GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
There was a lend-lease agreement, wich stated that Packard manufactured Merlins for Britain with the stipulation that the US was allowed to get a percentage license-free for the duration.
Jumo 213 vs. Napier Sabre
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wuzak
Captain
2,380hp was a development rating, allowed for flight. That used 3,300rpm, PN150 fuel and +30psi boost without ADI.
2,600hp+ was achieved with +36psi boost, PN150 fuel + extra TEL, ADI and 3,150rpm.
From my recollection.
The service rating for the RM.17SM was 2,200hp in MS gear and 2,100hp in FS gear.
wuzak
Captain
Allison V-1710-145 - 2,250hp @ 3,200rpm, 100inHg MAP, with ADI.
Packard V-1650-9 - 2,270hp @ 3,000rpm, 90inHg MAP with ADI.
More rpm and more boost to get less power!
Deleted member 68059
Staff Sergeant
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- Dec 28, 2015
Service limit for operational planes with Merlin-66 at 25 lbs boost exceeded 2000hp in January 1942.
No operational service V-1710`s exceeded 1800hp during the entire war in the west (V-1710-93 + 130PN fuel + ADI)
I think in a hypothetical scenario where the war would have dragged on for a few more years, and jets would also have been delayed a few years, we could very well have seen Griffon powered Mustangs. It seems to me that because the war was drawing to a close and jets being on the imminent horizon, there was never the same effort spent in improving the Griffon as the Merlin. But considering that Griffon was essentially a scaled up Merlin, to a rough approximation it should have been able to produce an equal amount of power per liter as the Merlin.
In hindsight we can see how sleeve valves were not such a great idea. But at the time, it was of course different, especially with a guru figure like Ricardo being a proponent. Would we have ever known that sleeve valves were a Jonah if not for Roy Fedden, Frank Halford and teams spending years tearing out their hair trying to make them work (and even then only managed to produce maintenance nightmares that perhaps entered service only because of wartime desperation?)? In a sense it's just standard R&D, you try a lot of different things, most of which turn out to not be such a good idea.
I guess the tragedy of sleeve valves was that finding out they weren't such a splendid approach happened to the good guys in a backs to the wall total war against fascism, possibly slightly prolonging the war and causing more casualties.
As for a modern usage of sleeve valves, I recently stumbled upon a RC plane engine: https://www.rcgroups.com/forums/sho...-91-CD-Four-Stroke-Rotary-Sleeve-Valve-Engine
BarnOwlLover
Staff Sergeant
Problem with the Griffon is that it was larger and heavier than the Merlin (fit in the same box in terms of length and width, but was taller and significantly heavier), and the larger displacement meant more cooling (ie, the much larger radiators on the Spitfire 14 vs the Spitfire 9) and being more fuel thirsty. Sadly, I don't think the "bigger engine, more torque, lower revs mean potential for better fuel mileage" that works with cars works the same way for airplanes. Also, the larger displacement should in theory mean less supercharger boost needed for the same power, but Griffon 60 and 80 series engines by war's end were running the 18 and 25 lbs boost ratings that the Merlins were, and, strangely, not making the amount of power that having 10 more liters of displacement would suggest IMO.
Putting an engine in the Mustang that dry weighed 350 or so lbs more than the Merlin would've played havoc with CG and range on internal fuel. Granted, the P-51 usually had issues with full rear fuselage tanks so that might have cancelled the nose-heaviness out to a degree, especially as the radiator and fuselage tanks probably would have to be made larger, though that also brings about it's own design issues. The Mustang's cooling system already had to be heavily modified to go from the single stage Allison to the two stage Merlin. And going to the Griffon would mean round two as far as those mods, just like when the Spitfire went from from the single stage Merlin to the two stage Merlin, to the Griffon.
Shortround6
Major General
Actually putting 500lbs ahead of the CG would have balanced out the weight aft and turned the plane into a lamb.
Except the ferocious torque of the Griffin would have made the P-51's already 'exciting' tendency to drop a wing and roll as it unstuck even more 'exciting' - it was a borderline dangerous plane until it got moving and gained enough control authority.
wuzak
Captain
And the torque being the other direction.
They could always have fitted the contra-prop Griffon to solve that.
wuzak
Captain
Actually, the Griffon was longer.
Given the same efficiency, more power = more fuel.
The fact that the 2 stage Griffon has more power in high gear than the 2 stage Merlin does in low gear at the same boost and their respective critical/FTH altitudes might be significant.
