{{Short description|V-8 piston aircraft engine}} {{For|the enzyme|c-Raf}}{{For|the wrestling event|RAF 01}} <!-- This article is a part of Wikipedia:WikiProject Aircraft. Please see Wikipedia:WikiProject Aircraft/page content for recommended layout. --> {{infobox aero engine |name=RAF 1 |image=File:Royal Aircraft Factory RAF 1a NASM.jpg |caption=RAF 1a at the National Air and Space Museum |engine_type=Piston V8 aero engine |manufacturer=Royal Aircraft Factory |first_run=1913 |major_applications={{ubl|Royal Aircraft Factory B.E.2|Airco DH.6 }} |number_built = |developed_from = Renault 70/80 hp |developed_into = |variants_with_their_own_articles = }}

The '''RAF 1''' is a British air-cooled, V-8 engine developed for aircraft use during World War I. Based on a French design, it was developed at the Royal Aircraft Factory, and built by six different British companies including Daimler, Rolls-Royce and Wolseley Motors Limited.

==Design and development== The RAF 1 was based on the Renault 70/80 hp engine, being intended specifically to replace that engine in the B.E.2c. It featured larger cylinders ({{convert|3.94|x|5.5|in|mm|abbr=on}}) for a total displacement of 540 cubic inches (8.8 L). It was rated at 92&nbsp;hp (70&nbsp;kW) at 1,600 rpm. The heads were cast integrally with the cylinders, with the intake and exhaust valves set one above the other in an upside-down F-head configuration.

The engines featured a large diameter lightweight flywheel at the rear, enclosed in a cast housing. Engine oil was picked up from the bottom of the crankcase and slung into a reservoir at the top. From there it was gravity fed, via a gallery high on the right side of the engine block, to the main bearing caps, and then to the connecting rod journals by the centrifugal effect of the turning crankshaft. The main bearings were ball bearings and were splash fed. Engine oil from the gallery was also supplied to the 1 : 2 reduction gearbox at the front. This drove the four-bladed propeller at one half engine speed, and the single camshaft was splined into the rear of the short propeller shaft. This arrangement meant that no mechanical oil pump was needed. Excess engine oil from the flywheel overflowed the reservoir and trickled over the large surface area of the round flywheel cover.

Two passages cast into the cover took air-fuel mixture from the carburettor mounted at the bottom to a copper U-shaped inlet manifold mounted between the banks of cylinders, and the flywheel cover acted as a heat exchanger, preheating the fuel-air mixture. In late 1915, the bore was increased to {{convert|4.1|in|mm}}, leading to an increased displacement of 590 cubic inches (9.7 L) and power of 86&nbsp;kW (115&nbsp;hp) at 1,800 rpm.<ref name="Lumsden">Lumsden 2003, p. 223.</ref>

===Supercharger=== In late 1915 a supercharged experimental version of the RAF 1a was developed.<ref name="Hare2">Hare 1999, p. 86.</ref> The engine was test flown in a B.E.2c. Climb rate improved from taking 36 minutes to reach {{convert|8,500|ft|m|abbr=on}}, without the supercharger, to reaching {{convert|11,500|ft|m|abbr=on}} in the same time with the supercharger.<ref name="Smithsonian">{{Cite journal |last=Sherman |first=Donald |date=May 2001 |title=Hill Climb |url=https://www.smithsonianmag.com/air-space-magazine/hill-climb-2023375/ |journal=Air and Space Magazine |publisher=Smithsonian |publication-place=USA |issn=0886-2257}}</ref>

==Variants== ;RAF 1 ;RAF 1a :Standard engine for aircraft using this powerplant. ;RAF 1b :Uprated version slated for installation in the B.E.2e - reliability problems precluded production.<ref>Hare (1990) p. 115</ref> ;RAF 1c ;RAF 1e

==Applications== [[File:Armstrong-Whitworth FK3.jpg|thumb|Armstrong Whitworth F.K.3]] ''List from Lumsden'' <ref name="Lumsden"/> *Airco DH.6 *Armstrong Whitworth F.K.2 *Armstrong Whitworth F.K.3 *Avro 504 *Boulton Paul P.6 *Boulton Paul P.9 *de Havilland DH.51 (prototype) *Royal Aircraft Factory B.E.2 *Royal Aircraft Factory B.E.9 *Royal Aircraft Factory S.E.5 (postwar civilian conversions) ==Specifications (RAF 1a)== {{pistonspecs| <!-- If you do not understand how to use this template, please ask at Wikipedia talk:WikiProject Aircraft --> <!-- Please include units where appropriate (main comes first, alt in parentheses). If data are missing, leave the parameter blank (do not delete it). For additional lines, end your alt units with )</li> and start a new, fully-formatted line with <li> --> |ref=''Lumsden'' <ref name="Lumsden"/> |type=8-cylinder, upright, 90 degree Vee engine |bore={{convert|3.94|in|mm|abbr=on}} |stroke={{convert|5.51|in|mm|abbr=on}} |displacement=537.4 cu in (8.8 L) |length= |diameter= |width= |height= |weight=450 lb |valvetrain= |supercharger= |turbocharger= |fuelsystem=Twin Claudel-Hobson carburettors |fueltype= |oilsystem=Wet sump |coolingsystem=Air-cooled |power=108 hp at 1,800 rpm (takeoff power) |specpower= |compression=4.3:1 |fuelcon= |specfuelcon= |oilcon= |power/weight= |designer= |reduction_gear=0.5:1, Left-hand tractor |general_other= |components_other= |performance_other= }}

==See also== {{aircontent <!-- other related articles that have not already linked: --> |see also=

<!-- designs which were developed into or from this aircraft: --> |related= *Renault 80 hp

<!-- aircraft that are of similar role, era, and capability as this design: --> |similar aircraft=

<!-- relevant lists that this aircraft appears in: --> |lists= *List of aircraft engines <!-- For aircraft engine articles. Engines that are of similar to this design: --> |similar engines= *Wolseley 60 hp <!-- See WP:Air/PC for more explanation of these fields. --> }}

==References== {{Commons category|Royal Aircraft Factory RAF 1A}}

===Notes=== {{reflist}}

===Bibliography=== {{refbegin}} * Lumsden, Alec. ''British Piston Engines and their Aircraft''. Marlborough, Wiltshire: Airlife Publishing, 2003. {{ISBN|1-85310-294-6}}. * Hare, Paul R. ''Aeroplanes of the Royal Aircraft Factory''. London: The Crowood Press, 1999. {{ISBN|1-86126-209-4}} * Hare, Paul R. ''The Royal Aircraft Factory''. London: Putnam, 1990. {{ISBN|0-85177-843-7}} *{{cite book |last= Gunston |first= Bill |title=World Encyclopedia of Aero Engines |year=1986 |publisher=Patrick Stephens |location= Wellingborough |pages=151 }} {{refend}}

{{Royal Aircraft Factory aeroengines}}

Category:1910s aircraft piston engines Category:V8 engines Category:Air-cooled aircraft piston engines Category:Royal Aircraft Factory aircraft engines