No (or too late) R-2800: plausible developments?

Discussion in 'Aviation' started by tomo pauk, Sep 28, 2012.

  1. tomo pauk

    tomo pauk Creator of Interesting Threads

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    Another time line: for the sake of discussion, and no matter how unlikely, lets say that P&W manages to drop the ball while developing their R-2800. Say, engine reaches production in second half of 1944. What would be the plausible developments in the field of airplane production/deployment/performance, for all the historical users of the planes powered by that engine. Instead of R-2800, USA builds more Allisons, R-2600s, R-1830s, maybe Packard Merlins.
     
  2. gjs238

    gjs238 Well-Known Member

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    F4U was built around the R-2800.
    Would no R-2800 mean no F4U, or maybe F4U built around something else?
    F6F was originally built around the R-2600.

    So maybe that's the answer, what has been deemed impossible by some here, a R-2600 powered fighter, would actually happen.

    On the other hand, perhaps there is more support for developing the Allison V-3420.
     
  3. GregP

    GregP Well-Known Member

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    If the R-2800 had not been developed a possible alternative might be either the R-2600 or the R-3350. The R-2600 could have been developed into a 2,000 HP engine with sufficient push. It might have needed to increase displacement or maybe boosted more, but it could have been done.

    The R-3350 turned intoa VERY reliable airlijne engine AFTER the war but, during the war, it had issues. If we had needed it instead of the R-2800, the issues might have been insurmountable or might have been worked out sooner ... I couldn't say which.
     
  4. Shortround6

    Shortround6 Well-Known Member

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    You cannot replace a 2800 cu in engine with a 1830 cu in unless you use two. and using two 1500lb engines to replace one 2300-2400lb engine poses some obvious problems in performance. The R-1830 is out.

    Same with the Allison. you need to use two Allisons for every R-2800.

    Almost the same with Merlins. For bombers you need take-off power to get off the runway and you need CRUISE power. You need 2 stage Merlins to have a even have a hope of replacing R-2800s.

    That rather leaves the R-2600. Wrights record of "improving" the R-2600 is not the best and it has a few fundamental problems compared to the R-2800. It used fewer but larger cylinders. The scope for "enlarging" the engine without adding more cylinders was somewhat limited. It already had 8mm more stroke than the R-2800 which means it has a whisker more piston speed at 2500rpm than the R-2800 does at 2600rpm. Increasing the stoke means a higher piston speed at any rpm. It is possible but needs a lot of work. It is complicated by the large size of the bore. 9 mm more than the R-2800. Large bore cylinders are harder to cool. Less surface area per unit of volume. Bore size also affects RPM. The speed at which the fuel burns is almost a constant. That is to say after the spark plug/s ignite the fuel the flame front/s in the cylinder advance at about the same speed. A larger cylinder needs more time for the flame front/s to advance across the cylinder. Ideally the fuel should be burned by the time the piston reaches 20 degrees after top dead center. Now this can vary a bit ( although power may not fall off much fuel economy might) and be a bit longer. Spark plug placement and exact ignition timing can help. Please remember that many WW II aircraft engines used fixed ignition timing and not variable like cars.
    A large 14 cylinder needs more development to reach the same power levels as a same sized 18 cylinder engine.
     
  5. wuzak

    wuzak Well-Known Member

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    Merlins and Allisons probably don't require as large an aircraft built around them.

    If the R-2800 is going to be delayed then I expect that the XP-47, built around the V-1710, continues and the XP-47B is not evolved.

    The V-3420 can just about fit in the space required for an R-2600/R-3350, except in length, so will only be slightly bigger than the R-2800 (albeit a different shape).

    Supply of the R-2600 would be difficult - I suppose you'd be building it in factories where the R-2800 would otherwise be. You'd be supplying it to the B-25, B-26, A-20, A-26 (maybe the R-2800 is ready by then), F6F, F4U, P-47 (maybe?), C-46 and, probably, many others I haven't mentioned.
     
  6. tomo pauk

    tomo pauk Creator of Interesting Threads

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    I don't want to replace the R-2800 with R-1830, nor with V-1710. I'm after the assesments about the planes that would be produced (or produced in larger numbers), with R-2800 being as good as unavailable until second half of 1944. Eg, the P-47B is out of the question, so the USA bulids more P-38s, while adopting the P-51 earlier. Martin builds the B-26 around aome other engine (or licence builds B-25s?).The USN has to procure something instead of historical F4U and F6F. Etc.
     
  7. Shortround6

    Shortround6 Well-Known Member

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    The R-2800 was the 3rd most produced major aircraft engine by the US until the end of 1944. With it un-available the repercussions and changes in US engine manufacture and types of aircraft produced go into multiple scenarios. Ford starts production in 1941, Nash-Kelvinator starts at the end of 1942. Both P&W Kansas City and Chevrolet start up in 1944. Certainly these plants can be built to make other engines but once tooled up and running they are pretty much committed to that original engine. No switching an R-1930 Factory to Merlins or Allisons at a later date. With P&W out of the picture ( or at least the R-2800) how much pressure is there to produced "tried and true" but low powered engines compared to building higher powered engines that never made it? Like the tooling up of the Continental plant for the IV-1430? Would the Army have pushed this turkey or the Lycoming H-2470 ?
    How many P-60s would have been made?
     
