Spokane, Portland & Seattle 4-4-2 "Atlantic" Locomotives of the USA

Class Details by Steve Llanso of Sweat House Media

Class K / C-1 (Locobase 13332)

Data from DeGolyer, Volume 32, p. 39. Works numbers were 33228-33233 in February 1909; 33273-33276 in March.

Each big 15" piston valve fed both cylinders on one side of the 4-cylinder battery under this balanced compound Atlantic. Based on the Great Northern compounds of 1906 (Locobase 6945), the SP & S engines arrived 3 years later. They had the GN-signature Belpaire fireboxes.

Drury (1993) says they were the "mainstay" of the SP & S express passenger service for years. In 1923, they were converted to simple-expansion locomotives identical to the Great Northern rebuilds shown in Locobase 6944.

Specifications by Steve Llanso of Sweat House Media
ClassK / C-1
Locobase ID13,332
RailroadSpokane, Portland & Seattle
Number in Class10
Road Numbers600-609
Number Built10
BuilderBurnham, Williams & Co
Valve GearWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft) 7.12
Engine Wheelbase (ft)30.42
Ratio of driving wheelbase to overall engine wheebase 0.23
Overall Wheelbase (engine & tender) (ft)63.48
Axle Loading (Maximum Weight per Axle) (lbs)50,000
Weight on Drivers (lbs)100,000
Engine Weight (lbs)208,000
Tender Loaded Weight (lbs)148,200
Total Engine and Tender Weight (lbs)356,200
Tender Water Capacity (gals)8000
Tender Fuel Capacity (oil/coal) (gals/tons)3000
Minimum weight of rail (calculated) (lb/yd)83
Geometry Relating to Tractive Effort
Driver Diameter (in)73
Boiler Pressure (psi)210
High Pressure Cylinders (dia x stroke) (in)15" x 26"
Low Pressure Cylinders (dia x stroke) (in)25" x 26"
Tractive Effort (lbs)21,036
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.75
Heating Ability
Firebox Area (sq ft)210.77
Grate Area (sq ft)54.15
Evaporative Heating Surface (sq ft)3489
Superheating Surface (sq ft)
Combined Heating Surface (sq ft)3489
Evaporative Heating Surface/Cylinder Volume656.10
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation11,372
Same as above plus superheater percentage11,372
Same as above but substitute firebox area for grate area44,262
Power L17858
Power MT346.48


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