And, yes, the Griffon was less developed.
- Thread starter
- #33
Thanks for the explanation.
Exhaust thrust of the engine seems to be often forgotten when it comes to propulsion and for all I know the Jumo 213 seemed to be especially good in this regard as well. Though delivering less hp on the shaft than comparable DB 603s it yet provided greater all-around propulsion because of that.
Wrt fuel burn, I don't recall any figures but I'd be surprised if Griffon had very different BSFC compared to the Merlin. Of course, given identical BSFC a more powerful engine will burn fuel faster than a smaller one at max power. At identical cruise power I'd expect both of them to be fairly close. Of course, a Griffon plane would need to haul around a heavier engine and draggier radiator, but I wouldn't think those would have a dramatic impact.
But all the same, what's the alternative? In the hypothetical scenario I outlined with the war dragging on and jets not in sight, Germany would likely have been deploying things like Do-335 and Ta-152 in nontrivial numbers, and the Allies would have needed more top speed to keep up, slightly worse fuel burn at cruise be damned.
And yes, this would certainly have required a heavily modified plane just like the Spit was modified to accommodate the Griffon. But just based on the Mustang being a bigger and heavier plane than the Spit, I'm sure it would have been doable.
Is it known why Jumo engineers doesn't changed much earlier to 4-valve-heads, as example with the precedessor models 210 or 211?
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Hypothetical scenarios always seem to favor one side over the other. With the war dragging on, where do you draw the line as to Allies on the mainland or not? On the mainland range of fighters becomes less worrisome (and performance goes up as fuel loads can be decreased and or smaller drop tanks made / utilized), and the ability to generate both air to air and air to ground sorties goes up (ASD - average sortie duration) length goes down. Put bombers on the mainland and their bomb loads go up, and time over bad guy territory goes down (so does risk to a degree). Allies on the mainland equals greater force brought against the Germany. Allies not on mainland, Russians somehow held off, German economy somehow still able to produce soldiers, weapons, food, and fuel (on going problem for years) and improvements needed on long range escorts. As Stalin is oft quoted as say, "Quantity has a quality all of its own". Or the Allies could have just produced more fighters. This allows you to fly over Germany and set up caps above their airfields, and or do sunrise strikes, and effectively keep the "higher performing" German fighters on the deck. Enough fighters and you could do this all day (logistically fuel, food, men and aircraft can be supplied which Germany couldn't keep up with).
There are several ways this could be scenario'd or gamed out. I think it would have been great to see a Griffon Mustang with contra props, but I think that a P51H with extra ADI and a few other mods would have been sufficient, especially in quantity.
Cheers,
Biff
Deleted member 68059
Staff Sergeant
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- Dec 28, 2015
I dont have "a letter" saying "we didnt do this because xyz" but you can infer a probable reason.Is it known why Jumo engineers doesn't changed much earlier to 4-valve-heads, as example with the precedessor models 210 or 211?
The early Jumo`s were earmarked for bombers after a bit of to-ing-and-froing between them and DB600 series for the 109.
Bomber engines have lower ratings as they usually have to fly longer and reliability tends to be more emphasised, so the
low revving 210/211 were quite adequate with 3-valve heads, in fact they were probably better for it.
Even the 213 was fairly low revving, early on, but then the war goes a bit sour and you need to get a big perfomance leap very
suddenly, and the 213A is being fitted to fighters (190-D9), so things change and you need to push the boundaries
and push the revs up. now, the 3-valve head is strangling the engine breathing. So the 4-valve head was to compliment
the 3700rpm of the 213-J (proposed to extend to 4000rpm so the engineers said under interrogation).
They probably wanted to change it in 1940 or so I think, but its such a huge tearup of the engine design
that its likely it got decided against unless they were forced to.
Shortround6
Major General
Why didn't Hispano switch to 3 valve heads instead of keeping using 2 valve (and a bad two valve layout at that)?Is it known why Jumo engineers doesn't changed much earlier to 4-valve-heads, as example with the precedessor models 210 or 211?
If you can get the needed air into and out of 3 valve head at the rpm you are intending to run then a 4 valve head doesn't get you much.
They were using 4 valve heads in WW I, nothing new, except............sometimes the reasons change.
