# Bicycle Mechanics - Spoke Tension by Ear?

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View Full Version : Spoke Tension by Ear?

11-27-12, 04:36 PM
It seems to me that it must be possible to judge spoke tension by ear, rather than tensiometer

When you spin a wheel and let an allen wrench or screwdriver blade lightly tap/bounce off of the spokes as they go by, each spoke will resonate with a pitch that is completely determined by its tension (and thickness and length, but those will all be the same for the same wheel). Left side rear spokes will have lower tension/pitch then right side, but it's easy enough to just strike just rights or just lefts.

For a wheel just built from a perfectly true rim (so no spoke has to work extra hard to pull the rim true in a certain spot), equal tension should mean every left-rear spoke rings the same pitch, every right-rear spoke rings the same pitch, and every front spoke (assuming non-dished) rings the same pitch. It seems like instead of a TM-1 and a deflection-force conversion chart, it should be possible to use a tuning fork and a pitch-force conversion chart.

And somebody (maybe even me) should be able to convert the statement (http://www.parktool.com/blog/repair-help/wheel-tension-measurement) "A wheel with spokes that are within plus or minus 20% of the wheel's average spoke tension is generally considered to have acceptable relative tension." into "A wheel with spokes that ring with pitches within plus or minus X...", for X=minor third, or something like that (2x pitch = 1 octave, but does 2x tension = 2x pitch?)

On a related note, would anybody start a wheel truing (building?) by first setting all spokes (per side) to equal tension (pitch) according to rim spec (say, hypothetically, Mavic Open Sport rear takes A440 on the drive side and E-flat below that NDS), and then removing any residual runout and hop?

bobotech
11-27-12, 05:00 PM
I tension by feel and tone because I don't have the money for a tension meter. It works fine. I will get to about 97 percent complete on a wheel build at home and then bring it to my coop and quite often, it needs no more truing.

FBinNY
11-27-12, 05:00 PM
Experienced wheelbuilders have never had a problem with eliminating spoke to spoke variation in spoke tension without reliance on a spoke tension meter. They've long used sound and/or in combination with good building technique to build wheels with even tension.

However, sound cannot be used for measuring actual tension or the average tension in the wheel. I built wheels for decades without a tension meter, relying on my calibrated fingers to set wheel tension where I felt it needed to be. However, today's stiffer rims, low spoke count wheels, high tension values, and tighter tolerance due to highly dished rear wheels have forced me to break down and buy a tension meter. I do not use it to compare tension of various spokes, but as a spot check of my fingers' calibration and to ensure that the average tension is where I want it to be.

Drew Eckhardt
11-27-12, 05:02 PM
It seems to me that it must be possible to judge spoke tension by ear, rather than tensiometer

It may be, although the tone varies based on unsupported length (that changes based on the rim, hub, and lacing) and spoke thickness. Making an app for that may be pretty straight forward (you don't get a pure tone although I expect you'd still get a useful peak in the FFT output).

You can get relative tension about as uniform using tone as you can with a Park meter - the last front wheel (Reflex clincher, 32 2.0/1.5 DT Revolutions cross-3) I built before getting mine was +9 and -5% at 120 and 104 kgf with a 110kgf average except at the bend that had me replacing the rim. Doing so is also faster than trying to measure.

With moderate weight box section rims and traditional spoke counts you can also get absolute tension right using the Jobst Brandt method of alternately adding tension and stress relieving until the wheel goes out of true in waves at which point you've reached the rim's elastic limit, reduce tension 1/2 turn, true, and be happy. That doesn't work for deep rims and/or low spoke counts where the spoke bed's fatigue life will be the limiting factor and even in wheels where it works using a tension meter and only stress relieving once is faster and more pleasant.

On a related note, would anybody start a wheel truing (building?) by first setting all spokes (per side) to equal tension (pitch) according to rim spec (say, hypothetically, Mavic Open Sport rear takes A440 on the drive side and E-flat below that NDS), and then removing any residual runout and hop?

Having built wheels and dealt with other peoples' mistakes I think the usual method of starting the nipples at the same thread engagement and dealing with issues as they emerge with mostly uniform tightening is easier since you don't need to go backwards as much on tension.

bigfred
11-27-12, 05:06 PM
I know my very limited experience has suggested otherwise. But, I'm all ears as to what others have found. I believe the tension by ear techinique is a theory that has been around a long time and may be used by those who do quite a lot of wheel building. But, I also recall that one of the authors of the most common texts was reported to have changed his tune about tensioning by ear once he actually started using a tension meter.

