Rolls-Royce Griffon

Le gros V-12 Griffon de Rolls Royce, 1939, vu sur Wikipedia.en

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The Rolls-Royce Griffon is a British 37-[Vous devez être inscrit et connecté pour voir ce lien] (2,240 [Vous devez être inscrit et connecté pour voir ce lien]) [Vous devez être inscrit et connecté pour voir ce lien], 60-degree [Vous devez être inscrit et connecté pour voir ce lien], liquid-cooled [Vous devez être inscrit et connecté pour voir ce lien] designed and built by [Vous devez être inscrit et connecté pour voir ce lien]. In line with company convention, the Griffon was named after a [Vous devez être inscrit et connecté pour voir ce lien], in this case the [Vous devez être inscrit et connecté pour voir ce lien].

Design work on the Griffon started in 1938 at the request of the [Vous devez être inscrit et connecté pour voir ce lien], for use in new aircraft designs such as the [Vous devez être inscrit et connecté pour voir ce lien]. In 1939 it was also decided that the engine could be adapted for use in the [Vous devez être inscrit et connecté pour voir ce lien]. However development was temporarily put on hold to concentrate efforts on the smaller [Vous devez être inscrit et connecté pour voir ce lien] and the 24 cylinder [Vous devez être inscrit et connecté pour voir ce lien], and the engine did not go into production until the early 1940s.

The Griffon was the last in the line of V-12 aero engines to be produced by Rolls-Royce with production ceasing in 1955.^{[Vous devez être inscrit et connecté pour voir ce lien]} Griffon engines remain in [Vous devez être inscrit et connecté pour voir ce lien] service today with the [Vous devez être inscrit et connecté pour voir ce lien] and also power the last remaining airworthy [Vous devez être inscrit et connecté pour voir ce lien].

Design and development


According to [Vous devez être inscrit et connecté pour voir ce lien]'s memoirs, a de-rated version of the "[Vous devez être inscrit et connecté pour voir ce lien]" engine, known by the name Griffon at that time, was tested in 1933.

This engine, R11, which was never flown, was used for "Moderately Supercharged Buzzard development" (which was not proceeded with until much later), and bore no direct relationship to the volume-produced Griffon of the 1940s.

In 1938 the Fleet Air Arm approached Rolls-Royce and asked whether a larger version of the Merlin could be designed.

The requirements were that the new engine have good power at low altitude and that it be reliable and easy to service.

Work began on the design of the engine soon afterwards.

The design process was relatively smooth compared with that of the Merlin, and the first of three prototype Griffon Is first ran in the Experimental Department on 30 November 1939.

Although the Griffon was designed for naval aircraft, on 8 November 1939 N E Rowe of the [Vous devez être inscrit et connecté pour voir ce lien] suggested fitting the Griffon in a [Vous devez être inscrit et connecté pour voir ce lien].

Three weeks later permission was given to [Vous devez être inscrit et connecté pour voir ce lien] to explore the possibilities of adapting the Griffon to the Spitfire;
in response Supermarine issued 'Specification 466' on 4 December.

This decision led to a change in the disposition of the engine accessories to reduce the frontal area of the engine as much as possible.

As a result the frontal area of the bare Griffon engine was 7.9 sq ft (0.734 sq m) compared with 7.5 sq ft (0.696 sq m) of the Merlin. This redesigned engine first ran on 26 June 1940 and went into production as the Griffon II.

In early-1940, on the orders of [Vous devez être inscrit et connecté pour voir ce lien], [Vous devez être inscrit et connecté pour voir ce lien], work on the new engine had been halted temporarily to concentrate on the smaller 27 L (1,650 cu in) Merlin which had already surpassed the output achieved with the early Griffon.

Design

Compared with earlier Rolls-Royce designs, the Griffon engine featured several improvements which meant it was physically only slightly larger than the Merlin, in spite of its 36% larger capacity of 37 L (2,240 cu in).

