Or, in other words, RR de-tunes & modifies 'R' engine in early 1930s so it can be produced in series, for military aircraft mostly. For the sake of discussion, they do this instead of designing the Merlin. How much the RAF can gain with this? What is likely to change in aiframe design of future fighters and bombers? Expected performance of engine on 77, 87 and early 100 oct fuel?
Rolls Royce 'militarized R' engine - one engine to rule them all?
- Thread starter tomo pauk
- Start date
Ad: This forum contains affiliate links to products on Amazon and eBay. More information in Terms and rules
wuzak
Captain
A detuned R was tested by Rolls-Royce as the Griffon I in around 1933.
The Buzzard, on which the R was based, had 800hp and weighed about 1,150lb.
The R of 1931 had around 2,500hp and weighed about 1,650lb. Albeit a lot of that was the huge supercharger.
I'm not sure how much power a Griffon I could have done. Perhaps 1,500hp for 1,500lb.
The Buzzard, on which the R was based, had 800hp and weighed about 1,150lb.
The R of 1931 had around 2,500hp and weighed about 1,650lb. Albeit a lot of that was the huge supercharger.
I'm not sure how much power a Griffon I could have done. Perhaps 1,500hp for 1,500lb.
Reluctant Poster
Staff Sergeant
- 1,383
- Dec 6, 2006
The Griffon I was seriously overweight and had to be extensively redesigned. The Griffon II was really a different engine.
Last edited:
wuzak
Captain
The Griffon II was a completely different engine
Shortround6
Major General
Awh, common on guys, it used the same bore & stroke 
wuzak
Captain
The Merlin did have nearly the same stroke:bore ratio as the Griffon, Buzzard and Kestrel. 1.111 vs 1.10.
I suspect the size of the Merlin was dictate by the power out desired. 27L was enough to get 1,000hp in the mid 1930s.
- Thread starter
- #8
For sake of discussion, let's say that early big engine makes 1250 HP at @ 2600 rpm 15000 ft, 87 oct fuel, 1500 lbs dry weight. How this might influence the design of the Battle, Hurricane or Spitfire? Performance of the fighters should be improved by a good margin?
What about licence production in other countries, once the UK production is under way? Germans and French look at their engines and go "damn"?
- Thread starter
- #10
We have quite a war to fight before P-51 gets the Griffon.
Shortround6
Major General
This doesn't quite get you a Griffon II of WW II early. You are almost 300lbs too light. It also rather ignores the trial and tribulations the Merin went through, like the ramp head excursion and other problems. You might well be able to make a 1250hp engine that weighs 1500lbs but when you push for the 1700-2000hp versions things may start to break or at least wear out quickly. RR was able to use everything they learned with the Merlin over 4-5 years on the "new" Griffon engine.
Performance might well be better for the fighters but then a 1934-36 fighter with a Grifzard engine might have trouble landing at many RAF airfields of the time( Or so the powers that be might think) leading to bigger wings to get the landing speed down. If they are putting flaps on the Gladiator biplane to get the landing speed down the idea of a monoplane with an over 1500lb engine in the nose gets a bit harder to swallow.
one of the reasons (but not the only one) that the Supermarine 224
was rejected was that it landed too fast.
295 sq ft of wing area, a weight of 4743lbs and a landing speed of 60mph which was 10mph faster than the specification called for.
Of course you also have to beat the men in the Air Ministry over the head with a cricket bat (or several) to make them give up on the idea of a two bladed wooden prop being suitable for fighters if you want to shove a 1200hp 36 liter engine into a fighter
Getting designers and buyers to jump from 600hp engine to 1000hp engines was hard at times, trying to get them to jump from 600hp to 1200hp was going to be even harder. However the "market" often did not realize how long it took to bring a modern engine to production. It had only taken months for such engines as the Hispano-Suiza, the Liberty and the RR Falcon and Eagle in WW I to go from drawing board to production. In the 1930s the engine that was too big one year was the engine they were clamoring for 2 years later when it took 3-5 years to develop such an engine.
- Thread starter
- #13
I was purposely conservative on what kind of power the early big engine will make, not just in order to make the scenario realistic (at least the 'what if' kind of realistic). The 1250 HP at 15000 ft will mean 1400-1500 HP down low with 100 oct fuel and/or 2-speed S/C. Please note that I've never mentioned Griffon II here.
In this scenario, RR from mid-30s to early 1940s have just one powerful engine to perfect, not two.
Shortround6
Major General
They could have both, can the Exe and the Vulture
Both demonstrate, however, the technical complexities thought to be needed to get maximum power from the available fuel of the time. As fuel got better and higher boost could be used to get more power from smaller (or less complicated) engines the interest in such engines faded, only to come back again as fuel limits began to be reached once again. RR Eagle 46 liter 24 cylinder sleeve valve, Sabre on steroids.
- Thread starter
- #15
They could have both, can the Exe and the Vulture
Both demonstrate, however, the technical complexities thought to be needed to get maximum power from the available fuel of the time. As fuel got better and higher boost could be used to get more power from smaller (or less complicated) engines the interest in such engines faded, only to come back again as fuel limits began to be reached once again. RR Eagle 46 liter 24 cylinder sleeve valve, Sabre on steroids.
Yes, Exe is axed in any what-if RAF scenario, ditto for Vulture in most of them
I'd like to see RR making a H-16 spin-off of the big engine here...
