03-14-2002, 07:19 PM
An interesting, but often unappreciated fact about helmets and head protection:<br>
<br>
It is very hard to penetrate even relatively thin, mild steel. We determined this by using a crow-billed axe on an 18 gauge mild steel helmet, mounted on a short post. The heaviest blow a 250 pound bruiser could deliver barely penetrated, but the force of the blow would have crushed vertebrae.<br>
<br>
The helmet did deform, and had it been as tight fitting as most Roman helmets appear to have been/be, the wearer would have suffered a severe concussion and fractured skull. However, remember the crushed vertebrae! I will return to the deformation item in a moment.<br>
<br>
So it is the neck, not the skull, and the brain that are most vulnerable to a head blow. From the back, it takes less than 10 psi to break a human neck. It takes more from the front because of the structure of the neck muscles and ligaments. Nevertheless, anyone with a severe neck strain is sufficiently wounded to be ineffective.<br>
<br>
There are two possible ways to protect the neck and brain from the force of the blow, one more effective than the other.<br>
<br>
The most effective is MASS. The heavier the helmet, the more force is required to move it, and hence the head, which contains the brain (vulnerable to sudden acceleration which causes concussion) and the skinny neck that attaches it to the body. We tried this, too, on a live person wearing a 15 pound helmet and camail. Hitting a horizontal blow with a 5 pound mild steel bar was merely annoying to the target. We stopped when the bar bent. The helmet was not dented. Now, with accelerometers much cheaper, we would not have used a human guinea pig.<br>
<br>
But what if the current technology does not permit the manufacture of a more massive helmet? Or what if the added weight is deemed to much for a marching soldier to carry? Or it is too expensive?<br>
<br>
Then restrain the sudden backwards movement of the head. The beavertail on the back of the Roman helmets in discussion was not there to keep the sun, or sword slashes, off. It would, very effectively, keep the head from being snapped back too far.<br>
<br>
Roman armor was not modern mild steel, although it may have picked up enough carbon while being worked to be close in its properties. Nevertheless, it may have been softer and more easily deformed. (I saw the metallurgy on one helmet, long ago. Anybody got a reference or a more recent study?) In a closefitting helmet, that is disastrous. I believe that is the reason for the increased reinforcement seen as ridges, raised designs, and additional plates on later helmets.<br>
<br>
<p>Salve,<br>
Triarius<br>
One of the pack, maybe. One of the herd, <i>NEVER!</I></p><i></i>
<br>
It is very hard to penetrate even relatively thin, mild steel. We determined this by using a crow-billed axe on an 18 gauge mild steel helmet, mounted on a short post. The heaviest blow a 250 pound bruiser could deliver barely penetrated, but the force of the blow would have crushed vertebrae.<br>
<br>
The helmet did deform, and had it been as tight fitting as most Roman helmets appear to have been/be, the wearer would have suffered a severe concussion and fractured skull. However, remember the crushed vertebrae! I will return to the deformation item in a moment.<br>
<br>
So it is the neck, not the skull, and the brain that are most vulnerable to a head blow. From the back, it takes less than 10 psi to break a human neck. It takes more from the front because of the structure of the neck muscles and ligaments. Nevertheless, anyone with a severe neck strain is sufficiently wounded to be ineffective.<br>
<br>
There are two possible ways to protect the neck and brain from the force of the blow, one more effective than the other.<br>
<br>
The most effective is MASS. The heavier the helmet, the more force is required to move it, and hence the head, which contains the brain (vulnerable to sudden acceleration which causes concussion) and the skinny neck that attaches it to the body. We tried this, too, on a live person wearing a 15 pound helmet and camail. Hitting a horizontal blow with a 5 pound mild steel bar was merely annoying to the target. We stopped when the bar bent. The helmet was not dented. Now, with accelerometers much cheaper, we would not have used a human guinea pig.<br>
<br>
But what if the current technology does not permit the manufacture of a more massive helmet? Or what if the added weight is deemed to much for a marching soldier to carry? Or it is too expensive?<br>
<br>
Then restrain the sudden backwards movement of the head. The beavertail on the back of the Roman helmets in discussion was not there to keep the sun, or sword slashes, off. It would, very effectively, keep the head from being snapped back too far.<br>
<br>
Roman armor was not modern mild steel, although it may have picked up enough carbon while being worked to be close in its properties. Nevertheless, it may have been softer and more easily deformed. (I saw the metallurgy on one helmet, long ago. Anybody got a reference or a more recent study?) In a closefitting helmet, that is disastrous. I believe that is the reason for the increased reinforcement seen as ridges, raised designs, and additional plates on later helmets.<br>
<br>
<p>Salve,<br>
Triarius<br>
One of the pack, maybe. One of the herd, <i>NEVER!</I></p><i></i>
