Western Pacific 2-8-8-2 "Chesapeake" Locomotives of the USA

Class Details by Steve Llanso of Sweat House Media

Class M-137 (Locobase 332)

Data from tables in 1947 Locomotive Cyclopedia and WP 2 - 1946 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Raildata collection. See also DeGolyer, Vol 81, pp. 521+ and Vol 82, pp. 344+. Works numbers were 61636-61637, 61641-61642, 61648-61649 in July 1931 and 62149-62152 in 1938.

Ten of these big articulateds were built for the Feather River Canyon route, running the Pacific Fruit Express trains (65-74 cars) through the canyon and up a 1% grade at speeds of 18-25 mph over a distance of 117 miles from Oroville to Portola.

These were oil-fired engines with immense firebox areas. Firebox and combustion chamber had thermic syphons which contributed considerably to the heating surface area; three were in the firebox, two in the combustion chamber. The thermic syphons alone amounted to 217 sq ft (20.15 sq m) and the combustion chamber added another 155 sq ft (14.4 sq m). The boiler was fitted with Worthington No 6 Type S feedwater heater. Four 12" piston valves fed the cylinders.

As good as the class was, the WP soon tested the EMD four-diesel set and plumped for diesels sooner than most other US railroads. As a result, the entire class of M-137s was scrapped in the early 1950s.

Specifications by Steve Llanso of Sweat House Media
Locobase ID332
RailroadWestern Pacific (WP)
Number in Class10
Road Numbers251-260
Number Built10
Valve GearWalschaert
Locomotive Length and Weight
Driver Wheelbase16.50'
Engine Wheelbase61.42'
Ratio of driving wheelbase to overall engine wheebase 0.27
Overall Wheelbase (engine & tender)108'
Axle Loading (Maximum Weight per Axle)69088 lbs
Weight on Drivers552700 lbs
Engine Weight665100 lbs
Tender Light Weight408250 lbs
Total Engine and Tender Weight1073350 lbs
Tender Water Capacity22000 gals
Tender Fuel Capacity (oil/coal)6000 gals
Minimum weight of rail (calculated)115 lb/yard
Geometry Relating to Tractive Effort
Driver Diameter63"
Boiler Pressure235 psi
Cylinders (dia x stroke)26" x 32"
Tractive Effort137174 lbs
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.03
Heating Ability
Firebox Area739 sq. ft
Grate Area145 sq. ft
Evaporative Heating Surface6811 sq. ft
Superheating Surface2152 sq. ft
Combined Heating Surface8963 sq. ft
Evaporative Heating Surface/Cylinder Volume173.18
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation34075
Same as above plus superheater percentage42253
Same as above but substitute firebox area for grate area215345
Power L118743
Power MT598.10



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