The reference for locomotives and railcars
Duluth, Missabe & Iron Range classes M-3 and M-4
United States | 1941 | 18 produced
M3 No. 221
M3 No. 221
Missabe Railroad Historical Society

For heavy ore trains with up to 115 cars, the Duluth, Missabe & Iron Range needed more powerful locomotives, where the most difficult task was to pull the empty trains up the 2.2 percent steep ramp from the port in Duluth to the marshalling yard in Proctor. The Western Pacific class M-137 was taken as the basis. With a two-axle trailing bogie, the wheel arrangement was 2-8-8-4 "Yellowstone", which allowed for a larger firebox and a larger all-weather cab for the cold Minnesota winters.

In 1941 eight members of the M-3 class were built and in 1943 ten more M-4s. Since the DM&IR had less traffic volume in winter, some of the locomotives were leased out. They were particularly valued by the D&RGW, where they had to pull heavy freight trains over a 10,239 foot high pass over the Continental Divide. With the exception of one locomotive that had an accident, all remained in use until they were replaced by diesel locomotives between 1958 and 1963. Today three remain, all of which are no longer operational.

Built1941, 1943
Axle config2-8-8-4 (Yellowstone (Mallet)) 
Gauge4 ft 8 1/2 (Standard gauge)
Dimensions and Weights
Wheelbase67 ft 2 in
Fixed wheelbase17 ft 3 in
Total wheelbase113 ft 6 in
Service weight695,040 lbs
Adhesive weight560,257 lbs
Total weight1,133,040 lbs
Axle load70,033 lbs
Water capacity25,000 us gal
Fuel capacity54,000 lbs (coal)
Power sourcesteam
Estimated power6,000 hp (4,474 kW)
Optimal speed27 mph
Starting effort140,093 lbf
Power Plant
Driver diameter63 in
Boiler pressure240 psi
Expansion typesimple
Cylindersfour, 26 x 32 in
Grate area125 sq ft
Firebox area750 sq ft
Tube heating area6,032 sq ft
Evaporative heating area6,782 sq ft
Superheater area2,770 sq ft
Total heating area9,552 sq ft
Calculated Values
steam locomotive
last changed: 02/2024

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