Firebox and combustion chamber had thermic syphons which contributed considerably to the heating surface area. The thermic syphons alone amounted to 217 sq ft and the combustion chamber added another 155 sq ft. The boiler fitted with feedwater heater.
10 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 large grate areas. Baldwin delivered the first 6 in 1931, the last 4 in 1938.
| Specifications | |
|---|---|
| Class | M-137 |
| Locobase ID | 332 |
| Railroad | Western Pacific (WP) |
| Whyte | 2-8-8-2 |
| Road Numbers | 251-260 |
| Gauge | Std |
| Builder | Baldwin |
| Year | 1931 |
| Valve Gear | Walschaert |
| Locomotive Length and Weight | |
| Driver Wheelbase | 16.50' |
| Engine Wheelbase | 61.42' |
| Ratio of driving wheelbase to overall engine wheebase | 0.27 |
| Overall Wheelbase (engine & tender) | |
| Axle Loading (Maximum Weight per Axle) | 69088 lbs |
| Weight on Drivers | 552700 lbs |
| Engine Weight | 665100 lbs |
| Tender Light Weight | 408250 lbs |
| Total Engine and Tender Weight | 1073350 lbs |
| Tender Water Capacity | 22000 gals |
| Tender Fuel Capacity (oil/coal) | 6000 gals |
| Minimum weight per yard of rail on which locomotive could run | 115.15 lb rail |
| Geometry Relating to Tractive Effort | |
| Driver Diameter | 63" |
| Boiler Pressure | 235 psi |
| Cylinders (dia x stroke) | 26" x 32" (4) |
| Tractive Effort | 137174 lbs |
| Factor of Adhesion (Weight on Drivers/Tractive Effort) | 4.03 |
| Heating Ability | |
| Firebox Area | 739 sq. ft |
| Grate Area | 145 sq. ft |
| Evaporative Heating Surface | 6811 |
| Superheating Surface | 2152 |
| Combined Heating Surface | 8963 |
| Evaporative Heating Surface/Cylinder Volume | 173.18 |
| Computations Relating to Power Output (More Information) | |
| Robert LeMassena's Power Computation | 34075 |
| Same as above plus superheater percentage | 42256.35 |
| Same as above but substitute firebox area for grate area | 215361.65 |
| Power L1 | 18743.37 |
| Power MT | 598.11 |
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