Pixels
New member
OK, I've been thinking about this a lot lately. I often see one seat recommended over another seat for little FFers because of the low head excursion numbers, or to make sure that it's tethered. But that just doesn't make sense to me.
The purpose of limiting head excursion is to (hopefully) prevent the child's head from striking the interior of the vehicle. It has no direct bearing on neck loading that I can see. The way that it's measured, it does not indicate the total distance that the head traveled in the crash.
In fact, might it not be better if the head traveled farther? Thus increasing ride-down time and decreasing neck loads. In fact, this is what the SafeStop on the Radian does. It allows the head to travel farther, increasing ride down time and decreasing neck loads.
Of course, it's difficult to compare apples to bananas (or Radians to Marathons) with the testing the way that it is currently done. If the Radian was the exact same seat, but the shell was 2 inches thicker behind the child's back, the head would start out 2 inches farther forward, travel the same distance (and presumably have the same neck loading characteristics), and have a higher head excursion number (by 2 inches) just because it started out farther forward.
I believe the HIC number is a more accurate (though indirect) indicator of neck loading. It is derived from the acceleration forces measured in the test dummy's head. Lower acceleration (which means reduced forces) results in lower HIC numbers.
Make sense?
The purpose of limiting head excursion is to (hopefully) prevent the child's head from striking the interior of the vehicle. It has no direct bearing on neck loading that I can see. The way that it's measured, it does not indicate the total distance that the head traveled in the crash.
In fact, might it not be better if the head traveled farther? Thus increasing ride-down time and decreasing neck loads. In fact, this is what the SafeStop on the Radian does. It allows the head to travel farther, increasing ride down time and decreasing neck loads.
Of course, it's difficult to compare apples to bananas (or Radians to Marathons) with the testing the way that it is currently done. If the Radian was the exact same seat, but the shell was 2 inches thicker behind the child's back, the head would start out 2 inches farther forward, travel the same distance (and presumably have the same neck loading characteristics), and have a higher head excursion number (by 2 inches) just because it started out farther forward.
I believe the HIC number is a more accurate (though indirect) indicator of neck loading. It is derived from the acceleration forces measured in the test dummy's head. Lower acceleration (which means reduced forces) results in lower HIC numbers.
Make sense?
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