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The R-2800 is a bit too big and heavy to serve as a substitute Merlin.
The US kept 1/3 (at most) of Packard production, some sources say as little as 20%. If Packard doesn't make Merlins that means no Merlin powered P-40s ( not much of a loss) and No Merlin Mustangs ( a much bigger loss)
but it also means 36,000-44,000 fewer Merlins for British and Canadian production aircraft. and that is the big loss in this scenario. For existing US engines the R-1820 and R-1830 are too small. The R-3350 is too big and too late. The R-2800 is too big for many applications, It rather leaves the the R-2600 (Hercules replacement in some aircraft and since the Hercules and Merlin both worked on a number of aircraft it might be a small change) and the Allison V-1710, as "plug in" replacements for existing aircraft, at least in a physical size sense.
A Halifax or Lancaster with four R-2800s might be a wondrous airplane but either one with four R-2600s might require a whole lot less redesign. Hurri-bombers with V-1710s might work.
In 1940-41 the British NEED another source of engines to power the airframes they are already planning to make in 1942-43. They don't need a source of engines that won't be making large quantities of engines until 1943/44 and need new airframes to make use of the larger engines. They already have 4 engines larger than the Merlin in the pipeline themselves.
Thanks for bringing us back to the topic
Wouldn't it depend upon the airframe that is about to receive the replacement? I can see the Spitfire as being too light for the R-2800, but not the P-51. We can take a look at the soviet examples - they re-engined the Lagg-3 and Yak-3 with the Ash-82, creating the La-5 and Yak-3U.
How feasible would be the turbo V-1710s for the British bombers; installation a-la the XB-38?
The single-stage V-1710s for the Mossie FBs (plus the Coastal command planes). Beaufighter with V-1710 or single stage R-2800?
The Hurricannes loosing the two-speed Merlins, while receiving V-1710s (Merlins go to the heavies)?
Of course they need the yet another source, and Packard was providing them with meaningful number of engines from 1942 on. Not producing the Merlin, it can produce V-1710 in same quantities (or bigger?). With one of their tasks now made easier, Allison can introduce the 2-stage variant easier/earlier?
If there wasn't any US production of the Merlin then the US would have probably arrived at this solution a lot earlier without the politics;
The P-51J with the V1710-119
Thanks for bringing us back to the topic
Wouldn't it depend upon the airframe that is about to receive the replacement? I can see the Spitfire as being too light for the R-2800, but not the P-51. We can take a look at the soviet examples - they re-engined the Lagg-3 and Yak-3 with the Ash-82, creating the La-5 and Yak-3U.
Within a scope of this thread: how feasible is the P-51 with 2-stage V-1710/R-2800, for, say, Big Week to be operating in meaningful numbers (the Packard being second source for the V-1710 or R-2800)?
How feasible would be the turbo V-1710s for the British bombers; installation a-la the XB-38? The single-stage V-1710s for the Mossie FBs (plus the Coastal command planes). Beaufighter with V-1710 or single stage R-2800? The Hurricannes loosing the two-speed Merlins, while receiving V-1710s (Merlins go to the heavies)?
Is Allisons task made easier? or do Allison have to help oversee production in a separate facility for the first few months/year?Of course they need the yet another source, and Packard was providing them with meaningful number of engines from 1942 on. Not producing the Merlin, it can produce V-1710 in same quantities (or bigger?). With one of their tasks now made easier, Allison can introduce the 2-stage variant easier/earlier?
This should not be read as the 'Allison was every inch as good as Merlin' mantra, but something that should inspire the further discussion about the choices for the W. Allies that do not have US-built Merlins in the ww2.
Why would taht be the case?
Before the P-51 was fitted with a 2 stage Merlin was there any push for a high altitude version from the USAAF?
They use Rolls-Royce engines, which is what they did, anyway. The contract, with Packard, was not signed until September 3rd., 1940, and the first engine was produced in September 1941.If Packard doesn't build Merlins what engine choice do the British have in the summer of 1940 to power their planes? .
It was already thought of, and Packard were given a set of Griffon drawings at the same time as they received those of the Merlin.For Wuzak's question:
"Another alternative - what if Rolls-Royce foresaw a need for more Griffons, and requested Packard set up a new line for them, to run alongside the Merlin? I imagine the decision would be mid 1941, after the Griffon had some testing behind it or had flown in the Spitfire (Mk IV - which flew in late 1941).
It was already thought of, and Packard were given a set of Griffon drawings at the same time as they received those of the Merlin.
They use Rolls-Royce engines, which is what they did, anyway. The contract, with Packard, was not signed until September 3rd., 1940, and the first engine was produced in September 1941.
Not sure that the performance would be there for an R-2800 Mustang.
Not very.
The turbo in the XB-38 was mounted in the standard nacelle in the wing, in its original location, not in the V-1710 engine module. The radiators for the V-1710s were in the wing leading edge between the nacelles, and not in the QEC.
