V-16 inline engine: pros cons?

Discussion in 'Engines' started by tomo pauk, Jun 25, 2011.

  1. tomo pauk

    tomo pauk Creator of Interesting Threads

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    Merely an invitation for a discussion about V-16 engines, both real paper projects, along with their (possible) implementation.
     
  2. marshall

    marshall Member

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    #2 marshall, Jun 25, 2011
    Last edited: Jun 25, 2011
    Two quotes from wikipedia:

    "In 1939, Chrysler was contracted by the US government to create a new engine for use in fighter aircraft. Chrysler responded by designing an inverted V16, the IV-2220. They tried many designs before choosing a hemispherical combustion chambered OHV head. The big V16 was rated at 2,500 hp (1,900 kW). It was finally tested in June 1945. It was installed in the P-47 Thunderbolt in place of a radial engine. This airplane was designated the XP47H. The change in engine and aerodynamics increased the top speed from 439 mph (707 km/h) to 504 mph (811 km/h). The war ended shortly after the tests, and the hemi V16 was never mass-produced, although the basic design and valvetrain setup live on in today's Hemi V8s."

    "Two XP-47Hs were built. They were major reworkings of existing razorback P-47Ds to accommodate a Chrysler IV-2220-11 water-cooled 16-cylinder inverted vee engine. However, such large inline engines did not prove to be especially effective."



    Anyone have some more data about this, or may verify this info?



    XP-47H

    [​IMG]
     
  3. Shortround6

    Shortround6 Well-Known Member

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    I think there is an element of hype in there, or creative license. I am not doubting the engine made the power it did or even doubting the speed but I think the valve gear on the aircraft engine used an over head camshaft and not push-rods like the car engines.
    Lots of engines used Hemi-heads including more than one US built radial engine.

    Here is a link with more pictures.
    Chrysler
     
  4. wuzak

    wuzak Well-Known Member

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    The Chrysler IV-2220 was a "hyper" engine, meaning that it was based around the cylinder design evolved by the Air Corps under Heron (?) in the late 1920s/early 1930s. That meant 2v hemi combustion chambers, and separate cylinder construction. It also meant that the engine was longer than it needed to be. The drive for the prop, cams, supercharger and accesories was all taken from the centre of the crankshaft, to reduce the problems of torsional loading.

    At 122in/3099mm it was some 40in/1016mm longer than the similar capacity and power Rolls-Royce Griffon, and some 400lb/181kg heavier. The weight was also slightly more than the 24 cylinder Sabre, which was more power and similarly 40in/1016mm shorter than the Chrysler. The small frontal area was a positive, but when they put the engine in a P-47 with its deep fuselage the advantage was cancelled somewhat.

    The Daimler Benz DB609 was a V16 based on the cylinders of a 603. It had much larger cylinders, but with the bore spacing closer and the reduction drive off the end of the crank its length was shorter. The DB609 was heavier, but it also had 60% more capacity than the IV-2220.

    I'd suggest that the small frontal cross section of the V16 is offset by the excessive length of the engine. For a 16 cylinder engine I'd suggest an X or H layout, but then I would probably also suggest going to 24 cylinders.
     
  5. wuzak

    wuzak Well-Known Member

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    In regards to the DB609 it gained no benefit in frontal area over the DB603, but gained capacity and power at the expense of weight an a lengthy, troublesome, crankshaft.
     
  6. davebender

    davebender Well-Known Member

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    DB603. 2,610.5mm length. 920kg weight.
    DB609. 2,935mm length. 1,400kg weight.

    The DB609 V16 is remarkably short compared to the DB603 V12. Did placing the cylinders so close together cause overheating?
     
  7. wuzak

    wuzak Well-Known Member

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    Probably didn't run long enough to overheat before the crankshaft broke....

    I'd say the bore spacing was probably the same as the DB603. The difference is 325mm, the bore of the DB603/609 is 162mm, so 2 more cylinders would add 324mm. I think that some savings were made in the length of the accesories section. (Looking at the Chrysler IV-2220 the accesories section is really long.)
     
  8. davebender

    davebender Well-Known Member

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    Plus the cylinder wall thickness. So DB609 cylinders must have been closer together then DB603 cylinders. Which leaves less room for coolant passages in the cylinder heads to carry away heat.

    With an engine as short as the DB609 I don't understand why a properly designed crankshaft would break. Some other WWII era piston engines probably had longer crankshafts.
     
  9. Shortround6

    Shortround6 Well-Known Member

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    A properly designed crankshaft won't break. But a properly designed crankshaft and crankcase will be heavier for a V-16 of the same power than a V-12 engine. granted you may get more power from a larger displacement V-16 but it's power to weight ratio will be lower than the smaller V-12.
     
  10. davebender

    davebender Well-Known Member

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    Might be a good powerplant for a mid engine design. Then you wouldn't need an exceptionally long tail section to balance a heavy engine in the nose.

    Such an aircraft could have the prop in back rather then in front (i.e. similiar to Do-335 rear prop). That leaves the nose free for four 20mm cannon, all firing on the centerline.
     
