Spoke Tensiometers: Which brand is better?

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Jeff S.

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Jun 25, 2001, 11:15:44 PM6/25/01
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I hear that Park, Wheelsmith and Hozan make one. I know the Hozan is super
pricey. Can anyone discuss the Park. Thanks.

Jeff S.


Tim McNamara

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Jun 26, 2001, 12:27:19 AM6/26/01
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In article <9h8uov$lnt$1...@bob.news.rcn.net>, Jeff S. <jef...@rcn.com>
wrote:

> I hear that Park, Wheelsmith and Hozan make one. I know the Hozan is super
> pricey. Can anyone discuss the Park. Thanks.

You can build excellent wheels without one, plucking the spokes to
check for evenness of tension. This is actually a remarkably sensitive
way to check for even tension on each side of the wheel, unless you're
tone deaf of course.

The instructions for how to determine proper spoke tension without a
tensiometer can be found in The Bicycle Wheel by Jobst Brandt,
available in most bike shops. It's quite easy, actually. The
tensiometer speeds up getting to the proper tension in the *second*
**identical** wheel but really doesn't help you much with the first
wheel.

I have the Wheelsmith tensiometer. It is simple and easy to use, but
there is no way to verify whether the calibration scale is accurate.
You read a scale on the caliper and then compare that reading with a
chart provided by Wheelsmith, but it doesn't take all the possible
variables affectivn spoke tension into account.

The best investment you can make is in Jobst's book, if you don't
already have that. Most bike shops carry it, and failing that you can
get it through amazon.com or alibris.com

David Green

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Jun 26, 2001, 5:09:07 AM6/26/01
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Tim McNamara <tim...@bitstream.net> wrote in message
news:250620012327190909%tim...@bitstream.net...

> The best investment you can make is in Jobst's book, if you don't
> already have that. Most bike shops carry it, and failing that you can
> get it through amazon.com or alibris.com

That may be true in the USA, but here in the UK I doubt whether any bike
shops carry it. Certainly I have never seen it in any. Neither do most book
shops, although they can obtain copies on special order.
--
David Green david...@smallworld.co.uk
Cambridge UK

Dirk Lenart

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Jun 26, 2001, 8:01:36 AM6/26/01
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Hi there,

I bought mine at amazon.co.uk, got it within a week!
Dirk Lenart
Belgium

Larry Bennett

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Jun 26, 2001, 8:13:04 AM6/26/01
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Fatbrain will deliver it to Boston for $21.43. Of course your LBS (local
book store) would be happy to order it. Most LBS (local bike shop) carry it.
Too bad many either don't read it, or don't follow it's principles. For
price comparisons, see:
http://www.addall.com/New/submitNew.cgi?query=0960723641&type=ISBN&location=
10000&state=AK&dispCurr=USD

"Dirk Lenart" <dirk....@pandora.be> wrote in message
news:3b3877b8...@news.pandora.be...

Tony Raven

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Jun 26, 2001, 6:25:12 AM6/26/01
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"David Green" <david...@nospam.smallworld.co.uk> wrote in message
news:3b3852af$0$12250$ed9e...@reading.news.pipex.net...

I'm in the UK and I've seen it in bike shops. Its hardly and overnight
emergency so Amazon or a bookshop order isn't that much of a problem.

Tony

Jules Nijst

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Jun 26, 2001, 3:31:29 PM6/26/01
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David,

I ordered one via internet bookstore Amazon UK.

David Green wrote:

--
Jules Nijst

Tim McNamara

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Jun 26, 2001, 3:39:13 PM6/26/01
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In article <3b3852af$0$12250$ed9e...@reading.news.pipex.net>, David
Green <david...@nospam.smallworld.co.uk> wrote:

Good point. I was forgetting again that the US isn't the center of the
universe, Ari Fleischer notwithstanding.

Orin Eman

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Jun 27, 2001, 4:40:51 AM6/27/01
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Tim McNamara wrote:

> The best investment you can make is in Jobst's book, if you don't
> already have that. Most bike shops carry it, and failing that you can
> get it through amazon.com or alibris.com

Agreed. Then there is Schraner's "The Art of Wheelbuilding". Jobst's book
first,
definitely. I prefer Schraner's method of lacing the wheel - you see the
relation of the hub to the rim after two spokes - makes lining up the
logos on the hub and rim easy if that's what you want.

Back to tensiometers - I too have the Wheelsmith. Plucking the spokes to
check evenness of tension is much easier for me than using tensiometer
and I can hear differences that would be difficult to see on the Wheelsmith's
scale.

Orin.

Qui si parla Campagnolo

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Jun 27, 2001, 9:04:52 AM6/27/01
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jeff-<< I hear that Park, Wheelsmith and Hozan make one. I know the Hozan is

super
pricey. Can anyone discuss the Park. >>


Wheelsmith one is great-

Peter Chisholm
Vecchio's Bicicletteria
1833 Pearl ST.
Boulder, CO, 80302
(303)440-3535
http://www.vecchios.com

Tim McNamara

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Jun 27, 2001, 9:51:24 AM6/27/01
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In article <3B399C13...@nwlink.com>, Orin Eman <or...@nwlink.com>
wrote:

> Tim McNamara wrote:
>
> > The best investment you can make is in Jobst's book, if you don't
> > already have that. Most bike shops carry it, and failing that you can
> > get it through amazon.com or alibris.com
>
> Agreed. Then there is Schraner's "The Art of Wheelbuilding".
> Jobst's book first, definitely. I prefer Schraner's method of lacing
> the wheel - you see the relation of the hub to the rim after two
> spokes - makes lining up the logos on the hub and rim easy if that's
> what you want.

The problem I have with Schraner's book is that he offers both good
advice and voodoo advice without making it clear which is which. Lning
up logos is the least of my concerns in building a wheel. Making sure
the spoke holes in the rim and flanges are properly lined up is more
important.

> Back to tensiometers - I too have the Wheelsmith. Plucking the spokes to
> check evenness of tension is much easier for me than using tensiometer
> and I can hear differences that would be difficult to see on the Wheelsmith's
> scale.

This is my experience as well. I designate one "master spoke" to
compare the rest to by plucking and pretty much just use the
tensiometer to check that one.

marten gerritsen

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Jun 27, 2001, 10:53:41 AM6/27/01
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Qui si parla Campagnolo wrote:

> jeff-<< I hear that Park, Wheelsmith and Hozan make one. I know the Hozan is
> super
> pricey. Can anyone discuss the Park. >>
>
> Wheelsmith one is great-

here's an other $$$$ one, : http://www.bmd.nl/test/test_uk_spm.htm
/Marten

A Muzi

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Jun 27, 2001, 7:37:20 PM6/27/01
to

Tim McNamara wrote:

>
> The problem I have with Schraner's book is that he offers both good
> advice and voodoo advice without making it clear which is which. Lning
> up logos is the least of my concerns in building a wheel. Making sure
> the spoke holes in the rim and flanges are properly lined up is more
> important.

I'm with Tim. I purposefully do not LOOK at the labels when I build a wheel and so
some are facing one way, some another. Riders who obsess over label placement can
buy wheels anywhere. Mine stay true.
--
Yellow Jersey, Ltd
http://www.yellowjersey.org
Open every day since 1 April, 1971


Qui si parla Campagnolo

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Jun 28, 2001, 9:33:07 AM6/28/01
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Lacing is lacing, if you can lace it with the labels any which way, you can
lace it with the labels thru the valve hole. It isn't any 'harder' or more
complicated and it's a nice touch, particularly if you charge labor for a wheel
build.
It has bugged me for years thet the 'pros' at Wheelsmith can't seem to line up
hub logos on their wheels, that's all they do!!!!

