Simpson Logging Co 2-6-6-2 "Mallet Mogul" Locomotives in the USA

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Class Details by Steve Llanso of Sweat House Media

Class Sophus Jacobson (Locobase 4062)

Data from, supplemented by DeGolyer, Vol 80, pp. 298+. Works number was 59173 in May 1926.

Split saddle-tanker served Simpson Logging on their Peninsular Railway in Shelton, Wash, where the specifications indicated a maximum grade of 5% (or "possibly 6%") on 60 lb/yard (30 kg/metre) rail around 30 degree (193 foot/59 metre radii).

Like the other Baldwin 2-6-6-2 tanks, all four of 13's cylinders were served by piston valves--8" (203 mm) diameter for HP, 12" (306 mm) for the LP cylinders.

The 13 put in 30 years beforel her retirement in 1956, after which she was scrapped.

Specifications by Steve Llanso of Sweat House Media
ClassSophus Jacobson
Locobase ID4062
RailroadSimpson Logging Co
Number in Class1
Road Numbers13
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)200,000 / 90,719
Engine Weight (lbs / kg)238,000 / 107,955
Tender Loaded Weight (lbs / kg)
Total Engine and Tender Weight (lbs / kg)238,000
Tender Water Capacity (gals / ML)2500 / 9.47
Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT)1000 / 3.80
Minimum weight of rail (calculated) (lb/yd / kg/m)56 / 28
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)18" x 24" / 457x610
Low Pressure Cylinders (dia x stroke) (in / mm)28" x 24" / 711x610
Tractive Effort (lbs / kg)42,517 / 19285.41
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.70
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 Volume233.99
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 L14730
Power MT312.84