  11. Shortround6

    Shortround6 Well-Known Member

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    You now have a heavier than needed engine, with the extra weight of the of the extension shaft, plus the extra weight of a fuselage rigid enough to keep the prop in line ( 1 degree of deflection over 10 ft is 1 inch.) while pulling high G maneuvers, plus the weight of landing gear long enough to keep the prop from hitting the ground.
    Now maybe by mounting the guns in the fuselage you can save structural weight over mounting them in the wings but it is going to take clever engineering and a lot of work to come out ahead of the tractor airplane.
     
  12. davebender

    davebender Well-Known Member

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    Nose mounted guns are far more effective then wing mounted guns as you don't need to worry about convergence and wing flexing throwing off your aim. That's the main reason I would consider a rear prop over a tractor prop.
     
  13. wuzak

    wuzak Well-Known Member

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    The DB6099 is not short at all....it's nearly 3m long!

    They did experience problems with the DB609 crankshaft from what I gather.

    I also said that the length savings of the DB609 would likely be in the accesories section. I doubt that the cylinder spacing was different to the DB603.
     
  14. billswagger

    billswagger Member

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    I read the advantage of the V16 was the piston cranks didn't require counter balancing because there was an opposing cylinder in place.

    Aside from saving weight, wouldn't that also help the crankshaft?

    The issue with the V16 i see is that in order to achieve that, it would require a V angle of 135 degrees which makes implementation into an existing fighter difficult since most fighters were designed around a 60 degree V engine.
    It would open up space in the middle of the engine for things like cooling or supercharging, but you'd need a wider nose.

    Bill
     
  15. Shortround6

    Shortround6 Well-Known Member

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    The opposing cylinder trick doesn't work until you get to 180 degrees or close to it. it also doesn't work unless you have a separate crank throw for each cylinder. with a common crank pin both pistons are moving to the left or the right at the same time.

    The best angle for a V-16 is 45 degrees. take 720 degrees of crankshaft rotation and divide by the number of cylinders to get an even firing pattern. Other firing intervals can be made to work but it is why V-12s usually are 60 degrees and V-8s are 90 degrees.

    Of course 45 degrees doesn't leave much room in the V. 90 degrees will work but you have two cylinders firing at the same time. or two cylinders firing 30 degrees apart and then a then a 60 degree gap then 30 and then 60. It works better in slow turning engines or low power to weight ratio engines or can be tolerated for other reasons.
    Aircraft engines have to be built light for their power and even with vibration damping mountings the rest of the airframe can suffer from engine vibrations.
     
  16. davebender

    davebender Well-Known Member

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    I agree. But DB609 power to weight ratio doesn't look all that bad.

    DB609. 1,400kg. 2,660 hp. 1.9 hp per kg.
    BMW801D. 1,012kg. 1,677 hp. 1.66 hp per kg.

    BTW, how is radial engine power measured? Is the BMW801 power net, after subtracting power required to run the cooling fan?
     
  17. Readie

    Readie Well-Known Member

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    I have reading this thread and vowed not to mention the M word....
    Its hard
    Very hard

    Nooooooooooo :oops:

    Oh, ok then...

    Merlin :shock:
     
  18. Piper106

    Piper106 Member

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    #18 Piper106, Jun 27, 2011
    Last edited: Jun 27, 2011
    Well Chrysler had it part right and part wrong.
    The idea of putting the propeller reduction gears in the center of the engine was a good one. This made it basically two V-8s end to end but isolated from each other, eliminating a lot of the crankshaft flex, torsion wind-up, and vibration.
    The accessory section was not so good, far too long. Look at how little the accessory section extends beyond the cylinder banks on the RR Merlin and Griffon and then look at the Chrysler. Not packaged well at all.

    Piper106
     
  19. Piper106

    Piper106 Member

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    Replay of an earlier thread from the engine section of this board.

    Opportunity lost - DB 16 cyl
    It is historic fact that Damlier Benz worked on a 16 cylinder development of the DB603 line of engines under the DB609 type number. Development of this engine was abandonned in April of 1943.

    From what little I have been able to find out, it was a conventional V16 design with a crankshaft that was 8 throws long, and the propeller reduction gear at the end of the engine. My guess is that torsional vibration and twisting of such a long heavily loaded carnkshaft was a major difficultly, and that correcting crankshaft problems was beyond the ability of the Damlier Benz engineers and technicians.

    But what if DB had built the engine like the Chrysler IV-2220?? Use the pistons, rods, valves, etc. from a DB603 to build a 162 mm bore x 180 mm stroke sixteen cylinder engine as essentually two V-8s end to end with the propeller reduction gears in the center of the engine. Now there are two short stiff crankshaft segments, and a the two crank segments could have been isolated from each other with a vibration damper or quill shaft. I estimate that the weight of such an engine with a single stage supercharger would have been around 2700 pounds (1230 kg).

    This likely would have given the German airforce a reliable alternate to the Jumo 222 on a timely basis.
    Maybe this could have been the 2500 HP engine that they needed for later versions of the He 219, Ju 388, etc. and the Bomber B projects.

    That is all I think i know.
    Piper106
     
  20. wuzak

    wuzak Well-Known Member

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    I think it could be argued that the DB604 X24 with 135mm x 135mm cylinders was a better bet, paricularly where the engine was to be interchangeable with the BMW801 in bomber designs. It had around the same power as the DB609 and was lighter in weight, shorter in length, though probably taller and wider.
     
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