beezaur

I reviewed numerous test standards, especially the one used in the US. I also studied up on the actual materials in my helmet. There is a lot of information I looked through on tests that actually were done too, including damage to helmets that actually were tested.

Measurements (rough ones) on my helmet were of deflection both on the inside and the outside. The full thickness of the foam was compressed somewhat. There are cracks too.

The damage to my helmet is "consistent with" actual damage from tested helmets. That is to say, it is roughly the same extent and type of damage. As it was, there was no evidence of major sliding in my crash.

I have experience doing accelerometer measurements under shock loads, destructive material tests, and things like that. I've also spent years on the analysis side, including using finite element analysis (writing my own code too).

Reading about the helmet tests, looking at the results of my crash, and my own experience with similar testing tied it all together. Anyone with a similar background probably would have the same experience.

My helmet was sitting in the corner and I was almost afraid to look at it, to tell you the truth. In the course of figuring out what to buy I worked up the courage to look. There was definitely an "oh gawd" moment the first time I took a careful look at the damage.

But anyway . . .

In the general case, helmets don't start major deformation until about 200 gs or so. By the time a human head reaches that kind of deceleration, you are looking at a concussion. The brain itself is not exposed to those high gs - it keeps moving and decelerates slower within your skull. So the actual forces and accelerations are tough to nail down and would require a fairly sophisticated analysis.

One unfortunate fact about helmets, which I think is a major source of confusion, is that you basically have to choose whether you want to have protection against minor injuries, or major injuries. The US standard is major injuries. So helmets in the US cannot protect against minor ones very well.

When claims are made that helmets don't protect you, that is what they're talking about - minor injuries. What they don't mention is that the reason is that they do protect against major injuries.

Verified by my doctors, that is exactly how my helmet worked.

I had a good concussion, but avoided permanent brain damage. It's not like I'm happy about being injured, but it prevented something far worse. The physical damage to my helmet looks almost exactly like a tested helmet. So I am pretty satisfied that my helmet's deformation was pretty much the same as those destroyed in testing.

That said, there are issues that could have caused my helmet to behave differently. There could have been a major sliding component to my landing, which is not tested for. The impact could have been in one of the more shaped regions of my helmet, which might have changed things. In tests, they have to duct tape the helmets down really well to even get them to stay on the apparatus.

When I learned about risks associated with non-round shapes and large vent holes, that was the end of that for me. I found out that MTB/skate style helmets were much safer. Here is a photo of the winter helmet I have on the way:



It's also certified as a ski helmet (not that I care) which means it has some features that make it probably good for winter riding: pluggable vents, detachable ear covers, and generally warmer construction. There were some runners-up that were pretty inexpensive, in the $40-$50 range.

I'm not saying helmets with aerodynamic shaping and massive vents are bad, but there are safer helmets out there.