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Tensiometer

Old 01-22-12, 12:51 PM
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Originally Posted by p2templin
Is there truly any need to consult the chart even once? If the spokes are all the same gauge and they're all the same deflection, they're the same tension, right?
Yes, if that's your only reason to use a tension meter.

I don't use it for that since I use an old school methodology that ensures even tension from the beginning of the process. For decades I built good even tensioned wheels without the need for a gadget.

However, today, with so many rim weights, using different gauge spokes, in various lacings, I can no longer trust my fingers to stay properly calibrated so I use a tension gauge to check the work. On a typical built I'll check the tension on 2-4 spokes as I come to final tension just to be sure I'm where I want to be. However for 32h 3x builds with tubular rims, I can still come to within 10% of target using my calibrated fingers.
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Old 01-22-12, 01:13 PM
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Originally Posted by JohnDThompson
When I was at Trek, one of my duties was to keep the tensiometers calibrated for the wheel building department. We made a special test bed with a strain gauge to put a known amount of tension on a spoke and used that to calibrate the tensiometers. My lasting impression is an abiding dismay at how quickly tensiometers go out of calibration. When this duty threatened to become my full-time job, I was glad to pass it on to someone else.
This situation illustrates the problem of what happens when too much is expected of any measuring device. Going back to the separation of accuracy, repeatability and resolution below and consider what happens when the resolution is more precise than the accuracy or repeatability.

Originally Posted by Staggerwing
...

In the engineering/science world:
Accuracy: How close to the actual value (as per your note)
Precision: Spread over multiple measurements (ie repeatability)
Resolution: Smallest change which may be detected (not precision)
Without good repeatability you can find yourself recalibrating the device forever even though each reading is accurate to the ability of the unit. Then add the natural variation in what your measuring, and you never know if the deviation is in what you're measuring or in the instrument itself. It's like using a watch precisely set, and with a sweep second hand to catch a bus which may come 2 minutes early of 5 minutes late.

Tension meters,for a number of reasons only are accurate to a range, ie. ±5%, and having a more precise readout doesn't change that. All it can tell you is that you're within 5% either way of the true tension either way. IMO repeatability is most important. If taking multiple readings, and comparing them, you don't really care if you're off a bit on the actual tension, but you don't want to be misled by the lack or repeatability in the unit, or you could make things worse rather than better.
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Old 01-22-12, 02:05 PM
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Originally Posted by FBinNY
Yes, if that's your only reason to use a tension meter.
I'm still awaiting your explanation of WHY one needs to consult the chart.

If you want even tension, wouldn't you see even deflection? Why would matter WHAT tension you have, as long as the tension was even?
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Old 01-22-12, 02:23 PM
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Originally Posted by p2templin
I'm still awaiting your explanation of WHY one needs to consult the chart.

If you want even tension, wouldn't you see even deflection? Why would matter WHAT tension you have, as long as the tension was even?
Tension matters because a wheel has to be within a range of tension to work properly and last. Too loose and it doesn't tend to hold up well. Too tight and the rims will stress crack, or with light spokes they could be too close to their elastic limits.

Note, That I said a range of tension. That's because IMO absolute tension isn't super critical, and tightest isn't best. Years ago the range of tension was pretty broad, and anybody's fingers could be calibrated accurately enough.

These days however, rear wheels will often have left side tension of about 60% of right side tension. That narrows the working tension to a narrow zone between what will be too loose on the left and too tight on the right, or often both at the same time.

That's where the tension meter is used, to check that the final product is within what I consider the proper tension range. Obviously to do that I need the chart to convert the readings to kpf.

As you and I agree, you don't need a chart if all you're going to do is compare spoke to spoke, and try to match the values for even tension. But I never do that anyway, because I consider it pointless.
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Old 01-22-12, 05:36 PM
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Originally Posted by p2templin
I'm still awaiting your explanation of WHY one needs to consult the chart.

If you want even tension, wouldn't you see even deflection? Why would matter WHAT tension you have, as long as the tension was even?

You are getting a little confused...

