Editing Bristol Hercules

{{Short description|Radial aircraft engine by Bristol Engine Company}}
{{Use dmy dates|date=December 2016}}
{{Use British English|date=December 2016}}
<!-- This article is a part of [[Wikipedia:WikiProject Aircraft]]. Please see [[Wikipedia:WikiProject Aircraft/page content]] for recommended layout. -->
{|{{Infobox aircraft begin
 |name=Hercules
 |image= File:Bristol-hercules east-fortune.jpg
 |caption=Cutaway Bristol Hercules engine at the [[National Museum of Flight]], East Fortune, Scotland
}}{{Infobox aircraft engine
 |type=[[Piston]] [[aircraft engine]]
 |national origin=United Kingdom
 |manufacturer=[[Bristol Aeroplane Company]]
 |first run=January 1936
 |major applications=[[Bristol Beaufighter]]<br />[[Short Stirling]]<br />[[Handley Page Halifax]]
 |number built = 57,400
 |program cost = 
 |unit cost = 
 |developed from = [[Bristol Perseus]]
 |developed into = [[Bristol Centaurus]]
 |variants with their own articles =
}}
|}

The '''Bristol Hercules''' is a 14-cylinder two-row [[radial engine|radial]] [[aircraft engine]] designed by Sir [[Roy Fedden]] and produced by the [[Bristol Engine Company]] starting in 1939. It was the most numerous of their single [[sleeve valve]] ([[Sleeve valve#Burt-McCollum|Burt-McCollum]], or [[Argyll (automobile)|Argyll]], type) designs, powering many [[aircraft]] in the mid-[[World War II]] timeframe.

The Hercules powered a number of aircraft types, including Bristol's own [[Bristol Beaufighter|Beaufighter]] [[heavy fighter]] design, although it was more commonly used on [[bomber]]s. The Hercules also saw use in civilian designs, culminating in the 735 and 737 engines for such as the [[Handley Page Hastings]] C1 and C3 and [[Bristol Freighter]]. The design was also licensed for production in [[France]] by [[SNECMA]]. 


==Design and development==
Shortly after the end of World War I, the Shell company, Asiatic Petroleum, commissioned [[Harry Ricardo]] to investigate problems of fuel and engines. His book was published in 1923 as “The Internal Combustion Engine”.{{sfnp|Gunston|1993|p=32}} Ricardo postulated that the days of the poppet valve were numbered and that a sleeve valve alternative should be pursued.{{sfnp|Gunston|1993|p=151}}

The rationale behind the single [[sleeve valve]] design was two-fold: to provide optimum intake and [[exhaust gas]] flow in a two-row radial engine, improving its [[volumetric efficiency]] and to allow higher compression ratios, thus improving its [[thermal efficiency]]. The arrangement of the cylinders in two-row radials made it very difficult to utilise four valves per cylinder, consequently all non-sleeve valve two- and four-row radials were limited to the less efficient two-valve configuration. Also, as combustion chambers of sleeve-valve engines are uncluttered by valves, especially hot exhaust valves, so being comparatively smooth they allow engines to work with lower [[octane number]] fuels using the same compression ratio. Conversely, the same octane number fuel may be utilised while employing a higher compression ratio, or supercharger pressure, thus attaining either higher economy or power output. The downside was the difficulty in maintaining sufficient cylinder and sleeve lubrication.

Manufacturing was also a major problem. Sleeve valve engines, even the mono valve Fedden had elected to use, were extremely difficult to make. Fedden had experimented with sleeve valves in an inverted V-12 as early as 1927 but did not pursue that engine any further. Reverting to nine cylinder engines, Bristol had developed a sleeve valve engine that would actually work by 1934, introducing their first sleeve-valve designs in the {{convert|750|hp|kW|abbr=off}} class [[Bristol Perseus|Perseus]] and the {{convert|500|hp|kW|abbr=on}} class [[Bristol Aquila|Aquila]] that they intended to supply throughout the 1930s. Aircraft development in the era was so rapid that both engines quickly ended up at the low-power end of the military market and, in order to deliver larger engines, Bristol developed 14-cylinder versions of both. The Perseus evolved into the Hercules, and the Aquila into the [[Bristol Taurus|Taurus]].

