Developed by the Swiss company Oerlikon in the fifties, gyrobuses were used for approximately 7 years at Yvernon and Grandson in Switzerland, Léopoldville in Belgian Congo, and in Gand in Belgium. An electric engine is powered by a large 4500kg flywheel.
Once the flywheel is launched, its kinetic energy is converted into electric energy and powers the propulsion engine.
During passengers’ ascent and descent, the flywheel is reloaded then put back into rotation. This system could reach a speed of 50-60 km per hour for an autonomy of about 6km.
The gyrobus offered several advantages : it did not pollute much (except for electricity production), it was not very noisy and, unlike the trolleybus, it did not require contact with overhead power lines all through its route as it was charging only at specific stops. However the relatively long charging time of the flywheel (3 to 4 minutes), in addition to the danger caused by the flywheel weighing more than a ton and working at 3,000 revolutions per minute led to abandon this kind of vehicle in the late sixties.
Nowadays flywheels are increasingly developed for energy storage. In Rennes (France) for instance, the energy produced by the subway’s braking action is stored into a flywheel, to be transformed later back into electricity.
