Thought some of the comments from an earlier
thread on wheel building might be beneficial so I've copied them into this one.
Dean
Mick F wrote:
Rigida Chrina rims in anodised silver, 32h front and 36h rear.
Campagnolo Chorus hubs.
ACI Stainless Double Butted spokes but with Plain Gauge on the drive-side rear.
All shiny and new!
since you bring it up...
I've seen this mentioned a few times - what's the advantage?
Mick F
Good question.
Stronger spokes on the drive side are required as they are under a great deal more tension than the non-drive side. This is because of the severe 'dish' of a road wheel - especially with a Campag hub.
The drive-side hub flange is not far from the centre-line of the wheel, making the spokes appear almost vertical.
I haven't seen the maths behind it, but a spoke that is thinner must be stretchier and weaker than a thicker one.
Look at the links to Spa and read the descriptions:
http://www.spacycles.co.uk/products.php ... b0s156p494 Plain Gauge - Ideal for drive sides for lighter wheelsets.
http://www.spacycles.co.uk/products.php ... b0s156p533 Double Butted - Ideal for front wheels and non drive sides of wheels.
The DB spokes are 2mm thick at each end, but only 1.7mm thick for the majority of their length. The Plain spokes are 2mm throughout.
Please don't think I'm any great expert, I'm very much in the learning stage. I'm good with my hands and enjoy tinkering and learning new skills. I started out by pulling apart a old set of wheels and re-building a couple of times until I got the hang of it. All you really need is a good spoke key and your bike frame as a jig.
Oh, and a good eye!
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Mick F. Cornwall
pigman
interesting re the plain gauge spokes on one side, but I cant see the point of having the excess meat in the centre of the spoke. My experience of breakages has been at the hub end, where DB or not, there is 14gauge metal. (im not disagreeing, just dont understand)
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Steel is real, the rest is second-best
Mick F
Spambuster
Maybe someone more experienced could enlighten us!
I know that the thicker the spoke, the stronger the wheel. Also, the higher the spoke count, the stronger the wheel.
As for breakages at the hook-end, I agree that that is where they usually break. I understand that you can buy spokes with very thick hooks.
What causes a spoke to break?
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Mick F. Cornwall
Dean
I was of the understanding that double-butted spokes are stronger than plain gauge, since the thinner middle section allows them to compress and spring back into shape more easily.
I'm relatively new to wheelbuilding too, so I don't pretend to be an expert. And until recently I've built exclusively front wheels or fixed wheels, which require zero dishing - hence my asking the question.
rogerzilla
I always use d/b on both sides, and have never broken (or even loosened) a spoke, except in a major prang.
Plain gauge spokes have no advantages except cheapness. There are, however, single-butted spokes which may have an advantage on the drive side, because they have a thicker elbow (the same as the major diameter of the thread, which is about 2.3 mm and only just fits through the hub spoke hole), which is where you need the extra metal.
Mick F
We await an expert!
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Mick F. Cornwall
Dean
My distinctly unprofessional approach to wheelbuilding:
Buy hubs and rims. *This is important*: Measure them carefully. Correct measurement determines the spoke length, which I have found to be the most critical factor in wheelbuilding. Using the wrong length of spokes is frustrating at best.
Lace the wheels (Sheldon Brown's site, as linked to in MickF's OP, is excellent).
Use the frame and forks as truing jigs. Blu-tack and a bit of old spoke can be used for lateral truing (making sure it runs straight), as the spoke makes a "Ping" when it catches the rim. Or you can use the brake blocks.
For roundness, you can put a tie-wrap around the frame/forks. This helps you gauge the height of the rim at any given point.
For dishing (making sure the wheel sits centrally), the cheapest way is to flip the wheel over.
Unless you're building wheels professionally, as in daily and for a living - I don't think you *really* need a truing jig or a dishing tool - all you need is the frame and a spoke key (make sure that it fits the nipples correctly).