Okay, this is how it might look like, for our 'big V12', 1st service/squardon use:
1935: Mk.I, 1250 HP at 2600 rpm @ 15000 ft, 1080 HP for take-off, impeller diameter 10.5in, 1500 lbs
1939: Mk.II, rated for 100 oct (say, 1500 HP at 10000 ft)
............Mk.X, 2-speed S/C, 1400 HP for take-off, 1500 HP 1st rated altitude, 1250 HP at 2nd rated altitude (15000 ft), all for 87 oct, 1600 lbs
1940: Mk.III, 2700 rpm, 100 oct, 1600 lbs, 1400 HP for take off, 1600 HP at 10000 ft, 1300 HP at 16000 ft,
............Mk.VIII, 2700 rpm, low-level engine, 1600 HP at S/L on 100 oct, 1250 on 87 oct
............MK.XX, 2700 rpm, 2-speed & improved S/C, 1600 HP for take-off, 1700 HP at 5000 ft, 1500 HP at 16000 ft, 1700 lbs; licence production at Packard
early 1941: Mk.45, 1-speed S/C-ed version of the Mk.XX, 1600 lbs
Deleted member 68059
Staff Sergeant
- 1,058
- Dec 28, 2015
In my experience of re-purposing race engines for more endurance applications (which I have done on 2 occasions professionally), by the time you add mass to make the bits last long enough, remove half the tiny little tweaks in materials and hand-fettling which are too expensive for mass production, remove the ultra-special fuels and re-tool it to be suitible for making in the dozens or hundreds, you end up with something not much better than you would have done if you just designed from scratch something to do the job properly from square 1.
All sorts of "tiny" issues which didnt matter on the race engine suddenly become show stoppers (eg. torsionals which didnt matter in the race engine at high crank speeds, suddenly ruin engines which are running at slightly lower revs, etc etc).
I think the Merlin was about the ideal balance of size, strength and weight for use in small single-seaters which we had in the 30s, and the Mustang proved that this had in fact not changed a great deal by 1944. This of course ONLY holds true if you have access to the very best fuels, oils and materials. If we had needed to fight the war on 87 octane, we would have been in a really bad place with the Merlin, so there are I think a lot of cavets to either option.
I think with the Griffon you`re right at the limit of sensible bore size for combustion, and that probably - it will always be possible to "push" a smaller Merlin a bit harder with boost before det sets in, this I think (partially) nullifies the advantage in swept volume the Griffon has over the Merlin providing that 100/130/150 is available as fuel. Later developments with the Jumo213 and of course Sabre showing that ultimately crank speeds needed to go up too. Eventually a bigger Griffon engine would be less amenable to this line of development due to the inevitably larger mass of the pistons etc. So I think overall, what happened probably shows us what the best option was, because the Griffon never became militarily significant, because it simply wasn`t the best overall option.
If the war had gone on further we all know that Griffon Mustangs and Mosquitos were planned, but with the jet coming in, I`m not sure we would have bothered with them for the sake of an 18month overlap with the early jets until they took over. I think the Spitfire XIV was a brutal fighter, but the tiny numbers produced tend to suggest it was also not really a necessity and if we HADNT had both engines, I`m unconvinced a Griffon Mustang would have been the escort fighter we needed, which was a war-winner, so I think what actually happened was pretty much what I`d do if I had a time machine and did it again.
Last edited:
[/QUOTE]one of the reasons (but not the only one) that the Supermarine 224 was rejected was that it landed too fast.
295 sq ft of wing area, a weight of 4743lbs and a landing speed of 60mph which was 10mph faster than the specification called for.
[/QUOTE]
Which is pretty funny when you consider the Luscombe was flying only 4 years later with about a 65-70 MPH approach speed. (It's been so long, if I remember correctly the stall was 44 mph.)
295 sq ft of wing area, a weight of 4743lbs and a landing speed of 60mph which was 10mph faster than the specification called for.
[/QUOTE]
Which is pretty funny when you consider the Luscombe was flying only 4 years later with about a 65-70 MPH approach speed. (It's been so long, if I remember correctly the stall was 44 mph.)
Shortround6
Major General
The Boeing P-26 fighter landed at about 80mph in the early version but they were refitted with flaps to get the landing speed into the low 70mph range.
the 149.5 sq ft wing may have helped top speed but take-off and landing on short fields may have been exciting.
landing speeds and take-off/landing distances are one of those pesky details than often don't make it into discussion on why certain countries did certain things or adopted certain airplanes.
the 149.5 sq ft wing may have helped top speed but take-off and landing on short fields may have been exciting.
landing speeds and take-off/landing distances are one of those pesky details than often don't make it into discussion on why certain countries did certain things or adopted certain airplanes.
wuzak
Captain
957 is tiny numbers? I suppose compared to the number of all Spitfires built, or Bf 109s, but not insignificant.
Hives pushed for the Griffon as an option for The P-51, but NAA rejected the idea based on the extensive redesign that needed to be done.
A Griffon powered Super-Mosquito was proposed, but it was felt that the performance increase was not there. This is because the Griffon Mosquito would have been a larger aircraft that would be capable of a heavier bomb load.
As an aside, as mentioned in other threads, the Air Ministry was exploring ways to take advantage of the larger capacity of the bulged bomb bay, which had been designed around the 4,000lb HC and MC bombs. The first proposals revolved around increasing the capacity of Target Indicators that could be carried - from 4 x 250lb TIs (6 if using wing racks) to 6 or 8 internally, depending on the rack scheme. The 8 bomb system, using a modified Wellington rack, could also accommodate 8 x 500lb MC bombs, but de Havillands said that the CoG would be too far back on the B.XVI. Had the B.XVI been fitted with the longer, heavier Griffons ahead of the CoG the bomb scheme may have been possible.
wuzak
Captain
Instead of starting with the R, with its mammoth supercharger, why not improve the Buzzard?
The Buzzard had 800hp from 1,140lb dry weight. With improved technologies, such as the steel backed bearing, and improved fuels it is not inconceivable to see the Buzzard at 1,000lb for not much more weight.
And some strengthening and the power could go up to early Merlin levels, at about the same weight.
Developing