These smooth-running engines were largely hand-built, which was incompatible with the needs of wartime production. At that time, the tolerances were simply not sufficiently accurate to ensure the mass production of reliable engines. Fedden drove his teams mercilessly, at both Bristol and its suppliers, and thousands of combinations of alloys and methods were tried before a process was discovered which used centrifugal casting to make the sleeves perfectly round. This final success arrived just before the start of the Second World War.{{sfnp|Gunston|1993|p=151}}

In 1937 Bristol acquired a Northrop Model 8A-1, the export version of the [[Northrop A-17|A-17]] attack bomber, and modified it as a testbed for the first Hercules engines.<ref>{{cite web |url=http://www.flightglobal.com/pdfarchive/view/1937/1937%20-%202787.html |title=Something Up Its Sleeve |website=www.flightglobal.com |url-status=dead |archive-url=https://web.archive.org/web/20180122001017/https://www.flightglobal.com/pdfarchive/view/1937/1937%20-%202787.html |archive-date=2018-01-22}}</ref>

In 1939 Bristol developed a [[Modular design|modular]] engine installation for the Hercules, a so-called "[[power-egg]]", allowing the complete engine and cowling to be fitted to any suitable aircraft.<ref>{{cite web |url=http://www.flightglobal.com/pdfarchive/view/1939/1939-1-%20-%201270.html |title=1939 {{!}} 1- - 1270 {{!}} Flight Archive |website=www.flightglobal.com |url-status=dead |archive-url=https://web.archive.org/web/20140302202359/http://www.flightglobal.com/pdfarchive/view/1939/1939-1-%20-%201270.html |archive-date=2014-03-02}}</ref>

A total of over 57,400 Hercules engines were built.

==Variants==
[[File:Varsity-WF369-01.jpg|thumb|right|Hercules fitted to a [[Vickers Varsity]] on display at the [[Newark Air Museum]]]]
[[File:Bristol Hercules Kbely.JPG|thumb|Bristol Hercules in Aviation Museum Kbely, Prague]]
[[File:bristol.hercules.arp.750pix.jpg|thumb|right|Bristol Hercules engine. Note the absence of pushrods on the cylinders. Each cylinder has two exhaust ports on the front (short L-shaped tubes) and three intake ports on the back supplied through a single manifold.]]
[[File:Bristol Hercules XVII Aircraft engine - side.jpg|thumbnail|Bristol Hercules XVII engine]]

'''Hercules I''' (1936) – {{cvt|1150|hp|kW}}, single-speed [[supercharger]], run on 87 [[Octane rating|octane]] fuel.{{sfnp|Lumsden|1994|p=119}}

'''Hercules II''' (1938) – {{cvt|1375|hp|kW}}, single-speed supercharger, run on 87 octane fuel.{{sfnp|Lumsden|1994|p=119}}

'''Hercules III''' (1939) – {{cvt|1400|hp|kW}}, two-speed supercharger, run on either 87 or 100 octane fuel.{{sfnp|Lumsden|1994|p=120}}

'''Hercules IV''' (1939) – {{cvt|1380|hp|kW}}, single-speed supercharger, run on 87 octane fuel.{{sfnp|Lumsden|1994|p=120}}

'''Hercules V''' (1939) – {{cvt|1380|hp|kW}}, civil prototype derived from the Hercules IV but not developed.{{sfnp|Lumsden|1994|p=120}}

'''Hercules VI''' (1941) – {{cvt|1615|hp|kW}}, two-speed supercharger, run on either 87 or 100 octane fuel.{{sfnp|Lumsden|1994|p=120}}

