Everything about building wheels, glueing tubs, etc.
thisisatest
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WinterRider wrote:Anyone ever build a triplet with the NDS tension higher than the DS?

Sort of. I've built a 24hole carbon Mtb rim onto a 32hole Lefty hub, 2:1. Happened to be that the radial (right) side had slightly higher tension. It kinda was annoyed about it, but the wheel ended up holding up very well. Cx-rays, of course.

bm0p700f
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It has been confirmed before I cannot see why this is not understood that lateral stiffnes is independent of spoke tension. So is stiffness of any kind so long as there is spoke tension. The physics of a wheel is well known.

http://www.rouesartisanales.com/article-23159755.html

For radail stiffness this biggest factors is rim stiffness and spoke diamter, (spoke length, spoke number and bracing angles will have a small effect but it is small), for lateral stiffness the factors are rim stiffness, spoke stiffness, spoke length and bracing angles for a tensioned wheel. The wheel of course has to be tensioned or it fails to function as a wheel.

Another paper regarding wheel stiffness
http://people.duke.edu/~hpgavin/papers/ ... -Paper.pdf

KLabs
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people.duke.edu ... The behavior of bicycle wheels subjected to static radial loads can be accurately modeled by idealizing the system of interlacing spokes as a linear elastic foundation of uniform stiffness per length of circumference. [b]The spoke pattern affects the over-all radial stiffness of the wheel more than it affects the spoke strains.[/b]

From a numerical analysis, the spoking pattern has the greatest impact on the spoke strains when the wheel is subjected to large lateral loads, such as during cornering. In this case, wheels with longer spokes have lower strains than do wheels with shorter spokes.

... it may only be concluded that static spoke strain due to radial loads are roughly independent of the spoke pattern, for the wheels in this study. Static spoke strains are, however, influenced by the spoke pattern when lateral loads are applied to the rim. In this case, wheels with the shortest spokes have the highest spoke strains.

The fatigue resistance of the spokes, the spoke diameter, the arrangement of the spokes, and the stiffness of the rim influence wheel stiffness and fatigue life. Wheels with 2X, 3X, and 4X spoke patterns all have similar spoke strains when subjected to radial loads. The fatigue resistance of spoked wheels to steady cycling loads is very high for most typical service conditions.
Last edited by KLabs on Sat Feb 16, 2013 8:20 am, edited 1 time in total.

KLabs
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www.rouesartisanales.com ... Frontal stiffness
Coming back to our frontal stiffness test, the wheel is fixed by its axle, then crushed. The force applied is determined by software which records deformation at the same time. The wheels deform very little because of several parameters playing an important role in the vertical deformation. The rim height and its high frontal stiffness are not really prone to deform easily. Shallower rims obviously deform more easily than deep rims because they are not as stiff. The spokes also play a role: their number, crossing pattern, tension and spoke stiffness (material, cross section) all have an influence on overall vertical stiffness of the wheel. A low cross section spoke with low spoke tension will deform or lose its stiffness quicker than a high cross section and high tensioned spoke. The hub plays a role too, but its influence will be smaller than the two first.

Rear wheels are not as stiff as front wheels because of the bracing angle difference on the two sides of the rear wheel. A rear wheel with a shallow rim, with low tensioned spokes, will vertically be easier to deform than a deep rim wheel with high tensioned spokes. A special case worth highlighting is an exception which concerns the Shimano 7850 C24TU and C50TU wheels, but also the Mavic Cosmic Carbone Ultimate offering higher frontal stiffness front than rear. The high spokes tension seem to be responsible of this phenomenon.

