Data from Maurice Demoulin, Locomotive Actuelle ... (Paris: Librairie Polytechnique Ch.Beranger, 1906), p. 269 and []. See also Silvio Mazzardi, "Gr. 950" with rendering , Locotender in L'ALBUM FOTOGRAFICO Locotender e locomotive a scartamento ridotto - I disegni di Silvio Mazzard websiti at [], last accessed 23 February 2026. (Thanks to Stefano Carnicelli for his email giving the proper designations and supplying data for the two-cylinder version.) Works numbers were 2868-2873 in 1904.
Locobase struggled to find any other information outside of Demoulin's account in his book and Demoulin does not provide the driver diameter. Fortunately, the Italian modeller's site did, giving us information about wheelbases and fuel loadings. The design used a Smith-type compounding system in which the single 430 mm (16.93") HP cylinder on the centerline fed two 440 mm (17.32") LP cylinders outside. (See Locobase 2231 for a description of the Smith system.) The engines were rated at 480 hp and held to a maximum speed of 80 km/h (50 mph).
Mazzardi reports that tests showed the design actually operated better with only the two outside cylinders engaged so the railway removed the center cylinder. Locobase's data shows the simple-expansion version.
Carnicelli's data shows the shops changed little else during the conversions. Calculated tractive effort increased to 7,882 kg (17,378 lb; 77.3 k) and the constant-lead radial valve gear linkages were undoubtedly simplified. His report on routes states (in translation): "They served on the Milan-Turin line (according to Kalla-Bishop) or on the Asti-Chivasso line (according to Bonazzelli) until the 1920s."
They remained
The class was assigned to the Turin area, serving the Pinerolo - Torre Pellice line.
| Principal Dimensions by Steve Llanso of Middle Run Media | |
|---|---|
| Class | Gruppo 6900/950 |
| Locobase ID | 9187 |
| Railroad | Mediterraneo / FS |
| Country | Italy |
| Whyte | 4-6-4T |
| Number in Class | 6 |
| Road Numbers | 6901-6906 / 9501-9506 |
| Gauge | Std |
| Number Built | 6 |
| Builder | Hartmann |
| Year | 1904 |
| Valve Gear | Walschaert |
| Locomotive Length and Weight | |
| Driver Wheelbase (ft / m) | 10.63 / 3.24 |
| Engine Wheelbase (ft / m) | 31.17 / 9.50 |
| Ratio of driving wheelbase to overall engine wheelbase | 0.34 |
| Overall Wheelbase (engine & tender) (ft / m) | 31.17 / 9.50 |
| Axle Loading (Maximum Weight per Axle) (lbs / kg) | 29,762 / 13,500 |
| Weight on Drivers (lbs / kg) | 89,287 / 40,500 |
| Engine Weight (lbs / kg) | 164,244 / 74,500 |
| Tender Loaded Weight (lbs / kg) | |
| Total Engine and Tender Weight (lbs / kg) | |
| Tender Water Capacity (gals / ML) | 1584 / 6 |
| Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT) | 333.30 / 303 |
| Minimum weight of rail (calculated) (lb/yd / kg/m) | 50 / 25 |
| Geometry Relating to Tractive Effort | |
| Driver Diameter (in / mm) | 59.10 / 1500 |
| Boiler Pressure (psi / kPa) | 173.30 / 1180 |
| High Pressure Cylinders (dia x stroke) (in / mm) | 17.32" x 25.2" / 440x640 |
| Tractive Effort (lbs / kg) | 18,842 / 8546.60 |
| Factor of Adhesion (Weight on Drivers/Tractive Effort) | 4.74 |
| Heating Ability | |
| Tubes (number - dia) (in / mm) | |
| Flues (number - dia) (in / mm) | |
| Flue/Tube length (ft / m) | |
| Firebox Area (sq ft / m2) | |
| Grate Area (sq ft / m2) | 19.27 / 1.79 |
| Evaporative Heating Surface (sq ft / m2) | 1082 / 100.48 |
| Superheating Surface (sq ft / m2) | |
| Combined Heating Surface (sq ft / m2) | 1082 / 100.48 |
| Evaporative Heating Surface/Cylinder Volume | 157.45 |
| Computations Relating to Power Output (More Information) | |
| Robert LeMassena's Power Computation | 3339 |
| Same as above plus superheater percentage | 3339 |
| Same as above but substitute firebox area for grate area | |
| Power L1 | |
| Power MT | |