As well as Sheldon's site, I found the Park Tools website useful on building wheels. Just ignore the bits where it says you need a truing jig, spoke tensioner etc:
Park Tools US
Roger Musson's website allows you to download his book on wheelbuilding ( I haven't yet, but I am assured that it is excellent). and it also has a free-to-use spoke calculator, and a good description of how to measure hubs and rims:
http://www.wheelpro.co.uk/spokecalc/
Is it cheaper overall? I'd say it probably is, but mostly it's more satisfying to build my own, and I'm not relying on some spotty yoof in a bike shop nwhom I wouldn't trust to hold a spanner correctly (having been that spotty yoof, I know whereof I speak).
DIY. It's usually the best way to go.
Mick F
Great!
When I made up my new ones, I laced up the front first in the manner I described.
I then started tightening a little at a time, and lo and behold, the wheel was perfect without using my frame or jig! Just sat on the settee holding the wheel and it was fine. I tensioned it in the jig later, but it was almost there!
I bet you're going to ask about spoke tension next. Not my strong subject, I worry about it a little. All I do is make sure the spokes "feel" right. Also, the nipples start to creak as you tighten them and get difficult to turn and I worry that I'm going to strip something. That's when I think it's right. I use my mechanical aptitude to know when if feels right.
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Mick F. Cornwall
lauriematt
not too worried about spoke tension.....generally you ' feel ' what the limits are
i made the mistake ( & im sure im not the only one ) when lacing the wheel - i had the correct spoke pattern but the spokes werent laced right. i tightened it up and was wondering why the spokes werent touching each other. then i realised that the spokes werent laced over each other!
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NO PAIN - NO GAIN!!!!!
PW
Tension the spokes until they feel right, then stress relieve the wheel by taking hold of parallel pairs of spokes and giving them a good squeeze in the centre - you'll need gardening gloves or it rips your palms to bits. Do each pair starting with the two pairs which bridge the valve hole. If the wheel stays true, tension it another 1/4 turn all round and repeat. Eventually it will go out of true in 4 smooth waves. Back off every spoke 1/4 turn, true it up and it's finished.
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If at first you don't succeed - cheat!!
axel_knutt
Mick F wrote:
Great!
I bet you're going to ask about spoke tension next. Not my strong subject, I worry about it a little.
I'm not sure it's anyones strong subject!
When I did my first wheel this was the one point I was unsure of, so I emailed Sheldon Brown, DT Swiss, and CJ. None of them gave a particularly straight answer so I set mine at 1kN (a mean of 1kN on the rear), which is the tension Brandt refers to as "typical". I've had no problems.
pigman
I've never been one for scientifically tightening up things with torque wrenches etc, so wouldnt know how to measure it in any definitive unit. easiest way is to check a wheel you know is good and squeeze adjacent spokes (not adjacent at the hub or rim, but in the middle where they cross) to get a gut feel. Then copy on your wheel and jobs a good 'un. as you get experienced wheelbuilding ,you wont need to copy, youll have that intuitive experience. Never failed me yet.
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Steel is real, the rest is second-best
CJ
Moderator
rogerzilla wrote:
I always use d/b on both sides, and have never broken (or even loosened) a spoke, except in a major prang.
Plain gauge spokes have no advantages except cheapness. There are, however, single-butted spokes which may have an advantage on the drive side, because they have a thicker elbow (the same as the major diameter of the thread, which is about 2.3 mm and only just fits through the hub spoke hole), which is where you need the extra metal.
Mick F wrote:
We await an expert!
I don't like to call myself an expert (ex: a has-been, spurt: a drip under pressure!) but here goes.
Spokes slacken when the bit of rim they're attached to gets pushed upwards by the road/tyre. They have to be tight enough that they hardly ever go completely slack (only when you hit a really big bump!) but not too tight, since either going slack or higher average tension will both shorten the fatigue life of a spoke.
