The British Railways (BR) Standard Class 9F 2-10-0 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 class was given the nickname of 'Spaceships', due to its size and shape. In 1955 BR experimentally built 10 9F's at Crewe Works; these 10 were fitted with Franco-Crosti boilers. The Franco–Crosti boiler is a type of boiler used for steam locomotives. It was designed in the 1930s by Attilio Franco and Dr Piero Crosti. The main difference between it and conventional feedwater heaters widely used on the continent is that the Franco-Crosti boiler uses both exhaust steam and exhaust gases from the firebox. Conventional feedwater heaters only use exhaust steam. The Franco-Crosti boiler took the form of a single cylindrical water drum running along the underside of the main boiler barrel; the standard chimney at the front was only used during lighting-up, in normal working the gases went through firetubes inside the preheater drum that led to a second smokebox situated beneath the boiler from which there emerged a chimney on the right-hand side, just forward of the firebox. However; the experiment did not deliver the hoped-for benefits, and efficiency was not increased sufficiently enough to justify the cost and complexity. Moreover, conditions were unpleasant on the footplate in a cross-wind, this in spite the later provision of a small deflector plate forward of the chimney. These problems led to the subsequent sealing off of the preheater drum, over the period of 1959 to 1961, and the locomotives were then worked conventionally. As a result of this, there was a reduced ability to generate steam, and so their power classification was reduced from 9F to 8F. No. 92028 was the first Franco-Crosti 9F to be withdrawn in October of 1966, No. 92027 followed in August of 1967, with the remainder being withdrawn en masse in November of 1967. All were scrapped, with none surviving into preservation.
