Ferrovie dello Stato / Ferrovie dello Strato 2-6-2 Locomotives in Italy

Class Details by Steve Llanso of Sweat House Media

Class Gruppo 680 (Locobase 8955)

Data from Albert H Bone, "Some Recent Designs of Locomotives for Service on Continental Railways", Cassier's Magazine, 1910, pp. 561-609. See also "A Balanced Compound Locomotive for Italian State Railways," The Railroad Gazette, Vol XLIII, No 5 (2 August 1907), pp. 128-132. Breda delivered 91, Ansaldo 40, and Berliner Maschinenbau 20.

Bone explains that a Prairie design suited those circumstances when an Atlantic had too little adhesive weight and the Pacific was too long or too heavy He further notes that this design, supplied both by Breda and by Berliner Maschinenbau, used the Zara truck (which like the Krauss-Helmholz truck combined the leading truck and the first coupled axle in a bogie). Instead of a pivot, however, the Zara truck used a swing bolster with the result that, says the RG report, "...any difference which may arise between the pilot and leading wheels, when on a sharp curve, as to which shall yield at either end of the fulcrum lever, is decided by the action of the swinging bolster which accommodates such differences."

Bone summarized the advantage of a design that "...combines the advantages of the 2-6-2 type with the easier running on curves of the Atlantic ..."

680s used the same Plancher compound setup found in the cab-forward Gruppo 670 4-6-0s ((Locobase 1472). Yet another four-cylinder compound layout, this design varied from the others by placing both low-pressure cylinders on the right side of the smokebox and the two high-pressure cylinders on the left. The design always worked compound and had no intercepting valve, although some HP steam was admitted to the LP steam to start moving the locomotive.

The piston valve for the HP cylinders measured 288 mm (11.34") in diameter and had crossed ports. Exhausted steam then went to a receiver that directed the steam to a valve with two slightly separated pistons in tandem. For each set, the intent was to admit steam to opposite ends of the two cylinders at the same time, The cranks turned by the rods were set 180 deg apart. Thus the goal was to balance the forces in both same-side cylinders as well as the left and right sides of the smokebox. The latter would be achieved, theoretically, by achieving a good compounding ratio in the original design.

Designed for 75 mph in express service pulling 400 metric tons (440 short tons), they would also haul accommodation trains (frequent stops, lower top speeds) of 450 metric tons. (495 short tons). In international service pulling the "trains de luxe", they were found "to pick up, easily 30 minutes and more, lost in delays during a run. " A surprising finding was that the Welsh coal evaporated at most 7.5 lb of water for every pound of fuel. Nevertheless, RG reported, "their boilers generate an abundance of steam in respect to the very economical steam consumption by the engines."

Yet, this class did not long dominate passenger service as designers revamped the design for simple expansion and superheated boilers. First delivered in 1912, the resulting 685s were a great success; see Locobase 2488.

91 of the 680s later received superheaters from 1917 to 1924, but kept their compound setup and were redesignated 682; the last fifteen of these used larger HP cylinders. When that failed to improve performance sufficiently, they were then fully updated as 685s.

Class Gruppo 685 (Locobase 2488)

Data from the US Military Railway Service's Equipment Data Book for Italian Locomotives supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. See also "Prairie Type Express Locomotive, Italian State Rys," Locomotive Magazine, Volume XIX [19] (14 June 1913), p. 122. See also at the website for the Leonarda da Vinci National Museum of Science and Technology at [], last accessed 10 April 2019.

Developed by FS engineers of the Ufficio d'Arte di Firenze, these were passenger engines able to run on parts of the system that couldn't take the Series 690 Pacific 19,000 kg (41,888 lb) axle load, this class was widely distributed because of their lighter axle load and the flexibility afforded by the Zara truck. It was credited by the MRS with 22,440 lb of steam per hour and rated at 1,250 hp at 45 mph.

The Leonardo da Vinci Museum account observes that while there were no particularly innovative features of this locomotive's design, it demonstrated "una perfetta sintesi di affidabilità, efficienza, economicità, versatilità e facilità di condotta." (Locobase translation: a perfect synthesis of reliability, efficiency, economy, versatility and ease of operation.)

Curiously, the first 106 locomotives, which were delivered before the beginning of World War One, were set up for right-hand running. The post-war engines were configured for left-hand running.

Hollingsworth (1982) infers from the Vauclain-like common piston valve for both cylinders on a side that these engines were not as free-running as they might have been. He notes that 127 were later fitted with the Caprotti poppet valve system. Some later pulled tenders carrying 29,000 litres (7,662 US gallons) of water

Ugo Poddine, contributor to Bryan Attewell ([] Steam locomotive simulator (April 2000), gives slightly different heating surface sizes. His production total reaches only 241 altogether. He pronounces this class "the 'Queen' of Italian locomotives."