V-1710s for Mossie FBs would be possible, but would require changes to suit those particular models. The single sage Allison may not be the best for all FB missions, though, and is definitely not good for PR, NF and B versions.
Most Beaufighters had the Hercules, which wasn't built in the US but had sufficient numbers for what they were being used. No need for the R-2800 here. The number of Merlin models is relatively small - about 600 and, I believe, built before US production of Merlins commences, so no need for a replacement.
Maybe Hurricane production is cut earlier in favour of the Typhoon and the R-2800 Tornado (single stage). The latter is an interim fighter until the Centaurus powered Tempest II is ready, but since that arrived very late in the war it is essentially replacing the Hurricane.
Having Packard involved would surely increase the amount of engineers available for development. If Allison assign some areas of development to Packard (like the V-3420) that would free up their own development time for the two stage project.
The Ash-82 was more of a R-2600 sized engine. R-2600 "B" --1980lbs, Ash-82--1984lbs, Hercules XI--1850lbs, R-2800 A series with single stage two speed supercharger 2270lbs, R-2800 with two stage supercharger 2480lbs without inter-coolers and ducts. And that is just for the engines.
The R-2800 needs a bigger propeller if you want to get the full benefit. At most times the R-2800 was giving about 15% more power than an R-2600 but also weighed about 15% more, a bit better in the power to frontal area ratio though.
Like I said before some planes might not have too much trouble. Wellington with two R-2800s? Lots of room to shift things around to balance the weight. Beaufighter with two R-2800s? you have added over 1/2 ton as far forward as you can go with the weight. Halifax? maybe but while certainly more powerful you have added over a ton to the empty weight and if you use the power you WILL suck down more fuel. You have the power to lift it but you may need to beef up parts of the plane to stand up to the extra weight and power, like heavier landing gear. Possible but no longer a "plug in" replacement.
as far as the R-2800 goes. the Merlin instillation a P-51B/C went about 3246lbs not including fuel system or oil. The R-2800 system in the F6F-3 went 3917. Almost 700lbs more and ALL forward of the front wing spar unlike the P-51 which had several hundred pounds (400-500?) behind the rear spar? P-51 used a 11'2in 4 blade prop. F6F used a 13'2 in 3 blade prop. Unless you use a smaller prop the same thrust line is going to mean a lot of plowed up runways
using a smaller prop may be a problem, I am not sure how much of the propeller disk in front of the engine really contributes to the thrust. The R-2800 is 52in in diameter or 4 ft 4 in. Merlin is 30 in wide (2ft 6in) and 40 something high but it tapers and is smaller in height at the front than the rear.
North American may be able to design an R-2800 powered fighter, it may even use the same wing as the P-51, I just don't think much else would be the same. And you can pretty much kiss off long range bomber escort missions. You have a higher drag airplane with a thirstier engine. Not a recipe for long range. Army figured combat radius for bomber escort at 310mph true airspeed at 25,000ft for the cruise portion of the mission profile.
the 2-stage V-1710 is a possibility but it is far in the future in the summer of 1940.
1. "turbo V-1710s for the British bombers". I have mentioned this before, feasible but at the cost of higher maintenance costs. Power eggs with turbos could be a problem, turbos liked a little distance between the engine and the turbo, longer exhaust duct meant cooler exhaust hitting turbo blades and thus longer life for the turbo.
2. " The single-stage V-1710s for the Mossie FBs (plus the Coastal command planes)". Again feasible but why? without WEP settings Allisons (in historical models) top out at 1325hp for take off. And the engine in the A-36 could only hold 1325hp to 3200ft without going into a WEP setting. Fitting low altitude Allisons to these planes means really low altitudes. No choice of even trying to fly/fight at 10-20,000ft. Fitting higher altitude Allisons means too little power for take-off.
3. Beaufighter? The Allisons won't give the power for either night fighter missions compared to Merlin XX or Hercules engines and won't give the needed power for strike missions. Weight and balance problems with R-2800s have been mentioned before.
4. Hurricanes? possibly the best choice but again you are really limiting the plane to well under 10,000ft.
ngIs Allisons task made easier? or do Allison have to help oversee production in a separate facility for the first few months/year?
This also skips over the British problem, how much engineering time do they spend on all these alternate engine installations rather than getting the engine they want that will drop into the airframes with little or no engineering time spent?
At times the Allison was every bit as good as the Merlin, unfortunately, the summer of 1940 was not one of those times. In the summer of 1940 the Allison supercharger was as good as the supercharger on the Merlin III and Merlin X, unfortunately the Allison "C" series reduction gear was suspect and the block needed a bit of beefing up. AND Hooker had started his work and the Merlin XX was ready with the improved single stage supercharger. Allison had the improved "E" and "F" series engines in test but not ready for production just yet. you have choice of the Merlin with a somewhat proven track record (several thousand single speed engines built and second generation supercharger having passed tests coupled with two speed drive proven on Merlin X) compared to the promising but unproven Allison. Allison had to rework hundreds of their already delivered "C" series engines at their own expense in 1941 to bring them up to rated power. Building a factory to make "E" and "F" series engines could have been trouble free, it could also have been a disaster.
