removing broken spoke nipples

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daveornee

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Sep 18, 2003
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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
The earlier statement " 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" was the one that I was questioning.
I didn't say that it was unclear, I just don't agree with it.

To extend my point (possibly to ad nauseum), spoke holes on a 40 mm deep rim are closer together than your MA-2 for the same spoke count), spokes are shorter, spoke support angle is greater (yes I agree they are all by small amounts), but when combined with a rim that has 3 times the h (from the equation) I come to a different conclusion.
The lateral bending strength difference, at least to me, *is* significantlyl different.
 
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
>>> beam 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://tinyurl.com/29z66f

>>> 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?


> The earlier statement " 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" was the one that I was questioning.


> I didn't say that it was unclear, I just don't agree with it.


> To extend my point (possibly to ad nauseam), spoke holes on a 40 mm
> deep rim are closer together than your MA-2 for the same spoke
> count), spokes are shorter, spoke support angle is greater (yes I
> agree they are all by small amounts), but when combined with a rim
> that has 3 times the h (from the equation) I come to a different
> conclusion. The lateral bending strength difference, at least to
> me, *is* significantly different.


If the rim is the same width, it has essentially the same bending
strength for the same wall thickness, its widest part (where it
derives its lateral bending strength) being the same as a non-aero
rim. Spoke spacing is angularly the same for the same number of
spokes, only the length changes by about 20mm out of 300mm. I think
this is grasping at straws because these wheels generally have far
fewer spokes as well.

I'm not understanding what your are pursuing in this
pin-the-tail-on-the-donkey exchange. I'm unclear about what you are
trying to assess.

Jobst Brandt
 
Carl Fogel writes:

> Instead of waving your arms and whining for sympathy, you should:


Now you are getting rude. This characterization of my question is
stretching decorum of which you approve beyond reasonable limits. I
do not use such language in responses as you may have noticed.

> a) Learn to address Jim Beam directly, just as I addressed you
> directly by replying to your obnoxious post, instead of squirting ink
> about not having his email address. If you haven't the courage to
> address him directly in this thread about what troubles you, why ask
> me to do it for you?


Are you jim beam's alter ego? You too are getting ruder with each
response just as he has descended into crude street language. Calling
people obnoxious is not what I expect in these responses. What is it
that irks you to the degree of losing you "Dear reader" courtesy?

> b) Learn to distinguish between spelling and capitalization--your
> quibbling is as inaccurate and trifling as ever and is presumably
> meant to conceal the familiar lack of content.


> Cheers,


> e.e. cummings


The parallel with jim beam and cummings doesn't ring well. I'm sure
cummings did not use scatological and sexual innuendo in the manner to
which we are being subjected in reading this thread.

Jobst Brandt
 
ok. the rim is road weary with bumps, lumps, dents. In group two wheel
building/tuning, those imperfections result in spoke triangles as
positions/torques and overall, most important, the relationship of the
wheel's seperable parts are unequal: the unequalness reduces the
wheel's capacities as the sum of the parts.
Achieving full design capacity for the truss entails a fairly even
distribution of unequal elements: haha an ugly a phrase as today i'll
write.
yeah-all the parts need be the same in all respects. its simple right
"the chain is only as strong as what?"

the angle/height bit is less clear as i can make assumptions based on
so called observed wire wheel properties from TC to AH 3000 to
xk-120/150 to the bicycle and frankly it doesn't mean nothing. I can
visualize what I think is happening based on sizes and performance
levels but its not an engineering spec understanding. to think that a
visual familiarity with increases/decreases in width/height from hub
and or rim and the proportions thereof give an accurate understanding
of lesser or greater strengths may not be true according to what jb
tells us. ??
 
On 18 Mar 2007 19:34:16 GMT, [email protected] wrote:

>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


Dear Jobst,

Instead of waving your arms and whining for sympathy, you should:

a) Learn to address Jim Beam directly, just as I addressed you
directly by replying to your obnoxious post, instead of squirting ink
about not having his email address. If you haven't the courage to
address him directly in this thread about what troubles you, why ask
me to do it for you?

b) Learn to distinguish between spelling and capitalization--your
quibbling is as inaccurate and trifling as ever and is presumably
meant to conceal the familiar lack of content.

