South Australian Railways 2-8-4 Locomotives in Australia


Class Details by Steve Llanso of Sweat House Media

Class 720B (Locobase 5688)

Data from Douglas Colquhoun's entries presented in the Australian national railway museum site: [] (visited 14 October 2003). See also [], last accessed 8 March 2015.

The only "Berkshires" in Australian service, these were enlargements of the "Mighty 700s". Five were delivered in 1930-1931, Three each in 1938, 1939, 1942, and 1943. Before the class's retirement in 1958-1960, the least-used of the class had accumulated 411,097 miles in service. Of those delivered in the early 1930s, the class leader covered 729,376 miles before its 14 April 1960 withdrawal.

Principal Dimensions by Steve Llanso of Sweat House Media

Class720B
Locobase ID5688
RailroadSouth Australian Railways
CountryAustralia
Whyte2-8-4
Number in Class17
Road Numbers720-736
Gauge5'3"
Number Built17
BuilderIslington
Year1930
Valve GearWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m)15.50 / 4.72
Engine Wheelbase (ft / m)37.08 / 11.30
Ratio of driving wheelbase to overall engine wheelbase 0.42
Overall Wheelbase (engine & tender) (ft / m)73.25 / 22.33
Axle Loading (Maximum Weight per Axle) (lbs / kg)44,454 / 20,164
Weight on Drivers (lbs / kg)172,704 / 78,337
Engine Weight (lbs / kg)277,312 / 125,787
Tender Loaded Weight (lbs / kg)232,960 / 105,669
Total Engine and Tender Weight (lbs / kg)510,272 / 231,456
Tender Water Capacity (gals / ML)10,800 / 40.91
Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT)19 / 17
Minimum weight of rail (calculated) (lb/yd / kg/m)72 / 36
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)57 / 1448
Boiler Pressure (psi / kPa)220 / 15.20
High Pressure Cylinders (dia x stroke) (in / mm)22" x 28" / 559x711
Tractive Effort (lbs / kg)44,460 / 20166.74
Factor of Adhesion (Weight on Drivers/Tractive Effort) 3.88
Heating Ability
Tubes (number - dia) (in / mm)
Flues (number - dia) (in / mm)
Flue/Tube length (ft / m)
Firebox Area (sq ft / m2)360 / 33.46
Grate Area (sq ft / m2)46.80 / 4.35
Evaporative Heating Surface (sq ft / m2)2975 / 276.49
Superheating Surface (sq ft / m2)751 / 69.80
Combined Heating Surface (sq ft / m2)3726 / 346.29
Evaporative Heating Surface/Cylinder Volume241.49
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation10,296
Same as above plus superheater percentage12,355
Same as above but substitute firebox area for grate area95,040
Power L119,568
Power MT999.17

All material Copyright © SteamLocomotive.com
Wes Barris