Impact range

[Jason]

What is the impact range between a trye barriers and a concrete wall?

[Ciro Pabón]

I do not know if this is helpful, which I took from here, because I do not understand well what you mean by "impact range":

"The HANS device (which NASCAR made compusory six months after Earnhardt's death) saved Ritchie Hearn's life. "I went head-on into the wall at 210 miles an hour (139 G's). I didn't have a headache, I didn't black out - nothing. I didn't have a mark on me except for my foot."

[Sources: "Ultimate Racing Crashes" (Discovery Channel)]

This quote makes easier for you to imagine that the forces that the pilot suffer depend on retaining gear, chassis and speed as much as the barrier itself. It also gives you an estimate of the G forces invoved. Besides, a tire barrier is designed to disperse and decelerate, not to contain, as opposed to a concrete barrier.

A rule of thumb:

G force average = Speed differential squared/(2 x distance for stop)

For example, if you take the data from Mr Hearn's crash, that is 210 miles/hr, which is 94 meters/second, this means that the "squashing distance" was 6.5 meters.

By squashing distance I mean the crushed part of the car plus the movement of the barrier plus any movement allowed and restrained afterwards by the seat belts and the HANS (for your basilar skull fractures, which is your probable cause of death in a barrier crash at 200 mph). It is the total distance over which you were deccelerated. This distance is found in the previous equation as:

139 G = 139 * 9.8 m/s2 = (94 m/s2)^2 /(2 * 6.5 m) = V^2/2S

There are other factors: for example, if you use an airbag you distribute this force over a larger area of your body. Besides, the main force is applied on the last part of the decceleration (the last foot or so), so it is very important what part of your car stops you in this last foot: it is not the same to hit a solid steel Ford Fairlane's 1955 dashboard that a well padded Volvo dashboard in this last foot. The average G force from this simple equation is only a lower limit of what really hits you.

I worked for a while at Turner-Fairbank. They have the FOIL lab on barriers, but I think they have not tested a tire barrier, only standard road barriers. You can ask to martin.hargrave@fhwa.dot.gov and he may answer you.

BTW, this lab always was a source of fascination to me as I saw them destroy over 100 cars in one year. They piled them in a huge parking lot I passed by every day. I never speeded with the same emotion afterwards. Who knows, maybe they will try one for you. Only in America...

[ackzsel]

Those 139 G's are measured from the car, right? Is there any way to figure out how much G's the driver had to cope with? Since there is an amount of strech in the savety belts, the driver travelled over a larger distance in the same amount of time which leads to less G's according to the above equation.

[Ciro Pabón]

Those 139 G's are measured from the car, right? Is there any way to figure out how much G's the driver had to cope with?

Actually, this values are deduced from measurements made using acelerometers on dummies. So this should be the value for the pilot.

But you are right: if the value is measured on acelerometers fixed to the car, your seat belt would diminish this amount, "spreading" the deceleration over a greater distance (and, of course, time) and diminishing the peak value.

The distance you have to use in the equation is the distance over which you are decelerated. The equation assumes that the deceleration is constant, like the one you have with a good restraint. If you hit something in your movement, then the equation does not apply (or, better, apply to the hitting). As the old saying goes: "it is not the fall what kills you, it is the floor hitting you".

[jaslfc]

few years ago button crashed outside the tunnel in monaco. he gave a figure on how many g's he experienced.. does anyone remember?

[Ciro Pabón]

Finally! I should have known it was at Gp.com, Jason:

http://www.grandprix.com/ft/ftpw016.html.

There you can see that G forces are low for tire barriers, because they deform extremely well, up to 30 G, wich is good.

So a first answer: very roughly speaking, a concrete barrier can deliver up to 4 times the forces to your body that a tire barrier, if 139 G's is typical for a full F-1 speed frontal hit on a concrete barrier, where the deceleration distance is what your chassis deformation provides. The tire barrier gives you therefore, three times the deformation or stopping distance that your chassis can give you.

