These locomotives were designed with 75" drivers, 26 x 32 cylinders, a 270 psi boiler pressure, a weight of 445,550 pounds and had a tractive effort of 66,000 pounds.
There are no survivors.
Classic Northern from the late 1930s that carried its boiler and firebox on an frame that was integrally cast with both the cylinders and the air reservoirs. Piston valves measured a modest 12" (306 mm) in diameter. The Elesco Type E superheater included a dryer. In place of the commonly adopted feed water heaters, the O-20s used an Elesco Type SL-305 exhaust steam injector.
Drury (1993) says of these engines: "Assigned to fast Chicago-Twin Cities freight trains, [they] acquired a reputation for availability -- they were able to turn at the terminals and be on their way quickly."
NB: The superheater area in the specs is an estimate. It is a calculation based on taking the diagram value of 2,120 sq ft of "superheater equivalent" and deducting a third from it. See the logic presented in Locobase 1364.
|Specifications by Steve Llanso of Sweat House Media|
|Railroad||Minneapolis, St Paul & Sault Ste Marie (Soo)|
|Number in Class||4|
|Locomotive Length and Weight|
|Driver Wheelbase (ft)||19.75|
|Engine Wheelbase (ft)||46.75|
|Ratio of driving wheelbase to overall engine wheebase||0.42|
|Overall Wheelbase (engine & tender) (ft)||87.47|
|Axle Loading (Maximum Weight per Axle) (lbs)||65,900|
|Weight on Drivers (lbs)||263,000|
|Engine Weight (lbs)||445,550|
|Tender Loaded Weight (lbs)||317,600|
|Total Engine and Tender Weight (lbs)||763,150|
|Tender Water Capacity (gals)||17,500|
|Tender Fuel Capacity (oil/coal) (gals/tons)||24|
|Minimum weight of rail (calculated) (lb/yd)||110|
|Geometry Relating to Tractive Effort|
|Driver Diameter (in)||75|
|Boiler Pressure (psi)||275|
|High Pressure Cylinders (dia x stroke) (in)||26" x 32"|
|Tractive Effort (lbs)||67,420|
|Factor of Adhesion (Weight on Drivers/Tractive Effort)||3.90|
|Firebox Area (sq ft)||423|
|Grate Area (sq ft)||88.30|
|Evaporative Heating Surface (sq ft)||5142|
|Superheating Surface (sq ft)||1413|
|Combined Heating Surface (sq ft)||6555|
|Evaporative Heating Surface/Cylinder Volume||261.49|
|Computations Relating to Power Output (More Information)|
|Robert LeMassena's Power Computation||24,283|
|Same as above plus superheater percentage||29,625|
|Same as above but substitute firebox area for grate area||141,917|