FS Class 685

FS Class 685

300px FS locomotive 685.089 in 2010

Type and origin Power type Steam Builder Ernesto Breda, Officine Meccaniche di Saronno, Reggiane Build date 1912–1928 Total produced 271 + 120 rebuilds

Specifications UIC class 1′C1′ h4 Gauge 1,435 mm (4 ft 8 1⁄2 in) standard gauge Leading dia 960 mm (37.80 in) Driver diameter 1,850 mm (72.83 in) Trailing dia 1,220 mm (48.03 in) Length Axle load 15.1 tonnes (14.9 long tons; 16.6 short tons) Loco weight 70.8 tonnes (69.7 long tons; 78.0 short tons) Tender weight 49.6 tonnes (48.8 long tons; 54.7 short tons) Fuel type Coal Fuel capacity 6,000 kg (13,000 lb) Water cap 22,000 litres (4,800 imp gal; 5,800 US gal) Boiler pressure Firegrate area 3.5 m2 (38 sq ft) Heating surface 191.8 m2 (2,065 sq ft) Superheater:  • Heating area 48.54 m2 (522.5 sq ft) Cylinders Four, simple Cylinder size 420 mm × 650 mm (16.54 in × 25.59 in) Valve gear Walschaerts (early production), Caprotti (late production)

Performance figures Maximum speed 120 km/h (75 mph) Power output Tractive effort

The Ferrovie dello Stato (FS; Italian State Railways) Class 685 (Italian: Gruppo 685code: it is deprecated ) is a class of 2-6-2 'Prairie' express train steam locomotives. These are colloquially known as Regine ('Queens' in Italian), mirroring their fame as one of the most successful and appreciated Italian steam locomotives.

Design and construction

The Class 685 was the simple-expansion and superheated version of the pre-existing FS Class 680 locomotive, the premier express locomotive in Italy up to that date; while discarding the complicated compound feature, the 685 nonetheless kept the unusual feature of having the cylinders arranged in pairs, with each pair being served by a single piston valve with crossed ports (a feature typical of the Plancher engine of the Class 680 and other Italian locomotives).

The first 106 locomotives were built up to World War I, and had right-hand drive; construction resumed in 1920, and the remaining 165 were all built, up to 1928, with left-hand drive and a slightly longer boiler. Of the latter, 30 were built from the beginning with Caprotti valve gear, after it had been tested first on a FS Class 740 locomotive and then on other four 685 locomotives; all of these were initially reclassified as FS Class 686 locomotives, but were later placed again into the Class 685.

Operations

The Class 685 was present on all the Italian mainlines before their electrification, thanks to its good performance related to its moderate axle load; the Class S.685 locomotives mainly operated on the Milan-Venice and Milan-Turin mainlines, together with the FS Class 691 'Pacifics'. It was renowned as a well-balanced design, especially for its very smooth riding qualities, and was pretty much universally appreciated. Despite being express locomotives, especially in the waning years of the Italian steam they proved to be apt for freight train pulling as well.

The maximum authorized speed for the Class 685 locomotives was originally 110 km/h (68 mph); from 1932 it was raised to 120 km/h (75 mph).

The first units to be withdrawn from service, in the mid 1960s, were the heavier S.685 locomotives, and the more maintenance-requiring Caprotti and Franco-Crosti locomotives; the last unit in active service, the 685.222, was withdrawn in early 1975.

Conversions

Rebuilds from the 680 class

The by then-obsolete FS Class 680 locomotives were first subjected to a first rebuild, in which 91 of them were superheated but kept the compound engine (with some of them receiving a larger high pressure (HP) cylinder); after it was determined that these locomotives were still inferior in terms of performance and water and coal consumption, it was decided to rebuild them into Class 685 locomotives, instead.

The first group, renumbered as 685.3XX, received the superheater and a simple-expansion engine, while keeping the original boiler pressure of ; the second, 685.5XX, also received the Caprotti valve gear. Finally, the last batch of rebuilds was subjected to an increase of its adhesive weight (by shifting the pivots of the Italian bogie and the trailing axle towards the driving axles) to improve performance, bringing their axle load up to 17 tons, and were fitted with a Knorr pre-heater (some of them also received a larger tender with a total water capacity of 29,000 L (7,700 US gal); based on their increased performance, they were classified as the separate Class S.685 ('S' standing for Speciale). In total, 120 ex-Class 680 locomotives were eventually rebuilt, until 1933, bringing the total number of locomotives in the Class to 391.

Franco-Crosti

In 1939 five locomotives (amongst those fitted with Caprotti valve gear) were rebuilt with Franco-Crosti boilers; initially classified into the Class S.685, in 1951 they were reclassified as FS Class 683.

Turbine locomotive

In 1933 the locomotive 685.410 had her cylinders replaced by a large forward motion steam turbine and a smaller reverse turbine; this experiment, under the guidance of renowned engineer Giuseppe Belluzzo, was completely unsuccessful, and the locomotive was restored to its previous condition in 1934.

Preservation

Five Class 685 locomotives survive into preservation:

• The 685.089 and 196 are currently operational;
• The 685.068 is a static exhibit at the Pietrarsa railway museum;
• The S.685.600 (the 1000th locomotive built by the Ernesto Breda company) is a static exhibit at the Museo della Scienza e della Tecnologia "Leonardo da Vinci";
• The 685.222 is awaiting restoration at Pistoia.