Robinson C5 (GCR Classes 8D & 8E) 4-4-2 Atlantics

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These four locomotives were an attempt at implementing compound expansion by Robinson. Compound expansion was believed to be a good way of improving efficiency, but it was never very popular in Britain. The most successful implementation was that of Walter Smith who designed the LMS Compound 4-4-0s that survived into British Railways (BR) ownership. Smith introduced this particular system of compound expansion whilst at the North Eastern Railway's (NER) Gateshead Works. In 1898 he rebuilt 4-4-0 No. 1619 as a three cylinder compound expansion locomotive (LNER D19 4-4-0). Robinson was impressed by the reports of this locomotive's success, and ordered two W.M. Smith-compound Atlantics based on his C4 Atlantic. Robinson's experiment may have also been influenced by the Great Western Railway's (GWR) purchase of the compound expansion de Glehn Atlantics from France.
The first two C5s were built in December 1905 and February 1906, and a second pair was built in December 1906.
The central high pressure cylinder drove the leading coupled axle, resulting in the cylinder being positioned far forward of the other two cylinders. Stephenson motion was used on all three cylinders, with a 10in diameter W.M. Smith-pattern piston valve on the central cylinder. The outside cylinders had unbalanced slide valves. All three sets of motion were driven from the rear coupled axle.
The C5's compound expansion resulted in a coal saving of about 2 to 2.5lb of coal per mile, when compared to the simple expansion C4. This slight advantage was negated by the extra cost and complexity of a compound third cylinder. Robinson introduced superheating a few years later, and this produced substantial improvements in efficiency without the complexity of compound expansion. Compound expansion was not developed any further by the GCR.

Just 2 photos in this collection
A very clean 258 in Great Central livery
258 The Rt. Hon. Viscount Cross GCB GCSI  (GCR Livery) Robinson C5 (GCR Classes 8D & 8E) 4-4-2
https://railway-photography.smugmug.com ... /i-kJTRWpN

and a very dirty 2898 in N.E. livery
2898 Sir William Pollitt Robinson C5 (GCR Classes 8D & 8E) 4-4-2
https://railway-photography.smugmug.com ... /i-z37pttK


Neil