R-2600 powered fighter?

[Markus]

on this i want add this is true for army but not for navy the F6F was thinked for R-2600 and late change to R-2800, they thinked that with R-2600 was underpowered?

Grumman started developing the F6F in June 1941, not in 1937. And time is what this is all about. The R-2800 was still undergoing testing in ´37, the first R-2800 powered fighter did not reach the front until Jan./Feb. 1943.

 

[tomo pauk]

All were 18 cylinder radials, the first 3 used the same cylinder dimensions. ALL were by the same design bureau.

Some American engines changed about as much and yet did not change their basic designation.

Your points are valid

How do you know you are going to win and how do you know what the Germans may issue next year. 1944-45?

After Op. Bagration, along with W. Allies firmly in France Italy, with Romania Poland within artillery range, there was no reason to believe war's end is so far away. And with the newest Russian designs (Yak-3P -U, Yak-9U P, La-7 9, Tu-2, Il-10) either being produced or designed, along with US planes, VVS would have the necessary tools to fight Luftwaffe in equal terms.

And the last named engine, the ASh-73, was what they used to power the TU-4 bomber (B-29 copy)

They wanted to have something they lacked - top-notch heavy bomber. Without US license, they produced the unauthorized copy.

The US might have needed yet another factory and by the time it was ready it might not have been needed for R-2600s. I don't have the figures for the Wright but for P&W the E. Hartford plant for R-2800s starting in 1939 made 2, 17, 5431, 7696,16816, per year and finished with 3819 engines in 1945.
Ford, with ground breaking for factory in Sept 1940, made 264 engines in 1941, 6403 in 1942, 13337 in 1943, 24196 in 1944 and finished with 13437 in 1945. Factory was much enlarged twice.
Nash started with 6 engines in 1942, went to 2692 in 1943, then 9259 in 1944 and finished with 5030 in 1945.
There were also a Kansas City Plant that came online in 1944 and Chevrolet Also built R-2800s. I hope you get the idea. It took time, several years, to get a plant up and running at a decent output. Production was small in 1939-41 compared to later years.

The only field US aviation industry where they were lagging behind were fighter designs that would've competed vs. foreign designs (Spitfire, Me-109 Zero* in this case), in short, but important, time of 1939 - late 42; both in raw performance numbers produced.
In order to have such a design, one needs an engine powerful enough. The only engine offering enough power in that time frame was R-2600 - it had the power, availability reliability.
If the design powered by that engine (say, 3000 pcs for naval fighter, plus 10 000 for land-based one) would've mean that USAAC others would've received Martin A-22s, and/or more A-20s with Twin Wasps to make good 6500 planes (=13000 engines), that would be good exchange IMO. Or perhaps those bombers with Allison V-1710...

*of course, not by all accounts for those 3 designs - P-40 F4F did have many advantages over them

 

[tomo pauk]

Here is how it might have looked - F4F with R-2600, plus a comparison with Twin Wasp engined one.
The weight difference between two engines was some 800 lbs, so such 'F4F-4' would've weighted perhaps 1000-1200 lbs more (= 6760 to 6960 lbs), with 500 HP more for take off (=1700 HP); 0,208 hp/lb for real dash-4 vs. 0,251-0,244 for 'my' F4F-4. It would've still offer 1350 HP on 13 kft - Fw-190, here I come...

 

[Shortround6]

Grumman started developing the F6F in June 1941, not in 1937. And time is what this is all about. The R-2800 was still undergoing testing in ´37, the first R-2800 powered fighter did not reach the front until Jan./Feb. 1943.

Navy was ordering the F6F as a back up to the F4U, Which first flew in April/May of 1940 although with simper supercharger than used on production versions. The design competition that lead to it was opened in Feb 1938. Contract for prototype signed in June of 1938. Chance Vought, being part of United Aircraft may have had more of a "heads up" about the R-2800 than some other airframe makers ( or been told what to use by corporate?)

