Great Northern 2-6-6-2 "Mallet Mogul" Locomotives in the USA

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Class Details by Steve Llanso of Sweat House Media

Class L-1 - 1st batch (Locobase 5354)

Data from GN 1916 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. Works numbers were 28601, 28641 in July 1906; 28739, 28854 in August; and 28933 in September.

These were the first locomotives built with this wheel arrangement, which united the pulling power of the 0-6-6-0 that ran so successfully on the B&O with both lead and trailing trucks for more flexible operation. A distinguishing feature was the long Belpaire firebox, but a very small percentage of heating surface being direct.

These first five performed as helpers in the Cascades, the next 45 went out on the road themselves. The CB & Q bought 3 identical T-1s (Locobase 1047) in 1908.


Class L-1 - 2nd batch (Locobase 819)

Data from DeGolyer, Volume 30, p. 24. Works numbers were 32722-32725, 32732, 32734-32735, 32740-32743, 32746-32749 in March 1908; 32755, 32758-32761 in April.

Soon after the first quintet of L-1s came on the range, the Great Northern bought some smaller L-2s (Locobase 3554). One can guess that those engines weren't quite powerful enough, so the GN tweaked the L-1 design slightly (yielding a slightly smaller boiler) and ordered the twenty more in 1908 that are shown in the current entry. The first three in the class (1905-1907) were sold to the Chicago, Burlington & Quincy as their T-1 class 4000-4002. Then the GN renumbered the last three locomotives from 1922-1924 to 1905-1907.

The Northern Pacific purchased the same design in the form of 16 Zs (Locobase 1046) in the same year. Western Maryland's 9 M-1s (Locobase 8321) used the same boiler and firebox, but had larger HP cylinders.

The others served the GN until the mid-1920s, when they were converted to O-6 2-8-2s; see Locobase 7449.


Class L-1 -S (Locobase 8854)

Data from GN 1916 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange.

At least two of the GN's L-1 2-6-6-2s (Locobase 5334) were superheated. In the process, the HP cylinders grew by 2 1/2" while the boiler's overall heating surface remained nearly the same. As these two were converted to O-6 Mikados in 1926 (Locobase 7449) as well as the rest of the class, the program must not have been very extensive.


Class L-2 (Locobase 3554)

Data from table in June 1908 American Engineer and Railroad Journal. Works numbers were 30400, 30422, 30445-30446 in March 1907; 30563-30565, 30588 in April; 30800-30803, 30846-30848, 30918-30919, 30943 in May; 31002-31004, 31065, 31105 in June; 31183-31184 in July; 32688-32691, 32696-32711 in February 1908.

These were smaller than the earlier L-1s (Locobase 5354), with a boiler, says Drury (1993) taken from the H-2 Pacifics. Small Mallets with Belpaire fireboxes, these engines weren't repeated as the Great Northern went for much bigger articulateds. Northern Pacific bought 6 copies in the same year (Locobase 821) .


Class L-2 -S (Locobase 8855)

Data from GN 1916 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange.

Although the GN found its 2-6-6-2s unremarkable, the railroad still superheated some of these pocket Mallets. Leaving the Belpaire firebox and the power dimensions alone, the shops performed the usual exchange of fire-tubes for flues. Most kept their HP slide valves, but three traded in for piston valves. Like the L-1, the class was rebuilt as 2-8-2s (O-5 class; Locobase 7450) in the 1920s.

