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Northern Pacific classes WA, WB and W-1
United States | 1904 | 200 produced
WA No. 1517
WA No. 1517
Railway and Locomotive Engineering, January 1905

The Northern Pacific was the first US railroad to purchase a significant number of Mikados. These machines grouped under the class W were 55 locomotives of the subclass WA without a combustion chamber and 105 WB with a combustion chamber. Some of these were built as compound locomotives and later rebuilt. 40 class W-1 locomotives followed in 1910, which differed mainly in that they had Walschaerts valve gear in contrast to the Stephenson valve gear of their predecessors. Most of the locomotives were superheated from 1912, and the boiler pressure was increased to 200 psi with thicker boiler plates.

VariantWAWBWA/WB superheatedW-1
General
Built1904190619121910
ManufacturerALCONorthern PacificALCO
Axle config2-8-2 (Mikado) 
Gauge4 ft 8 1/2 in (Standard gauge)
Dimensions and Weights
Wheelbase34 ft 9 in
Fixed wheelbase16 ft 6 in
Service weight259,000 lbs258,000 lbs263,500 lbs269,600 lbs
Adhesive weight203,500 lbs201,500 lbs206,000 lbs208,900 lbs
Total weight407,500 lbs435,800 lbs455,300 lbs461,400 lbs
Axle load58,000 lbs57,700 lbs58,700 lbs59,600 lbs
Water capacity8,000 us gal10,000 us gal
Fuel capacity24,000 lbs (coal)38,000 lbs (coal)
Power
Power sourcesteam
Estimated power1,500 hp (1,119 kW)1,450 hp (1,081 kW)1,750 hp (1,305 kW)1,600 hp (1,193 kW)
Optimal speed24 mph23 mph24 mph
Starting effort39,634 lbf46,629 lbf43,006 lbf
Power Plant
Driver diameter63 in
Boiler pressure170 psi200 psi170 psi
Expansion typesimple
Cylinderstwo, 24 x 30 intwo, 25 x 30 in
Boiler
Grate area43.5 sq ft
Firebox area209 sq ft245 sq ft250 sq ft270 sq ft
Tube heating area3,798 sq ft3,247 sq ft2,611 sq ft2,563 sq ft
Evaporative heating area4,007 sq ft3,492 sq ft2,861 sq ft2,833 sq ft
Superheater area570 sq ft465 sq ft
Total heating area4,007 sq ft3,492 sq ft3,431 sq ft3,298 sq ft
Calculated Values
steam locomotive
freight
last changed: 04/2023
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