1. The tool measures "deflection". That's it - nothing more. All it sees is a deflection for a set distance. [OBSERVATION]

2. The chart provides an estimate of what the "deflection" means as "tension" for a given gauge. [INTERPRETATION]


You can use deflection to judge consistency and relativity - but you need an interpretation to determine if you are anywhere near your tension goal.


Since I work with 14g 99.99% of the time for my inventory wheels, I don't have to hit the chart all the time - I have 23, 24 and 25 stuffed away in memory. I know what they "translate" to.


=8-)
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Old 01-22-12, 05:37 PM
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Who are you all kidding? Most of these will be toys for nerds that love this kind of high precision instruments. The precious tensiometers will be taken out of their boxes for those twice-a-year wheel build sessions, but they're mostly little collectables for display and admiration.

And yes, that's exactly why I have my FSA tensiometer, and why I will be getting that Wheel Fanatyk instrument. The tensiometers can keep each other company amongst the 10+ spoke wrenches and various wheelbuilding nicknacks, including the rare-as-hens'-teeth DT spoke wrenches. Some of us don't want to be saved.
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Old 01-22-12, 09:18 PM
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Originally Posted by FBinNY
IMO absolute tension isn't super critical, and tightest isn't best. Years ago the range of tension was pretty broad, and anybody's fingers could be calibrated accurately enough.

These days however, rear wheels will often have left side tension of about 60% of right side tension. That narrows the working tension to a narrow zone between what will be too loose on the left and too tight on the right, or often both at the same time.
My feeling is that for wheels with 28 or more spokes, a tensiometer is unnecessary (provided you have the experience to give you "properly calibrated" fingers).
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Old 01-22-12, 09:52 PM
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Originally Posted by byte_speed
I wonder how much we kid ourselves on the accuracy of our Park TM-1 meters and the accompanying chart? The engineer in me wants a calibration device.
If you really want a calibration device, it's not that hard
to set up a spoke with a given weight hanging vertically
from the free end. For our less than mission critical non
NASA purposes, it works well enough.

I almost never recalibrate my own park tensiometer, because
as many have said here, I'm mostly interested in consitancy
of spoke tension in relationship to each other, and I pull everything
up into about the same range as Mr. Bunny ( I also use mostly
straight 14g spokes because they are easy to work with and
cheaper than the DB ones.) Pretty sure I could do so if I wanted
to though.

I actually find the thing a lot more useful for truing and retensioning
a wheel that comes to me history unknown and requiring some
tweaking. The ability to quickly run the whole wheel and see what's
high, what's low, and where they sit in relation to each other....
with a simple analog readout.....just sets my heart aflutter.
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Old 01-22-12, 09:52 PM
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Originally Posted by JohnDThompson
My feeling is that for wheels with 28 or more spokes, a tensiometer is unnecessary (provided you have the experience to give you "properly calibrated" fingers).
I agree, and built wheels for about 40 years without.

However, nowadays I don't build enough wheels to maintain my finger calibration, and each is so different in terms of rim and spoke combination. So I use a tension meter as a reality check, or to give me better confidence that I'm where I want to be, especially on high dish rear wheels.

Probably the real reason for owning a tension meter, has nothing to do with the wheel itself. These days everyone wants numbers, spoke tension, torque specs, precise tire pressures, you name it. You have to own these gadgets, even if you don't need or use them, just to stay even in the BS battles.
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Old 01-22-12, 10:13 PM
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Originally Posted by 3alarmer
If you really want a calibration device, it's not that hard
to set up a spoke with a given weight hanging vertically
from the free end. For our less than mission critical non
NASA purposes, it works well enough..
What do you mean "works well enough" there's no more accurate way to calibrate a tension meter than with a dead weight on the end of a spoke. It's a precisely known tension, with built in compensation for the stiffness of the spokes to be measured.

The only thing you could do to make it better, is to use 2 weights on either side of the target tension range, ie. 100kg and 125kg.
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Old 01-22-12, 10:39 PM
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Originally Posted by FBinNY
What do you mean "works well enough" there's no more accurate way to calibrate a tension meter than with a dead weight on the end of a spoke. It's a precisely known tension, with built in compensation for the stiffness of the spokes to be measured.

