Lightweight Challenge 700 -> 721.3gr!

[strobbekoen]

Just tell me what's scientific about that ?
I'll just use the same argument. Show me the data. If not, there's nothing scientific about that. Period.

[alienator]

What, good design principles? Gee, I thought you would have known all about that, dude. Make us proud and go read about 'em.

[MrCurrieinahurry]

tikka

[strobbekoen]

@mr. alienator:
Surely you are the only one ever to have designed any products from A..Z on this forum. Gee, congratulations.

[alienator]

Surely you are the only one ever to have designed any products from A..Z on this forum. Gee, congratulations.

Feel free to misread and misinterpret what you want.

But no matter what you mistakenly assume, thank you for your valuable tuition. It's been so instructive. Really. Honest. I now hang on your every word.

[chrism]

I don't even know what he's on about any more.

[RTW]

Rather than picking out all of the entertaining, but uninteresting points, maybe you could answer the question that stildt asked in 'capitals'?

Also, just wondered, were you bullied as a child?

[strobbekoen]

I don't even know what he's on about any more.

Me neither.. I have no idea what i mistakenly assumed.

[Frankie - B]

guys, let's behave. Shall we?

Is this about the lightweight challenge or about lew? Ah, Lw's

[CharlesM]

The talk on here is all about how carbon has some magical properties that means you can build your wheels differently. Quick reality check here - it has no magical properties, just a better specific stiffness than steel. This means that for a given stiffness a tension spoke can be lighter, but that doesn't change the way the spoke works.

Nobody is saying anything is magical, and honestly I think you're trying to find an arguement when we agree with what's being said in a very general sense... (I could be wrong though...)


Simply put, the different character of spoke material is exactly why you can build wheels differently...


Nobody is saying that "carbon" allows a hub to suspend it's self in the center of a rim... Of course spokes go from the rim to the hub. But they absolutely are actively working differently in Lightweights than in standard rims.


The different character of the materials allows one wheel to need no tension while standard spoked wheels do need tension.

And when the wheel doesn't need tension, it's not pulling it's self in 16 - 18 - 24 different directions just to stay in shape.


Nothing's wrong with what's in Sheldonbrown.com. What's wrong is you thinking it applies in the same way to a wheel that uses spokes that don't require being pulled at to have the proper stiffness...

Simply put, Lightweights spokes work virtually opposite of standard wheels.


The lightweights spokes work in support of the hub in multiple directions while Tensioned spokes do the opposite. Personally I like a wheel design that works on the principal of supporting the hub in many directions than a design that depends on applying constant stress.


So...
Going back to your first comment, I wouldn't call a wheel that performs this well and is this light and requires no nipples or hardware at the rim and whos spokes act opposite of those requiring stress to be "throwing away Advantage..."

[chrism]

Nobody is saying that "carbon" allows a hub to suspend it's self in the center of a rim... Of course spokes go from the rim to the hub. But they absolutely are actively working differently in their general state (not basic function, but in the execution of the function) than standard spokes do.

Working differently how? Are you suggesting they do something other than support the hub through tension?

But the different character of the materials allows one wheel to need no tension while standard spoked wheels do need tension.

The only difference is that the carbon is stiffer weight for weight. All that it provides is tensile force at the attachment points in exactly the same way a steel spoke does - nothing else.

Nothing's wrong with what's in Sheldonbrown.com. What's wrong is you thinking it applies in the same way to a wheel that uses spokes that don't require being pulled at to have the proper stiffness...

It applies in exactly the same way - if the spokes were pretensioned the stiffness would be doubled (or you could use half the weight of spokes for the same stiffness if current stiffness is sufficient).

The lightweights spokes work in support of the hub in multiple directions while Tensioned spokes do the opposite. Personally I like a wheel design that works on the principal of supporting the hub in many directions than a design that depends on applying constant stress.

This is the bit I don't understand, and where my accusation of "magic" comes in. What exactly are the spokes doing to support the hub apart from providing tensile force at the attachment point exactly the same as a steel spoke. The have no appreciable bending stiffness, so support neither shear nor compression forces.

If building a wheel that is not only lighter all round but with equal and frequently better stiffness if throwing away an advantage, what would you suggest?

I suggest you read Adrien's comments on how stiff LWs are.

Reading all these comments I wonder why I'm so concerned about the stiffness of building up low spoke count wheels with CX-Rays, when they will still be stiffer than these super light wheels people drool over.

[520 Dan]

I suggest you read Adrien's comments on how stiff LWs are.

Reading all these comments I wonder why I'm so concerned about the stiffness of building up low spoke count wheels with CX-Rays, when they will still be stiffer than these super light wheels people drool over.

To be fair, the LW that Adrien spoke of being flexy were gen II Obies, with the tune carbon axle. THis is probably part of the flex issue.

[chrism]

with the tune carbon axle. THis is probably part of the flex issue.

But I thought carbon was supposed to be stiff

[Miller]

Nobody is saying that "carbon" allows a hub to suspend it's self in the center of a rim... Of course spokes go from the rim to the hub. But they absolutely are actively working differently in Lightweights than in standard rims.
...
Simply put, Lightweights spokes work virtually opposite of standard wheels.

I have my doubts about that claim, they're the same physical structure carrying the same loads, after all. But to an extent, yes, in that what you're saying is effectively in agreement with what others have said about a design advantage being lost.

It's already been established in this topic that for practical purposes, an untensioned spoke has no compressive strength (Mavic R-Sys excepted). The point being made in many previous replies is that a tensioned spoke has the surprising property of acting as if it does have compressive strength. So a wheel built with tensioned spokes (almost all wheels) can resist lateral forces with the spokes on both side of the wheel. Whereas a wheel built with untensioned spokes (hello Lightweights) can only resist lateral forces with the spokes on one side of the wheel.

What I am prepared to believe about Lightweights is that the spokes are very stiff in elongation and that the rim is also stiff. This must compensate for the design's inability to take advantage of the engineering design of normal wheels. Which indeed is truly elegant. You take a collection of bendy spokes and a not-that-stiff metal rim, apply a lot of tension to one and a lot of compression to the other, and you end up with a light, cheap and durable structure.

I'm not dissing Lightweights here. They're a real engineering achievement. But the achievement is all about excellence and cleverness in composite construction techniques.

[CharlesM]

Working differently how? Are you suggesting they do something other than support the hub through tension?

"lots of stuff out of context or ignoring the point"

This is the bit I don't understand, and where my accusation of "magic" comes in. What exactly are the spokes doing to support the hub apart from providing tensile force at the attachment point exactly the same as a steel spoke. The have no appreciable bending stiffness, so support neither shear nor compression forces.

Do you really not understand what the difference is when a wheel can be built without tensioning the spokes?


Again you're saying in one line that the Lightweights perform exactly the same way, by tensioning something (when they really don't)

Then you use the word "support", ignoring the part where you try and talk about standard wheels needing tension...



You're too busy argueing with yourself for me to help...

And no, I'm not argueing Adrien at all, and he wasn't argueing with me. He simply said that Obermeyers are less stiff than standards, but the gen 3 using all carbon (though no magic was mentioned) are 30% stiffer

and guess what, they did it with more carbon... not more tension