Recycling Bicycle Spokes

Er, ?

One of the questions I have about what Jobst says is whether it would be an issue to remove spokes from their wheels and use them in new wheels if you kept track of which were inbound and which were outbound. This would cause some change in what form they would optimally be set to coming out of the hub, but usually not very much (although I could think of some instances where it may be more considerable). I think one would need to answer some questions here to take spoke re-use to extremes. I have a bunch of spokes that have been in previous wheels of mine that I've unlaced and put in bunches that says "296-outer", etc, but I haven't started experimenting with this yet.

It should be noted that Jobst is talking about quality, stainless steel spokes that were stress relieved by the wheelbuilder to begin with. Spokes that have never been stress relieved can be assumed to have accumulated some amount of fatigue, weakening them and (by my understanding) possibly putting at least some spokes beyond the point where stress relieving them now will prevent breakage in the future. So if you start re-using lots of spokes from random wheels, some (perhaps many) will break eventually even if they get stress relieved at the start of their new life.

Re-using non-stainless spokes of any kind is probably not worth it - you're likely to run into corrosion problems on most of the wheels you'd be getting them from, and you can pretty much assume none of them have ever been stress relieved.

As puns go, not the worst one ever coined.

Funny I thought the guys at

were being overly cheap when they recycled spokes,I know better now.

It is always interesting to read about things like high end electronics and high cost bicycle equipment.

When one buys new spokes, do they come in two packs, one for inbound and one for outbound? My guess is that they do not. There is not a lot of difference in the angle. What would be an interesting experiment, would be to lace up a wheel with used spokes. And lace it with half of the wheel having spokes where the used inbound spokes are used for inbound and the used outbound spokes are used for outbound. But with the other half of the wheel laced where the used inbound spokes are used as outbound spokes, etc. One could use the valve hole to keep track of which side of the wheel had the position preserved.

When bike spokes fail, do they normally fail at the hub end? Or do they fail at the threaded end?

I am also interested in how the wheel builder stress relieves spokes. And does an additional stress relief after some use affect the fatique life. I would think that one could increase fatique life by stress relieving before ever using something, but question whether performing an additional stress relief after some amount of use, would add to the fatique life.

Dan

Nate, what do wheel builders mean by "stress-relieving" spokes? What is the process they use?

-- Ed Huntress

There are many, many descriptions in the archives of this group.

There is considerable difference after the wheelbuilder deliberately changes the angle of the outer spokes at the hub.

Okay...the consensus is in 6 replies visible is that stainless is the thing to recycle for sure, and we have some debate on whether inboard and outboard spokes should be separated for reuse.

I am thinking S-bend spokes would be highly recyclable. Nip to length, form new bends, and reuse. There'd be no need to own or operate a threader. Just a pair of special pliers, quick and easy. Preserve the threaded end.

The Eldi Emergency Spoke Tool, no longer available, comes to mind. I'm looking around for a 14-15 gage S-bend plier tool. I have found a 15 gage tool used by model airfcraft hobbyists, and ordered it. There is a Z-bend tool used by hobbyists for wire to 0.062. Spoke wire sizes are

0.072 and 0.081, I think.

Would universal use of straight gage S-bend spokes instead of headed spokes be a change that would encourage recycling of spokes, rims, wheels, and bicycles? Recycling is big with bicyclists. Would it also provide a safety problem? Do such spokes eventually unbend or loosen? Would S-bend spokes work with automatic wheel builders? It seems that they would be easier to use with such equipment.

Some artists recycle spokes into craft productions like bracelets, key rings, etc.

Do double-threaded spokes recycle well? Was that the intent for that variety, or was there another reason?

The Dougster (I) wrote:

I looked at the rec.bicycles.tech use group briefly and found that "Stress Relieving" in the bike world seems to mean cold forming to improve alignment. My ideas of stress relieving aren't close to theirs. I was picturing using a torch to heat the spokes and wondered how they controled the process.

Dan

In that case I would think one would not need to keep track of which were inbound and which were outbound. It would be obvious by merely glancing at the spoke.

