Archive for Month: June 2012

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Why 200 mph Laps at Michigan are not like 200-mph Laps at Daytona or Talladega

That fact that people are even talking about restrictor plates for Cup racing at Michigan International Speedway indicates a lack of understanding of the issues that give rise to concerns about cars getting airborne.

I touched on the difference between average and instantaneous quantities last week with the pit road speeding issue at Pocono. Instantaneous speed is the speed you are going at some particular instant. A radar gun measures instantaneous speed.

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Pocono: The Shifty Triangle

NASCAR engines like to run at about 8000-9500 rpm (revolutions per minute); however, the tires on the car rotate around 2400 rpm at 200 mph. The gearing in the transmission and the rear end gear reduce the rotational engine speed, with different gears providing different reductions. When you talk about the size of a gear, you’re actually talking about the relative sizes of a pair of gears. The gear on the left in the diagram has 20 teeth, while the gear on the right has 10 teeth, so this gear would be a 2:1, meaning that the smaller gear rotates twice every time the larger gear rotates once.

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