Cheers,

e.e. cummings
 
M

Michael Press

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

> On 18 Mar 2007 19:34:16 GMT, [email protected] wrote:
>
> >Carl Fogel writes:


[...]

> >> 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.

>
> Instead of waving your arms and whining for sympathy, you should:
>
> a) Learn to address Jim Beam directly, just as I addressed you
> directly by replying to your obnoxious post, instead of squirting ink
> about not having his email address. If you haven't the courage to
> address him directly in this thread about what troubles you, why ask
> me to do it for you?
>
> b) Learn to distinguish between spelling and capitalization--your
> quibbling is as inaccurate and trifling as ever and is presumably
> meant to conceal the familiar lack of content.
>
> Cheers,
>
> e.e. cummings


e.e. cummings always capitalized proper names except for
his own. jim beam insists on using minuscule for all
proper names. You inappropriately capitalize jb's alias.
Using minuscule on proper names is misspelling, and
ill-mannered when deliberate; except when it is one's own
proper name.
--
Michael Press
 

daveornee

New Member
Sep 18, 2003
2,763
0
0
<SNIP>

If the rim is the same width, it has essentially the same bending
strength for the same wall thickness, its widest part (where it
derives its lateral bending strength) being the same as a non-aero
rim. Spoke spacing is angularly the same for the same number of
spokes, only the length changes by about 20mm out of 300mm. I think
this is grasping at straws because these wheels generally have far
fewer spokes as well.

I'm not understanding what your are pursuing in this
pin-the-tail-on-the-donkey exchange. I'm unclear about what you are
trying to assess.

Jobst Brandt
I already made my assessment. It is clear to me that it is unclear to you.
I agree to disagree in what is significant to me and not significant to you.
 
T

Tim McNamara

Guest
daveornee <[email protected]> wrote:
> >

> The earlier statement " 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" was the one that I was questioning. I didn't
> say that it was unclear, I just don't agree with it.
>
> To extend my point (possibly to ad nauseum), spoke holes on a 40 mm
> deep rim are closer together than your MA-2 for the same spoke
> count), spokes are shorter, spoke support angle is greater (yes I
> agree they are all by small amounts), but when combined with a rim
> that has 3 times the h (from the equation) I come to a different
> conclusion. The lateral bending strength difference, at least to me,
> *is* significantlyl different.


Dave, are you asking if- all other things being equal- a tall aero rim
(say, 40 mm tall) is laterally stiffer than a "standard" rim like an MA2
(which is what, 15 mm tall)?

The taller rim would be significantly stiffer radially, it seems to me,
since it is just a thicker beam in that direction. In the lateral
direction, the aero rim is not a thicker beam but it is a wider beam.
Seems to me that would offer some increase in stiffness in theory.
Whether the difference would be significant to the operation of the
wheel vis-a-vis load bearing is a different question (since bicycle
wheels bear little lateral load except in unusual circumstances such as
skidding sideways). The lateral stiffness of the whole wheel is
affected not only by the stiffness of the rim but also by the spokes,
thicker spokes resulting in a laterally stiffer wheel if I remember
Damon Rinard's conclusion from his measurements correctly. ISTR spoke
tension being a relatively small factor in lateral stiffness.
 
B

Ben C

Guest
On 2007-03-19, Tim McNamara <[email protected]> wrote:
> daveornee <[email protected]> wrote:
>> >

>> The earlier statement " 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" was the one that I was questioning. I didn't
>> say that it was unclear, I just don't agree with it.
>>
>> To extend my point (possibly to ad nauseum), spoke holes on a 40 mm
>> deep rim are closer together than your MA-2 for the same spoke
>> count), spokes are shorter, spoke support angle is greater (yes I
>> agree they are all by small amounts), but when combined with a rim
>> that has 3 times the h (from the equation) I come to a different
>> conclusion. The lateral bending strength difference, at least to me,
>> *is* significantlyl different.

>
> Dave, are you asking if- all other things being equal- a tall aero rim
> (say, 40 mm tall) is laterally stiffer than a "standard" rim like an MA2
> (which is what, 15 mm tall)?
>
> The taller rim would be significantly stiffer radially, it seems to me,
> since it is just a thicker beam in that direction. In the lateral
> direction, the aero rim is not a thicker beam but it is a wider beam.
> Seems to me that would offer some increase in stiffness in theory.