The only thing you could do to make it better, is to use 2 weights on either side of the target tension range, ie. 100kg and 125kg.
NASA would use a proprietary $100,000 machine that pulled the thing horizontally
under variable gravitation values and needed monthly maintenance and recalibration
contracts to be put out for bid themselves. I was just apologizing for the directness
and simplicity of the method......given the nature of the original topic.
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Old 01-23-12, 01:58 AM
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Originally Posted by mrrabbit
You are getting a little confused...

1. The tool measures "deflection". That's it - nothing more. All it sees is a deflection for a set distance. [OBSERVATION]

2. The chart provides an estimate of what the "deflection" means as "tension" for a given gauge. [INTERPRETATION]


You can use deflection to judge consistency and relativity - but you need an interpretation to determine if you are anywhere near your tension goal.
That's well said (and what I was trying to say in my earlier post). None of the commericial spoke tensiometers directly measures spoke tension. They apply a known force to bend the spoke between two anchor pins and measure the deflection (in length units). The tension represented by this deflection is related to the amount of deflection, but the deflection itself varies with the spoke material and dimensions, hence the need for conversion tables to translate deflection into tension.

As others have said. measuring instruments are rated as to accuracy, precison, and resolution. Accuracy refers to how close the instrument's "read out" is to the "true" measurement. Precision refers to the instrument's ability to give the same measurement when repeatedly measuring the same object. Resolution refers to the instrument's ability to "read out" in smaller increments, such that a micrometer that reads out in 0.001mm increments is considered to have higher resolution than one that reads in 0.01mm increments. Of these three parameters, accuracy and precision are most important. Resolution is important as well (and most well-made instruments that are accurate and precise). There are plenty of modern measuring instruments that offer "high resolution" thanks to digital technology. However, unless these instruments are mechanically well-made, their high resolution is what we should call "empty" resolution, i.e., they can be neither accurate nor precise.
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Old 01-23-12, 03:37 AM
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Originally Posted by mrrabbit
Accuracy is not the goal - getting a "good" or "reasonable" estimate IS. Read my original post regarding using "fine" to " measure "rough". Once again, we almost never have "perfect" rims and spokes to work with. ...The Park TM-1 seems to do the job quite well ...
I have slightly mixed emotions about the TM-1 when I build wheels where mere usefulness isn't the governing build goal.
Dunno whether to be proud or disappointed that I can get a wheel to where the repeatability of the measurements is the limiting factor regarding spoke tension balance.
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Old 01-23-12, 09:55 AM
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I don't build anywhere near as many wheels as some folks here. I also don't know near as much about building wheels as some of the folks here. I built quite a few wheels before buying a tensiometer. I bought a TM-1. It wasn't the cheap side of me coming out, but I just couldn't see the benefit in spending more. It's only to check what my fingers and ears are telling me. After I realized that the "same tone" in every wheel/spoke combination didn't necessarily produce the same tension- I needed some measuring device to test the work and get closer to the target number (whatever that is.) The TM-1 will tell me what I need to know as well as any other instrument currently available.

What is disturbing are the reports on the need to "recalibrate." I lost my Park instruction sheet but I recall somewhere in there about the cost of sending it back for re-calibration. What? I'm not gonna fiddle with the initial factory settings, and I can't see the spring relaxing enough to throw deflection readings off. To check this occasionally I've built a little fixture with spokes having a known deflection using the TM-1 when it was new. It's simple to test that the tool continues showing the same deflection as originally witnessed.


So... Every tensiometer I see out there uses a spring to "deflect" the spoke. That spring isn't under huge tension at any time, and it doesn't cycle with the frequency that will cause a "weakening" of the spring, so what gives? It should never need recalibration if designed properly. Maybe someone needs to re-think how spoke tensiometers are built.
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Old 01-23-12, 10:09 AM
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I like the Wheel Fanatyk meter. It's better and cheaper than a DT, and half the price of the digital version of the DT.
YOu need to measure tension to build a reliable wheel. back when we had 5 speed wheels, everyone went by feel and we broke a lot of spokes. The margin for error when tensioning a 10 speed wheel is so thin that no one can do it reliably with measuring.
A Park TM-1 is ok for amateur wheel builders, but the Wheel Fanatyk is good enough for quality control even for the best builders. The electronic dial is a little easier to use and cool, but maybe it's also overkill for amateurs.

