Thursday, March 4

Aero Diversion

I hate to disappoint Whareagle, but composites and aerodynamic characteristics are pretty much unrelated, at least when it comes to bikes. What he stated in his comment was very true, that good aero can pay real dividends for a cyclist. On the other hand, almost any shape that can be obtained from composites can be duplicated using a metal. Or vice versa.

Buddy, for example, has a mostly aluminum frame. That frame has a flat bottom to the top tube, and has the other tubes variously shaped. Buddy's wheels have metallic bladed spokes and a medium deep rim. There's no reason it couldn't have had a very deep rim. In fact, all of this is mild when it comes to shapes that can be made from metal. Ducommun Aerostructures, has several photos of wild looking one-piece metal components.Similarly, Accudyne has different wild photos. Between forming processes, casting, welding and such, any weird and wonderful shape can be made from metal, including some that would not be a good idea with composites.

Lest we harbor any lingering doubts, do not forget that the fastest aircraft (at least that we know of) was made of titanium. Namely, the photo below, from Wikipedia. Now THAT is aero!

A-12 from the Intrepid Museum, from Wikipedia

4 comments:

Rantwick said...

No offense, but I am enjoying your "carbon series" more than just about anything you've ever written. Goofs like me and cycling pundits are easy to find compared to experts in complex topics who are willing to demystify a little. Keep it up. I like it a lot.

whareagle said...

Yeah, but if Kelly Johnson had had access to the composites that are now available, don't you think he would've made the thing 'Leak-Proof' by using composites throughout the infrastructure? I think we're also dealing with a 'push' vs 'pull' situation between aircraft and bicycles or cars, or even motorcycles. Aircraft 'hang' by either their engines or wings, while bikes 'hug' or are suspended between their wheels. Same forces, but perhaps a different look at how gravity affects things? There's also air density...

But it'd be next to impossible to come up with some of the phenomenal shapes available for composites if you were only using metals, all while keeping the density just right. I still think carbon is the present and future of all vehicles, and I am also convinced that their life span will outlive stresses from normal metals like Aluminium and some steels, but give carbon its' due. Lighter, stronger, and most of the time, faster or more efficient. Right?

Anonymous said...

Perhaps the real question is not Aero or anything else "speed related" but longevity. How well does Carbon age in the sun compared to metals, and do composites really represent the best value for the typical (non racing) cyclist. I think these are the issues that need to be explored.

Big Oak said...

Interesting discussion. As carbon technology continues to develop, it'd be interesting to have a glimpse, say 20 years, into the future. Maybe nanotech carbon bikes?

I know very little about carbon fiber and appreciate your insight.

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