The Basics of Wheel Alignment and Wheelbuilding
Jeff Napier
wheelbuilding at www.bikewebsite.com
Have fun!
- Jeff -
Ted
Nothing at all about stress relieving.
Pressing on the rim, against the axle end, will untwist spokes but it is
difficult to press hard enough to relieve internal stresses in
individual spokes that way. Better to add a step: wearing heavy
gloves, grasp pairs of spokes and squeeze hard, repeating all around the
wheel. Done properly, this will practically eliminate the need for
later truing and the spokes will last a long, long, time.
carl...@comcast.net
Dear Ted,
Outside of posts on rec.bicycles.tech and references to
Jobst's book, do you know of any studies, tests, or web
pages that address what we're calling "stress relieving" and
"stress relief"?
The quotation marks are used only to broaden the question,
since there may be other names and methods for
spoke-squeezing, as well as other claims for the process is
supposed to do to the spokes.
Sheldon Brown, for example, quotes Jobst, but gives the
spokes a twist with a smooth crank arm instead of squeezing
them:
http://www.sheldonbrown.com/wheelbuild.html#seating
It would be interesting to find out if Japanese Keirin
bicycle mechanics squeeze or twist spokes. Maybe John Dacey
knows?
Carl Fogel
daveornee
<http://yarchive.net/bike/stress_relieve.html>
Might be worth a look.
--
daveornee
Bicycling 1/2 century
carl...@comcast.net
Dear Dave,
Yes, that's a typical 1998 rec.bicycles.tech thread with the
usual suspects. It's one of the exchanges that led me to
wonder about the matter. Here's a fair example:
>>>> That is why I asked for references to hard scientific papers, a
>>>> mathematical explanation or other such research.
>>> The book gives both an explanation and experimental methods by which
>>> you can convince yourself of these effects. Had someone written about
>>> it previously, I would not have written "the Bicycle Wheel". Much of
>>> what the book contains could previously not be found in any
>>> literature. The work of Karl Wiedemer is cited.
>> Your book contained no mathematics on this topic, no results of
>> proper controlled experiments on the cause of the effects and no
>> references that I could look up. In particular, I was extremely
>> surprised that it didn't seem to contain any references to where
>> you had published your analyses and experiments in the scientific
>> literature.
>Well! I guess that means it is all wrong as you state.
>> Yes, I have tried doing a literature search, but found nothing.
>As you see, I found more than you. With help I located Karl
>Wiedemer's publication on the subject. Prof. Wiedemer, now
>retired, did his analysis at the same time I did and he also had
>no references because it was new work in a field that had progressed
>without analysis for a long time. Prof. Pippard in England wrote
>extensively on the subject but never discovered the mode of
>wheel loading and deflections that I and Wiedemer presented.
>As I said, I made the analysis by measurement and was rejected
>by professors of engineering. When I presented the finite element
>analysis, these same people chose to change the subject and get
>back to "serious" work.
[ and so on]
Googling for "karl wiedemer" produces four other pages, all
in German, one on safety devices for coal dust, one on blast
furnace slag, one on the history of some club from 1896, and
two other in pdf format that Google does not offer to
translate.
Spoke-squeezing is an intriguingly mysterious subject to
research. I remain agnostic, wavering one way and the other,
but haven't seen any experimental data or analyses involving
bicycle spokes. If you have the 3rd edition, perhaps you
could peek at the Wiedemer stuff and give me your thoughts
on it?
Carl Fogel
jim beam
>
<snip>
> Spoke-squeezing is an intriguingly mysterious subject to
> research. I remain agnostic, wavering one way and the other,
> but haven't seen any experimental data or analyses involving
> bicycle spokes. If you have the 3rd edition, perhaps you
> could peek at the Wiedemer stuff and give me your thoughts
> on it?
you may also want to consider this question:
q: elevator safety certification requires loading the cab to double
it's "safe working load". this is to test the wire ropes that suspend
it. the reason is that fracture mechanics predict that this process
will typically reveal by failure any latent flaws. but, if we extend
spoke squeezing theory, wouldn't this overload procedure also prevent
fatigue of elevator cables?
a: no. elevator cables still fatigue and need regular testing,
inspection & replacement.
the bottom line is that there is no quantification or testing of this
spoke squeeze theory. squeezing "as hard as you can" is no more
scientific than building with spoke tension "as high as the rim can
bear". i would suggest to you that the reason academics "change the
subject and get back to "serious" work" is because this theory is mere
speculation - it's author has shown no basis in statistical fact, and
most definitely not by metallurgical analysis.
carl...@comcast.net
Dear Jim,
Aaaargh!
I really wish that you could have thought of a different
example, since I didn't want to hear that elevator cables
need replacing.
I draw comfort from a vague memory that they have some kind
of safety brake, according to Ambrose Bierce and to some
famous demonstration in which Otis cut the cable while
standing on top of an elevator.
Two questions occur to me, both illustrating the depths of
my ignorance.
First, how much do elevator cables resemble spokes? Are they
made of stainless steel? Does it matter that they bend
around pulleys in a constant side-to-side flexing different
than spokes? Do spokes and cables go through similar cycles
of tension, partial release, and back to normal tension?
Second, do spokes in well-built (by whatever means) wheels
require constant inspection and replacement?
I understand that spokes are different from cables. I'm just
wondering how big the differences are and how much they
matter.
See you in the stairwell,
Carl Fogel
jim beam
as indeed i do too!
>
> Two questions occur to me, both illustrating the depths of
> my ignorance.
>
> First, how much do elevator cables resemble spokes?
obviously, rope is multistrand, a spoke is single strand, but the
materials & applications are the same. it's only the practical issues
of price, of needing a spoke that resists torque sufficiently to be able
to tighten a nipple and indeed, ability to thread a nipple in the first
place that lead to the use of single strand.
> Are they
> made of stainless steel?
sometimes. but typically not unless environmental conditions demand it.
doesn't make much of a difference - neither stainless nor typical
non-stainless steel rope have an endurance limit so they'll both fatigue.
> Does it matter that they bend
> around pulleys in a constant side-to-side flexing different
> than spokes?
yes, and those pulleys cause wear and bending stresses, but that's why
you use multi-strand in the first place. also, one strand breaking in a
rope of 100 leaves 99 others - pretty comforting. and there's a small
degree of freedom to move between strands which reduces cross sectional
stress considerably.
> Do spokes and cables go through similar cycles
> of tension, partial release, and back to normal tension?
yes, absolutely.
>
> Second, do spokes in well-built (by whatever means) wheels
> require constant inspection and replacement?
if you read the instructions that come with all these expensive
pre-built wheels yes! but, that's only a cursory visual inspection.
it's just like the contrasts between the safety & inspection regimes for
cars vs planes, wheel spokes are not usually considered a high fatality
risk, so there's no reason to subject them to a rigorous expensive
certification procedure.
Tim McNamara
> carl...@comcast.net wrote:
>>
> <snip>
>
>> Spoke-squeezing is an intriguingly mysterious subject to
>> research. I remain agnostic, wavering one way and the other, but
>> haven't seen any experimental data or analyses involving bicycle
>> spokes. If you have the 3rd edition, perhaps you could peek at the
>> Wiedemer stuff and give me your thoughts on it?
>
> you may also want to consider this question:
>
> q: elevator safety certification requires loading the cab to double
> it's "safe working load". this is to test the wire ropes that
> suspend it. the reason is that fracture mechanics predict that this
> process will typically reveal by failure any latent flaws. but, if
> we extend spoke squeezing theory, wouldn't this overload procedure
> also prevent fatigue of elevator cables?
>
> a: no. elevator cables still fatigue and need regular testing,
> inspection & replacement.
Of course they fatique. They are constantly being wound around a drum
and unwound with a large weight dangling on the end. This doesn't
happen with spokes. Spokes are one fairly thick wire under a fairly
small load, elevator cables are thin-stranded cables with internal
friction, corrosion challenges, etc.
Additionally, a spoke supports a load much differently than an
elevator cable, as has been discussed and verified- independently of
Brandt, BTW- by finite element analysis.
I see you're keeping the fine art of red herrings alive.
> the bottom line is that there is no quantification or testing of
> this spoke squeeze theory. squeezing "as hard as you can" is no
> more scientific than building with spoke tension "as high as the rim
> can bear". i would suggest to you that the reason academics "change
> the subject and get back to "serious" work" is because this theory
> is mere speculation - it's author has shown no basis in statistical
> fact, and most definitely not by metallurgical analysis.
And it's easy to take cheap shots when he's out of town and not able,
therefore, to respond. I don't quite know why it sticks in your craw
so much to admit even the possibility that Jobst is right, and it's an
interesting psychological problem especially when combined with your
anonymity behind a boozy screen name. But if you're going to
seriously critique his work and not just take potshots, come up with a
quantified and testable alternative analysis. Prove him wrong. Put
up or shut up. Frankly, jim beam old buddy old pal, I don't think you
have the stuff.
Tim McNamara
> carl...@comcast.net wrote:
>> Second, do spokes in well-built (by whatever means) wheels require
>> constant inspection and replacement?
>
> if you read the instructions that come with all these expensive
> pre-built wheels yes! but, that's only a cursory visual
> inspection. it's just like the contrasts between the safety &
> inspection regimes for cars vs planes, wheel spokes are not usually
> considered a high fatality risk, so there's no reason to subject
> them to a rigorous expensive certification procedure.
A nice duck and weave instead of answering the question. You sound
like a politician, and I've had enough of that for one week.
The answer to Carl's question is "no." I ride my bikes, I never
bother to inspect the spokes and I haven't broken a spoke in 50,000 to
60,000 miles of riding, racing, light touring and cyclo-cross. Of
course I built those wheels using a method of wheelbuilding that
mr. beam is attempting to discredit by misleading analogies and such;
I suppose you have to resort to that sort of thing when you can't
produce facts that are contradictory.
The last spoke I broke was in about 1994 on a group training ride;
rather embarassing for the guy who built the wheel, as he was along
for the ride. It was an Asahi 14g spoke, on the non-drive side of a 7
sp wheel spaced at 126 mm; Sun rim, Avocet Model III hub (Campy copy).
Hmm, correction, the last spokes I broke were in an 18" wheel built on
an SRAM 3x7 hub in a folding bike (Birdy, which was infamous for
broken spokes for a couple of years). I rebuilt the wheel in 1999 or
2000 and no broken spokes since, but that bike doesn't see many miles.
jim beam
tim, you're like a drunken finnean looking for a bit of bare-knucked
sport on his way home from a bar. read what i said when you're sober,
then show me one single piece of metallurgical evidence to support
brandts bullying assertions. or your allusions to superior mental
health come to that.
Benjamin Weiner
How do you inspect your spokes? I can't imagine that it is very
easy to see signs of imminent failure. Well-built wheels don't
require "constant" spoke replacement.
Carl, did you see in the discussion at
http://yarchive.net/bike/stress_relieve.html
the article containing this quote and link
"For some results of some actual residual stress measurements I did on
7050 aluminum plate before and after stretching see:
http://www.lanl.gov/residual/alplate.pdf
The residual stress was reduced by about a factor of 10 by the stress
relief process."
Jose Rizal
> > First, how much do elevator cables resemble spokes?
>
> obviously, rope is multistrand, a spoke is single strand, but the
> materials & applications are the same.
Materials may be the same but "applications" are not. That "rope" is
subjected to turns and loads on pulleys, as you admit below.
> it's only the practical issues
> of price, of needing a spoke that resists torque sufficiently to be able
> to tighten a nipple and indeed, ability to thread a nipple in the first
> place that lead to the use of single strand.
This made-up story doesn't even look nor sound good. Spokes still do
twist, and a threaded nipple is not the only way to have an adjustable
tightening mechanism on a rim.
> > Does it matter that they bend
> > around pulleys in a constant side-to-side flexing different
> > than spokes?
>
> yes, and those pulleys cause wear and bending stresses, but that's why
> you use multi-strand in the first place.
Hence spokes and cable are not the same "application".
> also, one strand breaking in a
> rope of 100 leaves 99 others - pretty comforting.
Nonsense. If a cable is loaded such that a strand breaks, the effective
cross section of the cable is reduced and hence the load results in a
higher stress for the remaining strands, which will rapidly lead to
failure of the cable. If a strand was broken by other than a load (eg
cut), the same effect on cross section will be observed. You can't cut
a strand on a solid spoke.
> and there's a small
> degree of freedom to move between strands which reduces cross sectional
> stress considerably.
Again, nonsense. What can move between strands? The only way to move
loads between strands is if the strands are able to move along the
cable's length. This is a bad event since the strands will not take up
the load evenly amongst themselves.
> > Second, do spokes in well-built (by whatever means) wheels
> > require constant inspection and replacement?
>
> if you read the instructions that come with all these expensive
> pre-built wheels yes! but, that's only a cursory visual inspection.
> it's just like the contrasts between the safety & inspection regimes for
> cars vs planes, wheel spokes are not usually considered a high fatality
> risk, so there's no reason to subject them to a rigorous expensive
> certification procedure.
In other words, no.
Trevor Jeffrey
originally about tied and soldered wheels, what difference they made and how
a wheel is loaded/supported/hangs/stands on or from its tyre/rim/spoke(s)
was reduced mostly to the semantics of the English language and whether
appropriate engineering terms were being used/abused. I fear the same may
happen again.
So here it is, how to build a wheel. Ignore JBs "stress releiving" it
is not required. When the spoke is relaxed, form the bend at the crossing,
oil the nipples with linseed and tighten to a point where the riders full
weight does not releive the bottom spoke. This is using a method of minimal
tension not only provides a wheel which will fail safe but also maintains a
ridable wheel in the event of impact damage resulting in spoke loss.
Severre buckling is eliminated. Spoke quality is not an issue.
The pre-forming of the spoke reduces the side to side bending which
occurs at the hub interface to a minimum thus allowing maximum life.
If I want to ride a rock strewn bridleway I will, with 20mm wide rims.
This is not asking for the impossible. I've done it safe in the knowledge
that my wheels will not buckle due to incorrect build. It was only through
cycling that road improvements came about in England with a smooth sealed
surface. If you look at early high-wheelers they had 20mm wide rims, so for
reliability there is no reason why a 27" wheel would require anything of
larger section. Those wheels where built for rough roads. This is a change
of my belief of 5+ years ago, when I thought a wider rim was required to
prevent buckling. Experience has since demonstrated that wheels built with
pre-formed spokes grossly outperform those built with ignorance. So all
in all rim width is dependant only on tyre choice.
Perhaps some 7oz rims may eventually become available again. Try using
JB's method on that and you may as well burn your money, followed by the
book.
TJ
Jose Rizal
> After hundreds of exchanges previously in this newsgroup the questions
> originally about tied and soldered wheels, what difference they made and how
> a wheel is loaded/supported/hangs/stands on or from its tyre/rim/spoke(s)
> was reduced mostly to the semantics of the English language and whether
> appropriate engineering terms were being used/abused. I fear the same may
> happen again.
You've just started it by your poor writing skill.
> So here it is, how to build a wheel. Ignore JBs "stress releiving" it
> is not required. When the spoke is relaxed, form the bend at the crossing,
> oil the nipples with linseed and tighten to a point where the riders full
> weight does not releive the bottom spoke.
Just how do you do this, and how do you account for the dynamic loads
put on the wheel which exceed the static rider/bike weight?
> This is using a method of minimal
> tension not only provides a wheel which will fail safe
What the hell is "a wheel which will fail safe"?
> but also maintains a
> ridable wheel in the event of impact damage resulting in spoke loss.
Uhhhh, headache.....
> Severre buckling is eliminated.
Since buckling is also load magnitude dependent, "severre" buckling
cannot be avoided if the load is high enough, and especially since you
only tensioned the spokes enough to take up your static weight.
> Spoke quality is not an issue.
Plastic spokes will be fine then.
Todd Bryan
> So here it is, how to build a wheel. Ignore JBs "stress releiving" it
> is not required. When the spoke is relaxed, form the bend at the crossing,
> oil the nipples with linseed and tighten to a point where the riders full
> weight does not releive the bottom spoke. This is using a method of minimal
> tension not only provides a wheel which will fail safe but also maintains a
> ridable wheel in the event of impact damage resulting in spoke loss.
> Severre buckling is eliminated. Spoke quality is not an issue.
So, how do I determine when the rider's full weight will not unload a
spoke? Do I measure that at rest? Or perhaps while dropping the laden
bike off a 2 foot high ledge? The point is that wheels are subject to
dynamic loads and you cannot predict whether those loads will unload
bottom spokes. So you tension spokes as highly as possible to handle the
highest radial load possible.