em

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Old 01-23-12, 10:37 AM
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Originally Posted by eddy m
I like the Wheel Fanatyk meter. It's better and cheaper than a DT, and half the price of the digital version of the DT.
YOu need to measure tension to build a reliable wheel. back when we had 5 speed wheels, everyone went by feel and we broke a lot of spokes. The margin for error when tensioning a 10 speed wheel is so thin that no one can do it reliably with measuring.
A Park TM-1 is ok for amateur wheel builders, but the Wheel Fanatyk is good enough for quality control even for the best builders. The electronic dial is a little easier to use and cool, but maybe it's also overkill for amateurs.

em
The high-end high-cost tensionmeters are flat out overkill on the both the measurement side of things and the cost. Read my earlier post - in general, the material we are using to build wheels are "rough". Maybe not as rough as "rough stock" in the wood working business...

Bringing in those high end tools is like bringing in a metric tape measure to do house framing when the old American standard tape measure is good enough.

But hey, if you want to feel "elite" and have an awesome show piece, go right ahead and buy one...

=8-)
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Old 01-23-12, 10:51 AM
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Originally Posted by eddy m
A Park TM-1 is ok for amateur wheel builders, but the Wheel Fanatyk is good enough for quality control even for the best builders. The electronic dial is a little easier to use and cool, but maybe it's also overkill for amateurs.
Like others you're assuming that the high resolution of the readout implies greater accuracy or precision (repeatability). There's little evidence to support this conclusion. All spoke tension meters rely on the same indirect method of measurement and have similarly limited accuracies and/or precision.

While useful, tension meter readings are subject to error and can only be used based on the level of the accuracy or repeatability of the instrument.
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Old 01-23-12, 10:52 AM
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Originally Posted by reddog3
I don't build anywhere near as many wheels as some folks here. I also don't know near as much about building wheels as some of the folks here. I built quite a few wheels before buying a tensiometer. I bought a TM-1. It wasn't the cheap side of me coming out, but I just couldn't see the benefit in spending more. It's only to check what my fingers and ears are telling me. After I realized that the "same tone" in every wheel/spoke combination didn't necessarily produce the same tension- I needed some measuring device to test the work and get closer to the target number (whatever that is.) The TM-1 will tell me what I need to know as well as any other instrument currently available.

What is disturbing are the reports on the need to "recalibrate." I lost my Park instruction sheet but I recall somewhere in there about the cost of sending it back for re-calibration. What? I'm not gonna fiddle with the initial factory settings, and I can't see the spring relaxing enough to throw deflection readings off. To check this occasionally I've built a little fixture with spokes having a known deflection using the TM-1 when it was new. It's simple to test that the tool continues showing the same deflection as originally witnessed.


So... Every tensiometer I see out there uses a spring to "deflect" the spoke. That spring isn't under huge tension at any time, and it doesn't cycle with the frequency that will cause a "weakening" of the spring, so what gives? It should never need recalibration if designed properly. Maybe someone needs to re-think how spoke tensiometers are built.

ALL measurement tools need calibration. They fall generally into three categories:

A. Those that are static in nature - calibration ONCE up front at production. Rulers, dials, etc...

B. Those that are dynamic in nature and require calibration throughout their lifetime. Spring loaded, displacement sensitive, balance beam sensitive. Tensionmeters, scales, etc...

C. Those that are dynamic in nature and require a specified stable input to determine specified output. Oscilliscopes, Time Domain Reflectrometers, etc...

Re-calibration is a normal and expected part of B and C.

You are raising alarm and disturbance where there is none. It is expected...

It just so happens though that spring-loaded measuring tools typically require the most re-calibration...like flexing spokes...the spring goes through changes due to fatigue from use.

=8-)

I have two TM-1s and a calibration wheel. I used the first TM-1 to set up the calibration wheel. I then continued to use the first TM-1 as my regular tensionmeter. I used the second TM-1 to verify the calibration wheel and the first TM-1 concurrently. The second TM-1 is locked away in its box never to be touched again UNLESS I have a reason to suspect that someone has messed around with my calibration wheel.

