Really powerful engine, early on, for RAF/FAA?

[tomo pauk]

Reading a bit on the Rolls-Royce engines, an interesting tidbit surfaces: in the late 1930s, RR was developing two engines specifically for the FAA: Exe and Griffon.
Exe was a new design, Griffon shared many things with Buzzard. In the same time, RR was working on the Vulture, the big and powerful engine. Eventually, Exe and Vulture were cancelled, Griffon went to serve in second half on the ww2 (being loosely based upon earlier engine, it was probably a less risky and demanding thing?).
So - how good or bad would be if the RR went, in second half of 1930s, to design one powerful engine, based on their existing engines, to serve the both RAF and FAA? Easiest way - develop the Buzzard more (pre-Griffon)? Make a 24-cyl engine, based on Merlin, maybe in W or H layout? Or, make a 24-cyl engine based on Kestrel/Peregrine, but in W or H layout? The 3-bank Merlin was proposed in another thread, we can skip it here
Or, forget the existing engines, and make something similar to Exe, but with bigger cylinders, so it ends up at ~35 L instead of 22L?
Aim should be at 1500-1800 HP, on 87 oct fuel, for service in 1940.

 

[yulzari]

For Rolls Royce it would have to be something instead of the Vulture. They had to drop the Exe and the Peregrine to allow resources for the Vulture and Merlin. The Griffon was an FAA back burner until the Vulture's resources were released so an early Griffon is really the only Rolls Royce option in time.

I would offer my perennial, the Double Pegasus from Bristol and tell them to stop playing with sleeve valves but I am sure others will look to the Fairey double engines.

A Double Pegasus Fulmar with 1,800 bhp and cannon will do most of the FAA tasks backed up by Swordfish as an all weather ASW escort carrier weapon. Now if you can get a torpedo under a Double Pegasus Fulmar and off a Fleet Carrier's deck then we forget the Firebrand (as we all should). Part of the trick is to persuade the Sea Lords that underwing weapon loads are a good idea. It can use Firefly design resources.

By the time the FAA is looking for a Double Pegasus replacement they have abandoned the torpedo as an anti ship weapon and should be looking to a jet generation for Fleet Carriers and helicopters for escort carriers. It was a tricky time when one wanted to increase naval aeroplane weights but the steam catapult had not yet changed the game so any Double Pegasus replacement has to be able to haul itself and it's warload off the deck by it's own efforts.

 

[tomo pauk]

I have no problems with proposals other than what RR might've developed.

 

[Shortround6]

"Aim should be at 1500-1800 HP, on 87 oct fuel, for service in 1940."

Probably not going to happen. Lets look at it shall we?

Merlin is 27 liters at 3000rpm (1500 power strokes per minute) times 1.4 ATA ( roughly, very roughly) for 1030hp. or 56700 liters of air per minute for 1030 hp or 55 liters of air per minute per hp. For 1500hp we need 82500 liters of air per minute ( 3 bank Merlin at 3000rpm). Griffon/Buzzard needs about 3280rpm at 6lbs boost. Vulture will do it at 2770rpm. The Exe needs 5360rpm. Even using cylinders the size of a DB 603 requires 2650rpm with a piston speed of 3129fpm.

Best, lowest risk, but lowest power is the Buzzard/Griffon.

With an upper limit on cylinder size ( from cooling, fuel burn and piston speed) and a limit on BMEP due to fuel all you can do is add cylinders.

Obviously I am ignoring things like compression ratios, internal friction and actual volumetric efficiency and just looking at possible airflow at 6lbs boost. With 87 octane fuel there is a limit to the effective BMEP you can have unless you really play games with cylinder size (smaller can be be bit higher) and that is one reason for the small cylinder 24 cylinder engines. The small cylinders also allow for more rpm at the same piston speed which helps.

The Exe was probably a no-go, while the prototype engine ran well for a number of years so did some Bristol and Napier prototype sleeve valve engines, it was making them on a production basis that caused trouble. Expecting R-R to solve that problem quicker than Bristol (who had been working on sleeve valves for years) is a very large leap of faith.

