Great Northern 4-8-4 "Northern" Type Locomotives

Class S-1 (Locobase 261)

Data from 1930 Locomotive Cyclopedia. Belpaire firebox had combustion chamber that contributed 108 sq ft to the firebox heating surface.

Its boiler fitted with exhaust steam injector. Heavy dual-service oil-burning engines. Only six built (works #60781-60782, 60807-60810 in April & May 1929) before design changed to lighter engine with high drivers.

They were nonetheless highly serviceable locomotives that remained in service until 1956 (2553), 1957, and 1958.

Class S-2 (Locobase 262)

Data taken from Great Northern locomotive diagram reproduced on Ben Ringnalda's http://www.greatnorthernempire.net/index2.htm?GNEGN_S2_Class.htm website, last accessed 16 February 2007. It differs slightly from the 1930 Locomotive Cyclopedia specs.

Baldwin supplied these in February and March 1930 (61211-61216, 61224-61225, 61237-61242).

To save weight, the GN eschewed their by-then standard Belpaire firebox in favor of a radial-stayed firebox. This large cavity had a combustion chamber (111 sq ft) and arch tubes (22 sq ft). The boiler was fitted with exhaust steam injector. The S-2 had high drivers and smaller boiler than the earlier S-1 and was more completely dedicated to express passenger service. Another change was the squaring of the cylinder dimensions so that diameter equalled stroke. This resulted in slightly more cylinder volume.

Like their predecessors, the S-2s were oil-fired.

Specifications
Class	S-1	S-2
Locobase ID	261	262
Railroad	Great Northern (GN)	Great Northern (GN)
Whyte	4-8-4	4-8-4
Road Numbers	2550-2555	2575-2588
Gauge	Std	Std
Builder	Baldwin	Baldwin
Year	1929	1930
Valve Gear	Walschaert	Walschaert
	Locomotive Length and Weight
Driver Wheelbase	19'	20.75'
Engine Wheelbase	45.50'	47.75'
Ratio of driving wheelbase to overall engine wheebase	0.42	0.43
Overall Wheelbase (engine & tender)	94.90'	91.17'
Axle Loading (Maximum Weight per Axle)
Weight on Drivers	273700 lbs	257000 lbs
Engine Weight	472120 lbs	438120 lbs
Tender Light Weight	375780 lbs	326560 lbs
Total Engine and Tender Weight	847900 lbs	764680 lbs
Tender Water Capacity	22000 gals	17250 gals
Tender Fuel Capacity (oil/coal)	5800 gals	5800 gals
Minimum weight per yard of rail on which locomotive could run	114.04 lb rail	107.08 lb rail
	Geometry Relating to Tractive Effort
Driver Diameter	73"	80"
Boiler Pressure	250 psi	225 psi
Cylinders (dia x stroke)	28" x 30"	29" x 29"
Tractive Effort	68466 lbs	58305 lbs
Factor of Adhesion (Weight on Drivers/Tractive Effort)	4.00	4.41
	Heating Ability
Firebox Area	401 sq. ft	401 sq. ft
Grate Area	102 sq. ft	97.75 sq. ft
Evaporative Heating Surface	5405	4803
Superheating Surface	2265	2265
Combined Heating Surface	7670	7068
Evaporative Heating Surface/Cylinder Volume	252.80	216.64
	Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation	25500	21993.75
Same as above plus superheater percentage	33030.31	29041.83
Same as above but substitute firebox area for grate area	129854.47	119138.36
Power L1	39542.57	36796.65
Power MT	1274.04	1262.61