The British Railways Standard Class 9F is a class of steam locomotive designed for British Railways by Robert Riddles. The Class 9F was the last in a series of standardised locomotive classes designed for British Railways during the 1950s, and was intended for use on fast, heavy freight trains over long distances. It was one of the most powerful steam locomotive types ever built for British Railways, and successfully performed its intended duties. The 9F class was given the nickname of 'Spaceship', due to its size and shape.
At various times during the 1950s, the 9Fs worked passenger trains with great success, indicating the versatility of the design, sometimes considered to represent the ultimate in British steam development. Several experimental variants were constructed in an effort to reduce costs and maintenance, although these met with varying degrees of success. They were capable of reaching speeds of up to 90 miles per hour (145 km/h).
The total number built was 251, production being shared between Swindon (53) and Crewe Works (198). The last of the class, 92220 Evening Star, was the final steam locomotive to be built by British Railways, in 1960. Withdrawals of the class began in 1964, with the final locomotives being withdrawn from service in 1968, the final year of steam traction on British Railways. Nine examples have survived into the preservation era in varying states of repair, including Evening Star.
They were generally thought of as very successful locomotives, O. S. Nock stating "The '9F' was unquestionably the most distinctive and original of all the British standard steam locomotives, and with little doubt the most successful. They were remarkable in their astonishing capacity for speed as well as their work in heavy freight haulage."
Background
The British Transport Commission had proposed that the existing steam locomotive fleet be replaced by both diesel and electric traction. However the board of British Railways, which wanted the railways to be completely electrified, ignored the BTC and ordered a new fleet of 'standard' steam locomotive designs as a stopgap ahead of electrification. Freight was well catered for in terms of locomotive availability after nationalisation in 1948, with a number of heavy freight locomotives built to aid the war effort forming part of British Railways' inheritance. This consisted of 666 LMS 8F Class and numerous Robert Riddles designed WD Austerity 2-8-0s and WD Austerity 2-10-0s.
It was the Eastern Region's Motive Power officer, L.P. Parker, who made the case for a new design of powerful freight locomotive, able to shift heavy loads at fast speeds in round trips between distant destinations within the eight-hour shift of the footplate crew. Riddles took up the challenge, initially designing a locomotive, but settled upon the 2-10-0 wheel arrangement for the increased traction and lower axle load that five coupled axles can provide. The resultant design became one of the most successful, but shortest-lived, locomotive classes ever built in Britain.
Design features
The 9F was designed at both Derby and Brighton Works in 1951 to operate freight trains of up to 900 tons (914 tonnes) at 35 mph (56 km/h) with maximum fuel efficiency. The original proposal was for a boiler from the BR Standard Class 7 Britannia , adapting it to a wheel arrangement but Riddles eventually settled upon a 2-10-0 type because it had been used successfully on some of his previous Austerity locomotives. Distributing the adhesive weight over five axles gave a maximum axle load of only 15 tons, 10 cwt. The driving wheels were in diameter. However, in order to clear the rear coupled wheels, the grate had to be set higher, thus reducing firebox volume. There were many problems associated with locomotives of such a long wheelbase, but these were solved by the design team through a series of compromises. The centre driving wheels had no flanges, and those on the second and fourth coupled wheels were reduced in depth. This enabled the locomotive to round curves of only radius. As on all other BR standard steam locomotives, the leading wheels were in diameter.