Yet Another Cycling Forum
General Category => The Knowledge => Topic started by: rogerzilla on 05 September, 2011, 08:28:42 pm
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Thought it was about time we had some of these.
1. Spokes do not "bed in" and need retightening after an initial period, unless it's a badly built wheel.
Just occasionally you get a soft hub shell in which the spoke heads can creep a little, but these are rare (the only hub where I had this problem was a very thin Sturmey-Archer alloy shell from 1951, which has flanges the same thickness as the steel shell; they often crack).
2. Spokes do not fail because they are too tight. They fail because they are too loose (movement leads to fatigue). The ultimate tensile stress of a spoke is way above anything the rim can take, and riding the wheel makes them go slacker, not tighter.
3. Spoke tension does not affect ride quality.
4. Plain gauge spokes are not stronger than double-butted. Their advantage is that the wheel goes out of true by a smaller margin should one break, because they are not stretched as far as DB spokes. But spokes don't break in a good wheel.
5. Radial spoking is not more aerodynamic, but it looks cool.
6. It makes virtually no difference to wheel strength whether your spoking is symmetrical or asymmetrical or which way round the leading and trailing spokes run, unless you have a good reason unconnected to the wheel itself.
Iif you think your fixie will throw a chain, you want the spokes to throw the chain out, not suck it down between the sprocket and hub flange where it will jam; so the "heads in" spokes should radiate backwards
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Well said, that man!
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7) Building a wheel doesn't require mystic skills other than patience. Building a good wheel quickly does.
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I'm not sure what you mean by 3)
I've had wheels where the spokes were too slack, and when pushing the bike hard (not honking, just going for it), the wheel gave from side to side, making the rear very squirmy in feel.
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I inferred that he means that deliberately building wheels with lower tension in the spokes (as has been suggested to me by someone who should know better), for a touring bike, will give a more comfortable ride. This is not true. I tension my wheels as much as I can (within sensible limits) and fit the biggest tyres I can get in the frame.
If the spokes are slack enough for the bike to squirm, they are too loose, full stop.
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I inferred that he means that deliberately building wheels with lower tension in the spokes (as has been suggested to me by someone who should know better),..
That person didn't also advocate tied and soldered spokes perchance ... ::-)
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re 5):
Why is it done then? Just to look cool?
And what's with the low spoke count? Surely the rim needs to be stronger to compensate thereby negating any potential weight saving?
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Irrelevant. Everybody buys factory wheels these days. If they break, you take them back to the shop and wait 6 weeks, or throw them away. :demon:
But seriously - tied and soldered spokes don't make a "stronger" wheel, the only advantage is that if a spoke breaks it's less likely to break free completely and cause more damage (to bike or rider).
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The OP is sprinkled with awesome sauce :thumbsup:
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I inferred that he means that deliberately building wheels with lower tension in the spokes (as has been suggested to me by someone who should know better),..
That person didn't also advocate tied and soldered spokes perchance ... ::-)
No. I did ask and this person considers that practice to be outmoded.
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re 5):
Why is it done then? Just to look cool?
And what's with the low spoke count? Surely the rim needs to be stronger to compensate thereby negating any potential weight saving?
1; Yes.
2; I suspect that this is the case.
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re 5):
Why is it done then? Just to look cool?
And what's with the low spoke count? Surely the rim needs to be stronger to compensate thereby negating any potential weight saving?
1; Yes.
2; I suspect that this is the case.
Uncrossed spokes will make a cleaner passage through the air than crossed. As the spokes at the top of a wheel will be travelling somewhat fast than the bike, this may be significant.
Regarding wheel strength: traditionally, low spoke-count wheels were simply more fragile and used mainly in time trials, where a steady speed on reasonable road surfaces wouldn't stress them too much.
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I had always thought the reason for radial spokes on front wheels was to save weight (shorter spokes).
Also intrigued by (3).
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I had always thought the reason for radial spokes on front wheels was to save weight (shorter spokes).
You are probably right, but radial spoked wheels are usually of the low spoke count so need stronger, heavier rims to compensate. Therefore, it's difficult to compare apples with apples.
Also intrigued by (3).
Me too.
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I inferred that he means that deliberately building wheels with lower tension in the spokes (as has been suggested to me by someone who should know better),..
That person didn't also advocate tied and soldered spokes perchance ... ::-)
Nothing wrong with tied and soldered on the rear wheel of a track bike used by a strong sprinter.
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(6) at last! Someone else says it! :thumbsup:
And an extra one: Your first go at a wheel will not kill you. If it's rideable, it's safe enough, and if it goes out of true, it's not rideable any more.
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8) Having a cup of coffee and a cake at Big Al's does not give you botulism :thumbsup:
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re 5):
Why is it done then? Just to look cool?
The spokes can be shorter, therefore a tiny tad lighter and more aero. Easier to lace as well. The hub flanges have to be strong enough though, and you lose the undoing-prevention advantage of crossed spokes. Looking cool is a big part of it.
And what's with the low spoke count? Surely the rim needs to be stronger to compensate thereby negating any potential weight saving?
Yes, and sometimes the spokes are thicker therefore heavier too. It is more aerodynamic though. Weight can be minimised by making the hub incredibly light (which may include stupidly small bearings) and using carbon fibre for the rims. Some of the fancy low-spoke wheels, especially the cheaper ones, are indeed still heavier than the lightest conventional handbuilt wheels.
Aerodynamics is more important than weight for fast riders.
