Snell standards (was re: track event virgin)
Fisher, Scott
Scott_Fisher at intuit.com
Tue Jan 23 10:10:57 EST 2001
Mike Pshenishny writes:
> In reference to the SA vs. M Snell ratings, I believe the
> difference is this: There is no difference between the
> "crash" ratings, they both face the same requirements to
> be approved. There is a difference in that SA is
> fire-resistant, while the M is not. Generally, in a
> crash with a motorcycle, you probably wouldn't need the fire
> protection, so the M helmets should be somewhat cheaper.
While flame resistance is part of the SA standard that's missing from the M
standard, there's a fair bit more to it than that. The Snell tests work by
placing accelerometers inside the helmets and then dropping them from a
specified height onto a series of anvils of different shapes. The SA
helmets have an additional anvil -- roll bar shaped -- that the M helmets
don't. Both standards test for two impacts at each site on the helmet
against the flat and hemispherical anvils, and one against the edge anvil;
the SA helmets further test for three impacts against a roll-bar shaped
anvil, at each test site on the helmet. Deceleration cannot exceed 300g for
any test, nor can there be any breakage of the helmet; either is cause for
rejection.
The rationale behind this (as it was explained to me when the standard in
question was SA-85 versus M-85) is that in a racing car, you're more likely
to have multiple impacts inside the car as it rolls, flips, or spins and get
tagged by the rest of the field coming through (think NASCAR), while in a
motorcycle there's more likely one or two impacts -- a bounce and a long
slide. The question of whether there's additional friction-resistance
testing on M-spec helmets is left to those who ride (I don't, I just move
over and point you guys by :-).
A good friend went into the wall backwards at Portland in May, moving about
80 MPH. His head hit the back support on his racing seat hard enough that
one of the nifty little vents on the forehead of his helmet actually popped
out of the shell from the impact. The only long-term indication of brain
damage is that he hasn't quit racing, but that could be demonstrated to be a
prior condition... I intend to buy a helmet exactly like his, since it's
about time to replace my old hat. I do NOT intend to test it the same way,
if I can help it.
Interested readers can find out more at http://www.snellfoundation.org/,
including reading the actual test procedures and standards (the SA 2000
standards are at http://www.snellfoundation.org/standards/sa20std.html) and
how much more stringent the Snell standards are than the DOT. It's pretty
interesting reading, if you're at all fond of your head. :-)
--Scott Fisher
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