Bengal Nagpur 4-4-2 Locomotives in India

Class Details by Steve Llanso of Sweat House Media

Class K (Locobase 3026)

Data from Ahrons (1927). See also R A S Hennessey, Atlantic: The Well-Beloved Engine (Stroud, Gloucestershire: Tempus Publishing Co, Ltd, 2002);"New Locomotive Types: Bengal-Nagpur Railway", Railway Times, Volume XCIV [94], No 14 (3 October 1908), pp. 370-371; and "Calcutta-Madras Mail Trains, Bengal Nagpur Ry", Locomotive Magazine, Volume XXI [21] (15 July 1915), p. 146.

Based on the British Engineering Standards Association Atlantic design, these Bengal Nagpur locomotives offered a twist. As Roger Hennessey puts it, the BN was "...a thorn of individualism in the side of the standardisers [and] insisted on a 4-cylinder de Glehn compound version." The first pair were supplied on a trial basis and could be returned within 12 months if the BNR was not satisfied.

The BNR was more than satisfied. The Ks were certainly bigger than most engines of that arrangement in Great Britain at the time. De Glehns put their HP cylinders outside to drive the second axle while the inside LP cylinders drove the leading axle. These had a Belpaire firebox offering a heating surface of 153 sq ft.

Principal Dimensions by Steve Llanso of Sweat House Media

Locobase ID3026
RailroadBengal Nagpur
Number in Class15
Road Numbers
Number Built15
BuilderNorth British
Valve GearStephenson
Locomotive Length and Weight
Driver Wheelbase (ft / m)7 / 2.13
Engine Wheelbase (ft / m)28 / 8.53
Ratio of driving wheelbase to overall engine wheelbase 0.25
Overall Wheelbase (engine & tender) (ft / m)50.87 / 15.51
Axle Loading (Maximum Weight per Axle) (lbs / kg)38,640 / 17,781
Weight on Drivers (lbs / kg)78,400 / 35,562
Engine Weight (lbs / kg)161,728 / 73,359
Tender Loaded Weight (lbs / kg)90,160 / 40,896
Total Engine and Tender Weight (lbs / kg)251,888 / 114,255
Tender Water Capacity (gals / ML)4200 / 15.91
Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT) 6.60 / 6
Minimum weight of rail (calculated) (lb/yd / kg/m)65 / 32.50
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)78 / 1981
Boiler Pressure (psi / kPa)220 / 15.20
High Pressure Cylinders (dia x stroke) (in / mm)13" x 26" / 330x660
Low Pressure Cylinders (dia x stroke) (in / mm)21.5" x 26" / 546x660
Tractive Effort (lbs / kg)15,428 / 6998.03
Factor of Adhesion (Weight on Drivers/Tractive Effort) 5.08
Heating Ability
Tubes (number - dia) (in / mm)195 - 2.125" / 54
Flues (number - dia) (in / mm)
Flue/Tube length (ft / m)14.75 / 4.50
Firebox Area (sq ft / m2)153 / 14.21
Grate Area (sq ft / m2)31.70 / 2.95
Evaporative Heating Surface (sq ft / m2)1899 / 176.42
Superheating Surface (sq ft / m2)
Combined Heating Surface (sq ft / m2)1899 / 176.42
Evaporative Heating Surface/Cylinder Volume475.43
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation6974
Same as above plus superheater percentage6974
Same as above but substitute firebox area for grate area33,660
Power L16974
Power MT392.22

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