The trouble with dished wheels is one side must be much tighter than the other. So if you use the same spokes both sides, none can be at their optimum tension. A compromise is required, which in the case of the common rear cycle wheel means the left side spokes are not really tight enough, so that one goes completely slack from time to time (frequency depending on the weight carried, stiffness of rim, bumpiness of road etc.) whilst the right side is tighter than optimum.
With modern road wheels demanding twice the left spoke tension on the right, this compromise is not insignificant.
Regardless of how far one may have ridden such a wheel without breaking a spoke, one could have ridden it further (or ridden a lighter one in the first place) if it were specified with spokes that are designed to take a higher tension in the side that necessarily has a higher tension, and vice versa.
Single-butted spokes (and others with an extra thick head section, sometimes called triple-butted) are designed to withstand a higher build tension, all other factors being equal. So they are what you really want in the right side, IMHO. In the case of a lightweight wheel I'd choose the DT Alpine-3 (so-called triple butted, but really double butted) that have a thinner 1.8mm centre section between the 2.3mm head and standard 2.0mm thread.
Meanwhile on the left you want double-butted with a much thinner centre section. Reason for that is to ensure that the spoke stretches by about the same amount as the right side spokes, in the process of tightening them to a necessarily lower tension than the right side spokes. That way, when the wheel deflects, spokes on both sides of the wheel relax in unison. An additional benefit of such "elongation matching", is that the rim does not also pull to one side as it deflects upward, so it's less likely to buckle when you hit a bump.
Whilst an entirely plain gauge wheel is less durable than an entirely double-butted, the same does not apply to the judicious combination of double-butted and plain in a dished wheel. Although the plain gauge do not have the extra-strong heads of single-butted, their greater stiffness compared to double-butted still provides all the symmetry benefits of elongation matching.
So whilst Mick might well have spent a bit more on even swankier spokes, that could have given a marginally even finer rear wheel, the combination of double-butted left and plain gauge right brings a lot of the same advantages.
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Chris Juden
CJ
Lawrie9 wrote:
Clear as mud!
Attempt at simple version:
In a typical road bike rear wheel the rim is half as far from the right hub flange than the left, and right spokes have to be twice as tight as the left spokes to pull it off-centre like that.
Or else there could be twice as many spokes on the right, as in a Campag G3 wheel, and as in all similarly dished spoked wheels on motorcars. Motor engineering apparently does not tolerate foolish design, cycling on the other hand ... but I digress.
Bike wheels are mostly condemned to have the same number of spokes both sides, even when they're dished. The response of an intelligent designer to this constraint is to use spokes that are twice as stiff on the right.
Think about what happens if all the spokes are the same stiffness and the right side ones are twice as tight to start with. As the rim is pushed up towards the hub the left spokes go completely slack first, whilst the right ones are still pulling, so the rim shifts to the right, as far as the sideways bending stiffness of the rim may allow. Push the rim hard enough and the lateral and torsional strength of the rim will be exceeded. Result: the familiar buckled wheel.
If the right side spokes are twice as stiff as the left however, the inbuilt 2 to 1, right to left tension ratio is maintained during any local reduction in spoke tension, as the rim is pushed upwards toward the hub. Rim deflection therefore remains purely radial in response to a radial load, with no inbuilt tendency to buckle one way or the other.
If the impact isn't truly square to the wheel of course, there's still some risk of it buckling. The simple wheel, admittedly, will be more resistant to leftward hits, but vulnerable to any knock that tends to push it to the right, since that's the way the radial load is sending it already.
Since there can be no consistent bias in the alignment of the edges of potholes etc.: the wheel built with tension balanced spoking, with equal resistance to random impacts from either direction, will be less likely to suffer damage.
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Chris Juden
rogerzilla
Jobst Brandt uses the term "taco" to describe the shape taken by an overtensioned wheel when it deforms to try and get out of the way of the load (probably a form of Euler failure). "Pringle" is my favourite description.