Without a new supercharger an R-2600 powered aircraft in 1940-41 would have been a dog at high altitude compared to the F4F. And I do mean the Wildcat. I's two stage supercharged engine delivered 1040Hp at 18,400ft military power according to some sources. The 1600hp for take-off R-2600 would have delivered about 1100hp at 18,000ft. For a mere 400lb increase in dry engine weight (the two stage superchargers did increase weight over the single stage R-1830s) plus larger propeller, cowling and all that stuff. Not to mention the higher fuel burn of the bigger engine meaning either shorter range of even more weight.

The Merlin XX is flying in combat by the fall of 1940 and offers 1120hp at 18,500ft.

All you have to do is get Wright to farm out production of it's smaller engines months if not years sooner to free up production space, develop a supercharger that Wright never used on a production engine, and then get airframe makers to modify airframe designs (some drastically) and flight test the new combinations all while they are struggling to establish production of what they already have in hand.

All for planes that offer little or no improvement in performance in the 20,000ft an up arena that had everybody worried after the BoB.

I have shown that the R-2600 only offered about 200hp more than an Allison at 18,000ft in another thread and it only cost more weight and drag to install the R-2600.

Great engine if you want a 12,000ft and under attack plane, not such a good idea if you want to fight at over 20,000ft. In-between? take your choice.

 

[tomo pauk]

Merlin XX was not available for US planes in more than token numbers, compared with original US engines.

For a (naval, but not only for those) plane to climb to the favorable altitude, it 1st has to get from carrier, while hauling it's fuel, ammo pilot, atop the empty weight. Than it has to climb to that altitude.
The R-2600 offered the power to bridge that lower altitude, plus the power to achieve greater speed at for 0 to 20000 ft, all in the right time (late 1940 on).

 

[Shortround6]

After Op. Bagration, along with W. Allies firmly in France Italy, with Romania Poland within artillery range, there was no reason to believe war's end is so far away.

Op. Bagration was in June 1944. In order to have an aircraft/engine in multi-squadron service at that time would have required planning for it to start at east a year earlier, about the time of Kursk. Did the Soviets know how much longer the war was going to last before Kursk?

If 1943 Aircraft were good enough to get the job done why did they develop later models?
Or why did they introduce new models of tanks in 1944-45 if they stopped and started to push back the Germans with the old models, which should have showed that they were good enough.

They wanted to have something they lacked - top-notch heavy bomber. Without US license, they produced the unauthorized copy.

they would have needed engines in that class for improved aircraft in any case.

If the design powered by that engine (say, 3000 pcs for naval fighter, plus 10 000 for land-based one) would've mean that USAAC others would've received Martin A-22s, and/or more A-20s with Twin Wasps to make good 6500 planes (=13000 engines), that would be good exchange IMO. Or perhaps those bombers with Allison V-1710...

2400hp bombers are not going to do the job of 3200hp bombers. The only spare Allisons you are going to have are the ones you replace with R-2600s

Production numbers for Allison.

1938..........14...........employees----512
1939..........46...........employees---1213
1940........1175..........employees---7347
1941........6433--------------------------------
1942.......15,319------------------------------
1943.......20,350

And if you "borrow" 10,000+ R-1830 engines for your scheme what airplanes that used those engines don't get built?

 

[Shortround6]

Merlin XX was not available for US planes in more than token numbers, compared with original US engines.

True but it showed what was possible, what was world class and in what direction fighter engines were going.
The R-2600 wasn't headed in that direction.

For a (naval, but not only for those) plane to climb to the favorable altitude, it 1st has to get from carrier, while hauling it's fuel, ammo pilot, atop the empty weight. Than it has to climb to that altitude.
The R-2600 offered the power to bridge that lower altitude, plus the power to achieve greater speed at for 0 to 20000 ft, all in the right time (late 1940 on).

True but not in an F4F airframe. and the speed advantage from about 17,000ft up is questionable.

