Talk:Rolls-Royce Griffon/Archive 1

Archive 1

V twin?

Um, I'm a little appalled that the description of the Griffon as a V-twin engine survived so long. Am I missing something? Andrewa 18:19, 25 Jun 2005 (UTC)

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BetacommandBot (talk) 05:42, 24 January 2008 (UTC)

Griffon Beaufighter

I could understand the good faith removal of the Beaufighter as an application but the engine was used in this aircraft, albeit in limited numbers, have added a cite now and this image shows what the beast looked like. Cheers Nimbus (Cumulus nimbus floats by) 09:43, 5 February 2009 (UTC)

I must admit I'd never seen a Griffon-engined Beaufighter before. It appears to have one of the early 'arrowhead' AI radar installations. (Fluctuations at a minimum) —Preceding unsigned comment added by 213.40.127.214 (talk) 21:43, 22 March 2009 (UTC)

RR-37

Yep, I was wondering about that myself; however that is how it was was designated by Morgan and Shacklady (mind you, they also asserted the engine was a direct derivative of the R). I am trying to clarify the timeline because design of the mass-produced Griffon was not started in 1933; so far my limited sources have shed little light on the matter. Minorhistorian (talk) 23:34, 5 January 2010 (UTC)

Well it's not a number that appears in other references, it's in the form that they used for alloys like "RR.50". Don't think it's a serial number either. There was a Griffon 37 variant much later, will look at Rubbra's book again. Nimbus (Cumulus nimbus floats by) 23:45, 5 January 2010 (UTC)

Does relate to the metric capacity though? Nimbus (Cumulus nimbus floats by)

Without further confirmation 'tis better to leave well alone and rely on verifiable details. Minorhistorian (talk) 09:58, 6 January 2010 (UTC)

Footnote 1

This note is confusing and not quite correct. The very first Griffon (Griffon serial No. 1) was a modified Buzzard and ran between 1933 and 1934, this engine was known just as the Griffon. The all-new Griffon I first ran in 30 November 1939 with the redesigned Griffon II running on 26 June 1940.

Extra info: There were three Griffon Is built according to Pugh (Magic of a name, p. 242) I think the article mentions just one at the moment. The Griffon II was 200 lb lighter than the I, The Griffon IIB first ran in December 1940, this engine had a revised firing order (which was kept for the series) to offset crankshaft vibration. Nimbus (Cumulus nimbus floats by) 01:50, 8 January 2010 (UTC)

All good stuff; the account in Morgan and Shacklady especially is a little confusing...must see If I can get a hold of the likes of Lumsden; my resources on engines are limited.

BTW Re; The reference to propeller "torque" in the "Pilot conversion" section; I have thought for a long time that the propeller's slipstream helped create take-off swing as much as engine torque, let alone so-called propeller "torque"; surely the airflow down the side of a fuselage must have been a more important element in creating swing, particularly as propellers got larger and produced a far greater disc area. Two things to consider: Since when has using a rudder been able to compensate for engine torque? The rudder has an aerodynamic function, not a mechanical one; on an aircraft, if engine torque was so critical, one means of compensating would be to use a stronger undercarriage leg and higher oleo pressure on the affected side. Minorhistorian (talk) 21:17, 8 January 2010 (UTC)

Have a read of P-factor and precession, there is a third effect of the landing gear on one side creating more drag through friction as it is forced harder into the ground (torque effect), it all adds up in the same direction of yaw. Precession takes hold in a taildragger when the attitude changes from tail down to tail up (the propeller being the gyro) and is probably the major cause of yaw on take-off. Most taildragger rudders are not very effective until the tail is up, it can catch the best pilots out at times and is the reason for specific taildragger 'differences' training for nose gear trained pilots in the UK at least. The lowly Tiger Moth will yaw quite badly if left unchecked. Got refs on this but they are probably not relevant to this article, just need to wikilink to the correct articles. I have pilots notes for the Seafire 47 that might have more on this, not sure where they are though. Nimbus (Cumulus nimbus floats by) 21:48, 8 January 2010 (UTC)