 

[tomo pauk]

I'm not sure my message got through - I was proposing 24-cyl engines (among other stuff), that would be based on existing Merlin/Kestrel/Peregrine. Agreed that a development of the Buzzard would be a low risk-low gain approach. As for the Exe-like, I was proposing the air-cooled 24-cyl of much greater displacement.

 

[Shortround6]

TO what purpose?

An Arsenal 24 H ( double Jumo 213) offered 4000hp for 4080lbs in 1947 on 100/130 fuel.

pre war Hispano offered the 24Y a 24 cylinder H engine using normal Hispano engine blocks. 2200hp for 2160lbs and 51in high and 36in wide.

Basically they are too big to fit in existing single engine aircraft. You wind up with either big twins like the Manchester or Warwick, which turned out to be NOT such a good idea or some really strange single engine aircraft, sticking a 24 cylinder H Kestrel on a Fulmar does NOT get you a Firefly several years early.

 

[tomo pauk]

On the contrary, Fulmar should be the 1st recipient of a big engine. There was a difference between fleet defenders that were able to catch Ju-88s, vs. the ones unable doing that. 2nd recipient might be one of the Hawker's heavy fighters. Then the Barracuda, then Firefly. Maybe install it on the Beaufighter, it was tested with Griffons historically.
Thanks for mentioning the 24Y - would you please provide some link about that, quick googling reveals only the post-war 24Z? The 24Y looks like a gem, comparing how hard it was for many of the countries to come up with 2000-2500 HP engines until late in war?

 

[wuzak]

For Rolls Royce it would have to be something instead of the Vulture. They had to drop the Exe and the Peregrine to allow resources for the Vulture and Merlin. The Griffon was an FAA back burner until the Vulture's resources were released so an early Griffon is really the only Rolls Royce option in time.

The Vulture was cancelled at the same time as the Exe and Peregrine. To allow resources for the Merlin and Griffon. But even the Griffon program was suspended during the BoB to concentrate on improving the Merlin.

The Griffon had one big advantage over the Vulture, Exe and Perergine - it was able to be fitted to the Spitfire and improve its performance. The Griffon was even redesigned to that end (before it had even got through the prototype stage).

 

[wuzak]

Griffon shared many things with Buzzard.

If "many things" consist of bore and stroke!

I suppose the general layout too - V-12, 4v per cylinder and flat combustion chambers. Not sure that any physical components were shared.

 

[tomo pauk]

You're probably right, re. Buzzard vs. Griffon.
Any particular favorite of yours, re. this thread?

 

[wuzak]

I'd have to say a tuned Buzzard/de-tuned R would be the best option for an engine to be availble prior to the beginning of the war.

 

[Shortround6]

On the contrary, Fulmar should be the 1st recipient of a big engine. There was a difference between fleet defenders that were able to catch Ju-88s, vs. the ones unable doing that. 2nd recipient might be one of the Hawker's heavy fighters. Then the Barracuda, then Firefly. Maybe install it on the Beaufighter, it was tested with Griffons historically.
Thanks for mentioning the 24Y - would you please provide some link about that, quick googling reveals only the post-war 24Z? The 24Y looks like a gem, comparing how hard it was for many of the countries to come up with 2000-2500 HP engines until late in war?

Going in reverse order, the 24Y is one of those engines who's appearance makes you want to gouge out your eyes with a spork ( plastic fast food utensil)

You have been warned 1938 | 3378 | Flight Archive

Two separate superchargers, 12 carburetors, 4 magnetos, a dry weight of 2160lbs (liquid cooled engine, how much for radiators and coolant?) 2200hp at 250rpm for take-off from a 4394 cu in (72 liter) engine. rated out put was 2000hp at 2400rpm at 10,800ft (3,300 m).

trying to stick this thing ( or a British clone) into a Fulmar is a disaster waiting to happen, even if you shorten that anteater inspired nose case. It is 370lbs heavier than an early Griffin and 700lbs heaver than a Merlin. It is lighter than a Vulture though so even a British 24 cylinder H engine is going to wind up heavier than a Vulture even if you you use Kestrel/Peregrine blocks. Fulmar went just over 7,000lb empty, sticking another 10% of it's weight in the nose (not including prop) isn't going to work too well. (or another 1/2 ton if your British 24 cylinder H weighs as much as a Vulture.)