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And an extra one: Your first go at a wheel will not kill you. If it's rideable, it's safe enough, and if it goes out of true, it's not rideable any more.
+1
When you have a look at the wheels on a lot of low-mid end bikes, it's a miracle that they don't collapse within a few hundred yards. However, they don't. They just mostly work.
You'd have to be seriously ham-fisted to build up a wheel from new parts that was worse than that.
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Once the tension in the spokes is high enough to hold the wheel in a stable shape, the wheel is already much less flexible than a tyre. When it is fully tensioned, the wheel's flexibility is considerably less than that of the tyre. Wheels should always be tensioned "properly". It is important to choose the components to suit the application, then build the wheel accordingly.
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Aerodynamics is more important than weight for fast riders.
I'll stick to conventional wheels then ;).
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Uncrossed spokes will make a cleaner passage through the air than crossed. As the spokes at the top of a wheel will be travelling somewhat fast than the bike, this may be significant.
Will the cleaner passage through the air be noticed at the crossing point (or, for radial spokes, where the crossing point would have been), or through the length of the spoke? Much of the spoke length is already sheltered behind the rim, and there's probably a fair bit of turbulence created by the fork blades. So how much difference is the presence or absence of a crossing point really going to make?
ISTR that something over 90% of the aerodynamic drag experienced by a cyclist is due to the size and riding position of the cyclist, so messing around with spoke counts and crossing patterns seems a little silly.
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It's all silly, but it's satisfying to know that you've done everything possible (within reason and budget) to make the bike as fast as possible - despite the fact that the weeny bit of time saved per mile will only be relevant to time trialists. It becomes a hobby in itself.
I've also gone to some lengths to save a silly amount of weight - just because it's fun and interesting, to those of us sad enough to find such things fun and interesting. :)
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I've never understood why, when crossing spokes, some builders pass them "wrong side" of each other so the spokes are touching and curved. This must detract from the overall strength, surely? It looks particularly bad on small wheels.
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I've never understood why, when crossing spokes, some builders pass them "wrong side" of each other so the spokes are touching and curved. This must detract from the overall strength, surely? It looks particularly bad on small wheels.
That's the 'lacing' and virtually all good wheels are built that way.
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I've never understood why, when crossing spokes, some builders pass them "wrong side" of each other so the spokes are touching and curved. This must detract from the overall strength, surely? It looks particularly bad on small wheels.
It's normal for spokes to touch and curve at the crossings. This lacing spreads load and increases lateral strength, and helps to prevent spoke-loosening.
Without this, there wouldn't be any point in crossing the spokes besides the angle being less stressful for the hub flanges.
EDIT: and to transmit drive torque, and braking torque with disc/hub brakes.
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(6) at last! Someone else says it! :thumbsup:
Definitely - but there are some folks out there - and you all know who you are (well thumbed stained JB book under the bed) - like bending over bicycle wheels and scratching sometimes imaginary beards whilst going hmmm ::-)
Although I guess there might well be a case for disc brake wheels ;)?
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Uncrossed spokes will make a cleaner passage through the air than crossed. As the spokes at the top of a wheel will be travelling somewhat fast than the bike, this may be significant.
Will the cleaner passage through the air be noticed at the crossing point (or, for radial spokes, where the crossing point would have been), or through the length of the spoke? Much of the spoke length is already sheltered behind the rim, and there's probably a fair bit of turbulence created by the fork blades. So how much difference is the presence or absence of a crossing point really going to make?
ISTR that something over 90% of the aerodynamic drag experienced by a cyclist is due to the size and riding position of the cyclist, so messing around with spoke counts and crossing patterns seems a little silly.
I think uncrossed / flat spokes do make sense on some recumbents where the rider position is quite aero, especially with a fairing or tailbox, when riding at over 30km/h
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I love it. Every "club" has their "myths".
Every club has its shared passions transcending gender race politics and even religion? etc
The good thing about YACF is the diversity and ability to laugh uncontrolably at each other and enjoy a good thing
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Ooops!
Is it a matter of three strikes and out - if one diverts off topic utilising a foreign left sided pond metaphor? :demon:
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I've never understood why, when crossing spokes, some builders pass them "wrong side" of each other so the spokes are touching and curved. This must detract from the overall strength, surely? It looks particularly bad on small wheels.
It's normal for spokes to touch and curve at the crossings. This lacing spreads load and increases lateral strength, and helps to prevent spoke-loosening.
Without this, there wouldn't be any point in crossing the spokes besides the angle being less stressful for the hub flanges.
I thought the primary point of crossing was to transmit drive torque, and braking torque with disc/hub brakes.
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I thought the primary point of crossing was to transmit drive torque, and braking torque with disc/hub brakes.
I forgot those good points, but the other points apply as well. Good front non disc/hub front wheels are also laced in the same way for the reasons I mentioned. Otherwise no-one would bother.
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Only just noticed this thread....
Just something to add Re 3).
Spokes, like springs, obey hooks law whereby the deflection Vs load graph is a straight line. i.e. The stiffness is constant and independent of the load (tightness). So once the spoke is tightened sufficiently not to be slack while riding. There is no extra benefit of tightening any further - it does not get any stiffer.
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"Not to be slack while riding" includes having enough tension in reserve to cope with momentary reductions in spoke tension from impacts to the wheel from potholes etc, as the rim deflects. So I think it potentially helps to have as much tension as the rim can bear.
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Plus the torque from mashing gears out of the saddle. That's a not-inconsiderable side loading.
