Class M (Locobase 317)

Data from tables in 1930 Locomotive Cyclopedia. Works numbers were 35165-35172 in September 1910.

Eight Mallet compounds virtually identical with Virginian 600. Stoking these engines was sometimes a problem even when two firemen were used. Although capable of handling 85 empties on the steep grades when fitted with mechanical stokers, the smallish boilers restricted their speed when so engaged.

Workhorse engines that were later given Schmidt superheaters, Standard mechanical stokers (in 1925), and Elesco feedwater heaters (in 1930). These engines were followed by 4 more engines fitted with superheaters from the start.

Class M - superheated (Locobase 6653)

Data from 1951 DM & IR locomotive diagram book supplied in May 2005 by Allen Stanley from his extensive collection.

When the M-class Mallets (see Locobase 317) were fitted with Schmidt superheaters, Standard mechanical stokers (in 1925), and Elesco feedwater heaters (in 1930), the result was as is shown here. The firebox heating surface now included thermic syphons.

Class M-1/M-2 (Locobase 318)

Firebox fitted with arch tubes, which contributed a considerable 48 sq ft to the heating surface total and large combustion chamber which added 108 sq ft. Works numbers were 43530-43531 in June 1916, 45769-45793 in June 1917.

Four Mallet compounds that followed the 8 bought in 1910 (see record # 317). They pulled empty ore trains up the ruling grade of 2.2% from the ore docks at Duluth and the Proctor yards and brought loaded cars back down; they weren't turned at either end. Of the 7 miles of line, 6 followed the grade while winding around compensated curves of 6-10 percent.

One source says that 208-209 had 77-sq ft grate area, which is smaller than earlier engines and presumably was still harder to fire and that 210-211 reverted to the early 84-sq ft grate, yielding a GDF of 61,750 and a CHS/GA ratio of 78.02. The data comes from a January 1917 table in Railway Mechanical Engineer for "208" that uses the 84-sq-ft figure.

Frank A King, writing in the November 1980 Trains, confirms the 84-sq-ft figure and notes that overall length was 5 feet less because the firebox was moved 5 ft farther forward.

All were converted to simple expansion locomotives in the 1930s. (see record # 319).

Class MS/etc (Locobase 319)

Data is for 208-209, rebuilt in 1931 and 1937, respectively, and is from the 1951 DM & IR locomotive diagram book supplied in May 2005 by Allen Stanley from his extensive collection..

210 (class M-2S) was rebuilt in 1929 with virtually identical specs except for an EHS of 5,441 sq ft and CHS of 7,921 (SHS% of CHS 31.31, BDF 792, CHS/GA ratio 94.3). She was nicknamed Madame Queen.

211 was rebuilt in 1931 and had an EHS of 5621 sq ft and a CHS of 8101 sq ft (SHS% of CHS 30.61, BDF 774, CHS/GA ratio 96.44).

The 207 (class MS) was rebuilt along similar lines in 1931, but came out heavier at 444,650 lb on the drivers.