Three more Class N-20 "Mountains", road numbers 4018 through 4020, were built by the MStP&SSM (Soo Line) in its Shoreham Shops in Minneapolis, MN.
All twenty-one of these Class N-20 "Mountains" had 27 x 30 cylinders, 69" drivers, and a boiler pressure of 200 psi which resulted in a tractive effort of 53,900 pounds.
There are no surviving Soo Line "Mountains".
|Class||Qty||Road Numbers||Locomotive Weight||Year Built||Builder|
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 an estimate. 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 by Steve Llanso of Sweat House Media|
|Railroad||Minneapolis, St Paul & Sault Ste Marie (Soo)|
|Number in Class||21|
|Locomotive Length and Weight|
|Driver Wheelbase (ft / m)||18.25 / 5.56|
|Engine Wheelbase (ft / m)||40.83 / 12.44|
|Ratio of driving wheelbase to overall engine wheebase||0.45|
|Overall Wheelbase (engine & tender) (ft / m)||76.54 / 23.33|
|Axle Loading (Maximum Weight per Axle) (lbs / kg)||57,900 / 26,263|
|Weight on Drivers (lbs / kg)||231,500 / 105,007|
|Engine Weight (lbs / kg)||342,000 / 155,129|
|Tender Loaded Weight (lbs / kg)||171,800 / 77,927|
|Total Engine and Tender Weight (lbs / kg)||513,800 / 233,056|
|Tender Water Capacity (gals / ML)||12,000 / 45.45|
|Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT)||17.50 / 15.90|
|Minimum weight of rail (calculated) (lb/yd / kg/m)||96 / 48|
|Geometry Relating to Tractive Effort|
|Driver Diameter (in / mm)||69 / 1753|
|Boiler Pressure (psi / kPa)||200 / 13.80|
|High Pressure Cylinders (dia x stroke) (in / mm)||27" x 30" / 686x762|
|Tractive Effort (lbs / kg)||53,883 / 24440.95|
|Factor of Adhesion (Weight on Drivers/Tractive Effort)||4.30|
|Firebox Area (sq ft / m2)||341 / 31.69|
|Grate Area (sq ft / m2)||70.30 / 6.53|
|Evaporative Heating Surface (sq ft / m2)||3789 / 352.14|
|Superheating Surface (sq ft / m2)||1103 / 102.51|
|Combined Heating Surface (sq ft / m2)||4892 / 454.65|
|Evaporative Heating Surface/Cylinder Volume||190.59|
|Computations Relating to Power Output (More Information)|
|Robert LeMassena's Power Computation||14,060|
|Same as above plus superheater percentage||17,294|
|Same as above but substitute firebox area for grate area||83,886|