USRA Heavy Mikado

The USRA Heavy Mikado was a USRA standard class of steam locomotive designed under the control of the United States Railroad Administration (USRA), the nationalized railroad system in the United States during World War I. These locomotives were of 2-8-2 wheel arrangement in the Whyte notation, or 1′D1′ in UIC classification. A total of 233 locomotives were built to this plan for the USRA; postwar, it became a de facto standard design, which was built to the total of 957 locomotives including the USRA originals and all subsequent copies.[2]

USRA Heavy Mikado
Type and origin Power type Steam Builder ALCO, Baldwin, Lima Build date 1918–? Total produced 233 originals, plus 724 copies[1]
Specifications Configuration: ​  • Whyte 2-8-2  • UIC 1′D1′ h2 Driver dia. 63 in (1,600 mm)[2] Wheelbase locomotive: 36 ft 1 in (11.00 m)[2] Firebox:  • Firegrate area 70.8 sq ft (6.58 m2)[2] Boiler pressure 190 psi (1.31 MPa)[2] Cylinders Two[2] Cylinder size 27 in × 32 in (690 mm × 810 mm)[2] Valve gear Walschaerts[2]
Performance figures Tractive effort 60,000 lbf (270 kN)[2]
Career Disposition All Scrapped

General arrangement drawing.

Heavy Mikado used the same running gear as the USRA Light Mikado but were built to a higher axle load, larger cylinders and a much larger boiler for more power and steam-generating ability. Many aspects of the PRR L1s class were carried over to the Heavy Mikado, although not that locomotive's distinctive Belpaire firebox.[1]