Bristol Jupiter Explained

The Bristol Jupiter is a British nine-cylinder single-row piston radial engine that was built by the Bristol Aeroplane Company. Originally designed late in World War I and known as the Cosmos Jupiter, a lengthy series of upgrades and developments turned it into one of the finest engines of its era.

The Jupiter was widely used on many aircraft designs during the 1920s and 1930s. Thousands of Jupiters of all versions were produced, both by Bristol and abroad under licence.

A turbo-supercharged version of the Jupiter known as the Orion suffered development problems and only a small number were produced. The "Orion" name was later re-used by Bristol for an unrelated turboprop engine.

The Bristol Jupiter was licensed by the Soviet Union as the Shvetsov M-22.

Design and development

The Jupiter was designed during World War I by Roy Fedden of Brazil Straker and later Cosmos Engineering. The first Jupiter was completed by Brazil Straker in 1918 and featured three carburettors, each one feeding three of the engine's nine cylinders via a spiral deflector housed inside the induction chamber.^[1] During the rapid downscaling of military spending after the war, Cosmos Engineering became bankrupt in 1920, and was eventually purchased by the Bristol Aeroplane Company on the strengths of the Jupiter design and the encouragement of the Air Ministry.^[2] The engine matured into one of the most reliable on the market. It was the first air-cooled engine to pass the Air Ministry full-throttle test, the first to be equipped with automatic boost control, and the first to be fitted to airliners.^[3]

The Jupiter was fairly standard in design, but featured four valves per cylinder, which was uncommon at the time. The cylinders were machined from steel forgings, and the cast cylinder heads were later replaced with aluminium alloy following studies by the Royal Aircraft Establishment. In 1927, a change was made to move to a forged head design due to the rejection rate of the castings. The Jupiter VII introduced a mechanically-driven supercharger to the design, and the Jupiter VIII was the first to be fitted with reduction gears.^[4]

In 1925, Fedden started designing a replacement for the Jupiter. Using a shorter stroke to increase the revolutions per minute (rpm), and including a supercharger for added power, resulted in the Bristol Mercury of 1927. Applying the same techniques to the original Jupiter-sized engine in 1927 resulted in the Bristol Pegasus. Neither engine would fully replace the Jupiter for a few years.

In 1926 a Jupiter-engined Bristol Bloodhound with the registration G-EBGG completed an endurance flight of 25074miles, during which the Jupiter ran for a total of 225 hours and 54 minutes without part failure or replacement.^[5]

Licensed production

The Jupiter saw widespread use in licensed versions, with fourteen countries eventually producing the engine. In France, Gnome-Rhone produced a version known as the Gnome-Rhône 9 Jupiter that was used in several local civilian designs, as well as achieving some export success. Siemens-Halske took out a licence in Germany and produced several versions of increasing power, eventually resulting in the Bramo 323 Fafnir, which saw use in German wartime aircraft.^[6]

In Japan, the Jupiter was licence-built from 1924 by Nakajima, forming the basis of its own subsequent radial aero-engine design, the Nakajima Ha-1 Kotobuki.^[7] It was produced in Poland as the PZL Bristol Jupiter, in Italy as the Alfa Romeo 126-RC35,^[8] and in Czechoslovakia by Walter Engines. The most produced version was in the Soviet Union, where its Shvetsov M-22 version powered the initial Type 4 version of the Polikarpov I-16 (55 units produced). Type 4 Polikarpovs can be identified by their lack of exhaust stubs, rounded NACA cowling and lack of cowling shutters, features which were introduced on the Shvetsov M-25 powered Type 5 and later variants (total production 4,500+ units).^[9] ^[10] Production started in 1918 and ceased in 1930.

Variants

The Jupiter was produced in many variants, one of which was the Bristol Orion of 1926. Metallurgy problems with this turbo-supercharged engine caused the project to be abandoned after only nine engines had been built.^[11]

Brazil Straker (Cosmos) Jupiter I

(1918) 400hp; only two engines assembled.