A Vulture went about 2450lbs. Ah "H" type engine uses two crankshafts instead of one used by the "X" engine. The one crank is bigger and heavier but not twice as heavy. The "H" engine uses a bigger crankcase, more weight. The "H" engine uses a gear train to gear the cranks together ( usually) that the "X" engine doesn't. The "H" engine will be bigger ( or at least taller if placed on end or wider if laid over).

We are back to what size/weight plane you can fit on existing carriers. And not just "fit" but actually operate (like land using existing or only somewhat modified arrestor system)

You may get away with sticking an early Griffon in a Fulmar (but then that is why they designed the Firefly?) trying to stick in engines weighinghundreds of pounds more than the Griffon means going back to the drawing board and/or a loooong reserach and development period which cancels out your hoped for advantage.

From wiki: take for what you think it is worth

"Before the war, in 1938 the Air Ministry issued two specifications for two naval fighters, a conventional and a "turret fighter". Performance for both was to be 275 knots at 15,000 ft while carrying an armament, for the conventional fighter, of eight 0.303 Browning machine guns or four 20mm Hispano cannon. This would replace the Fulmar which had been an interim design. These specifications were updated the following year and several British manufacturers tendered their ideas. Further changes to the official specification followed, the turret fighter specification was dropped and a modified specification issued to cover single and dual seat fighters capable of 330 and 300 knots respectively. Fairey offering designs that could be single or two seater and powered by the Rolls-Royce Griffon or alternatively a larger airframe with a Napier Sabre. After consideration of manufacturers responses, Specification N.5/40 replaced the earlier specifications. Due to the necessity of navigating over open sea, it was for a two-seater alone.[1] For defence of naval bases a separate single seater design would lead to the Blackburn Firebrand.[2]
The Firefly was designed by H.E. Chaplin at Fairey Aviation; in June 1940, the Admiralty ordered 200 aircraft "off the drawing board" with the first three to be the prototypes. The prototype of the Firefly flew on 22 December 1941.[3] Although it was 4,000 lb (1,810 kg) heavier than the Fulmar (largely due to its armament of two 20 mm Hispano cannon in each wing)>

Please note they were planning on replacing the Fulmar in 1938 and the Fulmar was considered an interim design even in 1938, Also please note that Fairey was proposing a bigger airframe than the Firefly to hold the 2500lb Napair saber engine.
I would also note that wiki might be just a wee bit wrong in blaming the 4,000lb weight increase on the 20mm cannon. Like the the extra 300-400lbs of the Griffon, the larger radiators/oil coolers and coolant and the larger propeller had nothing to do with (not to mention the larger fuel tanks), in fact the empty weight of a Firefly I is 2735lbs more than a Fulmar II. empty weight is without guns.

 

[tomo pauk]

Going in reverse order, the 24Y is one of those engines who's appearance makes you want to gouge out your eyes with a spork ( plastic fast food utensil)

You have been warned 1938 | 3378 | Flight Archive

Two separate superchargers, 12 carburetors, 4 magnetos, a dry weight of 2160lbs (liquid cooled engine, how much for radiators and coolant?) 2200hp at 250rpm for take-off from a 4394 cu in (72 liter) engine. rated out put was 2000hp at 2400rpm at 10,800ft (3,300 m).

Thanks for that.
For the record: I do not consider any piston engine as being ugly! Now, jet engines...yuck.

trying to stick this thing ( or a British clone) into a Fulmar is a disaster waiting to happen, even if you shorten that anteater inspired nose case. It is 370lbs heavier than an early Griffin and 700lbs heaver than a Merlin. It is lighter than a Vulture though so even a British 24 cylinder H engine is going to wind up heavier than a Vulture even if you you use Kestrel/Peregrine blocks. Fulmar went just over 7,000lb empty, sticking another 10% of it's weight in the nose (not including prop) isn't going to work too well. (or another 1/2 ton if your British 24 cylinder H weighs as much as a Vulture.)

