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Tensiometer

Old 01-20-12, 06:59 PM
  #1  
Soil_Sampler
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Tensiometer

Goodbye FSA, Hello Wheel Fanatyk!

https://wheelfanatyk.blogspot.com/201...nsiometer.html
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Old 01-20-12, 07:09 PM
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Will it work in the confines of a 20" wheel?

=8-)
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Old 01-20-12, 11:05 PM
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A spoke tensiometer is a simple device that allows you to place a spoke across two pivots, apply a perpendicular force to the pivoted spoke, and measure the amount of deflection. That's about all there is to it. Obviously the amount of deflection will depend upon the elastic properties of the spoke, which depends upon the spoke material and dimensions. That deflection needs to be "translated" into a "tension" measurement. So there is no way to directly measure "tension" (what you measure is deflection). I am quite satisfied with the $60 Park tensiometer. Fancier tensiometers, with digital deflection readouts may be easier to read, but you still need to use deflection/tension conversion charts.

YMMV.
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Old 01-20-12, 11:20 PM
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Originally Posted by neurocop View Post
A spoke tensiometer is a simple device that allows you to place a spoke across two pivots, apply a perpendicular force to the pivoted spoke, and measure the amount of deflection. That's about all there is to it. Obviously the amount of deflection will depend upon the elastic properties of the spoke, which depends upon the spoke material and dimensions. That deflection needs to be "translated" into a "tension" measurement. So there is no way to directly measure "tension" (what you measure is deflection). I am quite satisfied with the $60 Park tensiometer. Fancier tensiometers, with digital deflection readouts may be easier to read, but you still need to use deflection/tension conversion charts.

YMMV.



nothing wrong with analogue (sci-fi mag?). whatEVER we're measuring here, it doesn't HAVE to be spot on. this isn't a space shuttle. a guy i used to know got me into rc cars and boats. like to drove me nuts with his obsessive fussing and incessant tweaking instead of running the things. the kind of guy who'd keep sharpening a new pencil down to the eraser, trying to get the perfect point.

nice looking toy, though.
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Old 01-21-12, 03:30 AM
  #5  
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Fancy tools impresses the buyer, so you can raise your rates, for labor.

Don't forget the Machine that goes 'Ping"..
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Old 01-21-12, 03:51 AM
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Ah, the wonderful debate of accuracy and precision, especially when overlaid with the common misconceptions about each. For the uninitiated, accuracy is how close to correct (i.e. if a widgetometer says it's 10.2 widgets on something that's 10.1 widgets, there's a 1% accuracy error), while precision is the level of detail (i.e. a widgetometer reading of 10.20 indicates four digits of precision, or that it believes that it's not 10.19 or 10.21 widgets, while a reading of 10.2 indicates three digits of precision.) I wonder what this thingy provides on the accuracy/precision scale...
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Old 01-21-12, 11:16 AM
  #7  
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Here's the problem I have with these very "high end" tensionmeters:

I'm sure they are awesome tools, capable of very very fine estimates with resolutions of .1, .01 or even .001. In other words, they are tools capable of very very precise estimates.

Which is great, IF....IF...

...the materials you are working with were themselves manufactured consistently with very fine tolerances.

While there are certain model rims that are manufactured with very fine tolerances, you still have to deal with spokes that vary slightly within a gauge, and with spokes that vary composition-wise within a gauge.

Compound the average wheel together that we usually build - at best - all we can get are "rough" estimates of where the individual spokes are at and where the "average" is at.

The result is that you take a very fine tuned and very expensive tool - and drop it right down to the rough estimate world - right where the original Wheelsmith tensionmeter was - right where the current Park TM-1 is.

The Wheelsmith and Park, so long as they are kept callibrated, do the job just fine in that world - for a hellava lot less.


To give an example,

I have a Swiss made Pharmaceutical scale that is rated for 300g with a readout of "xxx.000" It is a very expensive piece of machinery used by Pharmacist's who need to do manual non-pill powderized drug formulations at the milligram level - usually for critical and very dangerous drugs.

I use it to quickly count CNspoke 12mm and 14mm brass nipples.

When I toss in a 12mm nipple, and then swap for another, and another...I get readings of .934 through .964.