And that +/- 20% figure is entirely inadequate when building wheels for clydes or other heavy users. Personally, I'm aiming for +/- <5%.

Andrew R Stewart
11-27-12, 05:07 PM
FB- I'm in the same boat as you are. The first real shop i worked at didn't believe in buying prebuilt wheels. We gave a small credit for the hubs on the wheels we replaced (dependent on condition of course) and during the off season we cleaned up the hubs and built wheels. When you build 5-10 wheels a day for a few weeks you get pretty comfy with judgemnents. Now things are not so much different but more critical to be within a "right' range.

Back in the day my cousin, John S Allen, wrote an artical for Bike World about truing and tensioning by tone. he had some mathmatical formula to determin the pitch of a plucked spoke and how it related to length, gauge and tension. Andy.

mrrabbit
11-27-12, 05:10 PM
This topic has been discussed ad-nausem here over and over:

To make it short:

By sound is good for:

- Isolating a rogue spoke
- Partial verification of even relative tension per side of wheel
- Partial indication of overly low or high average tension - i.e., the normal pinch one expects to hear isn't present

By meter is good for:

- Actual tension reading per spoke and across spokes for an average
- Consistency in tension efforts from wheel to wheel
- Speed
- Certification of sorts - especially for high cost high ends wheel as some customers expect it.

Sure it is possible to use sound to determine actual spoke tension - but the variety in crossings, lengths, gauges, make it pretty much feasible primarily for a shop that builds a statically configured set of wheels for periods of time for which they have charted tension > pitch equivalency via testing.

But most shops and builders are building a variety of wheels with random parts and configuration variability. For those environments, a tension meter is quick and efficient.

=8-)

11-27-12, 05:32 PM
This topic has been discussed ad-nausem here over and over:...

Why couldn't I find it? Do the discussions use different terms than "spoke tension pitch"?

While I (0 wheels built) certainly don't presume I can argue with 3000+ wheels built, since we're discussing here, I would argue that pitch could provide a speed advantage over meter.

Given the extra variables you mention that I did not originally consider (crossings, lengths, gauges, also add rim and hub size/construction/material), I grant it may not be feasible to build a reliable conversion chart for all (or even many) possible combinations.

But, for one particular wheel, equal tension should mean equal pitch, so I can envision that (someday, when I retire and have more time to play with bikes), I could be a wheelbuilder that would alternate between occasionally metering one spoke, adding equal tension to all spokes to bring them to a higher pitch (where equal tension is judged by same pitch for a wheel revolution), meter a spoke to guesstimate how much addition pitch I should add, rinse, repeat.

Probably do a final, complete run of tensions on every spoke only at the very end.

What's a tension reading take, maybe 2-3sec ea? So that's a minute or two for a whole wheel, vs maybe 5 sec for a wheel revolution?

11-27-12, 05:33 PM
Back in the day my cousin, John S Allen, wrote an artical for Bike World about truing and tensioning by tone. he had some mathmatical formula to determin the pitch of a plucked spoke and how it related to length, gauge and tension. Andy.

RaleighSport
11-27-12, 05:47 PM
From the man himself.

No. You can judge spoke tension by the pitch, but actual truing must be done by looking at the rim as it turns.

See: http://sheldonbrown.com/wheelbuilding

Tightening spokes doesn't make other spokes get loose, as a general rule.

People have been building spoked bicycle wheels for 150 years, but tensiometers have only been readily available for the last 10-15 years. They're handy, but by no means essential.

+-------------------------------------+
| Only those who attempt the absurd |
| will achieve the impossible. |
| --Albert Einstein |
+-------------------------------------+

mrrabbit
11-27-12, 05:58 PM
Why couldn't I find it? Do the discussions use different terms than "spoke tension pitch"?

While I (0 wheels built) certainly don't presume I can argue with 3000+ wheels built, since we're discussing here, I would argue that pitch could provide a speed advantage over meter.

Given the extra variables you mention that I did not originally consider (crossings, lengths, gauges, also add rim and hub size/construction/material), I grant it may not be feasible to build a reliable conversion chart for all (or even many) possible combinations.