It's not really a beam, more of a hollow box-section. I don't know what
difference that makes. I would expect that the stiffness of a
box-section would be even less affected by increasing its width in the
"wrong" dimension than a beam.

> Whether the difference would be significant to the operation of the
> wheel vis-a-vis load bearing is a different question (since bicycle
> wheels bear little lateral load except in unusual circumstances such as
> skidding sideways).


There is a real puzzle here. To summarize the argument: a radially stiff
rim means we can get away with fewer spokes to support the radial load.
But if the rim isn't stiffer laterally, which we expect it not to be
from looking at its shape, then the wheel might be prone to collapse
under lateral loads.

The reasoning seems sound, but I've never heard of this collapse
actually happening with a 16-spoke wheel. Two possibilities: either it
is less stiff, but it doesn't matter, because lateral loads are small
anyway; or the rims are stiffer laterally as well as radially in spite
of not being any wider (different materials, changes in the way they're
braced internally perhaps, etc.).
 

daveornee

New Member
Sep 18, 2003
2,763
0
0
Tim McNamara said:
daveornee <[email protected]> wrote:
> >

> The earlier statement " 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" was the one that I was questioning. I didn't
> say that it was unclear, I just don't agree with it.
>
> To extend my point (possibly to ad nauseum), spoke holes on a 40 mm
> deep rim are closer together than your MA-2 for the same spoke
> count), spokes are shorter, spoke support angle is greater (yes I
> agree they are all by small amounts), but when combined with a rim
> that has 3 times the h (from the equation) I come to a different
> conclusion. The lateral bending strength difference, at least to me,
> *is* significantlyl different.


Dave, are you asking if- all other things being equal- a tall aero rim
(say, 40 mm tall) is laterally stiffer than a "standard" rim like an MA2
(which is what, 15 mm tall)?

The taller rim would be significantly stiffer radially, it seems to me,
since it is just a thicker beam in that direction. In the lateral
direction, the aero rim is not a thicker beam but it is a wider beam.
Seems to me that would offer some increase in stiffness in theory.
Whether the difference would be significant to the operation of the
wheel vis-a-vis load bearing is a different question (since bicycle
wheels bear little lateral load except in unusual circumstances such as
skidding sideways). The lateral stiffness of the whole wheel is
affected not only by the stiffness of the rim but also by the spokes,
thicker spokes resulting in a laterally stiffer wheel if I remember
Damon Rinard's conclusion from his measurements correctly. ISTR spoke
tension being a relatively small factor in lateral stiffness.
I was challenging Jobst's statement regarding lateral stiffness where he concluded that the difference is not significant.
In Damon Rinard's findings rim height is the 5th in order of "Relative Contribution" (after 1. number of spokes, 2. spoke gauge, 3. rim weight, and 4. hub flange spacing) to lateral wheel stiffness. I agree with his findings and think that it is significant. He also concluded that spoke tension is not a significant factor until the spoke is slack.
While I agree that lateral stiffness is not the most important factor to reliability of a wheel, it is still significant to me.
I included this link earlier, in another response, but in case you missed it in this very long chain of "discussion":
http://www.sheldonbrown.com/rinard/wheel/index.htm
I have read through it and studied the data tables of the 140 wheels Damon measured. I find it instructive. I tried to get Damon to measure some of the wheels I built, but I was too late. He had moved on to employment by Trek and no longer has the time/set-up available to do further testing.
 
B

Bill Sornson

Guest
Michael Press wrote:
{snip}

> Using minuscule on proper names is misspelling, and
> ill-mannered when deliberate; except when it is one's own
> proper name.


Learn the proper use of semi-colons; you ain't got it now.

BS (really)
 

daveornee

New Member
Sep 18, 2003
2,763
0
0
Ben C said:
On 2007-03-19, Tim McNamara <[email protected]> wrote:
> daveornee <[email protected]> wrote:
>> >

>> The earlier statement " 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" was the one that I was questioning. I didn't
>> say that it was unclear, I just don't agree with it.
>>
>> To extend my point (possibly to ad nauseum), spoke holes on a 40 mm
>> deep rim are closer together than your MA-2 for the same spoke
>> count), spokes are shorter, spoke support angle is greater (yes I
>> agree they are all by small amounts), but when combined with a rim
>> that has 3 times the h (from the equation) I come to a different
>> conclusion. The lateral bending strength difference, at least to me,
>> *is* significantlyl different.

