Chicago Great Western 4-6-2 "Pacific" Locomotives in 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 Rail Data Exchange.

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 15,917 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 Wheelbase (ft / m)12.50 / 3.8112.50 / 3.8112.50 / 3.8112.50 / 3.8113 / 3.96
Engine Wheelbase (ft / m)33.50 / 10.2133.80 / 10.3033.80 / 10.3033.80 / 10.3034.50 / 10.52
Ratio of driving wheelbase to overall engine wheebase 0.37 0.37 0.37 0.37 0.38
Overall Wheelbase (engine & tender) (ft / m)53.80 / 16.4059.77 / 18.2259.80 / 18.2359.80 / 18.2363.33 / 19.30
Axle Loading (Maximum Weight per Axle) (lbs / kg)
Weight on Drivers (lbs / kg)121,500 / 55,112122,100 / 55,384125,700 / 57,017124,800 / 56,608140,000 / 63,503
Engine Weight (lbs / kg)191,200 / 86,727197,440 / 89,557190,700 / 86,500197,600 / 89,630216,000 / 97,976
Tender Loaded Weight (lbs / kg)122,560 / 55,592122,560 / 55,592122,560 / 55,592122,560 / 55,592144,200 / 65,408
Total Engine and Tender Weight (lbs / kg)313,760 / 142,319320,000 / 145,149313,260 / 142,092320,160 / 145,222360,200 / 163,384
Tender Water Capacity (gals / ML)6125 / 23.206125 / 23.206125 / 23.206125 / 23.208000 / 30.30
Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT)11 / 1011 / 1011 / 1011 / 1011 / 10
Minimum weight of rail (calculated) (lb/yd)6868706978
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)68 / 172769 / 175368 / 172768 / 172768 / 1727
Boiler Pressure (psi / kPa)175 / 12.10180 / 12.40200 / 13.80190 / 13.10180 / 12.40
High Pressure Cylinders (dia x stroke) (in / mm)22" x 26" / 559x66022" x 26" / 559x66020" x 26" / 508x66020.5" x 26" / 521x66024" x 26" / 610x660
Tractive Effort (lbs / kg)27,528 / 12486.5127,904 / 12657.0626,000 / 11793.4225,950 / 11770.7433,696 / 15284.27
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.41 4.38 4.83 4.81 4.15
Heating Ability
Firebox Area (sq ft / m2)157 / 14.59157.80 / 14.66157 / 14.59157.80 / 14.67191.80 / 17.82
Grate Area (sq ft / m2)40.10 / 3.7340.10 / 3.7340.10 / 3.7340.10 / 3.7349.30 / 4.58
Evaporative Heating Surface (sq ft / m2)2506 / 232.902235 / 207.642600 / 241.642325 / 216.083171 / 294.59
Superheating Surface (sq ft / m2)446 / 41.45494 / 45.89494 / 45.91615 / 57.13
Combined Heating Surface (sq ft / m2)2952 / 274.352729 / 253.532600 / 241.642819 / 261.993786 / 351.72
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 percentage807085178020899010,294
Same as above but substitute firebox area for grate area31,59633,51731,40035,37940,048
Power L112,66513,517811616,39014,483
Power MT689.42732.18427.03868.60684.20

Specifications by Steve Llanso of Sweat House Media
ClassK4SK5sK6s
Locobase ID15,918 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 Wheelbase (ft / m)13 / 3.9613 / 3.9611.33 / 3.45
Engine Wheelbase (ft / m)34.50 / 10.5235.33 / 10.7732 / 9.75
Ratio of driving wheelbase to overall engine wheebase 0.38 0.37 0.35
Overall Wheelbase (engine & tender) (ft / m)63.33 / 19.3066 / 20.1259.09 / 18.01
Axle Loading (Maximum Weight per Axle) (lbs / kg)
Weight on Drivers (lbs / kg)139,500 / 63,503152,400 / 69,128136,950 / 62,120
Engine Weight (lbs / kg)217,200 / 97,976256,450 / 116,324211,170 / 95,785
Tender Loaded Weight (lbs / kg)146,200 / 65,408158,000 / 71,668118,080 / 53,560
Total Engine and Tender Weight (lbs / kg)363,400 / 163,384414,450 / 187,992329,250 / 149,345
Tender Water Capacity (gals / ML)8000 / 30.308000 / 30.306000 / 22.73
Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT)11 / 1013 / 11.809 / 8.20
Minimum weight of rail (calculated) (lb/yd)788576
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)73 / 172773 / 185463 / 1600
Boiler Pressure (psi / kPa)200 / 12.40190 / 13.10200 / 13.80
High Pressure Cylinders (dia x stroke) (in / mm)21.5" x 26" / 610x66025" x 28" / 635x71121.5" x 28" / 546x711
Tractive Effort (lbs / kg)27,988 / 12695.1638,716 / 17561.3034,926 / 15842.19
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.98 3.94 3.92
Heating Ability
Firebox Area (sq ft / m2)193 / 17.82260 / 24.16167 / 15.52
Grate Area (sq ft / m2)49.30 / 4.5856 / 5.2049.30 / 4.58
Evaporative Heating Surface (sq ft / m2)3171 / 294.593732 / 346.842981 / 277.04
Superheating Surface (sq ft / m2)615 / 57.13794 / 73.79644 / 60.78
Combined Heating Surface (sq ft / m2)3786 / 351.724526 / 420.633625 / 337.82
Evaporative Heating Surface/Cylinder Volume290.25234.60253.37
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation986010,6409860
Same as above plus superheater percentage11,43812,55511,635
Same as above but substitute firebox area for grate area44,77658,29239,412
Power L121,54017,69617,156
Power MT1021.24767.97828.53

Reference