oTire Shakee


Recent discussions on the Standard 1320 Group have urged me to elaborate on the subject of "tire shake." Interestingly enough, I was watching the TV coverage of the Bristol race this past weekend, and they did make quite a big point about the shake situation. More than one race was lost when the weenies got to wobbling.

This problem, of course, is nothing new. We've had to deal with it for 30 years. When things started to get really nasty in the early '70s, everyone was trying to get a handle on it --with no apparent success. Turns out that Pepe Estrada (no relation, that I know of, to Erik Estrada of CHiPs fame) had a friend who was on staff at the California Institute of Technology in Pasadena, one of the nation's premiere "think tanks" for all matters scientific. This professor got a diversified group of his colleagues together to try and figure things out. A somewhat formal symposium was organized. Tony Nancy brought his car to the Cal Tech campus so those not familiar with drag racing could get a hands-on "feel" for the car, and Tony provided "real life" input. There were a few NHRA staffers there, as well as Pepe. I was there to provide coverage in National Dragster. On the Cal Tech side there were about a half-dozen PhDs of various disciplines, like hydro-dynamics, etc. As it turns out, they could not come to a consensus and each of them come forward with their own theories.

The one I was most impressed with postulated that the coefficient of friction between the clutch and flywheel was not alwlays constant, and it would be possible for a "harmonic" to devlop. This, in turn, would be amplified by the driveline and tire...resulting in a severe "shake." I personally believe there is a critical "balance point" between engine output, the energy transmission "medium," tires and the track itself. Now, I got Tom West to "buy into" this little theory...and he's been around this sport for a couple weeks. He also has, which most people don't know, a degree in Mechanical Engineering from the General Motors Institute in Detroit. So I'm not simply "pulling the wool over the eyes " of some dumbass photographer.

That said, I'm no engineering guru. Just a marketing guy (who happened to race Top Fuel for a number of years). But until someone comes up with a better theory, I'm inclined to believe the ol' Cal Tech prof. Now, I will temper this statement by saying that we had absolutely NO on-board telemetering equipment back in those days that could be used for input. Perhaps, there is enough meaningful data being acquired today to clarify matters. Or, maybe they still can't collect enough data points between engine RPM, shaft speed, wheel speed, etc. to conclusively identify the culprit. I, for one, would be interested to see what others have to say. Meanwhile, I'll try and pin down one of the Racepak guys and get their take on the whole matter. Film at 11.

Bill Holland
(a resident of Northridge, CA --where EVERYTHING shakes)


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