=8-)
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Old 01-23-12, 12:11 PM
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Originally Posted by FBinNY
Like others you're assuming that the high resolution of the readout implies greater accuracy or precision (repeatability). There's little evidence to support this conclusion. All spoke tension meters rely on the same indirect method of measurement and have similarly limited accuracies and/or precision.

While useful, tension meter readings are subject to error and can only be used based on the level of the accuracy or repeatability of the instrument.
The Park, DT, Hozan and Wheel Fanatyk tensiometers all infer tension in the same way, but that doesn't make them all equal. The WF uses ball bearing posts to eliminate friction and binding, and it's the only one that doesn't add the width of the spoke to the deflection measurement. IT has finer resolution than the Park, but that just means it can use lower test loads. Those things are the difference between something that works adequately, and another that is the best available.
It surprises me that people who like $5000 bicycles and $800 wheelsets object to high quality tools, even if they are more than the home mechanic needs.

em
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Old 01-23-12, 12:38 PM
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What I noticed with most measuring instrucments out there is, stiction within the meter's mechanism and contact points between the instrument and the item being measured can really screw up accuracy/consistency of readings. I've encountered this on both expensive and cheap instruments. I always end up measuring things at least 3 times min. to get a close toconsistent reading, and even then, a 4th measurement might be well off from the first three which forces you to do more measurements just to get a measurement that I could trust is closest to actual. Yes, you can throw money at the problem by buying the most expensive instrument that might not have as much stiction, but you can never really eliminate the problem 100%. I think A tensiometer will just slow my wheelbuilding way down that it's really not worth it as the wheels that I build just using tone and feel have never "asploded" on me yet and they stay true and straight.
JMOs

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Old 01-23-12, 01:07 PM
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Originally Posted by eddy m
The Park, DT, Hozan and Wheel Fanatyk tensiometers all infer tension in the same way, but that doesn't make them all equal. The WF uses ball bearing posts to eliminate friction and binding, and it's the only one that doesn't add the width of the spoke to the deflection measurement. IT has finer resolution than the Park, but that just means it can use lower test loads. Those things are the difference between something that works adequately, and another that is the best available.
It surprises me that people who like $5000 bicycles and $800 wheelsets object to high quality tools, even if they are more than the home mechanic needs.

em
No one objected to them...

We object to the overkill and unnecessary cost that results for a given application and environment...I'll keep my Swiss made pharmaceutical 300g scale thank you...

=8-)
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Old 01-23-12, 01:45 PM
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Originally Posted by mrrabbit
I'll keep my Swiss made pharmaceutical 300g scale thank you...

=8-)
You know that if the cops ever come in that baby is the first thing
they're gonna grab, right? Probably slice open thirty or forty rims,
too, looking for the coke.
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Old 01-23-12, 02:07 PM
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Originally Posted by 3alarmer
You know that if the cops ever come in that baby is the first thing
they're gonna grab, right? Probably slice open thirty or forty rims,
too, looking for the coke.
Good thing I have two toilets...

j/k

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Old 01-23-12, 02:58 PM
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For what's it's worth, I recently wrote an open-source program for use with Park's TM-1 tension meter that automatically converts the deflection reading to kilogram-force and makes a plot of the wheel.

Wheelwright : https://biciworks.com/wheelwright/

This is reminiscent of a spreadsheet from Park out there. I'm still working on making it easier to install, but if you have one of the fancier tension meters out there and would like to help me add it into this program send me a message.
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Old 01-23-12, 03:02 PM
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Using a spoke gauge is the same as using a torque wrench....it's doesn't really measure anything,it's an educated guess.

If you really want to know what the tension is on a spoke,you would measure the stretch.....something nobody does.

Works the same with fasteners.There are too many variables for a torque wrench to be accurite,so stretch is measured when it REALLY matters.

Spoke gauge is good for getting even tension but that's about it.....the rest of the numbers are educated guesses.

Doesn't matter if the gauge reads millionths and you can blow on it and the numbers/needle moves,it's still reading millionths of nothing.

Last edited by Booger1; 01-23-12 at 03:13 PM.
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