AW på ZRX wrote:
>>> Sikkerheden er helt i top på en carbon/kevlar racer hjelm.
>>
>> Er det nu rigtigt.....
>>
>> "Polycarbonate helmets generally transmit fewer Gs to the head in our
>> testing than fiberglass-shell lids, even when certified to the same
>> standards. "
>>
>> citat fra :
>>
http://www.motorcyclistonline.com/gearbox/motorcycle_helmet_review/
>>
> ....og til dem der ikke gider læse et hele:
> The stiffest helmets in the Big Drop test, the Arai Tracker GTs, hit our
> hypothetical head with an average of 243 peak Gs. The softest helmets, the
> Z1R ZRP-1s, bonked the noggin with an average of 176 peak Gs. This is a
> classic comparison of a stiff, fiberglass, Snell-rated helmet, the Arai,
> against a softer, polycarbonate-shell, DOT-only helmet, the Z1R. OK. So
> let's agree that we want to subject our heads to the minimum possible G
> force. Should we pick an impressive, expensive
> fiberglass/Kevlar/unobtanium-fiber helmet-or one of those less-expensive
> plastic-shelled helmets?
> Conventional helmet-biz wisdom says fiberglass construction is somehow
> better at absorbing energy than plastic-something about the energy of the
> crash being used up in delaminating the shell. And that a stiffer shell lets
> a designer use softer foam inside-which might absorb energy better.
> Our results showed the exact opposite-that plastic-shelled helmets actually
> performed better than fiberglass. In our big 3-meter hit-the high-energy
> kind of bash one might expect would show the supposed weaknesses of a
> plastic shell-the plastic helmets transferred an average of 20 fewer Gs
> compared with their fiberglass brothers, which were presumably designed by
> the same engineers to meet the same standards, and built in the same
> factories by the same people.
> Why is this? We're guessing-but it's a really good guess: The EPS liner
> inside the shell is better at absorbing energy than the shell. The
> polycarbonate shells flex rather than crush and delaminate, and this
> flexing, far from being a problem, actually lets the EPS do more of its job
> of energy absorption while transferring less energy to the head.
Så er det nok derfor at de laver et Carbon/Kevlar/Glasfiber mix . . .