Southern Pacific class A-6
All A-3 Atlantics built from 1904 onwards were fitted with a superheater from 1920 and most of them also received a feedwater heater and a booster on the trailing axle. Four underwent an even bigger rebuild in the Southern Pacific workshops, resulting in the class A-6. Two each were completed in August 1927 and October 1928.
As opposed to other rebuilds with a driver diameter of 77 inches, the A-6 retained the original 81 inches. In addition, the diameter of the cylinders was increased by two inches and the boiler pressure was increased by ten psi. The tube heating surface has been increased by about five percent and the frame has been strengthened. In total, this resulted in a service mass increased by around 20 tons. Their duties included the haulage of the Sacramento Daylight.
Technical data
General
- Built
- 1927-1928
- Manufacturers
- Sacramento
- Wheel arrangement
- 4-4-2 (Atlantic)
- Gauge
- 1,435 mm (Standard gauge)
Dimensions and weights
- Wheelbase
- 8.74 m
- Total wheelbase
- 23.99 m
- Service mass
- 110.6 t
- Adhesion mass
- 57.5 t
- Total mass
- 189.6 t
- Rigid wheelbase
- 2.13 m
- Axle load
- 29.3 t
Boiler
- Grate area
- 4.599 m²
- Firebox surface
- 16.351 m²
- Tube heating surface
- 197.791 m²
- Evaporative heating surface
- 214.142 m²
- Superheater surface
- 40.413 m²
- Total heating surface
- 254.6 m²
Power plant
- Driver diameter
- 2,057 mm
- Boiler pressure
- 14.5 bar
- Expansion type
- simple expansion
- Cylinders
- two, 559 x 711 mm
Power
- Power source
- steam
- Estimated power
- 1,342 kW (1,825 PS)
- Starting effort
- 132.8 kN
- Starting effort booster
- 51.244 kN
Calculated values
- Factor of adhesion
- 1 : 4.24
- Optimal speed
- 61 km/h
- Power-to-weight ratio
- 12.1 kW/t
- Heating Surface Equivalent
- 376.7 m²
- Cylinder volume/HSE
- 1 : 925.98
- Adhesive weight/Total
- 1 : 1.93
- Tractive force/Heating surface
- 1 : 10.90
- Grate area/Heating surface
- 1 : 55.35
- Firebox/Tube surface
- 1 : 12.10
- Total/Superheater
- 1 : 5.30
