The FS Class 740 were designed as the simple expansion and superheated version of the earlier FS Class 730; after the success of the FS Class 640. The first locomotives were built in 1911, and the production continued (with a long interruption caused by World War I) throughout 1923; in total, 470 were built, making the Class 740 the most numerous locomotive to be built for the Ferrovie dello Stato. The first locomotives were built with right-hand drive, but from 740.204 this was changed to left-hand drive; some of them had a six-wheels tender, while others had a bogie tender with higher water capacity.
Built for heavy freight work, the Class 740 saw service on the whole FS network, with virtually any train shed having had some of them assigned to it at some point; other than freight trains, they were also usually employed for passenger services on secondary lines. Having been built for wide route availability (and therefore requiring a low axle load), they are generally considered successful locomotives, well-suited for the role they were built for, although some have criticized their rather poor steaming; although their official top speed was set at 65 km/h (40 mph), several locomotives have proven to be able to reach higher speeds, around 80 km/h (50 mph).
The Class 740 remained in active service until the end of regular Italian steam, in the 1970s; some of the class were still assigned to various sheds as reserves in the early 1990s.
In 1921 locomotive 740.324 became the first FS locomotive to be fitted experimentally with Caprotti valve gear; the results were satisfactory, and locomotives 740.440–740.445 were modified during construction with the new valve gear and were classified in the separate Class 741, to be renumbered in 1930 as 740.691-697. An improved valve gear was fitted in 1932 to 740.352, which was renumbered 740.852; the valve gear was replaced by standard Walschaerts valve gear in 1955, and the remaining locomotives with Caprotti valve gear (which, although more efficient, required more refined maintenance) were withdrawn by the 1960s.
In 1942 five 740 (numbers 339, 367, 392, 396 and 405) were rebuilt with a Franco-Crosti boiler, and fitted with a streamlined casing (more for aesthetical reasons than for any aerodynamic advantages). In 1951 these locomotives (with the casing removed) were renumbered into the FS Class 743, and 88 more were rebuilt until 1953. A modified version, with a single pre-heater under the boiler (instead of two placed alongside it), was classified as FS Class 741, and 81 of them were rebuilt between 1958 and 1960.
Forty-nine Class 740 locomotives have survived into preservation. Five of them (the 740.038, 244, 293, 409 and 423) are currently operational and available for heritage trains.
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