Posted by: Grandma LaLa | August 17, 2014

Top 4 learnings from the FNAL lecture: speed

14-08-15 FNAL Lecture

Another great public lecture at Fermi National Accelerator Laboratory last evening, featuring Dr. Diandra Leslie-Pelecky on the topic of “The Science of Speed.”

Admittedly, I don’t care much about car-racing or NASCAR.  Having grown up in Indiana, for decades I have steadfastly resisted turning on the television on Memorial Day weekend, driving my car anywhere near Indianapolis on that weekend, or learning anything at all about the Speedway and the Indy 500.  So I was basically hoping that her topic would cover broader aspects of science about speed, including the physics related to space travel.  Well, not this time.

Even so, it was a fascinating lecture on a topic about which I previously knew absolutely nothing.  I learned a great deal from Dr. Diandra’s presentation, the top four points of which I’ll note for posterity.

  1. Fireproof suits
    Given the extreme risk of fire in a crash on these speedways, it makes sense that the drivers wear fireproof suits.  A gasoline fire can burn at 1200 degrees Fahrenheit – or hotter!  For years, the drivers wore materials that had been dipped in fire-retardant fluids, but these fluids washed out when the clothing was laundered.  Not good!  Now they wear fire-retardant underwear, gloves, shoes, and fitted clothing.  NASCAR tried treating with kevlar, but it does become flammable at 900 degrees.  More commonly, they used nomax, which has a molecular content identical to kevlar, but the molecules are arranged differently.  So nomax withstands heat and flame for longer and for higher temperature.  A third product (whose name I can’t recall) is pre-burned and actually the best protection, allowing the driver several extra seconds of fire protection.
  2. Short-life tires
    Goodyear supplies all of the tires used in NASCAR racing, with an eye-popping price of more than $450 per tire!  The tires are between 11 and 12 inches wide, with only one-eighth inch of tread.  This is part of the reason that NASCAR races are suspended if it rains.  These tires usually last for only 50-100 miles!
  3. Down force
    I really hadn’t thought about the forces outside the cars, given their speed on the track.  That includes the aerodynamic forces.  Dr. Diandra described the down force on the front of the car as oncoming air hits the front of the hood.  That down force helps to keep the front tires gripping the surface.  So what keeps the rear tires gripping?  As the oncoming air continues over the top and back of the car, there is a bar similar to the spoiler on regular vehicles.  It breaks the airflow enough to convert some of that air pressure into a second downward force, which helps to keep the rear tires gripping the surface.
  4. G-force
    I also hadn’t thought about the forces inside these cars, as they are driving and turning (60% of the time) at speeds of 160 mph and higher.  As I recall, Dr. Diandra’s own test-drive at speeds of 160 mph meant that she would experience 2-G in those turns.  Think of how much physical strength it takes just to keep one’s head and shoulders stable enough to safely drive those speeds in a race!  One earlier driver used rope to tie his helmet to a part of the car, just to try to stabilize.  Now they have a built-in stabilizer bar right next to the helmet to somewhat reduce the stress.

The thought of watching cars racing around a track is still not an enticing entertainment for me, but I have a whole new appreciation for what’s involved in these and other aspects of the “science of speed!”

 

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