Spokane, Portland & Seattle 4-6-2 "Pacific" Locomotives in the USA

Class Details by Steve Llanso of Sweat House Media

Class H-1 (Locobase 8846)

Data from SP&S 2 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange.

Originally delivered to the SP & S as redirected E-14 Ten-wheelers from the Great Northern (one of two SP & S owners), these engines underwent signficant changes in the 1920s. The design followed that of the Great Northern's H-5/H-7 rebuild (Locobase 6450). Total heating surface in the boiler remained about the same, but the percentage of superheater area rose considerably. Also, the boiler was lengthened by 42" and the Belpaire firebox gained a combustion chamber.

Principal Dimensions by Steve Llanso of Sweat House Media
Locobase ID8846
RailroadSpokane, Portland & Seattle
Number in Class6
Road Numbers620-625
Number Built
Valve GearWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m)13.50 / 4.11
Engine Wheelbase (ft / m)36.96 / 11.27
Ratio of driving wheelbase to overall engine wheebase 0.37
Overall Wheelbase (engine & tender) (ft / m)75.11 / 22.89
Axle Loading (Maximum Weight per Axle) (lbs / kg)55,500 / 25,174
Weight on Drivers (lbs / kg)166,500 / 75,523
Engine Weight (lbs / kg)283,400 / 128,548
Tender Loaded Weight (lbs / kg)252,700 / 114,623
Total Engine and Tender Weight (lbs / kg)536,100 / 243,171
Tender Water Capacity (gals / ML)18,000 / 68.18
Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT)4950 / 18.80
Minimum weight of rail (calculated) (lb/yd / kg/m)93 / 46.50
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)73 / 1854
Boiler Pressure (psi / kPa)210 / 14.50
High Pressure Cylinders (dia x stroke) (in / mm)23.5" x 30" / 597x762
Tractive Effort (lbs / kg)40,511 / 18375.50
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.11
Heating Ability
Firebox Area (sq ft / m2)272 / 25.28
Grate Area (sq ft / m2)55 / 5.11
Evaporative Heating Surface (sq ft / m2)3157 / 293.40
Superheating Surface (sq ft / m2)774 / 71.93
Combined Heating Surface (sq ft / m2)3931 / 365.33
Evaporative Heating Surface/Cylinder Volume209.62
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation11,550
Same as above plus superheater percentage13,860
Same as above but substitute firebox area for grate area68,544
Power L119,481
Power MT773.84

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