Cosmos Jupiter II

(1918) 400hp; a single engine assembled.

Bristol Jupiter II

(1923) 400hp.

Bristol Jupiter III

(1923) 400hp.

Bristol Jupiter IV

(1926) 430hp; fitted with variable valve timing and a Bristol Triplex carburettor.

Bristol Jupiter V

(1925) 480hp.

Bristol Jupiter VI

(1927) 520hp; produced in both high- (6.3:1) and low- (5.3:1) compression ratio versions.

Bristol Jupiter VIA

(1927) 440hp; civil version of Jupiter VI.

Bristol Jupiter VIFH

(1932) 440hp; version of Jupiter VI equipped with gas starter motor.

Bristol Jupiter VIFL

(1932) 440hp; version of Jupiter VI with compression ratio of 5.15:1.

Bristol Jupiter VIFM

(1932) 440hp; version of Jupiter VI with compression ratio of 5.3:1.

Bristol Jupiter VIFS

(1932) 400hp; version of Jupiter VI with compression ratio of 6.3:1.

Bristol Jupiter VII

(1928) 375hp; fitted with supercharger, with compression ratio of 5.3:1; also manufactured by Gnome-Rhone as the 9ASB.

Bristol Jupiter VIIF

(1929) 480hp; version of Jupiter VII with forged cylinder heads.

Bristol Jupiter VIIFP

(1930) 480hp; version of Jupiter VII with pressure feed lubrication to wrist-pins.

Bristol Jupiter VIII

(1929) 440hp; first version with propeller reduction gearing;^[12] compression ratio 6.3:1.

Bristol Jupiter VIIIF

(1929) 460hp; version of Jupiter VIII with forged cylinder heads and lowered compression ratio (5.8:1).

Bristol Jupiter VIIIFP

(1929) 460hp; version of Jupiter VIII with pressure feed lubrication (time between overhauls at this stage in development was only 150 hours due to multiple failures).

Bristol Jupiter IX

480hp; compression ratio 5.3:1.

Bristol Jupiter IXF

550hp; version of Jupiter IX with forged cylinder heads

Bristol Jupiter X

470hp; compression ratio 5.3:1.

Bristol Jupiter XF

540hp; version of Jupiter X with forged cylinder heads

Bristol Jupiter XFA

483hp

Bristol Jupiter XFAM

580hp

Bristol Jupiter XFBM

580hp

Bristol Jupiter XFS

Fully supercharged.

Bristol Jupiter XI

Compression ratio 5.15:1.

Bristol Jupiter XIF

500hp; compression ratio 5.15:1.

Bristol Jupiter XIFA

480hp; version of Jupiter XIF with 0.656:1 propeller gear reduction ratio

Bristol Jupiter XIFP

525hp; version of Jupiter XIF with pressure feed lubrication.

Bristol Orion I

(1926) Jupiter III, turbo-supercharged, abandoned programme.

Gnome-Rhône 9A Jupiter:French licence production primarily of 9A, 9Aa, 9Ab, 9Ac, 9Akx and 9Ad variants.

Siemens-Halske took out a licence in Germany and produced several versions of increasing power, eventually resulting in the Bramo 323 Fafnir, which saw use in wartime models.

Nakajima Ha-1 Kotobuki

In Japan, the Jupiter was licence-built from 1924 by Nakajima.

PZL Bristol Jupiter: Polish production.

Italian licence production, 420hp.

Alfa 126 R.C.35

Alfa Romeo developed variant

Walter Jupiter: Licence production in Czechoslovakia by Walter Engines

Applications

The Jupiter is probably best known for powering the Handley Page H.P.42 airliners, which flew the London-Paris route in the 1930s. Other civilian uses included the de Havilland Giant Moth and de Havilland Hercules, the Junkers G 31 and the huge Dornier Do X flying boat, which used no less than twelve engines.

