CBRVFR

I read about this in Motorcyclist , which was the magazine most critical about the Snell standards related to second-impacts. To summarize their criticism, and someone please correct me if I have this wrong - the Snell standard, which requires a helmet sustain a second impact, requires the manufacturers to use comparatively stiffer EPS lining, which can impart a greater amount of force to a rider on the first impact than a DOT helmet. The DOT standard only requires testing for a single impact, and allows the use of a softer EPS liner. Your number of impacts may vary..

In the opinion of some people whose judgment I trust, there are significant issues with other aspects of the DOT testing regimen, which you can read about here. in about post 12 and thereafter.

In this case, Snell is acknowledging that smaller heads weigh less than larger ones, (which, in my experience, are often filled with heavy delusions of grandeur..) So they're allowing lighter headforms for smaller helmets, which will result in higher allowable secondary impact velocities for those smaller helmets, which in turn, will allow the use of softer EPS.

I think.

Motorcyclist is acting like this is a major breakthrough, probably hoping to regain some advertising revenue that they lost by pissing off Arai and Shoei, among others.

The most significant line in the story was that the head of Snell said there would be huge safety gains in the helmets made in the next 10 to 15 years.
From
Final Draft 2005 STANDARD FOR PROTECTIVE HEADGEAR

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luvtolean

Seems like a good change to me, provided it's based on data, and not "heat" for not passing another standard. The more accurately a standard's testing regiment simulates the use environment, the more you learn, and the better the product will operate in its application.

The last time I seriously participated in a helmet discussion, I was downright angry, and quite frankly I chose to not participate in the supermoto thread for one reason:

MANY MOTORCYCLISTS AND SELF-PROCLAIMED IDIOTS...ERRR...EXPERTS THINK IF YOUR HELMET PASSES SNELL, IT'S AS PROTECTIVE AS ANY OTHER HELMET.

Arguing with a cheap ass that holds this belief dear is like trying to get him to change gods. And quite frankly, I don't care enough about it anymore to argue with them.

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CBR929RE

wait, so a smaller head has greater velocity on a second impact than a larger head? shouldn't that same smaller head have greater velocity on the first impact too? or am I reading into this wrong?

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luvtolean

Actually, a smaller head applies less energy to the EPS lining on impact due to its lighter weight. Because the lining works by crushing, a smaller head will crush less thickness of EPS than a bigger one, for the same impact, meaning the brain in a smaller head ultimately sees a larger force if the density/yield strength of the EPS is the same as for fatheads.

This allows helmet makers, and may even force them to, use different liner materials in different sized helmets, tailored to the user.

Good stuff.

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Someone needs to present the facts and the physics rather than just the rhetoric. Poor old Carmelo doesn't understand the physics of a motorcycle. - Jerry Burgess, on spec tires and changing engine rules

Hammer

It could also be construed that a smaller headed person also has less brain matter, and does not need as much protection.

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CBR929RE

that makes sense LTL but I'm still wondering why they are only changing the second impact velocities for smaller heads. both impact velocities should be changed for a smaller head, right? its not like the smaller head is equal to the larger for first impact then all of a sudden for that second impact things change.

I like their thought process but they have to keep extrapolating.

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if you can't fix it with duct tape, you haven't used enough.

CBRVFR

That train's never late.

__________________
"...the TV also never took away the screwdriver and shoved it up the repairman's ass."

Our own Mr.2nd Amendment, explaining the difference. Perfectly.

Rich Herald, the Gentle Giant

gt702

First impact is based on the velicity you are traveling when you strike something, so this should be the same for everyone. (for some reason the little people won't stay on mopeds where they belong )

For the second impact you get into complicated things like moments of inertia, and much like a light wheel, the rotation is quicker when the MOI is low. Meaning the force of the stretching spine will slam the lighter head back to the pavement at a faster speed. ... or something like that

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CBR929RE

sounds like a good explanation to me, thanks

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