P-40 with Griffon engine (1 Viewer)

[Elvis]

Maybe focusing on a P-40 with a R-2800 would be more realistic.

It seems that this could have been achieved at a relatively early date had not the USAAC dragged Curtiss down the paths of the Continental XIV-1430-3 inverted vee engine, British-built Merlin 28, Allison V-1710-75 engine and a General Electric B-14 turbo-supercharger, Allison V-1710-75 engine and a Wright SU-504-1 turbo-supercharger, Chrysler XIV-2220 sixteen cylinder inverted vee engine, Merlin 61, contra-rotating propellers...not sure what else I missed.

So I take it, we're looking at upgrading the P-36 now, and side-stepping the P-40 altogether?
Maybe instead of the R-2800, what about an upgraded version of the R-1820.
It's a lighter engine and would preserve the balance a little better, than the heavier R-2800.
Of course, it was originally powered by the R-1830, so the retro-fit might be more of an issue, seeing how the R-1820 is something like 8" larger diameter.
...however, the R-1820 ended up making about 1500hp before the war was over, so the effort might be worth it.

 

[Shortround6]

The time line is against it. Plenty of Hawk 75s used R-1-820s but the first real "upgrade" doesn't show up until late 1942/ early 1943 in the FM-2 Wildcat.
The 1500hp did not version show up in WWII but the 1425hp version did but not in real production numbers until 1945, late.
The 1475hp and 1525 hp versions didn't show up until the 1950s /and needed 115/145 fuel.

 

[NevadaK]

I am aware of the engine placement on the Do. 335 Wayne, but it has much more mass at the end of the rear fuselage than a plane with both props up fron2t. Not only is there the remote gearbox and the propeller assembly but also the beefing up of the tail structure to handle the torque and power of the rear propeller. You don't seriously think the tail structure wasn't much stronger than a standard tail with no propulsive power being transmitted through it, do you?

2-stage Merlin an easier install? I said that.

Wasn't talking about the XP_60, particularly the radial versions. Was talking about a revised P-40. The XP-60A or XP-60B kght be close, but still not what I ws talking about.

I said what i said about Race 2332 because the amount of fuselage in front of the wing leading edge seems to be longer than for a stock Sea Fury. That's my eye talking, not a tape measure.

Stock:
View attachment 584966
Look at the length in front of the leading edge above. Now look at Race 232 below.

View attachment 584967

Just seems a bit longer to me. Perhaps not. It's not a LOT, but also not quite the same. Perhaps in the eye of the beholder. Either way, not really a major point. They COULD have stretched a P-40 to accommodate a 2-stage Merlin without a lot of fanfare.

Look at a Vultee V-11:
View attachment 584968

Now look at the same aircraft with an Allison in it.



View attachment 584969

Now, looking at the above, I think they could stretch a P-40 by a little to accommodate any 2-stage V-12 IF the desire was there.

For the last couple of years I've been fortunate to be able to attend the Reno Air Races and see quite a few of the flight worthy sea furies in the US. From what I've seen and discussed with the crews, the Furies that have been converted to R2800's required minimal alteration and the only way to easily identify them is the number of blades and rotation of the prop. OTOH, the planes with the R4360 do appear different the easiest identifier being the scoop on top of the cowl. Here are couple links to illustrate some of the differences:

Flight testing Hawker Sea Fury T.20 'WG655'

One of the World's Most Famous Air Racers Retakes the Trophy | airspacemag.com | Air & Space Magazine

 

[GregP]

Hi NevadaK,

Reno is fun. The real issue with the R-3350 is the fact that they have run out of main bearings and it is reliable, after a fashion, as long as you run it per the WWII specs or just slightly faster than stock rpm. If you turn it much faster, it tends of be a bit fragile. But ... nowhere NEAR as fragile as the normally-reliable Bristol Centaurus when it it turned faster than spec. You might have noticed that Argonaut went from an R-3350 to an R-2800 due to the cost of replacing R-3350s on a regular basis.

Most of the WWII engines raced at Reno in other than the Bronze class are heavily modified and turn faster than stock engines. Some of the modified Merlins that turned 3,000 rpm stock are turned 200 - 600 rpm faster at Reno and survive just fine, particularly with Allison G-series rods in them. Tractor pull guys turn Allisons at 4,600 rpm, but not for long. A full pull is only some 10 - 15 seconds or less. The Bristol Centaurus was specified at 2,700 rpm and it reliable and will turn that speed all day long. But, due to the monkey-motion sleeve valve gear train, if you turn a Centaurus faster by as little as an extra 100 rpm, it tends to throw a scrap iron fit.

