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|
|Railroad||Western Pacific (WP)|
|Number in Class||10|
|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|
|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 Volume||173.18|
|Computations Relating to Power Output (More Information)|
|Robert LeMassena's Power Computation||34,075|
|Same as above plus superheater percentage||42,253|
|Same as above but substitute firebox area for grate area||215,345|