Bristol Mercury

The Bristol Mercury was a 9-cylinder one-row piston radial engine used on British aircraft in the 1930s and 1940s.

History

The Mercury was developed by the Bristol Aeroplane Company in 1925 as their Bristol Jupiter was reaching the end of its lifespan. Although the Mercury initially failed to attract much interest, the Air Ministry eventually funded three prototypes and it became another winner for the designer Roy Fedden.

With the widespread introduction of superchargers to the aviation industry in order to improve altitude performance, Fedden felt it was reasonable to use a small amount of boost at all times in order to improve performance of an otherwise smaller engine. Instead of designing an entirely new block, the existing Jupiter parts were re-used with the stroke reduced by one inch (25 mm). The now-smaller capacity engine was then boosted back to Jupiter power levels, while running at higher rpm and thus requiring a reduction gear for the propeller. The same techniques were applied to the original Jupiter-sized engine to produce the Pegasus.

The Mercury's smaller size was aimed at fighter use, and it powered the Gloster Gauntlet and its successor, the Gloster Gladiator. It was intended that the larger Pegasus would be for bombers, but as the power ratings of both engines rose the Mercury found itself being used in almost all roles. Perhaps its most famous use was in a twin-engine light bomber, the Bristol Blenheim. Outside the United Kingdom, Mercury was licence-built in Poland and used in their PZL P.11 fighters. It was also built by NOHAB in Sweden and used in the Swedish Gloster Gladiator fighters and in the Saab 17 dive-bomber. In Italy, it was built by Alfa Romeo as the Mercurius.

Variants

* Mercury VIII - 730 hp (545 kW) at 2,650 rpm for takeoff, 830 hp (618 kW) at 2,750 rpm maximum continuous power
* Mercury XV - 840 hp (625 kW) at 2,750 rpm at 14,000 ft (4,270 m) maximum power with 87-octane fuel; 995 hp (740 kW) at 2,750 rpm at 9,250 ft (2,820 m) maximum power with 100-octane fuel
* Mercury XX - 870 hp (650 kW) at 2,650 rpm at 4,500 ft (1,370 m) maximum power

pecifications (Mercury VI-S)

pistonspecs

ref=cite book|last=Tsygulev|title=Aviacionnye motory voennykh vozdushnykh sil inostrannykh gosudarstv ( _ru. Авиационные моторы военных воздушных сил иностранных государств)|publisher=Gosudarstvennoe voennoe izdatelstvo Narkomata Oborony Soyuza SSR|location=Moscow|year=1939|url=http://base13.glasnet.ru/text/aviamotory/t.htm]
type=Nine-cylinder single-row supercharged air-cooled radial engine
bore=5.75 in (146 mm)
stroke=6.5 in (165 mm)
displacement=1,519 in³ (24.89 L)
length=
diameter=51.46 in (1,307 mm)
width=
height=
weight=966 lb (438 kg)
valvetrain=Four pushrod-actuated valves per cylinder – 2 intake and 2 sodium-filled exhaust
supercharger=Single-speed centrifugal type supercharger
turbocharger=
fuelsystem=Claudel-Hobson carburetor
fueltype=87 octane rating gasoline
oilsystem=
coolingsystem=Air-cooled
power=
* 612 hp (457 kW) at 2,750 rpm for takeoff
* 636 hp (474 kW) at 2,750 rpm at 15,500 ft (4,730 m)
specpower=0.4 hp/in³ (18.35 kW/l)
compression=6.5:1
fuelcon=
specfuelcon=0.49 lb/(hp•h) (300 g/(kW•h))
oilcon=
power/weight=0.63 hp/lb (1.04 kW/kg)
reduction_gear=Farman epicyclic gearing, 0.5:1

pecifications (Mercury VIII/IX)

pistonspecs

ref=
type=Nine-cylinder single-row supercharged air-cooled radial engine
bore=5.75 in (146 mm)
stroke=6.5 in (165 mm)
displacement=1,519 in³ (24.9 L)
length=
diameter=51.46 in (1,307 mm)
width=
height=
weight=996 lb (452 kg)
valvetrain=Four pushrod-actuated valves per cylinder — 2 intake and 2 sodium-filled exhaust
supercharger=Single-speed centrifugal type supercharger
turbocharger=
fuelsystem=Claudel-Hobson carburetor with automatic mixture control
fueltype=87 octane rating gasoline
oilsystem=
coolingsystem=Air-cooled
power=
* 720 hp (537 kW) at 2,650 rpm for takeoff
* 830 hp (618 kW) at 2,750 rpm at 14,000 ft (4,270 m)
specpower=0.47 hp/in³ (21.57 kW/l)
compression=6.5:1
fuelcon=
specfuelcon=0.52 lb/(hp•h) (319 g/(kW•h))
oilcon=0.28 oz/(hp•h) (11 g/(kW•h))
power/weight=0.72 hp/lb (1.19 kW/kg)
designer=
reduction_gear=Farman epicyclic gearing, 0.572:1 (Mercury VIII) or 0.5:1 (Mercury IX)
components_other=Ignition system: Rotax with automatic spark advance
performance_other=

Applications

;GBR:
*Airspeed Cambridge
*Bristol Blenheim
*Breda Ba.27 ITA
*Fokker D XXI NED
*Fokker G.1 NED
*Gloster Gladiator
*Gloster Gauntlet
*IMAM Ro.30 ITA
*Miles Martinet
*Miles Master
*PZL P.11 POL
*Saab 17 SWE
*Supermarine Sea Otter
*Valmet Vihuri FIN
*Westland Lysander

References

* Bridgman, L, (ed.) (1998) "Jane's fighting aircraft of World War II." Crescent. ISBN 0-517-67964-7

ee also

* Bristol Jupiter
* Bristol Pegasus

External links

* [http://republika.pl/rola1/files/pzl11_start_run_01.mp3 Recorded sound of the Mercury V S2 engine] used in PZL P.11c (mp3 format)