That does NOT make the Centaurus a bad engine. At stock power levels, it is a reliable and good-running engine that produces good power.

Here is Ellsworth Getchell's stock Sea Fury:


Runs just fine and mostly trouble-free, if you ask Ellsworth.

The Wright R-3350, on the other hand, can be turned faster than stock and runs fine right up until it turns into a hand grenade. The million-dollar question is just how fast can you turn YOUR R-3350 before it slaps your wallet with a total replacement invoice. I have heard a few answers to just how fast that might be, but the people in the know generally keep that info rather quiet because they are racers. They might tell us after they are no longer racing.

 

[Elvis]

The time line is against it. Plenty of Hawk 75s used R-1-820s but the first real "upgrade" doesn't show up until late 1942/ early 1943 in the FM-2 Wildcat.
The 1500hp did not version show up in WWII but the 1425hp version did but not in real production numbers until 1945, late.
The 1475hp and 1525 hp versions didn't show up until the 1950s /and needed 115/145 fuel.

Sorry, I thought the 1500HP version showed up during the war.
Even so, the -56 would be a step in the right direction. though.

Elvis

 

[Shortround6]

Sorry, I thought the 1500HP version showed up during the war.
Even so, the -56 would be a step in the right direction. though.

Elvis

By the time the -56 shows up you have the Allisons with 8.80 gears making 1325hp for take-off and 1580hp at 2500 ft WEP and you had P-40s with 9.60 gears making 1200hp for take-off and 1410hp at 9500ft WEP. The Cyclone doesn't offer enough power to overcome it's drag to make a decent fighter in late 1942/ early 1943.

 

[GregP]

A pretty good R-1830 fighter was the Swedish FFVS J-22. They only built 198 of them, but it was introduced in Oct 43 and performed quite well, mostly due to low weight ... gross was only 6,250 lbs (2,865 kg).

Sort of monkey-motion main landing gear, but a good-performing airplane for an R-1830.

 

[Elvis]

By the time the -56 shows up you have the Allisons with 8.80 gears making 1325hp for take-off and 1580hp at 2500 ft WEP and you had P-40s with 9.60 gears making 1200hp for take-off and 1410hp at 9500ft WEP. The Cyclone doesn't offer enough power to overcome it's drag to make a decent fighter in late 1942/ early 1943.

So we're back to the P40 again?
...Look here and go from there.

 

[Elvis]

A pretty good R-1830 fighter was the Swedish FFVS J-22. They only built 198 of them, but it was introduced in Oct 43 and performed quite well, mostly due to low weight ... gross was only 6,250 lbs (2,865 kg).

View attachment 585071

Sort of monkey-motion main landing gear, but a good-performing airplane for an R-1830.

There was a very good site, which has since been taken down, concerning the J-22.
The guy was an aeronautical engineer and actually had amassed enough info from the two-speed/two-stage version(s) of the R-1830, to see what kind of impact it would have on the performance of the airplane.
Not quite a "400 mph fighter", but darn close...and good for about 35-38,000 feet. A lot better than 15-16,000 feet.
It was a good airplane for the time it was used. Wood and fabric construction, because Sweden had lots of trees and craftsmen to shape the wood.
At the time, it was seen as a more viable option than the limited number of metal workers they had.
I think they finally retired the last of them around '52-'54.

Elvis

 

[Schweik]

Yes, that is a fairly major jump, however, didn't the propeller always stay the same?
That is; a 3 bladed prop, 9.5' in diameter.
This is my point. You can put a million HP powerplant in the plane, but if the propeller stays the same size and configuration, the plane will always handle it.
It's like that thread from many eons ago, where someone asked if the prop and engine off a P-51D were put on a P-40, wouldn't it have better performance, since the P-40 was a lighter aircraft to begin with?
There was a very long discussion about how planes and props are matched to each other, and while there is some "wiggle room", you can't go too overboard with the size of the prop (or the engine), or else the plane will be almost impossible to handle (too much to be of any practical use, anyway).
We're kind of getting into the same discussion here, but from a different angle.
Maybe what you're quoting is the fact that the prop proved efficient through those power ranges, but to try to pull more thrust by utilizing a more powerful engine and a larger prop and you're going to start incurring handling issues which might be more easily remedied by designing a whole new plane....possibly designed around (or including, as an element) the new larger prop.
I still like the idea of the bored out Allison with the single stage two speed supercharger (maybe using the bigger 12.18" impeller) and sticking with the stock prop.
Would pretty much match F/L variants, power-wise, and it would happen in a lighter and more well balanced package.
...JMHO.

