Western Pacific 2-8-8-2 "Chesapeake" Locomotives in 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 Rail Data Exchange. 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 Wheelbase (ft / m)16.50 / 5.03
Engine Wheelbase (ft / m)61.42 / 18.72
Ratio of driving wheelbase to overall engine wheebase 0.27
Overall Wheelbase (engine & tender) (ft / m)108
Axle Loading (Maximum Weight per Axle) (lbs / kg)69,088 / 31,338
Weight on Drivers (lbs / kg)552,700 / 250,701
Engine Weight (lbs / kg)665,100 / 301,685
Tender Loaded Weight (lbs / kg)408,250 / 185,179
Total Engine and Tender Weight (lbs / kg)1,073,350 / 486,864
Tender Water Capacity (gals / ML)22,000 / 83.33
Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT)6000 / 22.70
Minimum weight of rail (calculated) (lb/yd / kg/m)115 / 57.50
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)63 / 1600
Boiler Pressure (psi / kPa)235 / 16.20
High Pressure Cylinders (dia x stroke) (in / mm)26" x 32" / 660x813 (4)
Tractive Effort (lbs / kg)137,174 / 62221.15
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.03
Heating Ability
Firebox Area (sq ft / m2)739 / 68.68
Grate Area (sq ft / m2)145 / 13.48
Evaporative Heating Surface (sq ft / m2)6811 / 632.99
Superheating Surface (sq ft / m2)2152 / 200
Combined Heating Surface (sq ft / m2)8963 / 832.99
Evaporative Heating Surface/Cylinder Volume173.18
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation34,075
Same as above plus superheater percentage42,253
Same as above but substitute firebox area for grate area215,345
Power L118,743
Power MT598.10