If ya can't line up logos, most wheels builders can't build a wheel either.
Some exceptions tho, but it is a really small 'skill', that most don't seem to
have.

Phil Holman

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Jun 28, 2001, 9:28:38 AM6/28/01
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Tim McNamara wrote in message <250620012327190909%tim...@bitstream.net>...

>In article <9h8uov$lnt$1...@bob.news.rcn.net>, Jeff S. <jef...@rcn.com>
>wrote:
>
>> I hear that Park, Wheelsmith and Hozan make one. I know the Hozan is
super
>> pricey. Can anyone discuss the Park. Thanks.
>
>You can build excellent wheels without one, plucking the spokes to
>check for evenness of tension. This is actually a remarkably sensitive
>way to check for even tension on each side of the wheel, unless you're
>tone deaf of course.

I know 2 tunes, one is Amazing Grace and the other one isn't :-)
I guess I can use my guitar tuner.

>I have the Wheelsmith tensiometer. It is simple and easy to use, but
>there is no way to verify whether the calibration scale is accurate.
>You read a scale on the caliper and then compare that reading with a
>chart provided by Wheelsmith, but it doesn't take all the possible
>variables affectivn spoke tension into account.

Interesting, I've never really had one of these in my hand but I'm assuming
it converts lateral deflection under a constant force into axial tension.
The chart, I'm also assuming, gives values for different spoke gauges. Other
variables could be cross section shape and material (Steel, Ti). It can be a
good comparitive tool even if your wheel is out of tune with the rest of the
orchestra.

>
>The best investment you can make is in Jobst's book, if you don't
>already have that. Most bike shops carry it, and failing that you can
>get it through amazon.com or alibris.com

I agree
Phil Holman

Alex Rodriguez

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Jun 28, 2001, 2:11:35 PM6/28/01
to
In article <eQRpHY9$AHA.263@cpmsnbbsa09>, phi...@email.msn.com says...

>Interesting, I've never really had one of these in my hand but I'm assuming
>it converts lateral deflection under a constant force into axial tension.
>The chart, I'm also assuming, gives values for different spoke gauges. Other
>variables could be cross section shape and material (Steel, Ti). It can be a
>good comparitive tool even if your wheel is out of tune with the rest of the
>orchestra.

It works just as you describe. For the tone deaf, it is a handy tool to
have and not very difficult to use.


-----------------
Alex __O
_-\<,_
(_)/ (_)

Jobst Brandt

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Jun 28, 2001, 2:50:39 PM6/28/01
to
Phil Holman writes:

> Interesting, I've never really had one of these in my hand but I'm
> assuming it converts lateral deflection under a constant force into
> axial tension. The chart, I'm also assuming, gives values for
> different spoke gauges. Other variables could be cross section shape

> and material (Steel, Ti). It can be a good comparative tool even if


> your wheel is out of tune with the rest of the orchestra.

The problem with all tensiometers that I have seen offered is that
they measure across the spoke so part of the reading is spoke
thickness and none of these instruments allows zeroing the gauge on
the spoke, tare, so to speak. Besides, Hozan in particular and others
I've seen use too large a test load, one that will affect tension of
the spoke being measured.

For this reason I designed a precision gauge that measures from the
support side and uses a dial micrometer so that small deflections can
be used. It also zeroes on the spoke and, because it uses such a
small deflection, bending stiffness over a 100mm span is small enough
to make the difference between 1.6 and 2.0mm diameter spokes
insignificant. The instrument is shown in "the Bicycle Wheel" and was
in production at Avocet but shops were unwilling to pay $300 for this
precision calibrated gauge. 100 of them were subsequently sold by DT
in Europe.

Jobst Brandt <jbr...@hpl.hp.com>

Jon Isaacs

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Jun 28, 2001, 3:38:10 PM6/28/01
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> know 2 tunes, one is Amazing Grace and the other one isn't :-)
>I guess I can use my guitar tuner.

Tried it, Guitar tuners don't seem to work.
Jon Isaacs

Karl Frisch

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Jun 28, 2001, 3:52:52 PM6/28/01
to

Jobst Brandt wrote:

>
> For this reason I designed a precision gauge that measures from the
> support side and uses a dial micrometer so that small deflections can
> be used. It also zeroes on the spoke and, because it uses such a
> small deflection, bending stiffness over a 100mm span is small enough
> to make the difference between 1.6 and 2.0mm diameter spokes
> insignificant. The instrument is shown in "the Bicycle Wheel" and was
> in production at Avocet but shops were unwilling to pay $300 for this
> precision calibrated gauge. 100 of them were subsequently sold by DT
> in Europe.
>
> Jobst Brandt <jbr...@hpl.hp.com>

You know I had one of those fine instruments on the bench at
PAB......anyone see it recently? I understand a junior mechanic snatched
it. A truly irreplaceable toy for those who care about such things. By the
way one of the bicycle magazines ran an article on "one of the worlds
finest mechanics," in one picture he is holding an instrument that looks
identical to the Brandt/Avocet device.....the caption was something to
like "a custom tensiometer built by his brother" just plain weird.

Karl

Jobst Brandt

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Jun 28, 2001, 4:38:13 PM6/28/01
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Karl Frisch writes:


> Jobst Brandt wrote:

>> For this reason I designed a precision gauge that measures from the
>> support side and uses a dial micrometer so that small deflections can
>> be used. It also zeroes on the spoke and, because it uses such a
>> small deflection, bending stiffness over a 100mm span is small enough
>> to make the difference between 1.6 and 2.0mm diameter spokes
>> insignificant. The instrument is shown in "the Bicycle Wheel" and was
>> in production at Avocet but shops were unwilling to pay $300 for this
>> precision calibrated gauge. 100 of them were subsequently sold by DT
>> in Europe.

> You know I had one of those fine instruments on the bench at


> PAB......anyone see it recently? I understand a junior mechanic
> snatched it. A truly irreplaceable toy for those who care about such
> things. By the way one of the bicycle magazines ran an article on
> "one of the worlds finest mechanics," in one picture he is holding
> an instrument that looks identical to the Brandt/Avocet device...

> the caption was something to like "a custom tensiometer built by his
> brother" just plain weird.

Wheelsmith has my first one and a second one while Tim Parker,
probably the man in the article, had his brother build about ten of
them in his own machine shop from my drawings. Unfortunately the
person who got your gauge probable doesn't use it but keeps it as a
trophy trinket.

I have offered the drawings to several bicycle tool folks but they
don't think there is a market for it. My impression was that they
didn't believe there was any benefit from it in the first place, from
the questions they asked. I use mine with every wheel I build to
sample tension level. I pluck spokes to make the wheel uniform
because I can do that more easily.

Jobst Brandt <jbr...@hpl.hp.com>

Dan Goldenberg

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Jun 28, 2001, 5:40:36 PM6/28/01
to

Jobst Brandt wrote:
>
I use mine with every wheel I build to
> sample tension level.

I am assuming this is to arrive at a tension value determined previously
by the method described in your book. What value does this typically
come out to for an MA-2 rim, 36 spokes?