Dan

Dear Ed,

Sitting in front of a wheel in a truing stand, grab two pairs of spokes, one pair with each hand, and squeeze mightily. Wearing gloves is recommended.

A pair of spokes should be roughly parallel, not crossed.

The nipples of the four spokes should run down the rim A-B-C-D, with A & C being squeezed with one hand, and B & D being squeezed in the other hand.

The theory is that this raises the spoke tension enough to relieve residual stresses from bending the spoke elbow during manufacture and then the slight bending if the spokes are bent to lie against the hub flange and to exit the rim at a slightly different angle.

Believers emphasize that this is not merely seating the spoke nipples and elbows at the rim and hub.

Despite sincere belief and anecdotes, there are no reports of any spoke testing that confirms or refutes the theory.

The lack of controlled testing (as opposed to anecdotes) leads to frequent debates on RBT. Unfortunately, automated fatigue testing of spokes is an incredibly tedious and lengthy business.

The only spoke fatigue tests that I know of were performed over 20 years ago at Stanford for WheelSmith, but did not compare squeezed to unsqueezed spokes:

Of the 76 spokes tested, 68 broke at the elbow, 8 at the threads. Testing was stopped because it had taken two months, which gives you some idea of how tedious it is, particularly since road test stress ranged from 20 to only 150 MPa, while the test stresses started at

174 MPa and reached 501 MPa.

The first formal description of spoke-squeezing for stress-relief came in 1981 in "The Bicycle Wheel," by Jobst Brandt, a frequent poster on RBT.

Twelve years later, Jobst wrote in the third edition of his book:

"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

In other words, some improvement in spokes had made spokes so much more durable within a decade that Jobst himself thought it would be difficult to discover his theory "for lack of failure data"--not that there is any data in the sense of results from controlled testing.

I waver between believing and doubting the theory that squeezing spokes by hand relieves internal stresses.

Recently, I wasted a lot of time measuring the actual tension increase in squeezed spokes.

Contrary to ad hoc theories that a modest squeeze force must produce a large tension increase, it appears that 32 and 36 spoke rims of ordinary construction deform in a faint M or W shape when squeezed in the traditional fashion because the top and bottom spokes of the A-B-C-D pattern are pulling largely unopposed in opposite directions.

To boil the uselessly detailed statistics down, a one-handed 60-pound squeeze force on spokes A & C and a simultaneous one-handed 60-pound squeeze force on spokes B & D raises the tension of each spoke only about 55 to 65 pounds.

Squeeze forces greater than 60 pounds tend to leave faint, permanent bends in the spokes. The dramatic bend angle fooled many people into thinking that the spoke tension increase must be enormous, with calculations estimating that a gentle 30-pound squeeze force would raise spoke tension an impressive 150 pounds, instead of the measured tension increase, which is actually often under 30 pounds.

From a practical point of view, no one claims that spoke-squeezing hurts anything. Even those who doubt that it relieves residual stresses emphasize that spoke-squeezing is necessary for seating and bedding the spokes.

It's one of the regular topics for debate on RBT.

Cheers,

Carl Fogel

Dear Dan,

Whew! Glad that you checked before experimenting.

Despite the flames that accompany the topic, pairs of spokes are squeezed together to raise tension, not toasted.

Posters who believe that squeezing spokes together raises tension and relieves residual stress might disagree with your description of the process as "cold forming."

They do bend/cold-form the spokes to get the spokes to lie flatter against the hub flange and to change the entry angle at the rim. These bends are visible.

But I think that they see this as entirely different from squeezing the spokes together to raise tension in hopes of relieving residual stresses. Spoke-squeezers often emphasize that this is a microscopic change, and they insist that it is not cold-forming.

"Cold-forming" tends to suggest "strain hardening," which is sometimes a sub-topic in the debate. In general, spoke squeezers say that what they do involves stress-relief, not work or strain hardening, and is entirely different from bending things to improve the spoke line.

Cheers,

Carl Fogel

I was thinking the same thing. Thanks for passing that on, Dan.

