Why is the elbow localized but the butting points aren't? Is is because one is straight but the other isn't.

In order for the elbow to actually move during use (assuming it's conforming to the hub flange via elastic deformation) the spoke elastic stretch would have to release almost completely, ie. the spoke would have to go almost slack. That would be a problem sure, but no just for the elbow.

Here's a fun analogy. If it takes 5000N to fully compress a spring and you add 6000N of force after which you cycle the force between 5500N and 6000N, how much does the spring wear out? It doesn't, because it doesn't move. It's the same with the elbow. If it's impossible to say whether it's plastically or elastically deformed before detensioning the wheel, the elbow is "fully compressed" when tensioned.

There was so much irrelevant fluff that I considered ignoring this post altogether but this last paragraph... Yeesh!

Righto, so let's establish that you ear is not more accurate than a tensionmeter for a multitude of reasons. Firstly in order to accurately listen to the minute differences in spoke pitch you need to be fairly practiced in relative pitches, ie. musical training.

Secondly, a tensionmeter measures a different thing than pitch. A tensionmeter isn't really affected by the variables that cause massive changes to pitch. A tensionmeter measures how much the spoke deforms which isn't affected much by crossings or minor changes in spoke length.

Things that affect pitch however:
Spoke length
Effective spoke length (hub flange drilling, rim drilling, threading depth etc.)
Spoke crossings
Spoke thickness
Spoke tension

Pitch isn't accurate in any wheel because spoke lengths and threading lengths vary so much. One could be lead to believe that the differences in modern spokes and components are so small that they don't have an effect. They'd be wrong. As a reference, the frets on modern bass guitars are measured to the tenth of a millimeter along the whole scale length of 860+mm. Basses aren't that bothered about that but since spokes are so short (usually less than 300mm) they are more akin to violin strings. And the violin is extremely particular about correct string length for the correct pitch.

Pitch works best with radial wheels or with untucked wheels where the crossings just go over the other spokes and not under, ie. there's not as much contact between spokes.

With traditionally built 2x or 3x tucked wheels the spoke crossings act as frettings, ie. they change the pitch. How much? No one knows as it depends on the tension and length of the crossing spoke and on and on it goes.

So rough adjustment with pitch and then final adjust with a tensionmeter.

Since we're apparently playing that fun credential game, I've played instruments since I was under 10 years old. I currently play the violin, viola, cello and bass guitar. I setup the bass guitar myself and do minor adjustments to the violin family instruments. Bigger things I let the luthier do, because unlike building wheels, building bowed string instruments is an actual art as well as a science.

Yes. That is called fatigue limit. It happens within elastic deformation. It's typically around 40% of UTS. I couldn't find the strength values of DT swiss spokes but I could deduct from some destructive tests that it's around 1100 MPa. 40% of that is 440 MPa or 44kgf/mm^2. For a 2mm spoke shoulder that's around 141kgf.

So even if the elbow hasn't been set and flexes to shape instead, if there is sufficient tension on the wheel, the spoke should never go over it's fatigue limit. And under the fatigue limit it can go through essentially unlimited cycles.

You know, I have to thank you. This has been very informative. I now have better answers to how the spoke stress cycling works and why those 2,3mm elbows really are a good idea. The fatigue limit of that elbow is over 180kgf.

How do spoke lengths vary on one side of one wheel?

Why would relative tension between spokes on a single wheel be different from each other when they are at the same tension?

Do you understand that relative tensions was what I said? Doesn't seem like it.

Not exactly sure what you're asking here but to clarify:

Spoke lengths have variation. You as a wheelbuilder should know this. If you buy a bunch of spokes at say, 290mm lengths, some might be 290,5mm while some might be 289,4mm. Due to spoke head and elbow variation the spokes might seat at the hub at different "heights" making the spokes effectively vary in length after they've been threaded in the nipple. Rims may have variation and a 1mm hop at a pinned joint isn't unheard of no matter how much you crank up the tensions there.

So you end up with spokes which have different effective lengths. Scale length of a string or wire alters the tension required for achieving the same pitch. So different effective spoke lengths mean that in order to achieve the same pitch, they will be at different tensions. You won't be able to match tensions with pitch alone, which means pitch isn't the fine adjustment you think it is.

This is stringed instrument 101. If you wish to refute any of the above, you may want to read up on stringed instruments, how they're tuned, what scale length is etc.

And that's all before string crossings come into play.

The sound the a piano string or a spoke makes is based on the length and tension of the exposed part of the string or spoke, not what is down on the other side of the nipple or fret. That's 101 - the violin doesn't know how much string is wrapped around the tuning peg. And the location of the flange, spoke crossings and rim are all very concentric, so the distance, tension and tone of the spokes at similar tensions are very close. (The tone you're looking for is produced between the rim and the touching spoke cross.) Otherwise, you couldn't true a wheel until it is hard to see it spinning.


However, you aren't going to tune all the spokes to exactly C. As I stated, using tone - which requires no music training - is a more accurate method to find variations in spoke tension than your typical tensiometer. And that's because tensiometers are more difficult to detect small differences in tension because they are relatively crude devices with arbitrary placement along the spoke. If you were using embedded digital strain gauges, that would be better than tone, but we don't use those.