>
> Dave, are you asking if- all other things being equal- a tall aero rim
> (say, 40 mm tall) is laterally stiffer than a "standard" rim like an MA2
> (which is what, 15 mm tall)?
>
> The taller rim would be significantly stiffer radially, it seems to me,
> since it is just a thicker beam in that direction. In the lateral
> direction, the aero rim is not a thicker beam but it is a wider beam.
> Seems to me that would offer some increase in stiffness in theory.


It's not really a beam, more of a hollow box-section. I don't know what
difference that makes. I would expect that the stiffness of a
box-section would be even less affected by increasing its width in the
"wrong" dimension than a beam.

> Whether the difference would be significant to the operation of the
> wheel vis-a-vis load bearing is a different question (since bicycle
> wheels bear little lateral load except in unusual circumstances such as
> skidding sideways).


There is a real puzzle here. To summarize the argument: a radially stiff
rim means we can get away with fewer spokes to support the radial load.
But if the rim isn't stiffer laterally, which we expect it not to be
from looking at its shape, then the wheel might be prone to collapse
under lateral loads.

The reasoning seems sound, but I've never heard of this collapse
actually happening with a 16-spoke wheel. Two possibilities: either it
is less stiff, but it doesn't matter, because lateral loads are small
anyway; or the rims are stiffer laterally as well as radially in spite
of not being any wider (different materials, changes in the way they're
braced internally perhaps, etc.).
Ben,
You are proposing a different argument than I was asking about.
If you take the profiles of a box section rim and a tall aero section rim that has the same width at the bottom ... and deal with the same number of spokes, same everything else (OK you will need a longer inner tube valve to practically use the wheel).
1. Start with the brake track cross sections for the first 10 mm or so and call that section even.
2. Go to the next areas of the rims and compare the two as you work you way closer to the center of the wheel.... there isn't a portion in the profile where the "box section" rim is wider than the aero section rim, but after the "box section" ends (at 17 mm in height or so) there is still structure remaining in the aero section rim to resist lateral force.
3. Add the very small, but measurable, contibutions of shorter spokes and wider spoke bracing angle to the mix.
I observed the difference in lateral stiffness while building wheels. Low profile box section rims are easy enough to push (or pull) laterally so as to remove sufficient spoke tension to avoid spoke wind-up in the final round(s) of tensioning. It takes signicantly more force to accomplish this same removal of spoke tension with lateral force on taller aero section rims... some to the point where it is no longer practical to use this method as there are limits to my hand strength & grip of tmy truing stand on the subject wheel's locknut faces. I know that it is quite easy to use other methods to detect and remove wind-up, but the observations I made are proof enough to me that there is *significant* difference in lateral stiffness.
I am talking about comparing standard spoke count wheels (32 and 36 spokes per wheel) with the same type of 14/15 DB spokes in both instances.
I also use the "Mavic method" for side loading the wheels to stabilize them.
I need to exert significantly more force on tall aero section wheels (again with the same number of spokes) to insure that there is no wind-up remaining in the spokes.
For further information on people who have explored this much further, take a look at the Damon Rinard pages I referred to in earlier replies.
One further comparison:

http://www.sheldonbrown.com/rinard/wheel/grignon.htm
If you look at the Cane Creek wheels with 32 mm rim height and half the number (18 Vs 36) of the same diameter (2.0 mm) spokes and compare to the data on lateral stiffness of the 36 spoke Mavic GL 330 you will see that the lateral stiffness difference is very small (279 lb/in for the 36 spoke Mavic GL 330 Vs 273 lb/in for the 18 spoke 32 mm profile rimmed Cane Creek Crono).
The comparisons were chosen by François Grignon.
 
B

Ben C

Guest
On 2007-03-19, daveornee <[email protected]> wrote:
>
> Ben C Wrote:

[...]
>> It's not really a beam, more of a hollow box-section. I don't know
>> what
>> difference that makes. I would expect that the stiffness of a
>> box-section would be even less affected by increasing its width in the
>> "wrong" dimension than a beam.
>>
>> > Whether the difference would be significant to the operation of the
>> > wheel vis-a-vis load bearing is a different question (since bicycle
>> > wheels bear little lateral load except in unusual circumstances such

>> as
>> > skidding sideways).