All the weight change went into the nose of the aircraft. Longer, bigger tail needed?
Heavier landing gear? Wildcats had problems with their narrow track landing gear to begin with. Adding the torque reaction of the larger engine is not going to help.
Wildcats had about 8-9in of prop clearance with the tail up, not much room for a larger propeller. Unless you go to 4 blade. larger prop often means larger tail. And/or change the landing gear for clearance of a larger 3 blade?
Peace time US fighters were usually designed to an ultimate load factor of 12. Upping your normal,clean gross weight by even 800lbs means an ultimate load factor of 10.9 which might not have been acceptable without structural reinforcement (weight) to bring it back up. Foreign fighters usually made do with less but without getting into alternate specifications for your alternative history you are kind of stuck with it. It was also a good part of what made the American reputation for rugged airplanes. Lower load factors mean lighter parts for the normal flight loads but mean there is less reserve strength to handle battle damage.

Could you evolve an R-2600 powered fighter from the F4F?
Probably, but it is not going to be a straight engine swap. How many months of design and testing to get the airframe even close to right?

 

[tomo pauk]

Op. Bagration was in June 1944. In order to have an aircraft/engine in multi-squadron service at that time would have required planning for it to start at east a year earlier, about the time of Kursk. Did the Soviets know how much longer the war was going to last before Kursk?

If 1943 Aircraft were good enough to get the job done why did they develop later models?

If you read the sentence from my post, just after the part you've quoted, things would've been more clear. I''l quote that:

And with the newest Russian designs (Yak-3P -U, Yak-9U P, La-7 9, Tu-2, Il-10) either being produced or designed, along with US planes, VVS would have the necessary tools to fight Luftwaffe in equal terms.

Or why did they introduce new models of tanks in 1944-45 if they stopped and started to push back the Germans with the old models, which should have showed that they were good enough.

The tanks introduced in 1944 were designed in 1943 (IS, T-34-85)

they would have needed engines in that class for improved aircraft in any case.

Indeed, they developed AM-42, VK-108 etc.

2400hp bombers are not going to do the job of 3200hp bombers.

Some of them no, some of them yes.

The only spare Allisons you are going to have are the ones you replace with R-2600s

Deal

And if you "borrow" 10,000+ R-1830 engines for your scheme what airplanes that used those engines don't get built?

F4F used R-1830, so we can start from there.
Or perhaps we delete B-26s, so other bombers could use 10 000 surplus R-2800s. eg. TBF, SBD, A-20, B-25...

 

[tomo pauk]

True but it showed what was possible, what was world class and in what direction fighter engines were going.
The R-2600 wasn't headed in that direction.

Not because of some perceived flaw R-2600 might have, but because Wright was not tasked to develop it in 1st place. I do not suggest anyway that R-2600 was better than it (neither I'll admit it was that worse), but that it was better than many things (or best?) US have had at disposal during the 1st half of war (measured from 1st Sept '39).

True but not in an F4F airframe.

So I conclude we disagree about that

and the speed advantage from about 17,000ft up is questionable.

I'll settle with speed advantage under that height

All the weight change went into the nose of the aircraft. Longer, bigger tail needed?
Heavier landing gear? Wildcats had problems with their narrow track landing gear to begin with. Adding the torque reaction of the larger engine is not going to help.
Wildcats had about 8-9in of prop clearance with the tail up, not much room for a larger propeller. Unless you go to 4 blade. larger prop often means larger tail. And/or change the landing gear for clearance of a larger 3 blade?

Many planes were re-engined worked as Swiss clock after that. F4F was not some flimsy airframe that would succumbed under stress of heavier more powerful engine, nor the people at Grummann were incapable to tweak what is needed.

Peace time US fighters were usually designed to an ultimate load factor of 12. Upping your normal,clean gross weight by even 800lbs means an ultimate load factor of 10.9 which might not have been acceptable without structural reinforcement (weight) to bring it back up. Foreign fighters usually made do with less but without getting into alternate specifications for your alternative history you are kind of stuck with it. It was also a good part of what made the American reputation for rugged airplanes. Lower load factors mean lighter parts for the normal flight loads but mean there is less reserve strength to handle battle damage.

That's why I've contemplated with additional weight, up to 400 lbs, added to engine weight itself, and then come out with numbers about power loading

Could you evolve an R-2600 powered fighter from the F4F?

