Merlin/Griffon question

Sorry for delay, the VATman took precedence!

Mike
The only pictures I’ve got of bare “R” engines quite clearly show spur reduction gears.
With a prop of the size used on the S6 and S6B I don’t believe direct drive could have been used.

VERY abbreviated summary of RR piston engines.

I think the RRHT may have been a bit wrong with their explanation regarding epicyclic and spur reduction. In one of their own publications, the Condor 1A has epicyclic but from the Condor III on they had spur reduction. This was in 1923 which is well pre-Kestrel. The Condor was developed from the Eagle which were all epicyclic.
The reason for changing to a spur reduction was to bring the propellor shaft to the centre of the engine.
The next stage was the “F” engine which later became the Kestrel. This was influenced by the Curtiss D12 with it’s aluminium block and steel liners. Prior to this, all RR aero engines had separate steel cylinders with welded-on jackets. The original “F” engine didn’t have a reduction gear but one was added early on. This infers that all Kestrels had a reduction gear.
The Goshawk and Peregrine were developments of the Kestrel. The Goshawk with evaporative cooling and the Peregrine specifically designed for the Westland Whirlwind with a downdraught carburettor and air intake between the cylinder banks to reduce drag, and handed. The handing doesn’t appear to be as simple as it first seems. Many internal drives incorporated a “spring drive” apparently for reasons of backlash. It would seem that these had to be handed as well.
The “H” which became the Buzzard was a scaled up Kestrel and development proceeded at the same time. As is well-known, the “R” was a development of the Buzzard.

The Merlin appears to be a “clean sheet of paper” design, based on Kestrel and Buzzard experience, rather than another variation in size.
The original design called for the cylinders and crankcase to be cast in one piece, like a car engine. When anything broke it caused so much damage they abandoned the idea.
The original head design (ramp head) was also unsuccessful and as a stopgap, a scaled up Kestrel type one-piece head and block was used. Later versions, from the 60 series onwards, used a separate head and block.

A derated version of the “R” known as the Griffon first ran in 1933. When RR realised a more powerful engine was needed, they completely redesigned the Griffon, using the “R” bore and stroke. The intention was to make it as small as possible. Comparing pictures of the original Griffon and the redesigned production version they succeeded brilliantly. The camshaft drives were moved to the front of the engine, and on the early ones, the first part of the supercharger drive.

There’s no mention of when they decided to make it run backwards. 🙂

Hi dhfan,
That could be interesting!
Cheers………………

WarbirdUK
I’ve got a RRHT book by A.A.Rubbra about Merlin and Griffon design and prinicples. Haven’t got time to do anything now but I’ll look later and paraphrase a few bits.

Yes Mike,
The Merlin has a reduction gear just behind the prop so the crank has a small straight cut gear running with a larger straight cut gear on the prop driver shaft so the prop will turn in the opposite rotation from the crankshaft, There is also an oil way that goes to the prop driver shaft for pitch control of the blades! So there is a lot going on in that area! Hope this helps.

The Griffon also has a reduction gear but I’m not up to speed on Griffons.

Janie,
I think the Merlin was the progression from the Kestrel as the early Merlin’s were a mono block as were the Kestrel If my memory serves, the Griffon is a much larger engine than the Merlin & to my eye looks to be round the wrong way compared with the Merlin as I seem to remember the cam drives are at the front of the engine while the Merlin has them at the rear, maybe this is why the Griffon rotates the other way, I don’t know I’ve not worked on any Griffons, only Merlin’s.

Cheers. 🙂

Originally posted by Janie
Thanks so far. However, I understand that the majority of propellers manufactured for the Merlin and Griffon were designed and made by the British company Rotol. I also believe that it was the Merlin which rotated anti-clockwise, like American engines, whilst the Griffon was “English-style”.

One theory is that the development of the Griffon actually started before the Merlin as it was developed from the earlier “R-Type” racing engines. Perhaps, when the Merlin was produced Rolls-Royce decided to adopt commonality with U.S. design practice.

I guess I am really looking for someone to confirm or correct the fragments of information that I have.

Take a look at the S6B and, as it was an ungeared engine you will see that (if you look at it from the front) it rotates anti -clockwise though how that relates to the geared engines like the merlin and griffon direction of rotation I don’t know. Did their gearing make the props rotate the opposite way to the engine?