>>
>> There is a real puzzle here. To summarize the argument: a radially
>> stiff
>> rim means we can get away with fewer spokes to support the radial
>> load.
>> But if the rim isn't stiffer laterally, which we expect it not to be
>> from looking at its shape, then the wheel might be prone to collapse
>> under lateral loads.
>>
>> The reasoning seems sound, but I've never heard of this collapse
>> actually happening with a 16-spoke wheel. Two possibilities: either it
>> is less stiff, but it doesn't matter, because lateral loads are small
>> anyway; or the rims are stiffer laterally as well as radially in spite
>> of not being any wider (different materials, changes in the way
>> they're
>> braced internally perhaps, etc.).

> Ben,
> You are proposing a different argument than I was asking about.


Yes, I think what I'm summarizing is roughly what I thought Jobst was
saying. My mental simplification here is to think of both rims as box
sections, but with the cross section of an MA2 for example as a one inch
square, and with the cross section of a deep aero rim as roughly a one
inch by 3 inch rectangle.

Of course it's not a rectangle, it's a triangle, and that might make a
difference.

> If you take the profiles of a box section rim and a tall aero section
> rim that has the same width at the bottom ... and deal with the same
> number of spokes, same everything else (OK you will need a longer inner
> tube valve to practically use the wheel).
> 1. Start with the brake track cross sections for the first 10 mm or so
> and call that section even.
> 2. Go to the next areas of the rims and compare the two as you work
> you way closer to the center of the wheel.... there isn't a portion in
> the profile where the "box section" rim is wider than the aero section
> rim, but after the "box section" ends (at 17 mm in height or so) there
> is still structure remaining in the aero section rim to resist lateral
> force.
> 3. Add the very small, but measurable, contibutions of shorter spokes
> and wider spoke bracing angle to the mix.
> I observed the difference in lateral stiffness while building wheels.
> Low profile box section rims are easy enough to push (or pull)
> laterally so as to remove sufficient spoke tension to avoid spoke
> wind-up in the final round(s) of tensioning. It takes signicantly more
> force to accomplish this same removal of spoke tension with lateral
> force on taller aero section rims... some to the point where it is no
> longer practical to use this method as there are limits to my hand
> strength & grip of tmy truing stand on the subject wheel's locknut
> faces. I know that it is quite easy to use other methods to detect and
> remove wind-up, but the observations I made are proof enough to me that
> there is *significant* difference in lateral stiffness.


I'm inclined to the view that aero rims generally _are_ stiffer
laterally, yes, and so this raises the question why or what's missing
from Jobst's explanation.

> I am talking about comparing standard spoke count wheels (32 and 36
> spokes per wheel) with the same type of 14/15 DB spokes in both
> instances.
> I also use the "Mavic method" for side loading the wheels to stabilize
> them.
> I need to exert significantly more force on tall aero section wheels
> (again with the same number of spokes) to insure that there is no
> wind-up remaining in the spokes.
> For further information on people who have explored this much further,
> take a look at the Damon Rinard pages I referred to in earlier
> replies.


I did look at those. It's hard to know what he means by putting rim
height fifth on the list. I took that to mean "not very important" since
it was the lowest on the list. But this might not be the correct
interpretation.

> One further comparison:
>
> http://www.sheldonbrown.com/rinard/wheel/grignon.htm
> If you look at the Cane Creek wheels with 32 mm rim height and half the
> number (18 Vs 36) of the same diameter (2.0 mm) spokes and compare to
> the data on lateral stiffness of the 36 spoke Mavic GL 330 you will
> see that the lateral stiffness difference is very small (279 lb/in for
> the 36 spoke Mavic GL 330 Vs 273 lb/in for the 18 spoke 32 mm profile
> rimmed Cane Creek Crono).
> The comparisons were chosen by François Grignon.
 
M

Michael Press

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

> Michael Press wrote:
> {snip}
>
> > Using minuscule on proper names is misspelling, and
> > ill-mannered when deliberate; except when it is one's own
> > proper name.

>
> Learn the proper use of semi-colons; you ain't got it now.


