Road Helmet Aerodynamics

Discuss light weight issues concerning road bikes & parts.
tanhalt
Posts: 109
Joined: Wed Dec 27, 2006 6:36 pm

by tanhalt

Valbrona wrote:
justkeepedaling wrote:0-180? What the hell are you talking about. Are cyclists now riding in reverse?


Yaw is not the direction someone is cycling in, it is the direction of air flow. And if anyone who has ever ridden a bike knows, you can actually get wind direction in a 360 deg. fashion. Vector analysis does not translate to real life cycling very well - cycling speeds are generally quite low and variable, and wind speeds can be comparitively high. Vector analysis works with objects that move at higher speed than your average cyclist.


...maybe for YOU :roll:

by Weenie


NGMN
Posts: 1536
Joined: Mon May 30, 2005 7:13 am

by NGMN

Valbrona wrote:
justkeepedaling wrote:0-180? What the hell are you talking about. Are cyclists now riding in reverse?


Yaw is not the direction someone is cycling in, it is the direction of air flow. And if anyone who has ever ridden a bike knows, you can actually get wind direction in a 360 deg. fashion. Vector analysis does not translate to real life cycling very well - cycling speeds are generally quite low and variable, and wind speeds can be comparitively high. Vector analysis works with objects that move at higher speed than your average cyclist.


What? Vectors has nothing to do with magnitude. You can calculate yaw whether you are traveling at 1mph or 100mph.

I've seen data which suggests less than 10% of all wind is over 20mph.

Anyway, play with this calendar and then talk to us about 180 degree wind:
http://www.wing-light.de/TechTalk/yaw.htm

mjduct
Posts: 662
Joined: Tue Dec 27, 2011 2:19 pm

by mjduct

Epic-o wrote:
JamieL wrote:
Image



I'm so surprised the Catlike faired so well in that test, I swear it makes my neck hurt in the crosswinds it catches so much air, but in South Texas from April-October it's totally worth it!!! :thumbup: :thumbup: :thumbup:

durkonion
Posts: 188
Joined: Sat Dec 22, 2007 4:17 am

by durkonion

Valbrona wrote:
justkeepedaling wrote:0-180? What the hell are you talking about. Are cyclists now riding in reverse?


Yaw is not the direction someone is cycling in, it is the direction of air flow. And if anyone who has ever ridden a bike knows, you can actually get wind direction in a 360 deg. fashion. Vector analysis does not translate to real life cycling very well - cycling speeds are generally quite low and variable, and wind speeds can be comparitively high. Vector analysis works with objects that move at higher speed than your average cyclist.

Yes, wind comes from all directions, but when are you ever travelling slower than the wind? The yaw angle you care about is the direction of the air relative to the rider. Unless you aren't pedalling for some reason, that will most likely be between 0-30 deg.

Murphs
Posts: 1117
Joined: Thu Feb 05, 2009 12:04 am
Location: Gold Coast, QLD, Australia

by Murphs

bricky21 wrote:
Murphs wrote:The Kask helmets are filled in like that, that is not a helmet cover. Sky have been using them for a number of years in the classics etc

Removable covers are illegal however.


Which model? The Sky rider behind looks to be using a standard helmet. I can't find that helmet on the Kask website, but I can't find a helmet cover either. Iirc Cav was wearing a cover in the WC road race on his specialized prevail.


Just because they're wearing one, doesn't mean you can buy one.

There was some murmur that if the UCI had actually seen Cav's helmet cover before the RR started, it would have been disallowed, but they didn't.

HillRPete
Posts: 2292
Joined: Tue Apr 12, 2011 8:08 am
Location: Pedal Square

by HillRPete

Valbrona wrote:
justkeepedaling wrote:0-180? What the hell are you talking about. Are cyclists now riding in reverse?


Yaw is not the direction someone is cycling in, it is the direction of air flow. And if anyone who has ever ridden a bike knows, you can actually get wind direction in a 360 deg. fashion. Vector analysis does not translate to real life cycling very well - cycling speeds are generally quite low and variable, and wind speeds can be comparitively high. Vector analysis works with objects that move at higher speed than your average cyclist.

