Spoke Tensiometers?
Tim Barnes
I've never seen one, and was wondering how they work. My guess is that
they displace the spoke a fixed distance and measure the force required
for the fixed displacemant, or vice versa. Anyone care to enlighten me?
cheers, Tim.
Jim Papadopoulos
how it might be different. The normal units employ a
spring, which would displace the spoke a fixed distance
IF IT DIDN'T SHORTEN. The shortening depends on both spring
stiffness and spoke tension-induced stiffness, and in practice
the mfrs just calibrate them.
Note that spoke centerline
displacement depends on it s thickness (gauge).
JP
Jobst Brandt
> I've never seen one, and was wondering how they work. My guess is that
> they displace the spoke a fixed distance and measure the force required
> for the fixed displacement, or vice versa. Anyone care to enlighten me?
An infinitely flexible filament displaced as one would a bowstring to
shoot an arrow enables the tension to be determined on the basis of
the angle of the filament and the applied force. Because there were
no tensiometers available when I was writing my book on wheels, I
designed and built one specifically for bicycle spokes.
Avocet now produces that instrument and has calibrated them to be
accurately repeatable among all units, something that I did not do for
the few that I built. The assembly drawing appears as one of the
figures in my book. The main features that are different from others
on the market are that it uses a light load so that the spoke is not
additionally tensioned by the measurement. The spoke is supported
from the same side from which the measurement is made, thereby
eliminating spoke thickness from the measurement. The spoke is
supported on two ball bearings four inches apart so that friction does
not impede deflection by spring force. The measurement is made by a
0-1mm dial micrometer with 1/100mm resolution. It uses a calibrated
spring force. The gauge reads in mm but a graph supplied can be used
to convert the readings to Newtons or pounds force. Most
wheelbuilders will most likely note the appropriate displacement value
in their notebook for each specific wheel design and leave the
conversion to force units for the lawyers who might question their
judgment.
Jobst Brandt <jbr...@hplabs.hp.com>
Jeff Orum
> Avocet now produces that instrument
So is this available to the general public? What is the approximate
cost of the unit?
Jeff Orum
or...@cup.hp.com
Jobst Brandt
> So is this available to the general public? What is the approximate
> cost of the unit [tensiometer]?
It is slightly less than the Hozan at ~$250.
Jobst Brandt <jbr...@hplabs.hp.com>
Robert Tisot
Tim Barnes <barnest@holly> writes:
>I've never seen one, and was wondering how they work. My guess is that
>they displace the spoke a fixed distance and measure the force required
>for the fixed displacemant, or vice versa. Anyone care to enlighten me?
I used one in some wheel building classes given by a local shop. They cost
about $80 and are available from Performanace. Basically, it measured the
tension by clipping to 2 spokes with the spring and gauge between.
Warning: This type of tool only works for straight spokes! It will give
an abnormally low reading for a 'double-butted' spoke. Beware before
ordering!!!!!
----
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Robert Tisot _-\_<, / Student Financial Services |
Systems Analyst ,___o (*)/'(*) <200 Franklin Building / 6270 |
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* Cycling compatibility is the key to a successful and happy marriage *
John - Forester
very simple construction and much cheaper than the more complex kind
described by Jobst. I own one, and I have found it to give reasonably
repeatable measurements when retested on individual spokes. It comes
with a calibration chart that I rely on. Presumably, I could tension
spokes of varying diameter with a variety of weights and recalibrate it
myself, but I have not done so. I presume that this type of instrument
is entirely adequate for the typical wheel builder.
JFor...@cup.portal.com John Forester
726 Madrone Ave
408-734-9426 Sunnyvale CA 94086 USA
David Mackintosh
>I used one in some wheel building classes given by a local shop. They cost
>about $80 and are available from Performanace. Basically, it measured the
>tension by clipping to 2 spokes with the spring and gauge between.
This would give the average tension of the two spokes, not the tension in a
single spoke. Also, the reading would still depend on spoke length,
thickness, and the angle between the two spokes being squeezed by the device
(and maybe even rim stiffness). Are you sure this is how it works?
>Warning: This type of tool only works for straight spokes! It will give
>an abnormally low reading for a 'double-butted' spoke. Beware before
>ordering!!!!!
In any case the reading would be different for various spoke thicknesses and
some sort of calibration table would be required, unless bending stiffness is
ignored.
David Mackintosh Germantown, MD DoD #1360
mack...@oasys.dt.navy.mil '92 Santana Sovereign '89 Hawk GT
Edward Caldeira
and effective method... Under the premise that like tensioned spokes have like
tones when plucked in the manner of a guitar, he adjusts the tension until is
round and all the spokes sound alike.
He may not know the pounds of tension, but they are evenly tensioned. All I
know is that I am 195 pounds and been racing every weekend on those wheels for
the last 2 years. And that's music to my ears!