Rudder will check the swing if it is applied (sometimes fully) before it develops, if it doesn't then the design of the aircraft is wrong or the aircraft is being flown out of crosswind limits or you've got a flat tyre/binding brake. Crosswinds can both help and hinder depending on which side they are coming from. Nimbus (Cumulus nimbus floats by) 21:54, 8 January 2010 (UTC)

I am a bit concerned that the word 'torque' has been replaced with 'slipstream', Gunston, Lumsden and Price use this term, their cites are now supporting something that they are not stating. Also remember that the rudder is operating in the slipstream and can be used to turn a stationary taildragger with one brake held on and the tail off the ground (only for the brave!). This tight turn [1] is done by blipping the throttle and holding full right rudder and 'down' elevator to lighten the tail. The Tiger has no differential brakes (no brakes at all actually) or steering other than the tailskid. Nimbus (Cumulus nimbus floats by) 22:27, 8 January 2010 (UTC)

Changed it back to read torque, although I still think this is a complete misnomer. I remember reading an Air International article which discussed the misuse of "torque effect" when related to the purely aerodynamic effects of slipstream - wish I could find it... Interestingly Spitfires up until the Mk XIs used the same pressure in both oleos; in Griffon-engined Spitfires from the Mk XII on higher pressures were used in the starboard oleo (Mk XII 420 psi Stbd, 380 psi port). Minorhistorian (talk) 04:50, 9 January 2010 (UTC)

Engine torque tends to try and rotate the aeroplane around the longitudinal axis, i.e., to rotate the fuselage in the opposite direction to the propeller rotation This will result in the effective load on the oleo leg on that side being increased in relation to the opposites side, creating greater friction on that side and thus a tendency to deviate from a straight line whilst on the ground. The slipstream from the propeller rotates in the same direction which increase the aerodynamic force on one side of the fuselage and fin/rudder, which creates a corresponding aerodynamic force on that side of the aeroplane, leading to a tendency to veer in that (same) direction. This is kept in check on take-off by a bootfull of opposite rudder, the amount depending on ground speed. This slipstream effect is one of the original reasons for having trimmable control surfaces, as the effect varies with airspeed. The Hurricane had an offset fin for just this purpose, although it would only have been effective at one particular airspeed, cruising, IIRC. Precession is usually only relevant when the tail is being raised during the acceleration of the take-off run, the rotating propeller mass acting as a gyroscope. All these effects combined are the cause of what used to be termed in tailwheel-undercarriaged aircraft, a 'swing' on take-off. —Preceding unsigned comment added by 86.112.65.146 (talk) 22:23, 17 March 2010 (UTC)

Pilot transition

It is difficult to know why this section belongs here in the first place; this should be in Supermarine Spitfire (Griffon powered variants). As it is not all Griffon engined Spitfires were as bad as recent additions have made out; according to the Pilot's Notes for the Spitfire XIV & XIX the stability about all axes was satisfactory, except for aircraft with the cut-down rear fuselages, which needed careful use of the rudder and rudder trimming tab at high altitudes. Aircraft with extra fuel tanks in the rear fuselage also had reduced longitudinal stability until the tank was emptied. The Spitfire 21 through to 24 series were, again, not as bad as recent additions have implied. Minorhistorian (talk) 08:54, 1 February 2010 (UTC)

The directional stability problems with some Spitfires only really applied to the re-engined ones, where the longer nose, increased horsepower, and greater propeller disc solidity (due to the increase in the number of blades, first four in the Mk IX, and then five in the Mk XIV) had finally proven too much for the standard (initial Mk I) fin and rudder areas. This, along with the cut-down rear fuselage for the bubble canopy, was the reason for the changing fin/rudder shapes, the area being increased for the reasons mentioned above. The instability was only significant in the initial (i.e., prototype) conversions, as these aircraft had the original size and shape fin/rudders of the earlier Marks, the larger tails being designed for production aircraft, e.g., Mk XIV. The later aircraft (especially the ones with the 'Spiteful tail', i.e., MK 22-24) had no real problem with directional instability. Quill's only complaint about the Mk 24 was that it was 'a little overpowered perhaps', but was a 'magnificent aeroplane'. —Preceding unsigned comment added by 86.112.65.146 (talk) 21:59, 17 March 2010 (UTC)

