Great Northern 4-4-2 "Atlantic" Locomotives of the USA

Class Details by Steve Llanso of Sweat House Media

Class K-1 (Locobase 6945)

Data from GN 1916 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Raildata collection. (Thanks to Chris Hohl for his comments on this class's tender capacity in his 18 February 2015 email.) Works numbers were 28037-28038 in April 1906; 28078, 28092, 28107-28108, 28148, 28162, 28198, 28270 in May.

Drury (1993) notes that these were delivered in 1906 as balanced-compound engines. The 15" HP cylinders sat inside the frame and drove the first coupled axle; the 25" LP cylinders sat outside and drove the second. Drury's observation about their 73" drivers suggesting no great turn of speed bears remembering when the basic idea of the 4-4-2 arrangement was to provide more power to express passenger trains.

GN superheated these engines before 1916 beginning with 1706-1707. They were later simpled beginning in 1924; see Locobase 6944.

Class K-1-S (Locobase 6944)

Data from GN 1 -1929 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Raildata collection.

When the GN converted their only Atlantics from balanced compounds (Locobase 6945) to simple-expansion engines beginning in 1924, they created some big-boilered engines that got their steam through rather sizable 15" (381 mm) piston valves. (1709 was shown in a 1946 diagram book to have 10" piston valves; that seems very small.) The class retained its Belpaire fireboxes.

In the process, the road gained a set of useful, mid-sized passenger engines, albeit ones with pretty high axle loadings. At least one remained in service through World War II. The GN also rebuilt the Spokane, Portland & Seattle's ten compounds and these served the SP & S until retired in 1937-1949.

Specifications by Steve Llanso of Sweat House Media
Locobase ID6945 6944
RailroadGreat Northern (GN)Great Northern (GN)
Number in Class1010
Road Numbers1700-17091700-1709
Number Built10
BuilderBurnham, Williams & CoGN
Valve GearWalschaertWalschaert
Locomotive Length and Weight
Driver Wheelbase 7.12' 7.12'
Engine Wheelbase30.37'31.62'
Ratio of driving wheelbase to overall engine wheebase 0.23 0.23
Overall Wheelbase (engine & tender)62.83'62.83'
Axle Loading (Maximum Weight per Axle)50000 lbs62450 lbs
Weight on Drivers100000 lbs124900 lbs
Engine Weight208000 lbs227300 lbs
Tender Light Weight160000 lbs169560 lbs
Total Engine and Tender Weight368000 lbs396860 lbs
Tender Water Capacity8000 gals8000 gals
Tender Fuel Capacity (oil/coal)13 tons4500 gals
Minimum weight of rail (calculated)83 lb/yard104 lb/yard
Geometry Relating to Tractive Effort
Driver Diameter73"73"
Boiler Pressure210 psi200 psi
High Pressure Cylinders (dia x stroke)15" x 26"21" x 26"
Low Pressure Cylinders (dia x stroke)25" x 26" (2)
Tractive Effort21036 lbs26702 lbs
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.75 4.68
Heating Ability
Firebox Area210.77 sq. ft211 sq. ft
Grate Area54.15 sq. ft54.15 sq. ft
Evaporative Heating Surface3489 sq. ft2696 sq. ft
Superheating Surface690 sq. ft
Combined Heating Surface3489 sq. ft3386 sq. ft
Evaporative Heating Surface/Cylinder Volume656.10258.66
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation1137210830
Same as above plus superheater percentage1137212996
Same as above but substitute firebox area for grate area4426250640
Power L1785823255
Power MT346.48820.95


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