Chicago Great Western 4-6-2 "Pacific" Locomotives of the USA


Class Details by Steve Llanso of Sweat House Media

Class K1s (Locobase 4171)

See http://www.geocities.com/zvwrr/chicago_great_western_steam.html for the original 1917 railroad diagrams. Firebox heating surface includes 11 sq ft of arch tubes.

Originally delivered as F6 Prairies, these were converted to K1 Pacifics in 1910 and within a year all had received Vauclain superheaters, smaller cylinders, and been redesignated K1s.

Relatively modest in power, this group was retired in December 1929 (2) and 1932 (902, 905, 920). By that time, 902 had been fitted with Walschaert outside radial valve gear and been redesignated K2A.


Class K2A (Locobase 15917)

Data from CGW 1 1932 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Raildata collection.

Only a few years after the conversion of F6 Ten-wheelers to other Pacific classes (mostly the K3s shown in Locobase 4173), the CGW settled on outside radial valve gear, a Schmidt superheater (instead of the low-temperature Vauclaiin), and 22" cylinders.

Half of the class were scrapped in 1929-1932. The other six served the CGW through the Second World War before being scrapped in September 1949 (912 and 915) and the first half of 1950 (917, 916, 914, and 906, in that order).


Class K3A (Locobase 4172)

See http://www.geocities.com/zvwrr/chicago_great_western_steam.html for the original 1917 railroad diagrams. Firebox heating surface includes 11 sq ft of arch tubes.

When these F6 Prairies (Locobase 4070) were converted to Pacifics, they received 3' (914 mm) longer boilers and four more tubes as well as the bogie truck replacing the Bissell. Otherwise, they were essentially similar.

See K3s (Locobase 4173) for the superheated variety.


Class K3s (Locobase 4173)

See http://www.geocities.com/zvwrr/chicago_great_western_steam.html for the original 1917 railroad diagrams. Firebox heating surface includes 11 sq ft of arch tubes.

When the K3s conversions (from F6 Prairies) were superheated, this is what resulted. K3s engines had a slightly lower boiler pressure and less heating surface, but a high ratio of superheat offset the difference.

Further work on these ex-F6s led to most of them being redesignated K2A (Locobase 15917). Only 909-910, 913, and 918 remained K3s and these were all sold for scrap in 1932.


Class K4B (Locobase 4174)

See http://www.geocities.com/zvwrr/chicago_great_western_steam.html for the original 1917 railroad diagrams. Firebox heating surface includes 11 sq ft of arch tubes.

Originally delivered as F1 Prairies, these were converted to K4s Pacifics in 1911-1912 (Locobase 15918).

Almost ten years later, the three engines were set on 5 inch (127 mm) smaller drivers and had their boiler pressure setting dropped by 10 psi.

All three were scrapped in 1932.


Class K4S (Locobase 15918)

See http://www.geocities.com/zvwrr/chicago_great_western_steam.html for the original 1917 railroad diagrams. Firebox heating surface includes 11 sq ft of arch tubes.

Originally delivered as F1 Prairies, these were converted to K4s Pacifics in 1911-1912. The specs refer to the 923. 921-922 had 24" cylinders; piston valves measured 13" (331 mm) in diameter.

All three were converted to K4B with smaller drivers in 1921-1922; see Locobase 4174.


Class K5s (Locobase 4175)

See http://www.geocities.com/zvwrr/chicago_great_western_steam.html for the original 1917 railroad diagrams. Also see DeGolyer, Vol 50, pp. 171-+ and Vol 55, pp. 26+. Works numbers were 41000-41004 in December 1913 and 43781-43783 in 1916.

These were the first CGW Pacifics to be built as such. Five were produced by Baldwin in December 1913, three more followed in 1916 (43781-43783). Steam admission came through capacious 15" (381 mm) piston valves with a lap of 1" (2, lead of 3/16", and an exhaust clearance of 1/8". Firebox heating surface includes 33 sq ft (3.05 sq m) of arch tubes and a Gaines combustion chamber.

At least one was fitted with a thermic syphon (in 1928), which raised the total direct heating surface to 338 sq ft. The entire class had its boiler pressure raised to 200 psi (13.8 bar)

The first three were scrapped in 1932 while the others carried on until early 1950.


Class K6s (Locobase 4176)

See http://www.geocities.com/zvwrr/chicago_great_western_steam.html for the original 1917 railroad diagrams.

Firebox heating surface includes 13 sq ft (1.2 sq m) of arch tubes.

These engines started out as F3 Prairies, but were converted in 1915-1918. Three had an intermediate existence as 2-6-6-2 Prairie Mallets, but by 1918 all were 4-6-2s. In the process, they received boilers that were 3 ft (914 mm) longer.

With the scaling back of the CGW in the early 1930s, the entire class became redundant and was scrapped in 1932.

