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Norfolk & Western classes M and M1
United States | 1906 | 225 produced
Class M No. 450 in a Baldwin factory photo
Class M No. 450 in a Baldwin factory photo

In order to be able to accommodate a longer boiler on the Consolidation, the Norfolk & Western chose the 4-8-0 “Twelve-wheeler” wheel arrangement instead of the Mikado. The aim was to achieve a higher adhesive weight because the weight of the firebox was placed on the rear driving axles. Even the firebox was extended to the rear of the cab so that the engineer and fireman were separated from each other. They were nicknamed “Mollies” by the crews.

After 125 class M locomotives, 100 more class M1 locomotives were built. They only differed in the valve gear and the valves. Due to design errors, the M1 was subject to high levels of wear and tear, so it was phased out relatively early. The M was replaced on main lines by the 2-8-8-2 class Y and was used on secondary lines and in switching service until the late 1950s. Only ten had received a superheater. The number 475 is still in use on the Strasburg Railroad today and the 433 also survives.

VariantMM1
General
Built1906-19071907
ManufacturerALCO, Baldwin, N&W Roanoke Shops
Axle config4-8-0 (Twelve-wheeler) 
Gauge4 ft 8 1/2 in (Standard gauge)
Dimensions and Weights
Wheelbase24 ft 5 in
Fixed wheelbase15 ft 6 in
Total wheelbase58 ft 4 1/2 in53 ft 7 in
Service weight206,200 lbs204,500 lbs
Adhesive weight169,800 lbs165,850 lbs
Total weight373,700 lbs321,100 lbs
Axle load42,450 lbs41,463 lbs
Water capacity9,000 us gal6,000 us gal
Fuel capacity28,000 lbs (coal)20,000 lbs (coal)
Power
Power sourcesteam
Estimated power1,400 hp (1,044 kW)
Optimal speed22 mph
Starting effort40,162 lbf
Power Plant
Driver diameter56 in
Boiler pressure200 psi
Expansion typesimple
Cylinderstwo, 21 x 30 in
Boiler
Grate area45 sq ft
Firebox area173 sq ft
Tube heating area2,624 sq ft
Evaporative heating area2,797 sq ft
Total heating area2,797 sq ft
Calculated Values
steam locomotive
freight
last changed: 11/2023
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