What does that mean? I could do the same counting job with a much cheaper gram scale that has a readout of "xxx.0"


These very high quality precision tensionmeters will spend most of their time being used as show pieces, just like like dial indicators...

=8-)
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Old 01-21-12, 12:24 PM
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Originally Posted by p2templin View Post
Ah, the wonderful debate of accuracy and precision, .
+1,000 i

It's become commonplace to use precision to create the illusion of accuracy. For a simple example think about the speedometer of your car. It's accuracy depends on a number of factors, some within the unit, some outside, for example whether your tires are the exact diameter it was calibrated for (they're not). So while a digital speedometer may seem more precise saying you're going exactly 66mph, ti isn't any more accurate than an analog unit that says you're going slightly faster than 65mph, because in face you might only be going 62mph.

There's also the issue of repeatability. Often, an instrument will give different readings for the same value different times for a variety of reasons. If the range of readings is within the stated accuracy it passes the test, but this could be a problem for a spoke tension meter causing a user to waste time correcting what are in face only read errors.

I'm not panning this tool, which appears to be a nicely executed piece of work. I'm just trying to remind folks that for much more dough, it isn't any better from a functional standpoint than most of the units out there.
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Old 01-21-12, 12:26 PM
  #9  
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Originally Posted by neurocop View Post
A spoke tensiometer is a simple device that allows you to place a spoke across two pivots, apply a perpendicular force to the pivoted spoke, and measure the amount of deflection. That's about all there is to it. Obviously the amount of deflection will depend upon the elastic properties of the spoke, which depends upon the spoke material and dimensions. That deflection needs to be "translated" into a "tension" measurement. So there is no way to directly measure "tension" (what you measure is deflection). I am quite satisfied with the $60 Park tensiometer. Fancier tensiometers, with digital deflection readouts may be easier to read, but you still need to use deflection/tension conversion charts.

YMMV.
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.
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Old 01-21-12, 01:57 PM
  #10  
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Originally Posted by p2templin View Post
Ah, the wonderful debate of accuracy and precision
I spoke with one of the phone reps at Easton wheels about wheel building a few times.

I was told that the Easton builders use tone for most of the tensioning process, but that they use a tension gauge to determine the proper tone. Further, the rep claimed they have found they need to calibrate the tension gauge several times a day, as the results will wander. They calibrate using a spoke under a known tension.
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Old 01-21-12, 02:32 PM
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Originally Posted by byte_speed View Post
I spoke with one of the phone reps at Easton wheels about wheel building a few times.

I was told that the Easton builders use tone for most of the tensioning process, but that they use a tension gauge to determine the proper tone. Further, the rep claimed they have found they need to calibrate the tension gauge several times a day, as the results will wander. They calibrate using a spoke under a known tension.
They use the tensionmeter to check final tension...they use tone to isolate "rogue" spokes not in line tension with with the rest as they are truing and tensioning.

=8-)

Sure, if you are building the exact same wheel all the time - you can establish a tone that matches. But if I bring 'em an unknown rim, hub, spokes, and specify the crossing...tone will not be the decider - tensionmeter will be.

The beauty of a tensionmeter is that it measures a deflection for a given length - regardless of gauge, length, crossings, etc.

=8-)
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Disclaimer:

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2. I like anyone will comment in other areas.
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4. I will provide information as I always have to others that I believe will help them protect themselves from unscrupulous mechanics.
5. My all time favorite book is:

Kahane, Howard. Logic and Contemporary Rhetoric: The Use of Reason in Everyday Life

Last edited by mrrabbit; 01-21-12 at 02:45 PM.
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Old 01-21-12, 03:03 PM
  #12  
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For $295, they could at least let you enter the conversion factor for the current wheel's spokes, and then get kgf readings directly, without needing a spoke chart.