One significant difference was the incorporation of the [Vous devez être inscrit et connecté pour voir ce lien] and [Vous devez être inscrit et connecté pour voir ce lien] drives into the propeller [Vous devez être inscrit et connecté pour voir ce lien] at the front of the engine, rather than using a separate system of gears driven from the back end of the [Vous devez être inscrit et connecté pour voir ce lien]; this allowed the overall length of the engine to be reduced as well as making the drive train more reliable and efficient.

The Griffon was the first Rolls-Royce production aero engine to use a hollow crankshaft as the means of lubricating the main and [Vous devez être inscrit et connecté pour voir ce lien], providing a more even distribution of oil to each bearing.

In another change from convention, one high efficiency [Vous devez être inscrit et connecté pour voir ce lien]-manufactured magneto was mounted on top of the propeller reduction casing; earlier Rolls-Royce designs using twin magnetos mounted at the rear of the engine

The Griffon 61 series introduced a two stage supercharger and other design changes: the pressure oil pumps were now housed internally within the sump and an effort was made to remove as many external pipes as possible.

In addition, the drive for the supercharger was taken from the crankshaft at the back of the engine, via a short torsion shaft, rather than from the front of the engine, using a long drive shaft as used by earlier Griffon variants.

Production of the aero version of the Griffon ended in December 1955, while a marine version, the Sea Griffon, continued to be produced for the RAF's High Speed Launches.

Basic component overview (Griffon 65)

From Jane's and Flight.

Cylinders

Twelve cylinders consisting of high-carbon steel, floating [Vous devez être inscrit et connecté pour voir ce lien]^{[Vous devez être inscrit et connecté pour voir ce lien]} set in two, two-piece cylinder blocks of cast [Vous devez être inscrit et connecté pour voir ce lien] having separate heads and skirts. Cylinder liners [Vous devez être inscrit et connecté pour voir ce lien] plated in the bores for 2 ¹⁄₂ inches from the head.^{[Vous devez être inscrit et connecté pour voir ce lien]}
Cylinder blocks mounted with an included 60-degree angle onto inclined upper faces of a two-piece crankcase.
Cylinder heads fitted with cast-iron inlet valve guides, [Vous devez être inscrit et connecté pour voir ce lien] exhaust valve guides, and renewable "Silchrome" steel-alloy valve seats. Two diametrically opposed [Vous devez être inscrit et connecté pour voir ce lien] protrude into each [Vous devez être inscrit et connecté pour voir ce lien].

Pistons

Machined from "[Vous devez être inscrit et connecté pour voir ce lien]" alloy [Vous devez être inscrit et connecté pour voir ce lien]. Fully floating [Vous devez être inscrit et connecté pour voir ce lien] of hardened nickel-chrome steel. Two [Vous devez être inscrit et connecté pour voir ce lien] and one drilled oil-control [Vous devez être inscrit et connecté pour voir ce lien] above the gudgeon pin, and another drilled oil-control ring below.

Connecting rods

H-section machined nickel-steel forgings, each pair consisting of a plain and a forked [Vous devez être inscrit et connecté pour voir ce lien].
The forked rod carries a nickel-steel bearing block which accommodates steel-backed lead-bronze-alloy bearing shells. The "small-end" of each rod houses a floating phosphor bronze [Vous devez être inscrit et connecté pour voir ce lien].

Crankshaft

One-piece, machined from a [Vous devez être inscrit et connecté pour voir ce lien] nickel-chrome [Vous devez être inscrit et connecté pour voir ce lien] steel forging. [Vous devez être inscrit et connecté pour voir ce lien].
Seven main bearings and six throws. Internal oilway, with feed from both ends, used to distribute lubricants to main and big end bearings.
"Floating" front end bearing consisting of an internally toothed annulus bolted to crankshaft, meshing with and incorporating a semi-floating ring, internally [Vous devez être inscrit et connecté pour voir ce lien] to a short [Vous devez être inscrit et connecté pour voir ce lien] shaft.
Coupling shaft splined at front end to driving wheel of propeller reduction gear.
Clockwise rotation when viewed from rear.

