The gyro locomotive was a locomotive for mine railways built in 1954 by Maschinenfabrik Oerlikon (MFO) , whose drive technology for flywheel storage was based on the gyrobus, which was first introduced four years earlier . The only ever existing rail vehicle with this drive technology was built for the iron ore mine in Saint-Pierremont , France . The machine did not prove itself there, however, because insufficient charging was not possible due to insufficient power supply. She then came to the Gonzen iron mine in Sargans , Switzerland . It was used there until ore mining was discontinued in 1966. After a long period of inactivity, the locomotive was reactivated and since 1994 has occasionally been used in front of visitor trains in the disused mine.