Red Bull.com

“The feeling while rushing down a hill is one of total concentration. You mustn’t lose it and you need to stay absolutely focused, watching the speedo in front of you. But you also need to be aware of the conditions and the crowd. It only requires one idiot to step onto the track to cause a real accident.

“We follow a drivers’ line, like in Formula One, but the skill is about learning when to use the brakes and when not to. The idea is really not to use the brakes at all, so it’s essential to walk the course first. Some courses are over two miles long. The adrenaline rush comes afterwards, not during, because you should be concentrating on the job on the way down.
 

“There are two types of racer: a roadster and a streamliner. In the streamliner, you’re locked in, bolted down and belted up, and it’s built to crash. They’re are always slightly faster because they present less of a frontal area. You just kneel down and look straight on.

“The roadster is cut away, and if you crash in that, you’re thrown clear. Drivers always wear good leathers and helmets, whatever they’re driving. There have been crashes, but the worst you’re really going to get is a stiff neck.”

 

“A soapbox race mimics one of Galileo’s most famous experiments,” says Thomas Schrefl, Professor of Communications & Simulation Engineering at the St Pölten University of Applied Sciences in Austria. “He used inclined planes and small metal balls to revolutionise our knowledge of gravity and acceleration.
 

“Let us first assume there is no friction and no air drag. The total potential gravitational energy at the start, Epot = mgh, will be the same as the total kinetic energy, Ekin = mv²/2, when the soapbox passes the finish line. Equating both energies shows that the mass, m, cancels, and the final velocity, v, is v = (2gh)^1/2. It only depends on the acceleration due to gravity, g, and the difference in height between start and finish, h. This simple theory predicts a velocity of about 100mph (160kph) if the soapbox runs a distance of 1,000m with a gradient of 10 per cent.
 

“As long as Galileo’s ball descends, its speed will increase. The balls were small in diameter and air resistance was negligible. We can use Newton’s first law of motion to compute the final velocity: the velocity of a moving object remains constant if the sum of the force due to gravity, Fa, and the drag force, Fw, is zero. Rolling friction of bicycle tyres reduces the acceleration due to gravity by a factor of 0.93. The smaller the drag coefficient, Cw, the smaller the cross-sectional area, A, and the higher the mass, the higher is the ultimate velocity. We can estimate these parameters from the photo. With a total mass of 160kg, the final velocity is 31mph (50kph) and the driver will finish the race in 82 seconds. In a two-man racer, the greater total mass, thanks to a co-driver, increases the maximum speed to 38mph, and they pass the finish line 10 seconds earlier.”

 

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