Great Northern 2-8-8-0 "Consolidation Mallet" Type Locomotives

Class N-1 (Locobase 307)

Originally built by Great Northern with relatively tall drivers for a compound articulated. They presented an imposing appearance, showing a high Belpaire boiler over 10 axles of running gear. Firebox heating surface included 81 sq ft of arch pipes. The N-1s were simpled in the 1920s, becoming N-2s and later N-3s in the process.

Class N-2 (Locobase 2802)

These were the tallest locomotives on the Great Northern because the designers had to get the large firebox above the rearmost driving axle. Delivered as N-1 compounds by Baldwin in 1912, these engines were simpled in the mid-1920s (N-2), pressing the boiler to 240 psi and generating 100,200 lb of tractive effort. The Belpaire firebox with its 81 sq ft of arch tubes remained unchanged. They did get 13" piston valves and some were converted to oil burning and trailed tenders carrying 17,000 gallons of water and 4,600 gallons of fuel oil.

In the early 1940s they got new frames and roller bearings as well as a larger grate; at that point they became N-3s; see Locobase 6445

Class N-3 (Locobase 6445)

Delivered as N-1 compounds by Baldwin in 1912 (Locobase 307), these engines were simpled in the mid-1920s (N-2; Locobase 2802). Note that they still had the characteristic Belpaire firebox.

In the early 1940s they got new frames, nickel-steel boilers, and roller bearings as well as a larger grate; at that point they became N-3s.

http://www.greatnorthernempire.net/index2.htm?GNEGNPrototypeDrawingsSteam.htm (visited 7 Jan 2005) shows all of the numbers in the GN's locomotive diagram. A note says the boiler had a nominal pressure of 275 psi, but was lowered to 265 psi for working. A comparison with the N-1's factors shows what a huge increase in power these rebuilds represented.

The timing couldn't have been better, either. The first of the rebuilds (2024) was completed on 10 February 1940, the last (2009) wrapping up almost exactly 2 years later on 12 Feb 1942. Thus the greater horsepower was available in time for the Great Northern's World War II traffic spike.

And did the N-3s ever deliver, according to Charles R. Wood, in Lines West (New York: Bonanza Books, 1967), p 109, describes them as: "Amazing engines, they hauled ore on the iron range, hustled time freights on the Kalispell Division and served in heavy duty passenger service on troop trains." On the latter service, Wood quotes Mr. J S Miller, Assistant to the Superintendent of Motive Power in 1945/46 as saying that N-3s could "...run like a deer" and hit speeds of 50-60 mph.

Virtually all of the class was retired in 1955.

Specifications
Class	N-1	N-2	N-3
Locobase ID	307	2802	6445
Railroad	Great Northern (GN)	Great Northern (GN)	Great Northern (GN)
Whyte	2-8-8-0	2-8-8-0	2-8-8-0
Road Numbers	2000-2024	2000-2024	2000-2024
Gauge	Std	Std	Std
Builder	GNR	GNR	GNR
Year	1912	1925	1940
Valve Gear	Walschaert	Walschaert	Walschaert
	Locomotive Length and Weight
Driver Wheelbase	16.50'	16.50'	16.50'
Engine Wheelbase	45.25'	43.25'	43'
Ratio of driving wheelbase to overall engine wheebase	0.36	0.38	0.38
Overall Wheelbase (engine & tender)	52.50'	98'	99.67'
Axle Loading (Maximum Weight per Axle)	52500 lbs	52500 lbs	67235 lbs
Weight on Drivers	420000 lbs	420000 lbs	537880 lbs
Engine Weight	450000 lbs	450000 lbs	572375 lbs
Tender Light Weight	150000 lbs	365400 lbs	372700 lbs
Total Engine and Tender Weight	600000 lbs	815400 lbs	945075 lbs
Tender Water Capacity	8000 gals	21500 gals	22000 gals
Tender Fuel Capacity (oil/coal)	13 tons	24 tons	5800 gals
Minimum weight per yard of rail on which locomotive could run	87.50 lb rail	87.50 lb rail	112.06 lb rail
	Geometry Relating to Tractive Effort
Driver Diameter	63"	63"	63"
Boiler Pressure	210 psi	210 psi	265 psi
Cylinders (dia x stroke)	28" x 32"	25" x 32" (4)	22" x 32" (4)
Low Pressure Cylinders (dia x stroke)	42" x 32"	" x "	" x "
Tractive Effort	98422 lbs	113333 lbs	110751 lbs
Factor of Adhesion (Weight on Drivers/Tractive Effort)	4.27	3.71	4.86
	Heating Ability
Firebox Area	326 sq. ft	245 sq. ft	483 sq. ft
Grate Area	78.40 sq. ft	78.40 sq. ft	95 sq. ft
Evaporative Heating Surface	6470	5837	5805
Superheating Surface	1430	1868	2188
Combined Heating Surface	7900	7705	7993
Evaporative Heating Surface/Cylinder Volume	283.70	160.53	206.16
	Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation	16464	16464	25175
Same as above plus superheater percentage	19444.19	20455.53	32066.39
Same as above but substitute firebox area for grate area	80852.13	63923.54	163032.29
Power L1	9011.19	14477.64	27581.93
Power MT	378.40	607.96	904.41