Cheers mate! 😀

Hi Janie,

I can send you a copy of that picture – please e-mail me off board.

I’m sure I’ve got it in a book myself somewhere but Google came up with this:
http://www.unrealaircraft.com/hybrid/spitfire.php

There may be others but that looks like the pic I’ve seen before.

Just noticed the serial number.
Comments, Ian?

Just finished reading the whole page. Comments unnecessary!

Originally posted by dhfan
There’s a picture around of a Spitfire the Germans re-engined with a D-B of some sort. Looks decidedly odd.

It would be great to get a copy of this picture. Can anyone help?

Thanks Janie, RR certainly don’t waste any time being helpful and I now understand the technicalities a little better thanks to their reply

Following on from the RRHT answer, presumably if RR had reverted to an epicyclic reduction for the Merlin, by lowering the prop-shaft centre, it would have given a better view over the nose. Make a Spifire look funny though. There’s a picture around of a Spitfire the Germans re-engined with a D-B of some sort. Looks decidedly odd.

Janie,
thanks for sharing!

This probably …… :rolleyes: …… put an end to speculating!

Christer

If you are still talking about flying – yes, that method works for me. Screaming helps too, I find.

Originally posted by Janie
So long as its into wind and straight, I don’t think going backwards would make me any more confused than I already am on take off. 😀

So you do the same as me then……………………close your eyes and hold on until the ground stops thumping on the wheels.

So long as its into wind and straight, I don’t think going backwards would make me any more confused than I already am on take off. 😀

… and then there are pusher engines of course, but we might have to move to another forum if we mention Cessna or Rutan …

That would make someone think when they fire it up for the first time and the torque takes them off the runway in the opposite direction………………………..backwards 😀 😀

It shouldn’t be too difficult to get the engine turning the other way, a change of cams, reverse the direction of the starter motor will get you most of the way there, mag timing & pumps will complete the change! Sorted!! 😀

Thank you all for your wonderful response.
Rolls Royce Heritage Trust took a mere week to reply. Fantastic. This is copied exactly:

[I][COLOR=darkblue]In the late 1930s the Society of British Aircraft Constructors formed a committee (among others) to standardise aero-engine powerplants. One of the Committee’s aims was to allow engines of a similar power to be installed on the same bulkhead. So, for instance, if a Hercules-engined aircraft needed an engine change and a spare was not available, then a Griffon could be substituted. The Griffon ready-to-be-bolted-on powerplant would be self-contained with radiators, etc, installed, the mounting pick-up points were the same as were the fuel supply and control lines connections and cowling diameters. Unfortunately this did not work for the Merlin because the propeller from the dead engine was not suitable. So, from the Griffon onward all new Rolls-Royce piston aero engines (Crecy, Eagle and Pennine) rotated the opposite way to the Merlin, and the same way as everyone else’s engines. This strategy was stifled by the outbreak of World War Two, and post-war the idea was dropped, even though Rolls-Royce produced many Universal Power Plants for the Lincoln and Shackleton. To anticipate the next question – why did the Merlin rotate opposite to other engines: The early Rolls-Royce engines had epicyclic propeller reduction gears, so the propellers rotated the same way as the crankshaft. The original Kestrel had a direct drive but when they fitted a reduction gear they chose a spur-type making the prop rotate opposite to the crank. This design feature was incorporated into the Merlin. Hooray for gas turbines! David Birch

[/I][/COLOR]
So most of you got a fair bit of it right, but now the jigsaw is complete. I did like dhfan’s answer at 02:24 in the morning on 12Sept which reads absolutely correct, so long as you hold it in front of a mirror! 🙂 Bless you!

Well, You can´t know them all but now I know of one more …… 🙂 …… thanks for introducing him!

Christer

Captain Eric ‘Winkle’ Brown CBE.DSC.AFC.RN has made 2407 carrier deck landings, 2,721 catapult launches and flown 487 different types of aircraft. These are all world records.
He served in the Fleet Air Arm in WW2 and was on board HMS Audacity when it was sunk.
He was based at Farnborough as a test pilot for 6 years from 1942 and has a list of decorations as long as your arm, and longer than his. I think his words are ‘diminutive stature’.
He was the first person to land a twin-engined aircraft (Mosquito) and the first to land a jet (Vampire) on an aircraft carrier.

For a potted history

http://www.setp.org/EBrown.htm

US carriers have the bridge on the right too.