But, for one particular wheel, equal tension should mean equal pitch, so I can envision that (someday, when I retire and have more time to play with bikes), I could be a wheelbuilder that would alternate between occasionally metering one spoke, adding equal tension to all spokes to bring them to a higher pitch (where equal tension is judged by same pitch for a wheel revolution), meter a spoke to guesstimate how much addition pitch I should add, rinse, repeat.

Probably do a final, complete run of tensions on every spoke only at the very end.

What's a tension reading take, maybe 2-3sec ea? So that's a minute or two for a whole wheel, vs maybe 5 sec for a wheel revolution?

1. Do you understand the up front work required to chart the frequencies for each wheel you need to build?
2. Do you understand the difference between theory and properties and then actual application especially where economics are a concern?

1-2 seconds on average - only a few spokes at a time during most of the build. More spokes read in the last few tension cycles to finish the wheel.

Despite its imperfections, the tension meter has one "beauty" to it: It makes no assumptions about crossing, gauges, etc. It simply measures a given deflection per given distance. When interpreted, the chart only makes an assumption about the material, profile and gauge - nothing more.

As I stated earlier, this has been discussed many times over - even to the point of people going at each other's throats. Usually because someone starts to push advocacy rather than discussion. Most of us here understand how both work - and don't really have any beef against the sound method in general.

Someone did post earlier a link to an Easton video - where both methods are used concurrently. It's a nice video to watch...hopefully someone can post it again.

=8-)

mrrabbit
11-27-12, 06:12 PM

Only took 15 seconds in advanced search to find it:

"tension sound pitch"

"Bicycle Mechanics"

=8-)

canyoneagle
11-27-12, 06:16 PM
By sound is good for:

- Isolating a rogue spoke
- Partial verification of even relative tension per side of wheel
- Partial indication of overly low or high average tension - i.e., the normal pinch one expects to hear isn't present

By meter is good for:

- Actual tension reading per spoke and across spokes for an average
- Consistency in tension efforts from wheel to wheel
- Speed
- Certification of sorts - especially for high cost high ends wheel as some customers expect it.

Sure it is possible to use sound to determine actual spoke tension - but the variety in crossings, lengths, gauges, make it pretty much feasible primarily for a shop that builds a statically configured set of wheels for periods of time for which they have charted tension > pitch equivalency via testing.

But most shops and builders are building a variety of wheels with random parts and configuration variability. For those environments, a tension meter is quick and efficient.

=8-)

+1.

I think tone alone can be deceiving (seeking a specific "pitch"). Tone + calibrated fingers can get you pretty damn close. It does not take too long to get a sense for what a properly tensioned spoke of a given size should feel like, and the tone exercise can help identify deviations in tension (but is susceptible to differences in contact pressure of crossing spokes, etc).

You can build a great wheel with common sense and a calibrated touch. I have not built 3000 wheels (yet ;) ) but I can guess tension fairly well by feel. You can too!

I personally prefer to use the meter, and I do check every spoke at the start of final tensioning, with a spot check on subsequent tensioning rounds (more spokes as it progresses) and a final check on each spoke when the wheel feels close to completion.
I'm building sporadically, so I find the meter to be a nice tool to have in the quiver, as I like to build within close tolerance to current specs.

11-27-12, 09:23 PM
No. You can judge spoke tension by the pitch, but actual truing must be done by looking at the rim as it turns.

Certainly, but truing is not the same as equal tensioning. By the same token, you can judge spoke tension with a tensiometer, but actual truing must be done by looking at the rim as it turns.

I guess the exception would be a set of geometrically and mechanically perfect rims, hubs, and spokes, in that case a perfect truing would have perfectly equal tension.

FBinNY
11-27-12, 09:31 PM
As I and others have said, tension can be used to match the spoke tensions within a wheel, and can be a useful and fast method for doing do.

But pitch cannot reliably be used for absolute tension. Not only are there too many combinations of free span and gauges to make a meaningful chart, but there is also a decently wide spectrum of desired tensions for various wheels. That means that there are 2 sliding variables; free length and target pitch; so establishing the database would be one hell of a chore.

Then when you were finished, it would be totally useless since only a small percentage of people have perfect pitch and can identify or reproduce a pitch without a pitch pipe or piano.