Crankcase

Two aluminium-alloy castings joined together on the horizontal centreline.
The upper portion bears the wheelcase, cylinder blocks and part of the housing for the [Vous devez être inscrit et connecté pour voir ce lien]; and carries the crankshaft main bearings (split mild-steel shells lined with lead–bronze alloy).
The lower half forms an oil sump and carries the main pressure oil pump, supercharger change-speed operating pump and
two scavenge pumps.
It also houses the main coolant pump which is driven through the same gear-train as the oil pumps.

Wheelcase

Aluminium-alloy casting fitted to rear of crankcase.
Carries the supercharger; and houses drives to the supercharger, auxiliary gearbox coupling, engine speed indicator, airscrew constant-speed unit, intercooler pump and fuel pump, as well as the oil and coolant pumps in the lower half crankcase.

Valve gear

Two inlet and two exhaust [Vous devez être inscrit et connecté pour voir ce lien] of "[Vous devez être inscrit et connecté pour voir ce lien]" austenitic nickel-chrome steel per cylinder.
Exhaust valves have [Vous devez être inscrit et connecté pour voir ce lien]-cooled stems. "[Vous devez être inscrit et connecté pour voir ce lien]" (nickel-chromium) protective coating to the whole of the combustion face and seat of the exhaust valves, and to the seat only of the inlet valves.
Each valve is held closed by a pair of concentric [Vous devez être inscrit et connecté pour voir ce lien].
A single, seven-bearing camshaft, located centrally on the top of each cylinder head operates 24 individual steel [Vous devez être inscrit et connecté pour voir ce lien]; 12 pivoting from a rocker shaft on the inner, intake side of the block to actuate the exhaust valves, the others pivoting from a shaft on the exhaust side of the block to actuate the inlet valves.

Engine capacity, mass flow and supercharging


Although it is common practice to compare different piston engines and their performance potential by referring to the [Vous devez être inscrit et connecté pour voir ce lien] this does not give an accurate reading of an engine's capabilities.

According to [Vous devez être inscrit et connecté pour voir ce lien], who was in charge of the Merlin's development,

"The impression still prevails that the static capacity known as the swept volume is the basis of comparison of the possible power output for different types of engine, but this is not the case because the output of the engine depends solely on the mass of air it can be made to consume efficiently, and in this respect the supercharger plays the most
important role."

Unlike the Merlin, the Griffon was designed from the outset to use a single-stage supercharger driven by a two-speed, hydraulically operated gearbox; the production versions, the Griffon II, III, IV and VI series, were designed to give their maximum power at low altitudes and were mainly used by the Fleet Air Arm.

The Griffon 60, 70 and 80 series featured two-stage supercharging and achieved their maximum power at low to medium altitudes.

The Griffon 101, 121 and 130 series engines, collectively designated Griffon 3 SML, used a two-stage, three-speed supercharger, adding a set of "Low Supercharger (L.S)" gears to the already existing Medium and Full Supercharger (M.S and F.S) gears.

Another modification was to increase the diameters of both impellers, thus increasing the rated altitudes at which maximum power could be generated in each gear.

While the 101 continued to drive a five-blade propeller, the 121 and 130 series were designed to drive contra-rotating propellers.

In 1946 a Griffon 101 was fitted to the [Vous devez être inscrit et connecté pour voir ce lien] XVI, RB518 (a re-engined production Mk.XIV); this aircraft achieved a maximum speed of 494 mph (795 km/h) with full military equipment.

Pilot Transition


Pilots who converted from the Merlin to the Griffon-engined Spitfires, soon discovered that, because the Griffon engine's propeller rotated in the opposite direction to that of the Merlin, the fighter swung to the right on take-off rather than to the left.

This tendency was even more marked with the more powerful 60 and 80 series Griffon engines, with their five-bladed propellers.

As a result, pilots had to learn to apply left (port) trim on take-off, instead of the right (starboard) trim they were used to applying.

