Chicago Great Western 2-6-2 "Prairie" Type Locomotives

Class F2s (Locobase 4157)

See http://www.geocities.com/zvwrr/chicago_great_western_steam.html 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 a compound, but was later simpled and superheated (with Vauclain superheaters) as shown in the above specifications. Alone among the CGW's Prairies, the class endured in that wheel arrangement until they were retired in 1929-1930.

Class F3 (Locobase 4166)

See http://www.geocities.com/zvwrr/chicago_great_western_steam.html for the original 1917 railroad diagrams. Firebox heating surface includes 13 sq ft of arch tubes. These freight Prairies led interesting lives. Three were converted to compound Prairie mallets (2-6-6-2) with inside piston valves and Stephenson valve gear; 247, 248, 250 became 650-652 respectively. .

Later, all 6 became Pacific (4-6-2) class K6, which see.

Class F4 (Locobase 4167)

See http://www.geocities.com/zvwrr/chicago_great_western_steam.html for the original 1917 railroad diagrams. 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. Eleven were redesignated F-7 after being modified with Schmidt superheaters and Walschaerts valve gear. Some of these remained in service until 1950.

Class F4 - compound (Locobase 9757)

Data from Angus Sinclair, Railway and Locomotive Engineering, May 1902, p. 199.

These were built as tandem compounds that 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.

Before too long they were converted to the simple-expansion engines shown in Locobase 4166.

Class F5 (Locobase 4168)

See http://www.geocities.com/zvwrr/chicago_great_western_steam.html for the original 1917 railroad diagrams. Firebox heating surface includes 13 sq ft 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 F5s (Locobase 4169)

See http://www.geocities.com/zvwrr/chicago_great_western_steam.html for the original 1917 railroad diagrams. Firebox heating surface includes 13 sq ft of arch tubes. It's not clear from the 1917 plans whether these three engines were delivered with superheaters or whether this subclass represented the first 3 to be so treated a decade or so after delivery.

Class F6 (Locobase 4170)

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. 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) in the 'teens.

Class F7 (Locobase 6121)

Data from 1943 CGW diagram book supplied by Allen Stanley from his extensive collection 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. 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, although a few survived to 1950.

Class F7B (Locobase 6122)

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

Like the F4, the CGW's F5 Prairies were delivered as saturated locomotives and like the F4, several F5s were superheated, given radial valve gear, and larger cylinders in the late 'teens. 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.

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

Specifications
Class	F2s	F3	F4	F4 - compound	F5	F5s	F6	F7	F7B
Locobase ID	4157	4166	4167	9757	4168	4169	4170	6121	6122
Railroad	Chicago Great Western (CGW)	Chicago Great Western (CGW)	Chicago Great Western (CGW)	Chicago Great Western (CGW)	Chicago Great Western (CGW)	Chicago Great Western (CGW)	Chicago Great Western (CGW)	Chicago Great Western (CGW)	Chicago Great Western (CGW)
Whyte	2-6-2	2-6-2	2-6-2	2-6-2	2-6-2	2-6-2	2-6-2	2-6-2	2-6-2
Road Numbers	221-246	247-252	253-272	253-272	273-292	285-287	901-920	270-272	273, 275-6, 282, 289, 292
Gauge	Std	Std	Std	Std	Std	Std	Std	Std	Std
Builder	Rhode Island	Rhode Island	Brooks	Alco-Brooks	Brooks	Brooks	Brooks
Year		1902	1902	1902	1903		1903	1919	1917
Valve Gear	Stephenson	Stephenson	Stephenson	Stephenson	Stephenson	Stephenson	Stephenson	Walschaert	Walschaert
	Locomotive Length and Weight
Driver Wheelbase	11'	11.33'	11.33'	11.33'	11.33'	11.33'	12.50'	11.33'	11.33'
Engine Wheelbase	29.17'	29.20'	29.20'	29.17'	30.83'	30.83'	30.75'	29.17'	30.83'
Ratio of driving wheelbase to overall engine wheebase	0.38	0.39	0.39	0.39	0.37	0.37	0.41	0.39	0.37
Overall Wheelbase (engine & tender)	54.20'	54.20'	54.20'	54.75'	54.83'	54.83'	57.02'	57.90'	54.83'
Axle Loading (Maximum Weight per Axle)
Weight on Drivers	135500 lbs	141000 lbs	141000 lbs	133200 lbs	141000 lbs	147100 lbs	121500 lbs	147100 lbs	147100 lbs
Engine Weight	185500 lbs	188500 lbs	188500 lbs	191700 lbs	192300 lbs	196460 lbs	173300 lbs	196500 lbs	196500 lbs
Tender Light Weight	120000 lbs	120000 lbs	120000 lbs	120000 lbs	110000 lbs	110000 lbs	122560 lbs	160000 lbs	160000 lbs
Total Engine and Tender Weight	305500 lbs	308500 lbs	308500 lbs	311700 lbs	302300 lbs	306460 lbs	295860 lbs	356500 lbs	356500 lbs
Tender Water Capacity	6000 gals	6000 gals	6000 gals	6000 gals	6000 gals	6000 gals	6125 gals	6000 gals	6000 gals
Tender Fuel Capacity (oil/coal)	11 tons	11 tons	11 tons	11 tons	10 tons	10 tons	11 tons	14 tons	14 tons
Minimum weight per yard of rail on which locomotive could run	75 lb rail	78 lb rail	78 lb rail	74 lb rail	78 lb rail	82 lb rail	68 lb rail	82 lb rail	82 lb rail
	Geometry Relating to Tractive Effort
Driver Diameter	73"	63"	63"	63"	63"	63"	68"	63"	63"
Boiler Pressure	180 psi	200 psi	200 psi	200 psi	200 psi	200 psi	200 psi	190 psi	190 psi
Cylinders (dia x stroke)	24" x 28"	21" x 28"	21" x 28"	16" x 28"	21" x 28"	21.5" x 28"	20" x 26"	23" x 28"	23" x 28"
Tractive Effort	33803 lbs	33320 lbs	33320 lbs	29162 lbs	33320 lbs	34926 lbs	26000 lbs	37970 lbs	37970 lbs
Factor of Adhesion (Weight on Drivers/Tractive Effort)	4.01	4.23	4.23	4.57	4.23	4.21	4.67	3.87	3.87
	Heating Ability
Firebox Area	167 sq. ft	167 sq. ft	167 sq. ft	179 sq. ft	172 sq. ft	172 sq. ft	157 sq. ft	167 sq. ft	172 sq. ft
Grate Area	49 sq. ft	49.30 sq. ft	49.30 sq. ft	49.30 sq. ft	45 sq. ft	42 sq. ft	40.10 sq. ft	49.30 sq. ft	41.50 sq. ft
Evaporative Heating Surface	3238	3238	3238	3250	3248	2586	2506	2523	2528
Superheating Surface	385					526		526	526
Combined Heating Surface	3623	3238	3238	3250	3248	3112	2506	3049	3054
Evaporative Heating Surface/Cylinder Volume	220.86	288.47	288.47	498.78	289.36	219.79	265.08	187.38	187.75
	Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation	8820	9860	9860	9860	9000	8400	8020	9367	7885
Same as above plus superheater percentage	9790	9860	9860	9860	9000	9828	8020	10959	9225
Same as above but substitute firebox area for grate area	33367	33400	33400	35800	34400	40248	31400	37124	38236
Power L1	11260	7620	7620	4362	7686	14600	7891	11990	12034
Power MT	549.61	357.43	357.43	216.59	360.53	656.44	429.55	539.09	541.07