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From: ron@argus.UUCP (Ron DeBlock)
Newsgroups: net.cycle,net.auto,net.politics
Subject: Re: re Re Seat belts, Helmets and Freedom of Choice
Message-ID: <411@argus.UUCP>
Date: Tue, 29-Jul-86 17:14:59 EDT
Article-I.D.: argus.411
Posted: Tue Jul 29 17:14:59 1986
Date-Received: Fri, 1-Aug-86 06:42:18 EDT
References: <473@water.UUCP> <2975@pixar>
Organization: NJ Inst of Tech., Newark NJ
Lines: 46
Xref: watmath net.cycle:1876 net.auto:11978 net.politics:17843

In article <2975@pixar>, good@pixar (All of the good ones are taken.) writes:
> In article <473@water.UUCP> kgdykes@watbun.UUCP writes:
> >
> >>From: junk@ur-tut.UUCP (Jan Vandenbrande)
> >When there is impact with the head, the greatest damage comes from
> >SUDDEN DECELERATION of the brain against the skull, helmets don't help.
> 
> This is the second such claim I have seen, and I'd love to have
> someone explain it.  My understanding is that the human head can
> safely decellerate at about 80 gees, and that with a good helmet
> a 200 gee decelleration can be reduced to below 80 for the head.
> In other words, the only thing a helmet really can do is lessen
> the severity of a decelleration.  The relative accelleration of
> the brain vs the skul has got to be proportional to the accelleration
> being applied to the skull by the sidewalk, right?
> 
> 
> -- 
> 		--Craig
> 		...{ucbvax,sun}!pixar!good


Craig, you are on the right track.  I am not sure about the numbers you claim
and I have no way to look them up.  Some references, please?

Helmets and seatblets (and "controlled crush" in car frames) work by
absorbing some of the energy of impact, thereby reducing the amount of energy
that must be absorbed by the skull and other parts of the body.
In effect, the rate of decelleration is DECREASED.  In a helmet, the plastic
shell flexes to absorb some energy, the rest is aborbed the the foam lining.

My brother's helmet SPLIT IN TWO in a crash (this was NOT a cheap helmet).
He messed up his leg and get lots of scrapes, but there was NO damage to
his head.  The helmet he was wearing was certified to pass the Snell test
(I think) which involves dropping a heavy, pointed object onto the helmet,
which must sustain no damage.  I don't remember the weight or height of the
object, but your head would NOT survive such a test.  Maybe someone could
enlighten us.
-- 
Ron DeBlock	KA2IKT

	uucp: ...!{allegra, ihnp4}!bellcore!argus!ron
	      ...!{siesmo, allegra!princeton}!caip!andromeda!argus!ron
	arpa: argus!ron@bellcore.arpa

"Beware of programmers carrying screwdrivers."