So off I went into math land, and soon the class had a new found respect for the car/driver equation. The student that put the following article together has certainly gained a greater understanding of what his Porsche can and cannot physically do. We set up the most easy to understand drill, four cones in a straight line, which at most schools is simply a warm up drill. At ADSI it is a mathematical challenge and our students leave with a much greater appreciation and understanding or their vehicle. The following article was written by one of our students, Sterling Vernon. I personally thought it was worth sharing with everyone.
How hard can 4 cones in a row be to master? At the most recent ADSI high-performance driving school day on June 22, they treated us to a simple yet very effective (and humbling) exercise: drive through four cones laid out in a straight line 60 feet apart as fast as you can. Sounds easy, right?
(mine should be close to that), you get a vmax of 44.3mph. Here is our theoretical case: Pic 2
cones. If we do that, the radius of the arc goes up. And not by just a little.
So we drove the course, trying to bump our speeds up slowly while being measured by a radar gun to know our speeds on entry, midway, and exit. It was tough to maintain a constant speed, tough not to hit cones as you went faster and even more difficult to be smooth. We slowly started to beat our theoretical vmax speeds. The question became, how were we doing it? I was perplexed on the exact details and knew I had some math ahead of me. Boy was I rusty when it came to geometry and let’s not even talk about calculus... But I had to know how and why.
The radius goes up to a whopping 448.6 feet! And the vmax for an arc that size is 79.7mph! So if you could perfectly “cheat” one set of cones, you could run at 80mph instead of the paltry 44mph that should be the top speed.
If you did 100 cones in a row, I’d bet that you’d get really consistent with this drill and could rhythmically bang out a nice, even line at the vmax easily. Not being robots or Schumachers, we all made some mistakes in our short four cone drill. Sometimes we went in too hot and had to scrub some speed with hard turns and
In reality, about 47 or 48mph was the best I could manage at any given point. Real-world considerations like acceleration times and inability to fully cheat any section should be fairly obvious. This also shows how sacrificing corner entry speed on the corner right before a straight to get a better exit speed pays big dividends. After some time, it became intuitive and the math helped to make it that much more clear. Maybe it is now clearer to you also. It got really intense when the instructors put a row of cones as “walls” 7 feet away from the slalom cones on each side. Then the pressure Pic 1
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We sat down and calculated our theoretical max speed (vmax) first. We were taught that what determines your max speed is the radius of the curve you are driving and the grip of your tires. If you could drive perfectly close to the cones and your car is 5.5 feet wide and the cone is another foot wide, the center of your driving line begins 2.75 feet away from the center line. Then let’s assume that you’ll arc from the mid-point of a set of cones to the next mid-point. This gives you a radius for your arc of 138.5 feet. If your car can achieve 0.95G
some sliding. Sometimes we went too slow and could turn in a bit earlier and make up time. We certainly didn’t use brakes at all. So why could we exceed vmax at times without spinning? It appears to come down to the fact that the arc really can change a bit even in such a short course. And the effects are not small. Let’s look at a case where you turn in really quickly - right after the first cone, then round the second cone, and then aim for just the far side of the third cone. You are effectively making the arc as narrow and as long as it could be between the first and third
was on. We had to drive the slalom but inside these new “walls”. Speeds tumbled as we all summoned our courage and nascent skills. It was a humbling and fun experience. As I get older, not being able to be good at things is often far more interesting than things I’m good at.
About the Authors Anthony Ricci is President of ADSI (http:// www.1adsi.com) Sterling Vernon is a consultant to ADSI.