Great Northern 2-6-6-2 Type Locomotives

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

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)

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 20 more in 1908 that are shown in the current entry.

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.

Class L-1 -S (Locobase 8854)

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

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.

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 collection.

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
Class	L-1 - 1st batch	L-1 - 2nd batch	L-1 -S	L-2	L-2 -S
Locobase ID	5354	819	8854	3554	8855
Railroad	Great Northern (GN)	Great Northern (GN)	Great Northern (GN)	Great Northern (GN)	Great Northern (GN)
Whyte	2-6-6-2	2-6-6-2	2-6-6-2	2-6-6-2	2-6-6-2
Road Numbers	1800-1804 / 1900-1904	1905-1924	1902, 1921	1810-1854	1814-16, 1822, 1824-26+
Gauge	Std	Std	Std	Std	Std
Builder	Burnham, Williams & Co	Burnham, Williams & Co	GN	Burnham, Williams & Co	GN
Year	1906	1908	1915	1907	1915
Valve Gear	Walschaert	Walschaert	Walschaert	Walschaert	Walschaert
	Locomotive Length and Weight
Driver Wheelbase	10'	10'	10'	9.83'	9.83'
Engine Wheelbase	44.83'	44.83'	44.83'	43.58'	43.58'
Ratio of driving wheelbase to overall engine wheebase	0.22	0.22	0.22	0.23	0.23
Overall Wheelbase (engine & tender)	73.17'	73.17'	73.19'	72.02'	71.60'
Axle Loading (Maximum Weight per Axle)	52667 lbs		52667 lbs		41667 lbs
Weight on Drivers	316000 lbs	321450 lbs	316000 lbs	250000 lbs	250000 lbs
Engine Weight	355000 lbs	362150 lbs	355000 lbs	280000 lbs	288000 lbs
Tender Light Weight	148000 lbs	152700 lbs	148200 lbs	152700 lbs	163000 lbs
Total Engine and Tender Weight	503000 lbs	514850 lbs	503200 lbs	432700 lbs	451000 lbs
Tender Water Capacity	8000 gals	8000 gals	8000 gals	8000 gals	8000 gals
Tender Fuel Capacity (oil/coal)	13 tons	13 tons	13 tons	13 tons	16 tons
Minimum weight per yard of rail on which locomotive could run	87.78 lb rail	89.29 lb rail	87.78 lb rail	69.44 lb rail	69.44 lb rail
	Geometry Relating to Tractive Effort
Driver Diameter	55"	55"	55"	55"	55"
Boiler Pressure	200 psi	200 psi	200 psi	210 psi	200 psi
Cylinders (dia x stroke)	21.5" x 32"	21.5" x 32"	24" x 32"	20" x 30"	20" x 30"
Low Pressure Cylinders (dia x stroke)	33" x 32"	33" x 32"	33" x 32"	31" x 30"	31" x 30"
Tractive Effort	64193 lbs	64193 lbs	74525 lbs	54999 lbs	52380 lbs
Factor of Adhesion (Weight on Drivers/Tractive Effort)	4.92	5.01	4.24	4.55	4.77
	Heating Ability
Firebox Area	230 sq. ft	225 sq. ft	230 sq. ft	198 sq. ft	206 sq. ft
Grate Area	78 sq. ft	78 sq. ft	78 sq. ft	53.40 sq. ft	78 sq. ft
Evaporative Heating Surface	5703	5658	4230	3906	3089
Superheating Surface			1070		725
Combined Heating Surface	5703	5658	5300	3906	3814
Evaporative Heating Surface/Cylinder Volume	424.13	420.78	252.46	358.08	283.18
	Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation	15600	15600	15600	11214	15600
Same as above plus superheater percentage	15600	15600	18749.43	11214	18565.39
Same as above but substitute firebox area for grate area	46000	45000	55286.79	41580	49031.67
Power L1	3966.14	3925.63	8686.97	3596.26	7446.04
Power MT	166.02	161.54	363.64	190.28	393.98