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Steam Locomotives of the Duluth, Missabe & Iron Range (DM&IR)[Inhalt]
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
Duluth, Missabe & Northern classes M, M-1 and M-2
United States | 1910 | 12 produced
M-1 No. 209
M-1 No. 209

In 1910, the DM&N initially received eight heavy Mallets of the 2-8-8-2 wheel arrangement, which they designated as class M and which largely corresponded to the class AB No. 600 of the Virginian. The intended area of operation was the ten miles from the docks in Duluth to Proctor at a gradient of 2.2 percent. Here the locomotive alone was to be able to push 55 empty ore wagons uphill at 12 mph

They were still operated with saturated steam, but had a second feedwater heater between the high and low pressure cylinders in addition to the regular one. By default, no stoker was installed, instead two firemen were used. While the 55 cars were a great challenge for the two firemen on the incline, locomotives with a retrofitted stoker could transport up to 85 empty ore cars. In the years 1916 and 1917, two more locomotives each followed, which were designated as class M-1 and M-2. These had a superheater from the factory and were five feet shorter overall.

Of the eight class M locomotives, seven were fitted with a superheater in 1925 and all those that did not yet have a stoker were retrofitted with one. The last locomotive, number 207, was built in 1930 in a total rebuild. In the completely new boiler, the superheater had a significantly larger share, resulting in a heating surface that was almost 60 percent larger overall. The cylinders were now of the same size without compound working. In the same year, the four M-1 and M-2 received a similar boiler with the larger superheater and four simple cylinders, which made them the M-2-S class.

VariantMM superheatedM-1, M-2M-2-S
Axle config2-8-8-2 (Mikado Mallet) 
Gauge4 ft 8 1/2 in (Standard gauge)
Dimensions and Weights
Wheelbase58 ft 2 in55 ft 9 in55 ft 4 in
Fixed wheelbase15 ft
Total wheelbase87 ft83 ft 6 1/2 in83 ft 10 in
Service weight448,100 lbs436,000 lbs470,200 lbs494,450 lbs
Adhesive weight406,600 lbs392,200 lbs415,200 lbs421,100 lbs
Total weight620,000 lbs607,900 lbs647,000 lbs689,650 lbs
Axle load50,825 lbs49,025 lbs51,900 lbs52,640 lbs
Water capacity9,000 us gal
Fuel capacity32,000 lbs (coal)42,000 lbs (coal)
Power sourcesteam
Estimated power3,200 hp (2,386 kW)3,400 hp (2,535 kW)3,700 hp (2,759 kW)3,900 hp (2,908 kW)
Optimal speed22 mph24 mph26 mph23 mph
Starting effort90,709 lbf109,945 lbf
with start valve108,851 lbf
Power Plant
Driver diameter57 in
Boiler pressure200 psi
Expansion typecompoundsimple
Cylindersfour, HP: 26 x 32 in
and LP: 40 x 32 in
four, 24 x 32 in
Grate area84 sq ft
Firebox area255 sq ft340 sq ft379 sq ft417 sq ft
Tube heating area6,635 sq ft3,782 sq ft5,045 sq ft5,024 sq ft
Evaporative heating area6,890 sq ft4,122 sq ft5,424 sq ft5,441 sq ft
Superheater area931 sq ft1,168 sq ft2,480 sq ft
Total heating area6,890 sq ft5,053 sq ft6,592 sq ft7,921 sq ft
Calculated Values
steam locomotive
last changed: 07/2023

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