RR Merlin

A Merlin was flown in a Hart on 21/02/35. Where that fits with the Horsley I don’t know.
Horsleys seem to have been particularly good as engine testbeds. They were used for various Condors, including a diesel, Eagle VIII, R-R H10 (whatever that was), Buzzards, Merlins, Napier Lions and various Armstrong-Siddeley Leopards. Versatile by any standards.
Info from Hawker Aircraft since 1920.

Forgot the Junkers Jumo.

it’s the people who ruin it

I count myself as one of them!

Originally posted by Buddy Boy
Something good had to come out of Paisley!

Don’t be like theat. Nice place Paisley, it’s the people who ruin it 😀

Something good had to come out of Paisley!

FWIW A nice old chap I spoke to a few years ago said that he’d worked on Merlins all through the war and he reckoned that you could tell which factory they came from by their qualty of finish. His remark was that the best ones came from Paisley with Derby and Packard swapping places for 2nd and 3rd over the years.

Going back to the original question, “Test Pilots” by Don Middleton says on page 148 that the first Merlins were installed in Hawker Horsleys. 100 hours were flown in 6.5 days, by test pilots Shepherd, Heyworth and Harker, according to this book, to test the engine thoroughly before the Hurricane prototype installation; the engine showed a high level of reliability. However I have not found any other reference to Horsley Merlin test beds in my other reference books.
The same page also refers to the He 70 Kestrel installation, but sheds no light on the alleged use of this engine in other aircraft in Germany before the He 70 was delivered to Rolls-Royce.

Cold it just be a cold day when they measured it?

Alec Lumsden’s book is highly recommended.

MH

Archer,

There is precious little air gap between the induction system and the firewall on all models of Spitfire. The Griffon two stage engines, the heaviest and the longest (in my view), required the provision for lead weight in the fin to maintain the C of G within manageable limits under operational conditions.

Mark

Originally posted by JDK
Hi Archer,
Great story about the ‘overused’ Kestrel. But.. It smells to me like a great ‘bar-room’ fact, rather than something likely. Any evidence?

Indeed it does sound that way a bit. But over the years I’ve seen it in a number of different books and publications, and although I cannot name one off the top of my head I reckon there is a grain of thruth in it. The facts are that RR did have a He-70 with a Kestrel in it so there’s a fair chance of it being correct. I was hoping someone else on this forum might have a clue as to the origins of the story?

With regards to the Griffon/Merlin length comparison, remember that the difference in length is not just because of the difference in engine size. The Griffon was heavier as well so the influence on CG was also a factor in the Spitfire’s redesign, and may have influenced the engine’s placement.

Originally posted by dhfan
A good bit of that is fairly obviously taken up in the cam bulges on the Spitfire.

The ‘cam bulges’ on the Griffon are obvious because that is the way the designers of the top cowling have streamlined it. I suspect the Merlin is equally broad in that area but has more voluminous cowls.

A little competition anybody?

How much narrower is the Merlin over the Griffon top cowling in the front cam area to nearest .25 inch?

I will get them measured.

Mark

It really was an amazing bit of design work. I had no idea of length comparisons but, IIRC the Griffon has something like 1 sq ft or a little over, greater frontal area than the Merlin for well over 30% greater capacity. A good bit of that is fairly obviously taken up in the cam bulges on the Spitfire.

Griffon dimensions

TN,

I guess it depends where you are measuring but I just had a quick pod through the Griffon 61 65-67 74 manual. They do not quote dimensions, however there is a large pullout longitudinal section view. By ratio on a 6 inch bore the overall length scales pro rata to just over 90 inches. This would suggest the Alec Lumsden dimension is for the Griffon VI or 6. That is 8 inches less and that sounds about right for the second stage of the blower.

The clever bit on the Griffon was to draw all the ancilliaries to the rear and drive them through a seperate gearbox, thus maintaining the same basic frontal area as the Merlin when fitted to the Spitfire. There was no change to the Spitfire firewall cross section dimensions from Mk I to Seafire 47.

Mark

Good question. I am not in the privileged (more like green with envy) position of being as knowledgeable about the spitfire as you so I can only quote others or offer an opinion as an engine engineer.

The Griffon was wider so I imagine that length was needed to ensure good streamlining.

Griffon IV is about 72 inches, with a Merlin 20 at 71inches and the 45 at 69inches

TempestNut.

Then why is the Spitfire XIV so much longer than the Mk VIII?

Not 24 odd inches in the Spinner and tail unit!

Mark

PS What length does Alec Lumsden give for the single stage Griffons such as the VI?

Mark12 as hard as it is to imagine that a Griffon could be shorter, in fact it is. The Merlin 2 stage engine is 88.7 inches long, and a Griffon 2 stage engine is 82 inches long. The Merlin 2 stage engine broke new ground, but in the Griffon the cam and magneto drives had been moved to the front of the engine allowing the designers to package the Griffon supercharger very cleverly and make the engine shorter.

The figures come from Alec Lumsden’s book British Piston Aero-engines and apply to most 2 stage engine models.

TempestNut

Quote:
‘In fact the 36 litre Griffon 60 is shorter than a 60 series Merlin.’

Surely not 🙁

Griffon VI – maybe.

Griffon 60 series – two stage supercharger.

Mark

Hi Archer,
Great story about the ‘overused’ Kestrel. But.. It smells to me like a great ‘bar-room’ fact, rather than something likely. Any evidence?

Cheers

Originally posted by TempestNut

The different sound from the Griffon is not so much that it revolves in the opposite direction, but that its maximum revs are less that the Merlin and the Valve overlap is far less aggressive, giving a different sound from the exhaust. The firing order is the same but just in reverse.

Ah yes that was it…I was nearly right !!!!
😀

The Griffon owes more to the Merlin than to the Buzzard and R. Although development work started from the base of the Buzzard in the early 30’s, the entire engine was redesigned to incorporate experience with the Merlin. In fact the 36 litre Griffon 60 is shorter than a 60 series Merlin. This was one of the design objectives. These objectives would never have been met with the Buzzard or R. The only thing in common with the Buzzard, R and Griffon was a 6 inch bore and a 6.5 inch stroke. The Merlin was 5.4 inches by 6 inches for 27 litres.

The different sound from the Griffon is not so much that it revolves in the opposite direction, but that its maximum revs are less that the Merlin and the Valve overlap is far less aggressive, giving a different sound from the exhaust. The firing order is the same but just in reverse.

If we had a Hornet flying we could listen to the handed engines, and although they revolve in opposite directions they would still sound the same. One of them would not sound like a Griffon. Must be some one out there who can remember the Hornet flying

The first mention of the Merlin in my personal database of first flights is Hawker Hart K3036 on February 21, 1935, powered by a P.V.12 which was to all intents and purposes the forerunner of the Merlin. The next entry that relates to an actual Merlin is the Haweker Hurricane prototype K5083 on November 6, 1935 as so many have already stated. This was a 990 hp version Merlin “C” no. 11, so numbers 1 to 10 were very probably ground test engines. That would make the Hurricane definitely the first true Merlin-powered aircraft.