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2. Spokes do not fail because they are too tight. They fail because they are too loose (movement leads to fatigue). The ultimate tensile stress of a spoke is way above anything the rim can take, and riding the wheel makes them go slacker, not tighter.
Not strictly true. The spokes nearest the ground will go slack when riding which will in turn tighten those opposite the ground a bit. Its all relative. They'll go slack and tight as you ride but its all equal (also if its built right it'll be so minute it won't matter).
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2. Spokes do not fail because they are too tight. They fail because they are too loose (movement leads to fatigue). The ultimate tensile stress of a spoke is way above anything the rim can take, and riding the wheel makes them go slacker, not tighter.
Not strictly true. The spokes nearest the ground will go slack when riding which will in turn tighten those opposite the ground a bit. Its all relative. They'll go slack and tight as you ride but its all equal (also if its built right it'll be so minute it won't matter).
I assume you mean "less tight" rather than "go slack"
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7. You need a special wheel jig and tensiometer to build a wheel.
This is my first wheelbuild (to be fair, a rim transplant) which I built the day before the Elenith 2007. I rode the wheel for about two years (by which time it needed another new rim) with only the most minor of tweaks.
http://www.youtube.com/watch?v=rXWFJrKjGRk (http://www.youtube.com/watch?v=rXWFJrKjGRk)]
The noise you can hear is vibration from the schmidt dynohub resonating through the workmate frame. Off the workmate, its smooth and silent.
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That setup looks like it would work better than my cheap purpose-built trueing stand. :thumbsup: I particularly like the tie-wrap guages. :)
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7. You need a special wheel jig and tensiometer to build a wheel.
This is my first wheelbuild (to be fair, a rim transplant) which I built the day before the Elenith 2007. I rode the wheel for about two years (by which time it needed another new rim) with only the most minor of tweaks.
http://www.youtube.com/watch?v=rXWFJrKjGRk (http://www.youtube.com/watch?v=rXWFJrKjGRk)]
The noise you can hear is vibration from the schmidt dynohub resonating through the workmate frame. Off the workmate, its smooth and silent.
That's not a myth; it's total bollocks.
I've got a Var jig. The only advantage is that it is too heavy to move easily. It's supposed to help dish the wheels correctly, but that's bollocks, too.
i got it as part of a job lot of bike tools (very cheap), otherwise i wouldn't bother with it.
You don't even need a fork in a Workmate, although that makes truing a front wheel a lot easier.
Every cyclist already has a truing jig; the bike. I'm not averse to correcting small errors in lateral trueness withe the wheels on the bike.
If you are building wheels for yourself, you may as well true them on the bike. A dishing gauge would be handy, but it is possible to make one yourself.
I'm currently building cheap(ish) dynamo wheels for stock using very basic hubs (Novatech). They're as rough as arseholes in the stand, but reasonably smooth and long lasting (several thousand miles) on the road.
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Not strictly true. The spokes nearest the ground will go slack when riding which will in turn tighten those opposite the ground a bit.
It's easy to demonstrate that the upper spokes don't measurably change in tension when you place a load on the wheel, whereas the tension of spokes below the hub reduce in tension. In a static situation in any case! :P
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And - there's nothing at all mythical or magical about any ONE wheelbuilder
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Not strictly true. The spokes nearest the ground will go slack when riding which will in turn tighten those opposite the ground a bit.
It's easy to demonstrate that the upper spokes don't measurably change in tension when you place a load on the wheel, whereas the tension of spokes below the hub reduce in tension. In a static situation in any case! :P
The lowest spokes go slacker because the rim deforms slightly due to the ground pushing against it. Because the lower spokes aren't pulling down so hard the weight on the hub is supported by the unchanged tension in the upper spokes.
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I forgot to comment on tensiometers. Biggsy has mentioned getting a feel for the correct tension for your particular wheel. That's all you need. For beginners, bringing the wheel into correct tension, systematically and carefully will ultimately lead to getting the wheel right.
Tensiometers are not like, say, multimeters. They all apparently give different results. You would need to know which instrument, and what rims and spokes were used to arrive at a recommended tension. Then, if you have a tensiometer, you need a well built wheel of known tension to calibrate it.
You can check for evenness of tension by ear.
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Or feel.
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Or feel.
:thumbsup: :thumbsup:
Once you know the feel
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And - there's nothing at all mythical or magical about any ONE wheelbuilder
There's something pretty cool about a blind wheelbuilder.
(although he needs to move somewhere with more kudos than Reading )
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And - there's nothing at all mythical or magical about any ONE wheelbuilder
There's something pretty cool about a blind wheelbuilder.
(although he needs to move somewhere with more kudos than Reading )
Wheelbuilding in Didcot blind or Reading with eyes does not make one a mythical person though?
And hopefully we can all agree that a YACF wheel should have reasonable tolerances?
Tee hee!
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And hopefully we can all agree that a YACF wheel should have reasonable tolerances?
I fear a YACF wheel will pull to the left and, unless corrected, end up in the gutter.
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I inferred that he means that deliberately building wheels with lower tension in the spokes (as has been suggested to me by someone who should know better),..
That person didn't also advocate tied and soldered spokes perchance ... ::-)
Nothing wrong with tied and soldered on the rear wheel of a track bike used by a strong sprinter.
I lent a pair of track sprints, built for a tandem, to the England pair for the Commonwealth Games (they won gold - Geoff Cooke and Tony Brocklehurst). They were returned to me re-built and tied and soldered, the front wheel in a two cross/one radial pattern. They were done by the German team mechanic. Boy, those wheels are solid, and totally bomb-proof, and have survived several crashes since.
