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 (ft) 7.12 7.12
Engine Wheelbase (ft)30.3731.62
Ratio of driving wheelbase to overall engine wheebase 0.23 0.23
Overall Wheelbase (engine & tender) (ft)62.8362.83
Axle Loading (Maximum Weight per Axle) (lbs)50,00062,450
Weight on Drivers (lbs)100,000124,900
Engine Weight (lbs)208,000227,300
Tender Loaded Weight (lbs)160,000169,560
Total Engine and Tender Weight (lbs)368,000396,860
Tender Water Capacity (gals)80008000
Tender Fuel Capacity (oil/coal) (gals/tons)134500
Minimum weight of rail (calculated) (lb/yd)83104
Geometry Relating to Tractive Effort
Driver Diameter (in)7373
Boiler Pressure (psi)210200
High Pressure Cylinders (dia x stroke) (in)15" x 26"21" x 26"
Low Pressure Cylinders (dia x stroke) (in)25" x 26"
Tractive Effort (lbs)21,03626,702
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.75 4.68
Heating Ability
Firebox Area (sq ft)210.77211
Grate Area (sq ft)54.1554.15
Evaporative Heating Surface (sq ft)34892696
Superheating Surface (sq ft)690
Combined Heating Surface (sq ft)34893386
Evaporative Heating Surface/Cylinder Volume656.10258.66
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation11,37210,830
Same as above plus superheater percentage11,37212,996
Same as above but substitute firebox area for grate area44,26250,640
Power L1785823,255
Power MT346.48820.95


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