Cycling UK Forum

531colin wrote:

interestedcp wrote:.......... when the spoke untwist the spoke tension may go out of spec ...............

No. You turn the nipple. If the nipple binds on the spoke, then the spoke twists. When you stress the wheel, (or ride the wheel) and that spoke is (partially) un-loaded, the nipple twists in the rim.
The only way the spoke tension can be altered is if the nipple binds on the spoke when you tighten it, but then mysteriously binds on the rim when the spoke un-winds.

as I said at the outset, a badly-built wheel may ping, and it may also go out of true, but they are not cause and effect.

It doesn't make sense at all to me.

If a spoke is twisting while the nipple is turned, the spoke tension is increased; not because the spoke have elongated because it has been stretched when advancing up the thread, but because it has been physically twisted, and therefore has become "shorter" as measured between the flange hole and the nipple seat.

Since the effective length of the spoke has become shorter by twisting, it logically follows that the effective spoke length will be longer when the spoke untwist again; this is also true if the nipple is rotating synchronously with the untwisting spoke, since thread engagement is unchanged but effective spoke length is increased by the untwisting.

I think it is rather obvious that spoke unwinding will reduce spoke tension. So does Jobst Brandt in his his book (page 50), and Roger Musson in his; "Professional Guide to Wheel Building": v. 6.02, p. 95:

The first few pedal strokes.
If you hear a tinkling sound then the spokes had some twist in them that should have been released in the building process. If you hear that sound on other people’s wheels it tells you the builder didn’t understand spoke twist. The spokes should not make a sound. The sound comes from movement of the nipple at the rim interface or within the spoke threads. That movement will likely change the nipple thread engagement and cause the wheel to lose a bit of trueness.

That spokes twist when tightening them and that backing off when tightening the nipple helps with releasing spoke wind up, is easily observed by attaching a tape flag to a spoke before tightening it. (see Jobst Brandt: The Bicycle Wheel, p. 50).
Also, this video at around 1 minute: https://www.youtube.com/watch?v=72UfDNLM2FQ&hd=1

interestedcp wrote:............

Since the effective length of the spoke has become shorter by twisting,...............

Can you put a number on that?
If you twist a spoke say, half a turn, how much shorter does it get compared to something we know about, like the pitch of the nipple thread?

EDIT...or, failing that, take a wheel. Mark a number of adjacent spokes the same side of the wheel, and wind 'em up as much as you can (how much is that , BTW?).
....How far out of true is the wheel now?

531colin wrote:Unless the nipple is corroded onto the spoke, a round spoke will not twist enough to have any real effect. (flat spokes twist much more)
I agree its good technique to "tighten the spoke to a bit past where you want it, then back off a bit", otherwise its difficult to make a small adjustment with any accuracy, and its much quicker to fit the key to the nipple if all the nipples are accurately aligned and don't twist by themselves.....but the sky won't fall down if you omit to do it, and its far from the most important thing in wheelbuilding.

This is funny I was in complete agrrement with 531colin in a previous post and now I'm not.

I don't agree with the comment that round spokes don't twist enough. I think they do and more so with thiner spokes such as the Sapin Laser, more than the racer or the DT equivalent.

On another post that I just read 531colin makes an interesting comment 'oil can be a double edge saw' I don't think Roger Musson mention this but I would like to investigate this further, on paper this makes sense to me.

531colin wrote:

interestedcp wrote:............

Since the effective length of the spoke has become shorter by twisting,...............

Can you put a number on that?
If you twist a spoke say, half a turn, how much shorter does it get compared to something we know about, like the pitch of the nipple thread?

EDIT...or, failing that, take a wheel. Mark a number of adjacent spokes the same side of the wheel, and wind 'em up as much as you can (how much is that , BTW?).
....How far out of true is the wheel now?

I doubt whether you could measure the length difference between a spoke twisted half a turn and one that is untwisted it would be that small.The`pinging`is the nipple rotating in the rim with the spoke i assume, an argument for using washers under the nipple as you would under any nut on a bolt.
That`s my two pennies worth

To add to this discussion I would recommend the booklet Building Bicycle Wheels by Robert Wright. Mine is a 1977 publication and it is available with abe books. It is not as detailed as the Brandst book ( only 46 pages) but still a good book.

I just had a go at a front wheel build this weekend, and followed Sheldon Brown's webpage. Except, I didn't quite.

I decided that I wanted the trailing spokes heads-in (don't ask me why) whereas Sheldon had the trailing spokes heads-out (supposedly better for rear wheels), so I followed all the instructions in order, otherwise working around this point.

Then I got to the last set of spokes (leading spokes, heads-out), and realised there was no way I could get the spokes laced in without quite a bit of bending. Fortunately, the other spokes were loose enough for this to work, but the last eight spokes definitely got a bit bent beyond their elastic limit.

So, the lesson is, don't end on heads-out spokes!

edocaster wrote:I just had a go at a front wheel build this weekend, and followed Sheldon Brown's webpage. Except, I didn't quite.