Dead external link

Have removed this link [2] as it is coming up as 'connection refused', parking it here in case it comes back. Nimbus (Cumulus nimbus floats by) 18:51, 7 April 2010 (UTC)

Moving up?

Just had a tidy up and ran the article through some auto reviewer tools, don't see why we can't move it up the assessment ladder. The images would need alt text adding and the supercharger section is a little 'cluttered', could be split into 'family group' sub-headers like the Merlin. Some paragraphs and important facts are not cited, cheers. Nimbus (Cumulus nimbus floats by) 19:43, 7 April 2010 (UTC)

Direction of rotation

Speaking from a theoretical perspective (specifically without personal experience or access to the references), I'm a bit puzzled. Most simply, there appears to be a contradiction in the article; the 'crankshaft' section states that the engine rotates clockwise, while footnote 4 states that the propeller rotates counter-clockwise. This could simply be because the reduction gear reversed the direction of rotation (though this would have caused the torque on the gear box to be the sum rather than the difference of the input & output torque, which wouldn't be particularly helpful). However, if this is the case, &/or the footnote is correct, I'd be rather puzzled as to the veracity/cause of the 'pilot transition' section. Assuming that the effects described is due to P-factor, a counter clockwise propeller would cause a yaw to the right at take off. I can't think of any reason for this effect to be reversed, so either there is a mistake somewhere, or I'm missing something (?) 80.229.172.13 (talk) 22:00, 14 February 2012 (UTC)

From the article: "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." Simple, really: pilots who had flown Merlin powered Spitfires, which, without proper trimming, swung to the left on take-off - the more powerful Griffon, and the four or five bladed propeller, induced a swing to the right, which could sometimes catch out pilots who continued to use a starboard oriented trim; this could naturally accentuate the swing, rather than compensate for it.◆Min✪rhist✪rian◆MTalk 00:06, 15 February 2012 (UTC)

it is actually propeller rotation that affects the swing, the propeller being of a relatively large mass compared to the rotating engine components. The reduction gear does indeed usually reverse the direction of propeller rotation over that of the crankshaft.

So, looking at the propeller from the cockpit, if the upper half of the propeller, i.e., the upper part of the propeller disc seen over the nose of the aircraft, turns from left to right (clockwise), the swing will be to the left. Conversely, if the propeller turns to the left, (anti-clockwise) the swing will be to the right. — Preceding unsigned comment added by 2.29.18.153 (talk) 13:10, 19 August 2015 (UTC)

Firing order, direction of rotation, and sound

Some info about firing order, direction of rotation and sound for consideration:

Merlin firing order: 1A, 6B, 4A, 3B, 2A, 5B, 6A, 1B, 3A, 4B, 5A, 2B ('A' being the right bank as viewed from the rear of the engine)

Griffon firing order: 1A, 4B, 3A, 2B, 5A, 1B, 6A, 3B, 4A, 5B, 2A, 6B (changed from the Merlin to reduce stress on the crankshaft)

The Griffon anti clock rotation (as viewed from the rear of the engine) was mandated by the Society of British Constructors to be in line with other UK engines (but not the Merlin). That caused the later Griffon engined Spitfires, for example, to pull to the opposite side, especially on take off. Note that most US engines rotated clockwise.

Although both engines are V12s they sound quite different: the Merlin has a smooth purr while the Griffon has a rough growl. This is mainly due to the different firing order and the different cam characteristics. .

CPES (talk) 19:11, 30 April 2015 (UTC)