R-2800 replacement for R-1830 powered Douglas TBD Devastator

Discussion in 'Aviation' started by gjs238, Apr 10, 2014.

  1. gjs238

    gjs238 Well-Known Member

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    The R-2600 powered Grumman TBF Avenger replaced the R-1830 powered Douglas TBD Devastator.

    However, on other threads it has been said that R-2600 replacements for R-1820/R-1830 powered aircraft would have been a waste of time pending R-2800 powered aircraft. The benefit of a R-2800 powered fighter would have been short-lived and would have diverted resources from R-2800 powered craft.

    So employing the retrospectroscope, would the US have been better off pursuing a R-2800 craft to replace the TBD?
     
  2. fastmongrel

    fastmongrel Well-Known Member

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    Is there any spare R2800 production capacity. Unless you use R2600 production lines for R2800 there is going to be a real shortage before 1944.
     
  3. Shortround6

    Shortround6 Well-Known Member

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    For a lot of these "what if's" please see: http://www.enginehistory.org/References/WWII Eng Production.pdf

    Now from the charts at the end ( and subject to mistake) we have production of the two engines in question all models.

    Plant.................P&W Hartford............Ford.................Wright, Patterson NJ..........Wright, Cincinnati
    engine type...........R-2800................R-2800..................R-2600..............................R-2600

    1940.....................17........................0.........................1925..................................0
    1941....................1469....................264.......................7186.................................443
    1942....................5431...................6403......................6393.................................5981

    In 1941 and until late 42 you simply don't have enough R-2800s to spread around very far.

    as to what was going to work in what. The early "A" series P&W R-2800s offered 1850hp for take-off and 1500hp at 14,000ft in high gearat a time when the Allison offered 1150hp at around 12,000ft. The Wright R-2600 was available in two flavors, the "A" series with 1600hp take off and 1400hp at 11,500ft from the Patterson plant and the "BA" series from the Cincinnati plant with 1700hp for take-off and 1450hp at 14,100ft.

    The R-2600 was actually bigger in diameter than the R-2800 by about 2in (roughly) but this resulted in a frontal area of 14.8 sq ft for the R-2800 vs 16.1 sq ft for the R-2600 ( the R-2600 was almost exactly the same diameter as the R-3350) so for a 'fighter' like the F4U the R-2800 offered more power per unit of frontal area. For a plane like the TBD the engine was nowhere near the size of the fuselage so the difference in size doesn't matter so much.
    Then look at the timing. R-2600s were flying in 1938 ( 39 built) so the Navy could "expect" the replacement for the Devastator to show up much earlier than if it used the R-2800, they also expected the Curtiss Helldiver to show up much earlier than it did but the delays had nothing to do with the engine.
    The thing is that both engines took 2 1/4 to 3 years to go from start of design to 5th production engine so the was some overlap. Neither engine in initial form offered much in the way of altitude performance without two stage superchargers (either mechanical or turbo).
    The Avenger may have been a better plane with the R-2800, you just might not have gotten ANY until sometime in 1943 unless you swiped engines from B-26 or C-46 production.

    Even radial engine factories are not easy to change over from one engine to another there were changes in casting and forging techniques between companies, changes in material (Wright R-2600BAs used steel crankcases) and differences in cooling fin machining.
    You can certainly change a factory over but it is not as simple as building R-2600s on Friday and building R-2800s on Monday. Say you could change a plant over in 2 months in 1942, that could be 800-1000 engines lost.

    Now, using the "retrospectroscope" we do know how successful the R-2800 will turn out so perhaps we can start tooling up new factories for it while it is still in the development stage and cut the R-2600 out of the picture but lets look at the Avenger again.

    This is the engine chart for the engine used in the majority of the Avengers. http://zenoswarbirdvideos.com/Images/TBF/TBFEDOLC.pdf

    max continuous power for the R-2600BA engine was 2400rpm and the Avenger can pull 1500hp max continuous to about 6000ft in low gear, in high gear it can pull 1350hp to about 13,000ft. The 1850hp "A" series R-2800 (also limited to 2600rpm max and 2400rpm Normal or max continuous) can pull 1500hp at 7500ft in low gear and 1450hp at 13,000ft in high gear. The R-2800 weighs about 300lbs more than the R-2600. How much more performance will you get out of an Avenger with 100-150 more hp at most altitudes?
    Some more is without a doubt but it doesn't seem like a game changer.
     
