Firebox heating surface included 124 sq ft (11.5 sq m) in seven circulators and several arch tubes.
Conventionally laid-out articulated locomotive for service on the El Paso-Tucumcari section, which didn't require the cab-forward arrangement. Unusually for an Espee locomotive, these were soft-coal burners until they were converted to oil-burning in 1950.
They were essentially "turned-around" cab forwards in which all of the wheelbases remained the same except for the four-wheel truck under the firebox used larger wheels (45" vs 33") that were more closely spaced. At least some of the class were equipped with Hancock size TA2 turbo-feed water heater.
These were fitted with an air-smoothed casing similar to those on the GS-4 4-8-4 passenger locomotives (without the colors). The "raciness" of the profile was not belied by performance--AC-9s were designed to reach 75 mph (119 km/h).
After the Southwest routes were dieselized (in part because of the difficulty in supplying sufficient quantities of good water for steam locomotives), the oil-burning AC-9s operated on the Modoc line in California. Retirements in 1953-1956.
|Principal Dimensions by Steve Llanso of Sweat House Media|
|Railroad||Southern Pacific (SP)|
|Number in Class||12|
|Locomotive Length and Weight|
|Driver Wheelbase (ft / m)||16.92 / 5.16|
|Engine Wheelbase (ft / m)||66.25 / 20.19|
|Ratio of driving wheelbase to overall engine wheebase||0.26|
|Overall Wheelbase (engine & tender) (ft / m)|
|Axle Loading (Maximum Weight per Axle) (lbs / kg)||66,400 / 30,119|
|Weight on Drivers (lbs / kg)||522,200 / 236,866|
|Engine Weight (lbs / kg)||677,200 / 307,173|
|Tender Loaded Weight (lbs / kg)||320,800 / 145,513|
|Total Engine and Tender Weight (lbs / kg)||998,000 / 452,686|
|Tender Water Capacity (gals / ML)||22,100 / 83.71|
|Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT)||28 / 25.50|
|Minimum weight of rail (calculated) (lb/yd / kg/m)||109 / 54.50|
|Geometry Relating to Tractive Effort|
|Driver Diameter (in / mm)||63.50 / 1613|
|Boiler Pressure (psi / kPa)||250 / 17.20|
|High Pressure Cylinders (dia x stroke) (in / mm)||24" x 32" / 610x813 (4)|
|Tractive Effort (lbs / kg)||123,364 / 55957.04|
|Factor of Adhesion (Weight on Drivers/Tractive Effort)||4.23|
|Firebox Area (sq ft / m2)||589 / 54.74|
|Grate Area (sq ft / m2)||139.50 / 12.96|
|Evaporative Heating Surface (sq ft / m2)||6918 / 642.94|
|Superheating Surface (sq ft / m2)||2831 / 263.10|
|Combined Heating Surface (sq ft / m2)||9749 / 906.04|
|Evaporative Heating Surface/Cylinder Volume||206.44|
|Computations Relating to Power Output (More Information)|
|Robert LeMassena's Power Computation||34,875|
|Same as above plus superheater percentage||44,989|
|Same as above but substitute firebox area for grate area||189,953|