Thanks
Dan Goldenberg

Tim McNamara

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Jun 28, 2001, 6:39:42 PM6/28/01
to
In article <eQRpHY9$AHA.263@cpmsnbbsa09>, Phil Holman
<phi...@email.msn.com> wrote:

> I wrote:
> >I have the Wheelsmith tensiometer. It is simple and easy to use, but
> >there is no way to verify whether the calibration scale is accurate.
> >You read a scale on the caliper and then compare that reading with a
> >chart provided by Wheelsmith, but it doesn't take all the possible
> >variables affectivn spoke tension into account.

Phil wrote:
> Interesting, I've never really had one of these in my hand but I'm assuming
> it converts lateral deflection under a constant force into axial tension.
> The chart, I'm also assuming, gives values for different spoke gauges. Other
> variables could be cross section shape and material (Steel, Ti). It can be a
> good comparitive tool even if your wheel is out of tune with the rest of the
> orchestra.

The Wheelsmith tensiometer is two symmetrical plates with a pivot bolt
on which they rotate. There are two arms or ears which hook over the
spoke and are pushed apart by a compression spring. The device is
"zeroed out" by rotating this spring. On the outer edges of the plates
are two scales, sort of like slide rule scales. These offer a reading
which is then compared to the calibration chart. The chart offers
values in "kgf" for several sifferent sized spokes (14 straight, 15
straight, 14 DB, 13 DB, 14 aero IIRC).

There are lots of potential confounds with this device, especially
friction in the pivoting movement between the plates and between the
ears and the spokes. It is a reasonable tool for relative measurement
between spokes but may not be a good tool for absolute measurement of
spoke tension.

Tim McNamara

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Jun 28, 2001, 6:44:27 PM6/28/01
to
In article <9hfu9v$7ba$1...@hplms2.hpl.hp.com>, Jobst Brandt
<jbr...@hpl.hp.com> wrote:

> Phil Holman writes:
>
> > Interesting, I've never really had one of these in my hand but I'm
> > assuming it converts lateral deflection under a constant force into
> > axial tension. The chart, I'm also assuming, gives values for
> > different spoke gauges. Other variables could be cross section shape
> > and material (Steel, Ti). It can be a good comparative tool even if
> > your wheel is out of tune with the rest of the orchestra.
>
> The problem with all tensiometers that I have seen offered is that
> they measure across the spoke so part of the reading is spoke
> thickness and none of these instruments allows zeroing the gauge on
> the spoke, tare, so to speak. Besides, Hozan in particular and others
> I've seen use too large a test load, one that will affect tension of
> the spoke being measured.

You can zero the Wheelsmith tool on a spoke that is not under tension.
I'm not sure if that addresses your concern, however.

I hadn't thought of the test load affecting spoke tension
significantly; this seems like it could cause a falsely high reading?

Jobst Brandt

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Jun 28, 2001, 7:10:59 PM6/28/01
to
Dan Goldenberg writes:

> I use mine with every wheel I build to sample tension level.

> I am assuming this is to arrive at a tension value determined previously
> by the method described in your book. What value does this typically
> come out to for an MA-2 rim, 36 spokes?

Yes, but then my tensiometer was never calibrated and I just use the
dial readings to characterize tension. 0.013 right side rear, 0.025
front wheel. That doesn't help you much but it works great for me.

The Avocet units had metric dials by Starrett. Mine has an inch dial
by Mitutoyo.

Jobst Brandt <jbr...@hpl.hp.com>

Jobst Brandt

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Jun 28, 2001, 7:27:29 PM6/28/01
to
Tim McNamara writes:

>> The problem with all tensiometers that I have seen offered is that
>> they measure across the spoke so part of the reading is spoke
>> thickness and none of these instruments allows zeroing the gauge on
>> the spoke, tare, so to speak. Besides, Hozan in particular and
>> others I've seen use too large a test load, one that will affect
>> tension of the spoke being measured.

> You can zero the Wheelsmith tool on a spoke that is not under
> tension. I'm not sure if that addresses your concern, however.

I don't think I made that clear. My instrument has a dial which is
set to zero, on the spoke before applying the test load. Subsequently
the reading on the dial gives the deflection in the units of the dial
micrometer. The Wheelsmith instrument has no dial it uses a vernier
scale that is rigidly attached to the two scissor image halves.
Besides having a friction pivot, it has no bearing between spoke and
contacts so that the cosine error binds the instrument. The Avocet
unit used two ball bearings as spoke support so there was essentially
no friction involved in the reading.

> I hadn't thought of the test load affecting spoke tension
> significantly; this seems like it could cause a falsely high reading?

With Hozan, that is appreciable and on top of that, one presses down
on the spoke with the hand grip so that all the application force is
resisted by the spoke. It's a BAD instrument. DT's new one has a lot
of potential but its gauge length is too short, and it measures across
the wire, and it has friction contact, and it uses too large a test
load, and it isn't zeroed. It's electronics are great and I would
love to have had them apply that to the Avocet/DT tensiometer but I
suspect they didn't appreciate what they had. I would have bought one
just for the micro processor abilities. They haven't talked to me
since I panned their revolution spoke years ago. Having used Berg and
Redaelli 1.5mm spokes years ago and had them fail in torsion, I know
how bad windup failures are. DT's 2.0mm ends cause more torsion than
the ones I mentioned at 1.8mm. It's the friction, not the thread ramp
that causes all the problem and that increases with thread diameter as
it does with 2.34mm diameter spokes.

Jobst Brandt <jbr...@hpl.hp.com>

Jeffrey L. Bell

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Jun 28, 2001, 8:31:57 PM6/28/01
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>Tried it, Guitar tuners don't seem to work.
>Jon Isaacs

Although you could use the guitar tuner to tune a guitar, say,
and then compare the tones by ear. Even if you're Roger Waters
you should be able to tell with more accuracy than matters.

-Jeff Bell

Phil Holman

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Jun 28, 2001, 11:56:05 PM6/28/01
to

Jobst Brandt wrote in message <9hfu9v$7ba$1...@hplms2.hpl.hp.com>...

Having a dial micrometer does push the cost up. Anyone ever thought about
using just 2 contact points and inducing a lateral load by wind up. The
deflection measurement would be similar to a torque wrench measuring the
position of the exiting spoke onto a scale held by an arm aligned with the 2
contact points. Different spoke lengths could be accounted for by adjusting
the spacing of the contact points. Hmmm another retirement project.
Is it too difficult to revise the Wheelsmith device to compensate for spoke
gauge. For $100 the device does not look very impressive.
Phil Holman
>
>Jobst Brandt <jbr...@hpl.hp.com>


Phil Holman

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Jun 29, 2001, 12:00:19 AM6/29/01
to

Jon Isaacs wrote in message
<20010628153810...@ng-fc1.aol.com>...

Maybe you were blowing in the wrong pipe.......couldn't resist that.
Phil Holman


Jon Isaacs

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Jun 29, 2001, 9:33:31 AM6/29/01
to


I just checked out one wheel by comparing it to a guitar, it was actually quite
easy and the spokes seemed to be near low A# on the big string. These are 15
gage spokes that seem to have a free length of between 175 and 180 mm. From
this it should be relatively simple to estimate the tension which I will do at
work. (Note, this A# is about 116 Hz if my music and math are correct.)

