
> and there to eliminate asymmetrical out-of-trueness and to equalize
> tension among the spokes).
>
> (I don't quite understand why the two waves don't disappear after one
> stops squeezing spoke pairs. I'm guessing that passing the threshold
> into buckling is such a major transition that only fairly gross changes
> can reverse it.)
>
> I sometimes get asymmetrical out-of-trueness after stress-relieving. I
> think the main cause is that I haven't been entirely successful in
> eliminating windup. A byproduct of stress relieving (but not its main
> purpose) is to release the windup, thus causing the rim to go out of
> true.
>
> I think these effects are distinct enough that "the wheelbuilder is
> fooling himself" can be eliminated as an explanation.
>
>
>> Second, some piece of metal may actually change. The rim, socket,
>> eyelet, nipple, spoke, or hub could yield here or there, which would
>> cause the rim to need some lateral truing.
>>
>> (That's the point that I think is being debated here.)

>
> I don't think so. I think you're conflating two different things. Even
> jim beam, who thinks that stress relieving causes yielding that leads to
> out-of-trueness, would -- I believe -- say that the yielding occurs only
> in the hub and perhaps the rim as the steel spokes bite into aluminum.


Carl,
I just know you're going to accuse me of not reading you very closely.
Let me spare you the trouble -- you're right, to an extent. I think my
comments have merit, but aren't always clear in how they respond to your
points.

What I should have said here is that I think you obscure the debate by
running all types of yielding together ("rim, socket, eyelet, nipple,
spoke, or hub"). It's not clear to me whether you recognize that both
sides think some kind of yielding is going on, though only jim beam
thinks that yielding leads to changes in alignment.

>
> As I understand it, yielding plays no part in Jobst's explanation of why
> stress-relieving produces out-of-trueness.
>
> In Jobst's view, stress-relieving does lead to yielding, but it occurs
> at the elbows and threads in movements so small (indeed, movements
> mostly internal to the spoke) that there's no appreciable effect on rim
> alignment.
>
> To sum up:
>
> jim beam -- there's no yielding at the elbow and threads (or at least no
> yielding that would lead to the relief of residual stress). However,
> there is yielding, in the form of bedding-in, that causes changes in rim
> alignment.
>
> Jobst -- The purpose of stress relieving is to produce yielding of a
> small magnitude at the elbows and threads, thus relieving residual
> stress. As a byproduct, stress relieving sometimes produces changes in
> rim alignment that are caused by increases in tension and not yielding.
>
>
>> Third, the rim may be able to move laterally without any metal yielding
>> on a cross-X laced wheel. When spoke pairs are squeezed, there may be
>> no noticeable yielding of the kind that would let the rim move from
>> side to side--but the crossings could shift slightly to a new position,
>> adding or reducing tension.
>>

> I haven't been following this discussion very closely, but who, other
> than yourself, suggests that spoke crossings play a role here? I don't
> see why it's necessary to add that to the mix.
>
>
>> If two spokes were stuck at the crossing and squeezing them unstuck
>> them, then their tension would be slightly reduced and the rim would
>> move away from their side of the hub.
>>
>> (No yielding is involved here, just the stubborn friction of crossed
>> spokes. But the overall tension changes.)

>
> Again, I think you're overlooking changes in alignment that occur as a
> byproduct of stress-relieving but that aren't caused by yielding of the
> elbows and threads -- i.e., by taking the rim beyond its safe limit or
> releasing windup.
>
> Its true that jim beam thinks that changes in alignment occur through
> yielding, but it's the bedding-in kind of yielding, not the yielding
> mostly internal to the spoke that Jobst thinks is important.
>


I should have been more explicit that I don't think spoke crossings play
a part on either side of the debate.

> If I may go on a bit of a tangent, I think jim beam's position in this
> discussion may be at odds with one he took in an earlier thread. In a
> discussion of Sapim's fatigue testing, he suggested that butted spokes
> have longer fatigue lives because the flexible mid-section exerts less
> bending moment at the elbows. He said that's true even when the spoke is
> largely immobilized by conforming closely to the hub flange. Again, I
> haven't followed this discussion closely, but jim beam seems to be
> dismissing the efficacy of effects that aren't obvious to the unaided
> eye. By contrast, his earlier bending-moment explanation seems to rely
> on forces of the same scale.
>
>
>> Fourth, the tension of all the spokes and the rim might somehow be
>> re-arranged without changing the sum. Nothing yields, the total tension
>> doesn't change, but the rim changes shape--this section bends a little
>> to one side, but another section bends exactly enough to the other side
>> to compensate.


