Spoke Tensiometer questions

[Tim McNamara]

[email protected] (Carl Fogel) writes:

> It's curious how many people feel that there are some
> things that man was never meant to measure with anything
> but the seat of his pants, like spoke tension.

Well, as I mentioned in the other thread, experience results
in perceptual learning. There's a biological limit to how
fine-grained perception can be (and even that can be
overcome to a degree- for example, vascular surgeons using
visual magnifying equipment can make tiny, accurate
movements that would not be possible without magnification).

> Oddly enough, the stress-relief of spokes that you call
> the single most important step may be one of these
> sacred cows:
>
> "The fatigue resistance of spokes was not tested for lack
> of suitable equipment." ("The Bicycle Wheel," 2nd edition,
> Part III, "Equations and Tests")
>
> And the stress-strain graphs of the tests of actual
> stainless steel spokes in that section (figure 69) don't
> look at all like the stress-strain graph used to explain
> elastic limits (figure 15). The curves of the actual spoke
> tests just climb toward failure without any intermediate
> drop at an elastic limit (which I gather is the normal
> behavior of stainless steel--it shows no elastic limit).
>
> Perhaps the third edition addressed this?

You'd have to ask Jobst, eh?

> To be honest, I can't see any objective difference between
> checking tension by ear (bikefixr's approach) and grabbing
> spoke pairs and giving 'em a good squeeze to relieve
> tension (current received wisdom on rec.bicycles.tech).

Oops, apples and oranges. Stress relieving is basically cold
setting the spokes to relieve residual stresses that remain
in the metal from the process of forming the elbow and head
(as I understand it, anyway). What bikefixr is talking about
is judging spoke tension by ear, which is unrelated to
stress relieving.

> Are there any studies showing actual results for these seat-of-the-
> pants approaches? That is, someone showing his ear to be
> as good at measuring tension as a high-quality
> tensiometer, or someone showing measurable effects from
> spoke-squeezing?

This is not a scientific study by any means, but in my
personal experience I can hear differences in spoke tension
that do not register on my Wheelsmith tensiometer. The
change in pitch caused by changing tension on a wire is
mathematically a very precise relationship. It's the same as
tuning a stringed instrument, in whcih case again the ear is
more sensitive than measuring the string tension. I don't
have any specific studies I can refer you to, this is from
my undegrad class in perception umpteen years ago. Come to
think of it, though, there was a thread on this a couple of
years ago and I had dug out my old textbooks to look up the
sensitivy of the ear to pitch changes.

> Either method may work. Anyone who can tune a violin can
> see the idea behind spoke-plucking, and a healthy squeeze
> might relieve some kind of tension in a spoke already
> under 200 to 500 lbs of tension.

Again, apples and oranges.

> I'm just curious if anyone has ever demonstrated that
> either method works in a fashion that could be presented
> and repeated in an engineering course.

You'd have to ask Jobst if his stress relieving technique
causes a high enough momentary increase in tension to cold
set the spoke material. But that's a different question than
judging spoke tension by pitch.

 

[Jobst Brandt]

An anonymous bikefixr snipes:

> You've been building wheels for years. Why bother with a
> tensiometer? Absolute tension is not important-eveness of
> tension around the wheel IS important.

That's an interesting concept. And how tight is right? I
suspect from what you say that you are unaware that wheel
strength is a direct function of spoke tension and that this
should be as high as a rim safely permits. That level of
tension is not easily assessed by any other means than a
tensiometer. Maybe you have another method and should let
others know what it is. I have described a method to find
that upper safe limit but I don't propose to use it for
successive wheels once that tension has been determined.

> If you measured the same wheel with 3 different
> tensiometers, you'll get 3 very different measures. So
> which one is right?

That's not the point. The point is repeatability and
protection from over or under tensioning. That works with a
completely uncalibrated instrument. However, the correct
tension must be determined at some time. Even your' claimed
difference in tensiometers is in my experience not
significant compared to guesses by people who as you
suggest, don't believe tension is important.

> In practice, it doesn't matter. What they are good for is
> draining your wallet and for novice builders who don;t
> have any "feel" yet. It might help keep them out of
> trouble, but I doubt it.

I see that you think engineers and engineering incompetent
to define what a structure should be while mechanics who
have been repeating the same errors for many years are
appropriate mentors. What gives you this aversion to
education and the scientific method?

