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.
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.
|Specifications by Steve Llanso of Sweat House Media|
|Railroad||Southern Pacific (SP)|
|Number in Class||12|
|Locomotive Length and Weight|
|Ratio of driving wheelbase to overall engine wheebase||0.26|
|Overall Wheelbase (engine & tender)|
|Axle Loading (Maximum Weight per Axle)||66400 lbs|
|Weight on Drivers||522200 lbs|
|Engine Weight||677200 lbs|
|Tender Light Weight||320800 lbs|
|Total Engine and Tender Weight||998000 lbs|
|Tender Water Capacity||22100 gals|
|Tender Fuel Capacity (oil/coal)||28 tons|
|Minimum weight of rail (calculated)||109 lb/yard|
|Geometry Relating to Tractive Effort|
|Boiler Pressure||250 psi|
|Cylinders (dia x stroke)||24" x 32"|
|Tractive Effort||123364 lbs|
|Factor of Adhesion (Weight on Drivers/Tractive Effort)||4.23|
|Firebox Area||589 sq. ft|
|Grate Area||139.50 sq. ft|
|Evaporative Heating Surface||6918 sq. ft|
|Superheating Surface||2831 sq. ft|
|Combined Heating Surface||9749 sq. ft|
|Evaporative Heating Surface/Cylinder Volume||206.44|
|Computations Relating to Power Output (More Information)|
|Robert LeMassena's Power Computation||34875|
|Same as above plus superheater percentage||44989|
|Same as above but substitute firebox area for grate area||189953|