I'm looking forward to your alternative rigorous analysis of spoked
wheels, preferably published in book form. You and 'Jim Beam' might
collaborate on that work.
--
Todd Bryan
Santa Barbara, CA
bryan at cs dot utk dot edu
jim beam
> jim beam:
>
>
>>>First, how much do elevator cables resemble spokes?
>>
>>obviously, rope is multistrand, a spoke is single strand, but the
>>materials & applications are the same.
>
>
> Materials may be the same but "applications" are not. That "rope" is
> subjected to turns and loads on pulleys, as you admit below.
>
>
>>it's only the practical issues
>>of price, of needing a spoke that resists torque sufficiently to be able
>>to tighten a nipple and indeed, ability to thread a nipple in the first
>>place that lead to the use of single strand.
>
>
> This made-up story doesn't even look nor sound good. Spokes still do
> twist, and a threaded nipple is not the only way to have an adjustable
> tightening mechanism on a rim.
what method do you propose? the threaded nipple method is cheap,
reliable and has stood the test of time. and of course spokes still
twist, but not as much as the equivalent multi-strand. brake cable's
about the same as a spoke, try the comparision.
>
>
>>>Does it matter that they bend
>>>around pulleys in a constant side-to-side flexing different
>>>than spokes?
>>
>>yes, and those pulleys cause wear and bending stresses, but that's why
>>you use multi-strand in the first place.
>
>
> Hence spokes and cable are not the same "application".
maybe your definiton of tension is different to mine.
>
>
>>also, one strand breaking in a
>>rope of 100 leaves 99 others - pretty comforting.
>
>
> Nonsense. If a cable is loaded such that a strand breaks, the effective
> cross section of the cable is reduced and hence the load results in a
> higher stress for the remaining strands, which will rapidly lead to
> failure of the cable. If a strand was broken by other than a load (eg
> cut), the same effect on cross section will be observed. You can't cut
> a strand on a solid spoke.
read some fracture mechanics. crack propagation in a single piece leads
to failure of the whole. fracture of a single strand does not. next
time you fly, check out the skin of the plane and notice that it's made
of many parts riveted together. is this because manufacturers can't
weld? no, it's because crack proagation in one piece does not propagate
to the whole - it's a policy of fracture containment.
>
>
>>and there's a small
>>degree of freedom to move between strands which reduces cross sectional
>>stress considerably.
>
>
> Again, nonsense. What can move between strands? The only way to move
> loads between strands is if the strands are able to move along the
> cable's length. This is a bad event since the strands will not take up
> the load evenly amongst themselves.
take a cable and cut the end exactly square. then bend it about some
kind of mandrel. notice how the end is no longer square and the strands
are staggered? they move relative one to another. this is why rope is
flexible.
jim beam
> jim beam <nos...@example.net> wrote:
>
>>carl...@comcast.net wrote:
>
>
>>>Second, do spokes in well-built (by whatever means) wheels
>>>require constant inspection and replacement?
>
>
>>if you read the instructions that come with all these expensive
>>pre-built wheels yes! but, that's only a cursory visual inspection.
>>it's just like the contrasts between the safety & inspection regimes for
>>cars vs planes, wheel spokes are not usually considered a high fatality
>>risk, so there's no reason to subject them to a rigorous expensive
>>certification procedure.
>
>
> How do you inspect your spokes? I can't imagine that it is very
> easy to see signs of imminent failure.
absolutely correct, the chances of you getting a visual on a spoke
fatigue crack are slim to zero. but pre-built wheels come with an
ass-covering "regular inspection" warning just the same. about the only
thing you can do for spokes short of spending a huge amount of money, is
just do a visual inspection for nicks & dents which could be fatigue
initators, and do a "ping" test for anything loosening up.
> Well-built wheels don't
> require "constant" spoke replacement.
>
> Carl, did you see in the discussion at
> http://yarchive.net/bike/stress_relieve.html
> the article containing this quote and link
>
> "For some results of some actual residual stress measurements I did on
> 7050 aluminum plate before and after stretching see:
> http://www.lanl.gov/residual/alplate.pdf
> The residual stress was reduced by about a factor of 10 by the stress
> relief process."
sure, metallurgical stress relief is very important, particularly when
trying to mitigate distortion of components machined out of 70mm chunks
of aluminum like that described above, but that material is entirely
different from a piece of high tensile wire. how often do you go about
comparing church bells to bicycles? they both have about as much in common.
Tim McNamara
"Finnean?" Did you mean "Fenian"? Nice reference though.
> read what i said when you're sober, then show me one single piece of
> metallurgical evidence to support brandts bullying assertions. or
> your allusions to superior mental health come to that.
You'd have to take that up with the author of the book, eh? But as
usual you're ducking and weaving, casting rocks and aspersions and
then crying foul when you get treated the way you treat others. Stop
being a whiner and step up to the plate. If you can disprove Brandt's
theory, then do so. Put up or shut up. If you can't disprove his
ideas, then accept that he may in fact be right. I'll say it again- I
don't think you have the stuff. If you did, you would have actually
disproven Brandt a long time ago.
All I can say, not being an engineer, is that the wheels I've built
with his method have performed admirably, better than wheels I've
bought built according to the Wheelsmith specs and much better than
wheels I have bought built to who knows what specs (e.g., OEM wheels).
I'll settle for my 50,000 to 60,000 miles without a spoke breakage and
rarely having to true a wheel- even 9 speed wheels built with MA2
rims. At my weight (215 lbs, give or take 10), I'm pleased with the
results.
The type of guttersniping you indulge in does not advance the
discussion one whit. Over the years we've had recurrent posters with
the gunslinger mentality who come into town aiming to knock off the
big guy. You seem to be just another one of this species. I suspect
that many of those posters have been the same person hiding behind
different personae, due to consistencies in writing style and
conceptual framework. You don't raise chickens, by any chance?
As far as comparative mental health, not having met you I can't say
for sure. However, at least I don't have an obsessive hatred of
someone on the Internet with a need to continue to attack that person
over and over and over- even when I can't prove that person wrong.
carl...@comcast.net
<b...@mambo.ucolick.org> wrote:
[snip]
>
>Carl, did you see in the discussion at
>http://yarchive.net/bike/stress_relieve.html
>the article containing this quote and link
>
> "For some results of some actual residual stress measurements I did on
> 7050 aluminum plate before and after stretching see:
> http://www.lanl.gov/residual/alplate.pdf
> The residual stress was reduced by about a factor of 10 by the stress
> relief process."
>
Dear Benjamin,
Yes, I've seen the thread and looked at the link to the
test. While I can't recall where I read it, others pointed
out a few potential problems.
The test involved a comparatively massive metal slab, about
6 inches square and 3 inches thick, not a spoke about a
tenth of an inch thick. (My naive guess would be that this
size difference wouldn't matter because the flaws are
microscopic, but a materials engineer suggested that it
might.)
The test slab was cut out of a much larger piece that was
"rolled," so it was worked to some degree, but it may not
have been as heavily worked as a bicycle spoke. (This
sounded more plausible to me, but it wouldn't surprise me to
learn that the rolling of the slab worked it just as much or
more as the production of a spoke works a spoke.)
The metal tested was aluminum, not stainless steel. (I know
that the two metals are similar in that neither shows a
yield point on a stress-strain test, but are different in
that aluminum ain't stainless steel. I also know that
aluminum and steel have different fatigue characteristics
when used in frames and that I don't have the slightest
idea whether any of this matters in comparing the aluminum
slab to the stainless steel spoke.)
The question of how much "stretching" was used on the test
slab versus how much "squeeze" (same idea) is used by a
typical bicycle wheel builder was not addressed. The slab
was stretched 1.5% to 3% in the rolling direction, but how
much a spoke is stretched by the squeeze method is unclear.
(My own vague notion is that a good squeeze should stretch a
pair of 300mm spokes that much.)
What the stretching does to the material in terms of final
dimensions was also debated. My naive impression was that
both the stretched test plate and the squeezed spokes are
tensioned only elastically and snap back to their original
length when tension is released--that is, there's no
permanent elongation. However, others have suggested that
releasing any stress involves permanent changes in
dimensions, microscopic or not. Damned if I know the answer.
A final question concerned the quenching of the aluminum
plate (I think that you have to go to the later version of
the test to see this) and whether quenching aluminum creates
far more internal stress than would be found in spokes and
whether such a difference makes any comparison a matter of
apples and oranges. Again, I don't know enough about metals
to even hazard a guess--I have a hazy notion that spokes are
cold worked, not quenched, but whether this matters to
stress is a mystery to me.
None of these objections, as I recall, were meant to cast
any doubt on Mike Prime's aluminum plate test itself, which
was not undertaken to address the stainless steel spoke
question and seems like a reasonable test to bring up. They
were raised to point out that the two situations may differ
in significant ways (and were also raised probably for the
joy of quibbling, not that we ever see any of that on
rec.bicycles.tech).
The trouble is probably that the question of spoke fatigue
is trickier than we'd like it to be. Various explanations
exist, each with fierce partisans, but testing of the kind
that would stand up in a high school physics class seems to
be hard to find, partly because the testing is likely to be
much harder than expected, partly because the subject is
much more complicated than it might seem at first, and
partly because the question is not exactly crucial.
I often wonder whether my wavering on this matter resembles
what I had to endure with people debating who wrote
Shakespeare. I'm not sure who's right about spoke squeezing,
so I long for a site that patiently goes through the details
for the layman in the way that this site explains literary
matters:
http://shakespeareauthorship.com
Unfortunately, not everyone is as helpful as you are, so
questions here on rec.bicycles.tech often degenerate into
mere name-calling instead of explanations. It's not much
good trying to convince a skeptical audience either way on
spoke-squeezing if all that I have is that one person says
that the other is wrong and both claim that their spokes
last forever.
The last person whom I bored to tears about spokes raised an
interesting question. If spoke-squeezing works, either by
relieving stress or by other methods, and makes spokes
practically immortal, how soon should unsqueezed spokes
break? That is, when did I predict that the unsqueezed
spokes would fail?
My muttered "sooner" was dismissed as being a bit imprecise.
I'd mentioned that some spoke squeezers claim over 50,000
miles on failure-free spokes, so my tormentor kept asking me
when he should expect his unsqueezed spokes to fail--1,000
miles, 5,000, 10,000, or even 25,000 miles?
He relented when I promised to pose the question here, so
perhaps someone will speculate on how long the spokes on
what everyone agrees is an otherwise properly built wheel
should last if not squeezed.
Carl Fogel
Trevor Jeffrey
Todd Bryan wrote in message ...
>So, how do I determine when the rider's full weight will not unload a
>spoke? Do I measure that at rest? Or perhaps while dropping the laden
>bike off a 2 foot high ledge? The point is that wheels are subject to
>dynamic loads and you cannot predict whether those loads will unload
>bottom spokes. So you tension spokes as highly as possible to handle the
>highest radial load possible.
The fear of loose spokes is unfounded. As long as lateral stability is
maintained the spokes are tight enough. The requirement to measure the
tension in the spokes by plucking or gauge is not required using the method
of wheel building I have described. If it is found that the wheel becomes
wobbly it is a simple matter to turn each nipple 1/4 turn to shorten their
effective length.
The use of a drying oil assists in the tensioning of spokes and the
prevention of the nipples unwinding in use.
No I do not tension spokes as high as possible. I presume therefore
that you do and so pre-load the rim so there is a tendency to buckle. There
is no advantage in pre-loading spokes and rims, it only lessens the load
capacity of the wheel before buckling.
A rigorous analysis is not required, all has been presented. I could
tidy it up, add some detail, some pictures and some waffle here and there,
but I doubt that I'd really want to do it. Why don't you do it? Give it a
hardback cover and overprice it. With a bit of luck you may just cover the
publication costs after a few years.
Call it "The Bicycle Wheel Revealed"
TJ
Trevor Jeffrey
Jose Rizal <_@_._> wrote in message ...
>
>Just how do you do this, and how do you account for the dynamic loads
>put on the wheel which exceed the static rider/bike weight?
Put water into pan, light gas, place egg in water, bring to boil, turn off
gas.
It would help if questions were more spcific than how do you do this?
specifically which part of my explanation do you think requires further
explanation?
7/5(rider+bike+load) Front wheel loading.
As another answer explains it is a simple matter to tension the wheel a bit
more if the rider finds the wheel wobbly.
>What the hell is "a wheel which will fail safe"?
Will not lock up in the frame due to buckling.
>
>Since buckling is also load magnitude dependent, "severre" buckling
>cannot be avoided if the load is high enough, and especially since you
>only tensioned the spokes enough to take up your static weight.
>
>> Spoke quality is not an issue.
>
>Plastic spokes will be fine then.
Steel is an excellent material for bicycle spokes. Plastics are not
renowned for their ability to work in tension and I doubt any plastic could
replace the steel spoke. Aramid fibre of course is exceptionally strong and
may provide an alternative at increased cost.
TJ
Todd Bryan
> No I do not tension spokes as high as possible. I presume therefore
> that you do and so pre-load the rim so there is a tendency to buckle. There
> is no advantage in pre-loading spokes and rims, it only lessens the load
> capacity of the wheel before buckling.
Oh! I never could have imagined that things were so simple! I guess
all one really has to do is lace the wheel, tighten the nipples enough
to snug up the spokes, and voila: a bicycle wheel with truly tremendous
load capacity! It makes so much sense.
Mark McMaster
> carl...@comcast.net wrote:
>
>>
> <snip>
>
>> Spoke-squeezing is an intriguingly mysterious subject to
>> research. I remain agnostic, wavering one way and the other,
>> but haven't seen any experimental data or analyses involving
>> bicycle spokes. If you have the 3rd edition, perhaps you
>> could peek at the Wiedemer stuff and give me your thoughts
>> on it?
>
>
> you may also want to consider this question:
>
> q: elevator safety certification requires loading the cab to double
> it's "safe working load". this is to test the wire ropes that suspend
> it. the reason is that fracture mechanics predict that this process
> will typically reveal by failure any latent flaws. but, if we extend
> spoke squeezing theory, wouldn't this overload procedure also prevent
> fatigue of elevator cables?
>
> a: no. elevator cables still fatigue and need regular testing,
> inspection & replacement.
This proves nothing one way or the other about the affects
of squeezing spokes to reduce residual stress. There is no
question that reducing residual (tensile) stresses can
increase fatigue life. There is also no question that
spokes (or elevator cables) will still fatigue if the cyclic
load is high enough (i.e. above the endurance limit). The
question is whether squeezing the spokes provides any
significant beneficial reduction in residual stress, or
increases the endurance limit.
Mark McMaster
MMc...@ix.netcom.com
Trevor Jeffrey
carl...@comcast.net wrote in message ...
>He relented when I promised to pose the question here, so
>perhaps someone will speculate on how long the spokes on
>what everyone agrees is an otherwise properly built wheel
>should last if not squeezed.
It is not possible to everyone to agree on what is a properly built wheel.
I would expect spokes to last longer than it takes to wear out a road rim.
I would expect spokes to last longer than it takes to wear out 100 tyres. I
would expect spokes to last in excess of 500,000 miles with or without
overtensioning on installation.
Steel spokes are cold drawn down to a thin wire which is then annealed,
by passing through hot rollers, to remove the spring. The wire is then cut
to length, the head and thread is formed by cold working and the head
knocked over to form the bend at the end. There is a cold working through
rollers after annealing, most obviously in the form of swaged spokes
(butted).
TJ
Tim McNamara
> carl...@comcast.net wrote in message ...
>>He relented when I promised to pose the question here, so perhaps
>>someone will speculate on how long the spokes on what everyone
>>agrees is an otherwise properly built wheel should last if not
>>squeezed.
>
> It is not possible to everyone to agree on what is a properly built
> wheel. I would expect spokes to last longer than it takes to wear
> out a road rim. I would expect spokes to last longer than it takes
> to wear out 100 tyres. I would expect spokes to last in excess of
> 500,000 miles with or without overtensioning on installation.
You might expect it, and I might too, but plenty of experiences are
reported here that indicate spokes breaking within a few hundred or a
few thousand miles. And there are some reports of tens of thousands
of miles without spoke breakage- thus far most of these seem to be
from people who have used Brandt's method.
> Steel spokes are cold drawn down to a thin wire which is then
> annealed, by passing through hot rollers, to remove the spring. The
> wire is then cut to length, the head and thread is formed by cold
> working and the head knocked over to form the bend at the end.
This is the issue that Brandt claims his "stress relieving" procedure
addresses. He states there are residual stresses in the spoke at the
bend from the forming of the elbow. Stress relieving raises the
tension and causes cold setting, relieving those stresses. This in
turn results in spokes that last longer.