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  4. tomo pauk

    tomo pauk Creator of Interesting Threads

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    #4 tomo pauk, Apr 10, 2014
    Last edited: Apr 10, 2014
    Some engines can be hopefully nicked from the Lockheed Harpoon/Ventura - 6000+ R-2800s used?

    Edited it for you, gjs :)
    In case the R-2600 powered fighter is upgraded with R-2800s when those are available, then it would not be a waste of resources. Once the R-2800s are available, your production figures can hit the stride early on.
    Anyway we slice it, the R-2800 powered fighters were a non-factor before Spring of 1943, and it was Autumn of 1943 when they appeared on the carriers.

    In case the USA does not iron out the bugs from the air-launched torpedo, there would be perhaps no benefit. The 'better TBFs' would be still shot to pieces if a competent air defense is encountered. The 'slimline' torpedo bomber with R-2800 might come in handy - until the bugs are out of the torpedo, it can happily bomb stuff?

    Alternatively, the USN might specify a dive bomber with R-2800?
     
  5. RCAFson

    RCAFson Well-Known Member

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    #5 RCAFson, Apr 10, 2014
    Last edited: Apr 10, 2014
    A more developed SB2C, for example, that could replace the TBF entirely sounds tempting, but the SB2C was already overweight, so while adding a heavier engine might get you off the deck with a heavier load, it will also exacerbate the SB2Cs problems while in the dive, and actually reduce it's effectiveness as a dive bomber. AFAIK, the SB2C was the only new USN DB that could have entered service in 1942. There were some R3350 designs in the works but none showed up till 1945, IIRC.

    Hmm, actually there was the Seawolf:
    TBU/TBY Sea Wolf Info
    Budd RB Conestoga, by Jack McKillop
     
  6. gjs238

    gjs238 Well-Known Member

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    That's a good point.

    The R-2600 powered Curtiss SB2C Helldiver replaced the R-1820 powered Douglas SBD Dauntless.
     
  7. tomo pauk

    tomo pauk Creator of Interesting Threads

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    Indeed, Seawolf is the answer to the opening question.
     
  8. RCAFson

    RCAFson Well-Known Member

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    However, Seawolf is still hampered by the inability to dive bomb and the same poor torpedo.
     
  9. FLYBOYJ

    FLYBOYJ "THE GREAT GAZOO"
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    The torpedo was not the problem of the airframe manufacturer.
     
  10. Shortround6

    Shortround6 Well-Known Member

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    True but then we are using the "retrospectroscope" to full advantage. Design fighter/s for two stage R-2800 with intercoolers and install single stage R-2600 in the first few hundred (or thousand or???) until the R-2800s are ready?

    Of course you have hundreds less hp than the design really calls for and you have a bigger, bulkier plane than the the single stage R-2600 can most efficiently power.

    lets Use the F6F-3 at 8951lbs empty and lets say you save 500lbs using the R-2600 single stage engine and you can save another 400lbs between the smaller prop, smaller engine accessories, oil system etc and lets say (just to keep things simple) you can keep the CG in place by shifting equipment. You now have an empty weight of 8051lbs, a basic weight of 8973lb and a clean gross weight of 10522lbs with only 200rpg of .50 cal ammo and 182 gallons of fuel. and you have (using a R-2600BA engine, 1700hp for take-off) 1300hp of military power at 15,000ft. instead of 1600hp(?) and it rapidly diminishes to 1050hp at 22,000ft instead of the 1650hp of the F6F-3 ?
    Maybe you can come up with slightly smaller outer wings to to get weight down a bit more ;)

    Once you get above 6-7000ft I am just not seeing what advantage a R-2800 two stage sized plane has against enemy aircraft when powered by a an R-2600.

    You may be able to design a fair performing aircraft using the R-2600 single stage engine, just don't expect to put a two stage R-2800 in it later. ANd we are back to the tens (if not hundreds) of thousands of man hours spent on designing the interim fighter and it's manufacturing jigs and tooling.
     
  11. tomo pauk

    tomo pauk Creator of Interesting Threads

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    #11 tomo pauk, Apr 10, 2014
    Last edited: Apr 10, 2014
    No; design the fighter for single stage R-2600, produce several hundred (a few thousands, if we can have such a number of engines) and, once the production is under way, adapt the airframe for the R-2800.

    I'd go for a 270-280 sq ft wing, increasing the wing by some 20-30 sq ft once the two stage R-2800 is installed. Go for 4 HMGs, and 6 HMGs with R-2800s. The engine power is down vs. F6F, but so is size and weight.