'''Hercules VII''' production cancelled.{{sfnp|Lumsden|1994|p=120}}

'''Hercules VIII''' – {{cvt|1650|hp|kW}}, very high-altitude version of the Hercules II, single-speed supercharger with an auxiliary high-altitude single-speed 'S' supercharger.{{sfnp|Lumsden|1994|p=120}}

'''Hercules X''' (1941) – {{cvt|1420|hp|kW}}, derived from the Hercules III.{{sfnp|Lumsden|1994|pp=120-121}}

'''Hercules XI''' (1941) – {{cvt|1590|hp|kW}}, derived from the Hercules III, run on 100 octane fuel.{{sfnp|Lumsden|1994|p=121}}

'''Hercules XII''' – derived from the Hercules IV.{{sfnp|Lumsden|1994|p=121}}

'''Hercules XIV''' (1942) – {{cvt|1500|hp|kW}}, developed for the civil market and used by [[BOAC]], run on 100 octane fuel.{{sfnp|Lumsden|1994|p=121}}

'''Hercules XVMT''' – {{cvt|1650|hp|kW}}, very high-altitude development of the Hercules II, single-speed supercharger with an auxiliary high-altitude [[turbo-supercharger]].{{sfnp|Lumsden|1994|p=121}}

'''Hercules XVI''' (1942) – {{cvt|1615|hp|kW}}, two-speed supercharger, run on either 87 or 100 octane fuel.{{sfnp|Lumsden|1994|p=121}}

'''Hercules XVII''' (1943) – {{cvt|1615|hp|kW}}, two-speed supercharger locked in 'M' gear.{{sfnp|Lumsden|1994|p=121}}

'''Hercules XVIII''' – low-level development of the Hercules VI with cropped {{cvt|12|in|mm}} supercharger [[impeller]]s.{{sfnp|Lumsden|1994|p=121}}

'''Hercules XIX''' (1943) – {{cvt|1725|hp|kW}}, a development of the Hercules XVII, the two-speed supercharger had cropped {{cvt|12|in|mm}} impellers locked in 'M' gear.{{sfnp|Lumsden|1994|p=121}}

'''Hercules XX''' – similar to the Hercules XIX.{{sfnp|Lumsden|1994|p=121}}

'''Hercules 36''' – a development engine derived from the Hercules VI and Hercules XVI, run on 100 octane fuel. The '''Hercules 38''' was a further development of the Hercules 36.{{sfnp|Lumsden|1994|p=121}}

'''Hercules 100''' (1944) – {{cvt|1675|hp|kW}}, the first in a new sub-series of Hercules engines designed primarily for the impending post-war civil market. The entire series was split, some versions had standard [[Epicyclic gearing|epicyclic reduction gearing]] and parallel versions had a new [[torquemeter]]-type reduction gearing.{{sfnp|Lumsden|1994|pp=121-122}}

'''Hercules 101''' – {{cvt|1675|hp|kW}}, developed from the Hercules 100. The '''Hercules 103''' was the torquemeter version. The '''Hercules 110''' was a further development of the Hercules 101.{{sfnp|Lumsden|1994|p=122}}

'''Hercules 105''' – {{cvt|1675|hp|kW}}, developed from the Hercules 101 with modified supercharger gears.{{sfnp|Lumsden|1994|p=122}}

'''Hercules 106''' – {{cvt|1675|hp|kW}}, developed from the Hercules 101. The '''Hercules 107''' was the torquemeter version.{{sfnp|Lumsden|1994|p=122}}

'''Hercules 120''' – {{cvt|1715|hp|kW}}, high-altitude development of the Hercules 101. The '''Hercules 121''' was the torquemeter version. The '''Hercules 200''' was further modified version of the Hercules 120.{{sfnp|Lumsden|1994|p=122}}

'''Hercules 130''' – {{cvt|1715|hp|kW}}, development of the Hercules 100. The '''Hercules 134''' was a development with modified mounting ring and exhaust pipes for a rear manifold.{{sfnp|Lumsden|1994|p=122}}

