Just a general culture remark. I'm not trying to propose anything. Do what you please about it, it's just a technical note without any political or moral implications.
I'm for freedom of choice, and against helmet laws, even if I wear one.


How a helmet works?
The most evident function is to avoid you break your skull. Well, that's obviously part of it, but not all.
Older helmets were made of thick fiberglass, had straps inside that separated the shell from the head, allowing it to protect from impact and in the meantime lessen the transfer of energy.
Another obvious function is to provide protection from friction. Again, it's not all there is.
A less obvious, but very important function of a helmet is to reduce deceleration. Impact is not the main cause of lethal head injury, or the only one, anyway, or the most important. The main cause is the strong deceleration it produces. When the head bangs on something, it passes from a certain speed to a stop in a fraction of a second. The skull is a pretty fine job of natural engineering, and may actually survive the impact without breaking, or with a minor fracture that wouldnt endanger the "owner". Unfortunately, the brain has a mass, and will try to continue on its path due to what in physical terms is called "inertia". Usually, deceleration is measured in "g", that is, how many times the acceleration of gravity the measured acceleration/deceleration is. This provides an easier to understand measure that plain m/s^2 (the standard measure of acceleration).
1 g = 9,81 m/s^2.
The human brain can survive only a certain amount of deceleration without being slammed against the inside of the skull with such force that it's reduced to a pulp. Lesser forces produce mild concussion, stronger force will kill instantly, or reduce the person to a lettuce for the time coming.
So, the job of a helmet is to abosrb energy and make so that the deceleration the head undergoes is less than what will destroy the brain.
To do so, helmets have actually been made WEAKER. Why? Because while destroying itself the helmet will absorb and consume energy that would otherwise be translated into strong deceleration. A helmet with a very thick layer of fiberglass, like the old motorcycle helmets or, say, a kevlar military "fritz" helmet will do a great job of protecting the head from impact and even penetrating objects, but in case of accident will be unable to absorb enough energy, being too sturdy, and will transfer it to the head.
A motorcycle or automotive helmet has an external shell of polycarbonate, or carbon fiber, or other similar material, whose job is to protect from impact and minor penetrating objects, and that will guarantee the structural integrity of the helmet intself so that the liner can do its job: abrosbing your head energy from the inside of the helmet. Then, there is an internal liner made of styrene foam with a graded density. The soft padding you feel inside is not for protection, but for comfort only. It's too soft to absorb any significative amount of energy. When the head hits something, the liner will act as a "brake". It will avoid the head travels on its path inside the helmet and then slams abruptly against the inside or is abruptly stopped by straps. Instead it will progressively deform greatly reducing the stress to the brain and cervical vertebrae (helmets also reduce dramatically the chance of neck injury, contrary to popular belief).
It's the combined action of the shell, absorbing energy "from the outside" and the liner, absorbing energy "from the inside" that greatly reduces the chance of lethal damage.
This is also why DOT certification is important: it will certify that the helmet is manufactured so to absorb energy in a gradual way. This obviously doesn't mean a non-dot helmet can't do the same job, it just certifies that the

 

- oh no ....

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The is a layer of liquid in between the skull and the brain....I forget what its called, but one of its jobs is to absorb the shock when your hit in the head. If that liquid is compromised in any way even a small impact could do real damage.
I know that the people who sniff glue have problems with this liquid layer. When you sniff glue some part of the active ingredient passes through your lungs and mucus membranes into your blood....then this chemical for some reason congregates in this liquid layer, and after a period of time will start turning it into a thicker and thicker liquid....until it is almost hard...not unlike the glue they are sniffing.
So.....I dont recommend any huffers out there who ride to fall and hit their head.

 

Yup, wait till AFTER you ride to sniff glue.

 

Pretty nice info.
When I hit a medean on my sportster, trying to be speedy gonzalez, I rolled over on my head and skidded along the gravel in the medean on my noggin. I was just thinking " I wonder how much of my scalp will be gone when I stop" but it only cut about an inch and ahalf cut, pretty deep the hospital said, and only took 4 staples. Not bad considering my hefty a$$ riding on it for that skid.
I will also add, I went into the oncoming traffic lane, but fortunately the light was red and everyone was stopped there, watching my put on my show for them, for free[>:] I was lucky. My uncle died, not cause of the wreck on his bike, but cause the car that hit him at 60+ mph. That seems to be the issue that I am worried about.
BTW I didn't notice it right away, but my memory started short circuiting after that accident. I would get easily confused if too much input came at one time. I still seem to feel a little less able to deal with multi-tasking like I used to, but sometimes it's no problem at all.
I still don't wear a helmet, maybe I'm just plain stupid, or maybe I'm testing newtons law.

 

You left out another very important statistic! The neck can only sustain on averageup to an 11 mph impact.Beyond that spinal column damage occurs.Then factor in the heat that builds up,plus the wind trying to tear that lump of fibergass off your neck.Have always felt safer not wearing a brain bucket and will continue doing so.

 

I'm not qualified as a medic, so I just didn't delve too much in the physiological aspects. Surely a helmet can't change the laws of physics.
A human body can take only so much punisment before sustaining fatal damage. A helmet will lower the forces a skull and spine will suffer in case of accident, but can't take them away. Go beyond that point, and nothing can save your ***.

What's been ascertained, through scientific tests of many kinds, computer modeling, crash test dummies and many other marvels of modern technology is that a helmet offers greater protection than no helmet. There's no guesswork in this, as science has answered in an undebatable way to the question if a person is more protected by a helmet or not.

Where technology and the scietific method fail, and can't give an answer is on the subjective level: there are many considerations about safety that are not so immediately evident. The amount of "uneasyness" and distraction that a piece of gear can cause to the rider is not easily determined, as it may vary greatly from person to person, and since the primary goal is anyway NOT crashing, they may constitute a safety hazard rather than a life-saver.

I won't give advice in one sense or the other. I greatly believe in freedom of choice. I've nothing to gain giving it, I'm not qualified to give it, and it's not been requested, so it may only result annoying. I only posted some technical facts for the sake of knowing.

Somebody who chooses not to wear a helmet because he believes it won't protect him, or will be more dangerous than no helmet at all, may reconsider, or may not. Either way, it's not the purpose of my post to make anybody reconsider. I just wanted to post something which may be interesting, really.

 

We have a joke around here (trust me it's a joke)

Wearing a helmet above 50 mph just makes it easier to find your head.

 

Just goes along the line of people saying they like old cars that had a lot of metal to protect you.
New cars crumple like a cardboard box when hit, but that is energy being disipated.
I see people out of there cars and walking around after 35-50 m.p.h. head on accidents with new cars, with old ones people would be dead right there after a 20 m.p.h. head on.

 

Good stats, thanks. I have in the past put the helmet on when I know I'm going to ride "on the edge", twisties, high speeds or both. I don't wear it when I'm just cruising country roads. I wear it when I ride to work cause my OL made me promise. Lucky I had it on when I hit a left turner recently. It did hit down and had a pretty good gouge in the chin piece. The insurance guy gave me a check for it, grabbed it and ran. Don't know what that was all about, some liability of sorts?