FS Class 690 II

The Class 690 was a four-cylinder 4-6-2 Pacific steam locomotive built for the Italian State Railways between 1911 and 1914, thirty-three in all. It was designed just as superheater technology made compound engines unnecessary, and it was the first Italian simple-expansion locomotive whose adjacent cylinders were paired and served by a single piston valve. Breda, Officine Meccaniche and Ansaldo shared the building, with Ansaldo producing ten of the later engines, which had left-hand drive. The class was fast, being the first certified for 130 km/h, and rated at about 1,400 horsepower, but a narrow firebox set between the rear driving wheels gave poor steaming, and an axle load of 17.1 tonnes kept it to the Milan to Venice and Milan to Florence main lines. No more were built, and at the end of the 1920s the class was rebuilt as the Class 691.