Some random observations:

1. Pinching the spokes where they cross raises the natural frequency so it is
clear that the effective length is the total free length.

2. I tried this on the rear wheel of the same bike but was unsuccessful. I
suspect was because the rear wheel is a disk wheel. :-)

3. It seems to me that measuring frequency is an easy and likely more
accurate way to tune a wheel. Consider this scheme:

A tone generator which is set for a given frequency which depends on the spoke
diameter and free length. All spokes are then compared to this and they will
not only have a known tension but an equal tension.

This is really just an extension of plucking the spoke, but it does provide an
absolute measurement and absolute comparison.

Imagine little tuner with a switch for various lengths and gages and such a
thing could be built for just a few dollars.

Enough is enough,

jon isaacs


Dan Goldenberg

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Jun 29, 2001, 10:47:09 AM6/29/01
to

Tim McNamara wrote:
>
> It is a reasonable tool for relative measurement
> between spokes but may not be a good tool for absolute measurement of
> spoke tension.

What kind of accuracy do you think this tool might achieve for an
absolute measurement? Would we be talking about an accuracy of
plus/minus 5-10% or so, or possibly worse (at least for a new one that
has been calibrated)?

Thanks
Dan Goldenberg

Tim McNamara

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Jun 29, 2001, 1:34:34 PM6/29/01
to
In article <9hgeh1$d2j$1...@hplms2.hpl.hp.com>, Jobst Brandt
<jbr...@hpl.hp.com> wrote:

> Tim McNamara writes:
>
> >> The problem with all tensiometers that I have seen offered is that
> >> they measure across the spoke so part of the reading is spoke
> >> thickness and none of these instruments allows zeroing the gauge on
> >> the spoke, tare, so to speak. Besides, Hozan in particular and
> >> others I've seen use too large a test load, one that will affect
> >> tension of the spoke being measured.
>
> > You can zero the Wheelsmith tool on a spoke that is not under
> > tension. I'm not sure if that addresses your concern, however.
>
> I don't think I made that clear. My instrument has a dial which is
> set to zero, on the spoke before applying the test load. Subsequently
> the reading on the dial gives the deflection in the units of the dial
> micrometer. The Wheelsmith instrument has no dial it uses a vernier
> scale that is rigidly attached to the two scissor image halves.
> Besides having a friction pivot, it has no bearing between spoke and
> contacts so that the cosine error binds the instrument.

Is this why the instructions for the Wheelsmith tool are to swivel it
up and down a few times? To try to relieve the binding due to
friction?

> They haven't talked to me since I panned their revolution spoke years
> ago.

I remember that. IIRC the extreme swaging of the spoke caused
longitudinal stress fractures in the thin section.

> Having used Berg and Redaelli 1.5mm spokes years ago and had them
> fail in torsion, I know how bad windup failures are. DT's 2.0mm ends
> cause more torsion than the ones I mentioned at 1.8mm. It's the
> friction, not the thread ramp that causes all the problem and that
> increases with thread diameter as it does with 2.34mm diameter
> spokes.

Doe the friction increase with spoke diameter because there is greater
contact area between the nipple threads and the spoke threads?

Tim McNamara

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Jun 29, 2001, 1:39:17 PM6/29/01
to
In article <9hgi9t$61l$1...@news.eecs.umich.edu>, Jeffrey L. Bell
<jlb...@agitato.eecs.umich.edu> wrote:

You'd need an acoustic chromatic tuner rather than one designed only to
measure EADGBE. The other problem is that the spoke doesn't sustain
the tone long enough for the tuner to analyze the frequency. Watch the
delay between plucking a guitar string and the tuner settling down to a
pitch- the harmonic overtones confuse the tuner and as these die out
the fundamental is left; it takes most tuners several seconds. The
average spoke damps out within about a second or so, whereas a guitar
string can sustain for much, much longer.

Tim McNamara

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Jun 29, 2001, 1:42:49 PM6/29/01
to
In article <3B3C94ED...@pss.boeing.com>, Dan Goldenberg
<daniel.g...@pss.boeing.com> wrote:

One of the engineers would be qualified to answer this, not me. Jobst
has pointed out how spoke thickness and friction can confound
measurement with this tool. Different alloys may also have an effect-
Wheelsmith calibrates the tools on their brand of spokes.

Jon Isaacs

unread,
Jun 29, 2001, 2:13:49 PM6/29/01
to
>You'd need an acoustic chromatic tuner rather than one designed only to
>measure EADGBE. The other problem is that the spoke doesn't sustain
>the tone long enough for the tuner to analyze the frequency. Watch the
>delay between plucking a guitar string and the tuner settling down to a
>pitch- the harmonic overtones confuse the tuner and as these die out
>the fundamental is left; it takes most tuners several seconds. The
>average spoke damps out within about a second or so, whereas a guitar
>string can sustain for much, much longer.
>

The one I tried is a rather sophisticated KORG tuner which is chromatic and
unlike the cheaper ones does not need to be preselected. If you play a G that
is 10 cents off, it will tell you that it is a G and it is 10 cent low. It
also has a selectable response time. You can actually play along and it will
often follow you if you are playing single notes.

My guess the frequency content of a plucked spoke is not sufficiently narrow to
allow the tuner to determine the frequency. When I have a moment I think I
will hook up a microphone to a digital oscope and see what the waveform of a
plucked spoke looks like. Of course one could do this with a PC and a sound
card as well.

jon isaacs

Tim McNamara

unread,
Jun 29, 2001, 3:12:51 PM6/29/01
to
In article <20010629141349...@ng-cg1.aol.com>, Jon Isaacs
<joni...@aol.com> wrote:

> >You'd need an acoustic chromatic tuner rather than one designed only to
> >measure EADGBE. The other problem is that the spoke doesn't sustain
> >the tone long enough for the tuner to analyze the frequency. Watch the
> >delay between plucking a guitar string and the tuner settling down to a
> >pitch- the harmonic overtones confuse the tuner and as these die out
> >the fundamental is left; it takes most tuners several seconds. The
> >average spoke damps out within about a second or so, whereas a guitar
> >string can sustain for much, much longer.
> >
>
> The one I tried is a rather sophisticated KORG tuner which is chromatic and
> unlike the cheaper ones does not need to be preselected. If you play a G that
> is 10 cents off, it will tell you that it is a G and it is 10 cent low. It
> also has a selectable response time. You can actually play along and it will
> often follow you if you are playing single notes.

Better tuner than the ones I have. ;-)

> My guess the frequency content of a plucked spoke is not sufficiently
> narrow to allow the tuner to determine the frequency. When I have a
> moment I think I will hook up a microphone to a digital oscope and
> see what the waveform of a plucked spoke looks like.

I think you're probably right in that a spoke is much stiffer than a
guitar string, much shorter and not cleanly bridged at either end, plus
being crossed by another spoke somewhere along its length.

Let us know, I'd be interested at least. Don't know about anyone
else...

Orin Eman

unread,
Jun 30, 2001, 2:40:11 AM6/30/01
to
Tim McNamara wrote:

I can't tell from the context or the messages on my server, but if we are
talking
about the Wheelsmith, I don't see why spoke thickness at least would be an
issue.