Big valves in WW I tended to warp, especially exhaust valves. Two small valves resisted warping better, had more valve in contact with valve seat for better cooling, each valve was lighter so the valve springs didn't have to be as strong and so on. In the 20s and with better valve seat material, coating of the valve face area (where it hits the seat) and with sodium salt cooling larger valves could be used with less cooling problems and less sticking/burning and one big valve may have been cheaper than 2 small ones.
don't need as many triple wound valve springs either
The first 4 valve heads may have been used in Grand Prix cars in 1913 if not earlier (?). every engine designer worth his T square knew about them.
The question is if they were worth it in his application.
BarnOwlLover
Staff Sergeant
To touch on the Merlin vs Griffon for a second, I do wonder why the later DH Mosquitos and the Hornet weren't envisioned to use the Griffon? Both aircraft stuck with the two-stage Merlin until they left production. I do wonder if size (size of engine and power relative to the size of the aircraft) played a role. Especially considering that the Hornet was originally designed around Merlin 60 series engines (got the 130 series instead that were largely designed for it and were significantly more powerful than the 60 series) and the plane was designed to weigh about 15,000 lbs give or take, which the Hornet F1 in clean take off (per post 2010 books like DH Hornet and Sea Hornet: de Havilland's Ultimate Piston Engine Fighter and Airframe Album 8: de Havilland Hornet and Sea Hornet) was actually a fair bit below the envisioned 15,000 lb weight.
Also, perhaps strangely, later Merlin 130 series engines were derated to have a normal boost of 18 lbs vs 25 lbs, though that reduction only knocked about 40 hp out of those Merlins (and had no impact on the Hornet's performance, though as far as the specs I did read, very slight performance differences--+/- 1mph and +/- 10 fpm climb rate--occurred due to a prop design change). And even the Spiteful was designed to possibly use the Merlin as a contingency measure in case the primarily intended Griffon 60 series engines ran into problems.
But I do guess as far as Griffon vs Merlin, I also guess that's also maybe a case for horses for course, like the Spitfire vs Mustang.
Now Jumo 213 vs Sabre. The Sabre did benefit from being high revving and 100+ octane fuel, which even for the Sabre did allow for better supercharging (though it wasn't comparable to the Merlin or Griffon in that respect). The Sabre eventually got to 25 lbs of boost, but that wasn't until late-war/post war development versions.
The Jumo 213 also obviously benefited from higher revving vs the DB 600 engines. And all German engines could've benefited from better supercharging, but the lack of steady supplies of 100+ octane fuel prevented this.
Of note, is that the Jumo 213 was, when it was being improved, was seen as an alternative to the DB 603, and even had identical mounting points and fluid line pick ups as the DB 603. And again, just like Merlin vs Griffon, like in my hypothetical fighter threads, I'll have to favor the Jumo 213 here, as it was in this case easier to package and smaller in cubic displacement (though both engines actually weighed about the same).
Also, perhaps strangely, later Merlin 130 series engines were derated to have a normal boost of 18 lbs vs 25 lbs, though that reduction only knocked about 40 hp out of those Merlins (and had no impact on the Hornet's performance, though as far as the specs I did read, very slight performance differences--+/- 1mph and +/- 10 fpm climb rate--occurred due to a prop design change). And even the Spiteful was designed to possibly use the Merlin as a contingency measure in case the primarily intended Griffon 60 series engines ran into problems.
But I do guess as far as Griffon vs Merlin, I also guess that's also maybe a case for horses for course, like the Spitfire vs Mustang.
Now Jumo 213 vs Sabre. The Sabre did benefit from being high revving and 100+ octane fuel, which even for the Sabre did allow for better supercharging (though it wasn't comparable to the Merlin or Griffon in that respect). The Sabre eventually got to 25 lbs of boost, but that wasn't until late-war/post war development versions.
The Jumo 213 also obviously benefited from higher revving vs the DB 600 engines. And all German engines could've benefited from better supercharging, but the lack of steady supplies of 100+ octane fuel prevented this.
Of note, is that the Jumo 213 was, when it was being improved, was seen as an alternative to the DB 603, and even had identical mounting points and fluid line pick ups as the DB 603. And again, just like Merlin vs Griffon, like in my hypothetical fighter threads, I'll have to favor the Jumo 213 here, as it was in this case easier to package and smaller in cubic displacement (though both engines actually weighed about the same).
When that reduction of boost took place?
That's very interesting. What source confirms +25 psi boost for post-war Sabres?
Jumo 213E and F were outfitted with 2-stage superchargers, and were still using 87 oct fuel.
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