Of course.

Probably, but it is not going to be a straight engine swap. How many months of design and testing to get the airframe even close to right?

If that's 6 months, we have 1st such F4Fs delivered by March 1941.

 

[tomo pauk]

Hope this will clear some stuff - excerpt form the book about Grumman TBF (Avenger), claiming that R-2600-10 (=1900 HP for take off) was tested aboard the TBF in May 1942 - so we'd have those easily in F4Fs from mid 1943.
The excerpt claims that Wright was in position to deliver them, too:

 

[Shortround6]

If you read the sentence from my post, just after the part you've quoted, things would've been more clear.

I read it, still trying to figure out how it applies. This started with you stating that the Russians mounted the bulky M-71 on a couple of prototypes in 1941 as justification for the US mounting the bulky R-2600 in planes in 1941. The Russians never went any further than the prototypes though. You claimed it was because, in the early years they had no factory space and in later years they weren't needed because what they had in hand was (or in design) was good enough. My question is how did they know it was good enough in 1943 when production decisions for combat use in 1944-45 would have to be made.

The tanks introduced in 1944 were designed in 1943 (IS, T-34-85)

Kind of makes the point.

Indeed, they developed AM-42, VK-108 etc.

Lets see here, the AM-42 had 5 protypes built in Nov 1942. passed a 50hr factory test in Jan 1943 (I guess the factory space problem was ending?) but State tests were delayed and Mikulin relieved of his post in May. Engine finally passes state tests in April-May of 1944 and is in series production.
Strange if the M-71 was really "ready to go" in the Autumn of 1942 that more wasn't done with it considering the delays in the AM-42 program.
As for the VK-108, Prototypes built in 43-44. It took factory No. 26 in Ufa from 44-46 to build 49 prototypes and development stopped in 1947 because the bureau was overloaded with jet engine work. Not a real competitor to a 2000hp engine that had passed in tests in late 1942 is it?

F4F used R-1830, so we can start from there.
Or perhaps we delete B-26s, so other bombers could use 10 000 surplus R-2800s. eg. TBF, SBD, A-20, B-25...

And how many tens of thousands of hours of engineering drawing time and such is this going to cause, not to mention delays in production.
An R-2800 powered SBD?
well it might not have been any worse than the Helldiver

 

[Markus]

Without a new supercharger an R-2600 powered aircraft in 1940-41 would have been a dog at high altitude compared to the F4F. And I do mean the Wildcat. I's two stage supercharged engine delivered 1040Hp at 18,400ft military power according to some sources. The 1600hp for take-off R-2600 would have delivered about 1100hp at 18,000ft. For a mere 400lb increase in dry engine weight (the two stage superchargers did increase weight over the single stage R-1830s) plus larger propeller, cowling and all that stuff. Not to mention the higher fuel burn of the bigger engine meaning either shorter range of even more weight.

Would have delivered 1100hp with a single stage, two speed SC?

 

[Shortround6]

Would have delivered 1100hp with a single stage, two speed SC?

that is my estimate, yes.

 

[Shortround6]

Not because of some perceived flaw R-2600 might have, but because Wright was not tasked to develop it in 1st place. I do not suggest anyway that R-2600 was better than it (neither I'll admit it was that worse), but that it was better than many things (or best?) US have had at disposal during the 1st half of war (measured from 1st Sept '39).

Actually the R-2600 may have had some problems, Wright had only started to design their own superchargers in 1937. The few turboed R-2600s went nowhere. The Navy had placed the contract for the F6F on June 30, 1941 for an "Improved F4F" using the R-2600, a bit later than your time line but still?
Original intention was to fit the engine with least amount of change needed absorb and use the 1600hp. #1 prototype using the R-2600 with single stage 2 speed supercharger. The #2 prototype was to use a turbo supercharged version. the Grumman design team had their own ideas and what resulted was the F6F Hellcat. see:

http://steeljawscribe.com/wordpress/wp-content/uploads/xf6f-1.JPG

For the R-2600 powered XF6F-1.
by early 1942 doubts were rising about linking the Hellcat to the R-2600. development was lagging behind the P&W 2800 with 'Promised HP' of 1700 for the R-2600 and 2000hp for the R-2800. The turbo option was dropped and the #2 prototype completed with the R-2800.

