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In August of 2004 some friends and I took a ride from San Francisco up to Sacramento to visit Snell Labs where they test helmets.

Snell Laboratories test helmets for motorcyclists, car racers, skiers, and bicyclists. Compliance with the program is voluntary. Manufacturers agree that once the initial tests are complete and certification is issued, Snell Labs will randomly buy helmets at retail, test them, and bill the manufacturer. If any helmet fails the test, that model will lose its Snell certification.

The tests are all done the same way on test jigs built for those specific tests. Thus they are objective and repeatable.

The first step in the testing process is to measure the helmet's face opening to show that it does not interfere with peripheral vision. A headform is inserted in the helmet and rulers formed to the minimum view angles are held to its "eyes". As long as the edges of the opening don't interfere with the angle-forms, it passes.

Then the helmet is marked according to the locations of the official testing area. Manufacturers and Snell Labs agree that it is difficult or impossible to provide the necessary impact protection at the very edge of the helmet, so the minimum area of protection is marked. Anything within that area is fair game. The engineers at Snell Labs are experienced in what will typically fail, so they aim for those parts.

First they test the helmet's chin bar. Basically a weight is dropped from a specific height and the deflection of the chinbar is measured. It is not permitted to bend inwards more than 60 mm (2 3/8"). This particular helmet, in for initial certification, failed the test. Snell will notify the manufacturers of their findings and let them submit another one when they've redesigned it.

The next set of physical tests are the chin-strap tests. They make sure that the helmet will not roll off and that the chin strap has the correct strength. For the pull-off tests the helmet is attached to a headform and a calibrated weight, attached to a strap, is dropped in a way that tries to pull the helmet off the headform. The helmet is tested twice, for a forward and a backward pull-off. If the helmet comes off the headform, it fails the test.

A guide is hung from the chin strap to make sure that it does not tear off its mounts or stretch too much or too little.


Then the helmet is placed on another headform, this one weighing 5.5 kg, and dropped onto two different targets from a specified height. The headform contains an accelerometer which measures the impact. The Snell standard is that the maximum deceleration from impact must be less than 300G. The headform with the attached helmet is attached to a frame which is lifted up into a hole in the ceiling. The guide wires ensure that the helmet drops in a predictable way. The speed at impact is measured by an optical sensor, the red thing at the right side of the second picture here.

The helmet made quite a loud noise when it hit the anvil—we all cringed. This particular helmet got dropped about four or five times onto the same spot, just to see what would happen. Surprisingly, even though it was visibly damaged after the third drop, it still met the test requirement. (Nevertheless, it had reduced protection after the first drop.) The tester told us that when a helmet fails the test, you can feel it through the floor of the building.

A motorcycle helmet works by crushing the expanded polystyrene (EPS, or Styrofoam) layer, absorbing and slowing down the impact. If a helmet doesn't slow down the impact, the energy gets transmitted to the skull and brain inside and to whatever it hits.

Unfortunately at this point I ran out of film. The second roll is still in my camera. When I get those developed, I will add the photos here. Do come back and check ... the second roll justifies me using my old Canon. There are pictures of the drop-test instrumentation, the dimples in the paint on this helmet, and the visor-test rig.

After the tour of the laboratory, we asked some questions.

If you drop a helmet from a few feet, say the seat of a motorcycle, is it okay?
Basically, yes. It takes a lot to damage a helmet. If the helmet fell onto a hard surface and your head was in it, you should replace it.
Do the new flip-face helmets pass the Snell tests?
None have been submitted, so they don't know. But they do know that when a manufacturer submits one model helmet for testing and it passes but they do not submit a different model, then that other model generally fails the Snell tests. So the conclusion was that the flip-face helmets don't offer the same level of protection as full-face helmets.
 
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