John Speller's Web Pages Dean Compound No. 8

John Speller's Web Pages - GWR Broad Gauge Locomotives

Dean Compound No. 8
In May 1886 Swindon Works turned out William Dean's broad gauge 4-cylinder compound 2-4-0 No. 8. A somewhat similar narrow gauge engine, No. 7, was produced about the same time. The coupled wheels were 7' 0" in diameter and the boiler pressure was 180 psi, unusually high for those days. The locomotives were subject to teething problems in their trials and the initial results were unimpressive, so the Locomotive Committee decided not to proceed any further with the experiment, and the locomotive was withdrawn after running a mere 3,050 miles. This was probably most unfortunate as the locomotive may have had considerable potential. After the end of the broad gauge in May 1892, the high pressure boiler and firebox were removed, but other parts of the locomotive were incorporated into a new narrow-gauge 4-4-0 of 1894.

Gairns notes: "At about the same time [1886-87]two engines were experimentally converted on the Great Western Railway, one engine having ordinary tandem inside cylinders, the high-pressure cylinders being placed in front of the low-pressure cylinders, and in the other case the low-pressure cylinders were in front, and their pistons had two piston rods which worked on either side of the high-pressure cylinders, so that each crosshead had three piston rods connected to it, substantially in the manner indicated by fig. 1. These experiments again did not result in further compound locomotives, and the engines were soon afterwards rebuilt as non-compounds [J. F. Gairns, Locomotive Compounding and Superheating (London, 1907) p. 41]."
Dean's broad gauge 2-4-0 tandem compound locomotive No. 8, built 1886
William Dean's 4-cylinder tandem compound No. 8. To enlarge right click and select "view image"
Fig. 1 Three piston-rod system as used in one of the Dean Compounds
Another view of No. 8 as built in May 1886
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