In racing school, one of the first things they teach you is to abandon your knee-jerk instinct to let off the gas (or even worse, brake) when you're entering or fully in a corner, and instead to either ride it out for the best or in some cases to even slightly bump up the speed and handle it with steering techniques.
The reason is actually quite fundamental, but you don't really think of it until you hear someone else say it out loud, and then it's a V8 moment: when you slow down, inertia rebalances *forward* the downforces transmitted from the mass of the frame through the suspension to the wheels. This means that there will suddenly be more downward force on the front tires and less on the rear tires. Now consider a race car operating near the physical limits of cornering ability (which especially happens during qualifying). The stiction between the rear tires and the track is right at the very limit of what will hold. The slang term "stiction" is best described as the holding force that results from the combination of the effective coefficient of friction, the downward force, the contact patch between the tire and the track, and various other properties such as how well the tire's wall profile aids stiction when it deforms under the sideways force of cornering. So any decrease in the downward force on the read tires "unsquashes" the tires from the track, resulting in a decrease in the area of the contact patch (already smaller than you think), and furthermore decreasing the force that is applied over that now-smaller area. The resulting change in stiction typically tips the balance from sticking to sliding. Now think about those sliding rear tires. These are the business end of the powerplant of the vehicle, and they are under their own forces moving perpendicular to the sideways force that just came loose from the track, and these forces have lots and lots of horsepower. Now all those horses are running free, if you will, spinning wildly for a brief moment because the tires broke free from the track. So to recap, the driver let off the gas, the car pitched forward, the rear tires broke free, the car slid sideways, the tires spun free, and the car slowed down a bit in about one second's time. Now the tires are spinning slower (because he let off the gas) and the car settles back down a bit (still only a second or two into the crisis). That means the now-slower rear tires can grab the track again and propel the car forward. But wait! The car is now pointed right at the wall because first it fishtailed and then the driver instinctively turned his wheels sharply in the same direction as the rear end's slide (toward the wall), and the car is again under acceleration, thereby *pitching the car's balance of downforces backward* and applying more force on the rear tires, making them really dig in and drive... And from that point on, that's all she wrote. Pro drivers who have truly retrained their instincts ride it out right into the wall with a nice, flat, safe full-on side hit, the way it was intended to be. I hope this has helped everyone's understanding of the science involved. I learned all this in the summer of 1979, just after graduating from military school, and it has saved my life twice so far in extreme conditions. Respectfully, Adam Phillip Churvis President Productivity Enhancement > -----Original Message----- > From: Vivec [mailto:[EMAIL PROTECTED] > Sent: Sunday, April 06, 2008 2:33 AM > To: CF-Community > Subject: Re: what a crash > > Coming off the wall, we see smoke from the tires at about 0:24s into > the video. Then in the next second he's away from the wall, but his > tires are still smoking a bit, I guess he lost traction somewhere up > at the wall. > > The back started to slide to the right, and he turned right into the > slide, it also seems that he came off the gas a bit. But look at the > video, and you see all this happens in a few seconds. > > Then the back of the car started rotating very rapidly to the left, > and he came off the gas a lot more. > > And the car started sliding, smoke from the tires etc. and he hit the > wall as it moved up the track. > > How was he supposed to have saved that? > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~| Adobe® ColdFusion® 8 software 8 is the most important and dramatic release to date Get the Free Trial http://ad.doubleclick.net/clk;192386516;25150098;k Archive: http://www.houseoffusion.com/groups/CF-Community/message.cfm/messageid:258080 Subscription: http://www.houseoffusion.com/groups/CF-Community/subscribe.cfm Unsubscribe: http://www.houseoffusion.com/cf_lists/unsubscribe.cfm?user=89.70.5
