Hi Folks, I invite your attention to a one-page article by one of our
finest motorcycle tech writers, Kevin Cameron.
This is a fundamental subject to all speed trials racers, bike or car.
Kevin starts with the concept of a flat sheet of plywood, shoving this
through the air (like the grill shell of my '32 Ford with a steel panel
in it!). At 100 feet per second(68 mph) this flat sheet has about 12
pounds of air resistance per square foot on it, and at 200 fps(136 mph)
the same sheet experiences a resistance of 48 pounds per square foot,
since the drag force increases as the square of the speed. And the
horsepower required increases as the CUBE of speed.
A motorcycle-sized flat frontal area of 6 square feet has 288 pounds of
resistance at 136 mph, requiring 105 horsepower.
Our rounded surfaces, of course, do better, but the examples show the
critical importance of aero (in non-roadster classes!) in design. Ardun
Bill
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