Bristol Hercules

The Bristol Hercules was a 14-cylinder two-row radial aircraft engine designed by Sir Roy Fedden and produced by the Bristol Engine Company starting in 1939. It was the first of their sleeve valve designs to see widespread use, powering many aircraft in the mid-World War II time frame.

Design and development

The rationale behind the sleeve-valve design was to provide optimum intake and exhaust gas flow in a two-row radial engine, improving its volumetric efficiency. The arrangement of the cylinders in two-row radials made it very difficult to utilize four valves per cylinder and all non-sleeve valve two- and four-row radials were limited to two valves.

Bristol had introduced their first sleeve valve designs in the 750 horsepower (560 kW) class Perseus and the 500 hp (370 kW) class Aquila, which 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 Taurus.

The first Hercules engines were available in 1939 as the 1,290 hp (960 kW) Hercules I, soon improved to 1,375 hp (1,025 kW) in the Hercules II. The major version was the Hercules VI which delivered 1,650 hp (1,230 kW), and the late-war Hercules XVII produced 1,735 hp (1,294 kW).

The Hercules powered a number of aircraft including Bristol's own Beaufighter heavy fighter design although it was more commonly used on bombers. The Hercules also saw use in civilian designs. The design was also licensed for production in France by SNECMA. It was considered to be one of the most reliable aircraft engines of the era, and was well liked by both pilots and mechanics.

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

Applications

* Armstrong Whitworth Albemarle
* Avro Lancaster
* Bristol Beaufighter
* Bristol Freighter
* Handley Page Halifax
* Handley Page Hastings
* Handley Page Hermes
* Nord Noratlas
* Saro Lerwick
* Short S.26
* Short Seaford
* Short Solent
* Short Stirling
* Vickers Valetta
* Vickers Varsity
* Vickers VC.1 Viking
* Vickers Wellington

Specifications (Hercules II)

pistonspecs

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type=Fourteen-cylinder two-row supercharged air-cooled radial engine
bore=5.75 in (146 mm)
stroke=6.5 in (165 mm)
displacement=2,362 in³ (38.7 L)
length=53.15 in (1,350 mm)
diameter=51.97 in (1,320 mm)
width=
height=
weight=1,929 lb (875 kg)
valvetrain=Gear-driven sleeve valves with five ports per sleeve — three intake and two exhaust
supercharger=Single-speed centrifugal type supercharger
turbocharger=
fuelsystem=Claudel-Hobson carburetor
fueltype=87 octane rating gasoline
oilsystem=
coolingsystem=Air-cooled
power=
* 1,272 hp (949 kW) at 2,800 rpm for takeoff
* 1,356 hp (1,012 kW) at 2,750 rpm at 4,000 ft (1,220 m)
compression=7.0:1
fuelcon=
specfuelcon=0.43 lb/(hp•h) (261 g/(kW•h))
oilcon=
specpower=0.57 hp/in³ (26.15 kW/l)
power/weight=0.7 hp/lb (1.16 kW/kg)
reduction_gear=Farman epicyclic gearing, 0.44:1

See also

Comparable engines

* BMW 801
* Pratt & Whitney R-1830
* Wright R-2600
* Fiat A.74
* Gnome-Rhône 14N
* Mitsubishi Kinsei
* Nakajima Sakae
* Shvetsov ASh-82

Related lists

* List of aircraft engines

References

* Gunston, B. (1995) "Classic World War II Aircraft Cutaways." Osprey. ISBN 1-85532-526-8
*

External links