The calibration chart supplied with the Wheelsmith tensiometer has a set of
tensions
corresponding to tensiometer readings _per spoke type_. As long as
readings
are repeatable (and in my experience, to my ability of reading the verner,
they are,)
then for example on my tensiometer, a reading of 60 means 64 kgf on a 2 mm
spoke,
93 kgf on a 1.8 mm spoke, 105 kgf on a 1.7 mm spoke.

Of course, accuracy does depend on how they produced that chart... they may
just
take a few readings and use a formula/interpolation for the various spoke
types.
I don't know. They could hide constant offsets, non-linearities or whatever
in the
production of that table.

Orin.

Peter Cole

unread,
Jun 30, 2001, 3:25:06 PM6/30/01
to
Freebie PC tone generator:

http://www.nch.com.au/action/index.html

"Jon Isaacs" <joni...@aol.com> wrote in message
news:20010629093331...@ng-ma1.aol.com...

Jon Isaacs

unread,
Jun 30, 2001, 4:43:42 PM6/30/01
to
>Freebie PC tone generator:
>
>http://www.nch.com.au/action/index.html

Thanks, Looks nice.

jon isaacs

Jobst Brandt

unread,
Jun 30, 2001, 5:01:09 PM6/30/01
to
Tim McNamara writes:

>> Having used Berg and Redaelli 1.5mm spokes years ago and had them
>> fail in torsion, I know how bad windup failures are. DT's 2.0mm
>> ends cause more torsion than the ones I mentioned at 1.8mm. It's
>> the friction, not the thread ramp that causes all the problem and
>> that increases with thread diameter as it does with 2.34mm diameter
>> spokes.

> Doe the friction increase with spoke diameter because there is
> greater contact area between the nipple threads and the spoke
> threads?

The main effect is radius of action. That's why nipples don't turn
when spoke twist unscrews, the spoke turns in the threads, being at a
far smaller radius. One might guess that the smaller diameter spoke,
having the same thread pitch, would, through it's steeper helix, have
higher torque, but this effect is way below frictional drag, the helix
effect being so small that most people cannot distinguish tightening
torque from loosening torque.

Jobst Brandt <jbr...@hpl.hp.com>

Jobst Brandt

unread,
Jun 30, 2001, 5:10:09 PM6/30/01
to
Tim McNamara writes:

>> What kind of accuracy do you think this tool might achieve for an
>> absolute measurement? Would we be talking about an accuracy of
>> plus/minus 5-10% or so, or possibly worse (at least for a new one
>> that has been calibrated)?

> One of the engineers would be qualified to answer this, not me.
> Jobst has pointed out how spoke thickness and friction can confound
> measurement with this tool. Different alloys may also have an
> effect- Wheelsmith calibrates the tools on their brand of spokes.

All steels have the same modulus of elasticity, regardless of alloy or
heat treatment. Their only difference lies in damping as we know from
the high pitch tone of drill steel compared to a nail of the same
cross section.

As to detecting absolute tension by tone, this is an illusion because
the resonant frequency depends on density (solid steel) which is
different from guitar strings, and free length, something that most
bicycle spokes do not have because they contact another spoke at
partial span and the two spokes do not resonate at the same frequency
to produce multiple harmonics that are only reasonably separable by a
frequency analyzer.

This has been done and found ineffective.

Jobst Brandt <jbr...@hpl.hp.com>

Jon Isaacs

unread,
Jun 30, 2001, 8:35:29 PM6/30/01
to
>All steels have the same modulus of elasticity, regardless of alloy or
>heat treatment.

For normal purposes this is true but I have measured steels that range from
about 27 Msi to around 32 Msi.

>As to detecting absolute tension by tone, this is an illusion because
>the resonant frequency depends on density (solid steel) which is
>different from guitar strings, and free length, something that most
>bicycle spokes do not have because they contact another spoke at
>partial span and the two spokes do not resonate at the same frequency
>to produce multiple harmonics that are only reasonably separable by a
>frequency analyzer.

I was skeptical about this and still am, however...

The purpose of comparing the tone to that of a guitar is determine the
frequency of the resonance of the spoke and from that determine the tension.
The sound of the plucked spoke is certainly highly damped but I was surprised
at how easy it was to compare the fundemental tone to that of a guitar. It may
be that my ear is better than the typical bicycle mechanics as I have been
playing musical instruments for nearly 40 years. It is also possible that this
tone is not the fundemental tone.

The question of free length is important. My test was to pinch the spokes at
their major crossing and listen to the effect. It is clear that the tone is
raised by the appropriate amount and so that the effective free length is
approximately the distance from the nipple to hub.

A radially laced wheel will also provide an opportunity to have a relatively
unambigious free length.


>This has been done and found ineffective.
>

Some of the rough calculations I have done seem to result in spoke tensions
that are much lower than I would expect. I am interested in doing some similar
tests when the actual load is known.

I suspect my model is poor.

I would be interested in knowing numbers for actual spoke tensions.

jon isaacs

Tim McNamara

unread,
Jun 30, 2001, 10:44:54 PM6/30/01
to
In article <20010630203529...@ng-mm1.aol.com>, Jon Isaacs
<joni...@aol.com> wrote:

> The purpose of comparing the tone to that of a guitar is determine the
> frequency of the resonance of the spoke and from that determine the tension.
> The sound of the plucked spoke is certainly highly damped but I was surprised
> at how easy it was to compare the fundemental tone to that of a guitar.

The basic principle is of course the same, that of a vibrating wire
under tension. On a guitar the closest approximation would be a bare
steel string (B or high E on an acoustic). A wrapped string carries
the tension on the steel wire core, but the wrapping (which is there
primarily to add mass, as far as I can tell) changes the overtone
characteristics quite a bit.

Musical instruments are also designed to enhance the fundamental and
the desireable overtones and to damp the undesireable overtones. The
"speaking length" of the string remains close to constant as the string
vibrates between the nut (or fret) and the saddle, whereas a spoke has
a more vague termination at either end- the bent elbow in the flange
hole and the threaded end in the spoke nipple- and the speaking or
tonal length of the spoke may vary as the spoke vibrates. I'm
speculating here and may well be way off base.

> The question of free length is important. My test was to pinch the spokes at
> their major crossing and listen to the effect. It is clear that the tone is
> raised by the appropriate amount and so that the effective free length is
> approximately the distance from the nipple to hub.

That's really interesting to me and I'll have to try it on some of my
wheels. I had assumed that the major crossing, which involves pretty
firm contact, would have the effect of "fretting" the spoke and that
the free or tonal length of the spoke would be from the nipple to the
major crossing. Got an explanation for this? Is it that touching the
spokes damps the portion of the spoke between the major crossing and
the hub flange and thus changes the relationships between the
overtones? I'm thinking that it's like damping or not behind a slide.

Jon Isaacs

unread,
Jul 1, 2001, 8:52:24 AM7/1/01
to
>That's really interesting to me and I'll have to try it on some of my
>wheels. I had assumed that the major crossing, which involves pretty
>firm contact, would have the effect of "fretting" the spoke and that
>the free or tonal length of the spoke would be from the nipple to the
>major crossing. Got an explanation for this? Is it that touching the
>spokes damps the portion of the spoke between the major crossing and
>the hub flange and thus changes the relationships between the
>overtones? I'm thinking that it's like damping or not behind a slide.
>
>

While a spoke crossing does make a good connection, the spoke is free to
vibrate in the other plane at its full length. A spoke is not a high Q system
so my guess is that vibrates the whole thing.

jon isaacs

Jobst Brandt

unread,
Jul 1, 2001, 9:56:09 PM7/1/01
to
Jon Isaacs writes:

>> All steels have the same modulus of elasticity, regardless of alloy
>> or heat treatment.