I've known several very good wheel builders, and I'm convinced that there are good, very good, and then, not very good, builders. One of the greatest is Steve Snowling who used to work the sixes for Tony Doyle. He tied and soldered (note - not just tied - you have to scape the chrome off chrome spokes, or use rustless, to properly solder the wires to the spoke) some track wheels. Again, they never, ever, went out of true.
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2. Spokes do not fail because they are too tight. They fail because they are too loose (movement leads to fatigue). The ultimate tensile stress of a spoke is way above anything the rim can take, and riding the wheel makes them go slacker, not tighter.
Not strictly true. The spokes nearest the ground will go slack when riding which will in turn tighten those opposite the ground a bit. Its all relative. They'll go slack and tight as you ride but its all equal (also if its built right it'll be so minute it won't matter).
I assume you mean "less tight" rather than "go slack"
Just using the OP's terminology.
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Maybe it's a matter of trusting the builder. Round about 1979, I was a member of Leeds St Christopher's CC while a student. We had Keith Lambert as a speaker one evening. He had just collected his (one and only) team bike for the new season, and was off to take the wheels to bits and rebuild them.
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I inferred that he means that deliberately building wheels with lower tension in the spokes (as has been suggested to me by someone who should know better),..
That person didn't also advocate tied and soldered spokes perchance ... ::-)
Nothing wrong with tied and soldered on the rear wheel of a track bike used by a strong sprinter.
I lent a pair of track sprints, built for a tandem, to the England pair for the Commonwealth Games (they won gold - Geoff Cooke and Tony Brocklehurst). They were returned to me re-built and tied and soldered, the front wheel in a two cross/one radial pattern. They were done by the German team mechanic. Boy, those wheels are solid, and totally bomb-proof, and have survived several crashes since.
I've known several very good wheel builders, and I'm convinced that there are good, very good, and then, not very good, builders. One of the greatest is Steve Snowling who used to work the sixes for Tony Doyle. He tied and soldered (note - not just tied - you have to scape the chrome off chrome spokes, or use rustless, to properly solder the wires to the spoke) some track wheels. Again, they never, ever, went out of true.
Just because some wheel builders tie and solder doesn't mean that it makes the wheel stronger. As said by others up post there is no advantage in doing so other than to stop broken spokes flailing around. The wheels you mention were obviously very well built wheels, buit not because of the tie and soldering. If anything the practice just adds weight and makes the wheel harder to re-true.
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Here's some proof
http://sheldonbrown.com/brandt/tied-soldered.html
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I lent a pair of track sprints, built for a tandem, to the England pair for the Commonwealth Games (they won gold - Geoff Cooke and Tony Brocklehurst). They were returned to me re-built and tied and soldered, the front wheel in a two cross/one radial pattern. They were done by the German team mechanic. Boy, those wheels are solid, and totally bomb-proof, and have survived several crashes since.
I'd always been lead to believe that track wheels (from pre 1980s) were routinely tied and soldered because of the lateral and inline stresses arising from sprinting round banked tracks. Especially for tandem loading!
It sounds like these wheels are in the Crow's Foot pattern.
Re: earlier posts, laced spoking:
Another factor for rear wheels is to dish the wheel and give spoke clearance to the rear jockey-wheels cage for innermost sprockets. Again, in 5 & 6 speed freewheel days, big sprocket sizes may have been as low as 19 or 20T (for straight-up TT use). Not like the more generous 23 - 32 T dinnerplates commonly in use today. And 5 speed chains and cages were wider than modern 9/10/11sp cages. Any un-laced spoke is more likely to clash (unless it is fitted from the cassette side into the flange).
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Jobst Brandt's view on tying and soldering from http://www.sheldonbrown.com/brandt/tied-soldered.html:
While writing The Bicycle Wheel, to conclusively determine what effect tying and soldering of spoke crossings in a wheel had, I asked Wheelsmith to lend me an untied pair of standard 36 spoke rear wheels, on Campagnolo low and high flange hubs. I had an inner body of a freewheel machined with flats so that a wheel could be clamped into the vise of a Bridgeport milling machine while the left end of its axle was held in the quill.
With the hub rigidly secured, with its axle vertical, dial gauges were mounted at four equally spaced locations on the machine bed to measure rim deflections as a 35lb weight was sequentially hung on the wheel at these positions. The deflections were recorded for each location and averaged for each wheel before and after tying and soldering spokes.
The wheels were also measured for torsional rigidity in the same fixture, by a wire anchored in the valve hole and wrapped around the rim so that a 35 lb force could be applied tangential to the rim. Dial gauges located at two places 90 degrees apart in the quadrant away from the applied load were used to measure relative rotation between the wheel and hub.
Upon repeating the measurements after tying and soldering the spokes, no perceptible change, other than random measurement noise of a few thousandths of an inch, was detected. The spokes were tied and soldered by Wheelsmith who did this as a regular service. The data was collected by an engineer who did not know what I expected to find. I set up the experiment and delivered the wheels.
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Jobst Brandt's view on tying and soldering from http://www.sheldonbrown.com/brandt/tied-soldered.html:
While writing The Bicycle Wheel, to conclusively determine what effect tying and soldering of spoke crossings in a wheel had, I asked Wheelsmith to lend me an untied pair of standard 36 spoke rear wheels, on Campagnolo low and high flange hubs. I had an inner body of a freewheel machined with flats so that a wheel could be clamped into the vise of a Bridgeport milling machine while the left end of its axle was held in the quill.