They didn't have problems with the prop they had giving them sufficient power with the P-40, though I suspect with the higher power settings they could have used one with slightly fatter blades. They did that with the P-47 ('paddle blade propeller', one variant of which was made by Curtiss incidentally) and it helped climb performance quite a bit. That might have helped with the P-40 too.

P47 Heaven :: P-47 Propeller types

The main difference though I believe was that higher power settings could be maintained for longer and / or at different altitudes. Optimal altitude on an Allison P-40 was around 7,000 - 12,000 ft depending on the specific variant, and the Merlin types were something like 9,000 and 16,000. HP boost allowed them to reach that optimal power setting at lower altitudes (close to Sea Level) and with the Merlin, at a bit higher altitude. And for longer, since especially in the case of the Allisons, all that was really done was to toughen up the engine by improving the metallurgy of crank case and crank shafts and pistons so they could endure the higher power settings.

They did also sometimes run them at higher RPM, the Soviets mentioned this.

I think the improved P-40 did exist though and it was the P-40Q. Basically a long tailed P-40K or a P-40N (depending on the specific model of the 3 prototypes) with a two-stage (and water injected) Allison engine and some fairly extensive streamlining, and a bit of a plumbing change (putting radiator intake scoops in the wings, while the oil cooler remained in the nose) and toward the end of the test series, slightly clipped wings... resulting in what would have been a fast and deadly dogfighter. Curtiss got this together a bit late, and basically dropped the ball with a series of prototype crashes. That on top of all the other aggravations and failed designs they had offered up to the USAAF, and it sealed the fate of the old Warhawk series fighter.

However if Curtiss had this working & into productoin say a year to six months earlier, it probably did have a niche.

I think the woulda coulda shoulda hit right there. It could have been a Griffon or a 60 series Merlin a year or two earlier, but I'm not sure if Curtiss had the werewithal any more. Even their regular P-40Ns, which was probably their most successful design, were having build quality problems by the end of the production run. That company had just lost their Mojo. Probably the death knell was when Don Berlin left, but I'm sure he left due to the stench that was already pervading the place.

 

[Schweik]

So you think the British, having negotiated for an American supply and giving away their technological secrets (radar, jet engines) in order to access American manufacturers, would just swap out the Packards for UK built Merlins?

This makes little sense, since if they had enough Merlins to do that they didn't need Packard Merlins at all.

I'm not sure what the problem was, maybe by the time they got them they had improved production sufficiently had had later model engines available. I know that some aircraft which came from Canada were rejected due to build quality problems. I think I remember something about ailerons...

 

[Schweik]

OK, take Hawk 75 with a 1200lb experimental radial engine and replace it with a 2270lb radial (engine used in the B-26, two speed, single stage) that needed a huge propeller

While the P-60 series did wind up with R-2800 engines they also got new wings and new landing gear and by the time the R-2800s were stuffed in how much remained of the P-40 fuselage is debatable.

P-40F production as you have pointed out actually started pretty early, in 1941. P-40Q production never started, but probably the earliest they could have would have been maybe mid 1944, which is too late.

The question therefore really is, could they have gotten anything better than a P-40F / L between those dates. Say a P-40 with a 2 stage Merlin, a griffin, or a 2 stage Allison working and intro production by say, 1942 or earlyish 1943.

 

[Elvis]

They didn't have problems with the prop they had giving them sufficient power with the P-40, though I suspect with the higher power settings they could have used one with slightly fatter blades. They did that with the P-47 ('paddle blade propeller', one variant of which was made by Curtiss incidentally) and it helped climb performance quite a bit. That might have helped with the P-40 too.

P47 Heaven :: P-47 Propeller types

The main difference though I believe was that higher power settings could be maintained for longer and / or at different altitudes. Optimal altitude on an Allison P-40 was around 7,000 - 12,000 ft depending on the specific variant, and the Merlin types were something like 9,000 and 16,000. HP boost allowed them to reach that optimal power setting at lower altitudes (close to Sea Level) and with the Merlin, at a bit higher altitude. And for longer, since especially in the case of the Allisons, all that was really done was to toughen up the engine by improving the metallurgy of crank case and crank shafts and pistons so they could endure the higher power settings.

They did also sometimes run them at higher RPM, the Soviets mentioned this.