From the link:

The tool costs USD$295, and here is what you get:

1. A shock-proof, lockable, foam lined case with metal pin hinges.
2. 26 page Owner's Manual, with many wheelbuilding tips.
3. Laminated Spoke Tension Chart, for convenient conversion.
4. Spare battery.
5. A CD with PDF files of the manual and chart, and our instruction movie.
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Old 01-21-12, 03:10 PM
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I got so excited I went out and just bought the Park tool for $48.41 delivered-

www.aawyeah.com/

40inutes later, I got the email confirming it was shipped!
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Old 01-21-12, 03:25 PM
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Originally Posted by p2templin View Post
Ah, the wonderful debate of accuracy and precision, especially when overlaid with the common misconceptions about each. For the uninitiated, accuracy is how close to correct (i.e. if a widgetometer says it's 10.2 widgets on something that's 10.1 widgets, there's a 1% accuracy error), while precision is the level of detail (i.e. a widgetometer reading of 10.20 indicates four digits of precision, or that it believes that it's not 10.19 or 10.21 widgets, while a reading of 10.2 indicates three digits of precision.) I wonder what this thingy provides on the accuracy/precision scale...
Not quite correct.

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)

The wiki page covers it decently: Accuracy/Precision
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Old 01-21-12, 03:41 PM
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Originally Posted by Bill Kapaun View Post
I got so excited I went out and just bought the Park tool for $48.41 delivered-

www.aawyeah.com/

40inutes later, I got the email confirming it was shipped!
Make sure you create yourself a calibration wheel (old junk wheel) with mutliple readings and the related spokes tagged.

...before you use it.

=8-)
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Disclaimer:

1. I do not claim to be an expert in bicycle mechanics despite my experience.
2. I like anyone will comment in other areas.
3. I do not own the preexisting concepts of DISH and ERD.
4. I will provide information as I always have to others that I believe will help them protect themselves from unscrupulous mechanics.
5. My all time favorite book is:

Kahane, Howard. Logic and Contemporary Rhetoric: The Use of Reason in Everyday Life
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Old 01-21-12, 03:50 PM
  #16  
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Originally Posted by rm -rf View Post
For $295, they could at least let you enter the conversion factor for the current wheel's spokes, and then get kgf readings directly, without needing a spoke chart.

From the link:

The tool costs USD$295, and here is what you get:

1. A shock-proof, lockable, foam lined case with metal pin hinges.
2. 26 page Owner's Manual, with many wheelbuilding tips.
3. Laminated Spoke Tension Chart, for convenient conversion.
4. Spare battery.
5. A CD with PDF files of the manual and chart, and our instruction movie.
Good point, with computers so small now for mobiles devices, you'd think at some point you'd be able to select the gauge being measured right before you start clamping.

And have the converted result right there on the little LCD screen...

=8-)
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4. I will provide information as I always have to others that I believe will help them protect themselves from unscrupulous mechanics.
5. My all time favorite book is:

Kahane, Howard. Logic and Contemporary Rhetoric: The Use of Reason in Everyday Life
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Old 01-21-12, 04:56 PM
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tensiometer

Originally Posted by Bill Kapaun View Post
I got so excited I went out and just bought the Park tool for $48.41 delivered-
www.aawyeah.com/
40inutes later, I got the email confirming it was shipped!
$45.99 shipped
https://aebike.com/itemdetails.cfm?ca...+Daily+Deal%29

compare the $295 WF to the $249 FSA tensiometer.
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Old 01-21-12, 09:12 PM
  #18  
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Originally Posted by rm -rf View Post
For $295, they could at least let you enter the conversion factor for the current wheel's spokes, and then get kgf readings directly, without needing a spoke chart.

I'm starting to wonder how folks use tension meters. There's no need to refer to the chart more than once, before measuring, and no need to ever convert readings to kpf, except maybe once at the end.

You know the spoke's gauge and your target tension. You look at the chart to find the corresponding scale value and decide on an acceptable tolerance. From there in you only need deal with the scale value, with no reason to convert to tension for each spoke.
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Old 01-21-12, 09:34 PM
  #19  
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Originally Posted by FBinNY View Post
I'm starting to wonder how folks use tension meters. There's no need to refer to the chart more than once, before measuring, and no need to ever convert readings to kpf, except maybe once at the end.

You know the spoke's gauge and your target tension. You look at the chart to find the corresponding scale value and decide on an acceptable tolerance. From there in you only need deal with the scale value, with no reason to convert to tension for each spoke.
Well you know, some of us have Alzheimer's. dementia, psychosis, etc...

=8-)
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Disclaimer:

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2. I like anyone will comment in other areas.
3. I do not own the preexisting concepts of DISH and ERD.
4. I will provide information as I always have to others that I believe will help them protect themselves from unscrupulous mechanics.
5. My all time favorite book is:

Kahane, Howard. Logic and Contemporary Rhetoric: The Use of Reason in Everyday Life
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Old 01-21-12, 09:49 PM
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Originally Posted by JohnDThompson View Post
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.
John could you elaborate on how those Trek meters were made? IE.. along the lines of the Park or Fanatyk with a dial indicator?