With the hub rigidly secured, with its axle vertical, dial gauges were mounted at four equally spaced locations on the machine bed to measure rim deflections as a 35lb weight was sequentially hung on the wheel at these positions. The deflections were recorded for each location and averaged for each wheel before and after tying and soldering spokes.
The wheels were also measured for torsional rigidity in the same fixture, by a wire anchored in the valve hole and wrapped around the rim so that a 35 lb force could be applied tangential to the rim. Dial gauges located at two places 90 degrees apart in the quadrant away from the applied load were used to measure relative rotation between the wheel and hub.
Upon repeating the measurements after tying and soldering the spokes, no perceptible change, other than random measurement noise of a few thousandths of an inch, was detected. The spokes were tied and soldered by Wheelsmith who did this as a regular service. The data was collected by an engineer who did not know what I expected to find. I set up the experiment and delivered the wheels.
And what? The problem I have understanding most things written by Brandt (Usually quoted by you) is that although he's prepared to go to great lengths to explain the method he doesn't bother to give any of the reasoning. Here we have a meticulously executed experiment in hanging 35lb weights of various parts of a wheel in various ways, all independently verified. Just how does that demonstrate the point? In what way does that replicate me riding the bike? If that's not explained, it's meaningless.
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Although I'm sceptical of a lot of Brandt's theories, the tests he made seem quite simple: vertical and tangental stresses, the kinds of thing you'd want to know about a wheel.
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yebbut, nipples lubed or nipples dry?
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yebbut, nipples lubed or nipples dry?
I wear loose clothing when building wheels.
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Although I'm sceptical of a lot of Brandt's theories, the tests he made seem quite simple: vertical and tangental stresses, the kinds of thing you'd want to know about a wheel.
So now we know about the stresses caused by a 35lb weight. Call me thick, but I still don't know the relevance of that.
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Changing the wheel stiffness, perhaps by tying and soldering spokes, should result in a difference in deflection for a fixed load. No difference in deflection means no difference in stiffness, means tying and soldering doesn't change wheel stiffness.
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You're trying to replicate the forces experienced by a wheel when riding, but in a controlled environment where the mechanical effects on the wheel can be measured. I'll take that any day over somebody's subjective opinion as to how it "feels" when riding - that's when you get Cycling Plus type "stiff yet responsive" nonsense.
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And what? The problem I have understanding most things written by Brandt (Usually quoted by you) is that although he's prepared to go to great lengths to explain the method he doesn't bother to give any of the reasoning. Here we have a meticulously executed experiment in hanging 35lb weights of various parts of a wheel in various ways, all independently verified. Just how does that demonstrate the point? In what way does that replicate me riding the bike? If that's not explained, it's meaningless.
Surprisingly enough, the fact that he didn't explain something to you doesn't make it meaningless. He's writing as an engineer, for other engineers, discussing an engineering modification to a bike.
So now we know about the stresses caused by a 35lb weight. Call me thick, but I still don't know the relevance of that.
No, he measured deflections, not stresses. You're not thick, you're just not an engineer so it's not your area. The productive response to that is to ask for explanations, not get antsy and imply it's his fault. You didn't pay him to explain it to you.
The point is that while a metal structure like this is having forces applied to it which are in its normal expected use, the deflections, or flex in it, will be directly proportional to applied force. This means that double the force, double the flex, half the force, half the flex. But the ratio of force to flex is called the stiffness of the structure (in this particular direction). Measuring the movement for a 35lb force tells you that.
Furthermore, measuring it in one direction and then another at 90 degrees tells you how much it flexes in each of those directions. Again with forces within normal expected use, the combination also tells you how much it will move for forces inbetween those angles.
So the experiment is measuring exactly how stiff or flexible the wheel is. Objectively, with numbers. The sort of thing engineers do to figure out if a change (such as tying and soldering) is worthwhile.
And no, I don't agree with Brandt on everything either, but this one does appear to be pretty clear.
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Has anyone managed to measure the lateral torque between axle and wheel rim, when sprinting?
I'm wondering why he chose 35lb.
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Not strictly true. The spokes nearest the ground will go slack when riding which will in turn tighten those opposite the ground a bit.
It's easy to demonstrate that the upper spokes don't measurably change in tension when you place a load on the wheel, whereas the tension of spokes below the hub reduce in tension. In a static situation in any case! :P
The lowest spokes go slacker because the rim deforms slightly due to the ground pushing against it. Because the lower spokes aren't pulling down so hard the weight on the hub is supported by the unchanged tension in the upper spokes.
That's a bit misleading. Provided the spokes all remain in tension then the weight bearing down on the hub is supported by a reduction of tension of the lower spokes within the pre- stressed structure of the wheel. There is no "need" for the rim to deform, although, of course, in a dynamic real world situation it will, a tiny bit, both as weight is borne by the wheel and as lateral and driving or braking forces dynamically affect spoke tension.
I think of it as the rim deforming because the spoke tension is changing, not the other way round.
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I forgot to comment on tensiometers. Biggsy has mentioned getting a feel for the correct tension for your particular wheel. That's all you need. For beginners, bringing the wheel into correct tension, systematically and carefully will ultimately lead to getting the wheel right.
Tensiometers are not like, say, multimeters. They all apparently give different results. You would need to know which instrument, and what rims and spokes were used to arrive at a recommended tension. Then, if you have a tensiometer, you need a well built wheel of known tension to calibrate it.
You can check for evenness of tension by ear.
