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-   -   Testing spoke tension by plucking it (https://www.bikeforums.net/road-cycling/304624-testing-spoke-tension-plucking.html)

donrhummy 06-01-07 08:19 PM


Originally Posted by Rocke
WOW, Bob,
Thanks for the walk down memory… Frank was a genius on many levels. I believe he could play anything he put his mind to. His sense of humor and timing being uncanny at times. I saw him I think when Michael Franks was playing near by and he did a great vibe/jazz thing totally impromptu based on Michael’s music, it was truly magic. (He did the same with Cash and many others.) Thanks for taking me back.

As for the thread… everything has harmonics, why wouldn’t the spokes on a wheel?
I am going to take my sons old guitar tuner and see how close the spokes are on Campy wheels! What a great idea. Blessings.

Let us know what you find! :)

old and new 06-01-07 08:28 PM


Originally Posted by huytheskigod
Being a music person, this is the method I use. In fact, the last wheel I tensioned was done sitting next to a piano and comparing the pitches. If you want, go to your local music shop and pick up either a pitch key or a an electronic metronome/pitch generator. It'll cost no more than $15 for a basic one. The one sitting on my desk right now is a KORG metronome MA-30.

Doesn't seem right. You don't tune a guitar by torsional tension, you go by pitch and pitch only. Why should we believe the torsional tension has a flawless direct relationship to pitch and that we should be sure that the spokes are correctly tuned based on the note they make.Give me a break music man.

byte_speed 06-01-07 09:19 PM

This article http://www.bikexprt.com/bicycle/tension.htm
explains the theory and gives a table of frequencies for various spoke lengths and types.

I built a wheel using this method and it worked pretty well. I found a musical pitch program online that would tell you the frequency of a tone via your computer microphone. I held my mike next to my wheel as I plucked the spokes and just read the frequency on the screen (yeah, I know, I do have a good ear, but this way was much more high tech).

Tmax1 06-02-07 05:18 AM

Do, a deer, a female deer;
Re, a drop of golden sun;
-
-
-
Fa...a long, long way from home...

Hocam 06-02-07 05:42 AM


Originally Posted by waterrockets
You said "truing by ear," which is not possible.



Exactly, and you should balance the three variables as best you can, but give up round and true in favor of tension if there are issues in there. A tiny bobble is not an issue, but but undertensioned spokes are a huge issue. I've re-tuned perfectly round and true wheels that had horrible tension variability (AC Sprint 350s). When I was done, they were just as round and true, but nearly perfectly tensioned.

It is possible to have a systemic tension problem that comes from a symmetrical oval shape to the wheel. In these conditions, it's possible to retain roundness and true, while improving tension regularity. If you build the wheel focusing on all three variables throughout, you will avoid this situation altogether.

The wheels I've built so far (only 4 but I only have 2 bikes, so =p) tend to get brought up to tension during the truing process, especially the rear wheels when getting the dishing right. I've never had an issue with a loose spoke or one that was even close to loose, but the pitch of my spokes varies considerably. I've put about 1500 miles of rough Philadelphia roads on my first set, second set is waiting for the frame to come back from the painters, and no problems. I haven't had to true them and no spokes have loosened.

The next set I build (planning on a XT hub to Velocity Dyad 36H 4x touring wheelset) I will try to take pitch into account.

waterrockets 06-02-07 06:23 AM


Originally Posted by Hocam
The wheels I've built so far (only 4 but I only have 2 bikes, so =p) tend to get brought up to tension during the truing process, especially the rear wheels when getting the dishing right. I've never had an issue with a loose spoke or one that was even close to loose, but the pitch of my spokes varies considerably. I've put about 1500 miles of rough Philadelphia roads on my first set, second set is waiting for the frame to come back from the painters, and no problems. I haven't had to true them and no spokes have loosened.

The next set I build (planning on a XT hub to Velocity Dyad 36H 4x touring wheelset) I will try to take pitch into account.

Yeah, I've only built around 2 dozen wheels, but my first 16 or so were built as you describe. They all lasted ~10,000 miles or so. Unacceptable. Once I started making even tension the highest priority, my wheels became much more durable. I think my current wheelset is headed for 30,000 miles (the braking surface will fail first).

With uneven tension, you're not going to get a loose/floppy spoke. Eventually the spokes with lower tone will fatigue and break at the bend. Pluck around your rim and draw a magic marker dot on your lowest-tone drive-side spoke. I'll bet that's the spoke that breaks one day.

