George wrote:

It doesn't take an engineer realize the complexity of the situation.

What we expect a bag to do:
1) Deploy at such a rate as to cover a certain distance in less time than
it takes the driver to meet it.
2) Upon reaching the point of maximum deployment, so as not to become the
equivalent of a fixed object,begin deflating at a rate sufficient to
cushion the driver or occupant.

3) remain deployed long enough to absorb secondary impacts. This, I
suspect, is the one that would be a killer on the race course. I'm
envisioning one of those crashes where the car goes end over end several
times shedding parts the whole way. The airbag might help on the _first_
bounce but how about the second, third, fourth, etc? And those are the
ones where the driver needs all the help he can get.

And I remember looking at a wrecked Porsche in the garage at Brumos one
time. It was _flat_ from the firewall (or whatever you call the partition
between the trunk and the passenger compartment in a Porsche--with a front
engine it would have been the firewall) forward. The salesman's comment
was "That was a bad one. Peter (Gregg, who was the owner of the dealership
and a well known racing driver then) sprained his thumb in that one." That
was back in '69--my Dad and I were there looking at a used XK-E that I was
hoping would be my first car and the salesman was trying to steer him to a
new Porsche having despaired of selling him the 250GTO that they had on the
lot--fortunately my Dad was smarter than I was and so I ended up with mongo
Detroit sedan aka roadgoing battleship so I'm still alive. There have been
vast improvements in the safety features of racing cars since.

It's Newtonian physics all the way, so your HS stuff should work, but in
case you require a review http://physics.ucsd.edu/~cdpgrad/speed.html
will
cover the basics. The last equation you'll need is E=mv(squared).

I'm not going to run down the numbers, but the basic bag is designed to
protect a certain mass traveling at a certain velocity over a fixed
distance less than the distance to the wheel, but greater than that
required to
absorb the deceleration as it deflates. You can get a review of the
difficulties at http://www.roadandtravel.com/womensw.../ww_airbag.htm
in case you have missed the ongoing controversy over the bag becoming the
fixed object. The bag is good with minor injuries over a certain range
either side of the design point.

A quick non-engineer assessment says that 150 versus 50 mph makes the
problem about nine times as complex. And they're still trying to solve
the 50.

Buckle up, so I don't have to lift your carcass out of a PIA in my county.
When so many bones are broken, handling a body is like trying to control
jell-o.

NOW I feel better.

"Upscale" wrote in message
. cable.rogers.com...
"George" george@least wrote in message
...
Oh yes, the five-point works only in conjunction with the roll cage and
a
seat that can't compress the driver against the airbag (wheel) on
deceleration. I'd say think about it, but I'm sure you won't, or
can't.

Feel better now? Don't hold back George, it's early in the morning. Let
it ALL out.



--
--John
Reply to jclarke at ae tee tee global dot net
(was jclarke at eye bee em dot net)