09-21-2010, 12:19 PM
Paul B,
It's my turn to apologize for coming on a bit strong, your comment following the accident did not incline me to a kindly attitiude, particularly as those injuries were endured attempting to follow your advice and diagrams of the fourteenth. A trip to the chiropractor's, a couple of days to heal, and a lot of anti-inflammatorys and Tylenol later I am a little more sanguine, and must say some of my comments about crowd theory othismos were unfair.
I do stand by the results of our two experiments of Friday challenging fundamental assertions of your theory, namely collapsing the stance and the superiority of the square to fore push between aspis bearing men. However, as I myself wrote, neither was conclusive as a full 8 man file will be required, and variations on square to fore pushing can be investigated.
Your comments on bones did lead me too do some research. Fortunately my wife is a AA, and our house is a trove of medical textbooks, so I found some very interesting information. Apparently a rib can be fractured by less than 10 PSI. However, the situation is more complicated than that as the sheathing of muscle and flesh makes it more resilient. In particular, there seems to be differential strength around the ribcage between front ad back, with the front where the ribs connect to the sternum being significantly more susceptible to compression and fracture as ths maximizes the leverage on the bone. I also ran across a fascinating summary online on rib injuries that speaks directly to the situation we are considering as well:
http://books.google.ca/books?id=q8VXAAA ... &q&f=false
In it Malgaigne not only describes the nature of rib fractures, but reports on the bodies of 23 people who died due to crowd pressure on the Champs du Mars. Of those 23, 7 demonstrated rib fractures, some fairly catastrophic. All were in the front, all within 1.5-2.5 inches of the cartilidge.
This result would tend to indicate that the most vulnerable place in the rib cage to crowd pressure is the front of the chest. As I understand your latest clarification of pushing, this is exactly the curve where the inside of the rim of the aspis would push on the chest. I modelled the pose several times last night with an aspis, and if, as you propose the aspis is on the left shoulder in a 3/4 stance and then rolls in to make contact on the mid chest and left thigh in a fairly neat curve. Measuring the area of contact it worked out to be about 30 square inches across the shoulder, collarbone, chest, and thigh. This being the case, your proposed shield position maximizes the 1000 pounds force into a pressure along a sharp line at approximately 33 PSI on the weakest part of the ribcage. This seems like a particularly dangerous result to be a cornerstone of a pushing model.
On the flip side, as 1000 pounds force plays on approximately 100 square inches in Arrian's method, which equates to around 10 PSI. So, the ribs might creak when pushing as Arrian proposes, but shouldn't be at any particular risk as the pressure is on the best protected part of the rib cage.
Have fun,
It's my turn to apologize for coming on a bit strong, your comment following the accident did not incline me to a kindly attitiude, particularly as those injuries were endured attempting to follow your advice and diagrams of the fourteenth. A trip to the chiropractor's, a couple of days to heal, and a lot of anti-inflammatorys and Tylenol later I am a little more sanguine, and must say some of my comments about crowd theory othismos were unfair.
I do stand by the results of our two experiments of Friday challenging fundamental assertions of your theory, namely collapsing the stance and the superiority of the square to fore push between aspis bearing men. However, as I myself wrote, neither was conclusive as a full 8 man file will be required, and variations on square to fore pushing can be investigated.
Your comments on bones did lead me too do some research. Fortunately my wife is a AA, and our house is a trove of medical textbooks, so I found some very interesting information. Apparently a rib can be fractured by less than 10 PSI. However, the situation is more complicated than that as the sheathing of muscle and flesh makes it more resilient. In particular, there seems to be differential strength around the ribcage between front ad back, with the front where the ribs connect to the sternum being significantly more susceptible to compression and fracture as ths maximizes the leverage on the bone. I also ran across a fascinating summary online on rib injuries that speaks directly to the situation we are considering as well:
http://books.google.ca/books?id=q8VXAAA ... &q&f=false
In it Malgaigne not only describes the nature of rib fractures, but reports on the bodies of 23 people who died due to crowd pressure on the Champs du Mars. Of those 23, 7 demonstrated rib fractures, some fairly catastrophic. All were in the front, all within 1.5-2.5 inches of the cartilidge.
This result would tend to indicate that the most vulnerable place in the rib cage to crowd pressure is the front of the chest. As I understand your latest clarification of pushing, this is exactly the curve where the inside of the rim of the aspis would push on the chest. I modelled the pose several times last night with an aspis, and if, as you propose the aspis is on the left shoulder in a 3/4 stance and then rolls in to make contact on the mid chest and left thigh in a fairly neat curve. Measuring the area of contact it worked out to be about 30 square inches across the shoulder, collarbone, chest, and thigh. This being the case, your proposed shield position maximizes the 1000 pounds force into a pressure along a sharp line at approximately 33 PSI on the weakest part of the ribcage. This seems like a particularly dangerous result to be a cornerstone of a pushing model.
On the flip side, as 1000 pounds force plays on approximately 100 square inches in Arrian's method, which equates to around 10 PSI. So, the ribs might creak when pushing as Arrian proposes, but shouldn't be at any particular risk as the pressure is on the best protected part of the rib cage.
Have fun,
Cole