I decided that I wanted the trailing spokes heads-in (don't ask me why) whereas Sheldon had the trailing spokes heads-out (supposedly better for rear wheels), so I followed all the instructions in order, otherwise working around this point.

Then I got to the last set of spokes (leading spokes, heads-out), and realised there was no way I could get the spokes laced in without quite a bit of bending. Fortunately, the other spokes were loose enough for this to work, but the last eight spokes definitely got a bit bent beyond their elastic limit.

So, the lesson is, don't end on heads-out spokes!

+1 for Sheldon
I built a rear 130mm OLN wheel fairly recently that had DS trailing spokes heads out and NDS trailing spokes heads in! First time I'd done that and it took a bit of juggling how to lace the spokes like that. The reason? The 126mm wheel it replaced was laced like that. I presume the reasoning was to create a more even sideways pull on the wheel

I find Sheldon's wheel building page gives you all the basic information you need to know to start with, and it's easy to follow as well. I subsequently bought Musson's book but didn't find much additional information and to me it seems to have, what I can only describe as, "opinionated" style.

I think the initial concerns with my first wheel build were "is it safe?" I'm light and the rim relatively sturdy so I don't suppose that wheel was highly stressed, but nevertheless I first rode it some miles on a rough surfaced off-road track. Nothing dire happened and the wheel did not go out of true, even though I subsequently decided the spokes should be tighter.

Perhaps for a first wheel build don't try to build one with a narrow rim and minimum spokes especially if you are heavy??

Musson for me,great book,practical,informative and simple to follow.I don't build wheels often enough to be able to without the relative pages by my side.
I always lightly oil spoke threads by putting a bit of oil in an aerosol can top cover getting all the spoke thread ends level and dipping them in,then tapping any excess off.
I also lube the inside of eyelets with a cotton bud dipped in the same oil.
The most important part of wheel building IME is to get the spokes at a reasonably similar tension when the wheel is true,which I 'measure' by tone when tapped with a screwdriver blade or plucked.
And to stress relieve,at least twice when the wheel is finished,I get quite brutal grasping two parallel spokes on either side simultaneously and really squeezing wearing gloves so it doesn't hurt my arthritic hands.
During building I also bend the 'outside' spokes(heads inside)inward when they're slack so they have a more direct pull and don't bind on the hub flange,again I can get quite brutal with them.

My wheels(five pair) so far have been as good as any I've bought built by pros,and as my LBS owner said to me ''yours will most likely be as good if not better,as you won't be constrained by time and you'll want to get things as perfect as possible''
As someone said up thread I've time on my hands and so take time to enjoy the experience .

531colin wrote:..............
EDIT...or, failing that, take a wheel. Mark a number of adjacent spokes the same side of the wheel, and wind 'em up as much as you can (how much is that , BTW?).
....How far out of true is the wheel now?

Anybody else tried this yet?
I did 2 front wheels this afternoon.
Put the wheel in the stand. True critically....no more than a quarter turn on a few spokes, for either wheel.
Spin the wheel and stop it randomly.....attach a tape "flag" on the spoke nearest my hand, and also on its 5 neighbours on the same side of the wheel.
Then wind-up each spoke until the nipple starts to turn on the spoke.....of the 12 spokes I "flagged" one or two got close to 1/4 turn wind-up before the nipple started to turn on the spoke, the others wound-up less, some much less than 1/4 turn.
With 6 adjacent spokes wound-up on the same side of the wheel, I couldn't see any effect on trueness of either wheel.

About the wheels....first wheel was off an Orbit Gold Medal, I didn't build it , it was built several years ago(presumably by Orbit) although only recently brought into use, ridden for 2 or 3 summers. Campag. "Topaz" rim, butted stainless spokes (I couldn't see any branding) brass nipples looked like ACI.
Second wheel, Rigida Snyper rim, Sapim butted spokes and brass nipples, recently downgraded from my winter bike to my pub/shopping bike, so its seen a few winters.
I don't lubricate the threads, so the most that wheel had was a drop of engine oil on the nipple/eyelet interface.

If my old winter wheel winds-up 1/4 turn or less, I can't see how a new wheel being built with new spokes and nipples would wind-up a turn and a half.
So, I repeat, wheels "pinging" when you first ride them isn't a problem in itself, its just the spokes un-winding, and the spokes can't wind-up enough to change their effective length. (Of course, badly-built wheels may ping and also go out of true, but going out of true is due to something else, like a lack of stress-relieving.)
I agree spoke wind-up is best avoided as its easier to make small adjustments (1/4 turn) and to put the key straight on the nipple if all the nipples are orientated identically, but in the great scheme of things, spoke wind-up is a minor inconvenience, not something of major importance.

