Central Pacific 2-6-2 "Prairie" Locomotives in the USA

Class Details by Steve Llanso of Sweat House Media

Class S-1 (Locobase 2846)

Data from "Tank Locomotive; Central Pacific Railroad", Engineering, Volume 34 This (18 August 1882), p. 155.

Master Mechanic AJ Stevens designed this engine for the heavy suburban traffic out of Oakland and Alameda, Calif. Engineering reported that the route was short (3 to 8 miles) from the end of the ferry wharf some two miles into San Francisco Bay. But morning and evening trains were "very heavy and make frequent stops." Note the very high factor of adhesion, which suggests an underexploited boiler.

[] (visited 6 January 2005), this class of little tanks operated into the 'Teens. One (335, works #18) was sold to the Tidewater Southern in 1912, which operated it between Modesto and the Stanilaus River and later to Stockton until the TS was electrified. At that point, the TS sold it to the Howard Terminal in Oakland in 1917.

Principal Dimensions by Steve Llanso of Sweat House Media
Locobase ID2846
RailroadCentral Pacific
Number in Class7
Road Numbers230-236
Number Built7
BuilderCentral Pacific
Valve GearStephenson
Locomotive Length and Weight
Driver Wheelbase (ft / m)14 / 4.27
Engine Wheelbase (ft / m)28 / 8.53
Ratio of driving wheelbase to overall engine wheebase 0.50
Overall Wheelbase (engine & tender) (ft / m)28
Axle Loading (Maximum Weight per Axle) (lbs / kg)
Weight on Drivers (lbs / kg)80,400 / 36,469
Engine Weight (lbs / kg)104,100 / 47,219
Tender Loaded Weight (lbs / kg)
Total Engine and Tender Weight (lbs / kg)104,100
Tender Water Capacity (gals / ML)1280 / 6.06
Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT)4 / 3.60
Minimum weight of rail (calculated) (lb/yd / kg/m)45 / 22.50
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)50 / 1295
Boiler Pressure (psi / kPa)125 / 10
High Pressure Cylinders (dia x stroke) (in / mm)16" x 24" / 406x610
Tractive Effort (lbs / kg)13,056 / 5922.11
Factor of Adhesion (Weight on Drivers/Tractive Effort) 6.16
Heating Ability
Firebox Area (sq ft / m2)88
Grate Area (sq ft / m2)14.70
Evaporative Heating Surface (sq ft / m2)929
Superheating Surface (sq ft / m2)
Combined Heating Surface (sq ft / m2)929
Evaporative Heating Surface/Cylinder Volume166.34
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation1838
Same as above plus superheater percentage1838
Same as above but substitute firebox area for grate area11,000
Power L12553
Power MT210.01

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