demands
even more
Shock Limits – Peak G
In a crash, a good helmet limits the shock transmitted to the wearer’s head.
These limits, generally expressed in G’s, multiples of gravity, are comparable
for M2010, DOT and ECE 22-05. The critical difference for M2010 is that helmets
must continue to limit the shock for much more severe crash impacts.
Impact Surfaces
When
a rider crashes, there’s no telling what he’s going to hit: a broad, flat roadway
maximizing the contact area with the helmet or a shaped surface which will concentrate
the loading to a small portion of the helmet shell. Broad flat surfaces
produce higher levels of shock immediately but load concentrating surfaces may
collapse the helmet wall and then transmit uncontrolled levels of shock directly
to the wearer’s head. A good helmet must be able to contend with both types.
Coverage
A crash impact might fall anywhere on a rider’s head. Good
helmets, as much as possible, will get between the rider and reasonably likely
impacts
to provide protective coverage. M2010 and DOT specify test lines and allow test
impacts centered anywhere
on or above those lines. ECE 22-05 specifies the test impact locations directly.
Shell Penetration
A good stiff outer shell is essential if a helmet is to protect in impact against
load concentrating surfaces. Helmet shells must be also tough enough to resist
penetration by edged and pointed hazards
such as road side barrier structures, signage, foot pegs and much more. Shell
penetration testing and edge impact testing assure that the helmet shell will
do its part.