Broken Hill Proprietary 2-8-2 Locomotives in Australia

Class Details by Steve Llanso of Sweat House Media

Class 6 (Locobase 14736)

Data from Baldwin Locomotive Works Specification for Engines as digitized by the DeGolyer Library of Southern Methodist University, Volume 63, p. 180 and Volume 79, pp. 498. See also Leon Oberg, Locomotives of Australia, 1854 to 2007 (New South Wales: Rosenberg Publishing Pty Ltd, 2007), pp. 174-175. Works numbers were 52694-52695 in December 1919, 60311 in December 1927, and 62232 in April 1938.

These were the first Mikados in Australia and were intended to represent a substantial increase in power for this mineral line. They were, in fact, among the heaviest engines with the biggest boilers and grates of any metre- or Cape-gauge 2-8-2s.

The short-stroke cylinders were supplied with steam through 10" (254 mm) piston valves. Firebox heating surface included 20 sq ft (1.85 sq m) from four arch tubes. The short wheelbase aided in meeting the requirement to pass curves with radii as low as 660 feet (201 metres). Loaded trains faced adverse 1 1/4% grades that ran 1 1/2 miles (2.4 km) and 1.6% grades that ran for 1/2 mile (0.8 km). Desired speed was 30 mph (48 km/h).

Although Oberg states that the #8 was 11 tonnes lighter than the earlier engines, the specifications gave exactly the same weights in 1927 as in 1919. Indeed, the general description of this engine was that it was a duplicate of the earlier two.

Oberg comments that the desired train loading was 660 tonnes (726 short tons), but that these Mikes each managed over 2,600 tons in trials and, in at least one instance in 1937, a train double-headed by two of this class out of Iron Knob mine totalled 3,838 tonnes (4,222 short tons).

Two decades later, the introduction of diesels spelled the rapid end of this class with the 7 being last to retire in 1958.

Principal Dimensions by Steve Llanso of Sweat House Media

Locobase ID14736
RailroadBroken Hill Proprietary
Number in Class4
Road Numbers6-9
Number Built4
Valve GearWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m)13.75 / 4.19
Engine Wheelbase (ft / m)30.92 / 9.42
Ratio of driving wheelbase to overall engine wheelbase 0.44
Overall Wheelbase (engine & tender) (ft / m)59.40 / 18.11
Axle Loading (Maximum Weight per Axle) (lbs / kg)
Weight on Drivers (lbs / kg)156,000 / 70,760
Engine Weight (lbs / kg)183,000 / 83,008
Tender Loaded Weight (lbs / kg)130,000 / 58,967
Total Engine and Tender Weight (lbs / kg)313,000 / 141,975
Tender Water Capacity (gals / ML)6500 / 24.62
Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT)10.10 / 9
Minimum weight of rail (calculated) (lb/yd / kg/m)65 / 32.50
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)48 / 1219
Boiler Pressure (psi / kPa)200 / 13.80
High Pressure Cylinders (dia x stroke) (in / mm)21" x 24" / 533x610
Tractive Effort (lbs / kg)37,485 / 17002.93
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.16
Heating Ability
Tubes (number - dia) (in / mm)161 - 2" / 51
Flues (number - dia) (in / mm)26 - 5.375" / 137
Flue/Tube length (ft / m)17.67 / 5.39
Firebox Area (sq ft / m2)161 / 14.96
Grate Area (sq ft / m2)41.30 / 3.84
Evaporative Heating Surface (sq ft / m2)2286 / 212.37
Superheating Surface (sq ft / m2)562 / 52.21
Combined Heating Surface (sq ft / m2)2848 / 264.58
Evaporative Heating Surface/Cylinder Volume237.60
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation8260
Same as above plus superheater percentage9912
Same as above but substitute firebox area for grate area38,640
Power L113,552
Power MT766.08

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