Many planes were re-engined worked as Swiss clock after that. F4F was not some flimsy airframe that would succumbed under stress of heavier more powerful engine, nor the people at Grummann were incapable to tweak what is needed.

The people at Grumman were quite capable and they did "tweak" it, right into the F6F

That's why I've contemplated with additional weight, up to 400 lbs, added to engine weight itself, and then come out with numbers about power loading

You might want to look at the Spitfire when they went from the Single stage Merlin MK V to the single stage Griffon MK XII. similar increase in engine weight but not quite the same change in power. And a slightly enlarged tail. And the shortest ranged Spitfire ever until the last of the production run added wing tanks. They also had been playing with a Griffon powered prototype for quite some time before starting work on the MK XII

If that's 6 months, we have 1st such F4Fs delivered by March 1941.

Gee, not bad, considering that the first squadron standard F4F-3s aren't delivered until early Dec,1940

as far as the 1900hp R-2600 goes, that article may claim Wright was in a position to deliver them but production of the TBM with the 1900hp engine didn't start until mid 1944. I can't find the start date of the SB2C version that used the the 1900hp version.
Prototype and pre production engines don't mean you are ready to produce in quantity. When did the Napier Sabre and Bristo Centourus Pass their type tests?
THe R-2600 that ran at 1900hp for take off used a totally different cylinder construction(needing new production machinery) and possibly a different cylinder head than the 1700hp version. While you could run an early engine at the higher power level for testing it didn't cool well and needed the new cylinders for service use.

 

[tomo pauk]

Actually the R-2600 may have had some problems, Wright had only started to design their own superchargers in 1937. The few turboed R-2600s went nowhere. The Navy had placed the contract for the F6F on June 30, 1941 for an "Improved F4F" using the R-2600, a bit later than your time line but still?
Original intention was to fit the engine with least amount of change needed absorb and use the 1600hp. #1 prototype using the R-2600 with single stage 2 speed supercharger. The #2 prototype was to use a turbo supercharged version. the Grumman design team had their own ideas and what resulted was the F6F Hellcat. see:

http://steeljawscribe.com/wordpress/wp-content/uploads/xf6f-1.JPG

For the R-2600 powered XF6F-1.
by early 1942 doubts were rising about linking the Hellcat to the R-2600. development was lagging behind the P&W 2800 with 'Promised HP' of 1700 for the R-2600 and 2000hp for the R-2800. The turbo option was dropped and the #2 prototype completed with the R-2800.




The people at Grumman were quite capable and they did "tweak" it, right into the F6F

As always, very informative. Thanks

Now how about developing 'my' F4F from after F2A won the contract? It took Grumman 10 months to get the XF4F-3 in the air afrter XF4F-2 was damaged, so I guess they would've needed perhaps 18-20 months in case they give R-2600 a chance. That would be end of 1939, so USN would have their squadrons ready by Peral Harbour.

You might want to look at the Spitfire when they went from the Single stage Merlin MK V to the single stage Griffon MK XII. similar increase in engine weight but not quite the same change in power. And a slightly enlarged tail. And the shortest ranged Spitfire ever until the last of the production run added wing tanks. They also had been playing with a Griffon powered prototype for quite some time before starting work on the MK XII

I don't hold Mk.XII in such great esteem either; Mk.VIII IX were much better overall IMO
The US have had an advantage vs. UK (not only one) in pre-1943 time - they were not pressed so hard, so they have had the time to develop their stuff. Eg they ditched Spit Mk.III, because of more urgent needs.

