Editing Bristol Centaurus (section)

==Design and development==

Like other Bristol sleeve valve engines, the Centaurus was based on the design knowledge acquired from an earlier design, in this case the [[Bristol Perseus]] cylinder. The Centaurus used 18 Perseus cylinders.   The same cylinder was in use in the contemporary 14-cylinder [[Bristol Hercules|Hercules]], which was being brought into production when the design of the Centaurus started.<ref>{{cite book| title=Fedden-the life of Sir Roy Fedden |first=Bill |last=Gunston |date=1998 |publisher=Rolls-Royce Heritage Trust |series=Historical Series No 26 |isbn=1872922139 |pages=175,179}}</ref>
[[File:Sleeve Valve Closeup.JPG|thumb|left|Sectioned cylinder showing sleeve valve]]
The Centaurus had a cylinder swept volume of {{cvt|3272|cuin|L|1}},  nearly as much as the American {{cvt|3347.9|cuin|L|1}} [[Wright R-3350 Duplex-Cyclone|Wright R-3350 ''Duplex-Cyclone'']] large radial, making the Centaurus one of the largest aircraft piston engines to enter production, while that of the Hercules was {{cvt|2363|cuin|L|1}}. The nearly 40 per cent higher capacity was achieved by increasing the stroke from {{convert|6.5|to|7|in|mm|sigfig=3}} and by changing to two rows of nine cylinders instead of two rows of seven. The diameter of the Centaurus was only just over 6 per cent greater than the Hercules in spite of its much greater swept volume.<ref name="Jane's">Bridgman (Jane's) 1998, p. 270.</ref>

The cylinder heads had an indentation like an inverted top hat, which was finned, but it was difficult to get air down into this hollow to adequately cool the head. During development, Bristol contacted [[ICI Metals Division]], Birmingham, to enquire whether a copper-chromium alloy with higher thermal conductivity would have sufficient high temperature strength to be used for this purpose. With the same cylinder volume and using the new material, the horsepower per cylinder was raised from {{cvt|110|hp}} to {{cvt|220|hp}}.

Bristol maintained the Centaurus from type-testing in 1938, but production did not start until 1942, owing to the need to get the Hercules into production and improve the reliability of the entire engine line.<ref name="Jane's"/>  Nor was there any real need for the larger engine at this early point in the war, when most military aircraft designs had a requirement for engines of about {{cvt|1000|hp|0}}. The Hercules power of about {{cvt|1500|hp|0}} was better suited to the existing airframes.

The Centaurus did not enter service until near the end of the war, first appearing on the [[Vickers Warwick]]. Other wartime, or postwar, uses included the [[Bristol Brigand]] and [[Bristol Buckmaster|Buckmaster]], [[Hawker Tempest]] and [[Hawker Sea Fury|Sea Fury]] and the [[Blackburn Firebrand]] and [[Blackburn Beverley|Beverley]]. The engine also entered service after the war in a civilian airliner, the [[Airspeed Ambassador]] and was also used in the [[Bristol Brabazon]] I Mark 1 prototype aircraft until the Brabazon trans-Atlantic airliner programme was cancelled. The eight Centaurus engines were to be replaced with eight [[Bristol Proteus]] gas turbines on the Mark II giving a {{cvt|100|mph}} faster cruising speed at {{cvt|10000|ft}} higher altitude.<ref>{{cite book |title=Bristol Brabazon |first=Graham M. |last=Simons |date=2012 |publisher=History Press Limited |isbn=9780752467337 |page=100}}</ref> By the end of the war in Europe, around 2,500 examples of the Centaurus had been produced by Bristol.<ref name="Jane's"/>

The 373 was the most powerful version of the Centaurus and was intended for the Blackburn Beverley transport aircraft. Using direct fuel injection, it achieved a remarkable {{cvt|3220|hp}}, but was never fitted.<ref>{{Cite magazine |url=http://www.flightglobal.com/pdfarchive/view/1956/1956%20-%200572.html |title=Aero Engines 1956 |work=Flight |date= 11 May 1956 |accessdate= 12 December 2014 |archive-url=https://web.archive.org/web/20160827083642/http://www.flightglobal.com/pdfarchive/view/1956/1956%20-%200572.html |archive-date=2016-08-27 |page=572}}</ref> A projected enlarged capacity version of the Centaurus was designed by Sir [[Roy Fedden]]; cylinders were produced for this engine, but it was never built. Known as the Bristol Orion, a name used previously for a variant of the Jupiter engine and  [[Bristol Orion|later re-used for a turboprop]], this development was also a two-row, 18 cylinder sleeve valve engine, with the displacement increased to {{cvt|4142|cuin|1}} [{{cvt|6.25|×|7.5|in}}], nearly as large as the American [[Pratt & Whitney R-4360 Wasp Major]] four-row, 28-cylinder radial, the largest displacement aviation radial engine ever placed in quantity production.<ref>Gunston 2006, p.152.</ref>