In short, the human ear does a good job spotting changes in pitch, but is not well calibrated for identifying a specific pitch.

11-27-12, 09:31 PM
Despite its imperfections, the tension meter has one "beauty" to it: It makes no assumptions about crossing, gauges, etc. It simply measures a given deflection per given distance.

And since there is a direct relationship between tension and pitch for a given wheel, the meter can be used to calibrate pitch for that wheel, and even an unmusical ear could easily get a set of spokes up to an equal pitch to within an eighth-step, and I guess another form of my question would be how that resolution compares with the quarter-unit-of-deflection readable on the meter?

Anyways, thanks for digging up the extra links for me, I have some homework to do!

(Do you have an ETA for changing your sig to 4000+ wheels built?)

fietsbob
11-27-12, 09:38 PM
Those crank screwdrivers are great at counting nip turns as you go around the wheel.

Using the Meter in the shop does make the customer feel better, about their product .
with numbers as a reference..

But As a Player of stringed instruments, my own wheels, I'm fine with relative pitch.

11-27-12, 09:38 PM
As I and others have said, tension can be used to match the spoke tensions within a wheel, and can be a useful and fast method for doing do.

But pitch cannot reliably be used for absolute tension. Not only are there too many combinations of free span and gauges to make a meaningful chart, but there is also a decently wide spectrum of desired tensions for various wheels. That means that there are 2 sliding variables; free length and target pitch; so establishing the database would be one hell of a chore.

Then when you were finished, it would be totally useless since only a small percentage of people have perfect pitch and can identify or reproduce a pitch without a pitch pipe or piano.

Yes, I envision the use of either a musical instrument for pitch reference, or something like an electronic guitar tuner. But yes, I see now it would be a pointless task trying to create an absolute reference or formula for any given wheel, probably the best would be anecdotal lists, like "I built a wheel out of these rims, nipples, spokes, and hubs, with this lacing pattern, and achieved drive side tension of such and such numbers, which resulted in a drive side range of A440-C, and NDS range of D-flat to E-flat. Then if somebody wanted to build the same wheel, they could maybe do it all by pitch, with no tensiometer

11-27-12, 09:43 PM
Using the Meter in the shop does make the customer feel better, about their product .

As a Player of stringed instruments, my own wheels, I'm fine with relative pitch.

I'm a violinist myself, which probably explains my interest.

Also, my dad used to be a piano tuner, and I know that the best piano tuners do not rely on oscilloscopes (you could tune a piano with a scope even if you're deaf), nor do they rely on perfect pitch. They have one or two tuning forks, and the rest is by ear. But then of course a properly tuned piano deals with pitch by definition, not by accident.

fietsbob
11-27-12, 09:48 PM
One of My Friends, a Music teacher with Concert piano chops , got lap top software for Piano Tuning .

Andrew R Stewart
11-27-12, 11:38 PM
I'm about the least musically inclined person you'd meet. Tone and beat are perfect in my head but not in my voice or hands. Yet I find it easy to follow the varying tone of plucked spokes. I use a tension meter on a few spokes to establish the base line and plucking to check the remainder.

Just today we were talking about using the sounds of a shop for a "song". But that's another thread... Andy

Drew Eckhardt
11-28-12, 01:50 AM
As I and others have said, tension can be used to match the spoke tensions within a wheel, and can be a useful and fast method for doing do.

But pitch cannot reliably be used for absolute tension.

It depends on how much technology you can accept.

Not only are there too many combinations of free span and gauges to make a meaningful chart

Assuming people would need to use a chart is anachronistic.

Most people already have at least one portable computer (in the form of a phone, tablet, or laptop) with a microphone that makes it trivial to measure a spoke's resonance via a FFT.

It would be painless to run a program on it to which you feed the data you gave your spoke length calculator, its output, and nipple plus spoke types.

That means that there are 2 sliding variables; free length and target pitch; so establishing the database would be one hell of a chore.

You don't need a database. One of the numerous spoke length calculators will output spoke length, ERD, and hub geometry which can be used to calculate free lengths. In theory you could look at nipple type which affects where the threads start; although 1-2mm of variation is inconsequential compared to 200-300mm of spoke length. Butting length should affect things too but not enough to matter.

