Nord Beyer-Garratt Locomotives in France

Class Details by Steve Llanso of Sweat House Media

Class 6.121 (Locobase 3251)

Data from "Locomotives at Liege," The Railway Magazine, Vol XI (15 August 1905), p.143. See also Dr. R. Sanzin, "Die Lokomotiven auf der Intertionalen Austellung in Mailand 1906, 34. 2x3/4 gekuppelte vierzylindrige Verbund-Tenderlokomotive der frazosischen Nordbahn ...", Zeitschrift des Oesterreichischen Ingenieur- und Architeckten-Vereines, Vol LIX, Nr. 12 (22 March 1907), pp. 211.-214; and "Sixteen-Wheel Double Tank Locomotive for the Northern Railway of France", Railroad Gazette, Volume XXXIX [39], No 14 (6 October 1905), pp. 322-324. Douglas Self''s entertaining "Unusual Locomotives" website supplied key details at [], last accessed 6 January 2019.

The RG account said the importance of the coal traffic and the profiles of the two main routes dictated the design. Over one of the options "the curves are of long radius and grades light". But the second one, which ran through Valenciennes, required helpers beyond that city to tackle grades of 1.2% while pulling 950 tons. On the flat, the designers were hoping for 30-37 mph (48-60 kph), while the locomotive might climb at 11-13 mph (18-21 kph).

In an attempt to lessen the energy loss entailed in leading steam exhausted from the HP cylinders powering the leading set all the way along a set of drivers to the LP cylinders at the rear, this du Bousquet design put the two pairs of cylinders under the center of the boiler. That is, two sets of Mogul wheel layouts faced each other under the steam dome. RG's page 323 offers diagrams showing the massive riveted backbone that provided rigidity to the locomotive.

Although it meant having a driver set lead the locomotive into the curves, the design certainly spread out the weight of the long side water tanks. At the speeds these engines were worked, the lack of leading truck probably didn't matter much. Also, the rear truck's mobility was limited to rotating around a central pivot only (which reduced steam leakage). The front truck had more degrees of freedom as well as carrying the water tanks.

The design obviously met with success and the growing stud initially operated from depots at Le Bourget and Hirson, where they worked the heavy coal trains on the Hirson-Valenciennes and Le Bourget-Lens routes. "However," Self added, "in the end most of their work was done on the Ceinture (Belt or Girdle) lines around Paris."

That service began in 1921 when 34 of the engines were assigned to the depot at Bobigny. The Ceinture services required tank locomotives able to travel in both directions with equal ease, and having enough tractive effort to draw heavy goods trains on an often difficult route profile, and the Du Bousquets met these needs effectively."

In 1935, the engines were reassigned to the main network as demand on the Ceinture had dropped.

Reder (1974) adds that similar engines went to China for the Peking-Hankow Railway, and to Spain for the Andalusian.

Principal Dimensions by Steve Llanso of Sweat House Media

Locobase ID3251
Number in Class48
Road Numbers6.121-6.168//2-031+130.TA.1 a 047
Number Built48
BuilderBW Hellemes
Valve GearWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m)11.38 / 3.47
Engine Wheelbase (ft / m)41.31 / 12.59
Ratio of driving wheelbase to overall engine wheelbase 0.28
Overall Wheelbase (engine & tender) (ft / m)41.31 / 12.59
Axle Loading (Maximum Weight per Axle) (lbs / kg)
Weight on Drivers (lbs / kg)199,359 / 90,428
Engine Weight (lbs / kg)223,368 / 101,318
Tender Loaded Weight (lbs / kg)
Total Engine and Tender Weight (lbs / kg)223,368 / 101,318
Tender Water Capacity (gals / ML)3379 / 12.80
Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT) 5.50 / 5
Minimum weight of rail (calculated) (lb/yd / kg/m)55 / 27.50
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)57.30 / 1455
Boiler Pressure (psi / kPa)227.70 / 15.70
High Pressure Cylinders (dia x stroke) (in / mm)15.75" x 26.77" / 400x680
Low Pressure Cylinders (dia x stroke) (in / mm)24.8" x 26.77" / 630x680
Tractive Effort (lbs / kg)31,967 / 14500.00
Factor of Adhesion (Weight on Drivers/Tractive Effort) 6.24
Heating Ability
Tubes (number - dia) (in / mm)130 - 2.756" / 70
Flues (number - dia) (in / mm)
Flue/Tube length (ft / m)15.58 / 4.75
Firebox Area (sq ft / m2)129.17 / 12
Grate Area (sq ft / m2)32.29 / 3
Evaporative Heating Surface (sq ft / m2)2632 / 244.55
Superheating Surface (sq ft / m2)
Combined Heating Surface (sq ft / m2)2632 / 244.55
Evaporative Heating Surface/Cylinder Volume436.01
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation7352
Same as above plus superheater percentage7352
Same as above but substitute firebox area for grate area29,412
Power L14762
Power MT315.96

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