Potlatch Lumber Company 2-6-6-2 "Mallet Mogul" Locomotives in the USA

Class Details by Steve Llanso of Sweat House Media

Class 24 (Locobase 4060)

Data from http://loggingmallets.railfan.net, supplemented by DeGolyer, Vol 80, pp. 248+ Works number was 59087 in March 1926.

One of several Prairie Mallet tanks built by Baldwin for Northwest logging roads. This full saddle-tanker was delivered to its Idaho operator as a coal burner (using bituminous eggnut Montana round-up coal, according to the specs), but was later converted to oil-burning. Its crown sheet was to be sloped to account for an 8% adverse grade. Rail weight remained at 60 lb/yard (30 kg/metre). HP cylinders were supplied through 8" (203 mm) piston valves, while 12" (305 mm) piston valves fed the LP cylinders.

24 had a cabbage stack for a time while with Potlatch, but it had been removed by the time the engine was sold to Weyerhaeuser in 1931 as #108, where she served first at Elk River, Ida., later at Longview, Wash.

Principal Dimensions by Steve Llanso of Sweat House Media
Locobase ID4060
RailroadPotlatch Lumber Company
Number in Class1
Road Numbers24 / 108
Number Built1
Valve GearWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m)8 / 2.44
Engine Wheelbase (ft / m)37.75 / 11.51
Ratio of driving wheelbase to overall engine wheebase 0.21
Overall Wheelbase (engine & tender) (ft / m)37.75 / 11.51
Axle Loading (Maximum Weight per Axle) (lbs / kg)
Weight on Drivers (lbs / kg)193,000
Engine Weight (lbs / kg)226,000 / 102,512
Tender Loaded Weight (lbs / kg)
Total Engine and Tender Weight (lbs / kg)226,000
Tender Water Capacity (gals / ML)2500 / 9.47
Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT)4 / 3.60
Minimum weight of rail (calculated) (lb/yd / kg/m)54 / 27
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)44 / 1118
Boiler Pressure (psi / kPa)200 / 13.80
High Pressure Cylinders (dia x stroke) (in / mm)17" x 24" / 432x610
Low Pressure Cylinders (dia x stroke) (in / mm)26" x 24" / 660x610
Tractive Effort (lbs / kg)37,545 / 17030.15
Factor of Adhesion (Weight on Drivers/Tractive Effort) 5.14
Heating Ability
Firebox Area (sq ft / m2)127.40 / 11.89
Grate Area (sq ft / m2)26.20 / 2.43
Evaporative Heating Surface (sq ft / m2)1653 / 153.66
Superheating Surface (sq ft / m2)358 / 33.26
Combined Heating Surface (sq ft / m2)2011 / 186.92
Evaporative Heating Surface/Cylinder Volume262.17
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation5240
Same as above plus superheater percentage6183
Same as above but substitute firebox area for grate area30,066
Power L15482
Power MT375.72

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