CJ
Moderator
rogerzilla wrote:
Jobst Brandt uses the term "taco" to describe the shape taken by an overtensioned wheel when it deforms to try and get out of the way of the load (probably a form of Euler failure). "Pringle" is my favourite description.
Pringle, excellent, must try to remember to use that in future. Very Happy
But even a somewhat under-tensioned wheel will go that shape if you wallop the rim hard enough sideways.
An over-tensioned wheel however, will "pringle" all by itself, whilst you're over-tensioning it Embarassed
Or, if dished with same spokes both sides, a not-quite-so-badly-over-tensioned wheel will pringle by just riding along, i.e. a radial load.
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Chris Juden
pigman
CJ wrote:
An over-tensioned wheel however, will "pringle" all by itself, whilst you're over-tensioning it
assuming that this hypothetically happens, would the rim be bent beyond repair (ie actually distorted), or would loosening "unpringle" it and leave it flat to try again?
I once saw, on a ctc invitation ride, a back wheel pringle whilst descending very carefully a 1-in-5/1-in-6 hairpin. Bike was very old & unmaintained all round and judging by the front wheel which was still intact, I'd say it was undertensioning, rather than overtensioning that caused it.
BTW what an invitation ride that was. Twas the most hilly area round Bradfield/strines/langsett - not exactly easy or endearing to joe public.
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Steel is real, the rest is second-best
CJ
pigman wrote:
CJ wrote:
An over-tensioned wheel however, will "pringle" all by itself, whilst you're over-tensioning it
assuming that this hypothetically happens, would the rim be bent beyond repair (ie actually distorted), or would loosening "unpringle" it and leave it flat to try again?
Didn't you notice my Embarassed ? There's nothing hypothetical about it, I assure you!
Fortunately it started slow, and I knew enough to realise exactly what was going on when my attempts to true whilst tensioning only made the deviations bigger. So the rim hadn't gone beyond its elastic limit and backing off the tension all round restored it to roundness. Starting from a zero tension, true wheel, subsequent tensioning to a lower "note", was successful - at least until the bike got stolen!
My excuse for over-tensioning is I was using an old-stock open-section rim to build a college hack bike for my son. All the other wheels I'd recently built had torsionally much stiffer box section rims, which can stand more tension (and bigger sideways hits) before "pringling" (what a versatile word this is!) so I'd become accustomed to tightening spokes that hard.
The relatively moderate tension at which this ocurred probably helped to make it a gradual and recoverable pringle. If it were to happen above the higher tension permitted by modern rims, the wheel would probably pringle more suddenly and would distort much further in order to relax the greater amount of spoke elongation, which increases in proportion to their tension. In that case it's very likely the rim would have yeilded and need to be overbent in the opposite direction to make it true.
Most people woudn't bother, but I have successfully straightened badly buckled rims using a flat surface and a collection of blocks of wood to press down and flatten the rim a section at a time. I've then gone on to build these restored rims into reliable wheels. It was less time and bother than trying to source something compatible with the existing number and length of spokes. Mick's rim however, is certainly beyond redemption!
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Chris Juden
PW
"Tension by stress relieving" is Brandt's recommended method - as my earlier post. When the rim won't stand any more tension it "Pringles" when the spokes are tweaked, so you back everything off 1/4 turn, re-true it and the wheel is complete. They last for years when tensioned that way.
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If at first you don't succeed - cheat!!
pigman
CJ wrote:
Didn't you notice my Embarassed ? There's nothing hypothetical about it, I assure you!
sorry, no i wrote it badly. I wasnt inferring it couldnt really happen, I was thinking it wouldnt (or is it couldnt) happen to me - this sort of thing only happens to the overzealous/inexperienced tightener. But after reading that you had it happen to you, I guess I'm going to revise this view too. Anyway, thanks for the answer.
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Steel is real, the rest is second-best