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Home > Forum > Triathlon Forum > Triathlon bike test in Europe – Scott Plasma 2 won, Cervélo and Specialized canceled

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Re: Triathlon bike test in Europe – Scott Plasma 2 won, Cervélo and Specialized canceled [Frank Day] [ In reply to ]
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Tom A.
Mar 14, 09 7:13
Post #126 of 135 (4964 views)
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*As can also be demonstrated by simply reading the wind tunnel specifications found here:

http://lswt.tamu.edu/...ance_Characteristics

which report that the boundary layer is only 1.5" thick, i.e., way below any frame member on a bicycle.
Missed this. While I guess it would be possible to engineer a wind tunnel such that wind speed 1.5 inches from the wall/floor is within .99 of the speed at the center of the tunnel, that goes against my under standing of wind speed characteristics.

Either way, it is not possible to have it both ways. If that were true, then the results would be valid for still air but not necessarily for riding into a substantial head wind.

Hey Frank...look at this photo and you'll see one of those clever ways that engineers have figured out how to minimize that pesky boundary layer effect you're so worried that they're ignoring ;-)

http://twitpic.com/228jx/full
http://bikeblather.blogspot.com/
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Re: Triathlon bike test in Europe – Scott Plasma 2 won, Cervélo and Specialized canceled [frank z.] [ In reply to ]
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Tom A.
Mar 14, 09 7:22
Post #127 of 135 (4958 views)
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I think first of all bikes are built to be ridden by an athlete. With a test without rider we know now a Scott alone in the Windtunnel is the best choice. If you have alot of races like this on your schedule, the buy it. If not, then you have to wait for a serious test with a pedaling rider on the bike.

I think you need to read the paper that Andy Coggan links to SO often (such as previously in this thread itself) describing the correlation between tunnel data and actual field measurements.


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But:

Fuer die abschliessende Bewertung der aerodynamischen Qualitaet haben wir daher nur die reproduzierbaren Messungen der nackten Raeder ohne Fahrer verwendet.

makes not so much sense.

It makes perfect sense if you have read and understood the Kyle data that Doc C also refers to often showing the correlation of bike alone vs. bike with rider drag (with the rare exception of bikes like the Trimble, which is VERY different than the bikes being discussed).
http://bikeblather.blogspot.com/
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Re: Triathlon bike test in Europe – Scott Plasma 2 won, Cervélo and Specialized canceled [WRE] [ In reply to ]
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Tom A.
Mar 14, 09 7:26
Post #128 of 135 (4956 views)
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Did you read the whole test? Then you would've realized that the bias was just to high with rider.

The bias?, or the "noise"?


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The only rational hing to do is to put a kind of plastic dummy on the bike.

Or...refine the test protocol ;-)



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Btw: I don't wanna offend you and many others but this kind of post of know-it-alls, who try to sell their half knowledge makes 80-90% of all those posts here rather useless. I rather trust a renowned bike magazine than anonymous slowtwitch posters :-)

Are you talking 'bout me? :-)
http://bikeblather.blogspot.com/
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Re: Triathlon bike test in Europe – Scott Plasma 2 won, Cervélo and Specialized canceled [Tom A.] [ In reply to ]
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Zarskiman
Mar 14, 09 12:07
Post #129 of 135 (4908 views)
Test is flawed, Euros have such a fetish for everything Scott- it's outrageous. Ski, bike, they just dig it. Conflict of interest makes this test non-legit.
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Re: Triathlon bike test in Europe – Scott Plasma 2 won, Cervélo and Specialized canceled [Tom A.] [ In reply to ]
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WRE
Mar 15, 09 10:19
Post #130 of 135 (4853 views)
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Did you read the whole test? Then you would've realized that the bias was just to high with rider.

Quote:
The bias?, or the "noise"?
You're right, bias is wrong. It's a random error. Think that's what you mean with "noise".


In Reply To:
The only rational hing to do is to put a kind of plastic dummy on the bike.

Quote:
Or...refine the test protocol ;-)
How?


In Reply To:
Btw: I don't wanna offend you and many others but this kind of post of know-it-alls, who try to sell their half knowledge makes 80-90% of all those posts here rather useless. I rather trust a renowned bike magazine than anonymous slowtwitch posters :-)

Quote:
Are you talking 'bout me? :-)
No, generally
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Re: Triathlon bike test in Europe – Scott Plasma 2 won, Cervélo and Specialized canceled [WRE] [ In reply to ]
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RChung
Mar 15, 09 11:08
Post #131 of 135 (4840 views)
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The only rational thing to do is to put a kind of plastic dummy on the bike.

Quote
Or...refine the test protocol ;-)[/quote] How?
Depends on what the source of the error is (mechanical, positional, architectural), but in some wind tunnels the precision of estimated CdA of a bike with rider is around .001 - .002 m^2.
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Re: Triathlon bike test in Europe – Scott Plasma 2 won, Cervélo and Specialized canceled [RChung] [ In reply to ]
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WRE
Mar 17, 09 13:52
Post #132 of 135 (4748 views)
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The only rational thing to do is to put a kind of plastic dummy on the bike.

Quote
Or...refine the test protocol ;-)[/quote] How?
Depends on what the source of the error is (mechanical, positional, architectural), but in some wind tunnels the precision of estimated CdA of a bike with rider is around .001 - .002 m^2.
I thought the problem of the rider is that he will always sit a little bit different or move and falsify the result because of that...
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Re: Triathlon bike test in Europe – Scott Plasma 2 won, Cervélo and Specialized canceled [WRE] [ In reply to ]
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Andrew Coggan
Mar 17, 09 14:26
Post #133 of 135 (4725 views)
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In Reply To:
In Reply To:
In Reply To:
The only rational thing to do is to put a kind of plastic dummy on the bike.

Quote
Or...refine the test protocol ;-)[/quote] How?
Depends on what the source of the error is (mechanical, positional, architectural), but in some wind tunnels the precision of estimated CdA of a bike with rider is around .001 - .002 m^2.
I thought the problem of the rider is that he will always sit a little bit different or move and falsify the result because of that...
The imprecision that Robert mentions (i.e., CdA being reproducible to 0.001-0.002 m^2) includes - and indeed, mostly reflects - the source of variation that you describe.
Last edited by: Andrew Coggan: Mar 17, 09 14:27
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Re: Triathlon bike test in Europe – Scott Plasma 2 won, Cervélo and Specialized canceled [WRE] [ In reply to ]
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Sam Apoc
Mar 17, 09 14:28
Post #134 of 135 (4722 views)
The cheapo magazine should have just purchased the spec and cervelo frames. They don't need permission to test them.
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Re: Triathlon bike test in Europe – Scott Plasma 2 won, Cervélo and Specialized canceled [Carl] [ In reply to ]
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SuperDave
Mar 31, 09 10:16
Post #135 of 135 (4604 views)
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Doubt fear had anything to do with it.


100% speculation on my part, but I can see it going down like this: any bike company with a reputation for aero prowess and a history of megabucks spent on tunnel time might ask for details on exactly how a magazine intends to conduct a test like this...and if a "wrong" answer (or no answer) can't be resolved, they elect not to participate.


Carl


(disclaimer: I don't know if we were even contacted...might start developing a SuperDave complex ;-) )

I'd hardly call it a complex. It's my job.
-SD
https://www.kickstarter.com/...bike-for-the-new-era
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