-- Ed Huntress

Sometime I have to look into this. As the former materials and heat-treating editor for metalworking magazines, I have to see how they claim that any kind of cold work is going to relieve stress in any grade of steel -- with the single exception of high-frequency vibratory stress relief.

I don't doubt that it does something useful, but relieving internal stresses at a "microscopic level" by low-frequency cold work of any kind would be a new one in the world of metallurgical science.

Artisans in a number of fields use the term "stress relieving" differently than engineers and scientists do. There's nothing wrong with that but it does lead to some confusion.

-- Ed Huntress

Both physical measurements, and "ad hoc" calculations can produce erroneous results. But certainly a force applied perpendicularly to the spoke can increase the stress in the direction of the spoke considerably. I tend to doubt the accuracy of your measurements more than the basic physics.

I recently found an old whell in my back yard. about 15 inch diameter. Hard rubber, hollow, non pneumatic tire. Looked to be from a garden cart or something so I thought I would build a wheelbarrow around it. I did that. It works fine. I was quite proud of myself for wasting an hour that way. However, said wheel was really out of true. The spokes were non adjustable, solid wires from hub to rim. Some spokes were bent so I went at them with a small hammer. Carefully tapping them back to straight, listening for the tone each made. Sure enough, when they were all straight and rang out about the same, the wheel was very straight. I have in my hands a pair of spoked wheels about 1.5" diameter that were made by Fulton Hungerford for very small lightweight rubber powered model planes. The tires are balsa, hubs are nylon tubing, and the spokes are silk thread. Really tight light and strong. Very authentic on a ww1 era model

I am pretty much of the " if it ain't broke, don't fix it " school so there wasn't much chance that I would be getting out the torch. At least not until I had multiple spokes break.

I used cold forming to mean changing the shape without cutting or using heat. So it my mind if there is a visible bend made without applying heat, it was cold formed and now almost surely has more not less residual stresses.

Dan

Dear Ed,

A common analogy is to "scragging" or "bulldozing" coil springs--squash 'em down hard, and see the stress relief:

One problem is that if you read the captions carefuly, you learn that the data for the bulldozed springs is not actually given, though it's said to be "essentially the same"--the pictures are for heat treated springs.

Another problem is how much extra tension or compression is involved. The coil springs are usually mashed flat.

General theory on RBT held that the impressive bend angle produced by squeezing spoke pairs must indicate even more impressive tension increases.

But when I measured the actual tension increases, it appeared that the rim deformed far more than expected, rendering calculations based on angles and an unchanging distance between the rim and hub useless.

That is, good-faith calculations based on the bend angle produced by a

30-lb squeeze force on a single spoke's midspan indicated that a 250-lb initial tension rose about 150 pounds, to 400 pounds. The calculation assumed a basically fixed distance between the rim and hub.

But when I measured various rear and front wheels, 32 and 36 spoke, with and without box section, eyelets, and sockets, I found that a

60-lb squeeze force on each of two pairs produced tension rises of only about 55~65 lbs.

With two spokes A & C pulling the rim to one side, and two spokes B & D pulling the rim to the other side, the rim probably goes into a faintly Z, S, N, M, or W zigzag shape:

B D_________ _________/\/ A C

The ASCII exaggeration above is huge. The shape could be more like this: D________ B__/ _________/ C A

Given the extremely stiff materials and tiny range of elasticity, it's understandable that the deformation wasn't noticed. If you tape a spoke flat against a rim at a tangent, you can sight along the spoke, squeeze a spoke or two near that rim section, and see the spoke swing in or out as the rim starts to zigzag.

Discussion of spoke squeezing usually becomes quite vehement.

As far as I know, the theory is unknown in spoked motorcycle and sports-car wheels, but they may use such massive spokes that bicycle-style problems are masked.

Some wheel manufacturers use presses to seat spokes and may claim that it's stress-relief akin to squeezing all the spokes at once, but as far as I know, they release no data, and posters who cite such practices as proof of stress-relief routinely scoff at other manufacturing techniques as marketing-driven superstition.

Cheers,

Carl Fogel