Is this a summary of the two waves explanation? If so, I think you've
left out the important point that a temporary increase in tension causes
them to appear.

>>
>> (I think that's what you're suggesting, but I may be wrong.)
>>
>> Cheers,
>>
>> Carl Fogel
 
B

Ben C

Guest
On 2007-03-18, [email protected] <[email protected]> wrote:
> On Sat, 17 Mar 2007 16:46:41 -0500, Ben C <[email protected]> wrote:

[...]
>>If stress-relief reduced whole-spoke tension significantly you'd expect
>>to have to tighten up all the spokes by a bit to compensate, since you
>>have stress-relieved all of them. That it may affect the tension of one
>>or two enough to require a bit of re-truing just reflects the fact that
>>nothing's perfect.

>
> Dear Ben,
>
> Why do sections of the rim move laterally enough to need truing after
> spoke pairs are squeezed?


Good question. I suspect it's because some of the spokes plastically
bend a bit and perhaps the hub squishes a bit, and so some spokes shift
position slightly. It only takes a small error to prompt lateral
retruing, especially if you're a perfectionist. In theory plastic spoke
bending and hub squishing is supposed to have all happened by now, so
the wheel should be quite resilient against further deformation, but
nothing's perfect. Getting those last few spokes firmly in place is a
good thing, and this may be one of the beneficial sideffects of the
stress relief process.

> I can think of four possible reasons, any or all of which may be
> involved.
>
> First, the rim may not actually change. It could be that the wheel
> builder tensions and trues the wheel up, squeezes all the spoke pairs,
> gives the wheel a spin, and just can't help himself--the wheel hasn't
> actually changed, but it can always be trued a little here or there.
> This would be perfectly understandable, nothing dishonest.


Certainly possible.

> (For all I know, the lateral movement is so gross and obvious to
> experienced wheel builders that this psychological explanation can be
> dismissed. I haven't enough confidence in my truing and tensioning to
> have an opinion one way or the other.)


Some of them have truing stands with special dials and gauges on them
that can tell them quite scientifically the sizes of the errors. I use a
postcard held against the side of the rim.

> Second, some piece of metal may actually change. The rim, socket,
> eyelet, nipple, spoke, or hub could yield here or there, which would
> cause the rim to need some lateral truing.


Exactly.

> (That's the point that I think is being debated here.)


The original question was does the spoke get slightly longer after ideal
stress-relief. Never mind for now the other effects and sideeffects that
stress-relief might have. The effect it's supposed to have, according to
Jobst's theory, is to yield small parts of the cross section by a small
amount. It it not supposed to affect the length or shape of the spoke
significantly. We have got that clarified.

In practice however, stress relief may cause more significant
deformations. If Jobst finds he usually only needs to make small lateral
adjustments, it may well be because he's already got a good spoke line
and tensioned the wheel to quite a high tension before stress-relieving.
This would be expected to reduce the chance that stress-relief would
cause significant changes in wheel geometry. Other builders may have
other results.

Note: if you are having to do a lot of retruing or any retensioning
after stress relief I think you're back to square one and should stress
relieve again afterwards. Repeat until stress-relief becomes effectively
idempotent.

> Third, the rim may be able to move laterally without any metal
> yielding on a cross-X laced wheel. When spoke pairs are squeezed,
> there may be no noticeable yielding of the kind that would let the rim
> move from side to side--but the crossings could shift slightly to a
> new position, adding or reducing tension.


An interesting suggestion. You'd be relying on "stiction" at the
crossings to maintain the new position. I wouldn't have thought there
would be enough force, but I don't know. Perhaps we should lube the
crossings as well!

> If two spokes were stuck at the crossing and squeezing them unstuck
> them, then their tension would be slightly reduced and the rim would
> move away from their side of the hub.


This sounds like it could happen though. You'd expect the Mavic method
to free up stubborn crossings on the side that's going slack.

> (No yielding is involved here, just the stubborn friction of crossed
> spokes. But the overall tension changes.)
>
> Fourth, the tension of all the spokes and the rim might somehow be
> re-arranged without changing the sum. Nothing yields, the total
> tension doesn't change, but the rim changes shape--this section bends
> a little to one side, but another section bends exactly enough to the
> other side to compensate.


