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 Post subject: AeroAirheads
PostPosted: Sun Jul 02, 2006 1:50 am 
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Joined: Thu May 04, 2006 4:43 pm
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Location: Wherever there's a mountain beckoning to be climbed
I propose a sister board "AeroAirheads", with a singular focus on bicycle aerodynamics, to include aerodynamic stiffness. Weight, function, durability, maintainability, and ability to support power output must not be considered.


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 Post subject: AeroAirheads
Posted: Sun Jul 02, 2006 1:50 am 


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 Post subject: Re: AeroAirheads
PostPosted: Wed Jul 06, 2011 2:27 pm 
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Joined: Thu Feb 03, 2011 2:28 pm
Posts: 380
Perhaps not a sister board, but maybe just a thread.

Here are a few for starters:
1. Does anyone have a link to the Velonews article that did a wind tunnel comparison of different wheels? I can't remember where I saw the reference to it.

2. Does anyone know how to translate grams of drag into watts of power? The Hed website has an interesting wheel comparison graph (http://www.hedcycling.com/aerodynamics.asp), but i don't know how to translate the differences to real-world performance. The graph, for example, claims that there's an 80 gram difference at 10 degrees of yaw between a Stinger Disc and Zipp Sub-9. Taking this at face value and assuming no wind and a constant 300 watts, what would difference (if any) would this have on speed?

3. Just how much difference is there in aerodynamics of different discs or 90mm section rims? There is substantial variation in the weights- in discs, for example the Hed Stinger disc is a claimed 1,130g, Zipps are around 1,000g and carbonsports claim that one version of thier discs only weighs 780g. Are aero differences between brands substantial enough to offset a 200g weight advantage on the slight rises and accelerations of a typical TT course?

4. Has anyone had a session in the wind tunnel with Drag2Zero?


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 Post subject: Re: AeroAirheads
PostPosted: Wed Jul 06, 2011 2:57 pm 
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Location: Melbourne, Australia
HammerTime2 wrote:
with a singular focus on bicycle aerodynamics


http://biketechreview.com/forum/1-general-discussion

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 Post subject: Re: AeroAirheads
PostPosted: Wed Jul 06, 2011 3:09 pm 
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Joined: Wed Dec 15, 2004 10:54 am
Posts: 1396
Location: Melbourne, Australia
Privateer wrote:
Does anyone know how to translate grams of drag into watts of power?


Found this on slowtwitch - http://forum.slowtwitch.com/forum/Slowtwitch_Forums_C1/Triathlon_Forum_F1/Drag_differences_(watts_or_seconds_per_40k)_for_different_bottle_set_ups_P2570287-3

Quote:
0.1 lbs (50 g) of drag (at 30 mph) = 0.5 s/km = 5 W = 0.005 m^2 CdA = 0.0005 Crr

The above rule-of-thumb (which refers to changes) is based on various assumptions/rounding everything to a 1 or a 5, but is fairly accurate and hence quite handy when doing in-your-head (or back-of-the-envelope) calculations.

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Last edited by Dalai on Wed Jul 06, 2011 3:11 pm, edited 1 time in total.

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 Post subject: Re: AeroAirheads
PostPosted: Wed Jul 06, 2011 3:11 pm 
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As far as grams of drag equating to watts saved, I believe the simple math is a 10:1 ratio, so 100 grams of drag saved equals 10 watts fewer needed to achieve the same speed. I think the real math is more complicated, but its one of those cases where the simple math is close enough.

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 Post subject: Re: AeroAirheads
PostPosted: Wed Jul 06, 2011 4:17 pm 
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Joined: Thu Feb 03, 2011 2:28 pm
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Thanks, that's really useful.

Hed's claim that their disc has 160g less drag than Zipp's at 15 degrees of yaw is a pretty big one then. 16 watts? Really?


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 Post subject: Re: AeroAirheads
PostPosted: Wed Jul 06, 2011 5:08 pm 
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Location: San Francisco, CA
Harumph. Grams are not a unit of force. Harumph.

Hats off to Tour magazine for getting this right.

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 Post subject: AeroAirheads
PostPosted: Wed Jul 06, 2011 5:16 pm 
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Joined: Tue Jun 22, 2004 11:42 pm
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Location: lat 38.9677 lon 77.3366
So how aero is Sparticus?

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 Post subject: AeroAirheads
Posted: Wed Jul 06, 2011 5:16 pm 


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