MikeF wrote:I think the initial concerns with my first wheel build were "is it safe?" I'm light and the rim relatively sturdy so I don't suppose that wheel was highly stressed, but nevertheless I first rode it some miles on a rough surfaced off-road track. Nothing dire happened and the wheel did not go out of true, even though I subsequently decided the spokes should be tighter.

Perhaps for a first wheel build don't try to build one with a narrow rim and minimum spokes especially if you are heavy??

The hard part seems to be working out if there's enough tension, without a gauge. The trick of plucking spokes for tone only works if comparing against the same wheel size and spoke type (plain gauge vs double butted). I think I've got the tension to where I need it, but the temptation is obviously to crank it up further.

breakwellmz wrote:

531colin wrote:

interestedcp wrote:............

Since the effective length of the spoke has become shorter by twisting,...............

Can you put a number on that?
If you twist a spoke say, half a turn, how much shorter does it get compared to something we know about, like the pitch of the nipple thread?

EDIT...or, failing that, take a wheel. Mark a number of adjacent spokes the same side of the wheel, and wind 'em up as much as you can (how much is that , BTW?).
....How far out of true is the wheel now?

I doubt whether you could measure the length difference between a spoke twisted half a turn and one that is untwisted it would be that small.The`pinging`is the nipple rotating in the rim with the spoke i assume, an argument for using washers under the nipple as you would under any nut on a bolt.
That`s my two pennies worth

If you were to make spokes out of (say) string then they would get shorter when they see an elastic torsion strain. BUT because they are made of nice, essentially isotropic steel, they don't change in length when they see small elastic torsion strains. Provided you don't start to flirt with Von Mises, (which you shouldn't do...) axial elastic stresses do not interact with torsional ones.

When spokes go 'ping' and any residual twist unwinds, the spoke and the nipple together can turn in the rim or the spoke can turn in the nipple. It all depends on the friction in each interface. In the latter case this may alter the truth of the wheel.

However with most spokes this is unlikely to be more than 1/4 turn on any one spoke and most modern touring rims don't move much if at all if you move one spoke 1/4 turn. However if you build with a very narrow/shallow lightweight rims this is no longer the case. If you also lubricate the spoke threads (but not the nipple seat) and/or the nipples sit an angle in the rim (and therefore bind more than normal) then the spokes may consistently unwind in the nipples rather than the nipples turn in the rim.

Note that both interfaces may exhibit a stick/slip characteristic, whereby the static friction is a good deal more than the dynamic friction. This can allow a spoke/nipple interface to bind when the spoke is tensioned, but unwind a lot more than this when it finally moves. This is in addition to the reduction in static friction when the spoke tension is temporarily reduced in service (which is what provokes the pinging).

So the bottom line is that with even the most modest care to avoid residual twist whilst building a wheel with a stiff rim, pinging and consequential truth changes are not likely to be anything to worry about. I certainly wouldn't worry about that in my first wheel build, there are much more important things to get right than that, and if it is any kind of a real problem (unlikely) then you can fix it later on, very easily.

By contrast you can't so easily detect and/or rectify more basic problems to do with poor component choice, or poor fit between spokes and hub, or a failure to set the spokes to avoid residual bending stresses, or a failure to stress relieve. These things should be the focus of attention, not pinging!

BTW I have found plenty to disagree with in every book on wheelbuilding. For example Roger Musson maintains that current DT spokes have an elbow length that matches typical hub flange thicknesses very well; I do not agree.

cheers

i like gerd schraner's book "the art of wheelbuilding." with the advance into the market of machine built examples i wonder whether the art will one day die out though.

mig wrote:i like gerd schraner's book "the art of wheelbuilding." with the advance into the market of machine built examples i wonder whether the art will one day die out though.

My background is in software development but I also build wheels. I haven't read much about what type of machines exist ATM but I do know that there are machine and man combination building wheels and that there are machines that do the building alone. I also know that what they produce is not as good as the wheels built by good wheel builders.

I think we currently have and have had for a long time all the technology required to build wheels that are as good if not better than any top wheel builder.

For a moment I go back to my days at university and learning about Artificial Intelligence, robotics and expert systems and I wonder why nobody has built a machine that build the almost perfect wheel (assuming such a machine doesn't exist). I had never give it much thought but right now I find it hard to think what is preventing such a machine. All the techniques and good practices already talked about can be tought to a robot and there is the technoly to support visual aid, tension measuring, tone reading, etc.

Whether the "art of wheelbuilding" will die out or not it's difficult to say. Some people will continue building their own wheels just for the pleasure of riding their own wheels. Othe people like custom built things like custom build shoes , etc. It's safe to say that it will not be the same as it's now.

In about 2004 there seemed to be machines that would stress-relieve, for example.......http://forum.ctc.org.uk/viewtopic.php?f=5&t=49702&hilit=spokes&start=60

i really hope the skills (and readily available spare parts) don't die out. ditto for small framebuilders. all mass produced frames/wheels just lack 'soul' to me. whilst i realise most bicycles are tools for a job i do like that element of true passion being put into one on top of that element of pure functionality.