    Not sure if I'm getting this right?

    But I do expect to have a two stage R-2800 on it :)

    Seawolf's designation was 'TBU' - TB is for 'torpedo bomber'. Neither TBD (Devastator) nor TBF/TBM (Avenger) were dive bombers. I've already stated that any new A/C cannot cure torpedo's problems.
    SB2C, for all of it's problems, was a dive bomber. Good one, once it was debugged.
     
  12. gjs238

    gjs238 Well-Known Member

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    That's fine, then perhaps there are aircraft like the SB2C Helldiver and TBF Avenger that could have/should have waited for more capable versions?
     
  13. GregP

    GregP Well-Known Member

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    #13 GregP, Apr 10, 2014
    Last edited: Apr 10, 2014
    If you design for the R-2600's power output, you can make a pretty decent plane from it. The TBF / TBM was pretty good and so was the B-25.

    Naturally I'd rather have something with an R-2800 in it, but that is looking from an historical perspective, not from a perspective at the time.

    The R-2600 was reliable and made decent power, which is a good place from which to start a new design.
     
  14. Shortround6

    Shortround6 Well-Known Member

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    You can't wait for the TBF. They only built 130 TBD Devastators and they closed the production line (for the 2nd time) in 1939. They only built the a small second batch to make of for attrition( crashes) and still only had about 100 in service at the time of Pearl Harbor.

    The TBF had a long and distinguished career. An extra 100-150hp wouldn't have made much difference to it's success.

    Give Curtiss the R-2800 for the SB2C Helldiver and they probably would have made just as much of a hash of it. The problems and delays in the SB2C program had very little to do with the engine and in fact work started on the SB2C before work started on the Avenger.
     
  15. RCAFson

    RCAFson Well-Known Member

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    #15 RCAFson, Apr 10, 2014
    Last edited: Apr 10, 2014
    The TBU also had a much bigger footprint than the TBF and minimum width with wings folded was 27ft versus 18ft for the TBF. This means that a given CV can carry about 2 TBUs for every 3 TBFs. Grafting the R2800 onto the TBF would have meant strengthening the airframe since the TBF was already dangerously close to it's airframe limits even with the the R2600 and the resulting aircraft, IMHO, would have been much delayed.
     
  16. pbehn

    pbehn Well-Known Member

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    Agree 100%, but for so many hit with dud torpedoes does beg a question, how come this wasnt found out sooner. A lot of lives were lost delivering duds.
     
  17. gjs238

    gjs238 Well-Known Member

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    Wasn't the issue something like "under controlled testing the torps worked fine, so it must be improper field usage that is causing malfunctions?"
     
  18. tomo pauk

    tomo pauk Creator of Interesting Threads

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    The air dropped, Mk 13 torpedo was probably best of the US torpedoes of the early ww2, reliability-wise. Its main problems were low allowable drop speed and height, forcing the A/C carrying it to slow down too much, turning those into sitting ducks. In case the A/C were above the speed altitude limits, the torpedo would display a host of problems. The speed and altitude limits were increased by mounting the wooden 'noses' that acted as air brakes, and would also receive a good deal of stress on themselves, once the torp hit the water. Also the wooden frame was attached around the tail. Another problem was the low speed of the torpedo itself, making possible for most of the targeted ships to simply turn away and run from it.
    People might want to check out this link, for an overview of this and other US ww2 torpedoes.
     
  19. FLYBOYJ

    FLYBOYJ "THE GREAT GAZOO"
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    Great link Tomo!

    Here's what Wiki says about the dreaded Mk 14

    Mark 14 torpedo - Wikipedia, the free encyclopedia

    Just for clarification once again - these weapons were manufactured by the Naval Ordinance Plant and their function (or lack thereof) had nothing to do with the aircraft manufacturer who designed aircraft to carry them.
     
  20. Shortround6

    Shortround6 Well-Known Member

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    The MK 13 avoided two of the MK 14s problems. It was never fitted with the Magnetic exploder element and its slower run and impact speed meant that it didn't suffer the crushed (dud) impact exploder element ( or at least not anywhere near as often). It did suffer from the run deep problem and the added problem of the limited drop parameters. How many torpedo drops were done at 50ft or under at 100-120 knots and while flying straight and level while being shot at?

    Until fitted with the wooden nose caps and tail fins dropping them at 100ft and 200 knts was a guaranteed miss so a faster torpedo bomber does no good on the attack run. Before and after it may be a big help though.
     
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