Crown Willamette Paper Co. 2-6-6-2 "Mallet Mogul" Locomotives in the USA

Class Details by Steve Llanso of Sweat House Media

Class 12 (Locobase 4055)

Data from Jon Davis's, supplemented by DeGolyer, Vol 80, pp. 266+. Works number was 60771 in April 1929.

One of several Prairie Mallet tanks built by Baldwin for Northwest logging roads with split saddle tank (called "semi-saddle" in the specifications). Like most of the other tanks of this layout, the HP valves were supplied through 8" (203 mm) piston valves, the LP cylinders through 12" (305 mm) piston valves.

12 worked for 35 years for the same company out of Cathlamet, Wash. She was scrapped after her 1959 retirement.

Principal Dimensions by Steve Llanso of Sweat House Media
Locobase ID4055
RailroadCrown Willamette Paper Co.
Number in Class1
Road Numbers12
Number Built1
Valve GearWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m)8 / 2.44
Engine Wheelbase (ft / m)37.25 / 11.35
Ratio of driving wheelbase to overall engine wheebase 0.21
Overall Wheelbase (engine & tender) (ft / m)37.25 / 11.35
Axle Loading (Maximum Weight per Axle) (lbs / kg)
Weight on Drivers (lbs / kg)183,000 / 83,008
Engine Weight (lbs / kg)222,000 / 100,698
Tender Loaded Weight (lbs / kg)
Total Engine and Tender Weight (lbs / kg)222,000
Tender Water Capacity (gals / ML)2500 / 9.47
Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT)1200 / 4.50
Minimum weight of rail (calculated) (lb/yd / kg/m)51 / 25.50
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)16" x 24" / 406x610
Low Pressure Cylinders (dia x stroke) (in / mm)26" x 24" / 660x610
Tractive Effort (lbs / kg)34,436 / 15619.93
Factor of Adhesion (Weight on Drivers/Tractive Effort) 5.31
Heating Ability
Firebox Area (sq ft / m2)128 / 11.89
Grate Area (sq ft / m2)26.20 / 2.43
Evaporative Heating Surface (sq ft / m2)1654 / 153.66
Superheating Surface (sq ft / m2)358 / 33.26
Combined Heating Surface (sq ft / m2)2012 / 186.92
Evaporative Heating Surface/Cylinder Volume296.15
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 area30,208
Power L15486
Power MT396.54

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