I'm not sure how relevant the 180° yaw case is though -- anyway you would probably like to have a high drag in that case, so you catch more air and sail off the front of the group! :beerchug:

Epic-o
Posts: 621
Joined: Tue Nov 20, 2007 7:18 pm

by Epic-o

Valbrona wrote:Vector analysis works with objects that move at higher speed than your average cyclist.


:roll: :roll:

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MajorMantra
Posts: 293
Joined: Mon Nov 02, 2009 8:38 pm

by MajorMantra

Roeboe wrote:I think the main reason is for keeping the head wind and water free, since you lose most energy (heat) trough your head.


Myth!:

http://www.guardian.co.uk/science/2008/ ... nbehaviour

Illuminate
Posts: 404
Joined: Mon May 24, 2010 4:18 am
Location: Australia

by Illuminate

Have had my prevail for a year now - would not rate it very well for two reasons:
Build quality is very very ordinary compared to my met strad. Moldings are very poor with days hanging off. Stickers are peeling. Typical made in china effort cleverly disguised with a made in Macau sticker - never again!
2. Chin straps vibrate when over 30kmh. Have tried tightening as per instructions but they loosen promptly and start buzzing again.

Just my thoughts. Some love it and swear by it and I respect that.
Peace
I

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HammerTime2
Posts: 5428
Joined: Thu May 04, 2006 4:43 pm
Location: Wherever there's a mountain beckoning to be climbed

by HammerTime2

It may not be as common as [0,30], but [90,180] yaw is possible on a bike. For example, strong predominantly tail wind up a steep climb. And yes, vector analysis applies regardless of speed, as long as you know how to apply it.

rodebaron51
Posts: 348
Joined: Sat Dec 17, 2011 4:38 pm
Location: Netherlands

by rodebaron51

I think the closed helmets are not for aerodynamics, but to keep the wind (thus cold) out!
Pascal

2012 Colnago C59 MTBK Camapgnolo Hyperon Ultra 2 and Campi SR11
2014 Merida Big 99 CF team fully
2015 Pinarello F8 Sky Campagnolo Bora Utra 2 and Campi SR11 EPS (RIP after crash)
2016 Trek Mad-One Limited Team Edition

tanhalt
Posts: 109
Joined: Wed Dec 27, 2006 6:36 pm

by tanhalt

rodebaron51 wrote:I think the closed helmets are not for aerodynamics, but to keep the wind (thus cold) out!


They do both.

natiedean24
Posts: 367
Joined: Wed Jun 10, 2009 2:16 pm
Location: Austin, Texas
Contact:

by natiedean24

Vector analysis works just fine and dandy for objects as slow as cyclist - even one as slow as myself.

http://s321476941.online.de/hedgermany/ ... ulator.asp

hna
Posts: 271
Joined: Thu Nov 17, 2011 8:26 pm
Location: Norway

by hna

Valbrona wrote:
justkeepedaling wrote:0-180? What the hell are you talking about. Are cyclists now riding in reverse?


Yaw is not the direction someone is cycling in, it is the direction of air flow. And if anyone who has ever ridden a bike knows, you can actually get wind direction in a 360 deg. fashion. Vector analysis does not translate to real life cycling very well - cycling speeds are generally quite low and variable, and wind speeds can be comparitively high. Vector analysis works with objects that move at higher speed than your average cyclist.


What the hell are you talking about? 360 degrees almost only applies when the rider is standing still. You don't have to ride very fast before airflow relative to the rider never exceeds 20 degrees of yaw.

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slyboots
Posts: 445
Joined: Sun May 10, 2009 3:31 pm
Location: Russia, Moscow

by slyboots

hna, 'never' is a rather strong word, isn't it? Try playing with the Apparent Wind Calculator from the link above (it's buggy in km/h, so leave it in mph) - you'll see that it's entirely possible to have sidewind of more than 20 degrees.

by Weenie


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