On take-off, the throttle had to be opened slowly, as the pronounced swing to the right could lead to "crabbing" and severe tyre wear.

Some test Spitfire XIVs, 21s and 24s were fitted with [Vous devez être inscrit et connecté pour voir ce lien], which eliminated the torque effect.

Early problems with the complex gearbox, required for contra-rotating propellers, prevented them from ever becoming operational in Spitfires, but they were used on later aircraft, including the [Vous devez être inscrit et connecté pour voir ce lien] FR. Mk 46 and F and FR.47, which were fitted with Griffon 87s driving contra-rotating propellers as standard equipment.

The Griffon 57 and 57A series, driving contra-rotating propellers, was used in the [Vous devez être inscrit et connecté pour voir ce lien] maritime patrol aircraft.

Variants


The Griffon was produced in approximately 50 different variants, the Griffon 130 being the last in the series.

Details of representative variants are listed below:

• Griffon IIB
  

1,730 hp (1,290 kW) at 750 ft (230 m) and 1,490 hp (1,110 kW) at 14,000 ft (4,270 m); Single-stage two-speed supercharger; impeller diameter 10 in (25.4 cm); gear ratios 7.85:1, 10.68:1. Used on [Vous devez être inscrit et connecté pour voir ce lien] and [Vous devez être inscrit et connecté pour voir ce lien].

• Griffon VI
  

Increased maximum boost pressure, 1,850 hp (1,380 kW) at 2,000 ft (610 m); impeller diameter 9.75 in (24.7 cm). Used on [Vous devez être inscrit et connecté pour voir ce lien] Mk.XV and Mk. XVII, Spitfire XII.

• Griffon 57 and 57A
  

1,960 hp (1,460 kW); 2,345 hp (1,749 kW) with water-methanol injection on take-off: used on [Vous devez être inscrit et connecté pour voir ce lien].^{[Vous devez être inscrit et connecté pour voir ce lien]}

• Griffon 61
  

Introduced a two-speed two-stage [Vous devez être inscrit et connecté pour voir ce lien] with aftercooler similar to that on Merlin 61; 2,035 hp (1,520 kW) at
7,000 ft (2,100 m) and 1,820 hp (1,360 kW) at 21,000 ft (6,400 m); used on [Vous devez être inscrit et connecté pour voir ce lien].

• Griffon 65
  

Similar to Griffon 61 with different propeller reduction gear; Impeller diameters 1st stage: 13.4 in (34 cm), 2nd stage: 11.3 in (29 cm); used on Spitfire F.Mk.XIV.

• Griffon 72
  

Increased maximum boost pressure to take advantage of 150-[Vous devez être inscrit et connecté pour voir ce lien] fuel; 2,245 hp (1,675 kW) at 9,250 ft (2,820 m).

• Griffon 74
  

Fuel-injected version of Griffon 72; used on Firefly Mk.IV.

• Griffon 83
  

Modified to drive [Vous devez être inscrit et connecté pour voir ce lien]; 2,340 hp (1,745 kW) at 750 ft (230 m) and 2,100 hp (1,565 kW) at 12,250 ft (3,740 m).

• Griffon 85
  

2,375 hp (1,770 kW); used on [Vous devez être inscrit et connecté pour voir ce lien].

• Griffon 89
  

2,350 hp (1,755 kW); used on Spiteful Mk.XV.

• Griffon 101
  

2,420 hp (1,805 kW); Two-stage, three-speed supercharger using Low Supercharger (L.S), Moderate Supercharger (M.S), or Full Supercharger (F.S); reduction gear ratio 4.45; Rolls-Royce fuel injection system. Used on Spiteful Mk.XVI.

• Griffon 130
  

2,420 hp (1,805 kW) at 5,000 ft (1,524 m) in L.S gear, 2,250 hp (1,678 kW) at 14,500 ft (4,419 m) M.S and 2,050 hp (1,529 kW) at 21,000 ft (6,400 m) F.S; reduction gear ratio 4.44; modified to drive contra-rotating propellers; Rolls-Royce fuel injection system.