The lighter Ash-82 replaced the lighter M-105; the heavier R-2800 would replace the heavier V-1710. The intercoolers can go to to the place previously occupied by the cooler radiators.
We can also take a look at the Spitfire, that 'swallowed' far heavier engine (Griffon) without too much trouble.
I've already covered the installation of the intercoolers, so they should balance the rest of the powerplant decently.
As far as the prop goes, P-47 was using the 12,2 ft prop, 4 bladed, early on. NAA can be smart and use the system from the P-47 (extend able gear strut).
The R-2800 powered P-51 would be far less draggy than F4U, far less weight, with more internal fuel (assuming the disposition of the fixed fuel tanks as it was in 1944), it's able to carry 2 drop tanks from day one (unlike the P-47). Granted that it would be using more fuel than the real Merlin P-51, but also far less than the P-47/F4U.
Of course, but so is the 2-stage Merlin for the P-51.
2. 1-stage V-1710 for Mossie, why? Because the USA is not building Merlins, so the RAF/MAP need to do some reshufling of those. I was thinking more about the 8.80 SC ratio engines, not the really low level ones.
3. NF job is obvioulsy not for the 1-stage V-1710s. The strike fighter can use the lower weight and lower drag of the inline to make good for the loss of the ~10% of the power, and can also use the WEP (1590 HP at 4500 ft, no ram) for the, well, war emergency
4. Not really so, with the 8.80 SC ratio engines. That should do up to 15000 ft.
Obviously the British would not re-engine all of their engines, but the designs that would still been serving them good in decent numbers. Using the US engine would free up their engine production for the other designs where such a change would prove troublesome, either from the production or performance standpoint.
Substituting R-2600s for Hercules engines might be simpler. It at least solves a big part of the power problem for the 4 engine bombers and thus frees up Merlins for other uses.
You mean with Packard-built R-2600s? IIRC Beufighter was tried with R-2600 historically.
I am not sure where the far less drag is coming from.
The M-105 was actually fairly close to the V-1710 in weight. According to some sources 1268lbs. With the radials there is some shift (small) in the engines center of gravity rearward in relation to the aircraft's center of gravity. The La-5 is about 14cm shorter than a Lagg-3, not a lot but every bit helps. The La-5 was nose heavy enough that armament was limited and we don't have good details on other equipment sights or ballast.
P-51 intercooler and radiator were filled with a water/glycol mixture which weighs a lot more than airSticking the intercoolers under/behind the pilot gives you a P-47 without the turbo. You don't need the exhaust ducts but you need ducts to carry the intake air from the first stage of the supercharger to the belly mounted intercooler/s and then ducts to bring the intake air back to the engine carburetor/second stage.
Intake air inlet needs to be near the 1st stage supercharger section. Cooling air for the intercooler can be brought in from under the engine (F6F or P-47) or from under belly scope but the intercoolers for the R-2800 do not weigh anything like the radiators on the Merlin unless you design and build a air/liquid intercooler for the R-2800 instead of the air/air system that they did use.
You could use 12'2" props and extending landing gear, But every change from the Allison powered Mustang is more engineering time and more testing.
Griffon required much larger radiators behind the CG than the Merlin did which helped balance things, plus ballast.
I am not sure where the far less drag is coming from. Yes you have a smaller, lighter wing but moving the intercoolers from behind the engine to the rear/belly of the fuselage may not be a low drag option.
We know that a radial P-36 had 22% more drag than P-40 so even if the bigger diameter (and greater appetite for air) R-2800 installation only has 12-15% more drag than the Merlin that will mean a 12-15% higher fuel burn even if you can keep the R-2800 from having to operate at a rich mixture setting.
A P-51D clean can do 335mph at 25,000ft burning 59 gallons an hour. A Corsair at 21,500 ft and doing 282mph is burning 61.2gallons and hour and at 338mph at 21,500ft is burning 127 gallons an hour. It has to shift into rich mixture to hit this speed.
A P-47 at 25,000ft clean burns 95 GPH to do 300mph and 145GPH to do 337mph.
The wing is still of the laminar flow type, of smaller profile and area. The Merredith effect is still there. So the drag reduction is no problem, P-51 vs. F4U.
Some other questions: in case the RAF is really lacking the engines for their heavy bombers, how about introducing Liberator in the night bomber units (British-built heavies assume more the task of ASV, to balance this out)? Maybe the (X)B-28 gets produced, despite being only a twin? The 2-stage Packard Merlins are available for the RAF only in 1944, so the 2-stage V-1710s are used in that year?