Bristol Jupiter

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Bristol Jupiter engine

The Bristol Jupiter was a British 9-cylinder one-row piston radial engine used in the 1930s and 1940s aircraft. It was built under license in France as the Gnome-Rhone Jupiter and in the Soviet Union as the M-22.

[edit] History

The Jupiter was designed during World War I by Roy Fedden of Cosmos Engineering. During the rapid downscaling of military spending after the war, Cosmos went bankrupt in 1920, and was eventually purchased by Bristol Aeroplane Company on the strengths of the Jupiter design. The engine matured into one of the most reliable on the market. Production started in 1918 and ceased in 1930.

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 heads were later replaced with aluminium alloy following studies by the RAE. In 1927 a change was made to a forged head due to the rejection rate of the castings.

In 1925 Roy Fedden started designing a replacement for the Jupiter. Using a shorter stroke to increase the 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 would fully replace the Jupiter for a few years.

The Jupiter is best known for powering the Handley Page HP.42 Hannibal airliners, which flew the London-Paris route in the 1920s. Other civilian uses included the de Havilland Giant Moth and de Havilland Hercules, the Junkers G 31 (which would evolve into the famous Junkers Ju 52), 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.

The Jupiter saw widespread use in licensed versions, with fourteen countries eventually producing the engine. In France the Gnome-Rhone company produced a version that was used in several local civilian designs, as well as achieving some export success. Siemens-Halske took out a license in Germany and produced several versions of increasing power, eventually resulting in the Bramo 323 Fafnir, which saw use in wartime models. In Japan, the Jupiter was license-built from 1924 by Nakajima, forming the basis of their own subsequent radial aero-engine design, the Kotobuki. The most produced version was in the Soviet Union, where their M-22 version powered the famous Polikarpov I-16, which was built in the thousands.

[edit] Specifications (Jupiter)

General characteristics

Type: 9-cylinder naturally aspirated air-cooled radial engine
Bore: 5.75 in (190 mm)
Stroke: 7.5 in (190 mm)
Displacement: 1,750 in³ (28.7 L)
Dry weight: 730 lb (330 kg)

Components

Valvetrain: Four valves per cylinder, two intake and two exhaust
Cooling system: Air-cooled

Performance

Power output:
- 435 hp (325 kW) at 1,575 rpm maximum continuous power
- 580 hp (430 kW) at 1,950 rpm takeoff power
Specific power: 0.33 hp/in³ (15.0 kW/L)
Compression ratio: 5:1
Power-to-weight ratio: 0.60 hp/lb (0.98 kW/kg)