GWR 9 and 10 Dean Experimental Single Wheelers
These were Dean prototypes. Superficially rather ordinary looking 2-2-2s by the time they went out of service, they are perhaps more interesting and influential than sometimes given credit to. I don't think I really said enough about them in the printed version of the book. I shall try and produce a series of sketches, although material can be rather sparse.
No. 9 started life in 1881 as a rather absurd express 4-2-4 tank engine with 7ft 8in driving wheels and was so prone to derailment it probably never went into service at all: at times the GWR denied it had ever existed. There is a long piece about No 9 in the original form in Les Summers' book "Swindon Steam", where he draws rather different conclusions about its design than those found in RCTS. I find his arguments rather persuasive.
In 1884 substantial parts of this locomotive were included in a renewed no. 9, which was a more conventional 2-2-2, still with the 7ft 8in driving wheels. Both iterations of no 9 had Stephenson's valve gear outside the frames with valves and cylinders inside the frames.
No. 10 followed in 1886 and was externally similar to No. 9, but had rather different internals, with the slide valves located under the cylinders. This is generally called the Stroudley layout, having been devised by Stroudley of the LBSCR. This layout was clearly successful since it was repeated on the 3001 (Dean Single) class and all the larger inside cylinder 4-4-0s.
Both 9 and 10 were reconstructed in 1890 with 7ft driving wheels and a conventional layout, generally similar to the Queen Class. The external valve gear on No 9 disappeared, and I think that new cylinders with the valves underneath were fitted. In 1890, or perhaps 1893 they were named Victoria and Royal Albert respectively. No 9 received a belpaire firebox boiler in 1901, together with a larger cab. They were scrapped in 1905 and 1906.
There are a few photos about of the pair in their later days - see, for example, the June 3 entry in the GWS Blog here: https://didcotrailwaycentre.org.uk/article.php/515/going-loco-june-2022. They're all a bit muddy in the shadows below the footplate though.
Edited by JimC
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