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 "Western Pacific Operating 2-8-8-2 Type in Fast Freight Service", Railway Age, Volume 91, No 26 (26 December 1931), pp. 975-976; DeGolyer, Volumes 81, pp. 521+ and 82, pp. 344+; and "Locomotive Feed Water Heaters,", Boiler Maker, Volume 22, No 10 (October 1922), pp. 292-294. 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. The WP had been using two 2-6-6-2s, a 2-6-6-2 and a 2-8-2, or a double-headed set of 2-8-8-2 and 2-8-0 locomotives.

These were oil-fired engines with immense firebox areas. Firebox and combustion chamber had Nicholson 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).

When delivered, two of the boilers were fitted with Worthington No 6 Type S open-system feedwater heater and four used the Elesco Type K-60 closed-system. Four 12" (305 mm) piston valves fed the cylinders. A report in the Boiler Maker in 1922 discussed "one of the most important considerations" when choosing between Worthington's open system, where the hot steam was blended directly with the incoming water, and the closed system of Elesco and Coffin, which passed the feed water through a tube in the center of a steam-filled chamber. In bad water districts, said the report, the closed type heater built up scale on the tubes that would "retard the heat transmitted and reduce the efficiency of the heater." One clear result from the difference was that the Worthington could from shopping to shopping without being cleaned.

The RA article reported that preliminary tests showed that one M-137 could handle trains of similar tonnage to the earlier consists and with approximately the same fuel consumption".

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.

Principal Dimensions 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)33 / 10.06
Engine Wheelbase (ft / m)61.42 / 18.72
Ratio of driving wheelbase to overall engine wheelbase 0.54
Overall Wheelbase (engine & tender) (ft / m)108 / 32.92
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 / Liters/MT)6000 / 22,710
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
Tubes (number - dia) (in / mm)270 - 2.25" / 57
Flues (number - dia) (in / mm)75 - 5.5" / 140
Flue/Tube length (ft / m)23 / 7.01
Firebox Area (sq ft / m2)739 / 68.66
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 L118,742
Power MT598.07

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