Specifications by Steve Llanso of Sweat House Media
ClassK1sK2AK3AK3sK4B
Locobase ID4171 15917 4172 4173 4174
RailroadChicago Great Western (CGW)Chicago Great Western (CGW)Chicago Great Western (CGW)Chicago Great Western (CGW)Chicago Great Western (CGW)
CountryUSAUSAUSAUSAUSA
Whyte4-6-24-6-24-6-24-6-24-6-2
Number in Class512863
Road Numbers902-905, 920901-902, 906-908, 911-912, 914-917, 919908-910, 912-913, 918901, 906-910, 912, 914-917921-923
GaugeStdStdStdStdStd
Number Built5
BuilderCGWCGWCGWCGWCGW
Year19101919191019181921
Valve GearStephensonWalschaertStephensonWalschaertWalschaert
Locomotive Length and Weight
Driver Wheelbase12.50'12.50'12.50'12.50'13'
Engine Wheelbase33.50'33.80'33.80'33.80'34.50'
Ratio of driving wheelbase to overall engine wheebase 0.37 0.37 0.37 0.37 0.38
Overall Wheelbase (engine & tender)53.80'59.77'59.80'59.80'63.33'
Axle Loading (Maximum Weight per Axle)
Weight on Drivers121500 lbs122100 lbs125700 lbs124800 lbs140000 lbs
Engine Weight191200 lbs197440 lbs190700 lbs197600 lbs216000 lbs
Tender Light Weight122560 lbs122560 lbs122560 lbs122560 lbs144200 lbs
Total Engine and Tender Weight313760 lbs320000 lbs313260 lbs320160 lbs360200 lbs
Tender Water Capacity6125 gals6125 gals6125 gals6125 gals8000 gals
Tender Fuel Capacity (oil/coal)11 tons11 tons11 tons11 tons11 tons
Minimum weight of rail (calculated)68 lb/yard68 lb/yard70 lb/yard69 lb/yard78 lb/yard
Geometry Relating to Tractive Effort
Driver Diameter68"69"68"68"68"
Boiler Pressure175 psi180 psi200 psi190 psi180 psi
Cylinders (dia x stroke)22" x 26"22" x 26"20" x 26"20.5" x 26"24" x 26"
Tractive Effort27528 lbs27904 lbs26000 lbs25950 lbs33696 lbs
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.41 4.38 4.83 4.81 4.15
Heating Ability
Firebox Area157 sq. ft157.80 sq. ft157 sq. ft157.80 sq. ft191.80 sq. ft
Grate Area40.10 sq. ft40.10 sq. ft40.10 sq. ft40.10 sq. ft49.30 sq. ft
Evaporative Heating Surface2506 sq. ft2235 sq. ft2600 sq. ft2325 sq. ft3171 sq. ft
Superheating Surface446 sq. ft494 sq. ft494 sq. ft615 sq. ft
Combined Heating Surface2952 sq. ft2729 sq. ft2600 sq. ft2819 sq. ft3786 sq. ft
Evaporative Heating Surface/Cylinder Volume219.07195.38275.02234.08232.93
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation70187218802076198874
Same as above plus superheater percentage807085178020899010294
Same as above but substitute firebox area for grate area3159633517314003537940048
Power L1126651351781161639014483
Power MT689.42732.18427.03868.60684.20

Specifications by Steve Llanso of Sweat House Media
ClassK4SK5sK6s
Locobase ID15918 4175 4176
RailroadChicago Great Western (CGW)Chicago Great Western (CGW)Chicago Great Western (CGW)
CountryUSAUSAUSA
Whyte4-6-24-6-24-6-2
Number in Class386
Road Numbers921-923925-932950-955
GaugeStdStdStd
Number Built8
BuilderCGWBaldwinCGW
Year191119131915
Valve GearWalschaertWalschaertWalschaert
Locomotive Length and Weight
Driver Wheelbase13'13'11.33'
Engine Wheelbase34.50'35.33'32'
Ratio of driving wheelbase to overall engine wheebase 0.38 0.37 0.35
Overall Wheelbase (engine & tender)63.33'66'59.09'
Axle Loading (Maximum Weight per Axle)
Weight on Drivers139500 lbs152400 lbs136950 lbs
Engine Weight217200 lbs256450 lbs211170 lbs
Tender Light Weight146200 lbs158000 lbs118080 lbs
Total Engine and Tender Weight363400 lbs414450 lbs329250 lbs
Tender Water Capacity8000 gals8000 gals6000 gals
Tender Fuel Capacity (oil/coal)11 tons13 tons9 tons
Minimum weight of rail (calculated)78 lb/yard85 lb/yard76 lb/yard
Geometry Relating to Tractive Effort
Driver Diameter73"73"63"
Boiler Pressure200 psi190 psi200 psi
Cylinders (dia x stroke)21.5" x 26"25" x 28"21.5" x 28"
Tractive Effort27988 lbs38716 lbs34926 lbs
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.98 3.94 3.92
Heating Ability
Firebox Area193 sq. ft260 sq. ft167 sq. ft
Grate Area49.30 sq. ft56 sq. ft49.30 sq. ft
Evaporative Heating Surface3171 sq. ft3732 sq. ft2981 sq. ft
Superheating Surface615 sq. ft794 sq. ft644 sq. ft
Combined Heating Surface3786 sq. ft4526 sq. ft3625 sq. ft
Evaporative Heating Surface/Cylinder Volume290.25234.60253.37
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation9860106409860
Same as above plus superheater percentage114381255511635
Same as above but substitute firebox area for grate area447765829239412
Power L1215401769617156
Power MT1021.24767.97828.53

Reference


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