  8. tomo pauk

    tomo pauk Creator of Interesting Threads

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    As I've already stated, the USA can (must?) produce other engines it sees fit to suit it's needs. So Nash-Kelvinator might start with Merlins, while Ford builds, say, R-2600 (needed for the license produced B-25s by Martin?). The pressure and funding can go towards V-3420s and R-3350s.

    The airplane production alteration (intended as the main topic of this thread) is easier to do for the USAAF, than for the USN. I've already mentioned increased attention to P-38 -51, as well as B-25. The P-60 (turbo V-1710) is maybe an easier task for Curtiss, than it was P-47G? Also, the P-63 gets deployed in Europe? Republic re-engine their P-43 with V-1710? Or start with 4/5s of an Thunderbolt, featuring R-2600 and 6 HMGs?

    USN has to either adopt R-2600 as a fighter engine (2-stage, or turbo maybe?) , and/or to adopt liquid cooled powerplants, if not the whole planes. So they adopt the Airabonitas? The P-51D was not a very acclaimed for it's CV capabilities, so maybe an increase in wing area, along with deletion of the hull fuel tank might help? A Packard Merlin in the F4F? Historically, however, by the time numerous R-2800s start roaring over USN's CV decks, the IJN was not anymore as a formidable opponent as it was once.
     
  9. Shortround6

    Shortround6 Well-Known Member

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    There are too many "what if's".
    There were proposed or experimental 2 stage and turbo R-2600s. Numbers actually flown were in the single digits. Wright spent millions of dollars and teens of thousands of hours on the R-2160 Tornado. Wright also essentially redesigned the entireR-3350 from what it had been in 1938-40 to what it was in 1942-44.

    We don't know how successful the R-2600 would have been with either a 2 stage or turbo, or how unsuccessful. We know the R-2160 Tornado was a flop but would more time and money have been spent on this rat hole? Even with the redesign the R-3350 was far, far from being trouble free until almost the end of the war. Perhaps a non-turbo derated version would have done better? But how much derated?

    Part of the impact of the R-2800 was that it allowed some of the more exotic engines to be dropped from consideration/production.

    Please note too that very few licence engine builders built more than one type of engine. Buick built over 60,000 engines but they were ALL Single stage R-1830s. Ford Built ALL single stage R-2800s and Nash built ALL two stage R-2800s. Studebaker Built over 57,000 R-1820s by the end of 1944 ot just under 62% of the R-1820s built between 1939 and 1944. Studebaker doesn't role out the first engine until Feb of 1942. Studebaker had been brought into the aircraft engine production system in Nov of 1940 but ti's intitial contracts to make R-2600s were changed to the R-1820 in June of 1941 before a single R-2600 was built. Studebaker was considered to be able to change engine types better than Wright itself.

    Sorry to stay on the engines but without sorting the engines the airframe questions takes off in too many directions. The Curtiss P-60 is behind the P-47 in timing. The first prototypes of the XP-53 are not ordered until a number of weeks after the first 773 P-47s are ordered. Performance numbers for the XP-53 are looking a bit dubious. The Air Corp was also specifying some rather unrealistic armament set ups. First P-60 (out of a 1300 plane order) with a Merlin Single stage engine was expected to be delivered in July of 1942. However prototypes failed to make guaranteed speed and revised estimates of performance with version with the turbo Allison showed a need for at least 1500hp.
    They were even planning versions using the Chrysler IV-2200 16 cylinder at one point.
    The Airabonita was a lost cause. Sower than expected with a higher landing speed, bad handling/stability.

    The P-51 isn't going offer much help early in the war. Even if a second factory is planed for starting at the end of 1940 it won't start producing until the middle of 1942 if not later and that is with Allison engines.
    Changing wings isn't as easy as it looks. A few sq ft is one thing, 40-60 sq ft is another on a fighter. New spars and so on are needed, a complete re-engineering of the wing.
     
  10. tomo pauk

    tomo pauk Creator of Interesting Threads

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    #10 tomo pauk, Sep 30, 2012
    Last edited: Sep 30, 2012
     
  11. Shortround6

    Shortround6 Well-Known Member

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    "Supermarine can do it, so can Messerschmitt. NAA?"

    Look again at the Spitfire, they changed the wing tips. All changes were from the rib at the end of the ailerons outward. Standard wing was 242 sq ft, "clipped" (wingtips left off and opening covered with a fairing) was 231 sq ft, the "extended" wing was a longer, pointier wing tip. and added 3 1/4 sq ft (0.3 sq meter) to each wing. Try adding 2-3 sq meters to each wing.

    "The V-1650-1 was a fine engine, but it was not that a stellar performer for jobs above 20000 ft. The 1425 HP from turbo V-1710 were available also at 25000 ft, where the single stage Merlin was delivering some half of that; even the exhaust thrust won't help against that kind of deficit in power."