How many have you tested? I've compared mine with two others (an FSA and a DT Swiss) and they all gave the same result to within 5 percent.
How is a beginner supposed to know what the correct tension is without being able to measure it?
Most people are happy to talk numbers when it comes to things like tyre pressures; I don't understand the widespread cynicism about tensiometers!
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For the record, I'm not against tensiometers, I just think that you can build good wheels without one. Beginners can compare by feel with another similar wheel, or learn through trial and error. Admittedly, the error of cracking a rim through over-tension is not a cheap one.
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I'm too too sure where we're all going with this (the tied/soldered/laced/stiffness debate) ?
Tewdric is correct (#65 above): spokes should always be in tension however the level of tension must fluctuate as the loaded bike wheel is moved along. And that variation in tension results in fatigue loading which ultimately affects spoke and hub flange life. And that variation in tensile stress/fatigue will be present regardless of whether tied & soldered spokes were used, because that is only a function of the axial tensile loads in the spokes. The fact that a spoke is tied cannot detract from its load wanting to take taking the shortest/stiffest load path available which is to carry on along the spoke. Engineering fact: stiffness = strength.
So, the tying and soldering can only affect lateral stiffness. By tying and soldering the cross-overs, a node point is created at each tied cross-over which forms a series of stiffer triangulated sub-frames in the rim/spoke/hub structure. So, the spokes cannot freely displace relative to each other as untied spoke could, under their fluctuating axial tension. So, the lateral spring stiffness of a tied wheel must be increased. So, it will be less likely to deform before exceeding/reaching the elastic yield point (of spokes) or permanent plastic deformation, or flange shear failure.
So, tied and soldered laced spokes must create a wheel that is laterally stiffer and has a greater capacity to withstand lateral forces (such as those acting on wheels on a steeply banked velodrome where gravitational and centripetal force effects are present) than an untied wheel. But tied and soldered spokes have no benefit for an upright wheel rolling normally along a straight road.
End of...
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Engineering fact: stiffness = strength.
Er, wtf? Is that meant to be a joke?
So, the tying and soldering can only affect lateral stiffness. By tying and soldering the cross-overs, a node point is created at each tied cross-over which forms a series of stiffer triangulated sub-frames in the rim/spoke/hub structure.
Stiffer how exactly? Sure, if you consider each sub-frame it is stiffer, but when you put two in series as there are then you add deflections for the same force and it becomes pretty similar again. Not exactly the same in all directions, which is why you'd want to do a proper analysis or test it.
So, the spokes cannot freely displace relative to each other as untied spoke could, under their fluctuating axial tension. So, the lateral spring stiffness of a tied wheel must be increased.
So why doesn't it show up in Brandt's test? The one where the axle is vertical and the rim loaded with weights is a direct test of lateral stiffness.
...lateral forces (such as those acting on wheels on a steeply banked velodrome where gravitational and centripetal force effects are present) ...
Those forces are balanced by the lean angle. There may be plenty of lateral forces on the wheel from sprinting and generally throwing the bike about. And the bends will generate increased vertical loading (relative to the wheel/bike). But the corners and banking do not directly affect lateral forces on the wheel.
End of...
Er, end of what exactly? Does that mean you don't want anybody else to talk anymore?
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End of...
Er, end of what exactly? Does that mean you don't want anybody else to talk anymore?
Quite.... and tbh I find the attempt to re-open the tying and soldering debate as pointless as a h.....t debate. Nobody is saying GraemeMcC (or anyone else) should cease to tie and solder if they so choose. Nor, I hope, is anyone trying to impose tying and soldering on us mere mortal wheelbuilders who can build a wheel that is satisfactory for our own purposes without doing so.
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Tying and soldering gives you a trick-looking wheel which is a PITA to fix at a later date, should anything go wrong - so you'd better get it spot on.
Apart from the looks, it stops a broken spoke from flailing about and impaling something but (a) injury is a pretty remote possibility - only Nutty or Phil could probably manage it - and (b) if you do break a spoke on your tied and soldered wheel, you're in for a very tough time trying to swap it out.
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I'm told that tying and soldering was fairly crucial on ordinary/penny-farthing bicycles. The spokes on the front wheel of an ordinary were long enough to present a hazard when they broke, and the primitive state of metallurgy back then meant that they broke much more frequently than is the case today.
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End of...
Er, end of what exactly? Does that mean you don't want anybody else to talk anymore?
:thumbsup:
ISTR the last time we had a "does a wheel stand on its lower spokes or hang from its upper ones" debate it ran to about 50 pages ...
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It does neither. It "hangs" by ALL the spokes except the bottom two or three. Brandt was being provocative in the way he described it, although he understood it perfectly well.
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Apologies folks - been away. But I'll defend my opinions:
Engineering fact: stiffness = strength.
Er, wtf? Is that meant to be a joke?
No: it is a fundamental engineering principle.
As I stated, the load running along a spoke will take the most direct loadpath available to it which is its stiffest.
Stiffness in any structure, whether it's a laced wheel or a multi-storey building or whatever, will attract load to it until such time as deflections occur and load-sharing becomes possible when the initially stressed elements deform to a stage that their effective stiffness reduces to the level that other elements can attract some of the load.
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Engineering fact: stiffness = strength.
Er, wtf? Is that meant to be a joke?
No: it is a fundamental engineering principle.
Erm, you're having a laugh mate.