You also seem to be unaware that using tone is a common practice - not something I've invented. So you are, once again, opening your pie hole about something you know nothing about and objecting to things you don't understand - like what part of a musical instrument makes the tone. Plucking or tapping the spokes is a quick, simple method for identifying large tension variations between pairs of spokes and evening them out (that might be missed using a crude tensiometer), which leads to more stability in the wheel build, and guards against damage from too high or too low individual spoke tensions.

That's a dumb analogy, not a fun one. A spoke is in tension, not compression. It is not analogous to a spring compressed until the coils are touching each other, because that is a mechanical limit. A spoke or spring in tension doesn't have a mechanical limit - it can keep stretching until it breaks. A fully compressed spring can't break from compression.

A sprung elbow can "move" for exactly the same reason that the rest of the spoke can elongate - because tension changes the shape of everything based on where the forces are applied. A straight section - like the end of the butt - is going to elongate in proportion to the amount of material. The butt isn't a stress riser because there is no bending force against it. The spoke is equally weak right next to the butt as it is mid spoke.

The sprung elbow is touching the flange, but is not necessarily at its mechanical limit in how short a distance it can make that curve. So as tension increases, that partially collapsed curve does get smaller and flatter, trying to compress into the flange, and it is doing that under a strain that is greater on the outside of the curve than the inside. So as tension changes, the bend experiences changes in that relative strain.


Which is why we are having a conversation about elbows breaking, instead of having a conversation about why elbows never break. If you actually believed your BS, you would say that there is no force that could break an elbow.

I'll give you props for trying. We'll make a musician out of you yet! Next look up guitar harmonics. I'll give you a hint. The crossed spoke doesn't work out exactly as fretting a note. But even if it did, the crossing location is random at best in terms of accurate pitch which further makes tensioning via pitch less accurate. The whole spoke does contribute to the pitch it makes when plucked.

Same length spokes are also "very close to the same length" but when we're talking pitch with these scale lengths and tensions, "very concentric" just isn't accurate enough for fine tuning tension. I would rather get the tensions actually close with a tensionmeter rather than guesswork close by ear.

What?

The placement has some effect sure, but if you maintain the same placement every time, you'll get repeatable results.

Tone does require music training. If you're tone deaf you need more music training. Relative pitch needs to be learned just as much as perfect pitch does.

Large tension variations? Fine adjustment? Do these two actually go together. I also know tone is a tried and true method. I use it. But it's a ballpark method whereas fine tuning is done with a tensionmeter.

But you did good trying to build a strawman to distract from the weakness of your other arguments. I do admire your inventiveness though. Once one of your arguments is shot down, you bounce back with a new (albeit often false) concept or term. It's quite impressive really.

You're an AI, aren't you? I have never had a conversation with an actual human being that was so carefully and consistently devoid of actual experience in the real world.


Tell you what - you go and do the 30 degree spoke bend test I created, then report back. Then you tune the spokes and measure the tensions of those tuned spokes and report back. Both of which are going to be hard when you exist in a server.

I'm fairly certain the elbow gets pulled in place way before maximum elongation for the final tension is reached. That'll of course will depend on the butting etc.

That's not the definition of a stress riser. In fact not even close. You should know this if you've been a crash investigator.

And if spokes cycled anywhere near their fatigue limit that might count for something. But as established above, they don't, so it doesn't. Also if you bend the elbow prior, how would that change things? The bend is still there so the asymmetric strain in your example remains.

At this point I would like to remind you of Occam's razor and the dangers of inventing complex elaborate theories just to explain your point of view.

What...?

Now now, there's no need to get insulting. That's uncouth. Also gives you a convenient way to ignore the arguments you can't refute.

You may also have quoted the wrong post?

Cyccomute is a thoughtful and experienced mechanic that I happen to disagree with at times.

You are a sophisticated troll whose interest I mistook for wheelbuilding, when it is actually just the thrill of disparaging an actual expert as they attempt to help people. The last time I encountered this kind of conversation, it was on a fiction writing forum with a Finnish man with aspergers. Go figure.

You are a know-nothing that makes the internet a worse place than it could be. I apologize to everyone reading this for allowing myself to debate someone so deceptive that they are inventing fake musical physics in their quest to one-up. I feel foolish to have fallen for your attempts, but I always assume people are essentially motivated by interest and knowledge until they are revealed as something else. My mistake.


In the future, your spam will be largely ignored, and people will not seek your advice on anything, because you have none to give.

Well, I personally feel all that is uncalled for. There's no need to get so insulting and derogatory. But I suppose it is understandable. This is a passion of yours and it surely stings when you realize you've been doing things wrong all along. Usually the insults come out when one realizes they have no arguments left and they've been proven wrong.

But maybe this can be a learning moment for you. A chance to get better and improve. Perhaps your future wheels will be even better. I wish you good luck on your future bicycle mechanic endeavours.

This is good stuff. I like how you have subtly insulted my background, skills, training and accomplishments throughout the thread, but are now clutching your pearls. Your consistency and dedication to your craft are laudable.

How's that bend test coming?

Maybe you should go do other things for a while. I don't think hanging around this thread is doing you any good.

Maybe you two people should argue via PMs so the rest of the forum doesn't have to slog through this.