Montana, Wyoming & Southern 2-8-2 "Mikado" Locomotives in the USA

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Class Details by Steve Llanso of Sweat House Media

Class 20 (Locobase 15304)

Data from DeGolyer, Vol 73, pp. 194. Works number was 57975 in September 1924.

Locobase 14952 describes the MW&S and the Consolidation Baldwin sold to the railroad in 1920. This Mikado increased the cylinder volume only slightly while rolling on taller drivers. The locomotive still traveled on 65 lb/yard (32.5 kg/metre) rail up 4.4% grades and around 18 degree curves (radii of 320 feet/97.5 metres).

A much longer boiler created more heating surface, both evaporative and superheater, which undoubtedly permitted longer, heavier hauls before running out of steam. Thirteen-inch (330 mm) piston valves supplied the cylinders.

Specifications by Steve Llanso of Sweat House Media
Locobase ID15,304
RailroadMontana, Wyoming & Southern
Number in Class16
Road Numbers20
Number Built16
Valve GearWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m)15 / 4.57
Engine Wheelbase (ft / m)31.67 / 9.65
Ratio of driving wheelbase to overall engine wheebase 0.47
Overall Wheelbase (engine & tender) (ft / m)62.58 / 19.07
Axle Loading (Maximum Weight per Axle) (lbs / kg)
Weight on Drivers (lbs / kg)154,000 / 69,853
Engine Weight (lbs / kg)208,000 / 94,347
Tender Loaded Weight (lbs / kg)143,000 / 64,864
Total Engine and Tender Weight (lbs / kg)351,000 / 159,211
Tender Water Capacity (gals / ML)7000 / 26.52
Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT)12 / 10.90
Minimum weight of rail (calculated) (lb/yd / kg/m)64 / 32
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)56 / 1422
Boiler Pressure (psi / kPa)190 / 12.80
High Pressure Cylinders (dia x stroke) (in / mm)22" x 28" / 559x711
Tractive Effort (lbs / kg)39,083 / 17727.77
Factor of Adhesion (Weight on Drivers/Tractive Effort) 3.94
Heating Ability
Firebox Area (sq ft / m2)187 / 17.37
Grate Area (sq ft / m2)46.80 / 4.35
Evaporative Heating Surface (sq ft / m2)2560 / 237.83
Superheating Surface (sq ft / m2)533 / 49.52
Combined Heating Surface (sq ft / m2)3093 / 287.35
Evaporative Heating Surface/Cylinder Volume207.81
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation8892
Same as above plus superheater percentage10,404
Same as above but substitute firebox area for grate area41,570
Power L111,936
Power MT683.49