There are reasonable default tensions that won't lead to wheels which collapse, wheels which go out of true, or stress cracks in the vast majority of rims with few currently manufactured exceptions. That default, rules for exceptions, or a user input will combine with the free length and spoke cross-section to produce a calculated target pitch. As more people use the tool and contribute there will be more entires producing optimal higher tensions.

Then when you were finished, it would be totally useless since only a small percentage of people have perfect pitch and can identify or reproduce a pitch without a pitch pipe or piano.

A \$25 MSRP computer (Raspberry Pi for example) has perfect pitch (from an FFT which converts things into the frequency domain). Everyone with a laptop made in the last five years, tablet, or smart phone already has a computer that's at least as powerful and includes a microphone which means their incremental cost is that of the software. That will be zero when wheel building geeks come up with formulas or software for their own use (If I was inexperienced enough for such a thing to be technically interesting or built more wheels than my wife and I needed for our own use I'd do it. Other good enough geeks are early enough in their careers and/or build enough wheels) and share for free. When that is not user friendly enough there will be be people with motivation and aptitude (less than the people who figured out how to do it) to make it so. In the cycling problem space some one added a tool to Golden Cheetah using Chung's virtual elevation model for aerodynamic and rolling drag estimation allowing non-technical users with power meters to ride around appropriate courses to net usable information on position and equipment drag where the alternative is waiting for the next group deal, flying to Washington state, and paying hundreds of dollars for their time in the UW low speed wind tunnel.

People who want to do things to old ways will still be able to. Although I have access to CNC equipment I still use my manually operated power tools to make sub-templates, master templates, and then the wood parts I need because using the robots would usually be too much like what I do for my day job for maximal enjoyment. More idealistic Neanderthals limit themselves to hand tools.

People who just want results will be able to poke their phone a few times and have the right magic happen apart from the wrench turning and accompanying beer drinking.

Mark Kelly
11-28-12, 03:31 AM
I build my wheels by ear too.

Although I own thousands of dollars worth of signal and function generators, GPS disciplined time bases, a spectrum analyser which covers the audio band (not that common, most are RF) and a calibrated microphone, I've never bothered to instrument this task. I just listen to them. I know what a correctly tensioned spoke sounds like and I know if one is too loose or too tight.

For the OP, your estimation of a minor third is close to exact.

For a given mass per unit length pitch varies linearly with tension. This applies to spokes so 20% variation in tension will be 20% variation in pitch.

One semitone is about 6% (12throot 2 = 1.0595) so a 20% variation is a little more than 3 semitones or a minor third.

zacster
11-28-12, 04:50 AM
I used a guitar tuner to verify, but I was pretty close by ear. It isn't that hard to hear it. I've only done one wheel this way about 3 years ago now and it is still true even though I ride in NYC and weigh over the limit of the original manufacturer's spec. I've been carrying a spoke wrench in my seat wedge ever since I built it and there it sits. This was a 24 spoke rear wheel too, so it fits the "low spoke count" type, and was my own personal rebuild of an Easton/Velomax hub with spokes that I bought for practically nothing on ebay. EA90 wheels are pretty expensive, even used, but my build is just as light and as far as I'm concerned, better built.

JohnDThompson
11-28-12, 07:53 AM
pitch cannot reliably be used for absolute tension. Not only are there too many combinations of free span and gauges to make a meaningful chart, but there is also a decently wide spectrum of desired tensions for various wheels. That means that there are 2 sliding variables; free length and target pitch; so establishing the database would be one hell of a chore.

But pitch is useful in determining relative tension, and an anomalously tensioned spoke is quite obvious even to a musical inept like me.

11-28-12, 08:18 AM
I build my wheels by ear too.

Although I own thousands of dollars worth of signal and function generators, GPS disciplined time bases, a spectrum analyser which covers the audio band (not that common, most are RF) and a calibrated microphone, I've never bothered to instrument this task. I just listen to them. I know what a correctly tensioned spoke sounds like and I know if one is too loose or too tight.

For the OP, your estimation of a minor third is close to exact.

For a given mass per unit length pitch varies linearly with tension. This applies to spokes so 20% variation in tension will be 20% variation in pitch.

One semitone is about 6% (12throot 2 = 1.0595) so a 20% variation is a little more than 3 semitones or a minor third.