'''Hercules 216''' – {{cvt|1675|hp|kW}}, development of the Hercules 106 with the Hercules 230 power section and single speed supercharger. Applications:{{sfnp|Lumsden|1994|p=122}}

'''Hercules 230''' – {{cvt|1925|hp|kW}}, development of the Hercules 130 with the re-designed power section and modified mounting ring and exhaust pipes for a rear manifold. The '''Hercules 270''' was a development. The '''Hercules 231''' and '''Hercules 271''' were the torquemeter versions.{{sfnp|Lumsden|1994|pp=122-123}}

'''Hercules 232''' – modified development of the Hercules 230 for improved performance. The '''Hercules 233''' was the torquemeter version.{{sfnp|Lumsden|1994|p=122}}

'''Hercules 234''' – modified development of the Hercules 232. The '''Hercules 235''' was the torquemeter version. The '''Hercules 238''' was a military version of the Hercules 734 which itself was based on the Hercules 234.{{sfnp|Lumsden|1994|p=122}}

'''Hercules 260''' – modified development of the Hercules 230 to suit [[reversible propeller]]s. The '''Hercules 261''' was the torquemeter version.{{sfnp|Lumsden|1994|p=123}}

'''Hercules 264''' – {{cvt|1950|hp|kW}}, a development of the Hercules 260. The '''Hercules 265''' was the torquemeter version.{{sfnp|Lumsden|1994|p=123}}

'''Hercules 268''' – a further development of the Hercules 260. The '''Hercules 269''' was the torquemeter version.{{sfnp|Lumsden|1994|p=123}}

'''Hercules 630''' – {{cvt|1675|hp|kW}}, a civil development of the Hercules 100. The '''Hercules 631''' was the torquemeter version.{{sfnp|Lumsden|1994|p=123}}

'''Hercules 632''' – {{cvt|1690|hp|kW}}, a civil-series engine developed from the Hercules 630. The '''Hercules 633''' was the torquemeter version. The '''Hercules 638''' and '''Hercules 672''', along with their torquemeter versions the '''Hercules 639''' and '''Hercules 673''' were developments of the Hercules 632.{{sfnp|Lumsden|1994|pp=123–124}}

'''Hercules 634''' – {{cvt|1690|hp|kW}}, a civil-series engine developed from the Hercules 630 with modified mounting ring and exhaust pipes for a rear manifold. The '''Hercules 635''' was the torquemeter version.{{sfnp|Lumsden|1994|p=123}}

'''Hercules 636''' – a civil-series engine developed from the Hercules 630 with modified mounting ring and exhaust pipes for a rear manifold. The '''Hercules 637''' was the torquemeter version. The '''Hercules 637-2''' and '''Hercules 637-3''' were further torquemeter developments.{{sfnp|Lumsden|1994|p=123}}

'''Hercules 730''' – {{cvt|2040|hp|kW}}, a civil-series engine developed from the Hercules 230 and 630 with improved power section, the '''Hercules 731''' was the torquemeter version.{{sfnp|Lumsden|1994|p=124}}

'''Hercules 732''' – a civil-series engine developed from the Hercules 730 with modified mounting ring and exhaust pipes for a rear manifold. The '''Hercules 733''' was the torquemeter version.{{sfnp|Lumsden|1994|p=124}}

'''Hercules 734''' – {{cvt|1980|hp|kW}}, a civil-series engine developed from the Hercules 730. The '''Hercules 735''' was the torquemeter version. The '''Hercules 238''' was a military version of the civil Hercules 734.{{sfnp|Lumsden|1994|pp=123–124}}

'''Hercules 736''' – {{cvt|2040|hp|kW}}, a civil-series engine developed from the Hercules 730. The '''Hercules 737''' was the torquemeter version.{{sfnp|Lumsden|1994|p=124}}

'''Hercules 738''' – a civil-series engine developed from the Hercules 730.{{sfnp|Lumsden|1994|p=124}}

'''Hercules 739''' – the torquemeter version of the Hercules 738.{{sfnp|Lumsden|1994|p=124}}