> For normal purposes this is true but I have measured steels that
> range from about 27 Msi to around 32 Msi.

So? That doesn't change the assessment of resonance of a taught wire
and that is what is under discussion.

>> As to detecting absolute tension by tone, this is an illusion
>> because the resonant frequency depends on density (solid steel)
>> which is different from guitar strings, and free length, something
>> that most bicycle spokes do not have because they contact another
>> spoke at partial span and the two spokes do not resonate at the
>> same frequency to produce multiple harmonics that are only
>> reasonably separable by a frequency analyzer.

> I was skeptical about this and still am, however...

Well stop guessing and do it. I've done this and investigated all
these old wive's tales before going to press with "the Bicycle Wheel".

> The purpose of comparing the tone to that of a guitar is determine
> the frequency of the resonance of the spoke and from that determine
> the tension. The sound of the plucked spoke is certainly highly
> damped but I was surprised at how easy it was to compare the
> fundemental tone to that of a guitar. It may be that my ear is
> better than the typical bicycle mechanics as I have been playing
> musical instruments for nearly 40 years. It is also possible that
> this tone is not the fundemental tone.

So now we have the frequency, and what are you going to do with it,
not knowing, for instance what the free length is or how much of a
swaged spoke affects this resonance, or what the frequency of the
crossed spoke is. Assuming you can decipher all that, you must solve
the equation for tension of a solid steel wire knowing it's frequency,
active length, resonance of its neighbor and spoke cross section.
That's a can of worms as I see it because that was my first attempt
to quantify spoke tension without a tensiometer. It was a miserable
failure and we have the instruments to do it here in the lab.

> The question of free length is important. My test was to pinch the
> spokes at their major crossing and listen to the effect. It is
> clear that the tone is raised by the appropriate amount and so that
> the effective free length is approximately the distance from the
> nipple to hub.

If you have your fingers on the spoke, then I don't see how you are
going to get a clean resonance. You are probably getting what I
advise, a higher harmonic by plucking near the nipple. This gets rid
of the crossed spoke problem and is a good comparison for balancing
tension, but it doesn't work for absolute tension.

> A radially laced wheel will also provide an opportunity to have a
> relatively unambigious free length.

Yes, but then most wheels are not and the 16/12 spoke wheels are no
problem, you can't work on them anyway. You can only send them back
to the factory or a bike shop that has the special fixtures to adjust
spokes.

>> This has been done and found ineffective.

> Some of the rough calculations I have done seem to result in spoke
> tensions that are much lower than I would expect. I am interested
> in doing some similar tests when the actual load is known.

> I suspect my model is poor.

> I would be interested in knowing numbers for actual spoke tensions.

I think there are plenty of those around but then it varies with
number of spokes and what the rim will bear.

Jobst Brandt <jbr...@hpl.hp.com>

Jobst Brandt

unread,
Jul 1, 2001, 9:59:33 PM7/1/01
to
Jon Isaacs writes:

> While a spoke crossing does make a good connection, the spoke is
> free to vibrate in the other plane at its full length. A spoke is
> not a high Q system so my guess is that vibrates the whole thing.

Not so. The spoke crossing easily welds and in most used wheels, has
a definite micro notch that is noticeable when the spokes are
displaced from their home position in the plane of the wheel. Even a
new spoke will not move this joint in a rubbing mode or there would
quickly be no vibration from the energy dissipated there.

Jobst Brandt <jbr...@hpl.hp.com>

and...@thankstomycranks.com

unread,
Jul 2, 2001, 5:04:13 AM7/2/01
to

Jobst Brandt <jbr...@hpl.hp.com> wrote in message
news:9hokbp$624$5...@hplms2.hpl.hp.com...

> >> All steels have the same modulus of elasticity, regardless of alloy
> >> or heat treatment.
>
> > For normal purposes this is true but I have measured steels that
> > range from about 27 Msi to around 32 Msi.
>
> So? That doesn't change the assessment of resonance of a taught wire
> and that is what is under discussion.

What are the repercussions for frame tubes though?
Has the frame-tubing counter-myth been busted here?

> >> As to detecting absolute tension by tone, this is an illusion
> >> because the resonant frequency depends on density (solid steel)
> >> which is different from guitar strings, and free length, something
> >> that most bicycle spokes do not have because they contact another
> >> spoke at partial span and the two spokes do not resonate at the
> >> same frequency to produce multiple harmonics that are only
> >> reasonably separable by a frequency analyzer.


You can get a nice note out of a spoke if you allow it
to ring over it's full length. On a 3X wheel this can be done by pushing or
pulling the crossing spoke off of it with the non-pick hand. Whether this
process will seriously affect the tension, I leave the experts to decide. If
not, a table of experimentally determined values for frequency at a given
length would do the trick, no?

More importantly, can we not deduce another characteristic of the typical
rbt contributor from this discussion? Not only is he large, but he probably
plays guitar.

Andrew, had a lesson in pinch harmonics from John Scofield, Bradley
www.thankstomycranks.com


Jon Isaacs

unread,
Jul 2, 2001, 9:28:07 AM7/2/01
to
>Not so. The spoke crossing easily welds and in most used wheels, has
>a definite micro notch that is noticeable when the spokes are
>displaced from their home position in the plane of the wheel. Even a
>new spoke will not move this joint in a rubbing mode or there would
>quickly be no vibration from the energy dissipated there.
>

I only am reporting the results of my plucking the spokes on several wheels.
When I pinch the spokes at the crossing point, the tone does indeed seem to be
raised an amount appropriate. If the crossings were acting as you state, then
there should be no change in pitch when the spokes are pinched at the
crossings.

It may be that these wheels have insufficient tension or that there is some
other factor at work.

jon isaacs

Jon Isaacs

unread,
Jul 2, 2001, 9:48:56 AM7/2/01
to
>So now we have the frequency, and what are you going to do with it,
>not knowing, for instance what the free length is or how much of a
>swaged spoke affects this resonance, or what the frequency of the
>crossed spoke is. Assuming you can decipher all that, you must solve
>the equation for tension of a solid steel wire knowing it's frequency,
>active length, resonance of its neighbor and spoke cross section.

>That's a can of worms as I see it because that was my first attempt
>to quantify spoke tension without a tensiometer. It was a miserable
>failure and we have the instruments to do it here in the lab.

I am interested the results of your experiments. I believe the place to start
is the simplest case, a spoke under uniform tension, I would do this
experimentally rather than analytically.

My first thought is to put a spoke in an MTS machine with some simple end
conditions, then pluck the spoke and record the waveform using a digital
O-scope. I could then have a series of wave forms that would correspond to a
series of loads.

The easiest way to record the waveform would be to use a non stainless spoke
and use a magnetic pick up, either a standard guitar pickup or one of Electro's
basic sensors.

This would provide a starting place to do further work. The issue of free
length could also be resolved experimentally.

>If you have your fingers on the spoke, then I don't see how you are
>going to get a clean resonance. You are probably getting what I
>advise, a higher harmonic by plucking near the nipple. This gets rid
>of the crossed spoke problem and is a good comparison for balancing
>tension, but it doesn't work for absolute tension.