Military uses were less common, but included the parent company's Bristol Bulldog, as well as the Gloster Gamecock and Boulton Paul Sidestrand. It was also found in prototypes around the world, from Japan to Sweden.

By 1929 the Bristol Jupiter had flown in 262 different aircraft types,^[13]

Note:^[14]

Cosmos Jupiter

Bristol Jupiter

Gnome-Rhône Jupiter

Shvetsov M-22

Engines on display

A Bristol Jupiter VI is on static display at Aerospace Bristol in the former Bristol Aeroplane Company factory complex in Filton, a suburb of Bristol, United Kingdom.^[16]
A Bristol Jupiter VIIF is on static display at the Shuttleworth Collection in Old Warden, United Kingdom.
A Bristol Jupiter VIIIF is on static display at the Steven F. Udvar-Hazy Center of the National Air and Space Museum at Washington Dulles International Airport in Fairfax County, Virginia, United States.^[12]
A Bristol Bulldog complete with a Jupiter VIIFP engine is on static display at the Royal Air Force Museum London in Hendon, United Kingdom.^[17] ^[18]

References

Bibliography

Bridgman, L. (ed.) Jane's Fighting Aircraft of World War II. New York: Crescent Books, 1998.
Lumsden, Alec. British Piston Engines and their Aircraft. Marlborough, Wiltshire: Airlife Publishing, 2003. .
Gunston, Bill. Development of Piston Aero Engines. Cambridge, England. Patrick Stephens Limited, 2006.
Gunston, Bill. World Encyclopedia of Aero Engines. Cambridge, England. Patrick Stephens Limited, 1989.
. 9 March 1939 . Rise of the Radials . . XXXV . 1576 . 236–244 . G. Geoffrey. Smith . 17 May 2018.

External links

3 July 1919 . The Cosmos Aero Engines . . XI . 27 . No. 549 . 869–871 . 12 January 2011 . Contemporary article on Cosmos Engineering's air-cooled radial engines. Photos of the Cosmos Jupiter are on page 870, and a short technical description is on page 871.
Bristol Jupiter endurance test - Flight, March 1926
A 1929 Flight advertisement for the Jupiter

Notes and References

Flight 9 March 1939, pp.236-237
Gunston 1989, p.44.
Gunston 1989, p.31.
Bridgman (Jane's) 1998, p.270.
Web site: 1926 0183 Flight Archive . www.flightglobal.com . dead . https://web.archive.org/web/20121019142218/http://www.flightglobal.com/pdfarchive/view/1926/1926%20-%200183.html . 2012-10-19.
Gunston 1989, p.29.
Gunston 1989, p.104.
Web site: Alfa Aero Engines . 25 August 2007 . aroca-qld.com . https://web.archive.org/web/20071008150746/http://www.aroca-qld.com/library_articles/alfa_romeo_aero_engines.php . 8 October 2007 . dead .
Web site: Modeling the VVS: I-16 Development.
Gunston 1989, p.158.
Lumsden 2003, p.101.
Web site: Bristol Jupiter VIIIF Radial Engine . National Air and Space Museum . Smithsonian Institution . 13 May 2018.
Web site: The Bristol Jupiter Aircraft Engine. Air Power World. 2 October 2017.
British aircraft list from Lumsden, the Jupiter may not be the main powerplant for these types
OKB YAKOVLEV, Yefim Gordon, Dmitriy Komissarov, Sergey Komissarov, 2005, Midland Publishing pp 28-29
Web site: Things to See and Do . Aerospace Bristol . Bristol Aero Collection Trust . 13 May 2018.
Web site: Bristol Bulldog MkIIA . rafmuseum.org . Trustees of the Royal Air Force Museum . 13 May 2018.
Web site: Individual History: Bristol Bulldog MkIIA G-ABBB/'K2227', Museum Accession Number 1994/1386/A . rafmuseum.org . Trustees of the Royal Air Force Museum . 13 May 2018.