GWR Standard Classes with two outside cylinders

George Jackson Churchward created for the Great Western Railway a family of standard classes of locomotive, based on a limited set of shared dimensions and components, and his principles were followed by his successors. Most of these locomotives had two cylinders, placed outside the frames, and they are listed here, ranging in size from small-wheeled 2-6-2T tank locos to 2-8-0 express freight engines.
==History of standardization==
Standardisation on the GWR started with Daniel Gooch, its first Locomotive Superintendent, who enforced uniformity on third-party suppliers of parts by issuing lithographed copies of drawings and iron templates to check accurate fitting. This was carried through once the GWR built its own works at Swindon, and standard parts were also shared by different classes of locomotive. Joseph Armstrong (and his brother George) used similar techniques at Wolverhampton, and continued Gooch's policy when he replaced him at Swindon. William Dean, Armstrong's successor, designed (among others) four classes of locomotive, 2-4-0 and 0-6-0 tender and tank engines, which shared many standard components. However, it was Churchward who carried the policy to lengths which made GWR locomotives distinctive and shaped their development until the nationalisation of the railways.
Even before Churchward succeeded Dean as Locomotive Superintendent in 1902, he had in 1901 published a list of proposed new locomotive classes of a revolutionary nature. He began by designing a range of standard components, then constructed a variety of locomotive designs of different sizes and purposes around these items. These locomotives were to have two outside cylinders, inside frames and motion, generous piston valves, and identical left/right cylinder castings, and they shared three coupled wheel sizes, two standard boilers and a single size of leading/trailing wheel. When Churchward took over the job, he began to create prototypes to test and evaluate his ideas, and they were developed into a series of locomotive classes that appeared throughout Churchward's time in office, and were further developed and expanded by both Charles Collett and Frederick Hawksworth, his successors up to the end of the GWR. Indeed, the proposed 4-6-0 with 5 ft 8 in driving wheels did not appear until Collett built the Granges in 1936. Even after the GWR ceased to exist, a new 'class' of Mogul was developed on the West Somerset Railway.
==Comparison of locomotive classes==
