A /different/ helmet thread...

[Roger Thorpe]

Phil Cook wrote:
> Mark Thompson wrote:
>
>
>>>Yup. But, seeing the rules are you have to wear something silly on your
>>>head for racing, I thought that one looked interestingly less silly.
>>
>>Wot I thought. He'd look absolutely stupid in it, if it weren't for the
>>others in their 'normal' helmets.
>>
>>The silliest-looking of them all has to be the poor chap on the derny.
>
>
> Have you seen the helmets they wear on the big motors?
>
> http://www.bobkestrut.com/images/2005dortmund.jpg
What are those things on the helmets? is it some of of horn arrangement
so that they can hear the bike rider ?

--
Roger Thorpe

My email address is spamtrapped. You can work it out!

 

[Ian Smith]

On Sun, 25 Feb, Roger Thorpe <> wrote:

> Whoever wrote that press release doesn't know as much as they think they
> know about aerodynamics.

[snip snip]

> Apart from the nonsense about surface air tension, don't you actually
> *want* the flow to remain attatched down the rider's back?

Indeed. My understanding is that you want to disrupt laminar flow, so
you get a turbulent boundary layer, which will stay attached much
longer. While the turbulent layer has higher friction than the
laminar layer, it separates much less easily, and the form friction
is reduced. Since the form friction is (say) 90% or more of the total
drag, increasing the skin friction 50% but reducing form friction even
only 10% is a net gain.

I'd think that yes, it would be quite good to get a turbulent layer
that could stay attached down the back.

regards, Ian SMith
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