Chicago Great Western 2-6-2 "Prairie" Locomotives in the USA

Class 200C/F2 (Locobase 15915)

Data from CGW 7 - 1902 Locomotive Diagrams supplied in August 2013 by Allen Stanley from his extensive Rail Data Exchange. Works numbers were 25357-25376 in June 1902 and 25676-25681 in August.

A few Prairie roads used the 2-6-2 wheel arrangement for freight service. The usual reason given--the trailing axle allowed for a wider firebox--carries less force in these engines supplied from the Ocean State.

The entire class was superheated beginning in 1910; see Locobase 4157.

Class 200D/F3 (Locobase 4166)

Data from CGW 7 - 1902 Locomotive Diagrams supplied in August 2013 by Allen Stanley from his extensive Rail Data Exchange. Works numbers were 25682-25687 in August 1902.

Firebox heating surface includes 13 sq ft of arch tubes.

These freight Prairies proved to be the model for later simpling of other CGW 2-6-2 compounds, but were the only ones delivered as simple-expansion engines.

The sextet led interesting lives. Three--247-248, 250--were converted to compound Prairie mallets (2-6-6-2)--Locobase 16525)--with inside piston valves and Stephenson valve gear; 247, 248, 250 became 650-652 respectively. .

Later, all six became Pacific (4-6-2) class K6; see Locobase 4176.

Class 220B/F4 - compound (Locobase 9757)

Data from Angus Sinclair, "New Freight Engine for the Chicago Great Western", Railway and Locomotive Engineering, Volume XV [15], No. 5 (May 1902), p. 199-201. See also CGW 1904 Locomotive Diagrams supplied in August 2013 by Allen Stanley from his extensive Rail Data Exchange and "Tandem Compound Locomotive for Chicago Great Western", Railway Age, Volume XXXIII [33], No 15 (11 April 1902), p. 618-620. (Thanks to Chris Hohl for his 27 July 2021 email noting the correct engine-and-tender wheelbase.) Works numbers were 25203-25222 in March 1902.

These mixed-traffic locomotives were built as tandem compounds, setups that placed the HP cylinder ahead of the LP cylinder on the same axis. They burned Illinois and Iowa bituminous coal, according to Sinclair, which accounts for the large grate. The CGW described them as "Lake Shore" engines, but Sinclair thought that an unnecessary diversion because they were so obviously of the Prairie type. He proceeded to apply F M Whyte's new system of notation to their description.

The RA acknowledged that the chief objection to tandem compounds lay in the inaccessibility of the low-pressure cylinders in the rear to inspect or repair the packing rings in those cylinders. An "ingenious" modification to the design used an auxiliary cast-steel guide support that allowed "removal of the back head without disturbing the guides." The author conceded the downside to such advantage was the need for a long piston rod as the auxiliary guide prevented the builder from driving the locomotive through the middle set of drivers. This was unfortunate "especially when the wheels are of comparatively small diameter."

Other elements of the design were more favorably reviewed such as the "large number of steel castings" and the firebox's brick arch holding water tubes that contributed 25 sq ft (2.32 sq m) to the direct heating surface area. The castings list is indeed impressive for the time:"notably the equalizers and spring hanger supports, the links and link hangers, the lifting shaft, horizontal arm, as well as the vertical arm, the reverse lever and fulcrum, draw casting and the front truck center pin, guide casting, in addition to the parts ordinarily made 'of steel."

No tweak of the guide supports could disguise the fact that tandem compounds simply wouldn't do for most North American railroads. This class was converted to the simple-expansion engines shown in Locobase 4166.

NB: Although Chris Hohl reported that the tube count totalled 352, Locobase found that the 1904 CGW book reported 351.

Class 221B/F7A (Locobase 6121)

Data from 1943 CGW diagram book supplied by Allen Stanley from his extensive Rail Data Exchange in March 2004.

These Prairies had been built as compounds and later simpled; as such they are described in Locobase 4167. In the late 'teens, more than half were fitted with superheaters and radial valve gear. All but 255 had been simpled, but not superheated in 1911-1913; see Locobase 15914.

At that point, they had 11" piston valves and they retained the arch tubes that contributed 13 sq ft to the firebox heating surface.

