I have some pretty interesting results from an aerodynamics experiment I did with Kevin Reimer a few months ago, they arent 100% perfect NASA-quality-land-on-an-asteroid-in-space-engineering but I think its a pretty good proof of concept. The first images show the 3d scanning and digital reconstruction process, I captured about six full body scans with millions of datapoints each. Then I solidified them and brought them into a wind tunnel simulation. The red and grey side-view images show the frontal surface area used in the terminal velocity calculations. The terminal velocity figures are based on someone traveling through air thats at sea level (on a frictionless road). The takeaway in all this is that the regular helmets are actually faster because theres less surface area hitting the wind even though they create more drag. The drag difference is very very low between both helmet styles actually, but typical aero helmet shapes have a larger surface area hitting the wind, which lowers your terminal velocity. Even if you increase the riders weight to 220lbs the regular helmet seems to fair 3-6mph faster or more. I did calculations with wind at 22mph , 80mph and 220mph and they both have pretty similar drag coefficients, the aero helmet always comes out with slightly less drag but like I said I think because less surface area is hitting the wind the regular helmet is actually probably faster. There are a lot of ways of calculating aerodynamics and drag, I chose this method because it seemed to represent the problem at hand the most accurately. If any of you are rocket scientists and think theres a better way of calculating this please go ahead. Ive calculated the drag coefficient and importantly found the cross-section area which would be impossible to do without digitizing someone calctool.org/CALC/eng/aerospace/terminal because Also for fun and as an experiment control I ran the same test on someone with a box around their head, the drag coefficient is really bad for boxes and both helmet styles outperform boxes. TLDR: I think the fastest helmet style for downhill skateboarding is a charly-no-limit style design because they have the lowest profile and surface area, but a long-tail style design would probably out perform it slightly.
Posted on: Thu, 13 Nov 2014 20:28:32 +0000
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