Specifications by Steve Llanso of Sweat House Media
ClassL-1 - 1st batchL-1 - 2nd batchL-1 -SL-2L-2 -S
Locobase ID5354 819 8854 3554 8855
RailroadGreat Northern (GN)Great Northern (GN)Great Northern (GN)Great Northern (GN)Great Northern (GN)
CountryUSAUSAUSAUSAUSA
Whyte2-6-6-22-6-6-22-6-6-22-6-6-22-6-6-2
Number in Class5172508
Road Numbers1800-1804 / 1900-19041905-19211902, 19211805-18541814-16, 1822, 1824-26+
GaugeStdStdStdStdStd
Number Built51750
BuilderBurnham, Williams & CoBurnham, Williams & CoGNBurnham, Williams & CoGN
Year19061908191519071915
Valve GearWalschaertWalschaertWalschaertWalschaertWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m)10 / 3.0510 / 3.0510 / 3.05 9.83 / 3 9.83 / 3
Engine Wheelbase (ft / m)44.83 / 13.6644.83 / 13.6644.83 / 13.6643.58 / 13.2843.58 / 13.28
Ratio of driving wheelbase to overall engine wheebase 0.22 0.22 0.22 0.23 0.23
Overall Wheelbase (engine & tender) (ft / m)73.17 / 22.3073.17 / 22.3073.19 / 22.3172.02 / 21.9571.60 / 21.82
Axle Loading (Maximum Weight per Axle) (lbs / kg)52,667 / 23,88952,667 / 23,88941,667 / 18,900
Weight on Drivers (lbs / kg)316,000 / 143,335321,450 / 145,807316,000 / 143,335250,000 / 113,398250,000 / 113,398
Engine Weight (lbs / kg)355,000 / 161,025362,150 / 164,269355,000 / 161,025280,000 / 127,006288,000 / 130,635
Tender Loaded Weight (lbs / kg)148,000 / 67,132152,700 / 69,264148,200 / 67,222152,700 / 69,264163,000 / 73,936
Total Engine and Tender Weight (lbs / kg)503,000 / 228,157514,850 / 233,533503,200 / 228,247432,700 / 196,270451,000 / 204,571
Tender Water Capacity (gals / ML)8000 / 30.308000 / 30.308000 / 30.308000 / 30.308000 / 30.30
Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT)13 / 11.8013 / 11.8013 / 11.8013 / 11.8016 / 14.50
Minimum weight of rail (calculated) (lb/yd / kg/m)88 / 4489 / 44.5088 / 4469 / 34.5069 / 34.50
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)55 / 139755 / 139755 / 139755 / 139755 / 1397
Boiler Pressure (psi / kPa)200 / 13.80200 / 13.80200 / 13.80210 / 14.50200 / 13.80
High Pressure Cylinders (dia x stroke) (in / mm)21.5" x 32" / 546x81321.5" x 32" / 546x81324" x 32" / 610x81320" x 30" / 508x76220" x 30" / 508x762
Low Pressure Cylinders (dia x stroke) (in / mm)33" x 32" / 838x81333" x 32" / 838x81333" x 32" / 838x81331" x 30" / 787x76231" x 30" / 787x762
Tractive Effort (lbs / kg)64,193 / 29117.4964,193 / 29117.4974,525 / 33804.0154,999 / 24947.1652,380 / 23759.20
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.92 5.01 4.24 4.55 4.77
Heating Ability
Firebox Area (sq ft / m2)230 / 21.38225 / 20.91230 / 21.38198 / 18.40206 / 19.14
Grate Area (sq ft / m2)78 / 7.2578 / 7.2578 / 7.2553.40 / 4.9678 / 7.25
Evaporative Heating Surface (sq ft / m2)5703 / 530.025658 / 525.844230 / 393.123906 / 363.013089 / 287.08
Superheating Surface (sq ft / m2)1070 / 99.44725 / 67.38
Combined Heating Surface (sq ft / m2)5703 / 530.025658 / 525.845300 / 492.563906 / 363.013814 / 354.46
Evaporative Heating Surface/Cylinder Volume424.13420.78252.46358.08283.18
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation15,60015,60015,60011,21415,600
Same as above plus superheater percentage15,60015,60018,72011,21418,564
Same as above but substitute firebox area for grate area46,00045,00055,20041,58049,028
Power L139663926868735967446
Power MT166.02161.56363.64190.27393.97

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