USRA 4-6-2 "Pacific" Type Locomotives

Class Details by Steve Llanso

Class Heavy (Locobase 173)

Data from tables in 1930 Locomotive Cyclopedia and from American Locomotive Company, Standardized Locomotives, US Railroad Administration (Alco Pamphlet 10049, 1918), pp. 26-27, reprinted by (Ocean, NJ: Specialty Press , 1973) and DeGolyer, Vol 58, pp. 48+.

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.

Intended to be the standardized Pacific heavy passenger express locomotive, but only twenty were actually allocated by the USRA. The design shared the tube and flue count with two other USRA variants: Light Mikado (Locobase 40) and Light Mountain (Locobase 231). Firebox heating surface included 72 sq ft (6.7 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.

Erie's were built by Alco-Richmond (10) and Baldwin (10) at the direction of the government-run USRA beginning in 1918.

Class Light (Locobase 172)

Data from tables in 1930 Locomotive Cyclopedia and from American Locomotive Company, Standardized Locomotives, US Railroad Administration (Alco Pamphlet 10049, 1918), pp. 24-25, reprinted by (Ocean, NJ: Specialty Press , 1973). See also DeGolyer, Vol 58, pp. 35+ and "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.

This was the "light" Pacific design standardized by the government-run USRA created in World War I and built by Baldwin and Alco. Three railroads actually took delivery of 81 locomotives: Atlantic Coast Lines (28 by Alco-Brooks, 17 by Alco-Richmond), the B&O (20 by Baldwin, 10 by Alco-Richmond), and L&N (6 by Alco-Richmond).

Although described as light, the design in fact had a relatively large grate compared to other engines within its axle-loading range. Firebox heating surface included 46 sq ft (4.3 sq m) in the combustion chamber and 27 sq ft (2.5 sq m) in arch tubes. Cylinders were served by piston valves measuring 14" (356 mm) in diameter.

In the literature describing particular railroads' acquisitions, this design often appears either as the direct-from-USRA variant or a later class based on the USRA Light. And very often, the USRA-inspired 4-6-2 is described as the best, most reliable Pacifics the railroad would own.


Specifications by Steve Llanso
ClassHeavyLight
Locobase ID173 172
RailroadUSRAUSRA
Whyte4-6-24-6-2
Road Numbers1000010000
GaugeStdStd
BuilderSeveralSeveral
Year19181918
Valve GearBakerBaker
Locomotive Length and Weight
Driver Wheelbase14'13'
Engine Wheelbase36.17'34.75'
Ratio of driving wheelbase to overall engine wheebase 0.39 0.37
Overall Wheelbase (engine & tender)70.70'68.62'
Axle Loading (Maximum Weight per Axle)60000 lbs54000 lbs
Weight on Drivers197000 lbs162000 lbs
Engine Weight306000 lbs277000 lbs
Tender Light Weight194200 lbs194000 lbs
Total Engine and Tender Weight500200 lbs471000 lbs
Tender Water Capacity10000 gals10000 gals
Tender Fuel Capacity (oil/coal)16 tons16 tons
Minimum weight of rail (calculated) on which locomotive could run109 lb/yard90 lb/yard
Geometry Relating to Tractive Effort
Driver Diameter79"73"
Boiler Pressure200 psi200 psi
Cylinders (dia x stroke)27" x 28"25" x 28"
Tractive Effort43925 lbs40753 lbs
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.48 3.98
Heating Ability
Firebox Area327 sq. ft261 sq. ft
Grate Area70.80 sq. ft66.70 sq. ft
Evaporative Heating Surface3824 sq. ft3333 sq. ft
Superheating Surface887 sq. ft794 sq. ft
Combined Heating Surface4711 sq. ft4127 sq. ft
Evaporative Heating Surface/Cylinder Volume206.09209.52
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation1416013340
Same as above plus superheater percentage1685015875
Same as above but substitute firebox area for grate area7782662118
Power L11907718025
Power MT640.47735.89

Credits

Introduction and roster provided by Richard Duley. Class details and specifications provided by Steve Llanso of Sweat House Media.