> In your accident it's clear that neither you, the bike, or your helmet had much traction.
The impact that you can't see in the video that damaged the helmet was in the collision with the side of the truck after it hit my left arm, rotating my handlebars to the right. This caused the counter-steer that slammed me into the side of the truck. The truck was moving faster than I was, so that was the source of the rotational acceleration.
Helmets are usually worn pretty loosely, after all you don't want your jaw forced close by an overly tight helmet strap. As such you can typically move a helmet around on the top of your head, especially with say the force of a truck hitting you.
So both WaveCel and non-WaveCel helmets help absorb impacts and reduce the peak acceleration of your brain. Imparting dangerous levels of rotational acceleration seems wildly improbable. Maybe if your helmet strap got caught on the trucks lugnuts? Even then the MIPS or WaveCel would absorb maybe 30 degrees of rotation?
I'm actually curious if you still have a working WaveCel. If you try to rotate your helmet for a normal helmet how much extra rotation do you get? Is it damped as you rotate, or rotating freely within the range available?
For the Wavecel to make a difference you'd need a very high traction to allow high torque which is required to reach a high peak rotational acceleration AND a very low total rotation. Even then I'd expect a normal helmet to rotate just as far.
Antanomically I just can't see it working. I've had my chin forced into my chest, landed on the wide of my head (forcing head onto the opposite shoulder), crushed the back my helmet. But generally there's not much friction between my hair and the helmet, or the helmet and the ground. So to transfer much energy requires an impact not a shear force or torque of any kind.
Can you propose an accident that would impact a sudden large torque to a normal helmet, but a low total rotation (compatible with keeping ones head attached)? Or really anything that allows a slippery layer inside the helmet to make a meaningful difference?
If WaveCel was actually better at absorbing impacts (which they show in their animation) than styrofoam I wouldn't expect them to make their helmet out of mostly styrofoam. If the WaveCel material is worse than the helmet is actually less good at absorbing impacts than a helmet of similar thickness and weight.
Seems safest to just buy the best styrofoam helmet you can buy and don't add cost, weight, and complexity to try to offset this theorized danger of peak rotational acceleration causing concussions that is somehow mitigated by Mips or WaveCel and not by a normal helmet worn normally.
It all happens during a split second of the impact, thr helmet won't be slipping while it is being pressed against your skull by the impact, hence the slip mechanisms. The strap is to make sure your helmet is still in the right place at the moment of impact and subsequent impacts not to stop it from moving during the impact.
Whether or not it's a marketing gimmick, it's the only good indicator we have as the research is inconclusive and I certainly don't have any better idea than the people making the helmets.
That said, what I typically look to for advice on what is a safe helmet is downhill mountain biking competition standards. If they think it will make the sport safer, and their insurance lower, then it's a good indicator that it is probably a good standard to have for my own head.
The impact that you can't see in the video that damaged the helmet was in the collision with the side of the truck after it hit my left arm, rotating my handlebars to the right. This caused the counter-steer that slammed me into the side of the truck. The truck was moving faster than I was, so that was the source of the rotational acceleration.