> There is a cold working through rollers after annealing, most
> obviously in the form of swaged spokes (butted). TJ
ISTR some spokes- DT Revolutions perhaps?- that had mid-shaft spoke
breakages because the swaging created an internal crack along the axis
of the spoke.
Tim McNamara
> The use of a drying oil assists in the tensioning of spokes and the
> prevention of the nipples unwinding in use.
In other words. it acts as a glue between the spoke and the nipple.
Wheelsmith sells a preparation that does a simiar thing, Spoke Prep.
Linseed oil is cheaper by orders of magnitude. I use 10w-30 motor
oil. My spoke nipples do not unwind in use, despite being 215 lbs and
riding 32 spoke wheels 6,000 to 7,000 miles a year. The reason for
this is not using something to glue the nipples and spokes together,
but using adeqate tension in the first place. Stuff like linseed oil
and Spoke Prep just covers for a badly built wheel.
Hmmm, this conversation seems like old times.
jim beam
ah, this explains everything! stainless steel has been developed that
has an endurance limit! and it's used in bicycle spokes!!!
no. this is one of the fundamental flaws of "the book". it cites
material behavior for mild steel, which /does/ have an endurance limit,
and then presumes to describe behavior in stanless steel, which does
not. just exactly how this lends credibility to a revolutionary means
of eliminating metal fatigue is something i have yet to come to terms with.
jim beam
yes, but brandt also advocates "correcting the spoke line" which
involves deformation significantly above that required to stress
relieve, and indeed may leave the material with even more residual
stress than it had initially. now add to that the fact that that spoke
wire is a highly cold worked material with a very high dislocation
density [and therefore full of lattice stresses] in which any further
deformation is likely to increase dislocation density rather than reduce
it, and it becomes clear that brandt really doesn't know what he's
talking about. how else could he cite mild steel deformation
characteristics in a stainless steel application, as he does in his book?
Tom Sherman
> ...
> tim, you're like a drunken finnean looking for a bit of bare-knucked
> sport on his way home from a bar. read what i said when you're sober,
> then show me one single piece of metallurgical evidence to support
> brandts bullying assertions. or your allusions to superior mental
> health come to that.
Speaking of mental health, do you have an irrational fear of capital
letters?
--
Tom Sherman – Quad City Area
Paul Kopit
opinion regarding "stress relieving", and would make that known. They
don't want their spokes to bread while in service more than anyone
else.
Paul Kopit
<tim...@bitstream.net> wrote:
>Prove him wrong. Put
>up or shut up. Frankly, jim beam old buddy old pal, I don't think you
>have the stuff.
I think you are on the right track but good science doesn't work that
way. The hypothesis needs to be proven.
Benjamin Weiner
> None of these objections, as I recall, were meant to cast
> any doubt on Mike Prime's aluminum plate test itself, which
> was not undertaken to address the stainless steel spoke
> question and seems like a reasonable test to bring up. They
> were raised to point out that the two situations may differ
> in significant ways (and were also raised probably for the
> joy of quibbling, not that we ever see any of that on
> rec.bicycles.tech).
Sure they differ. It does show that the metallurgical phenomenon
exists and is not just something Jobst made up without justification,
which is what some people seem to be arguing.
Unless you can get someone to do tests on actual spokes
that's probably as good as you can get. I don't know what
tests would prove it conclusively, perhaps sectioning and
electron micrography. There are a variety of materials tests
for flaws and stress cracks which I am no expert on, but
most of them are probably designed for much bigger pieces
than a spoke (I suspect eddy current testing is like that).
> I often wonder whether my wavering on this matter resembles
> what I had to endure with people debating who wrote
> Shakespeare. I'm not sure who's right about spoke squeezing,
> so I long for a site that patiently goes through the details
> for the layman in the way that this site explains literary
> matters:
> http://shakespeareauthorship.com
I think, even if there were workable tests, if someone tried to
write such a document it would have to teach the reader basic
physics, metallurgy, and mechanical engineering. At least
with Shakespeare, most readers understand the basics like
dates, tenses and handwriting, even if they don't know the
detailed issues about Elizabethan manuscripts, printing, and
the social position of playwrights.
Even so, I'm sure there is an Oxfordian site somewhere that tries
to refute all the arguments on shakespeareauthorship.com. To your
trained eyes, its arguments are transparently blowing smoke,
but to a layman's, it may not be so. I see similar things happening
here on r.b.tech when people talk about spokes.
> The last person whom I bored to tears about spokes raised an
> interesting question. If spoke-squeezing works, either by
> relieving stress or by other methods, and makes spokes
> practically immortal, how soon should unsqueezed spokes
> break? That is, when did I predict that the unsqueezed
> spokes would fail?
> My muttered "sooner" was dismissed as being a bit imprecise.
> I'd mentioned that some spoke squeezers claim over 50,000
> miles on failure-free spokes, so my tormentor kept asking me
> when he should expect his unsqueezed spokes to fail--1,000
> miles, 5,000, 10,000, or even 25,000 miles?
> He relented when I promised to pose the question here, so
> perhaps someone will speculate on how long the spokes on
> what everyone agrees is an otherwise properly built wheel
> should last if not squeezed.
It's completely unanswerable as is, because we don't know
anything about the use of the wheel - the weight of the rider,
on-road or off-road, rough pavement? I wouldn't trust any
answer that tried to derive this from first principles.
If the use is light enough and the build was fairly good
apart from squeezing, maybe the wheel won't break. I am not
a professional wheelbuilder so I don't have enough base
knowledge to tell you.
However, there is a substantial weight of experience. It is
very common to see posts in r.b.tech from people who are
breaking spokes on stock wheels on new bikes. Most new
good-quality bikes these days use stainless steel spokes that
are strong enough for the job. The likely suspect is an
inadequate wheelbuild. I don't have much idea how this
translates into mileage, but when people break a lot of
spokes in their wheels, I think it happens early. If a
wheel survives 10,000 miles, it isn't going to break half
the spokes at 11,000.
Trevor Jeffrey
important diversion, at the spoke crossing, to take care of itself. The
pre-shaping of the crossing point before spoke tensioning is the most
beneficial time spent in the construction of a wheel. It also saves on
component cost as the cheapest available parts may be used with success.
Over tensioning to correct spoke line stinks. All it is, is pre-loading.
Brandt advocates ought to apply the same logic to bridge building,
preloading to just under the point of collapse, and then think. There is
no argument that bicycle wheels are a special circumstance, the bicycle is
what brought along much of 19&20C engineering.
Wheels are made of metal with their rims in compression and spokes in
tension. Increase spoke tension and rim compression increases. Increase
load on bicycle and rim commpression increases. There is a maximum
compressive force that each rim can sustain without lateral support.
Pre-loading rims therefore is unacceptable. The potential consequences of a
buckled wheel compared to the loss of function of one spoke are too great on
my planet.
The reason why "stress releiving" results in a lower spoke failure is
that it will partially correct the bend of the spoke at the crossing. Much
better to specifically aim for this result. If the deviation at the
crossing is not made, the crossing point will move in and out relative to
the hub as the loaded wheel is rotated. This causes the fatigue failure of
the spoke at the hub so often reported.
If the preforming of the spoke at it's crossing is performed, the risk
of spoke loss due to fatigue failure is less than the method of
overtensioning. the MTBF is greater. Wheelbuilding is simpler, easier and
less stressfull. No rim failures is construction or on the road. Lateral
stability is improved with lower tension. The spokes act as the tensile
members the are designed to be and not as springs.
The smaller the angular deviation of the crossing the more likely you
are to get away with not pre-forming the spoke. This would explain the
popularity of x3 and x4 on a front wheel and also the use of large flange
hubs. Each of these methods can reduce the angular displacement at the
crossing so lessening the repeated bending of the spoke at the hub. My
preferred method of construction is uibtable for all rims and standard
spokes.
TJ
Tom Sherman
> ...No rim failures is construction or on the road....
Huh?
Trevor Jeffrey
Tom Sherman wrote in message <2n4d4gF...@uni-berlin.de>...
>Trevor Jeffrey wrote:
>
>> ...No rim failures is construction or on the road....
>
>Huh?
I notice reports that rims have 'tacoed' during construction and in use. I
believe this is to avoid the term buckled (a form of failure).
TJ
Tom Sherman
So the above should have read, "No rim failures IN construction or on
the road"?
Trevor Jeffrey
Tom Sherman wrote in message <2n4pleF...@uni-berlin.de>...
>>
>>>Trevor Jeffrey wrote:
>>>
>>>
>>>>...No rim failures is construction or on the road....
>>>
>>>Huh?
>>
>>
>> I notice reports that rims have 'tacoed' during construction and in use.
I
>> believe this is to avoid the term buckled (a form of failure).
>
>So the above should have read, "No rim failures IN construction or on
>the road"?
Yes, seems a bit of a wild mistype must be a comp. glitch.
Thank you.
TJ
Trevor Jeffrey
Tim McNamara wrote in message ...
>oil. My spoke nipples do not unwind in use, despite being 215 lbs and
>riding 32 spoke wheels 6,000 to 7,000 miles a year. The reason for
>this is not using something to glue the nipples and spokes together,
>but using adeqate tension in the first place. Stuff like linseed oil
>and Spoke Prep just covers for a badly built wheel.
>
>Hmmm, this conversation seems like old times.
The use of any oil will assist in the prevention of a nipple shaking
loose, a drying oil just happens to be the most successful in this
application, i.e. a wheel not overtensioned. The wheel construction is how
I describe and not what you ride. Your conversation is repeated because you
do not appear to take on board what I have wrote. Adequate tension is
accomplished when the wheel remains laterally stable under load. Further
tension unnecessarily reduces the available load capacity of the rim and so
of the wheel.
TJ
jim beam
you raise some very interesting points.
first is, does stress relief exist? yes, but the /real/ question is
whether it's relevant to this application. jobst clearly didn't make it
up, but he doesn't seem to understand it either. just like he used the
phenomenon of elastohydrodynamic separation as an explanation of why
headsets brinelled and hubs didn't. fact is, e.h.d.s. is not operative
in hubs at normal roads speeds, but his apparent ignorance of that fact
didn't stop him bullying folks here about it for years. similarly, he
explained stress relief in terms of deformation without work hardening,
a phenomenon that is present in mild steels, and cites such material
behavior in his book. unfortunately, that phenomenon is not known to
exist in stainless steels. perhaps that's why he doesn't understand why
the first stress/strain graph shown in his book is incorrect. the fact
that that graph is not replicated in the "real world" stress/strain
graphs he obtains from actual spoke testing as shown in the back of his
book does not appear to have registered.
second is fatigue testing. "the book" sets out a number of topics, and
proceeds to explore them in a number of ways. his tied & soldered
spokes testing is an example of where he has actually done quantitative
testing and publishes results. his "stress relief" theory on the other
hand is entirely subjective, amounting to "i say it works". he offers
no quantitative substantiation for that claim whatsoever. sure,
pointing at the phenomenon of metallurgical stress relief may sound
plausible, but his kind of usage is not anything i've ever seen cited in
literature for this kind of application. it would make millions of man
hours of research into fatigue over the last 100+ years irrelevant if
all we had to do was give a component a quick tweak in order to give it
infinite fatigue life characteristics. the coincidence of his theory
appearing at about the same time as real world materials advances like
vacuum degassed stainless steels becoming available in quantity is not
something lost on jobst. he even alludes to their existence in his
book, but tellingly fails to pursue their relevance or importance.
third, and related to the above, is spoke brand. this is most
definitely relevant. i have a large collection of broken spokes
collected from various wheels of friends and acquaintances over the last
few years. with the exception of those that have been physically
damaged thereby initiating fatigue at this point, they are all "unknown"
brands. in a highly competitive market, saving even a couple of bucks
on some no-name spokes on stock wheels where no one knows or cares what
they are is going to help profitability. the usual explanation here on
r.b.t. is that these wheels were "not stress relieved". failure to see
the relevance of the material quality employed in building that wheel
may not be convenient to "the theory", but it sure is a substantial blow
to credibility.
lastly, you mention early failures. this is actually consistent with a
lot of real world fatigue applications, automotive gearboxes being
another example. it's often called "the bath tub curve", where the
probability of failure starts comparatively high, rapidly drops, then
after an extended period, starts to climb again so the line on the graph
is a long shallow "u" like a bath tub. if the component can get through
the first few hours of use, its probability of survival increase
substantially. indeed, a lot of s/n curves show scatter at the low
cycle end of the graph for this reason and very low cycle failures are
often ignored.
dianne_1234
wrote:
>his "stress relief" theory on the other hand is entirely subjective,
Can you suggest some ways such a theory might be tested?
Mark McMaster
Ah, as usual, you dodge the question rather than addressing
it. Whether or not a material has a true endurance limit or
not doesn't change the question of whether momentarily
overloading the spokes can reduce residual stress and/or
increase fatigue life, which is central to the argument.
But then, you appear to be far more interested in being a
contrarian than to actually knowing what is going on.
That momentarily overloading the spokes results in increased
spoke life has been reported by many sources. Not just here
in the RBT newsgroup but by others as well, both inside and
outside the industry. For example, here is the Bontrager
wheel manual which shows how their "wheel stressor" is used
to momentarily overload the spokes:
http://www.bontrager.com/workshop/documents/wheel_manual.pdf
So, just what is the mechanism that causes the spokes to have
improved fatigue life after momentarily overloading them?
If you
do not believe that Brandt is correct about relieving residual
stresses in the spokes, than what other explanation do you
propose?
And about stainless steel having an endurance limit:
Whether any material has a true and absolute endurance limit
is often debated. However, under a common usage of the term
(fatigue strength at 10^7 cycles is a common definition),
the types of stainless steel used in spokes does have an
endurance limit (but then, you probably knew that). We can
dispose of that red herring.
Here are some data on some stainless steels of the type used
in spokes (for example, Wheelsmith uses 304, DT uses 18-8),
including their endurance limits:
http://www.hghouston.com/ss_cwp.html
http://www.band-it-idex.com/pdfs/stainless_steel/302_305.pdf
http://www.askzn.co.za/tech/tech_grade_304.htm
Mark McMaster
MMc...@ix.netcom.com
Mark McMaster
Sorry, it doesn't work this way. Because the spokes are far
stiffer than the rim, very little of the load is supported
by the rim at all when the wheel is loaded - at least not
until the spokes go slack. But then the wheel losses the
lateral stability you seek, so asking the rim to support the
load is a poor idea.
Mark McMaster
MMc...@ix.netcom.com
carl...@comcast.net
Dear Dianne,
One way would be to take before and after pictures that
either do or do not show microscopic changes in a squeezed
spoke.
(My understanding of such matters is so feeble that I should
add that "microscopic" may need to be replaced by "x-ray
diffraction" or even more exciting technologies involving
terms like "lattice" and "crystal" and "scanning
microscope"--or possibly "bi-focals.")
Unfortunately, this requires more than just swiping a spoke
across the bar-code reader at the grocery store, so I've
stopped holding my breath while waiting for such evidence to
appear.
Another test would be to find an industry in which a very
similar process has been developed and tested. The obvious
place to look would be spoked motorcycle wheels, or even the
spoked wheels of obsolete British sports cars. There might
be a paper detailing testing of spoke stress-relief lurking
out there somewhere. (If none can be found, this is not
proof that the theory is wrong--spokes in other applications
might be so over-engineered that stress-relief is pointless,
or the wheels elsewhere might just be badly built.)
A practical test would involve taking several brands of
modern spokes and subjecting batches of them to some Rube
Goldberg machine that mimics the rapid reduction of
otherwise steady tension in a rolling bicycle wheel for
millions of cycles. If the stress-relieved batch outlasted
the unsqueezed batch, it would settle the matter.
Because the subject is of little interest outside
rec.bicycles.tech, expensive and serious testing beyond
anecdote is unlikely. Perhaps someone will find a peer
reviewed paper on spokes (as opposed to related but arguably
different matters), but I expect that it would have turned
up by now if such a study existed.
(Again, the absence of a study is not proof for or against
the theory--and the Wiedemer citation that I assume appears
in the 3rd edition of "The Bicycle Wheel" might be
specifically on spokes. I take comfort in the fact that I'm
apparently not the only member of rec.bicycles.tech too
cheap to buy the newer edition.)
A less expensive (and less conclusive) test would be to find
a large group of dedicated bicyclists unaware of the spoke
squeezing theory and find out how often their spokes break.
The only group that I can think of that might fit this
description would be the Keirin racers of Japan, but it
wouldn't surprise me if they've thoughtlessly heard of the
stress-relief theory and ruined themselves as a control
group.
