|Introduced||1902 – 1913|
|Weight – Loco||72t 0cwt|
|Driving Wheels||6ft 8.5ins|
|Boiler Pressure||225psi superheated|
|Cylinders||Outside – 18.5in x 30in|
|Valve Gear||Stephenson (piston valve)|
Between 1897 and 1902 when Churchward was he was formally appointed as the Chief mechanical engineer of the GWR he had in fact been for all practical purposes in charge of the department because of the failing mental health of Dean. This allowed Churward to undertake some experimental work which resulted in the construction of the Kruger and Saint class locomotives.
The Kruger class was introduced in 1899 with two prototypes being built. One design was a 2-6-0 locomotive and the other a 4-6-0 engine. Only one 4-6-0 was built but a further eight 2-6-0 locomotives were completed up to 1903.
|Kruger 2-6-0 introduced in 1899|
There were many issues with these engines and they had very short lives which varied between three and six years. Although the Kruger was unsuccessful Churchward learnt many lessons including that if engines were to be introduced of far higher efficiency than had been obtained in the past (incorporating long stroke, long valve travel, small piston clearance and higher boiler pressure) then a new basic layout was required. The inside cylinders had to go.
The need to rethink the design resulted in development of the tapered boiler which led to the development of another experimental engine being introduced in 1902.
This locomotive which was to become the forerunner of a long line of 4-6-0 express engines. This was number 100 which in 1912 was named Dean (later William Dean) renumbered 2900 in 1912.
|100 William Dean as introduced in 1902|
It had a high running plate and large domeless parallel boiler, raised Belpaire firebox and outside cylinders. This was the first GWR locomotive to have outside cylinders. The piston valves were driven by rocking levers actuated by the expansion link of Stephenson valve gear which looked unusual at the time. The parallel boiler was later replaced with a half-cone boiler, then the first superheated half-cone boiler in 1910. Churchward had studied American boiler design, but he was also influenced by continental practice in efficient motion design. A Glehn 4-4-2 compound engine was ordered from Societe Alsacienne de Constructions Mecaniques for comparison trials on GWR. Churchward insisted the locomotive was purchased so that he could undertake a true comparison with his own locomotives.
|Locomotive built specifically for the GWR by Société Alsacienne de Constructions Mécaniques on the de Glehn principles and delivered in October 1903. This locomotive was numbered 102 and named La France.|
The second (number 98) was built with a half-cone boiler and a re-designed valve gear layout and cylinders. The valve dimensions were increased from 6.5inch to 10inch. In 1906 it was re-boilered with a 225psi boiler to correspond with the third prototype. It was named Vanguard in 1907 but soon renamed Ernest Cunard. In 1912 it was renumbered 2998.
|98 As built at Swindon in March 1903|
The third prototype (number 171) was built as a 4-6-0 in December 1903 but was soon converted to 4-4-2 for the De Glehn trials. It was given the name Albion in 1904 .The boiler pressure was increased to 225psi. Whilst the trials were taking place another nineteen locomotives were ordered which were to be built to a similar design with thirteen built as 4-4-2s and six as 4-6-0s. The superior adhesion of the 4-6-0s set the pattern for the future and 171 was converted back to a 4-6-0 in July 1907 and all the Churchward Atlantics were converted to 4-6-0s in 1912-13. 171 was renumbered 2971 in 1912.
|171 Albion as after being converted to 4-4-2|
The de Glehn du Bousquet 4-4-2 locomotives of the Nord Railway in France were considered by many to be the finest express engines in the world. Their reputation for fast and economical running was such that they were widely copied elsewhere including on the Pennysylvannia Railroad in the USA.
Churchward insisted that a locomotive (102 La France) built on the de Glehn principles be purchased from the Société Alsacienne de Constructions Mécaniques so that he could undertake a true comparison between it and his own locomotive – 171 Albion. In a series of trials Albion proved to be as powerful and just as fast as La France and surprisingly slightly more economical in coal consumption. It would have been expected the French compound would have been more fuel efficient than the simple two cylinder Churchward engine. The excellent valve gear of the simple locomotive made it possible to run at 22%-25% whereas the compound on similar work needed about 55%. In addition the compound was more expensive to build and maintain.
Some people thought that the superior performance of the Churchward engine might be because the performance of 102 La France was somehow unrepresentative of that of the class generally. In 1905 Churchward obtained two more French compound engines (103 President and 104 Alliance) which were slightly larger and more powerful than 102 La France. It was found that any improvement in performance was insufficient to justify Churchward changing his ideas although he did adopt features of the bogies from the French locomotives. He also used the French pattern big-end for the inside connecting rod on his four cylinder engines.
The early Churchwardlocomotives were rebuilt from 1903 onwards with new superheated boilers and the remainder were built as such.
Successive batches were named after Ladies, Saints, Courts and names connected with the novels of Sir Walter Scott. They were collectively known as the Saint class.
There were many variants of the class. Some had inside steam pipes, while others had outside steam pipes. Some earlier engines had the raised running plate extended to the back of the cab.
In 1924 2925 Saint Martin was rebuilt with six feet wheels and renumbered 4900 to become the prototype of the 4900 Hall class.
2935 had Caprotti valve gear and it was the only locomotive ever to run on GWR with poppet valve.
In total seventy seven locomotives were built, the first being withdrawn in 1931. 2900 itself was withdrawn in 1932.
The last surviving Great Western Railway Saint class locomotive (2920 Saint David) was scrapped in 1953, long before the standard gauge steam railway preservation movement got under way.
The class incorporated many revolutionary advances in design and the ‘Saints’ are now acknowledged to have had a profound influence on almost every aspect of subsequent steam locomotive development.
The Belphaire boiler developed by Churchward had no excessive flat surfaces which had plagued earlier versions. The firebox tapered from front to rear, and the barrel from back to front, giving an ample space for the circulation of water and release of steam where it was most needed, around the firebox tupeplate. This type of boiler proved remarkably successful throughout the life of GWR and later Western Region steam. It was equally successful on the LMs onwards, and later on the British Railways standard locomotives. The design is more expensive to produce but proved cheaper in maintenance than other types. It solved the problem of using higher pressures without incurring excessive boiler maintenance costs. On other railways the fear of the level of costs inhibited the use of anything more than 180psi for many years.