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

Class L1 (USRA) (Locobase 7064)

Data from MNGHLA 12 - 1949 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. Works numbers were 60923-60932 in February 1919.

The diagram refers to the class as a standard USRA light Mikado (Locobase 40).

As shown in the late 1940s, however, the addition of 71 sq ft (6.60 sq m) of thermic syphons in addition to the 14 sq ft (1.30 sq m) of arch tubes contributing to the firebox heating surface as well as removal of the 24" (610 mm) 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, Volume 77, pp. 288+. (Many thanks to Chris Hohl for his 22 September 2017 email reporting unlikely boiler pressure values for 177 entries. A Locobase macro caused the error .) 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.