Portland & Southwestern 2-6-6-2 Locomotives of the USA

Class Details by Steve Llanso of Sweat House Media

Class 2 (Locobase 4059)

Data from Jon Davis's loggingmallets.railfan.net/list/prtlnd2/portland2.htm, a logging locomotive website last accessed 19 May 2006 as well as Baldwin Locomotive's Record of Recent Construction 57 -- Oil-Burning Locomotives (1911), 29. Works number was 34785 in December 1910.

Running under Chapman Timber oversight, this engine operated out of Scapoose for only eight years. She then went to the Alton & Southern (in East St Louis, Ill.).

Davis's account pays special attention to the Baldwin "separable boiler" in a description that outdoes others in clarity. The rear part of the boiler had the firetubes common to all "Stephenson" boilers, although these were uncommonly short. The front half of the barrel had two bundles of tubes. In the back part of the front half (still with me?) rested a flue-gas feed water heater offering a total of 1,006 sq ft of surface to heat incoming tender water. A reheater in the smokebox (the 421 sq ft attributed to the "superheater" in the specs) was an intermediate point in the cycle where the exhausting steam from the HP cylinders was reheated before entering the LP cylinders.

Baldwin promoted this concept extensively for a few years, but almost all such Mallets were rebuilt with a standard boiler within a few years. Remarkably, this lone logger seems to have kept its oddly laid out boiler until it was scrapped.

Specifications by Steve Llanso of Sweat House Media
Locobase ID4059
RailroadPortland & Southwestern
Number in Class1
Road Numbers2
Number Built1
Valve GearWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft)9
Engine Wheelbase (ft)26.75
Ratio of driving wheelbase to overall engine wheebase 0.34
Overall Wheelbase (engine & tender) (ft)42
Axle Loading (Maximum Weight per Axle) (lbs)
Weight on Drivers (lbs)204,500
Engine Weight (lbs)235,300
Tender Loaded Weight (lbs)99,700
Total Engine and Tender Weight (lbs)335,000
Tender Water Capacity (gals)5000
Tender Fuel Capacity (oil/coal) (gals/tons)2000
Minimum weight of rail (calculated) (lb/yd)57
Geometry Relating to Tractive Effort
Driver Diameter (in)51
Boiler Pressure (psi)200
High Pressure Cylinders (dia x stroke) (in)18.5" x 28"
Low Pressure Cylinders (dia x stroke) (in)28" x 28"
Tractive Effort (lbs)44,472
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.60
Heating Ability
Firebox Area (sq ft)148
Grate Area (sq ft)41.80
Evaporative Heating Surface (sq ft)2904
Superheating Surface (sq ft)421
Combined Heating Surface (sq ft)3325
Evaporative Heating Surface/Cylinder Volume333.36
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation8360
Same as above plus superheater percentage9447
Same as above but substitute firebox area for grate area33,448
Power L16332
Power MT409.57

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