Recycling Bicycle Spokes

Thanks for your detailed explanation, Jobst, and for the link. I think I follow you and, as I said to Carl, what's important here is less the analysis than the practice, and I defer to your experience with that.

You may be interested that back when the first edition of _The Bicycle Wheel_ was published I showed it to my fellow editors at McGraw-Hill as an example of what I thought was the new trend in how-to books, which I found interesting and kind of exciting. Your book, a flood of new boatbuilding books, a few car books, and the new publications from Taunton Press were the key examples of a new generation of well-edited, precise, and expert specialized publishing oriented toward personal, avocational interests. I think your book still stands as a fine example of the breed. Oh, BTW, I built two wheels for my wife's bike from your instructions back then (that's why I bought the book), and they came out well for a rank amateur.

Back to the issue, I had some time to think about and research this subject, and I see a few issues that I'd like to resolve before saying I really understand it. I also think they would require some measurement and research that I have neither the time nor the inclination to do.

For example, it seems unlikely to me that your method for "stress relieving" spokes would stress all parts of a bend into plastic deformation, although I can see that it might be possible. Whether the outside AND the inside of a bend were relieved would seem to depend on whether the final angle of the bend, with the spoke in use, was greater or lesser than the angle it assumed after initial forming, when the stress of the initial bending was removed. As one of the engineers quoted in your link says, the plus- or minus-sign of stress on such a bend reverses after the initial bending stress is removed (the outside of a bend actually is loaded in compression, which is counterintuitive unless one thinks through the process). If you don't change the final bend angle when you "stress-relieve" the spoke after it's mounted on the wheel, you may exceed the plastic limit on the inside of the bend but you probably won't exceed it on the outside, unless you subject the whole spoke to quite a lot of strain. As you know, you first have to take up the compressive stress on the outside of the bend, at which point you've strained the inside of the bend quite a lot -- unless, of course, the bend angles change.

And they surely must change, but how much, and it which direction, I won't guess.

I'd like to see some kind of measured results, but this obviously remains a controversial issue among cyclists and I don't have the time or inclination to dig deeper into it. For whatever practical use I may make of this information, I'll defer to the experience of the experts and just follow that...for the same reason I wouldn't perform a surgical operation on myself.

Regards,

-- Ed Huntress

Thanks for the positive assessment.

The intent is to reduce stress at those points where spoke tension has been added to residual tensile stress. We don't care about compressive loads because the must be lower just by the added tension and by "improving the spoke line". As I mentioned, spoke elbows are at an obtuse angle when manufactured. Bending them into an acute angle for outbound spokes adds tensile stress to the elbow. This stress is reduced by over stressing the spoke in tension.

That goes under the assumption that the angle is opened to an even greater obtuse angle. This does not occur in common hubs.

The changes when stress relieving are microscopic and do not measurably change elbow angle. What occurs is that tiny areas on the skin of the spoke exceed yield if they were close to yield and are thus stress relieved. That will not change the shape of the bend. The same is true for threads.

The best example I can give is the spoke in the tensile test that comes out perfectly straight when its shaft reaches yield yet with essentially no measurable elongation by not continuing when the stress strain curve begins to flatten. That is because only the outer surface of the spoke has residual stress and the rest of the spoke did not reach yield.

The measured results are that wheels using elbow spokes are all stress relieved by the major manufacturers. Spoke failure has been reduced to poorly built wheels.

Jobst Brandt

Dear Jobst,

Please list the "major manufacturers" who stress-relieve their wheels and when they began doing so.

As far as I know, none of them have ever released any fatigue test data.

Do you consider this more important than the "better spokes" that you credited with vast improvements between 1981 and 1993?

"It appears that the better spokes now available would have made the discovery of many of the concepts of this book more difficult for lack of failure data. I am grateful in retrospect for the poor durability of earlier spokes. They operated so near their limits that durability was significantly altered by the techniques that I have outlined."

--Jobst Brandt, "The Bicycle Wheel," 3rd Edition, 1993, p.124

Cheers,

Carl Fogel

I mentioned TREK as one who support whees on a rim support and hydraulically push the hub laterally out of center with a designed load. The wheel is then turned over and the operation repeated. This method works ideally because it does not overload the rim in hoop stress, one set of spokes becoming looser while the other, tighter. It also does not cause any local rim distortion.

Why should they? You haven't seen any such data for spokes, chains, bar stems, cranks, seat posts...

You keep repeating this jim beam mantra. It has been answered often. Where did I write "vast improvement"?