This table summarises the classes that developed from Churchward's proposals. It is simplified in that it suggests the classes were sets of identical engines, whereas the prototypes often differed in some respects from later class members, and there was a constant move to improve the locomotives by changing boilers, enlarging cylinders and tweaking other details of their construction. By and large, the details and dimensions given were common to most members of the class in their final form. The details of Churchward's original proposed locomotives and boilers are shaded; no classes were built to exactly those dimensions. However, the proposed classes will sort adjacent to the most closely matching real classes. The WSR Mogul is shaded pink.
This table does not include
*the 4-cylinder classes - Stars, Castles and Kings
*similar looking inside-cylinder classes - 3901 2-6-2Ts, 5600 0-6-2Ts, and 2251 0-6-0s
*non-standard classes - outside-cylindered ex-ROD 3000 2-8-0s
GWR standard classes with two outside cylinders
Class 	CME 	Year	Wheel
arrangement	Driving
wheel spacing 	Wheel diameters	Wheel diameters 	Wheel diameters	Cylinders	Cylinders	Standard
boiler no.	Boiler
pressure	Tractive
effort	Numbering
Class 	CME 	Year	Wheel
arrangement	Driving
wheel spacing 	Leading 	Driving 	Trailing 	Bore 	Stroke 	Standard
boiler no.	Boiler
pressure	Tractive
effort	Numbering
Proposed 4-6-0 	Churchward	1901	4-6-0 	 	3 ft 3 in 	6 ft 8 +1⁄2 in	 	18 in 	30 in 	Prop 1	 	 	
Proposed 4-6-0 	Churchward	1901	4-6-0 	 	3 ft 3 in 	5 ft 8 in 	 	18 in 	30 in 	Prop 1	 	 	
Proposed 4-4-2T 	Churchward	1901	4-4-2T	 	3 ft 3 in 	6 ft 8+1⁄2 in 	3 ft 3 in 	18 in 	30 in 	Prop 2	 	 	
Proposed 4-4-0 	Churchward	1901	4-4-0 	 	3 ft 3 in 	6 ft 8+1⁄2 in 	 	18 in 	30 in 	Prop 2	 	 	
Proposed 2-8-0 	Churchward	1901	2-8-0 	 	3 ft 3 in 	4 ft 7+1⁄2 in 	 	18 in 	30 in 	Prop 1	 	 	
Proposed 2-6-2T 	Churchward	1901	2-6-2T	 	3 ft 3 in 	5 ft 8 in 	3 ft 3 in 	18 in 	30 in 	Prop 2	 	 	
2900 Saint 	Churchward	1902	4-6-0 	7 ft / 7 ft 9 in 	3 ft 2 in 	6 ft 8+1⁄2 in 	 	18+1⁄2 in	30 in 	1 	225 psi	24,395 lbf	2900-2955; 2971-2990; 2998
2800, 2884 	Churchward	1903	2-8-0 	5 ft 5 in / 5 ft 5 in / 6 ft	3 ft 2 in 	4 ft 7+1⁄2 in 	 	18+1⁄2 in	30 in 	1 	225 psi	35,380 lbf	28xx, 3800-66
3100 (1903) 	Churchward	1903	2-6-2T	7 ft / 7 ft 9 in 	3 ft 2 in 	5 ft 8 in 	3 ft 8 in 	18 in 	30 in 	2 	200 psi	24,300 lbf	3100, 3111-49; later renumbered 5100, 5111-49
3800 County 	Churchward	1904	4-4-0 	8 ft 6 in 	3 ft 2 in 	6 ft 8+1⁄2 in 	 	18 in 	30 in 	4 	200 psi	20,530 lbf	3473-82; renumbered 3800-39
4400 	Churchward	1904	2-6-2T	6 ft / 5 ft 6 in 	3 ft 2 in 	4 ft 1+1⁄2 in 	3 ft 2 in 	16+1⁄2 in	24 in 	5 	180 psi	20,195 lbf	4400-10
2221 County Tank 	Churchward	1905	4-4-2T	8 ft 6 in 	3 ft 2 in 	6 ft 8+1⁄2 in 	3 ft 8 in 	18 in 	30 in 	2 	200 psi	20,530 lbf	2221-50
4500, 4575 	Churchward	1906	2-6-2T	5 ft 6 in / 6 ft 	3 ft 2 in 	4 ft 7+1⁄2 in 	3 ft 2 in 	17 in 	24 in 	5 	200 psi	21,250 lbf	2161-90; later renumbered 45xx, 5500-74
3150 	Churchward	1906	2-6-2T	7 ft / 7 ft 9 in 	3 ft 2 in 	5 ft 8 in 	3 ft 8 in 	18+1⁄2 in	30 in 	4 	200 psi	25,670 lbf	3150-90