Simple google for school textbook type explanations of the difference between stiffness and strength produces:
http://www.vendettacycles.com/vendettacycles/stiffness.htm (http://www.vendettacycles.com/vendettacycles/stiffness.htm)
http://www.bledsoebrace.com/education/cp030004.htm (http://www.bledsoebrace.com/education/cp030004.htm)
http://www.matter.org.uk/schools/content/YoungModulus/stiffnessexercise.html (http://www.matter.org.uk/schools/content/YoungModulus/stiffnessexercise.html)
<snip slightly unnecessary rudeness>
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Let me get my answers out, mate...
So, the tying and soldering can only affect lateral stiffness. By tying and soldering the cross-overs, a node point is created at each tied cross-over which forms a series of stiffer triangulated sub-frames in the rim/spoke/hub structure.
Stiffer how exactly?
An untied spoke has an effective length running from rim to hub flange. In any direction.
So under tensile strain, it will stretch slightly and deform evenly over the full spoke length (assuming plain gauge uniform thickness spokes for this explanation).
Under lateral forces, the rigid system is from flange A - spoke A - rim - spoke B - flange B.
An untied crossed spoke is only partially restrained at its crossover: it can move in one direction by slipping along its partner at its lace point.
So the effective subframe size is still the overall spoke length relationship from rim to hub as above.
Thus the lateral rigid system is also still flange - spoke A - rim - spoke B - flange B.
However, a tied/soldered crossed spoke will have directional restraint at its crossover. So the spoking becomes two sets of triangular subframes: a larger outer set from rim to X-over to rim, and the smaller inner set from hub to X-over to hub.
The fixed node at the X-over rmeans that any lateral flexural movement of from a spoke must mobiliize the other spoke at the cross-over. So that movement must induce a force into that other spoke (induced tension). So that is developing strain energy which is taken up from the total energy in the wheel. So the overall lateral energy is being mobilised and transferred from deflections in one spoke into two spokes. So, forces are being shared. So, overall lateral force effects in one spoke are reduced - wheel is effectively laterally stiffer.
Does that help explain?
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Nobody is saying GraemeMcC (or anyone else) should cease to tie and solder if they so choose. Nor, I hope, is anyone trying to impose tying and soldering on us mere mortal wheelbuilders who can build a wheel that is satisfactory for our own purposes without doing so.
I'm not advocating the benefits of soldering cross-overs - I'm trying to add to the pointlessness of it to further debunk the myth - from a structural engineer's p-o-v.
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I ain't arguing with your analysis of a wheel, but, stiffness=strength?
A 5mm rod made of glass is very stiff compared to a 2.5mm spoke, but it doesn't take much force to break it.
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Two points:
The lateral force being applied is on the rim, not one spoke. That means that when one spoke is being moved by a lateral load, the ones adjacent are also. The spokes which cross over are only two holes apart. They're moving the same way at the same time.
When you load the rim laterally, the point of the spoke at crossover moves laterally. i.e perpendicular to the crossover contact, not along it. So they don't slide along one another. To get a movement which would be stopped by the tying but not otherwise you'd have to have a sufficiently flexible rim and localised force that the rim would bend laterally enough for the spokes to separate and get air between them without tying (not gonna happen, I think). Otherwise there is going to be no relative lateral movement of the crossover anyway, even without tying.
The only way you would get the transfer of forces you are talking about would be if there was sliding between spokes otherwise. But I'm looking at a wheel in front of me and I can't see a mechanism for it to happen with lateral loading.
Difficult to prove who is right with words rather than measurements of course, but Brandt appears to have done the right experiment for us.
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Fair points, Tom-e.
And my apologies to others - by "stiffness = strength" I was referring to structural system stiffness.
These were lunchtime-in-the-office posts and my brain was still in its "analysis and design" mode. Of course, a glass rod is a brittle structural material with good compression and tension qualities but, in the presence of surface micro-cracks, has poor flexural strength (unless specially treated to remove all micro-cracks). A steel spoke is a tensile component with great tensile properties but little flexural or shear strength and too slender to offer much in the way of compressive strength. A spider's web strand has fantastic tensile structural strength, but little else. Apples & pears...
But, another point to ponder, as I was coming home and thinking about posts from rogerzilla [#74, p5] and andrew-s & PeteJ [on p3] :-
- a spoked bicycle wheel is a tensile structure;
- when subject to imposed vertical load (i.e. rider on bike) the predominant imposed load path is from the axle to hub, transmitted via those spokes in most direct tension to the rim, then transferred around the circumference of the rim to acting onto the ground. (If you doubt that, consider a wheel with loose spokes and how that transmits the load. The bottom spokes would push out through the nipple if it weren't also for the fact that normal steel spokes have negligible compressive strength, and the side spokes have no flexural shear strength ability to transfer any imposed load).
- But, the rim is a hoop structure which will bend by flexing outwards at "3 & 9 o'clock" (like an egg) because it is being pulled downwards at the top from the imposed loaded spokes and is pushing up off the ground.
- This induced load bending is resisted by the spokes in tension (max induced tension at 3/9 o'clock, reducing elsewhere as a function of the rim hoop flexure).
- The resistance to the rim's hoop flexure is also a function of spoke elasticity (i.e. cross section area) & numbers of spokes.
So, I accept Rogerzilla's point, although these flexural hoop induced spoke forces are not going to be as severe as those directly involved in hanging the hub.
But, does this mean that a rigid (i.e. stiffer = stronger :facepalm: ) deep aero section rim builds a better wheel that doesn't develop much in the way of these hoop effect stresses or, should we have thinner section rims that do flex more thus share more of the tensile spoke load? (My apologies if this debate exists elsewhere...)
