{{short description|1910s British piston aircraft engine}} {{infobox aero engine | name = BR.2 | image = File:Bentley BR 2 RAF Museum London.jpg | caption = B.R.2 engine on display at the [[RAF Museum London]] |engine_type= Rotary engine |national_origin =[[United Kingdom]] |manufacturer=[[Humber Limited|Humber]], [[Crossley Motors|Crossley]], [[Daimler Company|Daimler]], [[Gwynnes Limited|Gwynnes]], [[Ruston, Proctor and Company|Ruston and Proctor]] |first_run= 1917 |major_applications= [[Sopwith Snipe]] |number_built =2,567 |developed_from = [[Bentley BR1|Bentley BR.1]] |developed_into = |variants_with_their_own_articles = }}

The '''Bentley B.R.2''' was a nine-cylinder British [[Rotary engine|rotary]] [[aircraft engine]] developed during the [[World War I|First World War]] by the motor car engine designer [[W. O. Bentley]] from his earlier [[Bentley BR1|Bentley BR.1]]. The BR.2 was built in small numbers during the war, its main use being by the [[Royal Air Force]] in the early 1920s.<ref>Lumsden 2003, p.88.</ref>

==Design and development== The initial variant of the BR.2 developed {{cvt|230|hp}}, with nine cylinders measuring {{cvt|5.5|×|7.1|in}} for a total displacement of {{cvt|1522|cuin}}. It weighed {{cvt|490|lb}}, only {{cvt|93|lb}} more than the [[Bentley B.R.1|Bentley BR.1]]. This was the last type of rotary engine to be adopted by the RAF – later air-cooled aircraft engines such as the [[Bristol Jupiter|Cosmos Jupiter]] and [[Armstrong Siddeley Jaguar]] being almost entirely of the fixed [[Radial engine|radial]] type. With the BR.2, the rotary engine had reached a point beyond which this type of engine could not be further developed, due to its inherent limitations.<ref>Gunston 1989, p.22.</ref>

==Applications== The type selected as the standard single-seat fighter of the post-war RAF, the [[Sopwith Snipe]], had been designed around the BR.2, as had its [[ground attack]] version, the [[Sopwith Salamander|Sopwith TF.2 Salamander]]. A number of other experimental and minor production types were either designed for, or otherwise fitted with this power plant during the late "war" years and into the early 1920s. [[File:Gloster Nightjar02.jpg|thumb|right|[[Gloster Nightjar]] during evaluation at Farnborough in 1922]] * [[Armstrong Whitworth Armadillo]] * [[Austin Osprey]] * [[Boulton Paul Bobolink]] * [[Brennan Helicopter]] * [[Gloster Grouse]] * [[Gloster Nightjar]] * [[Gloster Sparrowhawk]] * [[Port Victoria Grain Griffin|Grain Griffin]] * [[Handley Page Type S]] * [[Nieuport Nightjar]] * [[Parnall Panther]] * [[Sopwith Buffalo]] * [[Sopwith Gnu]] * [[Sopwith Salamander]] * [[Sopwith Snipe]] * [[Vickers Vampire]]

==Variants== ;BR.2 230 :1918, 230&nbsp;hp. ;BR.2 245 :1918, 245&nbsp;hp.

==Engines on display== A Bentley BR.2 is on public display in the [[Science Museum (London)]], another forms part of the aero engine collection at the [[Royal Air Force Museum Cosford]]. Another one (serial number 40543, manufactured by Gwynnes) is in the [[National Military Museum, Romania]].

The sole operational BR.2 is mounted in [[Fantasy of Flight]]'s replica of the [[Sopwith Snipe]].<ref>Archived at [https://ghostarchive.org/varchive/youtube/20211211/fUQCqSw-Yds Ghostarchive]{{cbignore}} and the [https://web.archive.org/web/20160418094859/https://www.youtube.com/watch?v=fUQCqSw-Yds Wayback Machine]{{cbignore}}: {{cite AV media| url = https://www.youtube.com/watch?v=fUQCqSw-Yds&t=346s| title = Sopwith Snipe - Part 1 - Kermie Cam | website=[[YouTube]]}}{{cbignore}}</ref>

A ¼ scale working replica of the Bentley BR.2 World War I rotary aero engine built by Lewis Kinleside Blackmore is currently on display at the Bentley Memorial Building in Oxfordshire, UK. This was the first model built of this engine and is the subject also of a book by L K Blackmore.

The Canada Aviation and Space Museum in Ottawa, Ontario, Canada has a BR.2 installed in their Sopwith 7F.1 Snipe.

==Specifications (BR.2)== [[File:BentleyBR2(Plate).JPG|thumb|right|Manufacturer's plate (dated November 1917) and valve operating gear of the BR.2 engine on display at the [[Royal Air Force Museum Cosford]]]] {{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=''Jane's'' <ref>Jane's 1993, p.274.</ref> |type=9-cylinder rotary |bore=5.51 in (140&nbsp;mm) |stroke=7.09 in (180&nbsp;mm) |displacement=1521.8 in (24.94 L) |length= |diameter= |width= |height= |weight=490 lb (220&nbsp;kg) |valvetrain=Overhead valve |supercharger= |turbocharger= |fuelsystem= |fueltype= |oilsystem= |coolingsystem=Air-cooled |power=250 hp |specpower= |compression= |fuelcon=20 gallons per hour |specfuelcon= |oilcon=16 pints per hour |power/weight=0.5&nbsp;hp/lb |designer= |reduction_gear= |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= *[[Bentley BR1|Bentley BR.1]] *[[Clerget]] <!-- aircraft that are of similar role, era, and capability 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= *[[Le Rhône]] <!-- See [[WP:Air/PC]] for more explanation of these fields. --> }}

==References==

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

===Bibliography=== {{refbegin}} * {{cite book |last= Gunston |first= Bill |title=World Encyclopedia of Aero Engines |year=1986 |publisher=Patrick Stephens |location= Wellingborough |pages=25–26}} * Gunston, Bill. ''World Encyclopedia of Aero Engines''. Cambridge, England. Patrick Stephens Limited, 1989. {{ISBN|1-85260-163-9}} *''Jane's Fighting Aircraft of World War I''. London. Studio Editions Ltd, 1993. {{ISBN|1-85170-347-0}} * Lumsden, Alec. ''British Piston Engines and their Aircraft''. Marlborough, Wiltshire: Airlife Publishing, 2003. {{ISBN|1-85310-294-6}}. {{refend}}

==External links== {{Commons category|Bentley BR2}} * [https://web.archive.org/web/20071212200433/http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=812 National Museum of the USAF - BR.2 fact sheet]

[[Category:Rotary aircraft piston engines]] [[Category:Air-cooled aircraft piston engines]] [[Category:1910s aircraft piston engines]]