Why inverted V12

Discussion in 'Engines' started by tyrodtom, Sep 9, 2010.

  1. tyrodtom

    tyrodtom Well-Known Member

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    What lay behind the Germans being the only country to develope the inverted V12. The only thing I can see that the DB series and Junkers Jumo designs provide different from upright V12s is a lower thrust line. And the thrust line can be changed easier by different crank gearbox designs.
    I can't see that it doesn't improve pilot vision, the crank sump is still in the way. It seems to me the inverted design introduced difficult oil scavaging problems.

    Was their desire to develope motor cannons that fired thru the propelle hubr behind it ?
    Why, why, why ?
     
  2. tail end charlie

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    All high performance engines gave scavenging problems, the crankshaft slopping in oil eats horsepower.
    An inverted V has a lower centre of gravity which may improve the aircrafts handling.
    The crankshaft is nearer to the propellor simplifying the drive.
    or
    In a lighter vein, a Porsche has the engine in the rear, Germans see engines as verbs and dont know where to put them:lol:
     
  3. seesul

    seesul Active Member

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    #3 seesul, Sep 9, 2010
    Last edited: Sep 9, 2010
  4. BombTaxi

    BombTaxi Active Member

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    I suspect inverted V12 did give more room for a 'motor kanone', and made installation easier. If you want to mount a big gun on a plane, the fuselage is the best place for it, and putting on the centreline reduces the need for synchronisation and makes aiming easier, especially with something like a Mk108, with low m/v and the subsequent tendency for gravity to affect the round before it travels very far...
     
  5. engguy

    engguy Member

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    As far as scavenging oil, it is much simpler to do it with the engine up right rather than inverted.
    Pretty much all aircraft engines are "dry sump", that means there is no oil in a pan under the crankshaft for the crankshaft to splash in. The oil pan or sump is just a collector for the scavenge system, not a holding tank.
    I don't think it is a smart thing to do, for the simple fact that then you have the hydraulic lock problems that plauge radial engines. Funny that the merlins and Allisons worked just fine standing up right.
     
  6. Colin1

    Colin1 Active Member

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    Sorry TEC
    I'm possibly missing something really fundamental here but what do you mean?
     
  7. tail end charlie

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    Colin

    On a spitfire For example the location of the propellor is approximately in line with the cylinder heads so there is a housing/gearbox to take the drive from the bottom of the engine to the top. With the engine inverted the end of the crankshaft is approximately in line with the propellor. Im not saying that is a reason for using it inverted but its an effect.
     
  8. Colin1

    Colin1 Active Member

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    TEC
    you would see a similar housing on a Daimler-Benz powerplant, the difference being, from the point of view of installation, it would be taking the drive from the top of the engine to the bottom.

    By inverting the powerplant you are not moving anything internally, the airscrew (thrust line) will however move. Watch the .gif animations at the top of the page for the Spitfire and the Bf109.
     

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  9. tail end charlie

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    Thanks colin
     
  10. DerAdlerIstGelandet

    DerAdlerIstGelandet Der Crew Chief
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    So did the DB engines...
     
  11. Marcel

    Marcel Well-Known Member

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    I once read that an inverted V gives you better forward vision in an aircraft. Not sure if it's true.
     
  12. The Basket

    The Basket Well-Known Member

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    An inverted engine may have been more aceesible for basic maintainenece.

    Change sparking plugs and what have you.

    as they are right there and you dont have to climb.

    I think.
     
  13. Shortround6

    Shortround6 Well-Known Member

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    On the Spitfire the Propeller is not in line with the cylinder heads. The propeller shaft is in almost the same place as regards the crankshaft of either the DB series of engines or the Merlins.
    Prop shaft placement was a result of the reduction gear type and design, it has nothing to do with the engine design. P-40Ds and later used Allisons with a different reduction design than the the P-40s up through the "C" model. it changed the prop shaft location by 6 inches. P-39s put the reduction gears 10 ft from the engine.
    Radial engines used epicyclic reduction gears to keep the propshaft in line with the crankshaft as did some older V-12 engines. Some inverted aircooled V-12s even off set the propshaft to above the crankcase to allow for a gun to fire through the prop. THis did nothing for the frontal area of the engine though.:lol:

    It was claimed the inverted engine gave a better view. the cylinders form a triangle with 60 degree angles. With an upright V-12 the widest part of the triangle is closest to the pilots eyes while with the inverted engine the widest part is further away. the view over the nose directly ahead isn't much different but the view downwards along the sides of the engine should be better on the inverted engine.
    However, since cowlings don't follow the exact contours of the engine (oil tanks, coolant header tanks, cooling air for sparkplugs, engine mounts, starters, superchargers, etc) some of this theoretical advantage disappeared.
     
  14. robwkamm

    robwkamm Member

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    what about the Ranger 770. that was a inverted v. were there any problems on that one? interesting topic.
     
  15. Shortround6

    Shortround6 Well-Known Member

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    The Rangers problems's had little to do with it's being inverted. In fact the inverted arrangement allowed the cam covers to act as oil sumps and so provide a little extra cooling to heads. Prop shaft was offset to the top of the engine so as not to block airflow into the "V".

    see: File:Ranger V-770 Inverted.jpg - Wikipedia, the free encyclopedia

    A later Ranger was one of the engines I mentioned that had an even bigger offset to allow a gun to be mounted on top of the crankcase to allow for firing through the prop. That model was never massed produced.
     
  16. Milosh

    Milosh Well-Known Member

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  17. The Basket

    The Basket Well-Known Member

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    SO why did the Me-110 have inverted engines then?
     
  18. Colin1

    Colin1 Active Member

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    Presumably
    to standardise on parts and training for powerplant installations. The Bf110 was after all contemporaneous of the Bf109 which was itself designed to be cheap as chips to build and maintain.

    Other than that, I can see no cause to 'right' the engine simply because it's being fitted to another aircraft type; fitting it inverted would exploit the powerplant to the strengths it was configured for
     
  19. Shortround6

    Shortround6 Well-Known Member

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    Colin is right.
    Trying to "flip" an engine to suit different airframes would require modification and testing of both the oil system and cooling systems if nothing else. And by testing you are probably looking at hundreds of test stand hours in addition to flight testing hours.
    Since "flipping" the engine is going to bring no benefits in either power or longevity (if the engine was designed/developed properly to begin with) that is a lot of trouble and expense for no gain.
     
  20. tyrodtom

    tyrodtom Well-Known Member

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    I understand about the inverted V giving better access to the main parts of a engine that needs the most maintenence, valvetrain and sparkplugs. They might have been able to get to most of the lower engine from ground level, or just a low platform.
    It's never been in my experience with German cars that they would ever make anything easy to work on.
     
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