Class Gruppo 910 (Locobase 6623)

Data from the US Military Railway Service's Equipment Data Book for Italian Locomotives supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. See also Dr. R. Sanzin, "Die Lokomotiven auf der Intertionalen Austellung in Mailand 1906, 21. 3/5 gekuppelte zweizylindrige Verbund-Tenderlokomotive der italienischen Staatsbahnen ...", Zeitschrift des Oesterreichischen Ingenieur- und Architeckten-Vereines, Vol LVIII Nr. 51 (21 December 1906), pp. 719-720; "Locomotiva FS 910" in Wikipedia at [], last accessed 28 July 2022; and "Diesel-Zarlatti locomotive" in Wikipedia at [], also last accessed 28 July 2022.

As noted in Locobase 6217, the Strade Ferrate della Sicilia had taken delivery of six relatively large tank engines.When the FS took over the SFS, it built six more of nearly identical dimensions. The boiler was shorter and the grate slightly larger. The Military Railway Service book credited this class with 15,840 lb (7,185 kg) of steam per hour and rated at 890 hp (664 kW) at 27 mph (44 kph).

Many of these locomotives operated out of Milan.

Wikipedia reports on a conversion experiment conducted with the 910.042 in April 1929. The shops removed the engine's boiler and replaced it with a two-stroke, 325 hp (242 kW) Diesel-Zarlatti hybrid engine. A naphtha-fired boiler heated water to provide steam to the cylinders upon starting. (This was necessary because compressed air cools when it expands and could ice up the cylinders.) Once the engine began moving, the hybrid system blended steam and compressed air. This drove a Swiss-built rotary compressor that sent high-pressure air into the existing two cylinders.

Although it completed sixteen trips, the system suffered several component failures and the FS abandoned its research.

NB: Direct (firebox) heating surface area is an estimate derived from calculating the tube heating surface area and subtracting it from the given evaporative heating surface area. Also, Wikipedia's Diesel-Zarlatti provides links to Italian-language documents explaining the system in detail.)

Principal Dimensions by Steve Llanso of Sweat House Media

ClassGruppo 680Gruppo 685Gruppo 910
Locobase ID8955 2488 6623
RailroadFerrovie dello Stato (FS)Ferrovie dello Stato (FS)Ferrovie dello Strato (FS)
Number in Class14939048
Road Numbers6801-6899, 68100-68149685.001 to 685.3919107-9154
Number Built14927148
Valve GearWalschaertWalschaertWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m)12.96 / 3.9512.96 / 3.9512.47 / 3.80
Engine Wheelbase (ft / m)27.72 / 8.4527.72 / 8.4527.56 / 8.40
Ratio of driving wheelbase to overall engine wheelbase 0.47 0.47 0.45
Overall Wheelbase (engine & tender) (ft / m)58.81 / 17.9327.56 / 8.40
Axle Loading (Maximum Weight per Axle) (lbs / kg)34,760 / 15,767
Weight on Drivers (lbs / kg)99,869 / 45,300102,960 / 46,70292,594 / 42,000
Engine Weight (lbs / kg)156,799 / 71,123158,620 / 71,949141,096 / 64,000
Tender Loaded Weight (lbs / kg)90,389 / 40,500110,220 / 49,995
Total Engine and Tender Weight (lbs / kg)247,188 / 111,623268,840 / 121,944141,096 / 64,000
Tender Water Capacity (gals / ML)5190 / 226050 / 22.921848 / 7
Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT) 6.60 / 6 6.60 / 6 3.90 / 3.50
Minimum weight of rail (calculated) (lb/yd / kg/m)55 / 27.5057 / 28.5051 / 25.50
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)72.80 / 185072.80 / 185059.10 / 1500
Boiler Pressure (psi / kPa)227.70 / 15.70174 / 11.70188.50 / 13
High Pressure Cylinders (dia x stroke) (in / mm)14.17" x 25.59" / 360x65016.54" x 25.59" / 420x650 (4)18.11" x 23.62" / 460x600 (1)
Low Pressure Cylinders (dia x stroke) (in / mm)23.23" x 25.59" / 590x65027.56" x 23.62" / 700x600 (1)
Tractive Effort (lbs / kg)19,912 / 9031.9428,445 / 12902.4514,668 / 6653.30
Factor of Adhesion (Weight on Drivers/Tractive Effort) 5.02 3.62 6.31
Heating Ability
Tubes (number - dia) (in / mm)273 - 2.047" / 52171 - 2.063" / 52222 - 2.047" / 52
Flues (number - dia) (in / mm)24 - 5.25" / 133
Flue/Tube length (ft / m)16.90 / 5.1516.89 / 5.1512.66 / 3.86
Firebox Area (sq ft / m2)126.97 / 11.80142.04 / 13.20120.02 / 11.15
Grate Area (sq ft / m2)37.66 / 3.5037.66 / 3.5025.62 / 2.38
Evaporative Heating Surface (sq ft / m2)2361 / 219.402064 / 191.821636 / 152
Superheating Surface (sq ft / m2)522 / 48.51
Combined Heating Surface (sq ft / m2)2361 / 219.402586 / 240.331636 / 152
Evaporative Heating Surface/Cylinder Volume505.49162.17464.64
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation857565534829
Same as above plus superheater percentage857578634829
Same as above but substitute firebox area for grate area28,91129,65822,624
Power L1659412,3955092
Power MT436.69796.22363.71

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