Was any variation found in the spoke strength's.. to what degree did they vary?
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Old 01-22-12, 08:15 AM
  #21  
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Originally Posted by JohnDThompson View Post
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.
Did you ever do any testing to find how much of the variability was in the spokes, not the meter?
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Old 01-22-12, 08:54 AM
  #22  
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Originally Posted by mrrabbit View Post
They use the tensionmeter to check final tension...they use tone to isolate "rogue" spokes not in line tension with with the rest as they are truing and tensioning.

=8-)

Sure, if you are building the exact same wheel all the time - you can establish a tone that matches. But if I bring 'em an unknown rim, hub, spokes, and specify the crossing...tone will not be the decider - tensionmeter will be.

The beauty of a tensionmeter is that it measures a deflection for a given length - regardless of gauge, length, crossings, etc.

=8-)
That is pretty much what I was trying to say.

On using a meter for the final tension, I think the tone method will get more even tension than using a meter if you aren't nearly tone deaf (assuming the spokes are all pretty much identical). But as you point out, you have to use the meter to establish what tone to listen for.

There are formulas to predict spoke tension from plucked spoke frequency, but these are very inaccurate and affected by the length of the butted section on spokes, spokes contact at the cross, nipple size & point of contact, etc, etc.

I don't quite understand your statement about a tensiometer measuring the deflection of the spoke. I agree with this, but the tension in the spoke is the thing we really want to know, and the conversion from deflection to tension does depend on spoke gauge.

I've wondered how good the tension meters are on bladed spokes. Tiny variations in size or shape could affect the deflection and the final tension deteremined from the chart. It seems that calibrating the meter would be particularly important for these.

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.
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Old 01-22-12, 09:54 AM
  #23  
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Originally Posted by byte_speed View Post
That is pretty much what I was trying to say.

On using a meter for the final tension, I think the tone method will get more even tension than using a meter if you aren't nearly tone deaf (assuming the spokes are all pretty much identical). But as you point out, you have to use the meter to establish what tone to listen for.

There are formulas to predict spoke tension from plucked spoke frequency, but these are very inaccurate and affected by the length of the butted section on spokes, spokes contact at the cross, nipple size & point of contact, etc, etc.

I don't quite understand your statement about a tensiometer measuring the deflection of the spoke. I agree with this, but the tension in the spoke is the thing we really want to know, and the conversion from deflection to tension does depend on spoke gauge.

I've wondered how good the tension meters are on bladed spokes. Tiny variations in size or shape could affect the deflection and the final tension deteremined from the chart. It seems that calibrating the meter would be particularly important for these.

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.

Simplicity = Beauty


Deflection > Coversion = 1 Variable

Tone > Length + Number of Cross Touches + Gauge > Conversion = At Least 4 Variables (3 multiplied)


One is faster with the known...one is faster with the unknown.


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. My meter for counting nipples has TOO much resolution for the job I have it do.

The Park TM-1 seems to do the job quite well - slightly better than the Wheelsmith which I always thought was a teeny bit short on resolution on the readout.

=8-)
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Last edited by mrrabbit; 01-22-12 at 10:00 AM.
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Old 01-22-12, 11:11 AM
  #24  
p2templin
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Originally Posted by FBinNY View Post
I'm starting to wonder how folks use tension meters. There's no need to refer to the chart more than once, before measuring, and no need to ever convert readings to kpf, except maybe once at the end.
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?

It might be fun to hang a banner on your bicycle that says "All of my spokes are tensioned to X <units>!". I bet the same number of people will actually CARE if the banner said "All of my spokes deflect Y <units>!", i.e. zero.
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Old 01-22-12, 12:41 PM
  #25  
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Originally Posted by SortaGrey View Post
John could you elaborate on how those Trek meters were made? IE.. along the lines of the Park or Fanatyk with a dial indicator?

Was any variation found in the spoke strength's.. to what degree did they vary?
We used the Hozan tensiometer:



I'm sorry I can't recall specific numbers; this was over 25 years ago.
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