Matt Nicholson wrote:
Quote:
YOU say its dangerous with a roll bar in a street car. Please show me where someone has died because they had a roll bar in a street car.
10 years. That's how long I've driven a car on the street with a roll bar. I even got rear ended once. I just simply do NOT see the issue. A padded rollbar is no more dangerous to my head than the padded steel roof above my head. Or the plastic coated steel door frame that's *right there* to the left of my temple.
I couldn't disagree more, from a pure engineering standpoint, about roll bar head contact versus, say, the door frame. There is one critical aspect you're missing here: effective contact area. A rollbar, properly padded, still creates a much smaller area of contact with your skull than the b-pillar (or other surfaces which in modern cars are designed with your skull in mind).
Think about the few degrees of angle that your skull will contact the rollbar which gives the vertical dimension of the area of contact. Let's assume that the horizontal dimension is similar to the b-pillar. Now increase the load, severity of the impact, and you can quickly see how there is almost no additional load area created on that radial section of rollbar contact (unless you bend your skull around the bar further), but on the b-pillar, you in fact do get a much larger area of contact as your neck deflects and more of your head/side of face make contact with it. On that roll bar, the contact area remains almost constant from the initial low load contact all the way to the full peak load...what does increase though is the local stress your skull and brain have to endure (and the decel rate your brain has to endure, locally).
This area of contact difference is what makes roll bar contact so dramatically different since strees = force/area. It is the localized stress on the skull and the brain inside that is many, many times greater contacting a bar versus the b-pillar which creates the problem.
Some people can have a lifetime of taking a risk with no bad outcome, but that experience simply means the realization of that risk didn't happen over the time period in question.
I'm reminded of a story a good friend, Ray Kelly (passed away now), who was a founding member of the CBOE told me about an options trader buddy of his. The guy had a "great system" he had used since the founding of the options exchange in the 1970's. He had made money every single month of every year trading stock and index options up until October 1987. On the Friday before the crash, implied volatility had soared to levels beyond anyone's comprehension. His system gave him an entry signal to short volatility (sell short put and call options) beyond anything he'd ever experienced. He jumped all over it and took on a full position, like he always did for so many years with what he knew was going to be a massive reward. He woke up Monday morning with some of those options he sold short at 1/8 (0.125) and 1/4 of a point now trading at 4.00, 5.00, and they only went up in value during the morning, some to over 10.00. He lost more on that Monday morning of the crash than he had made the entire prior 10+ years of making consistent money from his "awesome system". He was instantly in debt for many millions of dollars (oh, and of course he had a huge number of investors who were riding his "unstoppable" wave upward who now were also responsible for many times their net worth in debt).
Sorry for the long aside, but simply being exposed to a risk and not realizing it is truly no reason to assume that means the risk does not exist or is of a much lesser value than sound engineering science would suggest. Tear apart the risk. Examine it from every angle. Use sound methods. Fortunately for things simple like the roll bar example, engineering science is well proven and repeatable. Unfortunately, there is no such science in the area of financial investment/human behavior (no matter who claims there is...like all the investment banks, right? lol).
Cheers,
Chuck
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