by youngs_modulus on Sun Jun 01, 2014 7:24 pm
Calnago, the phrase "cross sectional area" in this context implies a cutting plane normal to the major axis of the spoke. In the world of engineering, there's no debate about this question.
Ergott and WMW have covered your stiffness question quite effectively, so I'm just adding my voice to the chorus. Adding cross-sectional area to spokes increases the stiffness of the spokes in direct proportion to the increase in area. It doesn't help that Sapim makes some strange claims about strength and stiffness when comparing Lasers to CX-Rays. Since CX-Rays are just flattened Lasers, they can't be either stronger or stiffer than Lasers. (Cold working isn't a factor here; the drawing process alone cold-works butted spokes as much as they *can* be cold-worked). Sapim's marketing claims make no sense to mechanical engineers, but they're pretty effective at confusing consumers.
And adding more tension to an already-tensioned wheel does not make it stiffer. For example, if your spokes are at 100 kgf, and you crank the tension up to 125 kgf, your wheel will not be measurably stiffer. Both Damon Rinard and Jobst Brandt have answered this question quite well with both theory and experiment.
In truth, though, experiment is not required. It's a trivial question from an engineering perspective, even if it's counterintuitive to non-engineers. It's analogous to someone at the dawn of iron ships asking whether you can build a ship that floats from a material, iron, that is heavier than water. The answer is obvious to anyone with an engineering or science background--no physicist would have needed an experiment to convince himself that a steel ship could float--but non-scientists might want to see a floating steel ship before they fully buy the idea. That's not unreasonable, I guess.
Cheers,
Jason