Monongahela 2-8-2 "Mikado" Locomotives in the USA


Class Details by Steve Llanso of Sweat House Media

Class L1 (Locobase 7064)

Data from MNGHLA 12 - 1949 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange.

This class of Mikes came as a single batch from Schenectady (builder's numbers 60923-60932 in February 1919).

The diagram refers to the class as a standard USRA light Mikado. As shown in the late 1940s, however, the addition of 71 sq ft of thermic syphons in addition to the 14 sq ft of arch tubes contributing to the firebox heating surface as well as removal of the combustion chamber changed the boiler to a small degree. This upgrade may have been prompted by the delivery of the six Baldwins as class L2 in the late 1920s (Locobase 27). It resulted in a boiler that still had less superheater area than did the L2.


Class L2 (Locobase 27)

Data from table in 1930 Locomotive Cyclopedia. See also DeGolyer, Vol 77, pp. 288+. Works numbers were 60087-60089 in June 1927 and 60094-60096 in July.

This sextet of coal-haulers was typical of US Mikado locomotives in the late 1920s and like many of them, was based on the USRA design of 1919. Indeed, the specification calls for a duplication of the L1 design (Locobase 7064), "except for changes in design and specialties."

The layout of the boiler suggests that it was the site of most of those changes. The combustion chamber was omitted and the firebox heating surface now included two thermic syphons comprising 71 sq ft (6.6 sq m) and 14 sq ft (1.3 sq m) in two arch tubes. The boiler had exhaust steam injector. Fourteen-inch (356 mm) piston valves supplied steam to the cylinders.

Specifications by Steve Llanso of Sweat House Media
ClassL1L2
Locobase ID7064 27
RailroadMonongahelaMonongahela
CountryUSAUSA
Whyte2-8-22-8-2
Number in Class106
Road Numbers170-179180-185
GaugeStdStd
Number Built106
BuilderAlco-SchenectadyBaldwin
Year19191927
Valve GearWalschaertWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m)16.75 / 5.1116.80 / 5.12
Engine Wheelbase (ft / m)36.92 / 11.2536.90 / 11.25
Ratio of driving wheelbase to overall engine wheebase 0.45 0.46
Overall Wheelbase (engine & tender) (ft / m)71.55 / 21.8171.55 / 21.81
Axle Loading (Maximum Weight per Axle) (lbs / kg)62,500 / 28,35060,160 / 27,288
Weight on Drivers (lbs / kg)233,300 / 105,823236,080 / 107,084
Engine Weight (lbs / kg)306,050 / 138,822318,740 / 144,578
Tender Loaded Weight (lbs / kg)207,000 / 93,894206,500 / 93,667
Total Engine and Tender Weight (lbs / kg)513,050 / 232,716525,240 / 238,245
Tender Water Capacity (gals / ML)12,500 / 47.3512,500 / 47.35
Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT)16 / 14.5016 / 14.50
Minimum weight of rail (calculated) (lb/yd)9798
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)63 / 160063 / 1600
Boiler Pressure (psi / kPa)200 / 13.80200 / 13.80
High Pressure Cylinders (dia x stroke) (in / mm)26" x 30" / 660x76226" x 30" / 660x762
Tractive Effort (lbs / kg)54,724 / 24822.4254,724 / 24822.42
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.26 4.31
Heating Ability
Firebox Area (sq ft / m2)281 / 26.11292.25 / 27.15
Grate Area (sq ft / m2)66.70 / 6.2066.70 / 6.20
Evaporative Heating Surface (sq ft / m2)4059 / 377.093876 / 360.22
Superheating Surface (sq ft / m2)882 / 81.941080 / 100.37
Combined Heating Surface (sq ft / m2)4941 / 459.034956 / 460.59
Evaporative Heating Surface/Cylinder Volume220.18210.25
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation13,34013,340
Same as above plus superheater percentage15,74116,275
Same as above but substitute firebox area for grate area66,31671,309
Power L115,26717,152
Power MT577.08640.69