Gee, not bad, considering that the first squadron standard F4F-3s aren't delivered until early Dec,1940

Covered above

as far as the 1900hp R-2600 goes, that article may claim Wright was in a position to deliver them but production of the TBM with the 1900hp engine didn't start until mid 1944. I can't find the start date of the SB2C version that used the the 1900hp version.
Prototype and pre production engines don't mean you are ready to produce in quantity. When did the Napier Sabre and Bristo Centourus Pass their type tests?
THe R-2600 that ran at 1900hp for take off used a totally different cylinder construction(needing new production machinery) and possibly a different cylinder head than the 1700hp version. While you could run an early engine at the higher power level for testing it didn't cool well and needed the new cylinders for service use.

Fair points, but since it says there that were testing it in may 1942, while stating they Wright was able to deliver them, then I'd say 1st production 'F4Fs' with such engines would've been available at least from mid-43.

 

[Markus]

that is my estimate, yes.

At TO the R-2600 is 450hp ahead of the V-1710 and despite a better supercharger that lead drops to a mere 200hp. Strange!

 

[Shortround6]

At TO the R-2600 is 450hp ahead of the V-1710 and despite a better supercharger that lead drops to a mere 200hp. Strange!

Why do you say the R-2600 had a better supercharger?

Supercharger being the impeller and defuser that actually compress the air.

The R-2600 may have had a better (more sophisticated) drive system for it's supercharger but that does not mean the supercharger was better.

It is also a matter of matching the supercharger to the engine and altitude. The R-2600 was set up as a low to middle altitude engine. low gear in The supercharger was set up to give peak power at about 3,000ft in the early engines. This low amount of supercharge required only a low amount of power from the engine to drive the supercharger, it heated the air less for better density and allowed the throttle to be wide open (or close to it) instead of part shut and so limited pumping losses.

Superchargers required power related to the square of their speed. The R-2600 used a gear ratio of 7.06 on most models for low gear and 10 or 10.06 for high gear and so used about double the HP to drive the blower in high gear. The Allison engines were set up (the non-turbo ones) with a 'High" gear only, 8.80 to 1.

While you can compare gear ratios on the same engine (if you know they didn't change the impeller), it is a lot harder to compare gear ratios from on engine to another.

The P-38 engines usually had lower supercharger gears 7.48s or 8.10s, that allowed more power for take-off (turbos were idling at sea level) and depended on the turbos to maintain performance at altitude.

Hopefully it is not so strange now

and as a very rough indicator of the "potential" of the two engines try multiplying the displacement times 1/2 the rpm and dividing by 1728 (converting cu in to cu ft). 2600 X 1200=3,120,000/1728=1805.5 for the R-2600 and 1710 X 1500=2,565,000/1728=1484.4.

The Allison could move 82% of the air through the engine per minute that the R-2600 could. Given equal intake pressures and so on. ( I said it was rough

Later R-2600s used higher rpm but later Allisons increase manifold pressures more than later R-2600s did.

 

[Shortround6]

Fair points, but since it says there that were testing it in may 1942, while stating they Wright was able to deliver them, then I'd say 1st production 'F4Fs' with such engines would've been available at least from mid-43.

And I suppose BMW told the German High command that they could NOT deliver reliable 801 engines in 1941-42

Considering the oh, so reliable R-3350s going into B-29s in 1944 I am less than impressed with Wrights ability to deliver engines I would like to fly behind

 

[gjs238]

As I wrote earlier, R-2600 powered Boeing 314 Clippers were criss-crossing the Pacific and Atlantic prior to 12/7/41.
R-2600 powered B-25's performed the "Doolittle Raid."
I find it hard to understand the difficulty in fielding a R-2600 powered fighter pre or early war, prior to fielding of R-2800 powered fighters.

 

[Markus]

As I wrote earlier, R-2600 powered Boeing 314 Clippers were criss-crossing the Pacific and Atlantic prior to 12/7/41.
R-2600 powered B-25's performed the "Doolittle Raid."
I find it hard to understand the difficulty in fielding a R-2600 powered fighter pre or early war, prior to fielding of R-2800 powered fighters.

The engine was designed for use at lower altitudes and only installed in planes that did not need to operate at higher ones. Hence no surprise it did not well at higher altitudes.

The R-2600 was set up as a low to middle altitude engine. low gear in The supercharger was set up to give peak power at about 3,000ft in the early engines.