How does a Helmet Protect Your Head? HEAD PROTECTION CAN BE CALLED MANAGING IMPACT ENERGY. EXCEPT MANAGING THAT ENERGY IS NOT JUST ABSORBING IT.
GLANCING OFF
GLANCING OFF WORKS TOGETHER WITH ENERGY ABSORPTION INVISIBLE TO YOUR EYES .
In the event of an impact, energy is created, and the role of a helmet is to ‘appropriately manage the impact energy’ to protect the rider’s head. That energy management is generally achieved by ‘absorption’ of the impact energy around the head, thus protecting it. The outer shell deforms and the cells of the inner EPS liner crush, and that destruction manages impact energy by converting it into work. However, the truth is even the best helmet has limits to how much energy it can manage. On the other hand, the helmet isn’t only absorbing energy, but rather in a large crash when the rider’s head is repeatedly protected by the helmet, we understand that it’s working to manage impact energy in another important way.
That is ‘glancing off’. Many people probably don’t even realize this, but at the moment a helmet is impacted, if struck off center it can slide on the crash surface, minimizing the impact energy that might otherwise be transferred to the rider’s head. Therefore, if not directed toward the center of the helmet, the head inside can be protected, even with high energy levels and the liner’s limited energy absorption ability. Even in extreme crashes we’ve witnessed ‘glancing off’ and ‘energy absorption’ as two halves of energy management that work together to increase the chances of head protection. This holds true for any kind of helmet.
When we talk about ‘Impact absorption ability’ there will be a limit regardless of any manufacturing technique employed, because of the limited amount of space between the shell and rider’s head necessary to manage impact energy (see below “The Limit of Absorption Ability”). And on a motorcycle, we have to prepare for impacts that far exceed our imagination. So it follows that glancing off is critical for supporting that. Arai’s helmet exhibits results due to its strong shell combined with its round smooth surface and achieves the important goal of not letting energy into the helmet. However, helmet standards place their emphasis on impact absorption and do not show anything about glancing off. Glancing off is the synergy of various elements working together, and there is no set way to impact a helmet to test for it. There is a
test for shell strength to resist penetration, though because it’s difficult to put numbers to the shell form and such for glancing off, there remains no definition. Any helmet makes use of glancing off, but due to the difficulty in numerically capturing each helmet’s difference in ability, there are many cases where safety standards simply don’t define glancing off. In addition to passing standards, Arai makes continual efforts to improve our helmets’ glancing off ability and pursue gains in head protection.
As for the force involved, if you convert the force from the helmet drop test of the strictest helmet standard in the world, it amounts to merely 27.9km/h (or 7.75 m/s).
Impact Energy
All helmets protect the rider’s head through both glancing off and energy absorption.
THE LIMIT OF ABSORPTION ABILITY
Here is the moment of impact. The rider tenses up, and the helmet contacts the ground. You can imagine what the helmet has to do next.
Buffer Zone II Size of the helmet
The amount of energy in a crash can be expressed as distance and force, where distance is the physical space between the helmet shell surface and the rider’s head, or in other words the helmet size. If you make the helmet user-friendly, there will be a limit to its size. Regardless of construction or material employed, there’s still a limit to the space available in a helmet.
MOVING FORWARD
Illustration
AIMING TO BE THE BEST IN THE WORLD
When it comes to proficiency in head protection, Arai has the goal of making a helmet superior to all others and continues to make our helmets this way today. We have seen this confirmed in many of our rider crashes over several decades, and we pursue gains in protection even if just a little. Because we come from this background, we’ve come to notice the importance of the smoothness of the
helmet as a component above all others and continue to employ it in our approach. Head protection is the foundation of our belief in being the best in the world and we pursue the value of both ‘glancing off‘ and ‘impact absorption’ equally. This is the difference of Arai.
01 HELMET SCARS FROM IMPACTS Impact absorption testing is representative in
SCAN HERE to watch crash video
helmet standards testing. It numerically measures the impact when a helmet collides with an obstacle
ENERGY ABSORPTION
GLANCING OFF
straight on. Diagonal scars are left on the
‘Energy Absorption’ and ‘glancing off’ are two wheels that can do the job of preserving balance that can work together without bias or offset.
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Right: Impact scars from drop test (hemisphere anvil)
helmet where it received a perpendicular impact. On the other hand, impacts can be received from different angles and the scars flow horizontally from the impact point. *See riding impact case examples.
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