'''Hercules 750''' – a civil-series engine developed from the Hercules 730 to suit braking propellers. The '''Hercules 751''' was the torquemeter version.{{sfnp|Lumsden|1994|p=124}}

'''Hercules 758''' – {{cvt|2080|hp|kW}}, a civil-series development of the Hercules 750, the '''Hercules 759''' was the torquemeter version. The '''Hercules 790''' and its torquemeter version the '''Hercules 790''' were further developed from the Hercules 758.{{sfnp|Lumsden|1994|pp=124–125}}

'''Hercules 760''' – a civil-series engine developed from the Hercules 730.{{sfnp|Lumsden|1994|p=124}}

'''Hercules 762''' – {{cvt|2080|hp|kW}}, a civil-series high-altitude development of the Hercules 730 with modified supercharger. The '''Hercules 763''' was the torquemeter version.{{sfnp|Lumsden|1994|p=124}}

'''Hercules 772''' – {{cvt|1965|hp|kW}}, a civil-series development of the Hercules 762. The '''Hercules 773''' was the torquemeter version.{{sfnp|Lumsden|1994|p=125}}

==Applications==
Bristol Hercules uses:{{sfnp|Lumsden|1994|pp=119−125}}
{{div col}}
* [[Armstrong Whitworth Albemarle]]
* [[Avro Lancaster]] Mk II
* [[Avro Tudor]] VII
* [[Avro York]] Mk II
* [[Bréguet 890 Mercure|Bréguet 890H Mercure]] prototype
* [[Bristol Beaufighter]]
* [[Bristol Freighter]]
* [[CASA C-207 Azor]]
* [[Fokker T.IX]]
* [[Folland Fo.108]]
* [[Blackburn Beverley|GAL Universal Freighter]]
* [[Handley Page Halifax]]
* [[Handley Page Halifax|Handley Page Halton]]
* [[Handley Page Hastings]]
* [[Handley Page Hermes]]
* [[Nord Noratlas]]
* [[Nord Noroit]]
* [[Northrop Gamma 2L]]
* [[Saunders-Roe A.36 Lerwick|Saro A.36 Lerwick]]
* [[Short S.26]]
* [[Short Seaford]]
* [[Short Solent]]
* [[Short Stirling]]
* [[SNCASE SE-1010]]
* [[Vickers Valetta]]
* [[Vickers Varsity]]
* [[Vickers VC.1 Viking]]
* [[Vickers Wellesley]]
* [[Vickers Wellington]]
{{div col end}}

==Engines on display==
* RAF Snaith Museum https://www.facebook.com/RAFSnaith/
* A Bristol Hercules is on public display at the [[City of Norwich Aviation Museum]] in [[Horsham St Faith|Horsham St Faith, Norfolk]].<ref>{{cite web |title=Engines List |url=http://www.cnam.org.uk/engines-list |website=City of Norwich Aviation Museum |access-date=27 August 2023}}</ref>
* Two incomplete and badly corroded examples from aircraft lost in the vicinity of Texel and recovered from the sea are on display at the [[Museum Kaapskil]] in Oudeschild, Texel, NL.

==Specifications (Hercules II)==
{{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.''{{sfnp|Lumsden|1994|p=119}}
|type=14-cylinder, two-row, supercharged, air-cooled [[radial engine]]
|bore={{convert|5.75|in|mm|0|abbr=on}}
|stroke={{convert|6.5|in|mm|0|abbr=on}}
|displacement={{convert|2,360|cuin|L|abbr=on}}
|length={{convert|53.15|in|mm|abbr=on}}
|diameter={{convert|55|in|mm|abbr=on}}
|width=
|height=
|weight={{convert|1,929|lb|kg}}
|valvetrain=Gear-driven [[sleeve valve]]s with five ports per sleeve — three intake and two exhaust
|supercharger=Single-speed [[centrifugal type supercharger]]
|turbocharger=
|fuelsystem=[[Claudel-Hobson]] [[carburetor|carburettor]]
|fueltype=87 [[octane rating|Octane]] [[gasoline|petrol]]
|oilsystem=
|coolingsystem=Air-cooled
|power=<br />
* {{convert|1,272|hp|kW|abbr=on}} at 2,800&nbsp;rpm for takeoff
* {{convert|1,356|hp|kW|abbr=on}} at 2,750&nbsp;rpm at {{convert|4,000|ft|m|abbr=on}}
|compression=7.0:1
|fuelcon=
|specfuelcon=0.43 lb/(hp•h) (261 g/(kW•h))
|oilcon=
|specpower=0.57&nbsp;hp/in³ (26.15 kW/L)
|power/weight=0.7&nbsp;hp/lb (1.16 kW/kg)
|reduction_gear=[[Farman Aviation Works|Farman]] [[epicyclic gearing]], 0.44:1
}}