> In 20 yrs of wheelbuilding, I have never once seen an
> amateur wheel I would ride on. Hell, I wouldn't have
> ridden MY first 20 wheels or so...

That's not saying much for your understanding of wheels. I
know many people who have ridden their first wheels for many
tens of thousand miles. Not being bicycle mechanics did not
stand in their way to building good and durable wheels. It
only takes reading ability, and a bit of manual dexterity. I
notice on occasion that bicycle shops that sell a wheel
building book do not read it themselves for the reasons that
you seem to express.

> So I suggest that you lace up, tension up. Keep as true
> and round as possible as you tension up, lube the nipple-
> rim interface regularly. I use subjective feel and
> sound. A human ear can hear far more subtle differences
> than the hand can feel. When they all feel the same,
> sound the same, I do minor tweaks and it's ready to
> roll. 8,000 pr later I've never had a wheel failure. I
> say keep doin' what you're doin' and comfortable with
> and refine your touch.

That's a nice testimonial but not much in the way of how
tight a wheel should be for someone who hasn't built
many wheels.

Jobst Brandt [email protected]

 

[Jobst Brandt]

Carl Fogel writes:

> It's curious how many people feel that there are some
> things that man was never meant to measure with anything
> but the seat of his pants, like spoke tension.

> Oddly enough, the stress-relief of spokes that you call
> the single most important step may be one of these
> sacred cows:

> "The fatigue resistance of spokes was not tested for lack
> of suitable equipment." ("The Bicycle Wheel," 2nd edition,
> Part III, "Equations and Tests")

Maybe instead of repeating this quote ominously, you might
add what you think you would gain from a fatigue test of a
specific spoke in a text about building wheels. The book has
been in print a long time and its fatigue values would even
when new not reveal what spokes to use for a given wheel.
How do you propose testing spoke fatigue?

> And the stress-strain graphs of the tests of actual
> stainless steel spokes in that section (figure 69) don't
> look at all like the stress-strain graph used to explain
> elastic limits (figure 15). The curves of the actual spoke
> tests just climb toward failure without any intermediate
> drop at an elastic limit (which I gather is the normal
> behavior of stainless steel--it shows no elastic limit).

To what are you alluding? These are curves taken directly
from a tensile tester. The reason for their presence is that
the long yield elongation of the DT spoke shows its
ductility and that it does not strain harden in use because
the wire has already been work hardened to its highest value
and is still ductile enough to be cold formed.

> Perhaps the third edition addressed this?

I see you are piqued and keep needling, just as Wheelsmith
did in his review of the book many years ago, claiming the
book was incomplete and therefore more or less useless. It
seems you are taking over his position in that respect.

> To be honest, I can't see any objective difference between
> checking tension by ear (bikefixr's approach) and grabbing
> spoke pairs and giving 'em a good squeeze to relieve
> tension (current received wisdom on rec.bicycles.tech).

"Giving 'em a good squeeze" is not to relieve tension (it
does not) nor is using a tensiometer. You can delete the "to
be honest" in you chiding manner, it only suggests that what
else you say without that preface is untrue, or at least
that you have not said all of the above with fill candor.

> Are there any studies showing actual results for these seat-of-the-
> pants approaches? That is, someone showing his ear to be
> as good at measuring tension as a high-quality
> tensiometer, or someone showing measurable effects from
> spoke-squeezing?

The reason this is not so is that there are many spoke
arrangements, crossed, radial, interleaved or not and a
great variety of rims and number of spokes, but you knew
that because it has all been here in this forum before,
something that you seem to be good at digging up from Google
when you think it might support your point of view. That
point of view remaining silent although obvious from many
allusions.

> Either method may work. Anyone who can tune a violin can
> see the idea behind spoke-plucking, and a healthy squeeze
> might relieve some kind of tension in a spoke already
> under 200 to 500 lbs of tension.

You don't need to list all the things that "may work" they
being myriad and little use to those reading this newsgroup.
Your ploy of raising and army of straw men to discredit
proven methods and confusing these with old wive's tales, is
not doing us any favors, especially when you occasionally
claim ignorance of science as you ramble on in plaintiff's
attorney style.