Lateral stiffness
Beside this, when the rider pushes the pedals, the torque transmitted through the spokes deforms the wheel because of the bracing angles creating a lateral component: even when sitting in the saddle, the rear wheels moves between the brake pads when a rider stomps on the pedals. So the rear wheel must be as stiff as possible in order not to slip away when transferring the power. The lateral stiffness of a conventional wheel depends on several parameters. First of all, the rim will determine the stiffness of the wheel by its depth, its torsional stiffness and spoke length. Then, the spokes give the wheel integrity and play a role in the stiffness according to their tension and their cross section. Finally, according to Mavic, the most important parameter is the bracing angle, which is the distance between the flanges of the hubs.
Thus, in order to increase the lateral stiffness of a wheel one needs to:
- use a stiff and deep rim which will also comes with shorter spokes
- use larger spokes
- increase the bracing angle: hubs with flanges as far as possible
- high tensioned spokes to delay the moment when the wheel loses all its stiffness

However, all these improvements come with a weight penalty so we have to make compromises and identify the improvements with a big impact on stiffness but the smallest weight penalty: deep rim (increasing aero properties too), hubs with widely spaced flanges. Flange diameter will play a role too but it will come with an important weight penalty.

A high deflection of the rim between the brake pads may slow the rider during the acceleration phase if the rim hits the pad. The parameters playing a role here are not well known but when digging deep inside the stiffness/deflections at 180° sheet, there are at least two important parameters:
- the rim depth: the shallower it is, the smaller are the deflections between the brake pads, but the lower is the lateral stiffness of the wheel
- the spoking: the higher is the spoke count, the lower are the deflections between the brake pads, and the higher is the wheel stiffness.

There are some special cases, especially from the biggest manufacturers, where the rear wheels are as stiff or stiffer than the front wheels. This comes from the optimisation of the wheel components: special spokings, extreme tensions, unusual constructions (Mavic R-SYS for example). A heavy rider stresses more the wheels than a light rider. If this heavy rider uses a too flexy wheel, it will easily go out of shape while sprinting and its spokes (most of the time the rear wheel non drive side spokes) will often lose their tension. This has three consequences: the wheel will go out of true if the spokes are not locked, the rider will feel the lack of stiffness which is poor for the performance and the spokes will have a shorter working life (and break).

Conclusion
The feeling of efficiency and performance on the road mainly comes from the inertia of the wheels but lateral stiffness is important too. It also is not necessary to get the stiffest wheel at all costs because this may compromise other characteristics of the wheel. High lateral stiffness often means a heavier wheel, meaning higher inertia and therefore harder accelerations or more difficult climbs. Ideally, one should choose the wheels with the best weight to stiffness ratio, considering your own weight and it’s important not to forget aerodynamics.
Recommendations to optimise racing performance ... Basically, only heavy riders, or racers looking for extreme performance need stiffness at all cost.
- Over 80kg, the racer should focus on wheels over 40N/mm of lateral stiffness.
- 70-80kg, wheels under 35N/mm are likely to impair performance in some race situations.
- 60 and 70kg would be best avoiding wheels with lateral stiffness below 30N/mm.
Last edited by KLabs on Sat Feb 16, 2013 8:17 am, edited 1 time in total.

HillRPete
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How many spokes for a Pacenti PL23 650b ?

Almost had pulled the trigger already on an A23, but then learned about the PL23 in the FWB rim roundup. Will be used for riding road and gravel, lightweight touring, commuting, everything really. Rider and bike probably up to around 100kg (no loaded touring really).

Thanks.

KLabs
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Hi wassertreter, there is also a Pacenti SL23 700c ... viewtopic.php?f=3&t=111386

HillRPete
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KLabs, sure, but I'm looking for something in 650b, with brake tracks.

bm0p700f
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The H+ sons archetype come in up to 480g and are available in 36H drillings now so this may be a option for you.

WinterRider
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[quote="bm0p700f"]

Thanks for the links bm0p700f. Went thru the stiffness article once early morn.. will review again.

A 'from left field' inquiry.. why the bother to clear the brakes? Why not just employ a unit that brakes on the tire surface?