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

<!-- designs which were developed into or from this aircraft: -->
|related=
*[[Bristol Perseus]]
*[[Bristol Centaurus]]
<!-- 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=
* [[BMW 801]]
* [[Pratt & Whitney R-1830]]
* [[Pratt & Whitney R-2000]]
* [[Wright R-2600]]
* [[Fiat A.74]]
* [[Fiat A.80]]
* [[Gnome-Rhône 14N]]
* [[Mitsubishi Kinsei]]
* [[Nakajima Sakae]]
* [[Shvetsov ASh-82]]

<!-- See [[WP:Air/PC]] for more explanation of these fields. -->
}}

==References==

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

===Bibliography===
*{{Ref Jane's|||1945}}
* {{cite book |last=Gunston |first=Bill |author-link=Bill Gunston |date=1993 |title=The Development of Piston Aero Engines |location=[[Sparkford]], Somerset |publisher=Haynes Publishing Group P.L.C. |isbn=1-85260-385-2}}
* {{cite book |last=Gunston |first=Bill |author-link=Bill Gunston |date=1995 |title=Classic World War II Aircraft Cutaways |location=Oxford |publisher=Osprey Publishing |isbn=0-7607-1399-5}}
* {{cite book |last=Gunston |first=Bill |author-link=Bill Gunston |date=2006 |title=World Encyclopedia of Aero Engines: From the Pioneers to the Present Day |edition=5th |location=[[Stroud]] |publisher=Sutton |isbn=0-7509-4479-X}}
* {{cite book |last=Lumsden |first=Alec |date=1994 |title=British Piston Engines and Their Aircraft |location=Shrewsbury |publisher=Airlife Publishing Ltd |isbn=1-85310-294-6}}
* {{cite book |last=White |first=Graham |date=1995 |title=Allied Aircraft Piston Engines of World War II: History and Development of Frontline Aircraft Piston Engines Produced by Great Britain and the United States During World War II |location=[[Warrendale, Pennsylvania|Warrendale]] |publisher=[[Society of Automotive Engineers]] |isbn=1-56091-655-9}}

==External links==
{{Commons category|Bristol Hercules}}
* [https://www.youtube.com/watch?v=D6Zw1_NiSWg Running a Hercules for the first time in 30 years]
* [http://t1.gstatic.com/images?q=tbn:ANd9GcTllVJQ9lKIjjxerytL05aZKl1P55hnFEsNhCwl9-7MHD_UC_ihf557hB_Vqg Image of the gear system for the sleeve drive]
*[http://www.flightglobal.com/pdfarchive/view/1948/1948%20-%200222.html "Safety through engine development testing"] a 1948 advert for the Hercules in ''Flight'' magazine
*[http://www.flightglobal.com/pdfarchive/view/1948/1948%20-%201284.html "600 Hours between overhaul"] a 1948 ''Flight'' advertisement for the Hercules

{{Bristol aeroengines}}

[[Category:Bristol aircraft engines|Hercules]]
[[Category:Aircraft air-cooled radial piston engines]]
[[Category:Sleeve valve engines]]
[[Category:1930s aircraft piston engines]]