In any case, we could only compare such a group to a very
small, self-selected group here on rec.bicycles.tech. A
double-blind study is hard to arrange when there's little
interest and the testing is expected to take a long time.
One test that occurred to me is to find out what the spoke
squeezing theory predicts will happen to unsqueezed spokes.
Obviously, unsqueezed spokes are supposed to fatigue and
fail sooner than apparently immortal squeezed spokes, but
how much sooner? That is, given 72 spokes on a pair of
wheels built as similarly as possible, except for the spoke
squeezing, how many will break in each set of wheels in ten,
twenty, fifty, or a hundred thousand miles of similar
riding?
I haven't seen any such predictions, but making them might
help put the debate in perspective. My impression is that
those who doubt the theory would predict no significant
difference in spoke failure rates.
I have no idea what kind of failure rates would be predicted
for unsqueezed spokes by spoke-squeezing proponents, but it
would be fascinating to see what kind of predictions would
be made and how they would be supported.
Time to see how my troop of monkeys is doing on duplicating
the First Folio.
Carl Fogel
Weisse Luft
Mark McMaster Wrote:
> jim beam wrote:[color=blue]
>
>
> So, just what is the mechanism that causes the spokes to have
> improved fatigue life after momentarily overloading them?
> If you
> do not believe that Brandt is correct about relieving residual
> stresses in the spokes, than what other explanation do you
> propose?
>
> And about stainless steel having an endurance limit:
> Whether any material has a true and absolute endurance limit
> is often debated. However, under a common usage of the term
> (fatigue strength at 10^7 cycles is a common definition),
> the types of stainless steel used in spokes does have an
> endurance limit (but then, you probably knew that). We can
> dispose of that red herring.
>
> Here are some data on some stainless steels of the type used
> in spokes (for example, Wheelsmith uses 304, DT uses 18-8),
> including their endurance limits:
>
> http://www.hghouston.com/ss_cwp.html
> http://www.band-it-idex.com/pdfs/stainless_steel/302_305.pdf
> http://www.askzn.co.za/tech/tech_grade_304.htm
>
>
> Mark McMaster
> MMc...@ix.netcom.com
The 300 series of stainless steels are 18-8 stainless steels with
slight modifications between the different numbers. Since the 300
series is an AISI designation, European and other areas are not obliged
to call them with this designation.
These stainless steels are all austenitic, meaning they have no
ferromagnetic properties in their annealed state. Plastic deformation
changes this structure to partially ferritic structure making highly
cold worked stainless steels (with some exceptions like 316, a
molybdenum modification of 18-8) slightly magnetic. In addition, this
crystaline change greatly increases the yield strength and is HIGHLY
ansitropic in its effects.
The overstressing procedure forces changes in the elbow, causing it to
conform to the flange hole AND causing deformation of the flange hole
itself. Because of this, the stresses of the bend is now spread over a
longer range of the bend. Cyclic loading consistent with riding is now
operating this joint in a purely elastic range rather than exposing
tiny areas of the bend to very high stresses over very small areas.
This is no different than some pressure vessel codes (notably French, I
forget the code) that hydrostatically test pressure vessels at much
higher pressures than the design. This is termed "auto frettage" and
confers much higher cyclic life to the vessel.
--
Weisse Luft
carl...@comcast.net
Dear Mark,
I'm pleased to see the Bontrager stressor tool, which does
indeed show a serious attempt to calibrate how much the
spokes are being stretched. Thanks for the link.
Being hopelessly contrarian even when wavering on the fence,
however, I have to ask if that same link proves that Jobst
is mistaken about paired spokes being antiquated nonsense?
That is, yes, they make a very nice tool for stretching
spokes, but the question is what the effect is of stretching
spokes, not how precisely it can be done.
That people have reported increased spoke life is true, but
the question is whether their reporting is accurate. They
may be quite right, but they may also be replicating the
tying and soldering reports that Jobst's testing demolished.
Do you know of any formal studies showing that squeezed or
stretched spokes enjoy a longer life? I'm sure that
Bontrager believes it, just as I'm sure that Jobst and
others believe it.
Unfortunately, it's a difficult matter to resolve either way
because any physical change in an actual spoke would
probably be on such a microscopic level that it would very
expensive to photograph and any statistically significant
testing might be frighteningly tedious.
Again, the lack of testing is not evidence that the theory
is wrong, just an indication of how beastly difficult it may
be: "The fatigue resistance of spokes was not tested for
lack of suitable equipment." --"The Bicycle Wheel," 2nd
edition, Part III, "Equations and Tests"
It's worth pointing out that those who deny the spoke
squeezing theory seem to be in the same boat in that their
testing is at least as anecdotal, leaving laymen like me to
admire all the fury and theory and to incline to agree with
whichever post I read last.
I suspect that the spokes don't care how much we abuse each
other and that they simply fatigue in a pattern that I
haven't yet seen documented. Some day, if I'm lucky, someone
will rub my nose in a knock-down, indisputable study, crow
about how the testing proves that their arguments were
correct, sneer at my wishy-washiness, and win my Fury
RoadMaster as a prize.
Carl Fogel
carl...@comcast.net
<Weisse.Lu...@no-mx.forums.cyclingforums.com> wrote:
[snip metallurgy]
>The overstressing procedure forces changes in the elbow, causing it to
>conform to the flange hole AND causing deformation of the flange hole
>itself. Because of this, the stresses of the bend is now spread over a
>longer range of the bend. Cyclic loading consistent with riding is now
>operating this joint in a purely elastic range rather than exposing
>tiny areas of the bend to very high stresses over very small areas.
>
>This is no different than some pressure vessel codes (notably French, I
>forget the code) that hydrostatically test pressure vessels at much
>higher pressures than the design. This is termed "auto frettage" and
>confers much higher cyclic life to the vessel.
Dear Weisse,
Forgive my layman's summary of what seems rather clear, but
I want to be sure that I'm following you.
You agree with the spoke-squeezing side of the debate that
overstressing significantly increases spoke life, but you
believe that it has nothing to do with internal stress
relief and is instead a matter of a better mechanical mating
of the spoke elbow with the hub hole that spreads the load
out and greatly reduces the stress?
If so, would magnified before and after pictures of the hub
hole show a difference?
I have a vague notion that you've mentioned scuba equipment
in passing. Is that what you have in mind when you speak of
pressure vessels? I'm hoping to wander off into "auto
frettage," but can't figure out how it resembles the spoke
hole and elbow situation.
Thanks,
Carl Fogel
David Damerell
>The type of guttersniping you indulge in does not advance the
>discussion one whit. Over the years we've had recurrent posters with
>the gunslinger mentality who come into town aiming to knock off the
>big guy. You seem to be just another one of this species. I suspect
>that many of those posters have been the same person hiding behind
>different personae, due to consistencies in writing style and
>conceptual framework. You don't raise chickens, by any chance?
Er, we already know that "jim beam" is a sock puppet for "tux lover", a
persona retired when it acquired too much of a reputation as a nut case.
That cannot be far away for "jim beam", since as far as I can see if
Brandt posted that wheels are round and spokes are thin it would net
another dose of froth.
--
David Damerell <dame...@chiark.greenend.org.uk> Distortion Field!
Peter Cole
>
> ah, this explains everything! stainless steel has been developed that
> has an endurance limit! and it's used in bicycle spokes!!!
>
> no. this is one of the fundamental flaws of "the book". it cites
> material behavior for mild steel, which /does/ have an endurance limit,
> and then presumes to describe behavior in stanless steel, which does
> not. just exactly how this lends credibility to a revolutionary means
> of eliminating metal fatigue is something i have yet to come to terms with.
>
http://www.hghouston.com/ss_cwp.html
Trevor Jeffrey
Mark McMaster wrote in message <410DB583...@ix.netcom.com>...
>Sorry, it doesn't work this way. Because the spokes are far
>stiffer than the rim, very little of the load is supported
>by the rim at all when the wheel is loaded - at least not
>until the spokes go slack. But then the wheel losses the
>lateral stability you seek, so asking the rim to support the
>load is a poor idea.
To what you are referring does not work I cannot make out. The spokes
are tensile members so need to be resistive to stretch and the rim is a
compressive member so needs to be resistive to squash. One is the complete
opposite of the other. The two are not comparable to each other. Aluminium
is good in compression but not in tension, this is the way of the world,
aluminium rims and steel spokes. If the rim did not support the load it
would not need to be there. It either does or it does not, extraneous items
are most usually omitted on a human powered vehicle. Rims are essential
part of the wheel and bear all the load. What else could possible transmit
the force between tyre and spokes?
TJ
Trevor Jeffrey
Mark McMaster wrote in message <410DB4F5...@ix.netcom.com>...
>So, just what is the mechanism that causes the spokes to have
>improved fatigue life after momentarily overloading them?
Shaping the spoke at the crossing point reduces lateral movement at the
crossing causing angular displacement at the hub with the resultant early
spoke failure due to fatigue. Overtensioning the spokes goes someway to
achieving this unintentionally.
TJ
Trevor Jeffrey
Weisse Luft wrote in message ...
>These stainless steels are all austenitic, meaning they have no
>ferromagnetic properties in their annealed state. Plastic deformation
>changes this structure to partially ferritic structure making highly
>cold worked stainless steels (with some exceptions like 316, a
>molybdenum modification of 18-8) slightly magnetic. In addition, this
>crystaline change greatly increases the yield strength and is HIGHLY
>ansitropic in its effects.
>
TJ
Peter Cole
>
> The overstressing procedure forces changes in the elbow, causing it to
> conform to the flange hole AND causing deformation of the flange hole
> itself. Because of this, the stresses of the bend is now spread over a
> longer range of the bend. Cyclic loading consistent with riding is now
> operating this joint in a purely elastic range rather than exposing
> tiny areas of the bend to very high stresses over very small areas.
Practically speaking, whether momentary overloading increase spoke fatigue
life by reducing residual manufacturing stresses or by "bedding in" the
spoke/flange interface is immaterial, as long as it works, it's a procedure
that should be followed. For the "bedding" theory to be correct, it would
require that the bulk material in both the spoke and flange to be taken beyond
yield. I don't think that's the recommended practice. Your version of
"bedding", since it involves higher forces, would necessarily also perform the
reduction of residual stresses, so the claim that it works by that particular
mechanism would seem impossible to prove. In fact, those of us who don't
stress relieve to yield, yet observe improved spoke lifetimes, would seem to
have experiences which refute that theory.
jim beam
fogel pretty much says it all. what /i/ would do is just set up a
fatigue testing machine and start stretching.
other ways to detect residual stress include x-ray diffraction, but
obviously, that's much more of an industrial research/academic exercise
rather than something we can replicate "at home".
jim beam
there's plenty of stuff out there on high tensile wire.
Weisse Luft
Peter Cole Wrote:
> "
> Practically speaking, whether momentary overloading increase spoke
> fatigue
> life by reducing residual manufacturing stresses or by "bedding in"
> the
> spoke/flange interface is immaterial, as long as it works, it's a
> procedure
> that should be followed. For the "bedding" theory to be correct, it
> would
> require that the bulk material in both the spoke and flange to be taken
> beyond
> yield. I don't think that's the recommended practice. Your version of
> "bedding", since it involves higher forces, would necessarily also
> perform the
> reduction of residual stresses, so the claim that it works by that
> particular
> mechanism would seem impossible to prove. In fact, those of us who
> don't
> stress relieve to yield, yet observe improved spoke lifetimes, would
> seem to
> have experiences which refute that theory.
Yielding occurs only in a partial cross section of the spoke during the
stress relieving process. Because the entire cross section does not go
to yield, the tension can and does remain the same.
Anisotropic means properties that differ with respect to axis. A very
common anisotropic material would be wood.
With regard to cyclic fatigue, one has to only look at the spring
industry to see what works. For long life, most springs are entirely
cold worked, that is no post forming heat treatment is used. That cold
working is the same as the final stress relieving process some of us
follow when wheel building.
Now on compression, tension, aluminum and stainless. Its true aluminum
is best in compression while spokes can only take a tensile load but in
a wheel, we have a pretensioned structure. That spoke takes a
compressive load, manifested as a decrease in tension. And the wheel
is under a compressive load from the sum of the sopke tensions but it
also can take a tensile load, manifested by a reduction in the
compressive stress.
--
Weisse Luft
jim beam
"directional" is a simple translation. wood is anisotropic. metals get
like this when their grains are all elongated in the same direction,
wire being the classic example.
jim beam
gotta scram for work so let's chat later, but be careful when talking
about endurance limits - they're easily confused with fatigue limits,
which may sound the same but are techically very different.
Weisse Luft
carl...@comcast.net Wrote:
> On Mon, 2 Aug 2004 13:58:26 +1000, You agree with the spoke-squeezing
> side of the debate that
> overstressing significantly increases spoke life, but you
> believe that it has nothing to do with internal stress
> relief and is instead a matter of a better mechanical mating
> of the spoke elbow with the hub hole that spreads the load
> out and greatly reduces the stress?
>
> If so, would magnified before and after pictures of the hub
> hole show a difference?
>
> I have a vague notion that you've mentioned scuba equipment
> in passing. Is that what you have in mind when you speak of
> pressure vessels? I'm hoping to wander off into "auto
> frettage," but can't figure out how it resembles the spoke
> hole and elbow situation.
>
> Thanks,
>
> Carl Fogel
Yes, you can easily see the deformation from the spokes with only
slight magnification.
On pressure vessels, I was not covering any compressed gas bottle but
rather lower pressure vessels fabricated by welding and used for
storing materials like LPG and the like. Some are actually formed by
pressure.
--
Weisse Luft
Trevor Jeffrey
Peter Cole wrote in message <5PqPc.195614$a24.110765@attbi_s03>...
>
>Practically speaking, whether momentary overloading increase spoke fatigue
>life by reducing residual manufacturing stresses or by "bedding in" the
>spoke/flange interface is immaterial, as long as it works, it's a procedure
>that should be followed.
I do not believe that all constructors using the method of
overtensioning spokes have had an equal benefit. As I have said previously,
overtensioning, accidentally, partially forms the bend in the spoke at the
crossing point so as to reduce the angular displacement at the hub during
the cyclic variation of loading. With a reduced angular displacement at the
hub interface the MTBF is increased due to the lowered rate of fatigue. The
fatigue rate is primarily dependant upon the angular displacement and not
the tensile force or variation in thereof.
Relatively the momentary overloading is a waste of time compared to
specifically shaping the spoke correctly.
TJ
Trevor Jeffrey
Ride bike hard and nip up a little if found necessary.
TJ
Trevor Jeffrey wrote in message ...
Trevor Jeffrey
Weisse Luft wrote in message ...
>compressive load, manifested as a decrease in tension. And the wheel
>is under a compressive load from the sum of the sopke tensions but it
>also can take a tensile load, manifested by a reduction in the
>compressive stress.
Please mind your language. A decrease in tension is not compression. It
cannot be so. It is the rim which is under a compressive load and the
spokes under a tensile load, it is therefore wrong to declare the whole
wheel as under a compressive load. You are confused.
TJ
Weisse Luft
No, I am not confused. If you know how to draw a free body diagram,
you will see the error in your ways if you can accurately measure the
rim deflection.
Pretensioned structures easily confuse those who study them. Rest
assured, a wheel stands on its spokes, be they wire, rope or pegs.
--
Weisse Luft
Peter Cole
message news:Weisse.Lu...@no-mx.forums.cyclingforums.com...
>
> Peter Cole Wrote:
> > "
> > Practically speaking, whether momentary overloading increase spoke
> > fatigue
> > life by reducing residual manufacturing stresses or by "bedding in"
> > the
> > spoke/flange interface is immaterial, as long as it works, it's a
> > procedure
> > that should be followed. For the "bedding" theory to be correct, it
> > would
> > require that the bulk material in both the spoke and flange to be taken
> > beyond
> > yield. I don't think that's the recommended practice. Your version of
> > "bedding", since it involves higher forces, would necessarily also
> > perform the
> > reduction of residual stresses, so the claim that it works by that
> > particular
> > mechanism would seem impossible to prove. In fact, those of us who
> > don't
> > stress relieve to yield, yet observe improved spoke lifetimes, would
> > seem to
> > have experiences which refute that theory.
>
> Yielding occurs only in a partial cross section of the spoke during the
> stress relieving process. Because the entire cross section does not go
> to yield, the tension can and does remain the same.
Of course. But that's what's wrong with the "bedding" argument, it requires
yield at the elbow and at the flange.
Peter Cole
"Trevor Jeffrey" <Trevor_...@beeeb.net> wrote in message
news:celklo$c8q$2$8300...@news.beeb.net...