    While the Merlin III might have been that bad the Merlin XX (V-1650-1) wasn't. Tests of a Hurricane II (with less level speed ram than a Spitfire) give a brake HP of 1073 at 20,000ft with 48.24 in boost. 1126hp at 20,000ft with 50.67 in boost, 960hp at 25,000ft at 42.12 in boost, 778hp at 30,000ft with 34.30 in boost. to which can be added 113 ejector HP, 126.8 ejector HP 107.2 and 89.0 ejector HP at the boost and altitudes given. More like the Merlin is giving 75% of the turbo Allison at 25,000ft counting the exhaust thrust. A faster plane than the Hurricane II could get a bit more Ram effect and a bit more ejector HP.

    A lot of Curtiss performance projections turned out to be rather wide of the mark when the planes were actually tested.

    The rare R-2600s are really rare. One A-20 (or more?) is supposed to have flown with Turbo R-2600s. A two stage mechanical version was planed for the Navy. The question is how far they got or if they ever flew. Please note that P&W had one B-23 bomber (normal had R-2600s) that they fitted several different versions of R-2800s to for testing, one test even included contra rotating propellers. R-2600 with two stage supercharger IF it ever flew might have been in a test bed bed aircraft and not a service type.
    P&W lists a lot of models for the R-2800 that were never "manufactured" or built.
     
  12. tomo pauk

    tomo pauk Creator of Interesting Threads

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    I was referring to the navalisation of the ground fighters, that became Seafire III and Bf-109T. The wings received, in these examples, significant changes.

    Thanks (time and again) for the effort to locate, calculate and type the data, I stand corrected re. ratio of HP available. The less draggier plane should have maybe 80% of the power of the turbo V-1710 at 25000 ft, and some 65-70% at 30000 ft?
    The Merlin XX would have far less of the power deficit while climbing, where both ram effect and exhaust thrust are almost of no use.

    Agreed. The real data about the XP-60A is rather difficult to dig, other from few lines at Whitney's book (that also being estimates?).
    Darn shame that P-51/Mustang was not flying with V-1650-1 from day one.

    Hellcat's prototype - flying with a prototype of the two stage R-2600?
     
  13. ShVAK

    ShVAK Member

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    I'd say focus on the R-3350 Duplex-Cyclone and smoothing out its problems. First run was in '37, about the same time as the P&W. With several aircraft on the table potentially designed around it instead of just the radical B-29 design it would've taken higher priority.

    Once direct injection was implemented it was every bit the equal of the R-2800 or even better. Plus they sound awesome, IMO.
     
  14. Shortround6

    Shortround6 Well-Known Member

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    #14 Shortround6, Oct 2, 2012
    Last edited: Oct 2, 2012
    There were aircraft designed for it. The Curtiss XP-62 and XF14C-2 fighters, Curtiss XSB3C-1, Douglas XSB2D-1 and more.

    It used 9 R-2600 cylinder per row rather than seven, what could go wrong? :) :)

    Give the Army and Navy a 2200hp engine in 1940 and they will do just what the did they then. Demand pressure cabins, twelve .50 cal guns in the wings or eight 20mm cannon and other performance robbing "features".

    Planes designed for the R-3350 tended to make the ones powered by R-2800s look anorexic. Hard to do to a P-47 but they managed.

    edit> Other aircraft using the R-3350 include the B-32 bomber and the Lockheed Constellation transport.
     
  15. stona

    stona Well-Known Member

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    The only changes to the wings of the Seafire III were associated with the need to fold them. They really weren't great considering. The hinge mechanism and fairing to cover the gaps in the fold line at the hinges in the upper surface. Some nice felt pads at the join in the gun heating ducts to avoid heat loss and that's about it.

    Steve
     
  16. Shortround6

    Shortround6 Well-Known Member

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    A lot of things CAN be done. The question is SHOULD they be done. How many man hours in engineering time gets sucked up for what benefit. Engineering time includes draftsmen sitting at tables "just" doing the drawings. Packard spent tens of thousands of hours redoing the Merlin drawings for American standards. It was worth it. The Spitfire wing tips could be changed with comparatively little engineering work. Practically and Spitfire wing (until you get to the very late ones) could be changed from one to the other in the field, changes in forces acting on the wing were small. Changing wings by 20-25% in area requires changes in structure. You have changed the spanwise lift loading and bending characteristics of the wing.
    It CAN be done but it requires time and testing. It is not quick and easy.


    I think you mean more of a power deficit while climbing and you are right, but then the Merlin is lighter than a turbo Allison. Advantage does stay with the Allison as long as the US doesn't bugger up the design with too many guns and too much ammunition.


    You are right but the engine was changed to a R-2800 in Sept. First flight was on June 26 with the second prototype ( first with R-2800 flying 4 days later), I have no idea how much flying was actually done. Sources differ but one or both prototypes flew with single stage R-2800-27s at some point in their lives. Starting in Oct of 1942. Results of those flight tests would be interesting :)

    I believe if the R-2800 had crapped out or been delayed a number of years the US would not have stayed just with the other historical mass produced engines but tried to bring one or more of the experimental ones into the production program. I have no idea how well or badly that would have gone. Wright apparently had quite a bit of trouble with the R-2600 as it was or at least production and quality control at one plant.
     
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