Minneapolis, St Paul & Sault Ste Marie 4-8-2 "Mountain" Type Locomotives

Class N-20 (Locobase 226)

Updated versions of the USRA Mountain that, says Drury (1993), were meant to speed up freight service to offset the competitive disadvantages of a longer route between Chicago and Minneapolis that was single-tracked most of the way. Brooks produced the first 10, Schenectady the next 8, and the Soo itself the last 3.

Note that the superheater area in the specs is estimated. It is a calculation based on taking the diagram value of 1,650 sq ft of "superheater equivalent" and deducting a third from it. See the logic presented in Locobase 1364. Also note that in this particular class, the 1,103 sq ft shown in the specs is taken directly from a 1930 Locomotive Cyclopedia table, which strengthens the case for the adjustment.

Specifications
ClassN-20
Locobase ID226
RailroadMinneapolis, St Paul & Sault Ste Marie (Soo)
Whyte4-8-2
Road Numbers4000-4020
GaugeStd
Builderseveral
Year1928
Valve GearBaker
Locomotive Length and Weight
Driver Wheelbase18.25'
Engine Wheelbase40.83'
Ratio of driving wheelbase to overall engine wheebase 0.45
Overall Wheelbase (engine & tender)76.54'
Axle Loading (Maximum Weight per Axle)57900 lbs
Weight on Drivers231500 lbs
Engine Weight342000 lbs
Tender Light Weight171800 lbs
Total Engine and Tender Weight513800 lbs
Tender Water Capacity12000 gals
Tender Fuel Capacity (oil/coal)17.5 tons
Minimum weight per yard of rail on which locomotive could run96.46 lb rail
Geometry Relating to Tractive Effort
Driver Diameter69"
Boiler Pressure200 psi
Cylinders (dia x stroke)27" x 30"
Tractive Effort53883 lbs
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.30
Heating Ability
Firebox Area341 sq. ft
Grate Area70.30 sq. ft
Evaporative Heating Surface3789
Superheating Surface1103
Combined Heating Surface4892
Evaporative Heating Surface/Cylinder Volume190.59
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation14060
Same as above plus superheater percentage17230.11
Same as above but substitute firebox area for grate area83577.06
Power L117840.85
Power MT679.61

Credits

Introduction and specifications provided by Steve Llanso of Sweat House Media.

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