Hey thanks! I wasn't sure whether the 20% rule of thumb would translate linearly, it's good to know that minor third would work; I can listen for that in terms of relative, and some day when I set out to (re)build a wheel I will beg, borrow, or steal (or perhaps even buy!) a tensiometer and work a hybrid technique.

11-28-12, 08:27 AM
Anything done by feel is not going to be consistently accurate. Gerd Schraner in his book admited he was surprised that he needed a tensiometer to be accurate.

11-28-12, 08:58 AM

Thx mr rabbit, that was a great video; now I want to skip wheelbuilding and just buy some Eastons!

(Funny, in that old thread, I noticed somebody making a reference to "2000+ wheels", and that was just last year! You must be speeding up, so the tensiometer can't be slowing you down that much!!)

BikeWise1
11-28-12, 09:03 AM
The Rabbit nailed it!

As a wheelbuilder, I rely on repeatable results which are easy to attain with an impartial measuring device. As someone who works on stringed musical instruments, I have observed that our personal perception changes daily, and is less trustworthy than we think.

Plucking spokes is fine to quickly assess relative tension on a wheel, but when it comes to professional results, which in my case include warranties against spoke breakage, I require absolute, rather than relative measurements.

11-28-12, 09:08 AM
Anything done by feel is not going to be consistently accurate. Gerd Schraner in his book admited he was surprised that he needed a tensiometer to be accurate.

Indeed, I recently had my own mind changed (http://www.bikeforums.net/showthread.php/845896-Not-using-a-tire-pressure-gauge?p=14827176&viewfull=1#post14827176) about pressure gauges. I thought I could "feel" when my road tires were pumped up enough, turns out anything above, say 90-100psi is indistinguishably rock-hard for my thumbs.

But the human ear's resolution for pitch is plenty sufficient to measure spoke tension objectively; there just needs to be calibration, i.e. a tensiometer to establish the necessary reference pitch.

BTW, (as usual) I should have searched SB first (http://sheldonbrown.com/wheelbuild.html):

The second way of judging spoke tension is by plucking the spokes where they cross and judging the musical pitch they make. If your shop doesn't have a piano, and you don't have perfect pitch, you can compare it with a known good wheel that uses the same length of spokes. This will get you into the ballpark. Before I started using a spoke tensiometer, I used to keep a cassette in my toolbox on which I had recorded my piano playing an F#, a good average reference tone for stainless spokes of usual length. (For more details on this method, see John Allen's article: Check Spoke Tension by Ear. (http://www.bikexprt.com/bicycle/tension.htm))

That link at the end is for the above-mentioned article, which I will definitely be reading! But it seems worth noting "F#, a good average reference tone for stainless spokes of usual length". Surely this would have to be refined for particular spokes, DS/NDS, etc.

canyoneagle
11-28-12, 11:48 AM
Hey thanks! I wasn't sure whether the 20% rule of thumb would translate linearly, it's good to know that minor third would work; I can listen for that in terms of relative, and some day when I set out to (re)build a wheel I will beg, borrow, or steal (or perhaps even buy!) a tensiometer and work a hybrid technique.

The Park TM-1 (http://www.parktool.com/product/spoke-tension-meter-tm-1) is a great device for not too much money (about \$50-60). It is totally worth it if you plan on building even one more wheel, as the labor alone for a shop build will run you \$40-60.

cycle_maven
11-28-12, 02:57 PM
Just for reference- an octave is 2x the frequency, which is 12 semi-tones. The frequency varies with the square root of tension. So each semi-tone (the difference between C and C#, for example) represents about 12% tension difference, or about 13 KGf near 110 KGf total tension (which is quite a bit of variation). An octave is 4x the tension.

canyoneagle
11-28-12, 03:02 PM
Just for reference- an octave is 2x the frequency, which is 12 semi-tones. The frequency varies with the square root of tension. So each semi-tone (the difference between C and C#, for example) represents about 12% tension difference, or about 13 KGf near 110 KGf total tension (which is quite a bit of variation). An octave is 4x the tension.

So it seems that the options are to either use a guitar tuner or a tension meter ;)

wphamilton
11-28-12, 03:31 PM
It may be, although the tone varies based on unsupported length (that changes based on the rim, hub, and lacing) and spoke thickness. Making an app for that may be pretty straight forward (you don't get a pure tone although I expect you'd still get a useful peak in the FFT output) ...