I believe what you're concerned about is what Jobst Brandt describes as
"improving the spoke line". The difference being that his concern is bends
(loaded) at the flange and nipple, while you worry about the crossing. The
concept seems the same, only the forces seem larger in the misalignments he
describes.
>
>
>
Jose Rizal
>
> Jose Rizal <_@_._> wrote in message ...
> >
> >Just how do you do this, and how do you account for the dynamic loads
> >put on the wheel which exceed the static rider/bike weight?
>
> Put water into pan, light gas, place egg in water, bring to boil, turn off
> gas.
> It would help if questions were more spcific than how do you do this?
> specifically which part of my explanation do you think requires further
> explanation?
The question followed your last statement "tighten to a point where the
riders (sic) full weight does not releive (sic) the bottom spoke"
immediately. It's not hard to figure out which part the question refers
to.
> 7/5(rider+bike+load) Front wheel loading.
Where does this magic figure come from?
> As another answer explains it is a simple matter to tension the wheel a bit
> more if the rider finds the wheel wobbly.
Trial and error is what you're suggesting.
> >What the hell is "a wheel which will fail safe"?
>
> Will not lock up in the frame due to buckling.
There is no such thing. Buckling is largely dependent on the magnitude
and direction of the load on the rim. A large enough load can buckle a
wheel enough to wrap it around your fork.
> >Since buckling is also load magnitude dependent, "severre" buckling
> >cannot be avoided if the load is high enough, and especially since you
> >only tensioned the spokes enough to take up your static weight.
> >
> >> Spoke quality is not an issue.
> >
> >Plastic spokes will be fine then.
>
> Steel is an excellent material for bicycle spokes. Plastics are not
> renowned for their ability to work in tension and I doubt any plastic could
> replace the steel spoke. Aramid fibre of course is exceptionally strong and
> may provide an alternative at increased cost.
Hence spoke quality is an issue.
Jose Rizal
> Jose Rizal wrote:
> > jim beam:
> >>it's only the practical issues
> >>of price, of needing a spoke that resists torque sufficiently to be able
> >>to tighten a nipple and indeed, ability to thread a nipple in the first
> >>place that lead to the use of single strand.
> >
> > This made-up story doesn't even look nor sound good. Spokes still do
> > twist, and a threaded nipple is not the only way to have an adjustable
> > tightening mechanism on a rim.
>
> what method do you propose? the threaded nipple method is cheap,
> reliable and has stood the test of time. and of course spokes still
> twist, but not as much as the equivalent multi-strand. brake cable's
> about the same as a spoke, try the comparision.
This has nothing to do with the claim you made before: "it's only the
practical issues of price, of needing a spoke that resists torque
sufficiently to be able to tighten a nipple and indeed, ability to
thread a nipple in the first place that lead to the use of single
strand."
> >
> >>>Does it matter that they bend
> >>>around pulleys in a constant side-to-side flexing different
> >>>than spokes?
> >>
> >>yes, and those pulleys cause wear and bending stresses, but that's why
> >>you use multi-strand in the first place.
> >
> > Hence spokes and cable are not the same "application".
>
> maybe your definiton of tension is different to mine.
Bending stresses do not result in only tension in cables or solid rods.
One side will experience compression. You do not have this issue with
spokes.
> >>also, one strand breaking in a
> >>rope of 100 leaves 99 others - pretty comforting.
> >
> > Nonsense. If a cable is loaded such that a strand breaks, the effective
> > cross section of the cable is reduced and hence the load results in a
> > higher stress for the remaining strands, which will rapidly lead to
> > failure of the cable. If a strand was broken by other than a load (eg
> > cut), the same effect on cross section will be observed. You can't cut
> > a strand on a solid spoke.
>
> read some fracture mechanics. crack propagation in a single piece leads
> to failure of the whole. fracture of a single strand does not.
Dodging again. Study some basic engineering. Fracture of a single
strand in a cable decreases the load-bearing cross-section of the cable,
which decreases the maximum load it can withstand. If the break happens
because of a high enough load, the rest of the strands will experience
higher stresses since there are less of them, and the cable will
eventually fail.
> next
> time you fly, check out the skin of the plane and notice that it's made
> of many parts riveted together. is this because manufacturers can't
> weld? no, it's because crack proagation in one piece does not propagate
> to the whole - it's a policy of fracture containment.
An absolutely ridiculous contention. A plane's skin is NOT a
significant load bearing structure. The FRAME is. An airplane's skin
is riveted for ease of manufacture, assembly and replacement. It has
nothing to do with "fracture containment".
So to you a cable = spoke = airplane skin. These are erroneous
comparisons.
> >>and there's a small
> >>degree of freedom to move between strands which reduces cross sectional
> >>stress considerably.
> >
> > Again, nonsense. What can move between strands? The only way to move
> > loads between strands is if the strands are able to move along the
> > cable's length. This is a bad event since the strands will not take up
> > the load evenly amongst themselves.
>
> take a cable and cut the end exactly square. then bend it about some
> kind of mandrel. notice how the end is no longer square and the strands
> are staggered? they move relative one to another. this is why rope is
> flexible.
And so? The ends of elevator cables are not free; nor of any cables
used in any load-bearing application. These are crimped/welded/looped
together to prevent movement of the strands relative to each other. One
of the reasons this is done is to ensure that the tensile load is shared
equally amongst the strands.
Weisse Luft
Jose Rizal Wrote:
>
> Bending stresses do not result in only tension in cables or solid
> rods.
> One side will experience compression. You do not have this issue with
> spokes.
> strand in a cable decreases the load-bearing cross-section of the
> cable,
> which decreases the maximum load it can withstand. If the break
> happens
> because of a high enough load, the rest of the strands will experience
> higher stresses since there are less of them, and the cable will
> eventually fail.
> significant load bearing structure. The FRAME is. An airplane's skin
> is riveted for ease of manufacture, assembly and replacement. It has
> nothing to do with "fracture containment".
>
> So to you a cable = spoke = airplane skin. These are erroneous
> comparisons.
> And so? The ends of elevator cables are not free; nor of any cables
> used in any load-bearing application. These are crimped/welded/looped
> together to prevent movement of the strands relative to each other.
> One
> of the reasons this is done is to ensure that the tensile load is
> shared
> equally amongst the strands.
If you EVER get compression in a strand of wire rope (cable is for
television), I want to be far away because something BAD is going to
happen. Wire rope unwinds when you put it in compression. Wire rope
has a lower elastic modulus than say a spoke. Someone needs to read up
on Roebling et al.
Its unlikely that failure of a single strand in a wire rope will cause
any failure given the lower elastic modulus of wire rope. Yes, you can
make it fail but the analogy here is not accurate.
And yes, an airplanes skin IS an IMPORTANT part of the total structure.
I learned this back when I was a kid building model sailplanes. The
structure is WEAK until the covering (silkspan, fabric or any of the
shrinkable Mylar films) is applied, shrunk and painted. When the wing
is positively loaded, the tension in the top is partially relieved
while that on the bottom surface increases. For ultra high performance
aircraft, the first third or so of the wing is sheeted in balsa, obeechi
or light ply because no covering is strong enough for the compression.
Enough aircraft, I forgot more than you know now.
Wire ropes are ALWAYS wound with tension to ensure the inner strands do
not go into compression. Since the wire is helical, the stresses are
normalized except for the CORE which is usually INDEPENDENT as in
Independent Wire Rope Core (IWRC).
--
Weisse Luft
Trevor Jeffrey
Peter Cole wrote in message ...
>
>"Trevor Jeffrey" <Trevor_...@beeeb.net> wrote in message
>news:celklo$c8q$2$8300...@news.beeb.net...
>> overtensioning spokes have had an equal benefit. As I have said
previously,
>> overtensioning, accidentally, partially forms the bend in the spoke at
the
>> crossing point so as to reduce the angular displacement at the hub during
>> the cyclic variation of loading. With a reduced angular displacement at
the
>> hub interface the MTBF is increased due to the lowered rate of fatigue.
The
>> fatigue rate is primarily dependant upon the angular displacement and not
>> the tensile force or variation in thereof.
>> Relatively the momentary overloading is a waste of time compared to
>> specifically shaping the spoke correctly.
>
>I believe what you're concerned about is what Jobst Brandt describes as
>"improving the spoke line". The difference being that his concern is bends
>(loaded) at the flange and nipple, while you worry about the crossing. The
>concept seems the same, only the forces seem larger in the misalignments he
>describes.
>
cyclic rotation and associated variance in spoke loading leading to that
movement. I am also concerned about the lateral stability of the rim. The
failure point is not the source of the problem. The fatigue failure of
spokes at the hub interface will generally be due to not pre-forming the
spoke at its crossing with the result that the crossing point moves in and
out with cyclic load variance, and also torque applied to the rear wheel,
bending the spoke at its contact point with the hub. Same as snapping a
paper clip, bend it back and forth many times and it breaks.
On wheels with spokes not shaped at the crossing point.
If you take a straight edge to your 32x3 or what have you, lay it upon a
spoke and slacken off a nipple, you will clearly see the spoke bend into the
path of least resistance. Not a nice clean straight line required of a
tensile component but loopy. When tight, the forces still remain, as each
spoke in a pair fights against its brother. The tighter spoke will push
harder and the not so tight will give because it is acting as a spring
instead of a tensile member.
If the spokes are pre-formed the spokes stop behaving as springs and
the lateral stability of the wheel is much improved along with increased
spoke life.
TJ
Trevor Jeffrey
weight
Dynamic loads
If the wheel is built to cope with a load of 7/5(rider + bike + luggage)
this will be found to be adequate on a road bike. The capability of the
wheel is simply tested with a weight equivalent to the calculated maximum
force. The calculation is based on maximum wheel load attained on a front
wheel during braking assuming a co-efficient of friction of almost 1 on a
flat road(use of trigonometry). Maximum braking in a bend with positive
banking may see this force may exceeded. I do not know whether the same
test figure could be used for a track sprinter, but expect it to be not far
off.
Tensioning a wheel with pre-formed spokes.
There is some trial and error until a person becomes practised and
therefore skilled and so knows the particular feel with the spoke key as
when to stop. If the mechanic starts with the spokes just a little bit
tighter than slack then adds 1 turn and tests by placing weight on axle with
rim on floor and it is found to be loose add 1/2 turn to all nipples. The
torque required to turn the nipples will quickly increase and be felt in the
fingers. This is the time to make any truing up, winding in the odd, not so
tight spokes, as necessary, which will be found much easier than with spokes
not pre-formed. Test again, add 1/4 turn if necessary. When suitably
tensioned it should be found that all nipple movements will have an effect
on rim position. Stiff , heavy rims may make this difficult to see without
some form of indicator.
The mechanic, after satisfying himself than all spokes are working
equally, judged by equal rim movement with nipple turn, and that the rim
will support the riders weight without reduction in lateral stability,
judged by attempting to wiggle the bottom nipple in the spoke hole, can
allow the rider to take a test ride.
If the rider returns and says the wheel was wobbly, add 1/4 turn to all
nipples and true up. try again or add load, ask rider to ride harder. If
at any time the rider feels a wobble it is simple to add 1/4 turn and true
up. A skill is something learnt with practice, and lots of testing and
re-testing will be eliminated with experience of the method. Familiarity
with the components using will also help to cut down the number of steps
and uncertainty which accompanies any new method and associated skill. The
use of the dynamic load calculation with static test would be the preferred
method for a professional wheelbuilder.
The likelihood of a wheel buckling that will lock up in the frame is
greatly reduced with my preferred method of building a wheel, as the
technique results in a wheel with a greater lateral stability and the lower
compression levels in the rim allow a greater overhead available for dynamic
load due to impact.
Commonly available cheap steel spokes are required. It is unnecessary
to seek out a particular brand or type.
The load required to buckle my regular wheels would most probably bend the
forks or frame first.
TJ
Trevor Jeffrey
Weisse Luft wrote in message ...
>you will see the error in your ways if you can accurately measure the
>rim deflection.
>
>Pretensioned structures easily confuse those who study them. Rest
>assured, a wheel stands on its spokes, be they wire, rope or pegs.
Thou protests too much.
There is no point to a diagram. Only those who wish to manipulate figures
and turn tension into compression to validate an improper method of
wheelbuilding feel a need to do this. The confusion lies in the figures.
It is diagrams with little arrows and numbers whose vectors do not add up
which confuse. And there no way on earth I will draw a 3D vector diagram
for something I can hold in my hands. The complication is the mask for JBs
method.
TJ
carl...@comcast.net
<Trevor_...@beeeb.net> wrote:
>One spoke without pre-tensioning is more than adequate to support my static
>weight
>
Dear Trevor,
?
Carl Fogel
Mark McMaster
As far as the role of the rim, it's main role is supply a
continuously round surface to mount the tire, to have a
sufficient compressive strength allow the spokes to be
pre-tensioned, and to have sufficient lateral strength to
bear the alternating side to side forces of the spokes on
each side of the wheel. For a wheel with a standard
compliments of spokes, the rim is not required to have any
strength to radial forces - it is the spokes, not the rim
that supports the radial load. If the rim were constructed
of many small hinged segments instead of being a continuous
arch, the wheel would still be able to support its load.
As I'm sure you'll agree, the compression on the rim is
caused by the spoke tension (i.e., the spokes pull radially
inward, attempting to circumferentially compress the rim).
If you had looked at the analyses of spoke tension changes
when a wheel is loaded more carefully, you would see that
the summation of the spoke tensions _decrease_ when a wheel
is loaded. In other words, there are large spoke tension
decreases directly at the bottom of the wheel, and only very
small spoke tension increases elsewhere around the rim. The
total sum of the spoke tension increases is far less than
the sum of the spoke tension decreases. Although there may
be some increases in rim compression around parts of the
wheel due to the small spoke tension increases, they are
very small.
If you are really concerned about rim compressive strength,
you should focus on braking forces - the only loading mode
that can add any substantial compression on the rim. This
is because this loading mode can apply a high load
tangential to the rim. Radial loads mostly apply the load
to the rim in bending - and since the spokes are so stiff,
as long as they remain in tension, the bending of the rim
will be minimized.
But you are an expert on wheels, so you knew all this.
Mark McMaster
MMc...@ix.netcom.com
Tom Sherman
Trevor has obviously purchased a pair of Citroën Monospoke wheels from
Sheldon Brown.
<http://www.sheldonbrown.com/nanodrive/index.html>.
--
Tom Sherman – Quad City Area
B.B.
"Trevor Jeffrey" <Trevor_...@beeeb.net> wrote:
Relative to the static state, yes, the bottom spokes undergo a
compression, but that compression is less than the tension already on
them, so they stay tensioned. Calling it compression instead of a
reduction of tension is six of one vs. a half dozen of the other.
Personally, I wouldn't say the bike stands on the bottom spokes as much
as it hangs from the top spokes. The rim supports the top spokes, and
the forward and trailing spokes hold the rim in shape. The bottom
spokes are just along for the ride. But mathematically, it's fine to
say it either way.
A free body diagram is handy for a structure you can hold in your
hands because you're not holding it in your hands when it's in use. In
its static state you can guesstimate about forces it'll experience, but
you don't just know without some calculations or experiments what
happens during a bump, high torque, or bending.
Anyway, the reason I always assumed for tensioning spokes has to do
with elasticity. Keep enough tension on them so that in the
loading/unloading cycle the experience as the wheel turns they never go
slack--they stretch enough to take up the movement. As the whole
structure moves around all parts remain in the same location relative to
each other and keep approximately the same loads they have when standing
still.
A similar application would be engine head bolts. They're
pre-tensioned (torqued to spec) to achieve a predetermined amount of
bolt stretch. That stretch more or less makes the bolts into springs
that can move a few hundred-thousandths when the engine fires. Without
the preload the bolts would move further and would repeatedly load and
unload, causing fatigue. It's impressive to watch a head bolt come
flying out of someone's hood.
Same with bicycle spokes--the springyness will hold all the parts in
place when the rim flexes, and keeping them loaded will prevent cyclical
unloading.
It happens with springs too--if you lighten a car enough without
lightening the suspension the springs can actually throw the car off the
tops of the springs, unloading them even if they're bolted in place with
clamps. Repeat that enough and the springs break far earlier than they
should even though the load on them is lighter.
--
B.B. --I am not a goat! thegoat4 at airmail.net
Weisse Luft
Wheels stand on the spokes, plain and simple. If you load a wheel, you
will note the bottom spoke is the only spoke which significantly changes
its tension. That its tension decreases is the sign it is actually
taking a compressive load even though in the properly tensioned wheel,
this spoke never becomes fully slack. This is the fundamental element
of a prestressed structure.
Since you are bent in a Pol-Pot style condemnation of technical terms,
why don't you try the plucking test?
