Rolls-Royce Merlin

Birth

The development was undertaken in the form of an private initiative on capital stock own of Henry Royce, in 1932, under the name of PV-12 (statement for private venture). In October 1933, the Air Ministry agrees to finance the development and gives the name of Merlin to the engine. A first version appears in July 1934, the Merlin has , able to provide 790 horses to 2700 turns per minutes. But the engine suffers from many problems, mainly on the level of the gears of the reducer and the shirts of liquid of the cooling system by evaporation. The Merlin B which follows is equipped with four Soupape S per capita of cylinder, using a slope of heads with 45°, as on the engines of car of the mark, tested in February 1935, it provides a power of 950 horses. The Merlin C , sees the manufacture changed by the casting into three parts of the casing and of the two blocks of cylinders, the heads are always on a slope with 45°.

The version E which derives from C, finally succeeds in being enough reliable to pass fifty hours the civil test, providing 955 horses with points to 1045. The F is in preparation when one decides to create the Merlin G which uses an increased alternative of the slope of heads parallel with cylinders, this engine appears better passing the test one month before F. the series production is launched, the Merlin F becomes Merlin I , but the production is quickly stopped after 172 specimens, G become Merlin II , satisfying to him knows a mass production then. the engine is tested for the first time in flight in 1935 on a Hawker Hart.

One adopts quickly the ethylene glycol, produced by the Prestone company in the United States, like liquid of cooling. Following the request of the Air Ministry in 1936 to provide modern hunters for RAF, two only being studied and able ones to satisfy the requests are the Hawker Hurricane and the Supermarine Spitfire, all both using Merlin, this one becomes essential with the British effort of war.

First series of engines suffering from a doubtful reliability, Rolls Royce lance then a superb checking routine of the quality which was going to make the fame of its engines. Certain engines were taken at the exit of the assembly lines and one made them turn on a bench, with full power to the breakdown, they were then dismounted to find the part which had yielded, the part was then worked over again to be made more resistant. After two years of this procedure, Merlins had become extremely reliable engines able to turn during eight hours of a mission of bombardment to full mode, without any problem.

Description and characteristic of Merlin 61

Merlin is V-12 gasoline, its two rows of cylinders are with 60°, lighting is done according to the sequence: 1A, 6B, 4A, 3B, 2A, 5B, 6A, 1B, 3A, 4B, 5A, 2B (the cylinder 1A being most distant on the right compared to the pilot).

Each cylinder is equipped with two inlet valves and of two of exhaust, these last are cooled with sodium, and are actuated by a camshaft located on the heads of cylinders. The engine supply is carried out by a carburettor equipped with the automatic check of the richness. The air is provided by a compressor to two stages and two speeds, the flow of air being cooled between the two stages by an exchanger of heat with the liquid of cooling. This last is a mixture of water 70% and 30% of ethylene pressurized glycol. Lubrication is ensured by a circuit of oil which comprises a pump of pressure and two pumps of draining.

mass dries: 745 kg

race: 152,4 mm

boring: 137,2 mm

rolled: 27 liters

ratio of compression: 6:1

fuel rating: 43,3 kw per liter

ratio power by mass: 1,57 kw per kg

power:

1565 ch (1 170 kw) with 3000 turns per minute and 3740 meters of altitude.

1390 ch (1 035 kw) with 3000 turns per minute and 7170 meters of altitude.

Evolution

The improvement of the engine output was done according to two ways, by using fuels with increasingly raised octane numbers and by improving the compressor. These modifications made it possible to thus increase the pressure of admission in the cylinders and to final the engine output, without increasing the cubic capacity. This possibility existed grace, entrre other, with powerful oil industry American, able to provide in quantity these new expensive fuels, on the contrary the Germans who, not having this choice, were obliged to increase the size of their engines which thus appeared less interesting in term of ratio of power by the mass.

