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Re: Helmets -- when do you change? Demonstration

In a message dated 12/05/2003 4:52:05 PM Eastern Standard Time, 
marc@xxxxxxxxx writes:

<< Just curious as to how long people keep their helmets. >>

Very good discussion here. 

I had the opportunity to sit in on a show and tell held by one of the 
University of Tennessee at Knoxville professors recently. He does his thing in the 
Department of Science and Engineering Research and concentrates his efforts on 
impact testing of helmets of all types, actual body parts (more on that in a 
minute), and more. This guy is a member of the local HOG chapter as are several 
of our local MSF instructor types. I'm not a member of HOG, but was invited 
along to this official HOG chapter event as were all of the other non-HOG 
chapter MSF folks.

Let me tell you...it was way cool. He started off with a short talk about the 
kinds of forces that the head is designed to absorb. Pretty darn interesting 
and way too complex to even start to absorb. Really complex stuff. He included 
some pictures of accident scenes that were quite graphic, but they made a 
point. After that, we went down to the little room where they had all of their 
testing equipment just as you'd expect the folks at Snell to have. Lots of 
equipment with high tech measuring for determining how much force a head or other 
body part is exposed to. Things to measure drops on different surfaces, things 
to measure impact from the side, an air powered "canon" to propel things from 
the side, and so on. They've developed a lot of new concepts in helmets right 
here in my home town where I've lived for 50 years, and I didn't know they did 
this stuff until last month. Most of the new football helmets in use at the 
major college level incorporate several of the University's patents (or 
his...he didn't talk about who gets credit for stuff in the world of academia).

He had a stack of bicycle helmets that had been submitted for testing and he 
demonstrated a bunch of the tests they do on them. 
To test extremes, they freeze helmets, they test them out of an oven for 
heat, they soak them in water and test them, and on and on. As you might expect, 
some materials deal with temperatures at the extremes better than others. Good 
old Expanded Polystyrene is still among the best. Our host showed us a helmet 
he uses that is commercially available that uses another type of lining. I'm 
sorry I don't remember what it is, but it was a slightly softer material than 
EPS. He said in testing it did quite well, maybe better than EPS, in the normal 
operating temperature range, but was a little less effective at 0 degrees F 
or 115 degrees F. (Pick when, where, and how you're going to have your accident 
and get the best helmet you can for those conditions.)

As far as real body parts go, the University of Tennessee is somewhat unique. 
UT is home of one of the world's leading forensic science facilities. A 
fellow named Dr. Bass started this back around the 1950s and now it is one of the 
few places in the world that has access to real cadavers where they do studies 
to determine how quickly body parts deteriorate in different conditions, etc., 
and that's just scratching the surface. To take advantage of what bodies they 
have, I understand a cadaver may go from the Body Farm to the Science and 
Engineering Department where they may break parts of the body to test something, 
then go to the medical school/University hospital where young surgeons may get 
practice putting a body back together, and then return to the Body Farm for 
whatever tests they may have going. In some cases, they do some of their 
testing on un-embalmed bodies, as the embalming process changes the way the brain 
and other organs react to impact. That means they have to take some 
extraordinary precautions when using those bodies as there are all sorts of nasty little 
things that you can get into.

Bottom line was that this fellow, who tests helmets all the time, says he 
replaces his helmet no less frequently than 5 years (that means no longer and 
probably a good bit shorter). That's also the period that Snell establishes their 
new criteria (DOT has NOT changed their criteria since established in the mid 
1960s...don't you find that comforting?) As we probably all know, in that 
time period the technology has probably improved enough that you're being left 
out on important advancements by continuing to wear that old helmet you dragged 
out of a closet or bought used from someone because it was a bargain.
Our host had to admit that while he would prefer the State not get into 
legislating helmets, he also admitted he would wear a helmet. He chooses to wear a 
high quality half helmet with that non-EPS lining I previously mentioned. He 
put a beanie helmet he bought just for this demo through its paces, and no 
surprise here, at virtually any speed on any surface on any shape, a head-form 
took enough stress that you'd be dead with virtually any impact at all. Maybe 
better than nothing, but the beanie wasn't nearly as effective as just a block of 
styrofoam that we yanked out of the inside of an old helmet. The foam was 
quite energy absorbing, but of course, wouldn't take any kind of scuffing.

I found it fascinating.

Geoffrey Greene
Knoxville, Tennessee USA


End of oilheads-digest V1 #22