DB 630

Discussion in 'Engines' started by SpicyJuan11, Jun 12, 2015.

  1. SpicyJuan11

    SpicyJuan11 Member

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    Hello, does anyone have any info on the DB 630? Specifically, how did it compare to te BMW 802? This is all I have:

    Any help would be greatly appreciated, thank you!
     
  2. WJPearce

    WJPearce Active Member

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    Engine project with six banks of six cylinders. The 100 degree bank angles were on the top and bottom. 4,000 hp (or 3,900 hp) at 3,200 rpm. 11,000 m (or 12,000 m) full throttle height. 142 mm bore and 155 mm stroke, which works out to 88.37 L displacement (but some sources say 89 L). 8.3/8.5 compression ratio. 3.0 m long, 1.4 m wide, and 1,750 kg.

    May have been planned to have a two-stage turbocharger and a three-stage, three-speed supercharger.
     
  3. SpicyJuan11

    SpicyJuan11 Member

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    Again, thank you for the great information WJPearce! So would it have been better to develope it instead of the 2 stage 3 speed BMW 802, or to develope them both?
     
  4. Shortround6

    Shortround6 Well-Known Member

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    forget them both and build engines they could really use.

    Of course a few other nations went down the same road.

    redpaul.jpg

    Lycoming XR-7755. The got to 5000hp before the project was canceled.

    "The huge engine was 10 feet long, 5 feet in diameter and weighed 6,050 pounds. It produced 5,000 hp at 2,600 rpm, and the target was 7,000 hp. It used 580 gph of aviation gas at the 5,000 hp rating."

    From Lycoming XR-7755

    and Bigoldengines
     
  5. SpicyJuan11

    SpicyJuan11 Member

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    Like jets?
     
  6. WJPearce

    WJPearce Active Member

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    I don't mean to get to crazy here, but this is where things get a little murky. Sitting here in 2015 we can easily say it was all a waste of time and these companies should have looked to inventing microwave ovens or cell phones or WiFi, because that technology is applicable to our daily lives and ridiculously huge reciprocating aircraft engines are not. But, sitting in 1941, perhaps with little to no knowledge of turbine engines for aircraft, ridiculously huge reciprocating aircraft engines seemed like a good idea. The same thing happened after WWI with the Duesenberg H, Sunbeam Sikh, Napier Cub, Beardmore Cyclone/Typhoon, Argus As 5, Allison X-4520, etc. While none of those were successful, I'm sure some of what was learned was applied to future aircraft engines (at least what NOT to do).

    On paper, the DB 630 looks to have the edge over the BMW 802; it is more powerful for about the same size and weight. But, the DB 630 only existed on paper while the BMW 802 was built and run. Who knows what technical difficulties awaited the more complex DB 630 to either delay its development or make it impossible.

    When it takes 10 years to develop a new large aircraft engine, I think the designers and engineers try to forecast what will be needed then, because it is too late to design something new for what is needed now. So, I completely agree with Shortround, but almost every industrial country chased the ridiculously huge reciprocating aircraft engines concept for the next generation of ridiculously huge aircraft. I think that is simply because they did not see the turbine engine 10 years out.

    Below is a list of ridiculously huge reciprocating aircraft engines that were built, with the exception of the Studebaker and GEHL. Other huge engines like the DB 630, Allison DV-6840, and Nakajima Ha 54 either stayed on paper or did not get much into the making parts phase.

    I think we all should be very glad turbine engines came along when they did.

    Large Engines.JPG
     
  7. johnbr

    johnbr Well-Known Member

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    #7 johnbr, Jun 13, 2015
    Last edited: Jun 13, 2015
    Don't for get the Daimier-Benz 604c-d and the Db-h24 both where 4000hp on the h-24 db did make a h-16 of 2000hp it said.
    DVL H 32
    rev/min 3500
    Hp 3750
    litres 66.5

    DB X24/604c
    Hp 4200
    Rev/min 3000
    litres 50
     

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  8. Shortround6

    Shortround6 Well-Known Member

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    You have several practical problems with huge engines. One is that the Market for them winds up being on the small side. You need a fighter the size of an F4U or P-47 to handle even the P W R-4360. How big a single engine fighter do you need to hold a 3 ton engine? The same sort of holds true for twins. Pre war twins were often under powered form a safe fight point of view. A number of Pre-war and early war bombers could not maintain height on one engine even with the bombs gone. THings got better with more powerful engines but a with these monsters there was a risk of going backwards in the sense of using two 5000 hp engines vs four 2500hp engines to power a large plane. If the 4 engine plane looses and engine it is still in pretty good shape, if it looses one on each side it may still go a pretty fair distance to land. The really big twin loosing an engine is in serious trouble. 1/2 power and a powerful asymmetric thrust requiring drag producing "trim" on the controls. A small but high powered twin may have surplus power but the weight and fuel consumption of these engines tends to go against a small twin. yes you could have 7-10,000hp using engines in the upper part of the list but you also have 4-6 tons of engine weight, some really big propellers and the ability to suck up 15-20 gallons of full a minute at full power. You aren't going to stick a pair of these things in a Mosquito sized airplane or even an A-26.

    The monsters only make sense on planes that will require 4 or more of them and those are very large aircraft indeed. And as such are not likely to be built in large numbers.

    The next problem is transmitting that kind of power. You not only need the engine but you need to push propeller technology and reduction gear box technology to their limits to get the big engines to work (you also need big landing gear to get the props high enough off the ground. :)

    Getting serious again, most everybody vastly under estimated the difficulties in building and running these large engines. We have the benefit of hindsight from 2015 but just as an example, P W used many more test engines and spent about 5 times the money IIRR on developing the R-4360 than they did the R-2800. The problems seemed to rise exponentially with the number of cylinders.
     
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  9. SpicyJuan11

    SpicyJuan11 Member

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    Interesting, thanks.
     
  10. GregP

    GregP Well-Known Member

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    #10 GregP, Jun 14, 2015
    Last edited: Jun 14, 2015
    I read a bit about the Lycoming XR-7755 and the chief designer made a statement that has always stuck with me. He said that while you could built larger engine, they weren't going to get any better than about 5,000 HP on petrolium fuel for aircraft use since the weight and frictional losses would overcome any power output gains after that size and output had been achieved.

    Seems he was at least mostly correct. The Russians DID make a bigger radial engine, the Zvezda M503. It is a 7-row radial of 6 cylinders each, but it is used for tractor pulls, not aircraft propulsion.

    Niheq.jpg

    Early models had 4,000 HP and developed power is 6,035 HP. But at 8,378 pounds (3,800 kg). you aren't going to fly it anywhere.

    The biggest engine of which I am currently aware is the Wartzila-Sulzer 14-cylinder Marine engine. It developes 108,920 HP at 102 rpm ... that's really 102 rpm. and weighs 4,600,000 pounds (2,086,514 kg).

    T4AXHT8.jpg

    Here is a pic under xconstruction with a man in the pic for scale.

    eYBusHj.jpg

    I'd say you aren't going to fly it anywhere, either. Since it weighs 4,600,000 pounds I won't bother to estimate the size and weight of the radiator that might be required ...
     
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