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 standardisation 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 Wheelarrangement Drivingwheel spacing Wheel diameters Cylinders Standardboiler no. Boilerpressure Tractiveeffort Numbering Refs Leading Driving Trailing Bore StrokeProposed 4-6-0 Churchward 19014-6-0 3 ft 3 in 6 ft 8 in18 in 30 in Prop 1 Proposed 4-6-0 Churchward 19014-6-0 3 ft 3 in 5 ft 8 in18 in 30 in Prop 1 Proposed 4-4-2T Churchward 19014-4-2T 3 ft 3 in 6 ft 8 in 3 ft 3 in18 in 30 in Prop 2 Proposed 4-4-0 Churchward 19014-4-0 3 ft 3 in 6 ft 8 in18 in 30 in Prop 2 Proposed 2-8-0 Churchward 19012-8-0 3 ft 3 in 4 ft 7 in18 in 30 in Prop 1 Proposed 2-6-2T Churchward 19012-6-2T 3 ft 3 in 5 ft 8 in 3 ft 3 in18 in 30 in Prop 2 2900 Saint Churchward 19024-6-0 7 ft / 7 ft 9 in 3 ft 2 in 6 ft 8 in 18 in 30 in 1 225 psi 24,395 lbf 2900-2955; 2971-2990; 2998 2800, 2884 Churchward 19032-8-0 5 ft 5 in / 5 ft 5 in / 6 ft 3 ft 2 in 4 ft 7 in 18 in 30 in 1 225 psi 35,380 lbf 28xx, 3800-66 3100 (1903) Churchward 19032-6-2T 7 ft / 7 ft 9 in 3 ft 2 in 5 ft 8 in 3 ft 8 in18 in 30 in 2 200 psi 24,300 lbf 3100, 3111-49; later renumbered 5100, 5111-49 3800 County Churchward 19044-4-0 8 ft 6 in 3 ft 2 in 6 ft 8 in 18 in 30 in 4 200 psi 20,530 lbf 3473-82; renumbered 3800-39 4400 Churchward 19042-6-2T 6 ft / 5 ft 6 in 3 ft 2 in 4 ft 1 in 3 ft 2 in16 in 24 in 5 180 psi 20,195 lbf 4400-10 2221 County Tank Churchward 19054-4-2T 8 ft 6 in 3 ft 2 in 6 ft 8 in 3 ft 8 in18 in 30 in 2 200 psi 20,530 lbf 2221-50 4500, 4575 Churchward 19062-6-2T 5 ft 6 in / 6 ft 3 ft 2 in 4 ft 7 in 3 ft 2 in17 in 24 in 5 200 psi 21,250 lbf 2161-90; later renumbered 45xx, 5500-74 3150 Churchward 19062-6-2T 7 ft / 7 ft 9 in 3 ft 2 in 5 ft 8 in 3 ft 8 in18 in 30 in 4 200 psi 25,670 lbf 3150-90 4200 Churchward 19102-8-0T 7 ft / 6 ft / 7 ft 3 ft 2 in 4 ft 7 in18 in 30 in 4 200 psi 31,450 lbf 42xx, 5200-04 4300 Mogul Churchward 19112-6-0 7 ft / 7 ft 9 in 3 ft 2 in 5 ft 8 in18 in 30 in 4 200 psi 25,670 lbf 43xx, 53xx, 63xx, 7300-21, 9300-21 4600 Churchward 19134-4-2T 7 ft 3 ft 2 in 5 ft 8 in 3 ft 2 in17 in 24 in 5 200 psi 18,360 lbf 4600 4700 Churchward 19192-8-0 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 19232-8-0T 7 ft / 6 ft / 7 ft 3 ft 2 in 4 ft 7 in19 in 30 in 4 200 psi 33,170 lbf 5205-64 4900 Hall Collett 19244-6-0 7 ft / 7 ft 9 in 3 ft 6 ft 18 in 30 in 1 225 psi 27,275 lbf 49xx, 59xx, 6900-58 5101 Collett 19292-6-2T 7 ft / 7 ft 9 in 3 ft 2 in 5 ft 8 in 3 ft 8 in18 in 30 in 2 200 psi 24,300 lbf 5101-10, 5150-99, 4100-79 6100 Collett 19312-6-2T 7 ft / 7 ft 9 in 3 ft 2 in 5 ft 8 in 3 ft 8 in18 in 30 in 2 225 psi 27,340 lbf 6100-69 7200 Collett 19342-8-2T 7 ft / 6 ft / 7 ft 3 ft 2 in 4 ft 7 in 3 ft 8 in19 in 30 in 4 200 psi 33,170 lbf 7200-53 6800 Grange Collett 19364-6-0 7 ft / 7 ft 9 in 3 ft 5 ft 8 in 18 in 30 in 1 225 psi 28,875 lbf 6800-79 7800 Manor Collett 19384-6-0 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 19382-6-2T 7 ft / 7 ft 9 in 3 ft 5 ft 6 in 3 ft 8 in18 in 30 in 2 225 psi 28,165 lbf 8100-09 3100 (1938) Collett 19382-6-2T 7 ft / 7 ft 9 in 3 ft 5 ft 3 in 3 ft 8 in18 in 30 in 4 225 psi 31,170 lbf 3100-04 6959 Modified Hall Hawksworth 19444-6-0 7 ft / 7 ft 9 in 3 ft 6 ft 18 in 30 in 1 225 psi 27,275 lbf 6959-99, 7900-29 1000 County Hawksworth 19454-6-0 7 ft / 7 ft 9 in 3 ft 6 ft 3 in 18 in 30 in 15 280 psi 32,580 lbf 1000-29 9351 WSR Mogul WSR 20042-6-0 7 ft / 7 ft 9 in 3 ft 2 in 5 ft 8 in18 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

Notes

References