Politics.be - telkens een sos probeert fel te doen...

Wiki Loves Heritage

Photograph heritage,?*
help Wikipedia and win!

Open main menu

EditWatch this page

Read in another languageRolls-Royce Merlin

The?*Rolls-Royce Merlin?*is a British?*liquid-cooled?*V-12?*piston?*aero engine?*of 27-litres?*(1,650?*cu in)?*capacity.?*Rolls-Royce?*designed the engine and first ran it in 1933 as a private venture. Initially known as the?*PV-12, it was later called?*Merlin?*following the company convention of naming its piston aero engines after?*birds of prey.

MerlinThe Rolls-Royce MerlinTypeLiquid-cooled?*V-12piston?*aero engineNational originUnited KingdomManufacturerRolls-Royce LimitedFirst run15 October?*1933Major applicationsAvro Lancaster?*
de Havilland Mosquito?*
Handley Page Halifax
Hawker Hurricane
Supermarine SpitfireNumber built149,659Unit cost£2,000 (engine)
£350 (propeller)[1]VariantsPackard V-1650 MerlinDeveloped intoRolls-Royce Meteor

After several modifications, the first production variants of the PV-12 were completed in 1936. The first operational aircraft to enter service using the Merlin were the?*Fairey Battle,?*Hawker Hurricaneand?*Supermarine Spitfire. The Merlin remains most closely associated with the Spitfire and Hurricane, although the majority of the production run was for the four-engined?*Avro Lancaster?*heavy bomber. A series of rapidly applied developments, brought about by wartime needs, markedly improved the engine's performance and durability. Starting at 1,000?*hp for the first production models, most late war versions produced just under 1,800?*hp, and the very latest version as used in the?*de Havilland Hornet?*over 2,000?*hp.

One of the most successful aircraft engines of the World War II era, some 50 marks of Merlin were built by Rolls-Royce in?*Derby,?*Crewe?*and?*Glasgow, as well as by?*Ford of Britain?*at their?*Trafford Park factory, near?*Manchester.[2][3]?*A de-rated version was also the basis of the successful?*Rolls-Royce/Rover Meteor?*tank engine. Post-war, the Merlin was largely superseded by the?*Rolls-Royce Griffon?*for military use, with most Merlin variants being designed and built for?*airliners?*and?*military transport aircraft. Production ceased in 1956 with the fulfilment of an order for 170 Merlins for the Spanish Air Force's?*CASA 2.111?*and?*Hispano Aviación HA-1112?*aircraft,[4]?*after 160,000 engines had been delivered.[5]?*In addition, the?*Packard V-1650?*was a version of the Merlin built in the United States, itself produced in numbers upwards of 55,000 examples, and was the principal engine used in the?*North American P-51 Mustang.

Merlin engines remain in?*Royal Air Force?*service today with the?*Battle of Britain Memorial Flight, and power many restored aircraft in private ownership worldwide.

Contents

Design and developmentEdit

OriginEdit

In the early 1930s, Rolls-Royce started planning its future aero-engine development programme and realised there was a need for an engine larger than their 21-litre (1,296?*cu in)?*Kestrel?*which was being used with great success in a number of 1930s aircraft.[6]Consequently, work was started on a new 1,100?*hp?*(820?*kW)-class design known as the PV-12, with PV standing for?*Private Venture, 12-cylinder, as the company received no government funding for work on the project. The PV-12 was first run on 15 October 1933 and first flew in a?*Hawker Hart?*biplane (serial number?*K3036) on 21 February 1935.[7]?*The engine was originally designed to use the?*evaporative cooling?*system then in vogue. This proved unreliable and when?*ethylene glycol?*from the U.S. became available, the engine was adapted to use a conventional liquid-cooling system. The Hart was subsequently delivered to Rolls-Royce where, as a Merlin?*testbed, it completed over 100 hours of flying with the Merlin C and E engines.[8]

In 1935, the?*Air Ministry?*issued a specification,?*F10/35, for new?*fighter aircraft?*with a minimum airspeed of 310?*mph?*(500?*km/h). Fortunately, two designs had been developed: the?*Supermarine Spitfire?*and the?*Hawker Hurricane; the latter designed in response to another specification, F36/34.[9]?*Both were designed around the PV-12 instead of the Kestrel, and were the only contemporary British fighters to have been so developed. Production contracts for both aircraft were placed in 1936, and development of the PV-12 was given top priority as well as government funding. Following the company convention of naming its piston aero engines after birds of prey, Rolls-Royce named the engine the?*Merlin?*after a small, Northern Hemisphere falcon (Falco columbarius).[nb 1][10]