The first great evolution appears with the Merlin X which uses a two-speed compressor, whose license was acquired near Farman in 1935, this innovation makes it possible to make consume less power with the mechanical compressor, at low altitude, when it there not need for overfeeding, on the other hand the length of the engine increases. In 1939, the decision to focus itself on fuels with octane number 100 is taken, the pressure of admission limited before to 3 kg/cm2 is changed to 6. The following phase is the work of Stanley Hooker, which largely improves the effectiveness of the compressor, thanks to an aerodynamic work on the flow of air interns with this one. The carburettor is moved to avoid having further to increase the length of the group. These modifications give rise to the Merlin XX which is more powerful in altitude, it indeed provides 1175 horses to more than 6000 meters compared with 1060 to 4500 for Merlin II. Certain alternatives of the engine, however, are optimized for low altitude, with blades of propeller of compressor shortened. One of these new Merlins is the Merlin 45 which equips the Spitfire MkV. Hooker also decides to pass to the compressor on two floors, for the bombers, it mounts upstream a compressor of Rolls Royce Vulture of that basic of Merlin 46, giving rise to the Merlin 60 . However, the rise in temperature and pressure of the mixture now requires to cool it before making it return in the cylinders, where it could clash prematurely. The new engine can then provide its maximum power to nearly 10.000 meters.

Advantages and disadvantage of the food by carburettor

The maintenance of a food per carburettor was a defect often reproached Merlin, this one being able to lead the engine to fix during an abrupt operation in G negative, as for example when one pushes on the handle with brush of the plane. The pilots of Messerschmitt Bf 109 thus often used the advantage that got to them the direct injection to sow a Supermarine Spitfire with their cases. It is however advisable to notice that the use of a carburettor was not without advantage far is necessary some. The feeding system is indeed much simpler to produce and maintain, and more reliable, because of absence of the pumps of cylinder. Moreover, the systems with carburettor make it possible to produce a mixture richer than the systems with injection, thus giving a specific power higher than the engine. These advantages amply compensated for the disadvantage presented by the draining of the engine. Moreover, in March 1941, a small modification of the carburettor, imagined by Miss Tilly Shilling with Farnborough, cured the problem largely, with the introduction of a membrane bored into the tanks which authorized finally the operations in G negative for short periods. In 1943, the arrival of the American carburettors anti-g Bendix-Stromberg, which were assembled on Merlin 66, definitively solved the problem.

American production

At the time of the Battle of England in 1940, the British government decided to provide the plans of the engine to American in the possibility of their defeat. The company Packard Motor Company gave its in September agreement, to launch the production of the engine at the same time for the British and American, by adapting it to the techniques of mass production of American industry. The first two specimens were presented the August 2nd 1941 to the factory of Detroit and the mass production started in 1942.

Use in the armoured tanks

Automobile use

In the years 1960, John Dodd, in Kent in England, mounted the engine in a vehicle of his design called The Beast ( the animal ). Deprived of compressor, it provided 850 horses (some think that it was about Rolls Royce Meteor) and involved a automatic Transmission TH-400 of General Motors on a frame in Glass fiber. Listed in the Guinness Book of the records, The Beast is regarded there as the most powerful road vehicle in the world.

Versions

Production of Rolls Royce

Merlin has July 1934, 790 ch with 2500 turns/min and 4000 meters.
Merlin B February 1935, 4 valves by cylinders, inlet valves on a slope with 45° compared to the heads of cylinder, 950 ch to 3700 meters.
Merlin C block of separately run cylinders, team the Standard Supermarine 300.
Merlin D
Merlin E version improved of C.
Merlin I or Merlin F 172 specimens, inlet valves on a slope with 45° compared to the heads of cylinder.
Merlin II or Merlin G 1030 ch with 3000 turns/min and 5500 meters.
Merlin III
Merlin X two-speed compressing.
Merlin XII use of a mixture of ethylene, Glycol and water under pressure, for the cooling, used on the Spitfire Mk II.
Merlin XX use of fuel with octane number 100 instead of 87,1300 cv.
compressing Merlin 45 at a stage and a speed, equips the Spitfire Mk V.
Merlin 46
Merlin 47 team the Spitfire HF VI
compressing Merlin 60 on two floors, equips the Spitfire Mk IX.
Merlin 61 block of part perfecting cylinders.
Merlin 63 team the Spitfire Mk VIII.
Merlin 65
Merlin 66 cylinder head run separately and screwed on the casing.
Merlin 67
Merlin 76
Merlin 85
Merlin 100
Merlin 130
Merlin 140
Merlin 266 team the Spitfire Mk XVI.
Meteor version intended to equip the armoured tanks, compressor removed and less light use of alloy.

Production of Packard

V-1650-1 used on P-40F
V-1650-3
V-1650-7
V-1650-9
V-1650-11

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