The rim might actually bend, but if so I suspect the builder is being a
bit too aggressive with his stress relieving.

> (I think that's what you're suggesting, but I may be wrong.)


I think elbow bending and hub hole deformation are the most likely
candidates. Any elbow that's sticking out will bend quite easily if the
spoke is overloaded, and then that spoke will end up with lower tension;
but it will happen to only one or two elbows in the wheel which is why
you usually need lateral truing and not general retensioning. As for hub
holes, if stress relief pulls them from a slightly new angle you may get
a change in the deformation-- the hole may spread or shift a bit,
resulting in a slightly different spoke line.

A further possibility is that spoke squeezing causes some plastic
bending at the nipples, especially if you're a bit rough with it.
 
On Sat, 17 Mar 2007 20:48:01 -0500, Tim McNamara
<[email protected]> wrote:

>
>I didn't mention Jobst. Jobst's writing is often not in very plain
>English, in fact.
>
>> utter ****-sucking ********.

>
>You are merely vulgar now.
>




>> >
>> >> you're utterly innumerate.
>> >
>> > Not utterly, no.

>>
>> > I can do arithmetic, basic algebra and have a good
>> > understanding of statistics (since that applies directly to my
>> > field of science, it was required in graduate school). I have
>> > never had a need to learn advanced mathematics so I can't do that
>> > stuff, and as a result can't always follow Luns's math. From what
>> > you've posted it looks like you can't follow it either. In fact,
>> > come to think of it, your participation pretty much disappears when
>> > the heavy math comes out. What's up with that? Perhaps you are
>> > not as numerate as you pretend.

>>
>> yeah, i'm a real dumb-ass. and a photo fraud. and you're real
>> useful with all those fine technical contributions you make. go back
>> to the bedroom brown-nose. your master awaits.

>


Tim, remember:

Insults are a sign that the person using them has nothing else to
support his assertions.

On this newsgroup there are three crazies, all with agendas, all who
use insult when the logical fallacies are pointed out to them.

You've found one.
 
T

Tim McNamara

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

> Tim, remember:
>
> Insults are a sign that the person using them has nothing else to
> support his assertions.
>
> On this newsgroup there are three crazies, all with agendas, all who
> use insult when the logical fallacies are pointed out to them.
>
> You've found one.


Yes, you are quite correct in your assessment. Although there are some
who would say that I too belong in the group of crazies. Perhaps there
are four... :)
 
On Sun, 18 Mar 2007 10:11:12 -0500, Tim McNamara
<[email protected]> wrote:

>In article <[email protected]>,
> [email protected] wrote:
>
>> Tim, remember:
>>
>> Insults are a sign that the person using them has nothing else to
>> support his assertions.
>>
>> On this newsgroup there are three crazies, all with agendas, all who
>> use insult when the logical fallacies are pointed out to them.
>>
>> You've found one.

>
>Yes, you are quite correct in your assessment. Although there are some
>who would say that I too belong in the group of crazies. Perhaps there
>are four... :)


I haven't noticed you employing insult...
 
B

Ben C

Guest
On 2007-03-17, [email protected] <[email protected]> wrote:
> in group two:
> the wheel radii vary following stress relief-1/4 turn is not unusually
> hi.
> does increased spoke breaking tension then occur
> yep! generic spokes do not spring back after the first road test, a
> few are permanently bent.
> and *&^%&^$$$ 2-3 of the little 8&^%^%##$3 could fail at the hub
> during the second road test.


My suggestion is:

1. Tension
2. Stress-relieve
3. If retensioning is necessary, go back to step 1.
4. Put wheel on bike, ride off and forget about it.

But I think I have an easy life compared to you because I don't carry a
lot of weight on the bike.
 
T

Tim McNamara

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

> Tim McNamara wrote:
> > In article <[email protected]>,
> > jim beam <[email protected]> wrote:
> >
> >> Tim McNamara wrote:
> >>> In article <[email protected]>,
> >>> jim beam <[email protected]> wrote:
> >>>
> >>>> really? so is 1600N > 5000N?
> >>>
> >>> Nope. But you can't guarantee that the right side of that
> >>> expression is 5000N.
> >>>
> >> pfffffft!!!! i just choked soup up my nose. it hurts!