This is an intriguing idea - I assume that you're thinking of feeding the app the length and weight of the spoke, letting the phone or tablet hear it and output the tension? What other useful information should the app present? Can you think of other parameters it would need?

Drew Eckhardt
11-28-12, 03:55 PM
This is an intriguing idea - I assume that you're thinking of feeding the app the length and weight of the spoke, letting the phone or tablet hear it and output the tension?

Right.

What other useful information should the app present?

An option to make a table of spoke tensions with average, low, and high in each side would be neat but not necessary. It could also plot the tension data like Park's spreadsheet does.

Can you think of other parameters it would need?

Nothing else is needed.

Optionally it could eliminate the measuring step by calculating the span length based on hub, rim, and lacing pattern where the database was populated via one of the exiting spread sheets.

Mark Kelly
11-28-12, 05:16 PM
Just for reference- an octave is 2x the frequency, which is 12 semi-tones. The frequency varies with the square root of tension. So each semi-tone (the difference between C and C#, for example) represents about 12% tension difference, or about 13 KGf near 110 KGf total tension (which is quite a bit of variation). An octave is 4x the tension.

My bad, I misremembered the equation. Should have looked it up.

That means 20% tension is roughly one and a half semitones, so +/- 20% is a minor third (rather than +20%).

Mark Kelly
11-28-12, 05:29 PM
As is so common, we are all repeating what has gone before and getting lots of it wrong (well I am anyway).

http://www.ihpva.org/HParchive/PDF/hp53-2002.pdf

(http://www.ihpva.org/HParchive/PDF/hp53-2002.pdf)

In this he notes that both the mass per unit length and the maximal acceptable tension are proportional to the cross sectional area, so there is no need to compensate for spoke weight.

wphamilton
11-29-12, 07:25 AM
Right.

An option to make a table of spoke tensions with average, low, and high in each side would be neat but not necessary. It could also plot the tension data like Park's spreadsheet does.

Nothing else is needed.

Optionally it could eliminate the measuring step by calculating the span length based on hub, rim, and lacing pattern where the database was populated via one of the exiting spread sheets.

Thanks. I may give this a shot, just to get the hang of writing an android tablet app. Plus then I might be able to actually get my wheels right, instead of approximately good enough.

In this he notes that both the mass per unit length and the maximal acceptable tension are proportional to the cross sectional area, so there is no need to compensate for spoke weight.

I figured that weighing the spoke, with knowing it's length (mass per unit length), is easier than finding the cross section. :) But, whatever is most convenient.

FMB42
11-29-12, 08:10 AM
https://itunes.apple.com/app/spoke-tension-gauge/id518870820?mt=8

cycle_maven
11-29-12, 09:40 AM
OK, I'm buying it. Probably easier to use than my TM-1, and maybe nearly as accurate. Thanks!

11-29-12, 10:53 AM
That's fantastic! Almost makes me want to buy a smartphone (if it wasn't more expensive than a tensiometer...)

I actually think that, just for the fun of it, I'll buy the app for a friend with an iPhone or iPad just so I can borrow it and try it out!

bigfred
11-29-12, 11:02 AM
Aren't there plenty of instrument "tuning" apps and devices out there? I know my wife has one for her uke' that probably didn't cost her much. Although, she probably applies the same declared cost correction factor to her hobbies as I do to bike bits:-)

Mark Kelly
11-29-12, 04:43 PM
I figured that weighing the spoke, with knowing it's length (mass per unit length), is easier than finding the cross section. :) But, whatever is most convenient.

You miss the point: you don't need to use the mass when calculating the correct pitch.

FBinNY
11-29-12, 04:55 PM
You miss the point: you don't need to use the mass when calculating the correct pitch.

Correct me if I'm wrong, acoustics and harmonics isn't my forte. But isn't it the case that for the same length and tension, a heavier (thicker) wire will sound a lower note?

11-29-12, 05:03 PM
Correct me if I'm wrong, acoustics and harmonics isn't my forte. But isn't it the case that for the same length and tension, a heavier (thicker) wire will sound a lower note?