> I'm just curious if anyone has ever demonstrated that
> either method works in a fashion that could be presented
> and repeated in an engineering course.

Can you repeat the WHOLE question in plain English so it is
evident what it is you don't understand?

Jobst Brandt [email protected]

 

[Jim Beam]

[email protected] wrote:
> Carl Fogel writes:
>
>
>>It's curious how many people feel that there are some
>>things that man was never meant to measure with anything
>>but the seat of his pants, like spoke tension.
>
>
>>Oddly enough, the stress-relief of spokes that you call
>>the single most important step may be one of these
>>sacred cows:
>
>
>>"The fatigue resistance of spokes was not tested for lack
>>of suitable equipment." ("The Bicycle Wheel," 2nd edition,
>>Part III, "Equations and Tests")
>
>
> Maybe instead of repeating this quote ominously, you might
> add what you think you would gain from a fatigue test of a
> specific spoke in a text about building wheels. The book
> has been in print a long time and its fatigue values would
> even when new not reveal what spokes to use for a given
> wheel. How do you propose testing spoke fatigue?

to be fair jobst, i think some spoke fatigue testing would
be a good thing. if nothing else, it will give some
comparative measures on whether the different manufacturing
methods and materials used by wheelsmith, d.t., sapim, etc
make any difference to their fatigue lives.

>
>
>>And the stress-strain graphs of the tests of actual
>>stainless steel spokes in that section (figure 69) don't
>>look at all like the stress-strain graph used to explain
>>elastic limits (figure 15). The curves of the actual spoke
>>tests just climb toward failure without any intermediate
>>drop at an elastic limit (which I gather is the normal
>>behavior of stainless steel--it shows no elastic limit).
>
>
> To what are you alluding? These are curves taken
> directly from a tensile tester. The reason for their
> presence is that the long yield elongation of the DT
> spoke shows its ductility and that it does not strain
> harden in use because the wire has already been work
> hardened to its highest value and is still ductile
> enough to be cold formed.

"shows its ductility and that it does not strain harden in
use"??? your graphs /do/ show a plastic deformation zone
above the elastic yield point, do they not? and that region
continues to rise for stress for some strain percentage
before u.t.s.? that's continuing cold work continuing to
harden the material and consuming the last of the materials
ductility.

unless you have a precipitation hardening material, which
spoke wire is not afaik, the /only/ hardening is from cold
work. there is no strain aging. any continuing cold work
[i.e. any plastic deformation, not fatigue] continues to
harden, unless you are at u.t.s. no spoke is at uts - your
own graphs prove that. "already work hardened to its highest
value" is directly contradictory to "still ductile enough to
be cold formed".

>
>
>>Perhaps the third edition addressed this?
>
>
> I see you are piqued and keep needling, just as Wheelsmith
> did in his review of the book many years ago, claiming the
> book was incomplete and therefore more or less useless. It
> seems you are taking over his position in that respect.
>
>
>>To be honest, I can't see any objective difference between
>>checking tension by ear (bikefixr's approach) and grabbing
>>spoke pairs and giving 'em a good squeeze to relieve
>>tension (current received wisdom on rec.bicycles.tech).
>
>
> "Giving 'em a good squeeze" is not to relieve tension (it
> does not) nor is using a tensiometer. You can delete the
> "to be honest" in you chiding manner, it only suggests
> that what else you say without that preface is untrue, or
> at least that you have not said all of the above with
> fill candor.
>
>
>>Are there any studies showing actual results for these seat-of-the-
>>pants approaches? That is, someone showing his ear to be
>>as good at measuring tension as a high-quality
>>tensiometer, or someone showing measurable effects from
>>spoke-squeezing?
>
>
> The reason this is not so is that there are many spoke
> arrangements, crossed, radial, interleaved or not and a
> great variety of rims and number of spokes, but you knew
> that because it has all been here in this forum before,
> something that you seem to be good at digging up from
> Google when you think it might support your point of view.
> That point of view remaining silent although obvious from
> many allusions.
>
>
>>Either method may work. Anyone who can tune a violin can
>>see the idea behind spoke-plucking, and a healthy squeeze
>>might relieve some kind of tension in a spoke already
>>under 200 to 500 lbs of tension.
>
>
> You don't need to list all the things that "may work" they
> being myriad and little use to those reading this
> newsgroup. Your ploy of raising and army of straw men to
> discredit proven methods and confusing these with old
> wive's tales, is not doing us any favors, especially when
> you occasionally claim ignorance of science as you ramble
> on in plaintiff's attorney style.
>
>
>>I'm just curious if anyone has ever demonstrated that
>>either method works in a fashion that could be presented
>>and repeated in an engineering course.
>
>
> Can you repeat the WHOLE question in plain English so it
> is evident what it is you don't understand?
>
> Jobst Brandt [email protected]

