One of the most successful in the series of rucksack-type personalised flying machines, Hazerug is powered by a 250cc, 60hp single cylinder motor. The motor powers two propeller blades which rotate at a speed of up to 8,000 revolutions a minute; close to the speed of sound. The motor is contained within a protective crown or enclosure constructed of Kevlar, a very strong, lightweight plastic used for bullet-proof vests and mooring ropes for ships. Hazerug was tested successfully at the University of Brussels in 1997 using a lead mannequin weighing 100kg.
© Maths Museum
'Hazerug' was tested in a small, glass-enclosed room inside a bigger laboratory from where I controlled it with a cable attached to the carburettor. Once the motor started functioning, the propeller blades began to rotate so quickly that they surpassed the speed of sound and began to produce sound barrier-breaking booms. The motor was also supplying its own noise and although there was a noise suppressor around the resonance pipe it didn't help much because an equal amount of noise was coming from the propeller. (A fan like the one on 'Shell-shaped Rucksack', 1986 would be far quieter because its speed is only 1,000 or 2,000 revolutions a minute instead of 8,000 and so it doesn't reach the sound barrier.) In a way it was lucky that the thing was producing all that noise because noise produces fear. All the people who were with me in the laboratory got scared and ran away and pretty soon, because of the pressure of the huge centrifugal forces on the propeller, the entire thing exploded.
When we tested it again the next day the same thing happened. The machine started to fill with gas and as the noise increased air began to pour out of the two corrugated pipes. Then the puppet rose a couple of centimetres from the floor. At that point I released the power because otherwise the whole figure would have started flying sideways around the room like a rocket. Because we were on the side of the thing that is made of Kevlar we knew that we were safe. If it exploded while it was strapped to your back nothing would happen to you because the Kevlar acts like a shield.
Motor, metal, Kevlar and fabric.
Ronny Van de Velde Gallery, Antwerp