As you may have noticed, we still get reports from people with wheels whose spokes break; wheels not purchased from TREK for instance. At TREK, Damon Rinard oversees this process. You may recall reading his contributions here on wreck.bike before he went to TREK.

Also, some wheels now use straight pull spokes (no elbow) that can be stress relieved during manufacture after head and threads have been formed, the spoke form not being altered in wheel building.

You must have given the straight pull spoke some thought. It is not without reason that manufacturers went to that design in spite of better steel spoke materials. Many did not realized the cause of spoke failures and took the obvious route of eliminating the elbow, while at the same time making a more complicated and expensive hub. Since today's bicyclists seem to be rich enough to afford these wheels, we hear few complaints. The $50 wheel is long gone and so are simple sturdy rims that aren't welded, anodized, and machined; ones that worked perfectly with thousands of miles use.

Jobst Brandt

Dear Jobst,

So your list of major manufacturers and the dates when they began stress relieving reads like this:

date manufacturer

1. ???? Trek

As for the vast improvements, that's a reasonable description of the quote from your 3rd edition, the one that you ignored while claiming that it was somehow Jim Beam.

You don't seem to distinguish between the spoke improvements that you wrote about in 1993, the ones that would have made it difficult discover your "concepts," and your new theory that "major manufacturers" are stress-relieving their wheels.

Are you saying that Trek wheels need no stress-relief, but that all other wheels do? The question is serious, since you seem to have come up with a new approach.

Cheers,

Carl Fogel

Someone piss in your wheaties?

Ron

Dear Ron,

No.

But someone did write that major manufacturers do something.

So I asked who they are and when they started doing it.

A long answer tended to obscure the lack any dates and a list consisting of only one manufacturer.

If anyone has a list of major manufacturers that do what Jobst claimst they do, that would be interesting.

Even more interesting would be when they began doing it.

Did they begin doing it before or after 1993?

That's when Jobst added a note to his 3rd edition that improvements in spoke quality (presumably since his first edition in 1981) would have made it much harder for him to come up with his theory.

So is the improvement in spoke durability due primarily to better spoke quality, to what unnamed major wheel manufacturers do after they build the wheels, both, or what?

What would you expect the response would be if I were to write that major manufacturers are doing something and that what they do proves some favorite point of mine (whether it does is another matter) . . .

But I failed to name more than one manufactuer or give any dates when they'd begun doing it after I was asked to please list them?

Cheers,

Carl Fogel

That a thing is a favorite point of yours, whether proven by the actions of manufacturers or not, does not mean that it must be important to me. He does seem to not go on about the subject quite as much as you.

Trek / Bontrager - a fairly successful outfit - known to be pretty solid in the engineering department - seems to agree that this is a necessary step in wheel production. Is that sufficient to prove that Jobst isn't just some crank with an Art Bell theory? Probably. Was there any other major question in play?

Here's a guy who has this empirical data on building wheels, he's developed procedures from this that lots of people use to build wheels that make them happy. And ... what? Okay, he's an ass, and rude besides. And ... ? Spokes are better than previously. So ... ? Yeah, he thinks he knows more about puncturevine than you ... ?

If it makes you happy, don't squeeze your spokes. That'll show him.

Ron

Dear Ron,

Actually, we take turns provoking each other about our (not just mine) favorite subject.

No, it's not sufficient to say that someone else does it--everyone used to tie and solder spokes.

And no, even if Trek does squeeze spokes with a press, it doesn't show whether it does any good unless there's some data, as opposed to alleged data.

And no, even if spoke-pressing did produce greater durability, it still wouldn't show whether it was due to microscopic stress relief or to better seating.

In any case, my question still stands. Jobst now claims that "major manufacturers" are squashing spokes, but when asked who they are and when they started, he came came up with four letters and no numerals in a long and evasive post:

date manufacturer

1. ???? Trek

If you or Jobst or anyone else knows of other manufacturers, that would be welcome and interesting news. But until then, the lack of names and dates makes the claim look a bit like myth and--

Well, you get the idea.

Cheers,

Carl Fogel

They tell me that if you move one more ring inward you get to literally gnaw on each other's limbs.

I'll bugger off now.

Ron

Dear Dante,

S?io credesse che mia risposta fosse A persona che mai tornasse al mondo, Questa fiamma staria senza piu scosse. Ma perciocche giammai di questo fondo Non torno vivo alcun, s?i?odo il vero, Senza tema d?infamia ti rispondo.

Technically, it's another ring downward.

Say hi to Beatrice for me.

Cheers,

Guido M.

I made it out once.

Ron