5AT Performance Predictions

The 5AT’s Predicted Performance (based on Wardale’s calculations)

The following summary of the 5AT’s performance capabilities are as stated by David Wardale and derive from his Fundamental Design Calculations for the locomotive:

  • Nominal starting wheel rim tractive effort = 146 kN (32,830 lb), requiring a starting coefficient of adhesion of 0.248.
  • Maximum rated drawbar power on level tangent track = 1890 kW (2535 hp) at 113km/h (71 mph).
  • Maximum indicated cylinder power = 2580 kW (3460 hp) at 170 km/h (106 mph). This equates to 32.3 kW/tonne of engine weight (43.3 hp/ton) assuming an engine weight of 80 tonnes.
  • The power/weight ratios for 5AT-hauled trains is comparable with diesel and electric traction is shown in the diagram (right).
  • Overall thermal efficiency of the locomotive, when oil fired (referring to the cylinder output corresponding to the maximum rated drawbar power) is estimated to be 14.1%.  This will not be the locomotive’s maximum figure.
  • The corresponding indicated specific steam consumption, based on steam to the cylinders only = 1.90 kg/MJ (11.2 lb/hp-h).
  • Maximum continuous operating speed = 180 km/h (112.5 mph). The locomotive will be designed for 10% over-speed, i.e. 200 km/h (125 mph). Note that this is the speed the locomotive will be designed to be capable of, and does not imply that it will be permitted to operate at such a speed. (Refer to the relevant FAQ page on this website).
  • Rated maximum steam supply from the boiler = 17,000 kg/h (37,500 lb/h).
  • Maximum steam temperature = 450°C.
  • Operating range at constant maximum drawbar power (1890 kW at 113 km/h)*:
    Based on fuel supply = 560 km (350 miles)
    Based on water supply = 370 km (230 miles)
  • Operating range under representative average main line service conditions (113 km/h overall average train speed assumed):
    Based on fuel supply = 930 km (580 miles)
    Based on water supply = 620 km (385 miles)

* Note: delivery of 1890 e.d.b. kW at a constant 113km/h implies the haulage of a 1075 ton 29 coach train at this speed on level track. The ranges at both maximum power and under “representative average service conditions” will therefore be greater than given with the trailing loads more likely to be found in actual service which are typically in the range of 300 to 500 tonnes.

The graphical representation comparing the Power-to-Weight ratios of the 5AT + various train lengths with modern traction types, first appeared in Wardale’s article titled “Steaming into the Future” published in the Steam Railway Magazine in June/July 2002.