The London and North Western Railway (LNWR) Jubilee Class was a class of 4-4-0 4-cylinder compound locomotives by F.W. Webb. A total of forty were built from 1897–1900. Slightly unusually for the LNWR, the class received a number series, this being 1901–1940. All were named, mostly after Royal Navy battleships.
Iron Duke and Black Prince
The first two of this class were prototypes, built to different designs to permit a comparison. The first, No. 1501 the Iron Duke (later re-named Diamond Jubilee and then Jubilee), was a 4-cylinder simple locomotive with cylinders. The second, No. 1502 Black Prince, was not Webb's first compound, but was his first 4-cylinder compound and the first in the UK. The outside high-pressure cylinders were the same as Iron Dukes, the inside low-pressure cylinders were .
There was no simpling valve or other means for starting, and so when starting they just operated as small 2-cylinder simples. The Joy valve gear was shared between high and low pressure, with a rocking lever to the high-pressure valves. The inside cylinders were angled above the outside cylinders and although this could have been solved by cranking the rocking levers, this gave an uneven drive to the valves; valve-setting between both of them had to be a compromise position, ideal for neither, and so gave an uneven power distribution between high and low. Their running was thus not as free-running as it might have been, which Webb would address in his later designs.
These were also Webb's first designs with a leading bogie rather than a pony truck, which was also described as a "double radial truck". The truck pivots geometrically at a point behind its rear axle, although there is no single mechanical pivot point. This motion is controlled instead, like Webb's earlier single radial truck, by curved radial slides, with a radius of curvature at the centre of the truck of .
Another novel feature was that both locomotives were fitted with double chimneys. The smokebox was partitioned internally into upper and lower halves, the lower section exhausting through the front chimney and the upper tubes through the rear chimney. The blastpipes were fed separately, the front chimney from the left cylinders and the rear from the right. After some time in service, the two chimneys were replaced with a single chimney on an undivided smokebox and their performance and fuel consumption measured again. It was found that the compound locomotive had identical performance both with and without the double chimney, but that the simple locomotive was improved by it. The double chimney was re-fitted to Jubilee, but the production locomotives were built as compounds without it.
After around a year's running, the simple had run for 33,517 miles, with an average coal consumption of 40.3 pounds per mile and the compound (starting slightly later) for 23,503 miles with a consumption of 38.1 pounds per mile. The compound was thus cheaper by 2.2 pounds per mile, or 5%.
The ratio between LP and HP cylinders was 1.69, lower than that considered optimal. Webb's 3-cylinder compounds had used the more usual figure of 2. To improve this to 1.87, Webb had decided to increase the size of the LP cylinders to , and this was applied to the production locomotives.
Service As with other Webb compounds, they were mechanically unreliable. As a result, George Whale rebuilt these as two-cylinder simple locomotives of the Renown Class, starting with 1918 Renown in 1908. Rebuilt engines retained their numbers. Rebuilding continued so that at the grouping of 1923, only 9 Jubilees remained, being 1903/4/8/11/12/15/23/27/29.
1908 Royal George was withdrawn in January 1923, but the remaining eight were allocated the LMS numbers 5110–5117, in sequence. Two, 1904 Rob Roy and 1923 Agamemnon were withdrawn 1923, without receiving new numbers. The LMS rebuilt the remaining six into Renowns in 1924, making the class extinct (Their subsequent history is discussed at LNWR Renown Class).
A successor to this class, the Alfred the Great class, retained the 4-cylinder compound design but used two sets of valvegear, both Joy, allowing the LP cutoff to be controlled independently.
Locomotive list +LNWR Jubilee class locomotive list LNWRNo. LNWRname CreweWorksNo. Datebuilt Daterebuilt LMSNo. Datewithdrawn Notes 1901 Jubilee 3856 5156 Named Iron Duke until December 1897, numbered 1501 until March 1899 1902 3857 5157 Numbered 1502 until March 1899 1903 3928 5110 1904 Rob Roy 3929 — (5111) Never carried its LMS number 1905 Black Diamond 3930 5137 1906 Robin Hood 3931 5149 1907 Black Watch 3932 5178 1908 3933 — — 1909 3934 5159 1910 Cavalier 3935 5172 1911 3936 5112 1912 3937 5113 1913 3938 5132 1914 3939 5144 Renumbered 1257 in April 1920 1915 3940 5114 1916 3941 5155 1917 3942 5184 1918 3943 5131 1919 3944 5160 1920 Flying Fox 3945 5166 1921 John of Gaunt 3995 5134 Named T. H. Ismay until April 1913 1922 3996 5146 1923 3997 — (5115) Never carried its LMS number 1924 3998 5183 1925 3999 5147 1926 La France 4000 5180 Shown at Exposition Universelle in Paris 1927 4001 5116 1928 4002 5173 1929 4003 5117 1930 4004 5142 1931 4045 5176 1932 4046 5162 1933 4047 5169 1934 4048 5165 1935 4049 5133 1936 4050 5150 1937 4051 5154 1938 4052 5161 1939 4053 5158 1940 4054 5170
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