BR standard class 9F
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The British Railways Standard Class 9F 2-10-0 is a class of steam locomotives, and the last steam locomotive design built by British Railways. 251 locomotives were built, numbered 92000-92250. Many lasted only a few years in service before withdrawal as steam traction was ended on the mainline in Britain.
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[edit] Background
On nationalisation in 1948, British Railways had a number of heavy freight locomotives that had been built to aid the war effort. It had 666 LMS 8F class 2-8-0, numerous WD Austerity 2-8-0s and WD Austerity 2-10-0s. New heavy freight locomotives were thus not a priority.
The original proposal was for a boiler from the Standard Class 7 Britannia 4-6-2 to be combined with a 2-8-2 wheel arrangement. However it is thought that R.A. Riddles preferred the 2-10-0 arrangement, as used on his Austerity 2-10-0s. The firebox had to be slightly reduced in size from the Britannias as a result. The 4' 8½" driving wheels lacked flanges on the centre axle and had reduced ones on the second and fourth.
The 9F turned out to be the best of the standard designs and surprisingly was also good at running on passenger trains. 92220 Evening Star operated the Capital's United Express between Cardiff and London in July 1960, reaching 90mph. Concerns about the durability of the locomotive brought this high speed running to a rapid end.
[edit] Variations
The 9F was used as a proving ground for a variety of technical innovations. All were promised to provide improvements in efficiency, power or cost. None delivered.
92020-92029 were built with Franco-Crosti boilers. An additional boiler ran under the main boiler, taking the firebox gases back from the smokebox to a chimney on the right side of the locomotive forward of the cab. The standard chimney at the front was only used during lighting up. The additional boiler acted as a pre-heater, using low-grade heat that would otherwise be wasted.
However, the experiment did not deliver the hoped-for benefits. Efficiency was not increased sufficiently to justify the cost and complexity. The locomotives were unpleasant on the footplate in a cross-wind and the low temperature of the gases in the secondary smokebox caused serious corrosion due to the formation of sulphuric acid. The engines were rebuilt without the Franco-Crosti boiler, although they retained some of their distinctive looks.
92165-92167 were built with a mechanical stoker. A helical screw conveyed coal from the tender to a plate in the firebox, where four steam pipes could be used to direct coal all over the grate. The powered stoker made higher steaming rates possible, albeit at the cost of a serious loss of efficiency. The 9F was however powerful enough for all the routes that were required, and even ignoring the loss of efficiency caused by such high firing rates there were no routes available that could take advantage.
It was also hoped that mechanical stoking might enable the burning of low-grade coal but this proved to be unsuccessful. Simply supplying more low grade coal than a fireman could do by hand did not provide stable burning.
92250 was built with a Giesl Blastpipe and chimney. This offered the same level of draught for a reduced level of exhaust back-pressure or, alternatively, increased draught with no performance loss elsewhere. The exhaust gases were progressively fed into the smokebox gases through a succession of nozzles, rather than by a single blast pipe.
Again, great claims were made as to the potential benefits, but these did not emerge either on test plant or in service. 92250 retained the variant blastpipe until withdrawal, but no benefit was noticeable. The burning of low-grade coal was again held out as a potential benefit, a benefit which was not delivered.
[edit] Evening Star
In 1960, 92220 Evening Star became the last steam locomotive to be built by British Railways. To mark this, she was named and given a green passenger livery, as opposed to the unlined black normally given, and a copper-capped chimney.
[edit] Preservation
Nine 9Fs have survived, these being 92134, 92203 Black Prince, 92207, 92212, 92214, 92219, 92220 Evening Star, 92240 and 92245.
[edit] In fiction
An example of this type of locomotive can be seen on the Thomas the Tank Engine and Friends TV Series. The character's name is Murdoch the Heavy Goods Engine, who, despite his size and strength, enjoys peace and quiet in 'Murdoch's Peace and Quiet'.
[edit] External links
| British Railways standard classes: |
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Britannia Class 7 | Duke of Gloucester | Clan Class 6 | 5MT 4-6-0 | 4MT 4-6-0 |