I am confused about this as well. In the John Allen article (http://www.bikexprt.com/bicycle/tension.htm), there are two consecutive sentences right near the beginning that seem to contradict each other:

The resulting musical pitch is higher if a spoke is tighter, and the optimum pitch does not depend on the thickness of the spoke. To know what the musical pitch should be, all you need to know is the approximate spoke length and whether you will be using plain-gauge spokes or butted spokes, which are effectively shorter since their ends are thicker

Note also that all stringed-instruments have their lower-pitched strings also thicker. (However, no stringed instrument I've ever heard of has double-butted strings!)

bigfred
11-29-12, 05:11 PM
At what point does one simply decide that a deflection spring device is the easiest, most consistant, cost effective way of verifying ultimate tension?

11-29-12, 05:13 PM
Ah, from the follow-on link (http://www.bikexprt.com/bicycle/pitcheqn.htm), this kind of makes sense:

One way to think of this is to imagine two identical spokes side by side, both of the same gauge and at the same tension. They vibrate at the same frequency. Now imagine lightly connecting them together all along their length. They still vibrate at the same frequency. Finally, imagine merging them into one, thicker spoke. It still vibrates at the same frequency.

But for butted spokes, the change in diameter ruins all that; the thinner (shorter) section is really what's doing almost all of the vibrating, the butted ends are (relatively) still, so it's not that the spoke gets thinner in the middle, it's that (approximately) only the middle section is vibrating.

FBinNY
11-29-12, 05:37 PM
The resulting musical pitch is higher if a spoke is tighter, and the optimum pitch does not depend on the thickness of the spoke. To know what the musical pitch should be, all you need to know is the approximate spoke length and whether you will be using plain-gauge spokes or butted spokes, which are effectively shorter since their ends are thicker

Note also that all stringed-instruments have their lower-pitched strings also thicker. (However, no stringed instrument I've ever heard of has double-butted strings!)

If you leave the bike world and join the rest of the world, the natural frequency depends on the tension, linear density (weight per unit length) and length. Obviously all other things being equal, a thicker spoke will produce a lower pitch.

Mr. Allen speaks of butted spokes and for these things are a bit different because the end of the butted length acts as a node (terminus) so you would use the lighter gauge, and the length of that section only. (that part of his statement is correct, but to say that thickness or gauge isn't a factor is simply incorrect).

FBinNY
11-29-12, 05:49 PM
Ah, from the follow-on link (http://www.bikexprt.com/bicycle/pitcheqn.htm), this kind of makes sense: One way to think of this is to imagine two identical spokes side by side, both of the same gauge and at the same tension. They vibrate at the same frequency. Now imagine lightly connecting them together all along their length. They still vibrate at the same frequency. Finally, imagine merging them into one, thicker spoke. It still vibrates at the same frequency.

This is a disingenuous analysis, and shows how a cleverly constructed model can produce a wrong conclusion. If you take two wires that are under tension and merge them into one, then not only is the mass doubled, but so is the tension. So yes, twice the linear mass at twice the tension will produce the same pitch. However if you don't adjust the tension in proportion to linear mass, then mass does make a difference.

BTW- if John A could have had a great career dealing 3-card Monte in NYC if he wanted.

BTW- the reason string instruments use heavier wire for bass strings and lighter wires for high note, is a practical consideration. In theory you could build a piano or violin using the same wire for all the strings, but that would require a tremendous range of tension. Using lighter strings for high notes reduces the tension needed, and heavier strings for low notes is better than trying to work with strings that border on being slack. For a violinist, it allows roughly equal bow pressure on all strings, which makes the instrument much easier to play.

TiHabanero
11-29-12, 05:51 PM
No question, using a tensiometer is the best way to build a good wheel, however that does not mean an equally good wheel cannot be built without one.
Back in the day of being a bike mechanic I built plenty of wheels without a tension meter, this was before they were around, and the wheels were fine and stout. Ten years ago I build a rear commute wheel from a used rim and hub without a tension meter. Before the axle broke it had 20 thousand miles on it and never a problem other than a single spoke loosening each year, yes the same spoke! Retightened it and rode it until it loosened again.
Now I have a wheel I salvaged from a junker and tensioned it by feel. Although only 3100 miles on it, I have never trued it. Works just fine.
Do not, under any circumstance purchase a cheap wheel. You will get what you pay for.
I weigh in at 235 lbs.