 

[Carl Fogel]

[email protected] wrote in message news:<[email protected]>...
> Carl Fogel writes:
>
> > It's curious how many people feel that there are some
> > things that man was never meant to measure with anything
> > but the seat of his pants, like spoke tension.
>
> > Oddly enough, the stress-relief of spokes that you call
> > the single most important step may be one of these
> > sacred cows:
>
> > "The fatigue resistance of spokes was not tested for
> > lack of suitable equipment." ("The Bicycle Wheel," 2nd
> > edition, Part III, "Equations and Tests")
>
> Maybe instead of repeating this quote ominously, you might
> add what you think you would gain from a fatigue test of a
> specific spoke in a text about building wheels. The book
> has been in print a long time and its fatigue values would
> even when new not reveal what spokes to use for a given
> wheel. How do you propose testing spoke fatigue?
>
> > And the stress-strain graphs of the tests of actual
> > stainless steel spokes in that section (figure 69) don't
> > look at all like the stress-strain graph used to explain
> > elastic limits (figure 15). The curves of the actual
> > spoke tests just climb toward failure without any
> > intermediate drop at an elastic limit (which I gather is
> > the normal behavior of stainless steel--it shows no
> > elastic limit).
>
> To what are you alluding? These are curves taken
> directly from a tensile tester. The reason for their
> presence is that the long yield elongation of the DT
> spoke shows its ductility and that it does not strain
> harden in use because the wire has already been work
> hardened to its highest value and is still ductile
> enough to be cold formed.
>
> > Perhaps the third edition addressed this?
>
> I see you are piqued and keep needling, just as Wheelsmith
> did in his review of the book many years ago, claiming the
> book was incomplete and therefore more or less useless. It
> seems you are taking over his position in that respect.
>
> > To be honest, I can't see any objective difference
> > between checking tension by ear (bikefixr's approach)
> > and grabbing spoke pairs and giving 'em a good squeeze
> > to relieve tension (current received wisdom on
> > rec.bicycles.tech).
>
> "Giving 'em a good squeeze" is not to relieve tension (it
> does not) nor is using a tensiometer. You can delete the
> "to be honest" in you chiding manner, it only suggests
> that what else you say without that preface is untrue, or
> at least that you have not said all of the above with
> fill candor.
>
> > Are there any studies showing actual results for these
> > seat-of-the-pants approaches? That is, someone showing
> > his ear to be as good at measuring tension as a high-
> > quality tensiometer, or someone showing measurable
> > effects from spoke-squeezing?
>
> The reason this is not so is that there are many spoke
> arrangements, crossed, radial, interleaved or not and a
> great variety of rims and number of spokes, but you knew
> that because it has all been here in this forum before,
> something that you seem to be good at digging up from
> Google when you think it might support your point of view.
> That point of view remaining silent although obvious from
> many allusions.
>
> > Either method may work. Anyone who can tune a violin can
> > see the idea behind spoke-plucking, and a healthy
> > squeeze might relieve some kind of tension in a spoke
> > already under 200 to 500 lbs of tension.
>
> You don't need to list all the things that "may work" they
> being myriad and little use to those reading this
> newsgroup. Your ploy of raising and army of straw men to
> discredit proven methods and confusing these with old
> wive's tales, is not doing us any favors, especially when
> you occasionally claim ignorance of science as you ramble
> on in plaintiff's attorney style.
>
> > I'm just curious if anyone has ever demonstrated that
> > either method works in a fashion that could be presented
> > and repeated in an engineering course.
>
> Can you repeat the WHOLE question in plain English so it
> is evident what it is you don't understand?
>
> Jobst Brandt [email protected]

Dear Jobst,

You seem to have replied at considerable length to a
question that you claim not to understand.

Since you didn't answer it, I almost believe you.

Carl Fogel