text: EngineAir, an Australian company, is making a rotary engine powered by compressed air, called The Di Pietro motor.
  The Di Pietro motor concept is based on a rotary piston. Different from existing rotary engines, the Di Pietro motor uses a simple cylindrical rotary piston (shaft driver) which rolls, with little friction, inside the cylindrical stator.
  It can be used in boats, cars, burden carriers and other vehicles. Only 1 psi (≈ 6,8 kPa) of pressure is needed to overcome the friction. The engine was also featured on the ABC's New Inventors programme in Australia on 24 March 2004.