> >
> > I'm sorry to hear that. I hope you're feeling better.
> >
> >>> That's the part you kept dancing around. Your entire position
> >>> is posited on the assumption- rather than a fact- that the right
> >>> side of the equation is necessarily higher than the left side.
> >>> It's a foundation of sand.
> >>>
> >> so you /are/ innumerate. what a freakin' joke.

> >
> > Nope. But you have once again conflated your opinions with reality
> > and I am certainly wondering about your ability to comprehend what
> > is really quite simple math. You make the assumption that the
> > retention force will never be less than 5000N. But that is not a
> > reasonable assumption to make. There are multiple potential
> > reasons for the retention force to be below 5000N. On top of that,
> > you've plucked "1600N" out of thin air since it's already been
> > shown that the ejection force can easily exceed 2100N (which is
> > concentrated on one dropout, so that's an equivalent of more than
> > 4200N pulling on the wheel). That is not a particularly
> > comfortable margin of safety. What if the retention force is only
> > 4000N? Now the ejection force exceeds the retention force.
> >
> > Since the ejection force can be easily eliminated with a change in
> > the geometry of the braking system, the logical conclusion is that
> > correcting the faulty design is a good idea. That should be easy
> > enough for you to understand, unless you persist on conflating your
> > opinion with facts.

>
> that's it timmy boy, try to move on to the statements /you/ didn't
> make. and fyi, rehashing the mistakes of others doesn't somehow make
> them any less invalid. but i'd guess you'd need to understand them
> to follow that argument.


Sorry, I missed this one when I wrote my other reply to your post. Here
again we see that you distort and lie in your efforts to "win." I have
made all these statements before on multiple occasions starting in 2003.
 
T

Tim McNamara

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

> On Sun, 18 Mar 2007 10:11:12 -0500, Tim McNamara
> <[email protected]> wrote:
>
> >In article <[email protected]>,
> > [email protected] wrote:
> >
> >> Tim, remember:
> >>
> >> Insults are a sign that the person using them has nothing else to
> >> support his assertions.
> >>
> >> On this newsgroup there are three crazies, all with agendas, all
> >> who use insult when the logical fallacies are pointed out to them.
> >>
> >> You've found one.

> >
> >Yes, you are quite correct in your assessment. Although there are
> >some who would say that I too belong in the group of crazies.
> >Perhaps there are four... :)

>
> I haven't noticed you employing insult...


I have in the past been, shall we say, immoderate in expressing my
opinion about jim. I have long had a tendency to shoot from the lip
which I have mostly gotten over in my personal life but have not always
practiced such temperance in my online life. I have been cautioned
back-channel on this by several level-headed people and have tried to
take their advice to heart. That jim is wrong on several points, and
tenaciously so, is no reason to be insulting and rude to him. His
insults, rudeness and invective really only demean himself. I have been
making a point of reining in my language, and your post suggests to me
that I have had some success in this thread. Thanks for your feedback.
 
Carl Fogel writes:

> Why do sections of the rim move to new lateral positions when spokes
> are squeezed?


Looking at the angles involved might reveal more clearly what is
happening to wheel alignment. The lateral spoke angles involved are
on the order of 6° the sine of which is about0.1 and the cosine 0.994.
So for a lateral error of +-1mm (sine) it takes 0.1mm (0.004") length
change. Most of this would probably be yielding in an aluminum flange
if it were that large. I usually need to make no adjustments after
stress relieving.

> As for my silence, consider how tactful it was and how foolish it is
> to keep whining about this:


> http://groups.google.com/group/rec.bicycles.tech/msg/530db1a52761ea77


> Or this:


> http://groups.google.com/group/rec.bicycles.tech/msg/3888013418502011


You didn't say what it was that you found rude and inappropriate in
those replies. I see no aspersions to character faults or rude
comments about intelligence. I asked the writer to show why he
offered the certain advice to the subject. If you think that is rude,
I find you acquiescing in truly rude postings odd.

> I understand that it rankles to have your bad manners pointed out on
> the newsgroup, but waving your arms and pointing at the other children
> only draws attention to something everyone else was willing to drop.


You keep alluding to unspecified bad manners. Just referring to a
couple of sentences and saying so doesn't clarify what you find there.
I believe you have a biased perspective to the use of civil discourse.

