Fourcylinder compound 2-8-2 express train steamlocomotive 746 # 031 of the Ferrovie dello Stato, exhibited in the Museo Nazionale Scienza e Tecnologia Leonardo da Vinci in Milan. After the First World War, the FS locomotive fleet had to be renewed with more powerful series. Because no renewal work had been carried out on the lines during the war, the axle load could not be raised above 17 tons, even on main lines. An express locomotive with four coupled axles therefore had to be built that could withstand these axle loads. It was used for heavy express trains with a maximum speed of 100 km/h. Operation:
After delivery in 1923, the locomotives were assigned to the depots in Rome San Lorenzo, Naples and Florence, and later also Milan. After the Naples-Rome-Florence main line was electrified in 1935, the locomotives were withdrawn from Rome and Florence and assigned to the depots in Ancona, Salerno and Reggio Calabria. After the Salerno-Reggio di Calabria line was also electrified in 1937, the locomotives were transferred to the Catania depot in Sicily. During the Second World War, some locomotives were also assigned to the Turin depot. However, they returned to the depots in Ancona and Catania until 1957, where they ended their service in the mid-1960s.
The 746 # 031 on display at the Museo della Scienza e della Tecnologia in Milan is the only surviving locomotive in the series. It is considered a technical cultural monument of Lombardy. The 746 # 038 was stored in Verona for a long time before being transferred to Pistoia in the 2010s.
The FS 746 locomotive is of the Mikado type. The running gear consists of a steel frame in which the four coupled axles are mounted. There is one running axle in front of and one behind the coupling axles for track guidance and weight distribution. The leading axle is combined with the first coupling axle to form a Carrello Italiano.
Propulsion is provided by a four-cylinder hot-steam compound engine. In contrast to most Italian compound locomotives, the Borris design was used instead of the Plancher design with drive to the third coupling axle and internal high-pressure cylinders.
Most of the locomotives had an external Walschaerts control system that drove the piston valves of both pressure stages, some were equipped with Caprotti valve control. These locomotives were originally assigned to the 747 series, but were given new serial numbers in the 100 range of the 746 series in 1929.
After the Second World War, some locomotives were equipped with oil firing. Text from Wikipedia.