United States Railroad Administration 4-8-2 "Mountain" Locomotives in the USA


Class Details by Steve Llanso of Sweat House Media

Class Heavy (Locobase 232)

Data from tables in 1930 Locomotive Cyclopedia and from American Locomotive Company, Standardized Locomotives, US Railroad Administration (Alco Pamphlet 10049, 1918), pp. 30-31, reprinted by (Ocean, NJ: Specialty Press , 1973), and DeGolyer, Vol 57, pp. 121+. See also Robert A LeMassena, "The USRA HEAVY 4-8-2 and its Illustrious Ascendants", Railway & Locomotive Historical Society Newsletter (Vol 23, #2 - Spring 2003).

See also "Standard Equipment Specialties," Railway Mechanical Engineer, Vol 93, No 3 (March 1919), pp. 137-138 for a list of all the "special equipment" by manufacturers--everything from air brakes to lubricators to rolled steel wheels--and the USRA designs on which they appeared.

Boiler had feedwater heater, firebox heating surface area included 115 sq ft (10.7 sq m) and

34 sq ft (3.15 sq m), and piston valve diameter measured 14" (356 mm).

Only 15 "Heavy" mountains entered service under the USRA aegis. Baldwin built two engines for the C&O, Alco-Brooks supplied three more to the C&O as well as 10 more to the N&W. LeMassena argues, however, that this particular design influenced not only 4-8-2 designs, but also encouraged the development of the larger 4-8-4.


Class Light (Locobase 231)

Data from tables in 1930 Locomotive Cyclopedia, "Two More Standard Locomotives," Railway Mechanical Engineer, Vol 93, No 1 (January 1919), pp. 25-30, and from American Locomotive Company, Standardized Locomotives, US Railroad Administration (Alco Pamphlet 10049, 1918), pp. 28-29, reprinted by (Ocean, NJ: Specialty Press , 1973) and DeGolyer, Vol 58, pp. 108+.

See also "Standard Equipment Specialties," Railway Mechanical Engineer, Vol 93, No 3 (March 1919), pp. 137-138 for a list of all the "special equipment" by manufacturers--everything from air brakes to lubricators to rolled steel wheels--and the USRA designs on which they appeared.

Boiler had feedwater heater and the same tube and flue count as the USRA's Heavy Pacifics and Heavy Mikados. Firebox heating surface included 105 sq ft (9.75 sq m) in the combustion chamber and 28 sq ft (2.6 sq m) in arch tubes. Cylinders were served by piston valves measuring 14" (356 mm) in diameter.

Standard light "Mountain" design as conceived for mass production during World War I. Four railroads bought 47 locomotives, 25 going to the Southern. Baldwin built 15 (for the Southern), Alco-Richmond supplied 15, and Alco-Schenectady delivered 17 to the MoPac and the Southern. Most later Mountains had a higher superheater to evaporative heating surface ratio and a higher boiler pressure.

Specifications by Steve Llanso of Sweat House Media
ClassHeavyLight
Locobase ID232 231
RailroadUnited States Railroad Administration (USRA)United States Railroad Administration (USRA)
CountryUSAUSA
Whyte4-8-24-8-2
Number in Class
Road Numbers10,00010,000
GaugeStdStd
Number Built15
BuilderSeveralSeveral
Year19181918
Valve GearBakerBaker
Locomotive Length and Weight
Driver Wheelbase (ft / m)18.25 / 5.5618.25 / 5.56
Engine Wheelbase (ft / m)40 / 12.1940 / 12.19
Ratio of driving wheelbase to overall engine wheebase 0.46 0.46
Overall Wheelbase (engine & tender) (ft / m)75.70 / 23.0775.70 / 23.07
Axle Loading (Maximum Weight per Axle) (lbs / kg)56,500 / 25,628
Weight on Drivers (lbs / kg)243,000 / 110,223224,500 / 101,832
Engine Weight (lbs / kg)352,500 / 159,892327,000 / 148,325
Tender Loaded Weight (lbs / kg)194,200193,700 / 87,861
Total Engine and Tender Weight (lbs / kg)546,700520,700 / 236,186
Tender Water Capacity (gals / ML)10,000 / 37.8810,000 / 37.88
Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT)16 / 14.5016 / 14.50
Minimum weight of rail (calculated) (lb/yd / kg/m)101 / 50.5094 / 47
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)69 / 175369 / 1753
Boiler Pressure (psi / kPa)200 / 13.80200 / 13.80
High Pressure Cylinders (dia x stroke) (in / mm)28" x 30" / 711x76227" x 30" / 686x762
Tractive Effort (lbs / kg)57,948 / 26284.8053,883 / 24440.95
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.19 4.17
Heating Ability
Firebox Area (sq ft / m2)373 / 34.67348 / 32.34
Grate Area (sq ft / m2)76.30 / 7.0970.30 / 6.53
Evaporative Heating Surface (sq ft / m2)4666 / 433.644121 / 382.99
Superheating Surface (sq ft / m2)1085 / 100.84966 / 89.78
Combined Heating Surface (sq ft / m2)5751 / 534.485087 / 472.77
Evaporative Heating Surface/Cylinder Volume218.24207.29
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation15,26014,060
Same as above plus superheater percentage18,15916,731
Same as above but substitute firebox area for grate area88,77482,824
Power L117,53116,839
Power MT636.20661.44