And now a plug for Tony Nennan, musician and wheel builder of Baltimore.
J. Lee
In a previous article, ecal...@delphi.com (Edward Caldeira) says:
>My wheelbuilder is also a musician and he uses his musical skills in a unique
>and effective method... Under the premise that like tensioned spokes have like
>tones when plucked in the manner of a guitar, he adjusts the tension until is
>round and all the spokes sound alike.
>
>He may not know the pounds of tension, but they are evenly tensioned.
I use the same technique, except that I DO use a Wheelsmith
tensiometer to give all of the spokes a final check-- if one
isn't totally tone-deaf, then only very slight adjustments will
be required at that stage of final truing.
--
"If the theory produces nonsensical answers that disagree with
physical data, then it must be discarded, no matter how elegant
its mathematics."
--Michio Kaku
Otto-Ville Ronkainen
>My wheelbuilder is also a musician and he uses his musical skills in a unique
>and effective method... Under the premise that like tensioned spokes have like
>tones when plucked in the manner of a guitar, he adjusts the tension until is
>round and all the spokes sound alike.
It ain't unique. I've done so for years. It's just that the interval
of the spoke tones is usually quite large within 1/4 turn of a nipple.
--
Ott-Vill R______________________ / Wo ein Wille ist, ist auch ein Weg.
o...@snakemail.hut.fi / Missä Wille on, on myös tie.
Dara Parsavand
Edward Caldeira <ecal...@delphi.com> wrote:
>My wheelbuilder is also a musician and he uses his musical skills in a unique
>and effective method... Under the premise that like tensioned spokes have like
>tones when plucked in the manner of a guitar, he adjusts the tension until is
>round and all the spokes sound alike.
has anyone used a digital tuner (say for a guitar), to do the same thing.
a computer with a microphone should be able to do a plot of all the spoke
tensions also. has this been done?
dara parsavand the most important technical development for
pars...@prony.colorado.edu (road) bikes will be the electric (or hybrid) car
Joshua Winsor
First of all Jobst Brandt documents tonal tensioning of wheels in his book
_The_Bicycle_Wheel_ quite extensively. He goes so far as to claim that it
is one of the easiest and most accurate methods without the use of special
tools, such as a tensionometer. He does however suggest the use of a
tensionometer.
An electronic tuner is far too sensitive to use in this application. A
quarter turn changes the pitch quite a bit. Also once you get the tension
even by tones, the wheel is not exactly true, and thus needs to be fine
tuned on a truing stand. you can't get the perfect pitch method due to the
fact that the rim, spokes, nipples, and hubs are far from perfect.
-Joshua
Dara Parsavand
Joshua Winsor <jwnr...@uhura.cc.rochester.edu> wrote:
>An electronic tuner is far too sensitive to use in this application. A
>quarter turn changes the pitch quite a bit. Also once you get the tension
>even by tones, the wheel is not exactly true, and thus needs to be fine
>tuned on a truing stand. you can't get the perfect pitch method due to the
>fact that the rim, spokes, nipples, and hubs are far from perfect.
if a normal guitar tuner is TOO sensitive, then doesn't it seem like a
cheaper (less sensitive) electronic device than a mechanical tension
device can be made? i can understand that the interlacing will affect
the tone, but of course that affect is equal for each spoke for lacing
patterns i use. i'm not sure i agree with you that TOO sensitive an
instrument is EVER a problem, so long as it has the desired range (the
only type of guitar tuner (about $20) i know of covers the entire range
of the guitar [i.e. you tune each string separately with the tuner]).
would you say that you wouldn't want a digital scale that measured
1-100kg +/- .001kg, but would prefer one 1-100kg +/- .1kg? (assuming
they are the same price)
btw, i have read Jobst's book, though it has been a while, and i
don't remember electronic measurement of tone being in there, which is
why i chose to post. the next wheel i build, i'll try my friend's tuner
and post my results.
Jobst Brandt
> Has anyone used a digital tuner (say for a guitar), to do the same thing.
> A computer with a microphone should be able to do a plot of all the spoke
> tensions also. Has this been done?
The frequency of a plucked spoke depends on its cross sectional
diameter, its length, its tension and the adjacent spoke and where it
intersects this spoke. Interleaved spokes, therefore, have a complex
tone that has multiple modes, the primary mode not containing the most
energy but rather a mode that resonates in the free span of the spoke.
Seen on an oscilloscope, the spectrum is dirty and not repeatable.
Using tone by exciting the higher modes of the spoke is useful for
balancing tension but practically useless to gauge absolute tension.
By plucking spokes near the nipple, the higher modes are excited which
largely avoids the problem of interleaved spokes. The musically adept
human ear readily recognizes the "quality" of the tone that is
otherwise difficult to define analytically.
Jobst Brandt <jbr...@hplabs.hp.com>