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

Class Details by Steve Llanso of Sweat House Media

Class 2 (Locobase 3644)

Data from Wiener (1930) and . See also DeGolyer, Vol 34, p. 299 and Vol 62, pp. 290+. Works numbers were 34215 in January 1910 and 53143 in April 1920.

A Prairie Mallet tank for a logging road and one of three of the wheel arrangement (the other two were tender engines) bought by the company in 1910. Baldwin supplied the second in the class a decade later. One bug addressed in the second engine was the small size of the frame bolts that held the brake rigging and hangers; the #2's "were too small and gave considerable trouble." As was often the case, no amount of stock springing was ever enough and #6 had larger springs under the firebox.

They operated over 26 miles (41.9 km) of 1% to 5% grade over 30-deg curves pulling 385 tons. (The maximum gradient was later reduced to 3.33%.) The tank version was the first tank Mallet built for use in North America. Baldwin's specs included even more stringent requirements, such as the ability to haul 134 tons of trailing load up an 8% (!) grade and negotiate curves of up to 40 degrees over 56-lb/yard (28-kg/metre) rail. The crown sheet was sloped to allow operation on grades of 9% (a rise of 475 ft/144.8 metres in a mile).

Wiener singles out the design, saying "They deserve far more than a mere passing mention, because they were so well thought out and designed that the type has remained unchanged until this [1930] day, except for the adoption of ...superheaters and arch tubes ...which tend to increase efficiency or to reduce maintenance costs." At some point the balloon stack was replaced by a straight pipe. tells us that both remained with Booth-Kelly until 1945 and was scrapped a year later in Wendling, Oregon.

Principal Dimensions by Steve Llanso of Sweat House Media
Locobase ID3644
RailroadBooth-Kelly Lumber Company
Number in Class2
Road Numbers2, 6
Number Built2
Valve GearWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m)8 / 2.44
Engine Wheelbase (ft / m)23.67 / 7.21
Ratio of driving wheelbase to overall engine wheebase 0.34
Overall Wheelbase (engine & tender) (ft / m)23.67 / 7.21
Axle Loading (Maximum Weight per Axle) (lbs / kg)
Weight on Drivers (lbs / kg)177,200 / 80,377
Engine Weight (lbs / kg)205,950 / 93,417
Tender Loaded Weight (lbs / kg)
Total Engine and Tender Weight (lbs / kg)205,950
Tender Water Capacity (gals / ML)2000 / 7.58
Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT)1000 / 3.80
Minimum weight of rail (calculated) (lb/yd / kg/m)49 / 24.50
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)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) 4.72
Heating Ability
Firebox Area (sq ft / m2)132 / 12.27
Grate Area (sq ft / m2)26.30 / 2.44
Evaporative Heating Surface (sq ft / m2)2089 / 194.14
Superheating Surface (sq ft / m2)
Combined Heating Surface (sq ft / m2)2089 / 194.14
Evaporative Heating Surface/Cylinder Volume331.32
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation5260
Same as above plus superheater percentage5260
Same as above but substitute firebox area for grate area26,400
Power L12734
Power MT204.09

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Wes Barris