--
Weisse Luft
Tom Sherman
> ...
> Since you are bent in a Pol-Pot style condemnation of technical terms,
> why don't you try the plucking test?
Would not Trofim Denisovich Lysenko be a better example than "Brother
No. 1"?
Trevor Jeffrey
??
Unless I know your assumptions, previous perception, I do not know how to
respond.
Do you think steel wire will take a tensile load more effectively if its
load is, say, doubled, in any way?
TJ
________
carl...@comcast.net wrote in message ...
Trevor Jeffrey
Weisse Luft wrote in message ...
>
>will note the bottom spoke is the only spoke which significantly changes
>its tension. That its tension decreases is the sign it is actually
>taking a compressive load even though in the properly tensioned wheel,
>this spoke never becomes fully slack. This is the fundamental element
>of a prestressed structure.
>
>Since you are bent in a Pol-Pot style condemnation of technical terms,
>why don't you try the plucking test?
I do not think the art of sophistry is conducive to understanding.
Spokes have no feet so cannot stand whether in a wheel or elsewhere.
A tensile spoked wheel does not mean a pre-tensioned wheel.
Tensile spoked means that the service load will be taken up by the spokes as
a tensile force. The spokes merely transfer the load between the hubshell
and the rim. The fact that spoke reduces in tension solely shows the
restraining elements have moved closer.
I'm satisfied with the amount of plucking I've done, thank you.
TJ
Trevor Jeffrey
Mark McMaster wrote in message <410EFF7B...@ix.netcom.com>...
>Trevor Jeffrey wrote:
>> Mark McMaster wrote in message <410DB583...@ix.netcom.com>...
>>
>>>Sorry, it doesn't work this way. Because the spokes are far
>>>stiffer than the rim, very little of the load is supported
>>>by the rim at all when the wheel is loaded - at least not
>>>until the spokes go slack. But then the wheel losses the
>>>lateral stability you seek, so asking the rim to support the
>>>load is a poor idea.
>>
>>
>> To what you are referring does not work I cannot make out. The
spokes
>> are tensile members so need to be resistive to stretch and the rim is a
>> compressive member so needs to be resistive to squash. One is the
complete
>> opposite of the other. The two are not comparable to each other.
Aluminium
>> is good in compression but not in tension, this is the way of the world,
>> aluminium rims and steel spokes. If the rim did not support the load it
>> would not need to be there. It either does or it does not, extraneous
items
>> are most usually omitted on a human powered vehicle. Rims are essential
>> part of the wheel and bear all the load. What else could possible
transmit
>> the force between tyre and spokes?
>
>As far as the role of the rim, it's main role is supply a
INCORRECT The rim provides the rolling surface and the tyre reduces rolling
resistace and provides grip to assist traction. I consider a tyre should
also reduce jarring.
>to have a
>sufficient compressive strength allow the spokes to be
>pre-tensioned,/
INCORRECT Spokes do not have to be pre-tensioned for a tensile spoked wheel
to function. The rim has to be able to withstand the compressive force
placed upon it in service. To enjoy lateral stability the nipples only
require winding to the point that no spoke comes loose(as in not in
contact ) from the rim or hub.
> and to have sufficient lateral strength to
>bear the alternating side to side forces of the spokes on
>each side of the wheel. /
Not a problem with wheels using the method I describe.
> For a wheel with a standard
>compliments of spokes, the rim is not required to have any
>strength to radial forces - it is the spokes, not the rim
>that supports the radial load. If the rim were constructed
>of many small hinged segments instead of being a continuous
>arch, the wheel would still be able to support its load.
I'm glad someone has appreciated the function of an arch. I prefer to say
that the spokes restrain the rim in its arch and the spokes transfer the rim
loading to the hub. Further detail is not pertinent to the understanding of
an effective wheel build.
>
>As I'm sure you'll agree, the compression on the rim is
>caused by the spoke tension (i.e., the spokes pull radially
>inward, attempting to circumferentially compress the rim). /
As I've pointed out above, the compressive load is caused by service and
that pre-loading the spokes is not required for a serviceable wheel. I
consider it is important not to take spoke tensioning further than that
which will result in a laterally stable wheel under reasonably expected
service conditions. Excessive tension in the spokes may cause the wheel to
self buckle with the slightest of knocks in service.
>If you had looked at the analyses of spoke tension changes
>when a wheel is loaded more carefully, you would see that
>the summation of the spoke tensions _decrease_ when a wheel
>is loaded. In other words, there are large spoke tension
>decreases directly at the bottom of the wheel, and only very
>small spoke tension increases elsewhere around the rim. The
>total sum of the spoke tension increases is far less than
>the sum of the spoke tension decreases. Although there may
>be some increases in rim compression around parts of the
>wheel due to the small spoke tension increases, they are
>very small.
This is complex, innaccurate and irrelevant. It is absurd that you wish to
persuade that the spokes change tension to move the rim, the force on a
loaded wheel is generally in directions so as to bring together rim and hub
in the lower portion of the wheel. To suggest that the spokes act to move
the rim is incongruous of an inanimate object. The point is stated above,
the spokes transfer the load from the rim to the hub. I know not of which
analysis you seem to think I have looked at. If it suggests that which you
have indicated, it is worthless.
>
>If you are really concerned about rim compressive strength,
>you should focus on braking forces - the only loading mode
>that can add any substantial compression on the rim. /
If you look again, you may find.
>This
>is because this loading mode can apply a high load
>tangential to the rim./
You do not understand arches do you? Please ignore previous statement and
ammend to " I see you've heard of arches." All serviceable loads directed
through a wheel through the plane of that wheel will be restrained by the
rim. This is because the rim acts as an arch and changes the direction of
load through 90deg to travel along that arch.
> Radial loads mostly apply the load
>to the rim in bending - and since the spokes are so stiff,
>as long as they remain in tension, the bending of the rim
>will be minimized./
Adequately restrained arches do not bend significantly. The preforming of
the spoke at the crossing point, makes the rim adequetly restrained, without
the risk of self destructive forces otherwise encountered due to
overtensioning of spokes during construction. Spoke tension is kept to the
minimum required to maintain lateral stability under reasonably expected
service conditions.
>
>But you are an expert on wheels, so you knew all this.
>
I now have a better understanding of your lack of knowledge.
TJ
Benjamin Weiner
> [Jobst Brandt wrote in a 1998 exchange now on yarchive.net]
> >As you see, I found more than you. With help I located Karl
> >Wiedemer's publication on the subject. Prof. Wiedemer, now
> >retired, did his analysis at the same time I did and he also had
> >no references because it was new work in a field that had progressed
> >without analysis for a long time. Prof. Pippard in England wrote
> >extensively on the subject but never discovered the mode of
> >wheel loading and deflections that I and Wiedemer presented.
> >As I said, I made the analysis by measurement and was rejected
> >by professors of engineering. When I presented the finite element
> >analysis, these same people chose to change the subject and get
> >back to "serious" work.
> Googling for "karl wiedemer" produces four other pages, all
> in German, one on safety devices for coal dust, one on blast
> furnace slag, one on the history of some club from 1896, and
> two other in pdf format that Google does not offer to
> translate.
>
> Spoke-squeezing is an intriguingly mysterious subject to
> research. I remain agnostic, wavering one way and the other,
> but haven't seen any experimental data or analyses involving
> bicycle spokes. If you have the 3rd edition, perhaps you
> could peek at the Wiedemer stuff and give me your thoughts
> on it?
The reference to Karl Wiedemer's article is in the Bibliography after
the tables of equations used. It is:
Wiedemer, K. "Kraftverteilung am Speichenrad", Konstruktion, Vol. 2,
pp. 64-66, 1962.
This probably translates as "Strength of a spoked wheel" or "Stress
distribution in a spoked wheel" or something close to that. From what
Jobst says above, I expect that it is an analysis of the deflections of
rim and spokes, along the lines of what Jobst did later with finite
element analysis. It might be relevant to the "hub stands on the
prestressed spokes" argument but I doubt it says anything about stress
relieving of spokes.
The yarchive.net interchange where someone flames Jobst because his book
isn't peer-reviewed is a complete red herring. His book is a monograph,
a detailed treatment of a subject which doesn't slot neatly into a scientific
journal's predefined niche. There's a long and honorable tradition of
these in scientific and technical publishing.
Weisse Luft
Tom, that would be a more accurate example, if not more arcane.
I once had the same error of thought, that the hub was indeed supported
by an increase in tension of the top spokes. This would be true if the
rim were infinitely rigid or was uniformly constrained. This is not
the case in any wheel, even ones with steel rims.
My road to Damascus came from formal training in mechanical
engineering, specifically a course on strength of materials...another
Russian but with the name Timenshenko. This Russian was however, well
grounded in science, peer review and to this day is highly regarded.
And yes, the spoked wheel was one topic on pre-stressed structures.
Now before you go off and label me as a Brandt "boot-licker" or worse,
let me state I have never met the man nor do I agree with everything he
says. But when he talks of the basic concepts, I find general
agreement.
--
Weisse Luft
Tom Sherman
> Tom Sherman Wrote:
>
>>Weisse Luft wrote:
>>
>>
>>>...
>>>Since you are bent in a Pol-Pot style condemnation of technical
>>
>>terms,
>>
>>>why don't you try the plucking test?
>>
>>Would not Trofim Denisovich Lysenko be a better example than "Brother
>>No. 1"?
>>
>>--
>
>
> Tom, that would be a more accurate example, if not more arcane.
>
> I once had the same error of thought, that the hub was indeed supported
> by an increase in tension of the top spokes. This would be true if the
> rim were infinitely rigid or was uniformly constrained. This is not
> the case in any wheel, even ones with steel rims.
>
> My road to Damascus came from formal training in mechanical
> engineering, specifically a course on strength of materials...another
> Russian but with the name Timenshenko. This Russian was however, well
> grounded in science, peer review and to this day is highly regarded.
I have a copy of "Mechanics of Materials" by Gere and Timenshenko packed
away somewhere.
Trevor Jeffrey
B.B. wrote in message ...
>
> Relative to the static state, yes, the bottom spokes undergo a
>compression, but that compression is less than the tension already on
so they do not undergo a compression. Obvious, they are still in tension.
> Calling it compression instead of a
>reduction of tension is six of one vs. a half dozen of the other.
No, it is either lying or stupidity. The two are opposites. An either or
state.
If you owe me ten pounds sterling, I want ten pounds sterling, not a not not
ten pounds sterling or any U.S. currency below 30 dollars for that matter.
>Personally, I wouldn't say the bike stands on the bottom spokes as much
>as it hangs from the top spokes. /
Don't do it!
> The rim supports the top spokes, /
Nah, they hang from the rim.
>and
>the forward and trailing spokes hold the rim in shape./
it will hold its own shape without external influence. Do not try and
entertain me by using forward and trailing, I will not fall for it.
> The bottom
>spokes are just along for the ride. /
Wouldn't we all like to be?
> But mathematically, it's fine to
>say it either way.
1+2=3 2+1=3 3-1=2 3-2=1 What's math's got to do , got to do with
it.
What's math's but I reckon a distraction?
> A free body diagram is handy for a structure you can hold in your
>hands because you're not holding it in your hands when it's in use. In
>its static state you can guesstimate about forces it'll experience, but
>you don't just know without some calculations or experiments what
>happens during a bump, high torque, or bending.
Presently no feasably economic way of measuring all stresses desired.
I can see no reason to get further from the truth by using diagrams, unless
one wishes to avoid the obvious. As I have said, it matters not which way
the wheel loading is taken through the spokes, as long as it is done
succesfully.
>anyway, the reason I always assumed for tensioning spokes has to do
>with elasticity. Keep enough tension on them so that in the
>loading/unloading cycle the experience as the wheel turns they never go
>slack--they stretch enough to take up the movement. /
If you think your spokes are acting as springs, there's your problem. You
should think of them as stays, and make them act as such, by preforming
them.
Then you will end up with a solid wheel, and not the usual wibbly wobbly
mess that may or may not ollapse when braking, climbing or sprinting. Oh
yes those other wheels dongt like corners either.
> As the whole
>structure moves around all parts remain in the same location relative to
>each other and keep approximately the same loads they have when standing
>still.
Nah, that is not possible. Please attempt to use punctuation for clarity.
> A similar application would be engine head bolts.
Cylinder head bolts are nowt in comparison.
> They're
>pre-tensioned (torqued to spec) to achieve a predetermined amount of
>bolt stretch. /
They are tensioned to resist the cylinder pressure from lifting the head and
so allowing leakage, usually into the water jacxket.
> That stretch more or less makes the bolts into springs
>that can move a few hundred-thousandths when the engine fires./
If the head lifted a few hundred thou, leakage into the water jacket would
be certain.
> Without
>the preload the bolts would move further and would repeatedly load and
>unload, causing fatigue.
Am I suppposed to think you understand fracture mechanics after the
statements you made above?
> It's impressive to watch a head bolt come
>flying out of someone's hood.
It's a bloody fool that wants to be there. Don't you have workshops that
understand specced hi-ten studs and bolts?
> Same with bicycle spokes--the springyness will hold all the parts in
>place when the rim flexes, and keeping them loaded will prevent cyclical
>unloading.
"the forward and trailing spokes hold the rim in shape." you meant
constrained before, now its "springyness" but the rim dose not move, and it
flexes.
TYhere is no way on earth that you can prevent cyclic variation of load in
any wheel. Try and form your argument before you write it please.
> It happens with springs too--if you lighten a car enough without
>lightening the suspension the springs can actually throw the car off the
>tops of the springs, unloading them even if they're bolted in place with
>clamps.
Whatever springs your jabbering on about, I expect leaf, they failed because
of poor manufacture. It's Ford in the UK that have had this sort of
reputation, who vastly improved betwen 10 to 15 years back. Along with
their previously appaling brakes.
> Repeat that enough and the springs break far earlier than they
>should even though the load on them is lighter./
>
Reapeat it enough and you may convince youself, I, being sane do not feel
the need to make comparisons that bear no relation.
TJ
I'll say it again, be certain of your argument before writing.
Trevor Jeffrey
Jeff Napier wrote in message ...
>You'll find a reasonable tutorial on the basics of wheel alignment and
>wheelbuilding at www.bikewebsite.com
>Have fun!
>- Jeff -
>
>
GRRRRRRRRRRR
Mark McMaster
> Mark McMaster wrote in message <410EFF7B...@ix.netcom.com>...
>>As far as the role of the rim, it's main role is supply a
>>continuously round surface to mount the tire, /
>
>
> INCORRECT The rim provides the rolling surface and the tyre reduces rolling
> resistace and provides grip to assist traction. I consider a tyre should
> also reduce jarring.
How can you say that the rim provides the rolling surface,
if the wheel doesn't roll on the surface of the rim? Also,
you are entirely incorrect about the tire reducing rolling
resistance - it increases the rolling resistance, not
decreases it. If tires decreased rolling resistance,
railroad cars would roll on pneumatic tires instead of
directly on their solid wheels. Now that you've been wrong
twice about bicycle tires (they don't hydroplane and they
don't decreasing rolling resistance over a solid wheel),
let's see what else you can be wrong about.
>>to have a
>>sufficient compressive strength allow the spokes to be
>>pre-tensioned,/
>
>
> INCORRECT Spokes do not have to be pre-tensioned for a tensile spoked wheel
> to function. The rim has to be able to withstand the compressive force
> placed upon it in service. To enjoy lateral stability the nipples only
> require winding to the point that no spoke comes loose(as in not in
> contact ) from the rim or hub.
This statement is wrong in the general case, and for the
practical case also. Theoretically, if a rim were
sufficiently stiff in bending, it could carry a substantial
portion of the load to the top of the wheel. However, rims
actually stiff enough to do this are few and far between.
Typical rims (such Mavic's Open Pro or MA3) are not nearly
stiff enough. So in the practical sense for the vast
majority of wheels in service, you are wrong.
>>For a wheel with a standard
>>compliments of spokes, the rim is not required to have any
>>strength to radial forces - it is the spokes, not the rim
>>that supports the radial load. If the rim were constructed
>>of many small hinged segments instead of being a continuous
>>arch, the wheel would still be able to support its load.
>
>
> I'm glad someone has appreciated the function of an arch. I prefer to say
> that the spokes restrain the rim in its arch and the spokes transfer the rim
> loading to the hub. Further detail is not pertinent to the understanding of
> an effective wheel build.
If you believe this, then you are being willfully ignorant.