This is the description of Button's accident in Monaco 2003 in Daily Times (at the bottom of the page). Sorry, no mention of G forces.

You can see by the photo

and the description that he hit the barrier sideways, so it is hard to guess what was the change in speed to deduce a force. It was hard enough to destroy both rear axles.

Lateral collisions are dangerous because they have the same effect of head-on collisions: they duplicate the speeds involved because the change in speed (actually, momentum) is doubled. Every time you bounce laterally, you change your lateral speed vector by 180 degrees and the human body is better protected against the more common frontal hits.

What this means is that you should use, in the simple equation I gave, the absolute value of the change in vector speed instead of a simple substraction of speeds after and before the crash.

Here is a table with typical effects of G-forces.

Here is a long history on the famous Holloman track experiments in the 1950's, when Colonel Stapp took 40 Gs for 1 second.

There is also a curious table (that does not mention its source) that gives you the G-Forces and pressure forces for water collisions.

[Jason]

No fear of F1 after crash, says Button

MONACO (Reuters) -- Jenson Button can remember little about the crash that forced him to miss Sunday's Monaco Grand Prix but the Briton has no fear about stepping back into a Formula One car.

"I've never really had a big accident in F1 but it doesn't scare me at all, which is great," the BAR driver said, standing in the bustle of the shaded pit lane before the race as mechanics worked around him.

"You never know if it will but it didn't scare me at all in this one.

"I'm looking forward to getting back in the car but I also don't want to be silly about it," he added.

"I want to go through all the training regime first and make sure everything's good. I don't want to get back into the car and hurt myself. We have to make sure everything's okay before I do that."

Button was knocked unconscious in a crash on Saturday that was frighteningly reminiscent of one suffered in 1994 by Austrian Karl Wendlinger, who ended up in a coma for days.

The Briton roared out of the tunnel at around 290kph before hitting the barrier, slewing across the track and slamming into the tire wall sideways in free practice.

He was tended to in the car for 10 minutes before being taken to hospital, where he remained overnight.

Little lost

"I remember the car going a bit sideways to start with and then I remember being totally out of control and hitting the inside barriers," he said.

"It didn't feel like it was hard and then I can remember seeing the wall coming towards me. After that I was a little bit lost.

"After I hit the wall I was unconscious, I don't know for how long. I sort of came round and they (the rescue team) had already cut (through the seat) up to my arm, I might have been awake but I can't really remember.

"I was speaking to (FIA medical head) Sid Watkins and he was saying that I was talking but I wasn't making any sense," said Button.

"I said what's different? I mean, that's me all over.

"I didn't have a clue where I was. I was just looking down and my legs were hurting."

Button, third in Thursday's first qualifying, said he was disappointed not to start the seventh round of the championship but he would have other chances.

"It is disappointing but then again if I'm not well for the race I don't want to race because I could be a danger to myself and everyone else," he said.

"I had concussion yesterday and they kept me in overnight because of that.

"I'd love to race here and everything's gone so well here this weekend, apart from the accident.

"It just gets better and better every race, but I'm 23 and this is just one race in my career. There's a lot more better races to come."

Button is due to test with BAR at Monza in Italy next week but he was unsure whether that would be possible, intending to stay in Monaco for a couple of days instead to work out in the gym of the Hermitage hotel.

"I'm not sure if I'll be testing next week. I'll definitely be in Canada (the next race), 100 percent," he said.

If JB is not scared of crashing I would presuade him to crash from 300km/h (nah just a joke)

[Scuderia_Russ]

If JB is not scared of crashing I would presuade him to crash from 300km/h (nah just a joke)

If it's any consolation Jason I think most of your posts are a joke.

[m3_lover]

If JB is not scared of crashing I would presuade him to crash from 300km/h (nah just a joke)

And Alex Wurz holds the record for the most G's ever record in a accident for mclaren.