Editing BR Standard Class 9F (section)

==Variations==
The 9F was used as a proving ground for a variety of technical innovations intended to provide improvements in efficiency, power or cost.

===Franco-Crosti boiler===
[[File:Chesterfield BR 2-10-0 with Franco-Crosti boiler geograph-2751531-by-Ben-Brooksbank.jpg|thumb|left|Right hand view of a Crosti BR Standard 9F 2-10-0, No. 92024, showing the unique layout]]
[[File:Up freight train at Newport High Street Station - geograph.org.uk - 2127054.jpg|thumb|right|9F 92029 at Newport in 1963. By this stage it had been converted back to a conventional arrangement]]
{{details|BR Standard Class 9F 92020-9}}
Ten locomotives (numbers 92020-92029) were built in 1955 with the [[Franco-Crosti boiler]]{{r|Walford|p=46}}<ref>{{cite web |url=https://www.aqpl43.dsl.pipex.com/MUSEUM/LOCOLOCO/francocrosti/francocrosti.htm |title=The Franco-Crosti Boiler System |access-date=6 December 2007 |archive-date=31 October 2010 |archive-url=https://web.archive.org/web/20101031005906/http://www.aqpl43.dsl.pipex.com/MUSEUM/LOCOLOCO/francocrosti/francocrosti.htm |url-status=dead }}</ref> which incorporated a combustion gas feed water preheater that recuperated low-grade residual heat.<ref name="Chapelon" >{{cite book |last=Chapelon |first=Andre |title=La Locomotive à Vapeur |edition=English ed., transl. Carpenter George W. |publisher=Camden Miniature Steam Services |location=Somerset |year=2000 |isbn=0-9536523-0-0 |pages=85, 372, 488, 550, 552}}</ref> 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.<ref name="Duffy">{{cite journal |last=Duffy |first=M.C. |title=Waste heat recovery and steam locomotive design |journal=Transactions of the Newcomen Society |volume=61 |year=1989 |pages=15–31 |doi=10.1179/tns.1989.002}}</ref><ref name="Cox">{{cite book |last=Cox |first=E. S. |title=British Railways Standard Locomotives |publisher=Ian Allan |location=London |year=1966 |pages=113-117, 136-139}}</ref> 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.

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===Westinghouse Pump Variation===
The ten 9F locomotives (92060-92066 and 92097–92099) allocated to [[Tyne Dock]] on the NER were fitted with Westinghouse Pumps to drive the pneumatic doors on the 56 ton ore hopper wagons which operated on the heavily inclined [[Consett]] line to the [[Consett Iron Company]]. These additional pumps allowed automatic discharging of the ore train, consisting of nine hoppers, in under a minute at Consett.<ref>{{Cite web|url = http://southpelawjunction.co.uk/wp/?page_id=631|title = Iron Ore Trains|date = 23 March 2014|access-date = 13 September 2020|archive-date = 10 January 2021|archive-url = https://web.archive.org/web/20210110091004/http://southpelawjunction.co.uk/wp/?page_id=631|url-status = live}}</ref>

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===Mechanical stoker and blastpipe variation===
Locomotive numbers 92165–92167 were built with a [[mechanical stoker]], which was a helical screw that conveyed coal from the tender to the firebox, where it would be directed to the required part of the [[:wikt:grate|grate]] by high-pressure steam jets controlled by the fireman.<ref name=Herring /> The stoker made higher steaming rates possible, and it was hoped that mechanical stoking might enable the burning of low-grade coal. It was relatively inefficient, and the locomotives used in this trial were rebuilt to the normal configuration.<ref name=Herring /> Simply supplying more low grade coal than a fireman could do by hand did not provide efficient burning. Trials found that the maximum coal delivery rate of the mechanical stoker was slightly faster than firing by hand, and it could maintain that maximum for hours at a time when a fireman would tire. However, that was of little practical benefit in actual service, because even a long-distance freight train would frequently stop to allow faster trains to pass or would be held at signals. For the short periods when maximum firing rate was needed, a skilled fireman was more than sufficient. The success of mechanical stokers on North American railroads was mainly because the locomotives were significantly larger (with a commensurately greater demand for coal) and many routes required hours of supplying coal at a rate beyond the physical limit of a single fireman.

Number 92250 was equipped with a [[Giesl ejector]], which divided the exhaust steam between seven nozzles arranged in a row on the locomotive's longitudinal axis, and directed into a narrow fan-shaped ejector that more intimately mixed it with the smokebox gases than is the case of an ordinary chimney.<ref name=Herring /> That offered the same level of draught for a reduced level of exhaust back-pressure or, alternatively, increased draught with no performance loss elsewhere. Again, claims were made about the potential benefits, and 92250 retained the variant chimney until withdrawal, although no benefit was noticeable.<ref name=Herring />

The only modification which did deliver any noticeable benefit was the fitting of 92178 with a [[double chimney|double blastpipe and chimney]] during its construction. Following delivery in September 1957, it was subjected to extensive testing, both in the [[Rugby Locomotive Testing Station]] and on service trains. After the completion of the tests in February 1958, it was decided to fit all 9Fs built subsequently with double blastpipes and chimneys — they were numbers 92183 onwards, as well as 92165–7. The modification was also installed on 92000/1/2/5 and 92006.{{r|Walford|p=29}} That allowed the engines to steam slightly more freely and thus generate higher power ranges.<ref name=Herring />