The rim in a bicycle wheel does not behave like a classic
arch (more on this below)
>>If you had looked at the analyses of spoke tension changes
>>when a wheel is loaded more carefully, you would see that
>>the summation of the spoke tensions _decrease_ when a wheel
>>is loaded. In other words, there are large spoke tension
>>decreases directly at the bottom of the wheel, and only very
>>small spoke tension increases elsewhere around the rim. The
>>total sum of the spoke tension increases is far less than
>>the sum of the spoke tension decreases. Although there may
>>be some increases in rim compression around parts of the
>>wheel due to the small spoke tension increases, they are
>>very small.
>
>
> This is complex, innaccurate and irrelevant. It is absurd that you wish to
> persuade that the spokes change tension to move the rim, the force on a
> loaded wheel is generally in directions so as to bring together rim and hub
> in the lower portion of the wheel. To suggest that the spokes act to move
> the rim is incongruous of an inanimate object. The point is stated above,
> the spokes transfer the load from the rim to the hub. I know not of which
> analysis you seem to think I have looked at. If it suggests that which you
> have indicated, it is worthless.
It appears that you are suffering from cognitive dissonance.
During discussions on wheel mechanics, you become agitated
whenever the actual measured tension changes in a loaded
wheel is pointed, because they don't jibe with your
particular views. For any theory to be correct it has to
correspond with known facts. If the facts and the theory
are mutually exclusive, it is the theory that is incorrect,
not the facts. This is the case with your "wheel loads are
carried by compression of the rim" theory.
The changes in spoke tension in a loaded wheel have been
analyzed and measured several times. They always lead to
the same conclusions about how loads are distributed through
out the wheel components. In case you need reminding (and
it appears you do) of the spoke tension changes, here are a
few links to some finite element analyses and direct
measurements:
http://www.achrn.demon.co.uk/astounding/ian/wheel/
http://www.rose-hulman.edu/~fine/FE2002/Projects/Hartz.pdf
http://www.duke.edu/~hpgavin/papers/HPGavin-Wheel-Paper.pdf
http://groups.google.com/groups?q=spoke++.0002++hoyt+mcmaster&hl=en&lr=&ie=UTF-8&c2coff=1&selm=34AE9E7E.3593%40usit.net&rnum=3
There are also other published tests and analyses not on the
web.
>>This
>>is because this loading mode can apply a high load
>>tangential to the rim./
>
>
> You do not understand arches do you? Please ignore previous statement and
> ammend to " I see you've heard of arches." All serviceable loads directed
> through a wheel through the plane of that wheel will be restrained by the
> rim. This is because the rim acts as an arch and changes the direction of
> load through 90deg to travel along that arch.
You may have heard of arches, but I don't think you
understand how they work. It can be demonstrated that a
bicycle rim does not support loads like a classic arch does.
In a classic arch, a load applied in the middle of the
span is transferred to the ends of the arch through
compression of the arch. For example, if a 100 lb. downward
force is applied exactly at the middle of the arch, the arch
will transfer 50 lb. of the downward force to one end of the
arch, and 50 lb. of the downward force to the other end.
For a bicycle rim this does not happen. You say that the
bottom half of the rim (180 degrees) acts like an arch and
carries loads by compression 90 degrees up around the
periphery of the rim to the front and back of the wheel. If
this were so, then the loads would have to then be
transferred (by compression) to the top 180 degree arch of
rim. But if that were the case, in order to support this
load on the top arch of the rim, you would see corresponding
increases in tension in the spokes at the top of the wheel,
supporting the arch. However, all the analyses and
measurements have shown that the small spoke tension
increases that do occur at the top aren't nearly enough to
support the load. Looking at the analysis in the first web
site cited above, out of the 1000 N load applied at the
bottom of the wheel, The vertical components of all the top
spokes combined are only 100 N (10%). Where is the rest of
the load being supported? Look at the bottom of the wheel,
and you can see tension decreases account for about 950 N
(95%) of the load. (Further, you'll see that there are
spoke tension increases below rim, of about 5% of the total
load). The only conclusion that can be reached is that the
rim does not act like a classic arch, and only transfer a
small portion of the external load to the top of the wheel.
So, your theory that a load on the wheel increases
compression on the rim is clearly inconsistent with the
actual data. If there is little increase in the tension in
the top spokes, there can be little increase in compression
in the top half of the rim, which means that there is little
rim compression transferred from the bottom half of the
rim. Therefore, the load on a wheel is not transferred
from the ground to the hub primarily by rim compression.
The magnitudes of the spoke tension changes have been
measured and calculated by many independent parties, who
have all discovered the same patterns of load distribution.
You can not simply dismiss the data, just because it
doesn't match your ideas. If your theory can not account
for the load distribution, your theory is wrong. Even if
you do manage to concoct a some convoluted explanation to
make your theory fit, that still doesn't make it correct.
Occam's razor says that the simplest theory is the best -
the theory that the external load is carried by the
decreases in tension of a pre-tensioned wheel is simple,
direct, and matches all the known data.
> Adequately restrained arches do not bend significantly. The preforming of
> the spoke at the crossing point, makes the rim adequetly restrained, without
> the risk of self destructive forces otherwise encountered due to
> overtensioning of spokes during construction. Spoke tension is kept to the
> minimum required to maintain lateral stability under reasonably expected
> service conditions.
>
>
>>But you are an expert on wheels, so you knew all this.
>>
>
>
> I now have a better understanding of your lack of knowledge.
No, but we all have a better understanding of how creative
you can be in ignoring independently verified data that
don't match your beliefs. I guess I'll have to withdraw the
statement about you being an expert on wheels.
Mark McMaster
MMc...@ix.netcom.com
B.B.
"Trevor Jeffrey" <Trevor_...@beeeb.net> wrote:
>B.B. wrote in message ...
>>
>> Relative to the static state, yes, the bottom spokes undergo a
>>compression, but that compression is less than the tension already on
>>them, so they stay tensioned./
>
>so they do not undergo a compression. Obvious, they are still in tension.
You can have both tension forces and compression forces working on
the same object. If you have more tension, the whole object is said to
be "in tension" but the compressive force still exists.
>> Calling it compression instead of a
>>reduction of tension is six of one vs. a half dozen of the other.
>
>No, it is either lying or stupidity. The two are opposites. An either or
>state.
No, if you do the math, compression is negative tension, tension is
negative compression. Negative 4 plus positive five nets you positive
one. If the two concepts were really unrelated you'd be unable to add
or subtract them.
>If you owe me ten pounds sterling, I want ten pounds sterling, not a not not
>ten pounds sterling or any U.S. currency below 30 dollars for that matter.
If you want to talk money, fine. Deposit $100 in the bank, write a
check for $80, how much have you got left? But deposits and withdrawals
are opposites!
>>Personally, I wouldn't say the bike stands on the bottom spokes as much
>>as it hangs from the top spokes. /
>
>Don't do it!
>
>> The rim supports the top spokes, /
>
>Nah, they hang from the rim.
>
>>and
>>the forward and trailing spokes hold the rim in shape./
>
>it will hold its own shape without external influence. Do not try and
>entertain me by using forward and trailing, I will not fall for it.
Unfortunately, the rim often has external influences called
"bicycles" so we need to add a few spokes to hold stuff in place.
>> The bottom
>>spokes are just along for the ride. /
>
>Wouldn't we all like to be?
>
>> But mathematically, it's fine to
>>say it either way.
>
>1+2=3 2+1=3 3-1=2 3-2=1 What's math's got to do , got to do with
>it.
>What's math's but I reckon a distraction?
>
>> A free body diagram is handy for a structure you can hold in your
>>hands because you're not holding it in your hands when it's in use. In
>>its static state you can guesstimate about forces it'll experience, but
>>you don't just know without some calculations or experiments what
>>happens during a bump, high torque, or bending.
>
>Presently no feasably economic way of measuring all stresses desired.
>I can see no reason to get further from the truth by using diagrams, unless
>one wishes to avoid the obvious. As I have said, it matters not which way
>the wheel loading is taken through the spokes, as long as it is done
>succesfully.
That I'll agree with. However, if you want to determine life
expectancy of the materials involved without using a whole lot of
destructive testing you'll need diagrams and evil, confusing math!
But if you don't care about that--fine, put 'em together in whatever
way works for you.
>>anyway, the reason I always assumed for tensioning spokes has to do
>>with elasticity. Keep enough tension on them so that in the
>>loading/unloading cycle the experience as the wheel turns they never go
>>slack--they stretch enough to take up the movement. /
>
>If you think your spokes are acting as springs, there's your problem. You
>should think of them as stays, and make them act as such, by preforming
>them.
>Then you will end up with a solid wheel, and not the usual wibbly wobbly
>mess that may or may not ollapse when braking, climbing or sprinting. Oh
>yes those other wheels dongt like corners either.
Your wheels still flex. All structures flex, so the good ones get
designed to tolerate it. Things that can't tolerate the normal flexing
they experience will fail quickly. In a structure that flexes, the
flexing parts act as springs, so you calculate with them accordingly.
>> As the whole
>>structure moves around all parts remain in the same location relative to
>>each other and keep approximately the same loads they have when standing
>>still.
>
>Nah, that is not possible. Please attempt to use punctuation for clarity.
Bite me. If what I said isn't possible, how can you bend your arm at
the elbow without tearing your flesh apart? Answer: because it flexes!
Metals do the same thing, just to a much smaller degree. In a correctly
adjusted bike wheel there will be a small amount of flex. By small I
mean smaller than you can see visually, so this flexing won't leave you
with a floppy wheel. And the parts won't be moving around relative to
each other--they'll just all "give" a bit here and there.
>> A similar application would be engine head bolts.
>
>Cylinder head bolts are nowt in comparison.
It's steel in tension, isn't it?
>> They're
>>pre-tensioned (torqued to spec) to achieve a predetermined amount of
>>bolt stretch. /
>
>They are tensioned to resist the cylinder pressure from lifting the head and
>so allowing leakage, usually into the water jacxket.
The head does lift by a few hundred thousandths. That's why the head
gasket is there--to take up the difference. There are a few engines out
there without head gaskets, but they simply use other means to take up
that slack.
FYI, compression leaks out of the head gasket usually come out the
side of the block at the gasket seam, or spill over into an adjoining
cylinder. It's pretty rare to leak into the water passages. Also note
I said "passages" as the actual water jacket stops below the head gasket.
>> That stretch more or less makes the bolts into springs
>>that can move a few hundred-thousandths when the engine fires./
>
>If the head lifted a few hundred thou, leakage into the water jacket would
>be certain.
You're incorrect.
>> Without
>>the preload the bolts would move further and would repeatedly load and
>>unload, causing fatigue.
>
>Am I suppposed to think you understand fracture mechanics after the
>statements you made above?
Yup.
>> It's impressive to watch a head bolt come
>>flying out of someone's hood.
>
>It's a bloody fool that wants to be there. Don't you have workshops that
>understand specced hi-ten studs and bolts?
No, I live on the moon.
>> Same with bicycle spokes--the springyness will hold all the parts in
>>place when the rim flexes, and keeping them loaded will prevent cyclical
>>unloading.
>
>"the forward and trailing spokes hold the rim in shape." you meant
>constrained before, now its "springyness" but the rim dose not move, and it
>flexes.
>TYhere is no way on earth that you can prevent cyclic variation of load in
>any wheel. Try and form your argument before you write it please.
There can be variation, but as long as it doesn't completely unload
or completely overload it can handle many cycles. A minimum tension
limit is important to keep the parts from unloading, a maximum tension
limit is important to keep parts from overloading.
>> It happens with springs too--if you lighten a car enough without
>>lightening the suspension the springs can actually throw the car off the
>>tops of the springs, unloading them even if they're bolted in place with
>>clamps.
>
>Whatever springs your jabbering on about, I expect leaf, they failed because
>of poor manufacture. It's Ford in the UK that have had this sort of
>reputation, who vastly improved betwen 10 to 15 years back. Along with
>their previously appaling brakes.
Coil. And not just Fords; it happens in all suspended vehicles if
you unload them enough--regardless of spring manufacturer. Leaf springs
would break pretty often due to cyclic unloading due to design, but
they're overbuilt enough to handle it most of the time. If weight
weren't an issue you could use really fat, untensioned spokes that never
break, but bicycle riders for whatever reason seem to like lighter
bikes, so materials are pushed a little further towards their mechanical
limits.
>> Repeat that enough and the springs break far earlier than they
>>should even though the load on them is lighter./
>>
>
>Reapeat it enough and you may convince youself, I, being sane do not feel
>the need to make comparisons that bear no relation.
You protest too much. You also omitted a comma slightly after the
middle of your run-on sentence. Please use punctuation correctly--for
clarity.
>TJ
>
>I'll say it again, be certain of your argument before writing.
That's funny.
Weisse Luft
I think I will write TJ a check for a NEGATIVE 10 pounds Sterling and
see if he tries to deposit it ;)
Spokes do behave like springs with the spring rate proportional to the
cross sectional area and inversly proportional to the length. This is
why 14/17 gauge spokes make a wheel that is more difficult to true but
also make for a more durable wheel since the variation in spoke load is
of less magnitude.
--
Weisse Luft
Jose Rizal
> If you EVER get compression in a strand of wire rope (cable is for
> television),
Cable was used as a term for "wire rope" long before fibre optic cable
came into common use. Wire rope is not commonly used as a term, but if
it makes you feel better....
> I want to be far away because something BAD is going to
> happen. Wire rope unwinds when you put it in compression.
Not if the strands' movement is constrained, as in _wound_ strands
around a pulley.
> Wire rope
> has a lower elastic modulus than say a spoke.
And your point is?
> Someone needs to read up
> on Roebling et al.
Someone needs to study basic physics. Better yet, just look at a wire
cable and bend it.
> Its unlikely that failure of a single strand in a wire rope will cause
> any failure given the lower elastic modulus of wire rope. Yes, you can
> make it fail but the analogy here is not accurate.
Rubbish. You ignore the fact that loss of a strand (or strands)
decreases the cross-sectional area of the cable. As I've stated several
times before, if the load is high enough such that strands start
breaking, failure will be inevitable since the load will be taken up by
less strands. I fail to see what is hard to understand about this.
> And yes, an airplanes skin IS an IMPORTANT part of the total structure.
> I learned this back when I was a kid building model sailplanes.
Excellent, that sure replaces years of University education on airplane
design.
> The
> structure is WEAK until the covering (silkspan, fabric or any of the
> shrinkable Mylar films) is applied, shrunk and painted. When the wing
> is positively loaded, the tension in the top is partially relieved
> while that on the bottom surface increases. For ultra high performance
> aircraft, the first third or so of the wing is sheeted in balsa, obeechi
> or light ply because no covering is strong enough for the compression.
> Enough aircraft, I forgot more than you know now.
Great, why don't you go work for Boeing, I'm sure they'll be blown away
by your novel "findings". Read up on basic airplane design before you
make silly pronouncements like the above "sailplane" analogy.
Airplane skins do not take up any significant in-plane loads. The
aerodynamic loads normal to the skin are transmitted to the frame, which
are the critical load structures that are subject to much fatigue
analysis and modelling. All the skin needs to do is stay on the frame
to provide an aerodynamic structure and to transmit the aerodynamic
loads to the frame. With high-flexing structures such as lengthy wings,
the skin only needs to withstand the amount of flex the wings undergo;
these are much less than the aerodynamic loads that the frame must
withstand.
> Wire ropes are ALWAYS wound with tension to ensure the inner strands do
> not go into compression. Since the wire is helical, the stresses are
> normalized
"Normalized"? I suspect you don't know what this term means.
> except for the CORE which is usually INDEPENDENT as in
> Independent Wire Rope Core (IWRC).
And so? Bending an "IWRC" core, or any structure for that matter, will
always involve compressing one side (the concave side), unless you are
suggesting that the core is tensioned so highly that bending it will
never unload the concave part of the bend (an impossible situation).
Jose Rizal
> One spoke without pre-tensioning is more than adequate to support my static
> weight
This does not make any sense at all. How do you pre-tension a spoke?
You either tension it or you don't. A slack spoke will not take up your
static weight.
> Dynamic loads
> If the wheel is built to cope with a load of 7/5(rider + bike + luggage)
> this will be found to be adequate on a road bike. The capability of the
> wheel is simply tested with a weight equivalent to the calculated maximum
> force. The calculation is based on maximum wheel load attained on a front
> wheel during braking assuming a co-efficient of friction of almost 1 on a
> flat road(use of trigonometry). Maximum braking in a bend with positive
> banking may see this force may exceeded. I do not know whether the same
> test figure could be used for a track sprinter, but expect it to be not far
> off.
I'd like to see your calculations on this, since your figures look
dubious. Even if your assumption is correct, you have not taken into
account any loads on the wheel due to bumps and drops, which can exceed
your static weight and braking forces.