I don't think one is likely to get a clean resonance in any case, plucking a
radial laced wheel does not give a clearer tone. Pinching the crossed spoke is
similar to stopping the string of a non-fretted instrument. A violin has no
frets and this does not seem to be a problem.

>> A radially laced wheel will also provide an opportunity to have a
>> relatively unambigious free length.
>
>Yes, but then most wheels are not and the 16/12 spoke wheels are no
>problem, you can't work on them anyway. You can only send them back
>to the factory or a bike shop that has the special fixtures to adjust
>spokes.
>

Actually I am only suggesting that a radial laced wheel provides a starting
point for an investigation. A simpler case to begin with.

Anyway, enough of my blather, now I need to see if I actually have the energy
to make some of these measurements I have suggested.

Jon Isaacs

Jobst Brandt

unread,
Jul 2, 2001, 11:11:28 AM7/2/01
to
Jon Isaacs writes:

>> That's a can of worms as I see it because that was my first attempt
>> to quantify spoke tension without a tensiometer. It was a
>> miserable failure and we have the instruments to do it here in the
>> lab.

I got inconsistent results and the spectrum had many harmonics with a
standard cross laced wheel.

> I am interested the results of your experiments. I believe the
> place to start is the simplest case, a spoke under uniform tension,
> I would do this experimentally rather than analytically.

> My first thought is to put a spoke in an MTS machine with some
> simple end conditions, then pluck the spoke and record the waveform
> using a digital O-scope. I could then have a series of wave forms
> that would correspond to a series of loads.

I take it you doubt the equations for resonating taught wires or you
wouldn't want to do this experiment. Trust the reference books, they
have it right. Whether the method has value for bicycles or not
should be evident from the absence of any such instrument in the
bicycle industry, anywhere. These are the questions that should come
to mind and from them one can deduce that there are good reasons for
not using the method, either that or the rest of world is stupid.

Jobst Brandt <jbr...@hpl.hp.com>

John Red-Horse

unread,
Jul 2, 2001, 3:31:04 PM7/2/01
to
In article <9hlf7h$fcm$3...@hplms2.hpl.hp.com>, jbr...@hpl.hp.com wrote:
>
>All steels have the same modulus of elasticity, regardless of alloy or
>heat treatment. Their only difference lies in damping as we know from
>the high pitch tone of drill steel compared to a nail of the same
>cross section.
>

While the damping values may well be different among the different steel
alloys, there are some other critical differences between them: (1) The
elastic strength (or yield limit); (2) The ultimate strength; and (3) The
endurance limit.

At least two of these characteristics would seem to be relevant to a
structure as complicated as a bicycle.

john

Jon Isaacs

unread,
Jul 2, 2001, 4:11:27 PM7/2/01
to
>I take it you doubt the equations for resonating taught wires or you
>wouldn't want to do this experiment. Trust the reference books, they
>have it right.

I actually have not looked past the simple solution for a vibrating string. A
spoke has an L/D of about 150 which seems quite high but I also wonder about
the effect of the bending stiffness on the resonance.


> Whether the method has value for bicycles or not
>should be evident from the absence of any such instrument in the
>bicycle industry, anywhere. These are the questions that should come
>to mind and from them one can deduce that there are good reasons for
>not using the method, either that or the rest of world is stupid.

Actually these questions do come to mind but actually the questions which are
more of interest are actually just doing a few simple tests and establishing an
understanding of the basics for myself. Getting my feet wet.

Since I have the equipment necessary for such measurements, something I doubt
many cyclist have, it seems like something interesting to investigate.

The motivation behind such investigations is only to clarify this stuff in my
own mind. I am not in the business of making items for bicycle shops. Rather
I am curious as to some of the inconsistancies between the tones I seem to hear
and the tones I calculate using simple math and simple tension assumptions.

In such investigations is often instructive to start with the simplest
situation, ie a spoke under known tension with proper end conditions and then
once one understand this situation, then variables can be added and hopefully
understood.

Jon Isaacs

Jobst Brandt

unread,
Jul 2, 2001, 4:30:07 PM7/2/01
to
John Red-Horse writes:

>> All steels have the same modulus of elasticity, regardless of alloy
>> or heat treatment. Their only difference lies in damping as we
>> know from the high pitch tone of drill steel compared to a nail of
>> the same cross section.


> While the damping values may well be different among the different
> steel alloys, there are some other critical differences between
> them: (1) The elastic strength (or yield limit); (2) The ultimate
> strength; and (3) The endurance limit.

"may" but they aren't. The art of making spoke wire is well enough
advanced that all spokes worth using have little spread in these
characteristics. The damping value of these spokes of the taught wire
harmonic frequencies is essentially zero, the frequencies in question
being too close to static. As I said, the high pitched "klink" of
drill steel compared to a similar sized nail is close to the audible
limit for most people. The resonating taught spoke is in mid vocal
range.

> At least two of these characteristics would seem to be relevant to a
> structure as complicated as a bicycle.

They may and may seem to but don't, but thanks for guessing.

Jobst Brandt <jbr...@hpl.hp.com>

Tom Morley

unread,
Jul 2, 2001, 5:08:09 PM7/2/01
to
In article <20010702161127...@ng-mq1.aol.com>,
joni...@aol.com (Jon Isaacs) wrote:

> >I take it you doubt the equations for resonating taught wires or you
> >wouldn't want to do this experiment. Trust the reference books, they
> >have it right.
>
> I actually have not looked past the simple solution for a vibrating
string. A
> spoke has an L/D of about 150 which seems quite high but I also wonder about
> the effect of the bending stiffness on the resonance.
>

> Jon Isaacs


The case of a thick vibrating string comes up in piano tuning,
and is handled as a pertubation of the wave equation.
In terms of pianos what happens is the the harmonics are
all slightly sharp [1]. See "Physics of Musical Instuments,
second ed." published by Springer Verlag.

[1] Thus the octaves on a piano are tuned wide.

--
Tom Morley |
mor...@math.gatech.edu | Same roads,
tmo...@bmtc.mindspring.com | Same rights,
http://www.math.gatech.edu/~morley | Same rules.
ICQ: 24798603 AIM: DocTDM |

Jeffrey L. Bell

unread,
Jul 3, 2001, 1:55:01 PM7/3/01
to
Tim McNamara <tim...@bitstream.net> wrote:
>...

>You'd need an acoustic chromatic tuner rather than one designed only to
>measure EADGBE. The other problem is that the spoke doesn't sustain
>the tone long enough for the tuner to analyze the frequency....

I think you missed what I was saying.

Use the tuner to tune the guitar. Even a tuning fork is good enough
for this. Then use the guitar to judge the pitch of the spoke.
The tricky part will be finding a guitar that you don't mind playing with
bike grease on your hands.

For that matter you could practice up on your perfect pitch, or learn
some relative pitch skills with a known pitch such as a telephone
dialtone (A and F), "Shine On You Crazy Diamond" on autorepreat (G),
or cheap flourescent light fixtures (120 Hz in N.America)

-Jeff Bell

(I once took a class in the music department at an
engineering school. By then end of the first class the
instructor had put wave equations on the board.)

