page_title: BR Standard Class 9F
section_title: Franco-Crosti boiler
hierarchical_section_title: BR Standard Class 9F / Variations / Franco-Crosti boiler
caption_attribution_description: English: BR 2-10-0 with Franco-Crosti boiler at Chesterfield. View NE, towards Tapton Junction, Sheffield, Rotherham etc.: ex-Midland Main Lines. On one of the almost constant flow of freight and mineral trains through Chesterfield Midland, this was an unusual locomotive. No. 92024 was one of the ten BR 9F 2-10-0s built (5/55) with Franco-Crosti boilers, in which the exhaust was passed through a secondary chamber acting as a pre-heater and came out of a large orifice on the right hand side. (The conventional chimney was used only when lighting up). The arrangement outweighed any advantages and the boilers of these ten engines were changed back to normal (with the pre-heater blanked off)after about five years - on this one in 2/60, the locomotive then lasting until 11/67.
context_page_description: 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 profile, daylight can be seen between the frames and the boiler.
  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.
  The total number built was 251, production being shared between Swindon and Crewe Works. The last of the class, 92220 Evening Star, was the final steam locomotive to be built by British Railways, in 1960.
context_section_description: Ten locomotives (numbers 92020-92029) were built in 1955 with the Franco-Crosti boiler. which incorporated a combustion gas feed water preheater that recuperated low-grade residual heat. In the 9F version, this took the form of a single cylindrical water drum running along the underside of the main boiler barrel. The standard chimney on top of the smokebox 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. In the event, the experiment did not deliver the hoped-for benefits, and efficiency was not increased sufficiently to justify the cost and complexity. Moreover, conditions were unpleasant on the footplate in a cross-wind, this in spite of the later provision of a small deflector plate forward of the chimney. These problems led to the subsequent removal of the preheater drum, although the locomotives did retain the original main smokebox with its distinctive look.
caption: Right hand view of a Crosti BR Standard 9F 2-10-0, No. 92024, showing the unique layout
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