G&SWR 11 Class
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The G&SWR No 11 was one of the first four-cylinder steam locomotives in the UK. It was built to the design of James Manson at the G&SWR's Kilmarnock Works in 1897,[2][3][6] as a development of his two-cylinder 'Manson Bogies' of 1892.[3][7]
This was one of three designs of the first four-cylinder locomotives, produced near-simultaneously around 1897.[3] The others were Webb's Black Prince or Jubilee class and Drummond's T7. As was the typical express passenger locomotive pattern of the day, all were of 4-4-0 arrangement.[i]
The 4-4-0 had been in use for some time before this. The first example of a comparable UK design was the NBR 224 Class of 1871. Coincidentally, the first of that class was rebuilt in 1885, after its loss in the Tay Bridge disaster, to become the first four-cylinder locomotive, although as a tandem compound.[3]
Manson's earlier 'Manson Bogies' were already in successful service. To improve their running at speed, he planned to make a four-cylinder version, which could be better balanced. Inside and outside cylinders ran at 180° to each other, with each side quartered at 90°, as conventional. He may also have been considering a four-cylinder compound, as for Webb.[8] The two inside cylinders were narrowed from 18+1⁄4 to 14+1⁄2 in (460 to 370 mm) but kept their 26 in (660 mm) stroke. 12+1⁄2 in × 24 in (320 mm × 610 mm) external cylinders were added, unusual in that their stroke was shorter than the internal ones. This was due to the short bogie wheelbase leaving little room for the outside cylinders between the wheels. Although such a difference was unusual, it did not affect their balance. The overall cylinder volume of the four-cylinder locomotive was the same as the two-cylinder.[ii][3][9]
A single set of Stephenson valve gear was shared between inside and outside cylinders. The valves of the inside cylinders were driven directly, the outside valves were balanced valves mounted above their cylinders and driven through a transverse rocking shaft.[3] Both used slide valves, the inside slide valves mounted between the cylinders, the outside valves placed on top above the footplate.