My inquiry via higher NDS tensions on a potential triplet goes to a radial NDS lacing... thinking those spokes would then pick up the hub torque ahead of DS spokes. On paper this arrangement would give around 120% NDS. 1x all outbound NDS sounds like a better arrangement [?]... this on a 135 rear 26" wheel.

bm0p700f
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Tortrional stiffness is no more dependent of spoke tension than lateral stiffness is so I cannot see how having NDS tension 120% of DS is ever going to help. Having NDS tension at 90% of DS tension is more than enough, I get away with a tension balance of 44%.

Penny farthing's use a spoon brake that braked the tyre apparantly it a sucide brake and a endover is likely. also the tyre will wear out and go pop. tyre brakes can only work on solid tyres.

WinterRider
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bm0p700f wrote:Tortrional stiffness is no more dependent of spoke tension than lateral stiffness is so I cannot see how having NDS tension 120% of DS is ever going to help.

Agreed... looking more to a downside angle. Just comes about potentially as the hub is on hand.

I'll goggle the spoon brake.. first reference to it I've come across.

http://sheldonbrown.com/rinard/wheel/index.htm Link to Rinard stiffness data per S Brown.

KLabs
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Hi bm0p700f, going by this reference, they are suggesting that spoke tension plays a part in a wheels radial and lateral stiffness. They are suggesting that when the rim can nolonger resist the lateral force being applied that the spokes (through spoke tension and spoke stiffness) then need to take over ...

Frontal stiffness
Coming back to our frontal stiffness test, the wheel is fixed by its axle, then crushed. The force applied is determined by software which records deformation at the same time. The wheels deform very little because of several parameters playing an important role in the vertical deformation. The rim height and its high frontal stiffness are not really prone to deform easily. Shallower rims obviously deform more easily than deep rims because they are not as stiff. The spokes also play a role: their number, crossing pattern, tension and spoke stiffness (material, cross section) all have an influence on overall vertical stiffness of the wheel. A low cross section spoke with low spoke tension will deform or lose its stiffness quicker than a high cross section and high tensioned spoke. The hub plays a role too, but its influence will be smaller than the two first.

Lateral stiffness
Beside this, when the rider pushes the pedals, the torque transmitted through the spokes deforms the wheel because of the bracing angles creating a lateral component: even when sitting in the saddle, the rear wheels moves between the brake pads when a rider stomps on the pedals. So the rear wheel must be as stiff as possible in order not to slip away when transferring the power. The lateral stiffness of a conventional wheel depends on several parameters. First of all, the rim will determine the stiffness of the wheel by its depth, its torsional stiffness and spoke length. Then, the spokes give the wheel integrity and play a role in the stiffness according to their tension and their cross section. Finally, according to Mavic, the most important parameter is the bracing angle, which is the distance between the flanges of the hubs.
Thus, in order to increase the lateral stiffness of a wheel one needs to:
- use a stiff and deep rim which will also comes with shorter spokes
- use larger spokes
- increase the bracing angle: hubs with flanges as far as possible
- high tensioned spokes to delay the moment when the wheel loses all its stiffness

xnavalav8r
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I've been busy...

bm0p700f
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Klabs I interpret that as the article says. Spoke tension does little to no effect on wheel stiffness unless the NDS spokes (it will alway be the NDS spokes unless something strange has happened) loose tension, then stiffness falls of a cliff. So Klabs I think you have the right idea. It is also what must be happening in a wheel under torque unless physics is as wrong. Physics was nearly wrong with speeding Italian Neutrino's but in the end it was only a time keeping error. The point is Physics dicates how a wheel behaves and that is how I look at a wheel.

So the article is right in every way as far as I can tell. The only thing I cannot confirm is there latteral stiffness recmendation for weight. I do think that is a little simplistic.

WinterRider
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bm0p700f wrote:Klabs I interpret that as the article says. Spoke tension does little to no effect on wheel stiffness unless the NDS spokes (it will alway be the NDS spokes unless something strange has happened) loose tension, then stiffness falls of a cliff. .

NDS spokes in the case of the triplet.. for instance.. are near or equal to DS spoke tension.

?

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