Tim McNamara

unread,
Jul 4, 2001, 12:35:08 AM7/4/01
to
In article <9ht0tl$o17$1...@news.eecs.umich.edu>, Jeffrey L. Bell
<jlb...@agitato.eecs.umich.edu> wrote:

> Tim McNamara <tim...@bitstream.net> wrote:
> >...
> >You'd need an acoustic chromatic tuner rather than one designed only to
> >measure EADGBE. The other problem is that the spoke doesn't sustain
> >the tone long enough for the tuner to analyze the frequency....
>
> I think you missed what I was saying.
>
> Use the tuner to tune the guitar. Even a tuning fork is good enough
> for this. Then use the guitar to judge the pitch of the spoke.
> The tricky part will be finding a guitar that you don't mind playing with
> bike grease on your hands.

It would be a pretty filthy bicycle that would get grease on your hands
from plucking a spoke. Mine are marginally cleaner than that,
fortunately.

> For that matter you could practice up on your perfect pitch, or learn
> some relative pitch skills with a known pitch such as a telephone
> dialtone (A and F), "Shine On You Crazy Diamond" on autorepreat (G),
> or cheap flourescent light fixtures (120 Hz in N.America)

I don't think I missed your point. Besides, IIRC, my comment was in
response to Jon Isaacs talking about using a Korg chromatic tuner to
measure the spoke's pitch directly rather than comparing the pitch to a
guitar string.

Having been a guitarist for nearly 25 years my sense of pitch is pretty
good (even if I do sing like Jerry Garcia on a bad night).

The problem with the model you propose is that the tone and pitch of a
guitar string is very clearly defined thanks to the clean termination
of the string at the nut and saddle, and the damping of the portion of
the string beyond the nut and saddle. When a string is fretted, the
finger doing the fretting damps the portion of the string between the
fret and the nut. The end result is a clear and, as far as pitch is
concerned, definitive tone. The amplitude of the fundamental is much
greater than the amplitude of the overtones- which is why a plucked
string is louder than playing harmonics if the force of plucking is the
same (guys like Lenny Breau and Tal Farlow learned to compensate for
this very effectively when throwing harmonics and false harmonics into
their lines).

A bicycle spoke is a different animal. At one end it is bent and
hooked through a hole an aluminum that is slightly larger, so the
inside of the elbow and the head of the spoke is in contact with the
flange. This is a large and rather vague contact area, unlike the
clean termination of the nut and saddle, being a bi-curved surface
resting on another bi-curved surface. About 1/3 of the way from the
spoke head to the nipple, the spoke is crossed, essentially fretted, by
another spoke *but* it is not damped behind the crossing except by
friction at the contact. At the far end, the spoke is threaded and
terminates in a threaded nipple which may not be in perfect alignment
with the spoke. The lip of the nipple might be in contact with the
shaft of the spoke and it may not. In addition, the diameter of the
spoke may vary by more than 10% if it is a swaged spoke, which further
complicates the tone. Guitar strings are drawn through a die to be a
constant diameter; wrapped strings are also drawn through die so that
the cores and the wrappings are of constant diameter.

When you pluck a guitar string, you are actuating a vibrating wire that
is cleanly terminated at either end and damped effectively for the
portions beyond the terminations, so that only the "speaking length" of
the string produces sound. There is a series of harmonic overtones in
addition to the fundamental, but the guitar is designed to selectively
damp the unpleasant overtones and to enhance the pleasant ones.

When you pluck a bicycle spoke, you are actuating a vibrating wire that
is poorly terminated and fretted without damping about 1/4 to 1/3 along
its length. The fundamental is overwhelmed by the harmonic overtones,
and the structure of the wheel is not designed to selectively damp
those overtones. Wood damps the string vibrations very effectively,
but the metal rim and hub do not. The reason the tone decays so
rapidly is the lack of clean termination at the ends of the spoke.

It's much like playing a square neck Dobro or a Weissenborn with a bar
and not damping behind the bar. The results are ugly. You can compare
the tone of the spoke to a guitar string, you can probably reasonably
approximate the pitch, but what does that tell you? You already know
the relative relationship- a higher pitch means greater tension, a
lower pitch the opposite. You might decide that you think that your
optimal spoke tension is A# above middle C, but that tells you nothing
about the actual tension (without a whole lot of complicated math,
anyway).

There are too many confounds to be able to use pitch in an absolute
manner for dtermining spoke tension. As Jobst has mentioned, this has
already been tested with a whole lot of high-grade lab equipment and
found to be non-useful.

John Red-Horse

unread,
Jul 5, 2001, 7:24:28 PM7/5/01
to
In article <9hqlkf$9g0$3...@hplms2.hpl.hp.com>, jbr...@hpl.hp.com wrote:

>John Red-Horse writes:
>
>> While the damping values may well be different among the different
>> steel alloys, there are some other critical differences between
>> them: (1) The elastic strength (or yield limit); (2) The ultimate
>> strength; and (3) The endurance limit.
>
>"may" but they aren't. The art of making spoke wire is well enough
>advanced that all spokes worth using have little spread in these
>characteristics.

Wait a second: Are you saying that somehow fundamental differences in
material properties are being reduced due to spoke wire manufacturing? Or,
are you saying that candidates for use as spoke wire limit the scope of
useful alloys sufficiently that the material properties, and, really the
metals themselves, then have only very small differences?

>The damping value of these spokes of the taught wire
>harmonic frequencies is essentially zero, the frequencies in question
>being too close to static. As I said, the high pitched "klink" of
>drill steel compared to a similar sized nail is close to the audible
>limit for most people. The resonating taught spoke is in mid vocal
>range.
>

Actually, you wrote, as you always do, in such an obtuse manner that
figuring out your point on the damping issue was difficult to do.

The statement ``frequencies [...] being close to static'' makes me want to
laugh. Nice job. Here's your challenge for the day: Go back and review
your structural dynamics textbook (I know that this'll be easy since it's
probably on your desk open to some critical passage right now), find a
reference to static natural frequencies, and get back to us that specific
references. Only then will I stop laughing, and stop avoiding your
annoying engineering-esque explanations to physical phenomena.

Let's agree that there is, essentially, no difference in the damped and
undamped natural frequencies for a given configuration between the
different steel alloys, and that this owes to the fact that the damping
values are so small for all of them.

>> At least two of these characteristics would seem to be relevant to a
>> structure as complicated as a bicycle.
>
>They may and may seem to but don't, but thanks for guessing.
>

Oh, the various material properties, other than damping of course,
probably were relevant at some time or other. Given the (apparently)
cyclical nature of the bicycle components manufacturing business, why do
you think that they won't be relevant again?

john

Jon Isaacs

unread,
Jul 6, 2001, 9:57:20 AM7/6/01
to
>The statement ``frequencies [...] being close to static'' makes me want to
>laugh.

Static simply means the frequency is equal to zero.

The point is that spokes vibrate at low frequencies, hundreds of Hz rather than
millions of Hz.

Jon Isaacs

Bikefixr

unread,
Jul 8, 2001, 5:41:31 PM7/8/01
to
I've used all three plus one not avail in the states. My opinion is that they
are about worthless. The different styles all yield vastly differing results
on the same wheel. What they might be good for is that you , as an
inexperienced bewannabe builder, haven't yet developed "feel" for the wheel.
The gauge might be helpful in getting the spokes uniformly tensioned-even if
the absolute tension is a big question mark. Eveness is more important than the
absolute #. You can accomplish the same thing with a nice pluck of the spokes.
The ear is amazingly acurate-and you can quickly find spokes that are high or
low. I sold all mine off and haven;t missed them once.
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