> Tensioning a wheel with pre-formed spokes.
***** snip rain dance methodology ******
> The likelihood of a wheel buckling that will lock up in the frame is
> greatly reduced with my preferred method of building a wheel, as the
> technique results in a wheel with a greater lateral stability and the lower
> compression levels in the rim allow a greater overhead available for dynamic
> load due to impact.
You hope. You haven't shown any quantitative reasoning for your
beliefs, instead relying on optimism based on faulty assumptions.
carl...@comcast.net
Dear Weisse,
If you have a few moments, could you see if I'm following
you on this thinner spoke business?
I'm familiar with the idea that double-butted spokes with
thinner middle sections are paradoxically more durable than
straight spokes of the same thickness .
My half-remembered explanation is something along the lines
of how thinner spokes can stretch farther elastically and
therefore aren't as likely to lose all tension (a bad thing,
I gather) as straight spokes of the same thickness.
But you're saying that the variation of the spoke load is
less. Is this a matter of both thick and thin spokes being
tensioned to X pounds and the thick one going to 0 pounds
of tension, a variation of X, while the more elastic thinner
spoke doesn't drop as far--say to 10 lbs tension--and
therefore has a smaller load range of X -10 instead of the
full range of X.
Presumably spokes last longer with this smaller load
variation. I'm hoping that I've managed to figure out what
you (and others) already understood, since it seems clearer
than waving my hands and declaring that losing all tension
is a bad thing.
Thanks,
Carl Fogel
Weisse Luft
http://www.nps.navy.mil/avsafety/gouge/stress.htm
>
> An example of this is the G-loading an airplane structure experiences
> during maneuvering. During an abrupt pull-up, the airplane's wing
> spars, wing skin and fuselage undergo positive loading and the upper
> surfaces are subject to compression, while the lower wing skin
> experiences tension load...
And I do know what "normalized" means in statistics, stress and
materials science.
--
Weisse Luft
Weisse Luft
You are going great in understanding of the spoked wheel. The rim
deforms (elastically) under the loading which partially unloads the
bottom spoke. Since this deformation is relatively irrespective of
spoke diameter and is mostly due to the strength of the rim, it stands
that a more elastic spoke will lose less of its pretension under the
same deformation.
This concept dictates why stiff rim sections can be supported by fewer
spokes and why more flexible rim sections are better suited to using
more elastic spokes.
Since elasticity is the length of the spoke divided by the product of
the cross sectional area and the modulus of elasticity, one can see
that titanium spokes in 14 gauge are equivalent to DT Revolutions in
14/17, length being equal. Amazingly enough, the weight is about the
same.
Keeping spokes under tension is one key to durability. Stress reversal
is a bane to cyclic life which is why all automobile valve springs are
kept in tension. And Valve springs that float or go into harmonic
unloading will fail at very low cycle life.
--
Weisse Luft
Tom Sherman
You mean that Hooke and Young were right? ;)
Weisse Luft
Right? They are BRILLIANT :D I am continually amazed of the average
engineering graduate who has troubles with stress, strain and
deformation when a complex problem is presented. One has to look at
the effects of displacement and load. Consider a pipe subjected to a
pressure load and a thermal expansion. The stress resulting from the
pressure is constant, not reduced by diplacement. The stress resulting
from thermal effects is relieved by small displacements. If one takes
the system as being infinitely ridgid, the yield point is exceeded.
But in reality, the tiny displacements relieve the thermal stress,
allowing the pipe to adequately restrain the axial stress along with
primary hoop stress.
--
Weisse Luft
Trevor Jeffrey
Jose Rizal <_@_._> wrote in message ...
>Trevor Jeffrey:
>
>> One spoke without pre-tensioning is more than adequate to support my
static
>> weight
>
>This does not make any sense at all. How do you pre-tension a spoke?
>You either tension it or you don't. A slack spoke will not take up your
>static weight.
The point I am making is that it is possible to operate a tensile spoked
wheel with slack spokes and that tensioning spokes during build does not
contribute significantly to the operation of that wheel. The spoke will
tension when it bears my weight.
>
>> Dynamic loads
>> If the wheel is built to cope with a load of 7/5(rider + bike +
luggage)
>> this will be found to be adequate on a road bike. The capability of the
>> wheel is simply tested with a weight equivalent to the calculated maximum
>> force. The calculation is based on maximum wheel load attained on a front
>> wheel during braking assuming a co-efficient of friction of almost 1 on a
>> flat road(use of trigonometry). Maximum braking in a bend with positive
>> banking may see this force may exceeded. I do not know whether the same
>> test figure could be used for a track sprinter, but expect it to be not
far
>> off.
>
>I'd like to see your calculations on this, since your figures look
>dubious. Even if your assumption is correct, you have not taken into
>account any loads on the wheel due to bumps and drops, which can exceed
>your static weight and braking forces.
Using Pythagarus' theorum on the length of the hypotemuse sqr/ 1*1 +
1*1=1.41 or a little over 7/5
Most bumps are minor and short term, and so with an adequate tyre will be
absorbed by the tyre. Exceptions do occur such as speed humps on a
downhill, this will shake loose nipples that have not been oiled, hence the
requirement for linseed or the like.
Experience shows the lack of calculation due to severe road shock, does not
limit the wheel in any way. The worry may otherwise unnecesarily limit your
performance.
>
>> Tensioning a wheel with pre-formed spokes.
>***** snip rain dance methodology ******
>
>> The likelihood of a wheel buckling that will lock up in the frame is
>> greatly reduced with my preferred method of building a wheel, as the
>> technique results in a wheel with a greater lateral stability and the
lower
>> compression levels in the rim allow a greater overhead available for
dynamic
>> load due to impact.
>
>You hope. You haven't shown any quantitative reasoning for your
>beliefs, instead relying on optimism based on faulty assumptions.
>
>
OK 5732094528492637850937245 times out of 5732094528492637850937246 my
method will result in better wheels than any alternative method I know of or
suspect. Duly quantified. Is it vaguely possible you could understandably
explain in simple language, a method you know to be superior?
TJ
Trevor Jeffrey
Mark McMaster wrote in message <41121C05...@ix.netcom.com>...
>Trevor Jeffrey wrote:
>> Mark McMaster wrote in message <410EFF7B...@ix.netcom.com>...
>>>As far as the role of the rim, it's main role is supply a
>>>continuously round surface to mount the tire, /
>>
>>
>> INCORRECT The rim provides the rolling surface and the tyre reduces
rolling
>> resistace and provides grip to assist traction. I consider a tyre should
>> also reduce jarring.
>
>How can you say that the rim provides the rolling surface,
I assure you it can. I have ridden a bare rim after tearing a tyre cased by
wheel collapse (constructed as instructed in JB's book) during sprinting.
It was the poor stability of this wheel made me want to investigate further
on constructional techniques.
>Also,
>you are entirely incorrect about the tire reducing rolling
>resistance - it increases the rolling resistance, not
>decreases it. /
Robert Thompson and John Dunlop etc would disagree.
> If tires decreased rolling resistance,
>railroad cars would roll on pneumatic tires instead of
>directly on their solid wheels./
Oh no they wouldn't. Oh yes they do. But where? I cannot recall.
The railway carriage was in existence long before the invention of the
pneumatic tyre. Wheels are large and the track is smooth and resilient.
Notice the use of the word track, a carriage wheel has to track the line
accurately at high speed under braking and acceleration in straight lines
and around curves. This is acheived through special shaping of the wheel's
tyre and the track. The track is cambered. Railway locomotives are heavy,
the complications to use pneumatic tyres resilient enough for this
application are great. It would be impossible to convert to a pnuematic
tyred rail system.
> Now that you've been wrong
>twice about bicycle tires (they don't hydroplane and they
>don't decreasing rolling resistance over a solid wheel),
>let's see what else you can be wrong about.
>
>
>>>to have a
>>>sufficient compressive strength allow the spokes to be
>>>pre-tensioned,/
>>
>>
>> INCORRECT Spokes do not have to be pre-tensioned for a tensile spoked
wheel
>> to function. The rim has to be able to withstand the compressive force
>> placed upon it in service. To enjoy lateral stability the nipples only
>> require winding to the point that no spoke comes loose(as in not in
>> contact ) from the rim or hub.
I unfortunately ommited to say during service when referring to nipple
position. Ambiguity removed.
>
>This statement is wrong in the general case, and for the
>practical case also. Theoretically, if a rim were
>sufficiently stiff in bending, it could carry a substantial
>portion of the load to the top of the wheel. However, rims
>actually stiff enough to do this are few and far between.
>Typical rims (such Mavic's Open Pro or MA3) are not nearly
>stiff enough. So in the practical sense for the vast
>majority of wheels in service, you are wrong.
>
Constraint by the spokes forward and behind the contact area provide the
necesary resistance, along with the method of arch support, to bending of
the rim due to radial loads. The rim is not required to take the load
without spokes. Your statements are superfluous.
>
>>>For a wheel with a standard
>>>compliments of spokes, the rim is not required to have any
>>>strength to radial forces - it is the spokes, not the rim
>>>that supports the radial load. If the rim were constructed
>>>of many small hinged segments instead of being a continuous
>>>arch, the wheel would still be able to support its load.
>>
>>
>> I'm glad someone has appreciated the function of an arch. I prefer to
say
>> that the spokes restrain the rim in its arch and the spokes transfer the
rim
>> loading to the hub. Further detail is not pertinent to the understanding
of
>> an effective wheel build.
>
>If you believe this, then you are being willfully ignorant.
> The rim in a bicycle wheel does not behave like a classic
>arch (more on this below)
Why are bringing in classic arches? A misdirection. My argument still
stands without further comment or explanation.
> During discussions on wheel mechanics, you become agitated /
I really don't. Don't make false accusations.
>whenever the actual measured tension changes in a loaded
>wheel is pointed, because they don't jibe with your
>particular views.
It is still uneccasary and irrelevant, you only bring it up to cause
diversion.
> For any theory to be correct it has to
>correspond with known facts. If the facts and the theory
>are mutually exclusive, it is the theory that is incorrect,
>not the facts. This is the case with your "wheel loads are
>carried by compression of the rim" theory.
Well perhaps you shound stand by "the wheel stands on its spokes" and use a
rim made out of rubber. Isacc Newton, relativity, motion etc - facts.
May I remind you, any reference I have made to wheel loading, assumes
spokes which are not pre-tensioned. My method of wheelbuilding specifically
aims to reduce pre-loading of the rim to the minimum required to prevent
loss of lateral stability during service. As long as spokes do not become
loose, lateral stability is maintained. I was not prepared for and did not
want a discussion on load theory of the wheel as it depends upon components
used and actual constructional technique. Please note that the heading of
the thread is "The Basics of Wheel Alignment and Wheelbuilding"
I believe your statement to be specific to an overly tensioned wheel.
> In a classic arch, a load applied in the middle of the
>span is transferred to the ends of the arch through
>compression of the arch. For example, if a 100 lb. downward
>force is applied exactly at the middle of the arch, the arch
>will transfer 50 lb. of the downward force to one end of the
>arch, and 50 lb. of the downward force to the other end.
>
>For a bicycle rim this does not happen. You say that the
>bottom half of the rim (180 degrees) acts like an arch and
>carries loads by compression 90 degrees up around the
>periphery
Never mentioned the word.
>of the rim to the front and back of the wheel. If
>this were so, then the loads would have to then be
>transferred (by compression) to the top 180 degree arch of
>rim. But if that were the case, in order to support this
>load on the top arch of the rim, you would see corresponding
>increases in tension in the spokes at the top of the wheel,
>supporting the arch. However, all the analyses and
>measurements have shown that the small spoke tension
>increases that do occur at the top aren't nearly enough to
>support the load. Looking at the analysis in the first web
>site cited above, out of the 1000 N load applied at the
>bottom of the wheel, The vertical components of all the top
>spokes combined are only 100 N (10%). Where is the rest of
>the load being supported? Look at the bottom of the wheel,
>and you can see tension decreases account for about 950 N
>(95%) of the load. (Further, you'll see that there are
>spoke tension increases below rim, of about 5% of the total
>load). The only conclusion that can be reached is that the
>rim does not act like a classic arch, and only transfer a
>small portion of the external load to the top of the wheel.
>
>So, your theory that a load on the wheel increases
>compression on the rim is clearly inconsistent with the
>actual data.
Is the data relevant, is it shown that the spokes are adequately tensioned
and not over-tensioned? By this I mean that the spokes will become loose
when the service load is exceeded. Is it also shown that the spokes take a
direct line and are not looped around each other. Unless these conditions
are satisfied, it is improbable that the data would corespond to my wheel
build. If you disagree, perhaps you may think it raises serious doubt.
>If there is little increase in the tension in
>the top spokes, there can be little increase in compression
>in the top half of the rim, which means that there is little
> rim compression transferred from the bottom half of the
>rim. Therefore, the load on a wheel is not transferred
>from the ground to the hub primarily by rim compression.
You make an assumption based on pre-conceived ideas and measurements on
others wheels. My statements hold true for a wheel not pre-tensioned.
So how does the load transfer between tyre and spokes if not by compression?
Faries?
>
>The magnitudes of the spoke tension changes have been
>measured and calculated by many independent parties, who
>have all discovered
What they set out to "discover"
>the same patterns of load distribution.
> You can not simply dismiss the data, just because it
>doesn't match your ideas. If your theory can not account
>for the load distribution, your theory is wrong. Even if
>you do manage to concoct a some convoluted explanation to
>make your theory fit, that still doesn't make it correct.
I'll remind you, my aim was to reduce the tensioning of spokes to the
minimum required, and that this was acheivable throughthe pre-forming of the
spoke at its crossing.
>Occam's razor says that the simplest theory is the best -
>the theory that the external load is carried by the
>decreases in tension of a pre-tensioned wheel is simple,
>direct, and matches all the known data.
It would not apply should the spokes be loose before loading, so does not
apply to all tensile spoked wheels. To exclude some wheels because they are
not up to some sort of arbitary tension is not a valid argument to support
the theory that the wheel is supported by a decrease in tension.
Your explanation on a pretensioned wheel is influential without resorting to
the sites. I'll give it further thought.
I think this 95% shift may only occur in a grossly pre-tensioned wheel.
My methods do not require gross pre-tensioning so how similar, measured
results will be is questionable.
The fact still remains that lateral and radial stability along with reduced
spoke failures can be attained by pre-forming the spokes at their crossing.
Your argument for an overly tensioned wheel is good, but still off topic.
We should be discussing the merits or otherwise of the system I adhere to,
and not whether or not I understand how an arbitrary wheel is loaded. I
only referred to variance in cyclic loading of the spokes so as to avoid
specifics on whether they predominantly increased or decreased in tension.
You seem all out for a battle and use weapons of mass distraction in an
attempt to qualify it.
TJ
Trevor Jeffrey
Weisse Luft wrote in message ...
>
>is a bane to cyclic life which is why all automobile valve springs are
>kept in tension. And Valve springs that float or go into harmonic
>unloading will fail at very low cycle life.
Weisse Luft wrote in message ...
>No, I am not confused. If you know how to draw a free body diagram,
>you will see the error in your ways if you can accurately measure the
>rim deflection.
>
>Pretensioned structures easily confuse those who study them. Rest
>assured, a wheel stands on its spokes, be they wire, rope or pegs.
I told you, that you were confusing compression and tension. Poppet valves
always use springs in compression.
TJ
Trevor Jeffrey
Steels tested for this, have not shown it to be evident.
Reduction of magnitude of load variation may increase life of sample, but
the increase of tension before applying load variation does not show
benefits for component life.
TJ
carl...@comcast.net
<Trevor_...@beeeb.net> wrote:
[snip]
> I have ridden a bare rim after tearing a tyre cased by
>wheel collapse (constructed as instructed in JB's book) during sprinting.
>It was the poor stability of this wheel made me want to investigate further
>on constructional techniques.
[snip]
Dear Trevor,
Could you explain this a bit more?
That is, what exactly does "wheel collapse" mean to you?
It sounds catastrophic, since it caused a torn tire.
Did you somehow repair this wheel and continue riding on it
after removing the tire? Or was there a later experiment?
Chalo Colina sometimes rides what sounds like a
traditionally tensioned and trued bare-rim steel wheel
around Seattle without it collapsing under over 350 pounds
of rider:
or
Well, www.tinyurl.com hasn't gotten out of bed yet.
I assume, perhaps incorrectly, that you built a wheel to the
best of your ability to Jobst Brandt's suggestions and feel
that it had "poor stability" because it collapsed, not that
the wheel suffered from "poor stability" after it collapsed,
was repaired, and was ridden with no tire.
Carl Fogel