I could see that a wheel with a deep rim would have a lower degree of secondary hoop-effect stress fluctuations but its spokes would be subjected to a higher level of imposed load stress fluctuations per revolution. So, the fatigue life of the spokes may be compromised but the fatigue fluctuations in an alloy rim from local bending effects would be less, so the rim may be less susceptible to fatigue cracking.
Whereas, a more flexible rim and with fewer spokes would have higher hoop flexibility but lower peak imposed load variation in its spokes, so its spokes could last longer (at the expense of reduced flexural fatigue life of the rim)? And be more comfortable to ride?
Oh, my head hurts now...
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You have a fundamentally different view to the widely accepted understanding of the bicycle wheel explained by Jobst Brandt. If you haven't read it, it is well worth it.
And I always thought that hoop - effect stress fluctuations were what you get when you experience lock- to-lock shimmy during a 40mph descent..
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Cheers T.
I obviously haven't read through all of that yet, but I don't disagree with Brandt's basic description - a wheel is a (pre)tensioned structure and the key to how strong it is likely to be and its fatigue resistance is predominantly going to be down to how much prestress is built into the system and how those stresses vary when the wheel is subjected to additional loads when it is loaded by a rider sat on the machine.
The greater the pre-tension in the wheel, then the lower the stress variations will be due to rider loading. It's these stress variations that need to be dealt with. At the lower end of the pretension effect, then rider load effects will dominate. At greater pre-tensions, then rider imposed load will be less influential.
Sadly, in our office sit a team of stress analysts with just the right software to play with and to look at the variables such as rim stiffness, spoke positions, spoke stiffness, spoke stresses, etc. However, no way could I get them to apply their technology to this... Would cost more than I earn...
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The greater the pre-tension in the wheel, then the lower the stress variations will be due to rider loading. It's these stress variations that need to be dealt with. At the lower end of the pretension effect, then rider load effects will dominate. At greater pre-tensions, then rider imposed load will be less influential
And that is why wheels with loose or inadequately-tensioner spokes break spokes.
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Which is what I said at the start of the thread :smug:
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On the CTC forum bits for sale
http://forum.ctc.org.uk/viewtopic.php?f=32&t=73083
"Built by one of the best wheelbuilders in England (and the world!)" ::-)
How many bests constitute a whole pile of myths? :demon:
Reminds me about that add from SJSC - asking punters to call them and speak to one of their GURUS about anything! Track mitt gurus? Seat tube angled gurus? ;)
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Well Hewitt is indeed a damned fine wheel builder. Wonder what the world wide experience of the seller actually is though ::-)
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The only wonky wheel I have is a Hewitt wheel. It hasn't actually got any worse, though.
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Well Hewitt is indeed a damned fine wheel builder. Wonder what the world wide experience of the seller actually is though ::-)
I very much doubt Paul Hewitt builds the wheels he sells.
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Well Hewitt is indeed a damned fine wheel builder. Wonder what the world wide experience of the seller actually is though ::-)
I very much doubt Paul Hewitt builds the wheels he sells.
He was truing up a pair for me when I arrived to collect them although it could have been a quick QC check.
All the wheels that I've had off him save one (the Rohloff) has been perfect.
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So, having read through all this thread once more and not understood half of the arguments:
1. If wheels are necessarily so stiff that they don't move with weights hung off them (or otherwise), why aren't you all using solid disc wheels in your tourers and audax bikes; no spokes to break and after all is said and read it's the tyre that provides the comfort, not the spokes. ???
2. Why don't wheels just go oval, instead of going pretzel?
I am still going to carry on building my wheels as I have done for the last 40 years. I don't sell them so it's nobody's business but mine
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So, having read through all this thread once more and not understood half of the arguments:
That's because a simple bicycle wheel brings out the devils, the myths and the blinded like no other :demon:
Can you imagine Any (Cycling) Questions with Dimbleby anywhere in the country, with four guest speakers and some bloke asks about bike wheels? There'd be a riot ;D
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I'd go as far to say that drug testing should be applied to wheelbuilders. All that RSI and arthritis, not to mention back pain sitting at the jig day in day out.
According to my mate fast Eddy Fisher, who lived around the corner from J D Whisker when he had a shop in Kilburn in the 70s, there was a chap called Depressing Derek (name changed just in case the impossible could happen and he is STILL alive - doubt he had any family) who built wheels and moaned about customers and his bad back from building too many wheels.
As a semi professional unmythical lacer and truer myself, I have taken drugs. Mainly Cocodamol, alcohol, caffeine and an Ibuprofen rub gel - I own up! Bring on the truth and reconcilliation. Imagine the force us global spoke twizzlers would have? I wanna stand proud with my Chinese and Taiwanse sisters. We HAD to do it to compete on a level playing field/pay the bills/feed the kids.
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1. If wheels are necessarily so stiff that they don't move with weights hung off them (or otherwise), why aren't you all using solid disc wheels in your tourers and audax bikes; no spokes to break and after all is said and read it's the tyre that provides the comfort, not the spokes. ???
Because they're bad in cross winds and are more expensive and heavier.
2. Why don't wheels just go oval, instead of going pretzel?
The wheel is so much weaker laterally than radially that it only takes the slightest difference in tension between the left and right side for the rim to go sideways. Left and right spoke tension is never perfectly matched, especially after the event that caused the wheel to start to pretzel. The rim deforms in the easiest way for it. (Spokes pull the rim sideways as well inwards).