English usage and grammar is not a completely defined
system. For instance, the use of the possessive mark in
proper names and how to punctuate quotations cannot be
universally defined. Many usages that are otherwise
forbidden can be acceptable in particular
circumstances; such as split infinitives. Semicolons
are quite proper in place of a comma when the writer
means to indicates a stronger break in the flow of a
sentence.
--
Michael Press
 

daveornee

New Member
Sep 18, 2003
2,763
0
0
Ben C said:
On 2007-03-19, daveornee <[email protected]> wrote:
>
> Ben C Wrote:

[...]
>> It's not really a beam, more of a hollow box-section. I don't know
>> what
>> difference that makes. I would expect that the stiffness of a
>> box-section would be even less affected by increasing its width in the
>> "wrong" dimension than a beam.
>>
>> > Whether the difference would be significant to the operation of the
>> > wheel vis-a-vis load bearing is a different question (since bicycle
>> > wheels bear little lateral load except in unusual circumstances such

>> as
>> > skidding sideways).

>>
>> There is a real puzzle here. To summarize the argument: a radially
>> stiff
>> rim means we can get away with fewer spokes to support the radial
>> load.
>> But if the rim isn't stiffer laterally, which we expect it not to be
>> from looking at its shape, then the wheel might be prone to collapse
>> under lateral loads.
>>
>> The reasoning seems sound, but I've never heard of this collapse
>> actually happening with a 16-spoke wheel. Two possibilities: either it
>> is less stiff, but it doesn't matter, because lateral loads are small
>> anyway; or the rims are stiffer laterally as well as radially in spite
>> of not being any wider (different materials, changes in the way
>> they're
>> braced internally perhaps, etc.).

> Ben,
> You are proposing a different argument than I was asking about.


Yes, I think what I'm summarizing is roughly what I thought Jobst was
saying. My mental simplification here is to think of both rims as box
sections, but with the cross section of an MA2 for example as a one inch
square, and with the cross section of a deep aero rim as roughly a one
inch by 3 inch rectangle.

Of course it's not a rectangle, it's a triangle, and that might make a
difference.

> If you take the profiles of a box section rim and a tall aero section
> rim that has the same width at the bottom ... and deal with the same
> number of spokes, same everything else (OK you will need a longer inner
> tube valve to practically use the wheel).
> 1. Start with the brake track cross sections for the first 10 mm or so
> and call that section even.
> 2. Go to the next areas of the rims and compare the two as you work
> you way closer to the center of the wheel.... there isn't a portion in
> the profile where the "box section" rim is wider than the aero section
> rim, but after the "box section" ends (at 17 mm in height or so) there
> is still structure remaining in the aero section rim to resist lateral
> force.
> 3. Add the very small, but measurable, contibutions of shorter spokes
> and wider spoke bracing angle to the mix.
> I observed the difference in lateral stiffness while building wheels.
> Low profile box section rims are easy enough to push (or pull)
> laterally so as to remove sufficient spoke tension to avoid spoke
> wind-up in the final round(s) of tensioning. It takes signicantly more
> force to accomplish this same removal of spoke tension with lateral
> force on taller aero section rims... some to the point where it is no
> longer practical to use this method as there are limits to my hand
> strength & grip of tmy truing stand on the subject wheel's locknut
> faces. I know that it is quite easy to use other methods to detect and
> remove wind-up, but the observations I made are proof enough to me that
> there is *significant* difference in lateral stiffness.


I'm inclined to the view that aero rims generally _are_ stiffer
laterally, yes, and so this raises the question why or what's missing
from Jobst's explanation.

> I am talking about comparing standard spoke count wheels (32 and 36
> spokes per wheel) with the same type of 14/15 DB spokes in both
> instances.
> I also use the "Mavic method" for side loading the wheels to stabilize
> them.
> I need to exert significantly more force on tall aero section wheels
> (again with the same number of spokes) to insure that there is no
> wind-up remaining in the spokes.
> For further information on people who have explored this much further,
> take a look at the Damon Rinard pages I referred to in earlier
> replies.


I did look at those. It's hard to know what he means by putting rim
height fifth on the list. I took that to mean "not very important" since
it was the lowest on the list. But this might not be the correct
interpretation.