View attachment 585150

I think the improved P-40 did exist though and it was the P-40Q. Basically a long tailed P-40K or a P-40N (depending on the specific model of the 3 prototypes) with a two-stage (and water injected) Allison engine and some fairly extensive streamlining, and a bit of a plumbing change (putting radiator intake scoops in the wings, while the oil cooler remained in the nose) and toward the end of the test series, slightly clipped wings... resulting in what would have been a fast and deadly dogfighter. Curtiss got this together a bit late, and basically dropped the ball with a series of prototype crashes. That on top of all the other aggravations and failed designs they had offered up to the USAAF, and it sealed the fate of the old Warhawk series fighter.

However if Curtiss had this working & into productoin say a year to six months earlier, it probably did have a niche.

I think the woulda coulda shoulda hit right there. It could have been a Griffon or a 60 series Merlin a year or two earlier, but I'm not sure if Curtiss had the werewithal any more. Even their regular P-40Ns, which was probably their most successful design, were having build quality problems by the end of the production run. That company had just lost their Mojo. Probably the death knell was when Don Berlin left, but I'm sure he left due to the stench that was already pervading the place.

That would be XP-40Q, as it never entered service.
Here's what Wiki had to say about that part of the P-40 program....

XP-40Q : Three P-40N modified with a 4-bladed prop, cut-down rear fuselage and bubble canopy, four guns, squared-off wingtips and tail surfaces, and improved engine with two-speed supercharger. Even with these changes, its performance was not enough of an improvement to merit production when compared to the contemporary late model P-47Ds and P-51Ds pouring off production lines. The XP-40Q was, however, the fastest of the P-40 series with a top speed of 422 mph (679 km/h) as a result of the introduction of a high-altitude supercharger gear. (No P-40 model with a single-speed supercharger could even approach 400 mph (640 km/h)

...and I think they're correct.
I mean, look at the thing. It's a re-doing of the P-51D, and we already had that plane, so why would we want to re-do it?
Nice exercise in how far you can take a specific design, but I really don't see it as much more than that.
I think the P-40 works better as a low altitude interceptor, due to its better agility (compared to the P-51).
In regards to Optimal Altitude, if you're referring to the single stage Merlin, that increased working height could be a factor of a larger impeller working with a slightly smaller engine displacement....thus my earlier comments about utilizing the 12.18" impeller. Normally, the Allison used a 9.5" impeller in single stage configuration.
The Merlin normally used a 12" impeller.
Thanks for the thread on the P-47. I remember someone here calling that a "high efficiency" prop, but I cannot find any official documentation naming it such.
I swear the P-51D wore that propeller too, but I cannot find any evidence of it now......odd......
I think a more powerful engine using a propeller of that design would aid the P-40, but in a 3-bladed, 9.5' configuration.
I can't comment on the inner workings of the Curtiss company, but it sounds like you know a thing or two about it, so I will bow to your knowledge on that.

Elvis

 

[Schweik]

Fair enough - I was referring to the hypothetical production P-40Q

 

[Elvis]

Fair enough - I was referring to the hypothetical production P-40Q

Gotcha. Sorry, if my comments seemed harsh.

 

[Schweik]

Not at all! You provided a lot of good data.

 

[GregP]

Schweik, The P-51D used two different propellers. Most of the P-51D-NA Mustangs (Inglewood, CA) had Hamilton-Standard propellers and most of the P-51K-NT (Dallas, TX) Mustangs had Aeroproducts propellers. There is a dash number in the designation ,too, as I'm sure you know, such as P-51D-25-NA.

The Hamilton-Standard had a hard rubber cuff on the shank. The Aeroproducts was a very similar propeller, but without the rubber cuffs:

These are only models but the upper prop has cuffs and the Hamilton-Standard logo. The lower prop is similar but has no cuffs and has the Aeroprodcts logo. Cuffs were used to smooth out the airflow near the propeller hub or, in this case, the spinner because the hub has a nearly a round shape and creates more turbulence than useful airflow. The cuffs help top speed by a few mph (maybe 2 - 4 mph in the case of the P-51), but help cooling a lot more than that by sending better airflow into the carb intake on the Mustang or engine cooling opening if they are used on a radial engine.

Just trying to clarify, no insult intended and this is obviously not a complete aerodynamic explanation.

 

[Schweik]

No insult taken and very interesting indeed. Seems like there were a lot of incremental but beneficial things which could be done with props without a total redesign of the aircraft.

 

[Elvis]

The upper prop on Greg's models is the "high efficiency" prop I was told about many years ago.
Thanks for clearing that up, Greg.
...another view of the Hamiliton Standard...

...pic taken from Arizona Skies Meteorites website.

Elvis

 

[GregP]

Just for completeness, the early, Allison-powered P-51A's and A-36's used Curtiss Electric Propellers with 3-blades (no cuffs), as you both likely know. So did most of the P-38s and P-40s.