Originally posted by 924Guy:
...To put numbers to it, the threshold for basal skull fracture or other injury is 4000N (tensile force on the neck). The HANS reduces this to 2000N in their benchmark frontal impact test (sorry, don't remember for sure the numbers, but I think that was 40G, 35mph). By contrast, the ISAAC, Hutchens, etc all apparently end up at around 3000N - enough to save you, but less effective. But the HANS does have its limitations - in lateral. It only contributes in a 45 degree angle; beyond this angle of impact, it will not help control head motion. This was why I selected to go with the ISAAC; again, while not as effective in straight-line, it appears to (based on analysis of design and my personal experiences) provide support and motion control in all up to 90 degree impacts. More on my personal testing of the ISAAC later....
Vaughan,

Thanks for passing on the information. It is consistent with everything we know with one exception, the head loads in frontal impacts for the devices mentioned.

Both the Isaac system and the HANS device come in at about 1,000N:

http://www.isaacdirect.com/html/chart.html

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Gregg Baker, P.E.
Isaac, LLC
http://www.isaacdirect.com