> One further comparison:
>
> http://www.sheldonbrown.com/rinard/wheel/grignon.htm
> If you look at the Cane Creek wheels with 32 mm rim height and half the
> number (18 Vs 36) of the same diameter (2.0 mm) spokes and compare to
> the data on lateral stiffness of the 36 spoke Mavic GL 330 you will
> see that the lateral stiffness difference is very small (279 lb/in for
> the 36 spoke Mavic GL 330 Vs 273 lb/in for the 18 spoke 32 mm profile
> rimmed Cane Creek Crono).
> The comparisons were chosen by François Grignon.
You shouldn't oversimplify in either direction:
Stack a connected triangle on top of a rectangular section.
Compare the actual profiles of two rims with the same width lower section.
I think you will see that there isn't anywhere on the profile overlay where the box section rim is wider.
 
B

Ben C

Guest
On 2007-03-19, daveornee <[email protected]> wrote:
>
> Ben C Wrote:

[...]
>> Yes, I think what I'm summarizing is roughly what I thought Jobst was
>> saying. My mental simplification here is to think of both rims as box
>> sections, but with the cross section of an MA2 for example as a one
>> inch square, and with the cross section of a deep aero rim as roughly
>> a one inch by 3 inch rectangle.
>>
>> Of course it's not a rectangle, it's a triangle, and that might make
>> a difference.

[...]
> You shouldn't oversimplify in either direction:
> Stack a connected triangle on top of a rectangular section.
> Compare the actual profiles of two rims with the same width lower
> section.
> I think you will see that there isn't anywhere on the profile overlay
> where the box section rim is wider.


Of course not wider, I never meant to dispute that. A rim is quite
particular about its width because it relates to tyre size, whether it
fits in the frame etc.

The question is, is this:

----
| |
| |
----

or this:

----
/ |
\ |
----

stiffer laterally (i.e. extruding those cross-section out of and into
the screen, and bending them in the up-and-down-the-page direction).
Imagine the triangle as being much more pointy than I've drawn it of
course.

All things being equal I would think not, lateral stiffness I would
expect to be theoretically about the same, perhaps a bit stiffer for the
lower one, but a much smaller difference than the difference in radial
stiffness.

The simplified picture is

----
| |
| |
----

vs

---------
| |
| |
---------

Again, I expect a small increase in lateral stiffness for the second of
the two cross-sections, but a large increase in radial stiffness.
 
On 19 Mar 2007 04:21:15 GMT, [email protected] wrote:

>Carl Fogel writes:
>
>> Instead of waving your arms and whining for sympathy, you should:

>
>Now you are getting rude. This characterization of my question is
>stretching decorum of which you approve beyond reasonable limits. I
>do not use such language in responses as you may have noticed.
>
>> a) Learn to address Jim Beam directly, just as I addressed you
>> directly by replying to your obnoxious post, instead of squirting ink
>> about not having his email address. If you haven't the courage to
>> address him directly in this thread about what troubles you, why ask
>> me to do it for you?

>
>Are you jim beam's alter ego? You too are getting ruder with each
>response just as he has descended into crude street language. Calling
>people obnoxious is not what I expect in these responses. What is it
>that irks you to the degree of losing you "Dear reader" courtesy?
>
>> b) Learn to distinguish between spelling and capitalization--your
>> quibbling is as inaccurate and trifling as ever and is presumably
>> meant to conceal the familiar lack of content.

>
>> Cheers,

>
>> e.e. cummings

>
>The parallel with jim beam and cummings doesn't ring well. I'm sure
>cummings did not use scatological and sexual innuendo in the manner to
>which we are being subjected in reading this thread.
>
>Jobst Brandt


Dear Jobst,

You're still waving your arms to attact attention, like a little boy
trying to make excuses:

"Gee, you called me rude and obnoxious, but Jim Beam is awful, why
aren't you calling him rude and obnoxious, too?"

I repeat: quit tugging at my shirt sleeve and whining that I must
condemn Jim Beam to please you. If you have a problem with him, reply
to him directly.

Judging by your posts, your real problem is that I pointed out how
rude you were to a stranger:

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

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

Feel free to protest again that you have no idea why anyone on RBT
would point out your habitually rude replies to newcomers--the
spectacle is always amusing.

As John Forrest Tomlinson recently pointed out, the only real question
is whether your bad manners are automated or hand-crafted:

http://groups.google.com/group/rec.bicycles.tech/msg/a9a2e3aa4c0dee84

Cheers,

Carl Fogel