> Feel free to write directly to Jim Beam, just as I wrote directly to
> you. I doubt that it will do any good, since he and Tim McNamara are
> engrossed in their familiar squabble.


He gives no email address... or name other than an alias. By the way,
your misspelling of his alias is rude and inappropriate.

Jobst Brandt
 

daveornee

New Member
Sep 18, 2003
2,763
0
0
<SNIP> Lateral bending
strength of deep aero rims, that can bridge large spoke-to-spoke
distances for vertical loads, is not significantly higher than
rectangular cross section rims, their width being the same.

<SNIP>
Jobst Brandt

Can you explain more of what you mean here?
Are you talking about 19 mm wide 21mm tall rim (as an example of a regular cross section rim) having the not significantly higher lateral bending strength as a 19 mm wide 30 mm (as an example of not a very deep aero section) rim when built into a wheel?
I will wait for your explanation before jumping the conclusions, but I would like you answer to include how spoke support angle plays into this as well as other factors of physics. I also would like if you can include in the explanation lateral strength Vs. laternal stiffness in this context.
If this is old hat, you can just point me to the r.b.t. thread that covers it or a section of your book so as not to spend unneeded bandwidth here.
 
Dave Ornee writes:

>> <SNIP> Lateral bending strength of deep aero rims, that can bridge
>> large spoke-to-spoke distances for vertical loads, is not
>> significantly higher than rectangular cross section rims, their
>> width being the same.


> Can you explain more of what you mean here?


> Are you talking about 19 mm wide 21mm tall rim (as an example of a
> regular cross section rim) having the not significantly higher
> lateral bending strength as a 19 mm wide 30 mm (as an example of not
> a very deep aero section) rim when built into a wheel?


The radial depth of, for instance, an MA-2 is 1/3 that if a typical
aero rim (over 40mm) (for which we need to buy inner tubes with extra
long valve stems).

> I will wait for your explanation before jumping the conclusions, but
> I would like you answer to include how spoke support angle plays
> into this as well as other factors of physics.


I don't know what you mean by "spoke support angle". Spokes come in
pairs both laterally and circumferentially so their angles are
balanced. This concerns radial loading. The depth of an aero rim
furnishes bridging strength, the bending strength of a bean going as
the third power of its depth.


Jobst Brandt
 
"So for a lateral error of +-1mm (sine) it takes 0.1mm (0.004")
length
change. Most of this would probably be yielding in an aluminum
flange
if it were that large. I usually need to make no adjustments after
stress relieving. "

well, again down here in group 2, not only are my spokes at a lower
torque level than group 1 but the average variation of 36 ( on a good
day) spoke's torque gotta be hmmmm 15% greater than group 1.

Now, I realize that somewhere ahead lies a plateua where the spokes
running on my bent rims will close in to say an average 5% torque
difference.

but you can bet a dead squirrel i'm not gonna hold my breath on it.
 

daveornee

New Member
Sep 18, 2003
2,763
0
0
Dave Ornee writes:

>> <SNIP> Lateral bending strength of deep aero rims, that can bridge
>> large spoke-to-spoke distances for vertical loads, is not
>> significantly higher than rectangular cross section rims, their
>> width being the same.


> Can you explain more of what you mean here?


> Are you talking about 19 mm wide 21mm tall rim (as an example of a
> regular cross section rim) having the not significantly higher
> lateral bending strength as a 19 mm wide 30 mm (as an example of not
> a very deep aero section) rim when built into a wheel?


The radial depth of, for instance, an MA-2 is 1/3 that if a typical
aero rim (over 40mm) (for which we need to buy inner tubes with extra
long valve stems).

> I will wait for your explanation before jumping the conclusions, but
> I would like you answer to include how spoke support angle plays
> into this as well as other factors of physics.


I don't know what you mean by "spoke support angle". Spokes come in
pairs both laterally and circumferentially so their angles are
balanced. This concerns radial loading. The depth of an aero rim
furnishes bridging strength, the bending strength of a bean going as
the third power of its depth.


Jobst Brandt
"Spoke support angle" = Spoke bracing angle.
I don't know what you mean by "their angles are
balanced". This isn't of particular interest to me, but I sure don't see that in the angles of spokes left Vs. right in rear wheels. I understand that the force vectors must be balanced.
It is my understanding that:
1. The bracing angle or "spoke support angle" increases as the height of the rim increases.
2. The higher the "spoke support angle" the stiffer the wheel latterally; all other things being equal.