A Vulture went about 2450lbs. Ah "H" type engine uses two crankshafts instead of one used by the "X" engine. The one crank is bigger and heavier but not twice as heavy. The "H" engine uses a bigger crankcase, more weight. The "H" engine uses a gear train to gear the cranks together ( usually) that the "X" engine doesn't. The "H" engine will be bigger ( or at least taller if placed on end or wider if laid over).

We might remember the Fairey Monarch, flight tested aboard the Battle - there were no problems (engine weight- and size-wise)? Replaced the very Merlin. The cooling system can be relocated behind the CoG, as with Monarch Battle, that would account for ~300 lbs that front of the fuselage does not have to carry now. Seems like the Monarch was offering more power than the Vulture, wile being more than 10% lighter.

We are back to what size/weight plane you can fit on existing carriers. And not just "fit" but actually operate (like land using existing or only somewhat modified arrestor system)

You may get away with sticking an early Griffon in a Fulmar (but then that is why they designed the Firefly?) trying to stick in engines weighinghundreds of pounds more than the Griffon means going back to the drawing board and/or a loooong reserach and development period which cancels out your hoped for advantage.

From wiki: take for what you think it is worth

"Before the war, in 1938 the Air Ministry issued two specifications for two naval fighters, a conventional and a "turret fighter". Performance for both was to be 275 knots at 15,000 ft while carrying an armament, for the conventional fighter, of eight 0.303 Browning machine guns or four 20mm Hispano cannon. This would replace the Fulmar which had been an interim design. These specifications were updated the following year and several British manufacturers tendered their ideas. Further changes to the official specification followed, the turret fighter specification was dropped and a modified specification issued to cover single and dual seat fighters capable of 330 and 300 knots respectively. Fairey offering designs that could be single or two seater and powered by the Rolls-Royce Griffon or alternatively a larger airframe with a Napier Sabre. After consideration of manufacturers responses, Specification N.5/40 replaced the earlier specifications. Due to the necessity of navigating over open sea, it was for a two-seater alone.[1] For defence of naval bases a separate single seater design would lead to the Blackburn Firebrand.[2]
The Firefly was designed by H.E. Chaplin at Fairey Aviation; in June 1940, the Admiralty ordered 200 aircraft "off the drawing board" with the first three to be the prototypes. The prototype of the Firefly flew on 22 December 1941.[3] Although it was 4,000 lb (1,810 kg) heavier than the Fulmar (largely due to its armament of two 20 mm Hispano cannon in each wing)>

Please note they were planning on replacing the Fulmar in 1938 and the Fulmar was considered an interim design even in 1938, Also please note that Fairey was proposing a bigger airframe than the Firefly to hold the 2500lb Napair saber engine.
I would also note that wiki might be just a wee bit wrong in blaming the 4,000lb weight increase on the 20mm cannon. Like the the extra 300-400lbs of the Griffon, the larger radiators/oil coolers and coolant and the larger propeller had nothing to do with (not to mention the larger fuel tanks), in fact the empty weight of a Firefly I is 2735lbs more than a Fulmar II. empty weight is without guns.

Much of this is related at what engines would be available for the perspective costumers, within next 5-6 years.
FAA did have only one shiny new engine to base their planes in late 1930s - the Merlin (Taurus being an alternative; Hercules was overlooked??). Same goes for the Fairey, when they started developing the Fairey P.4/34 (Fulmar's predecessor). The new engines were ordered from RR (Exe and Griffon), but it would take time to have them produced, and needs of FAA were to take a back seat to the needs of RAF/AM. In case that RR have had in works the engine with plenty of power available in mid/late 1930s, there would've been a choice around what to design an aircraft.
Anyway, it was a pity that RR didn't further refined the Goshawk, in parallel with the PV.12/Merlin.