4200 	Churchward	1910	2-8-0T	7 ft / 6 ft / 7 ft 	3 ft 2 in 	4 ft 7+1⁄2 in 	 	18+1⁄2 in	30 in 	4 	200 psi	31,450 lbf	42xx, 5200-04
4300 Mogul 	Churchward	1911	2-6-0 	7 ft / 7 ft 9 in 	3 ft 2 in 	5 ft 8 in 	 	18+1⁄2 in	30 in 	4 	200 psi	25,670 lbf	43xx, 53xx, 63xx, 7300-21, 9300-21
4600 	Churchward	1913	4-4-2T	7 ft 	3 ft 2 in 	5 ft 8 in 	3 ft 2 in 	17 in 	24 in 	5 	200 psi	18,360 lbf	4600
4700 	Churchward	1919	2-8-0 	6 ft 6 in / 6 ft 6 in / 7 ft	3 ft 2 in 	5 ft 8 in 	 	19 in 	30 in 	7 	225 psi	30,460 lbf	4700-08
5205 	Collett 	1923	2-8-0T	7 ft / 6 ft / 7 ft 	3 ft 2 in 	4 ft 7+1⁄2 in 	 	19 in 	30 in 	4 	200 psi	33,170 lbf	5205-64
4900 Hall 	Collett 	1924	4-6-0 	7 ft / 7 ft 9 in 	3 ft 	6 ft 	 	18+1⁄2 in	30 in 	1 	225 psi	27,275 lbf	49xx, 59xx, 6900-58
5101 	Collett 	1929	2-6-2T	7 ft / 7 ft 9 in 	3 ft 2 in 	5 ft 8 in 	3 ft 8 in 	18 in 	30 in 	2 	200 psi	24,300 lbf	5101-10, 5150-99, 4100-79
6100 	Collett 	1931	2-6-2T	7 ft / 7 ft 9 in 	3 ft 2 in 	5 ft 8 in 	3 ft 8 in 	18 in 	30 in 	2 	225 psi	27,340 lbf	6100-69
7200 	Collett 	1934	2-8-2T	7 ft / 6 ft / 7 ft 	3 ft 2 in 	4 ft 7+1⁄2 in 	3 ft 8 in 	19 in 	30 in 	4 	200 psi	33,170 lbf	7200-53
6800 Grange 	Collett 	1936	4-6-0 	7 ft / 7 ft 9 in 	3 ft 	5 ft 8 in 	 	18+1⁄2 in	30 in 	1 	225 psi	28,875 lbf	6800-79
7800 Manor 	Collett 	1938	4-6-0 	7 ft / 7 ft 9 in 	3 ft 	5 ft 8 in 	 	18 in 	30 in 	14 	225 psi	27,340 lbf	7800-19
8100 	Collett 	1938	2-6-2T	7 ft / 7 ft 9 in 	3 ft 	5 ft 6 in 	3 ft 8 in 	18 in 	30 in 	2 	225 psi	28,165 lbf	8100-09
3100 (1938) 	Collett 	1938	2-6-2T	7 ft / 7 ft 9 in 	3 ft 	5 ft 3 in 	3 ft 8 in 	18+1⁄2 in	30 in 	4 	225 psi	31,170 lbf	3100-04
6959 Modified Hall	Hawksworth	1944	4-6-0 	7 ft / 7 ft 9 in 	3 ft 	6 ft 	 	18+1⁄2 in	30 in 	1 	225 psi	27,275 lbf	6959-99, 7900-29
1000 County 	Hawksworth	1945	4-6-0 	7 ft / 7 ft 9 in 	3 ft 	6 ft 3 in 	 	181⁄2 in 	30 in 	15 	280 psi	32,580 lbf	1000-29
9351 WSR Mogul 	WSR 	2004	2-6-0 	7 ft / 7 ft 9 in 	3 ft 2 in 	5 ft 8 in 	 	18 in 	30 in 	2 	200 psi	24,300 lbf	9351
==List of boilers==
The history of GWR boilers is long and complex. This table lists only the principal dimensions of the boilers (including proposed boilers) mentioned in the table of standard classes.
Selected GWR boilers
Boiler number	Length 	Firebox length 	Rear diameter 	Front diameter
Prop 1 	15 ft 	9 ft 	5 ft 	
Prop 2 	11 ft 2 in 	8 ft 8 in 	5 ft 	
1 	14 ft 10 in	9 ft 	5 ft 6 in	4 ft 11 in
2 	11 ft 	7 ft 	5 ft 	4 ft 5 in
4 	11 ft 	7 ft 	5 ft 6 in	4 ft 11 in
5 	10 ft 6 in 	5 ft 10 in	4 ft 9 in	4 ft 2 in
7 	14 ft 10 in	10 ft 	6 ft 	5 ft 6 in
14 	12 ft 6 in 	8 ft 8 in 	5 ft 3 in	4 ft 8 in
15 	12 ft 7 in 	9 ft 9 in 	5 ft 8 in	5 ft
Category:Lists
Category:GWR Standard Class Locomotives
Category:Great Western Railway locomotives
Category:Steam locomotives