Please provide a couple of examples of "the bending strength of a bean going as the third power of its depth."
I would find it helpful if you used the MA-2 and the 40 mm deep aero rim you suggest in your earlier statement.
 
no problem: the wheel and spokes and iron truss bridge are
geometrically perfcet mroe or les!
that is structural element A1=A2=A3..., B1=B2=B3..., X1=X2=X3... angle
A1=angleA2=...ad nauseum
to achieve optimum structural properties such as strength, stiffness,
and whatever.

the concept "higher" rims or wheels possess greater lateral "strength"
than "lower" wheels or rims is a loser at this end: the opposite, no?
or are you talkin wider hubs?
 

daveornee

New Member
Sep 18, 2003
2,763
0
0
no problem: the wheel and spokes and iron truss bridge are
geometrically perfcet mroe or les!
that is structural element A1=A2=A3..., B1=B2=B3..., X1=X2=X3... angle
A1=angleA2=...ad nauseum
to achieve optimum structural properties such as strength, stiffness,
and whatever.

the concept "higher" rims or wheels possess greater lateral "strength"
than "lower" wheels or rims is a loser at this end: the opposite, no?
or are you talkin wider hubs?
If you were trying to help me understand, it isn't working for me. Maybe I need to be referred to an Engineering text book with pictures.
To answer your question (which I guess that you meant to be obvious) to me: is not in my understanding or observations. I might add that Damon Rinard doesn't conclude or measure that either. See his information on wheel stiffness:
http://www.sheldonbrown.com/rinard/wheel/index.htm
Lots of other conclusions, but the last in order of his listing:
"Relative contribution of the following to stiffness:
number of spokes
spoke gauge
rim weight
hub flange spacing
rim height "
 
Dave Ornee writes:

>>>> <SNIP> Lateral bending strength of deep aero rims, that can bridge
>>>> large spoke-to-spoke distances for vertical loads, is not
>>>> significantly higher than rectangular cross section rims, their
>>>> width being the same.


>>> Can you explain more of what you mean here?


>>> Are you talking about 19 mm wide 21mm tall rim (as an example of a
>>> regular cross section rim) having the not significantly higher
>>> lateral bending strength as a 19 mm wide 30 mm (as an example of not
>>> a very deep aero section) rim when built into a wheel?


>> The radial depth of, for instance, an MA-2 is 1/3 that if a typical
>> aero rim (over 40mm) (for which we need to buy inner tubes with extra
>> long valve stems).


>>> I will wait for your explanation before jumping the conclusions, but
>>> I would like you answer to include how spoke support angle plays
>>> into this as well as other factors of physics.


>> I don't know what you mean by "spoke support angle". Spokes come in
>> pairs both laterally and circumferentially so their angles are
>> balanced. This concerns radial loading. The depth of an aero rim
>> furnishes bridging strength, the bending strength of a bean going as
>> the third power of its depth.


> "Spoke support angle" = Spoke bracing angle. I don't know what you
> mean by "their angles are balanced". This isn't of particular
> interest to me, but I sure don't see that in the angles of spokes
> left Vs. right in rear wheels. I understand that the force vectors
> must be balanced.


For rear wheels with offset, spoke tension is different for left and
right sides by the sine of the angle.

> It is my understanding that:


> 1. The bracing angle or "spoke support angle" increases as the height
> of the rim increases.


There is no connection between the two parameters. Only thew radial
distance from hub to spoke end in the rim affects that angle and the
percentage difference over the length of a spoke is small. I still do
not see what you are proposing.

> 2. The higher the "spoke support angle" the stiffer the wheel
> latterally; all other things being equal.


As I said, that goes as the sine of the angle and that is a small
number. Far more significant is the number of spokes (or their
density per lineal length of rim).

> Please provide a couple of examples of "the bending strength of a bean
> going as the third power of its depth."


The equation is (b*h^3)/12 and is reviewed on various web sited:

http://www.engineersedge.com/calculators/section_square.htm
http://pergatory.mit.edu/2.007/Resources/calculations/bending/bending.html

> I would find it helpful if you used the MA-2 and the 40 mm deep aero
> rim you suggest in your earlier statement.


What earlier statement and what is it that is unclear?

Jobst Brandt