Track Helmets

hippy

I think you've got it the wrong way around..

From the site mentioned above:
"The wide-spread ANSI approved helmet Bell V1 Pro gains around 9.8% compared to a bald head"

The context is "increasing aero drag", so it basically states that wearing an approved aero helmet is aerodynamically worse than a bald head by 9.8%.

Also, you can't calculate a performance increase/decrease of x% based on the drag increase/decrease of x%. The drag percentage isn't directly related to speed. So 5% better aerodynamics isn't necessarily 5% faster..

Also quoting that site:
"New wheels offer the largest aerodynamic advantage with the bicycle"
but it goes on to mention front disc problems in winds and the cost.

So, maybe you could get a better helmet if you can afford it and swap your spokes for bladded ones and maybe some deep, aero rims?

hippy

bikeguy2

Hippy.. no a standard helmet has worse aero drag than a bald head, a good aero helmet has much better drag than a bald head. As for speed increases, since drag is proportional to velocity cubed, a 10% reduction in drag would cause a 3% increase in speed at constant power. air drag (watts)= VA*VA*VG*0.5*air density (in kg per cubic meter) *frontal area (in meters squared)*drag coefficient (dimensionless number) Va is air velocity, Vg is ground velocity, in meters-sec of course.

hippy

Yep, as per: "The Bell Stratos, an ANSI approved helmet, increases the
aero drag by approximately 1.3 % over a bald head."

and: "Aero helmets, as they are used for racing, which do not however
meet the ANSI safety requirements, reduce the aero drag by approximately 2% compared to a bald head or a rubber cap over the hair."

But I'm not sure I'd call 2% drag reduction "much better" than a bald
head. Maybe at the elite level 2% is a lot, but not for me

Anyway, 2% less drag is MUCH less benefit than the 5% _time_ benefit
some people were calculating. It's only a 2% _drag_ decrease which is
NOT 2% speed increase.

Ahh.. too much maths not enough riding!

hippy

leifclarke

That Bell (razor?) that the Kiwi rode in the pursuit is cool. You don't see many of those around anymore. I've always been curious why Bell stopped making them. Also, why Troxel stopped making the radius titanium. Both really cool lids from the mid 90's.

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