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The Ferrovie dello Stato Italiane (FS; Italian State Railways) Class 690 (Italian: Gruppo 690) was a 4-6-2 'Pacific' steam locomotive for express trains.
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| FS locomotive 69001 (later 690.001) | |||||||||||||||||||||||||||||||||||||||||||||
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The Ferrovie dello Stato Italiane (FS; Italian State Railways) Class 690 (Italian: Gruppo 690) was a 4-6-2 'Pacific' steam locomotive for express trains.
The Class 690 was designed just as the superheater technology was becoming available, allowing the FS to discard what had been a widespread feature on many Italian locomotives, the compound engine, deeming the advantages of the simpler single-expansion engine coupled with superheated steam to be superior. [1]
The English author Peter Michael Kalla-Bishop claims that, just before the production run, a prototype (numbered FS 6901) was built with a number of different features, but was so unsuccessful that it was withdrawn and quietly scrapped after just a few months. However, there is no reference for this claim, which is not repeated in any other document. [2]
The first nine locomotives, all with right-hand drive, were built in 1911 by Ernesto Breda (6) and the Officine Meccaniche (3); the following twenty-four, built in 1914 by Breda (14) and Gio. Ansaldo & C. (10) had left-hand drive. All of them had been designed for an axle load of 18 tons, but since this value was too high for even the current mainline railways, they all entered service with the load on the driving wheels lightened to 17.1 tons. They were the first Italian four-cylinder simple-expansion locomotives that had the feature of having the adjacent cylinders paired together and both served by a single piston valve through crossed ports (a feature shared by the more numerous Class 685). The firebox had to be placed between the rearmost driving wheels and was therefore of trapezoidal shape and relatively small; this feature would prove to be the locomotive's weakness, as it caused poor steaming and was expensive to maintain. [3] [2] [4]
Limited by their high axle load to the Milan-Venice and Milan-Bologna-Florence mainlines, the Class 690 did not prove to be satisfactory, as its poor steaming qualities greatly hampered the performance. While fast (being the first Italian locomotive certified for a mainline top speed of 130 km/h (81 mph) and powerful in absolute terms, relatively speaking its performance was modest – 1400 CV at 90 km/h (1,030 kW; 1,380 hp at 56 mph), while the Class 685 (which was smaller and had a shorter boiler) had a power of 1250 CV at 75 km/h (920 kW; 1,230 hp at 47 mph). [3] [5]
As a result, by the end of the 1920s a new three-cylinder Pacific locomotive (to be classified as Class 695) was designed; however, although more powerful than the Class 690, it would have required considerable strengthening of bridges and other infrastructures of the railways it was supposed to work on, because of an axle load of 21 tons. Therefore, a less ambitious plan to rebuild the Class 690 by replacing the boiler and firebox with those of the FS Class 746 was approved. From 1928 to 1934 all thirty-three locomotives were rebuilt into the new Class 691. [6] [7]
An articulated locomotive is a steam locomotive with one or more engine units that can move independent of the main frame. Articulation allows the operation of locomotives that would otherwise be too large to negotiate a railroad's curves, whether mainlines or special lines with extreme curvature such as logging, industrial, or mountain railways.
The Ferrovie dello Stato Class 740 is a class of 2-8-0 'Consolidation' steam locomotives.
The Ferrovie dello Stato Class 685 is a class of 2-6-2 'Prairie' express train steam locomotives. These are colloquially known as Regine, mirroring their fame as one of the most successful and appreciated Italian steam locomotives.
The Ferrovie dello Stato Italiane Class 691 is a class of 4-6-2 'Pacific' locomotives; they were the fastest and most powerful locomotives ever built for the Italian railways.
The Rete Adriatica Class 500, classified after 1905 in the Ferrovie dello Stato Italiane as Class 670 was an unorthodox and iconic cab forward 4-6-0 (2'C) steam locomotive.
The Ferrovie dello Stato Italiane Class 746 is a class of 2-8-2 'Mikado' steam locomotive. These were the biggest locomotives ever built by the Ferrovie dello Stato, even though not the fastest, which were the Class 691s.
The Ferrovie dello Stato Italiane Class 470 is a 0-10-0 steam locomotive.
The Ferrovie dello Stato Class 480 is a 2-10-0 steam locomotive.
The Ferrovie dello Stato Italiane Class 650, formerly SFAI1181-1200 and Rete Mediterranea 300 Class, also known as "Vittorio Emanuele II", was the first steam locomotive in continental Europe to have the 4-6-0 'Ten-Wheeler' arrangement.
The Ferrovie dello Stato Italiane Class 680 is a 2-6-2 express steam locomotive; it was the direct ancestor of the very successful and appreciated Class 685.
The Ferrovie dello Stato Italiane Class 552, formerly Rete Adriatica Class 180 bis, is a 4-4-0 steam locomotive; it was the final development in Italy of the 'American' express locomotive type.
The Ferrovie dello Stato Italiane Class 600, formerly Rete Adriatica Class 380 and Società per le Strade Ferrate Meridionali Class 380, is a 2-6-0 'Mogul' steam locomotive; it is considered by some as the first Italian modern steam locomotive.
The Ferrovie dello Stato Italiane Class 835 is a 0-6-0T steam locomotive; it was the standard steam shunter of the FS.
The Ferrovie dello Stato Italiane Class 290, formerly the Rete Adriatica Class 350 bis, is a 0-6-0 steam locomotive.
The Ferrovie dello Stato Italiane Class 420, formerly SFAI Class 1200, Rete Adriatica Class 420 and Rete Mediterranea Class 480, was a 0-8-0 steam locomotive.
The Ferrovie dello Stato Italiane Class 310, formerly Rete Mediterranea Class 380, was a 0-6-0 steam locomotive; they were the first Italian as-built compound locomotives.
The Ferrovie dello Stato Class 741 is a class of 2-8-0 'Consolidation' steam locomotives, rebuilds from the FS Class 740 with a Franco-Crosti boiler; it was the last class of steam locomotives introduced in Italy.
FS Class 400 were steam locomotives of French construction, built for service in Italy. They were 0-8-0 tender locomotives with two outside cylinders.
The Ferrovie dello Stato Class 745 was a class of 2-8-0 'Consolidation' steam locomotives.
The Ferrovie dello Stato Class 744 is a class of 2-8-0 steam locomotives; they were the last orthodox steam locomotives built for the FS.
