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. The 1951 diagram states that the class were equipped with Worthington 4-B feed water heaters.
Note: Unusually, the Lima table gives a significantly higher adhesion and engine weights than is found in SP locomotive diagrams of a later date. Adhesion weight on the later SP diagram comes in at 522,120 lb, 4 1/2 short tons lighter than the Lima figure and the engine's weight appears as 677,200 lb (307,173 kg) or 12,700 lb (5,761 kg) less. On the other hand, Lima's tender weights are repeated on page 222-R-1 of Menke's Southern Pacific All Time Tender Diagrams collection.
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)||112.99 / 34.44|
|Axle Loading (Maximum Weight per Axle) (lbs / kg)||66,400 / 30,119|
|Weight on Drivers (lbs / kg)||531,200 / 240,949|
|Engine Weight (lbs / kg)||689,900 / 312,934|
|Tender Loaded Weight (lbs / kg)||400,700 / 181,755|
|Total Engine and Tender Weight (lbs / kg)||1,090,600 / 494,689|
|Tender Water Capacity (gals / ML)||22,120 / 83.79|
|Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT)||28 / 25.50|
|Minimum weight of rail (calculated) (lb/yd / kg/m)||111 / 55.50|
|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)||4.31|
|Firebox Area (sq ft / m2)||589 / 54.72|
|Grate Area (sq ft / m2)||139.50 / 12.96|
|Evaporative Heating Surface (sq ft / m2)||6918 / 642.70|
|Superheating Surface (sq ft / m2)||2831 / 263.01|
|Combined Heating Surface (sq ft / m2)||9749 / 905.71|
|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|