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The Helmet Update

Volume 40 - #1 - February 1, 2022

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Snell publishes rotational energy research

Summary: Snell has tested helmets with and without a rotational energy management system and found that there were differences with some testing methods but not with others that possibly simulate more realistic coupling of head and helmet.

The Snell Memorial Foundation has published a paper on its website with new findings on rotational testing. The paper is by Stephen Johnson, Executive Director, and Dennis Anischenko, Chief Technology Officer. It has not been peer-reviewed.

Snell did not specifically identify the rotational mitigation technology they tested, so it could be MIPS, WaveCel, SPIN pads, 6D Omni-Directional Suspension, Leatt 360 Turbine, Kali Composite Fusion Squared, Fluid Inside, Koroyd or other. They tested with a method similar to ASTM/FIM/MIPS/EN/Folksam testing, dropping a helmeted headform on an angled anvil covered with sandpaper much rougher than a road surface.

Snell wanted to test with various levels of coupling of helmet and headform. They initially tried a standard magnesium headform with a covering of silicone to more closely replicate the coefficient of friction of a human head. They found some improvement in angular acceleration in the frontal one of three locations on a bicycle helmet, but no improvement in angular velocity. For a motorcycle helmet they did find improvement in both measures. To test the coupling theory further they tested motorcycle helmets with a wig over the silicone layer. Those tests showed no improvement at all from the rotational technology add-on in any of the impacts. "The wig broke the coupling between the head form and the helmet so completely that the anti-rotational feature had no effect on rotational acceleration or angular velocity in this series."

Snell concludes that "We have demonstrated that at least one anti-rotational innovation can change the response of helmets tested in oblique impact. However, we have also demonstrated that different test conditions which might reasonably simulate performance in the field nullify the effect."

Snell's bottom line: "Finally, although the testing has demonstrated that this anti-rotational feature does reduce peak angular velocity and peak angular acceleration for some tests conducted to FIM protocols, whether these findings bear on the protective performance of these features in real world crashes appears uncertain. Fortunately, helmets incorporating these features are already in use. Epidemiological studies of crash outcomes may one day tell us what we need to know. "

There is lots more detail in the linked pdf file, and no fee for downloading it.