Minneapolis, St Paul & Sault Ste Marie 4-8-4 "Northern" Locomotives of the USA

The Minneapolis, St. Paul & Sault Sainte Marie Railroad purchased four Class O-20, 4-8-4s in 1938 from the Lima Locomotive Works. They were given road numbers 5000 through 5003 and were assigned to both freight and passenger trains.

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.

Class Details by Steve Llanso of Sweat House Media

Class O-20 (Locobase 278)

Data from Soo 1942 Locomotive Diagrams supplied in August 2013 by Allen Stanley from his extensive Raildata collection. Works numbers were 7753-7756 in January 1938.

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
Locobase ID278
RailroadMinneapolis, St Paul & Sault Ste Marie (Soo)
Number in Class4
Road Numbers5000-5003
Number Built4
Valve GearWalschaert
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
Heating Ability
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 Volume261.49
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation24,283
Same as above plus superheater percentage29,625
Same as above but substitute firebox area for grate area141,917
Power L134,917
Power MT1170.78


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