I'm not trying to say your wheel might taco on your next ride. They'll be fine for 5000-7000 miles or so, then start to need more truing, and eventually you'll break a spoke, and replace it. A 1000 miles later, another spoke will break. Then it will get more frequent.

donrhummy 06-02-07 06:32 AM


Originally Posted by byte_speed
This article http://www.bikexprt.com/bicycle/tension.htm
explains the theory and gives a table of frequencies for various spoke lengths and types.

I built a wheel using this method and it worked pretty well. I found a musical pitch program online that would tell you the frequency of a tone via your computer microphone. I held my mike next to my wheel as I plucked the spokes and just read the frequency on the screen (yeah, I know, I do have a good ear, but this way was much more high tech).

What program was this?

I'd like to try it. :)

specq 06-02-07 07:54 AM


Originally Posted by Bob Ross
Isn't there an old episode of The Steve Allen Show, or maybe What's My Line?, where a young Frank Zappa came on and "played" a bicycle by plucking the spokes?

There certainly is. Although he does quite a bit more than just pluck the spokes.

simplify 06-02-07 08:15 AM


Originally Posted by Hocam
If the rim is true radially and laterally, and the spokes are destressed properly they are at the correct tension.

Wrong. You can have a wheel perfectly true and round, stress-relieved, and it can still be WAY undertensioned. In fact, it's much easier to have a perfectly round and true wheel if it's undertensioned. The challenge is to keep it true and round as it's brought up to proper tension.


Originally Posted by Hocam
I don't see how you can take a true, round wheel, mess around with the spoke tension until it's closer to even and have a wheel as true.

But you can, as Waterrockets points out, within about 5%--which is darn good. This is the part that gets *easier* as the tension is raised. There are some excellent wheelbuilding books that will tell you much more about how this is accomplished.

simplify 06-02-07 08:29 AM


Originally Posted by old and new
Doesn't seem right. You don't tune a guitar by torsional tension, you go by pitch and pitch only. Why should we believe the torsional tension has a flawless direct relationship to pitch and that we should be sure that the spokes are correctly tuned based on the note they make.Give me a break music man.

Torsional tension?? Not on spokes! The spokes are not twisted or torqued (unless you have bad technique or did not oil the threads), they are simply pulled tighter by the turning of the nipples. It's exactly the same principle as the tightening of a musical instrument string. No torsional tension.

mcoomer 06-02-07 04:59 PM

Just bike the bullet and buy a tension meter. I've got the one from Park and it's comforting to know that my spokes are in the window given by the manufacturer and that all of the spokes are tensioned the same.

babydee 06-02-07 06:28 PM


Originally Posted by a77impala
I will sometimes strike the spokes with a wrench and check the ones that have a dull sound or different sound that the rest, usually find the looser ones that way.

+1

huytheskigod 06-04-07 11:31 AM


Originally Posted by old and new
Doesn't seem right. You don't tune a guitar by torsional tension, you go by pitch and pitch only. Why should we believe the torsional tension has a flawless direct relationship to pitch and that we should be sure that the spokes are correctly tuned based on the note they make.Give me a break music man.

Sorry that I gave the impression that that I "tune" spokes to exact pitch. I only use it to bring spokes to the same relative tension. Spokes of same length/material and tension will produce the same pitch (more or less). Two guitar strings both being equal in every way when tensioned the same will produce the same pitch. Given that, spokes of similar dimension and material should produce the same pitch when brought to the same tension you can use the pitch method as a tool for even tensioning. So all drive side spokes when bought to the same tension will be one pitch all non-drive side brought to the same tension will be one pitch...but not the same pitch. There is no one perfect pitch that is appropriate for all cases as length of spoke is an important variable. Different lengths will produce different resonant frequencies due to the shortening or lengthening of sine wave when the spoke is plucked and vibrates. Back to old and new's point, it's true you don't tune a guitar to LINEAR tension to achieve a certain pitch however, if you know that a certain pitch produced on the guitar string will yield a certain tension you can achieve that tension by producing that pitch. The flaw being that guitar strings stretch over time and one of your variables change because of it (string's vibration characteristics). A spoke does not stretch nearly as much as a guitar string so pitch to tension relation stays true much longer. Now, you cannot create a true wheel on pitch tension alone. You simply use it to achieve even spoke tension then visual truing will be needed. Pitch will only allow you even tension that is neither too high or too low. By the way, if you want more specifics, I'll gladly take off my music man hat and place on my engineer hat just for you.


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