 

[Shortround6]

We might remember the Fairey Monarch, flight tested aboard the Battle - there were no problems (engine weight- and size-wise)? Replaced the very Merlin. The cooling system can be relocated behind the CoG, as with Monarch Battle, that would account for ~300 lbs that front of the fuselage does not have to carry now. Seems like the Monarch was offering more power than the Vulture, wile being more than 10% lighter.

OK, we have flight tested, Plane only has to carry the new engine, test instruments and an observer. No war load and does not have to perform combat maneuvers.

We also have the Battle with 8 ft more wing span, 2 ft more length and 80 sq ft more wing and NOT trying to operate from a carrier like the Fulmar. Battles were used as test hacks for a variety of engines.

The last is supposed to have a Napier Sabre installed.

Nobody had noted (yet) how much ballast was used in addition to the radiator relocation in order to get these things to fly, and again, the only intention of these installations was to provide flying test beds for the engines, NOT provide higher powered Battle combat aircraft.

Much of this is related at what engines would be available for the perspective costumers, within next 5-6 years.
FAA did have only one shiny new engine to base their planes in late 1930s - the Merlin (Taurus being an alternative; Hercules was overlooked??)

.

Actually the FAA was hopping for the Griffon even if not in quite the Version is was made in. The Taurus was in no way, shape or form an alternative to the Merlin. A 1550 cu in ( 25.4 l) air cooled radial with 11.7 sq ft of frontal area is NOT a competitor to a 1650 cu in (27 l) liquid cooled engine with 5.8 sq ft of frontal area (+ radiator). Taurus was good for about 1065-1080 hp at low attitude or take-off on 87 octane, A Merlin VIII could pull 1275hp at 9lbs at sea level using 87 octane. Taurus was "supposed" to be a low drag, small diameter replacement for the Pegasus.

Anyway, it was a pity that RR didn't further refined the Goshawk, in parallel with the PV.12/Merlin.

On god's green earth, WHY????? the thing was a complete and utter failure! and look at it again. Same bore and stroke as a Kestrel/Peregrine, it wasn't going to make any more power at the same boost and rpm as the Peregrine without direct divine intervention.
Deity of your choice shows up in the R-R engine shop, waves his/her hand/s mutters a few words and repeals the laws of physics for that one engine model.

 

[tomo pauk]

Whoops, not Goshawk, but Buzzard. Sorry about that mistake.

 

[Shortround6]

Whew! for a minute there I thought you had gone round the bend.........

A few papers on an American evaluation of the Fairey Monarch engine.

http://www.enginehistory.org/Misc/P152543.pdf

If R-R had continued with development of the Buzzard/R engine it might have come out bulkier than the Griffon that did result and been harder to fit in a Spitfire airframe without rework, however a 1400-1500hp engine on 87 octane fuel (low level) might have allowed for a Fulmar III/early Firefly and a Barracuda somewhat earlier that historically.

 

[yulzari]

It all rather reminds one that Britain could have got through the whole war with just the Merlin plus Cheetah for trainers and light transports.

 

[Shortround6]

Well, the Hercules did power an awful lot of aircraft.

 

[wuzak]

Whew! for a minute there I thought you had gone round the bend.........

A few papers on an American evaluation of the Fairey Monarch engine.

http://www.enginehistory.org/Misc/P152543.pdf

Not exactly a glowing report.

I think it was light because it was lightly built. Which would be a problem for future developments.

 

[merlin]

Whew! for a minute there I thought you had gone round the bend.........

A few papers on an American evaluation of the Fairey Monarch engine.

http://www.enginehistory.org/Misc/P152543.pdf

If R-R had continued with development of the Buzzard/R engine it might have come out bulkier than the Griffon that did result and been harder to fit in a Spitfire airframe without rework, however a 1400-1500hp engine on 87 octane fuel (low level) might have allowed for a Fulmar III/early Firefly and a Barracuda somewhat earlier that historically.

Interesting link - especially D Recommendations - I wonder does that refer to US engines being built in the UK or UK engines being built in the US ?? If the former, do we get the P W 1830 at Armstrong Siddeley, and Wright Cyclone R 2600 at Fairey !!??