Two more Rolls-Royce engines developed just prior to the war were added to the company's range. The 885?*hp (660?*kW)?*Rolls-Royce Peregrine?*was an updated,?*superchargeddevelopment of their V-12 Kestrel design, while the 1,700?*hp (1,300?*kW) 42-litre (2,560 cu in)?*Rolls-Royce Vulture?*used four Kestrel-sized?*cylinder blocks?*fitted to a single?*crankcase?*and driving a common crankshaft, forming an?*X-24?*layout.[11]?*This was to be used in larger aircraft such as the?*Avro Manchester.[12]

Although the Peregrine appeared to be a satisfactory design, it was never allowed to mature since Rolls-Royce's priority was refining the Merlin. As a result, the Peregrine saw use in only two aircraft: the?*Westland Whirlwind?*fighter and one of the?*Gloster F.9/37?*prototypes. The Vulture was fitted to the?*Avro Manchester?*bomber, but proved unreliable in service and the planned fighter using it – the?*Hawker Tornado?*– was cancelled as a result.[13]?*With the Merlin itself soon pushing into the 1,500?*hp (1,100?*kW) range, the Peregrine and Vulture were both cancelled in 1943, and by mid-1943 the Merlin was supplemented in service by the larger?*Griffon.[14]?*The Griffon incorporated several design improvements and ultimately superseded the Merlin.

DevelopmentEdit

Initially the new engine was plagued with problems, such as failure of the accessory gear trains and coolant jackets, and several different construction methods were tried before the basic design of the Merlin was set.[15]?*Early production Merlins were also unreliable: Common problems were cylinder head cracking, coolant leaks, and excessive wear to the?*camshafts?*and?*crankshaft?*main bearings.[16]

Early enginesEdit

The prototype, developmental, and early production engine types were the:

PV-12The initial design using an evaporative cooling system. Two built, passed?*bench?*type testing?*in July 1934, generating 740 horsepower (552?*kW) at 12,000-foot (3,700?*m) equivalent. First flown 21 February 1935.[7]Merlin BTwo built, ethylene glycol liquid cooling system introduced. "Ramp"?*cylinder heads?*(inlet valves?*were at a 45-degree?*angle to the cylinder). Passed Type Testing February 1935, generating 950 horsepower (708?*kW) at 11,000-foot (3,400?*m) equivalent.[7]Merlin CDevelopment of Merlin B;?*crankcase?*and?*cylinder blocks?*became three separate?*castingswith bolt-on cylinder heads.[7]?*First flight in?*Hawker Horsley?*21 December 1935, 950 horsepower (708?*kW) at 11,000-foot (3,400?*m).[17]Merlin ESimilar to?*C?*with minor design changes. Passed 50-hour civil test in December 1935 generating a constant 955 horsepower (712?*kW) and a maximum rating of 1,045 horsepower (779?*kW). Failed military 100-hour test in March 1936. Powered the Supermarine Spitfire prototype.[18]

Parallel valve Merlin cylinder head

Merlin F?*(Merlin I)Similar to?*C?*and?*E. First flight in Horsley 16 July 1936.[19]This became the first production engine, and was designated as the Merlin I. The Merlin continued with the "ramp" head, but this was not a success and only 172 were made. The?*Fairey Battle I?*was the first production aircraft to be powered by the Merlin I and first flew on 10 March 1936.[18]Merlin G?*(Merlin II)Replaced "ramp" cylinder heads with parallel pattern heads (valves parallel to the cylinder) scaled up from the Kestrel engine. 400-hour flight endurance tests carried out at?*RAE?*July 1937; acceptance test 22 September 1937.[19]?*It was first widely delivered as the 1,030-horsepower (770?*kW) Merlin II in 1938, and production was quickly stepped up for Fairey Battle II.[18]Merlin IIIMerlin II with standardised de Havilland/Rotol?*SBAC?*propeller shaft, and dual accessory-drive. 1,030-horsepower (770?*kW) at 3,000?*rpm at 10,250 feet at +6.5?*lb boost.[20]?*Formed basis for the?*Rolls-Royce/Rover Meteor?*tank engine"Racing" MerlinRacing engine for 1937/38 "Speed Spitfire" world speed record attempt. Merlin III with strengthened pistons, connecting rods, and gudgeon-pins, running on increased octane fuel, developed 2,160-horsepower (1,610?*kW) at 3,200?*rpm and +27?*lb boost, a power/weight ratio of 0.621?*lb per horsepower. Completed 15 hour endurance run at 1,800-horsepower (1,342?*kW), 3,200?*rpm at +22?*lb boost.[20]Merlin IVMerlin with pressure-water cooling for?*Armstrong Whitworth Whitley IV.Merlin VMerlin for Fairey Battle V.Merlin VIIIMedium-supercharged Merlin developed for?*Fairey Fulmar I, rated 1,010-horsepower (754?*kW) at 2,850?*rpm at 6,750 feet, 1,080-horsepower (805?*kW) at 3,000?*rpm for take-off using 100 octane fuel.