The reference for locomotives and railcars
Great Northern (US) class L-1
United States | 1906 | 25 produced
No. 1917 around 1920 at Wellington, Washington
No. 1917 around 1920 at Wellington, Washington
Curtiss Miller / collection Taylor Rush

The first Mallet with the 2-6-6-2 wheel arrangement was the L-1 class of the Great Northern. They were created in 1906 by adding a leading and a trailing axle to the 0-6-6-0 in order to improve running in curves. They were used as helpers in the Cascades. After the first five, 20 more followed in 1908 after the L-2, which had been delivered in the meantime, turned out to be too light. The class Z of the Northern Pacific was identical to these.

Although they had a Belpaire firebox, its heating surface was very small compared to the total heating surface. At least two L-1s received a superheater around 1915, and they also received significantly larger high-pressure cylinders. However, as early as 1925 and 1926, all L-1s were rebuilt to class O-6 Mikados, which remained in use until the mid-1950s.

Built1906, 1908
Axle config2-6-6-2 (Mallet Mogul) 
Gauge4 ft 8 1/2 in (Standard gauge)
Dimensions and Weights
Wheelbase44 ft 10 in
Fixed wheelbase10 ft
Total wheelbase73 ft 2 in
Service weight355,000 lbs
Adhesive weight316,000 lbs
Total weight503,000 lbs
Axle load52,667 lbs
Water capacity8,000 us gal
Fuel capacity26,000 lbs (coal)
Power sourcesteam
Estimated power2,500 hp (1,864 kW)
Optimal speed25 mph
Starting effort64,193 lbf
with start valve77,032 lbf
Power Plant
Driver diameter55 in
Boiler pressure200 psi
Expansion typecompound
Cylindersfour, HP: 21 1/2 x 32 in
and LP: 33 x 32 in
Grate area78 sq ft
Firebox area225 sq ft
Tube heating area5,433 sq ft
Evaporative heating area5,658 sq ft
Total heating area5,658 sq ft
Calculated Values
steam locomotive
last changed: 02/2024

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