Most were scrapped in the 1920s and early 1930s. 254, 264-255

Class 221E/F5 (Locobase 4168)

See [] for the original 1917 railroad diagrams.

Firebox heating surface includes 13 sq ft (1.21 sq m) of arch tubes. These had a slightly different heating surface/grate area ratio, but otherwise were very similar to the rest of the line of CGW Prairie engines. Half were later upgraded to F7 with the addition of superheaters and Walschaerts valve gear; see Locobase 6122.

Six of these saw steam out on the CGW.

Class F2S (Locobase 4157)

See [] for the original 1917 railroad diagrams.

Firebox heating surface includes 13 sq ft of arch tubes.

This engine class came on to the road as Alco cross-compounds, but simpled and superheated (with Vauclain superheaters) beginning in 1910 as shown in the above specifications. Cylinder volume increased but the class retained its slide valves and link motion. Boiler pressure plummeted by 50 psi (3.45 bar).

Alone among the CGW's Prairies, the class endured in using Vauclain superheaters. The 222, 230, and 241 had their cylinders bushed to 23" diameter with a concomitant increase in BP to 165 psi (11.4 bar)..

The F2S were retired in 1929-1930.

Class F4B (Locobase 15914)

See [] for the original 1917 railroad diagrams. Firebox heating surface includes 13 sq ft of arch tubes.

Like the F4S conversions shown in Locobase 4167,these freight Prairies entered service as compounds (Locobase 9757). They were simpled and used 12" (305 mm) piston valves, but kept the inside link motion. Unlike the F4S, these engines were not superheated in 1910-1914.

254-255, 264-265, 267-268, and 270-272 were redesignated F-7A after being modified with Schmidt superheaters and Walschaerts valve gear in 1919-1920; see Locobase 6121. Some of these remained in service until 1950.

Class F4S (Locobase 4167)

Data from CGW 1917 Locomotive Diagram book supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange.

Firebox heating surface includes 13 sq ft of arch tubes.

These freight Prairies entered service as compounds (Locobase 9757), but were simpled and superheated with Vauclain superheaters beginning in 1910. They also received larger-volume cylinders with 12" (305 mm) piston valves, but kept the inside link motion. The Vauclain superheaters were deliberately designed as low-temperature installations and contributed little to energizing boiler steam.

Eleven were redesignated F-7 after being modified with Schmidt superheaters and Walschaerts valve gear. Some of these remained in service until 1950.

Class F5S (Locobase 4169)

See [] for the original 1917 railroad diagrams.

Originally delivered as tandem compounds by Brooks in 1903 (Locobase 4168), this class was updated with Schmidt Type A superheaters in 1916-1919. The firebox heating surface includes 13 sq ft (1.21 sq m) of arch tubes.

Several F5 and F5s also received Walschaert constant-lead radial valve gear; designated F7B, these appear in Locobase 6122.

Class F6 (Locobase 4170)

Data from CGW 1904 Locomotive Diagrams supplied in August 2013 by Allen Stanley from his extensive Rail Data Exchange. See also [] for the original 1917 railroad diagrams. Works numbers were 26471-26490 in February 1903.

Firebox heating surface includes 11 sq ft (1 sq m) of arch tubes. Part of the big run of Prairies built for the CGW by Brooks in 1903. These differ from the others, however, in their bigger boilers, smaller grates, taller drivers, and lower weight. Like the F1s, these were intended for passenger service, likely on some light rail.

They were converted to Pacifics (K1-K3) beginning in 1910.

Class F7B (Locobase 6122)

Data from 1943 CGW diagram book supplied by Allen Stanley from his extensive Rail Data Exchange in March 2004.

Like the F4, the CGW's F5 Prairies were delivered as saturated, tandem-compound locomotives (Locobase 4168). Compared to the F4, the F5s had a deeper firebox, but they too had arch tubes that added 13 sq ft to the firebox heating surface.

A program to fit F5s with Schmidt superheatedrs began in 1916 (F5S, see Locobase 6122), but several of those and several still operating with saturated boilers were given radial valve gear, superheated (279, 282-283, 289, and 292), larger cylinders fed by 11" (279 mm) piston valves in 1919-1923.

The refit definitely extended the class's usefulness; 6 remained in service until 1950.