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  #31  
Old 21st November 2018, 17:55
schwarze-man schwarze-man is online now
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Re: Bf 109 vs. Spitfire production costs

Quote:
Originally Posted by Kutscha View Post
The workmanship, or the lack there of, of late war 109s reflected the decrease in assembly times.

Late war C3 had gumming problems if the fuel sat too long. Did Allied 150 fuel have this problem?

Hi Kutscha!
I believe (very generally as fuel chemistry is complex!), the B4 fuel was very low in aromatic content whereas the C3 had higher levels of aromatics. Generally, the Higher grades of Allied fuels also had higher levels of aromatic content that could attack some of the rubber in fuel system components. Also, levels of poisonous TEL and other compounds were very high in 150 fuel. I know that Avgas (100/130) is still monitored for levels of dissolved "gum" to ensure it is not contaminated. Cheers

SM
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  #32  
Old 22nd November 2018, 01:57
Kutscha Kutscha is offline
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Re: Bf 109 vs. Spitfire production costs

Thank you. What I understood from what was written in the old post on another board, it was not the 'rubber' that caused the gumming but the fuel itself degraded.
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  #33  
Old 22nd November 2018, 10:43
schwarze-man schwarze-man is online now
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Re: Bf 109 vs. Spitfire production costs

Hi Jukka!
Were the details I posted at reply #30 interesting to you? Do you have an interest in the Cam timing specifically? I would be very interested if you have any other details of this. As you will know, the details of the DB605A are now completely known. However, the later engines are still hiding many of their secrets. There is enough information to operate the DB605D. I have worked on the 605D that flys with the Messerschmitt team, previously owned by Hans Dittes.
Cheers
SM
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  #34  
Old 22nd November 2018, 12:06
Icare9 Icare9 is offline
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Re: Bf 109 vs. Spitfire production costs

The basic answer has to be in economics.
The Me109 was produced in vast quantities and until the later years of the War was virtually the only fighter produced.
Britain had the Spitfire and Hurricane, so a choice of which fighter performed best in what role, then succeeded by the Typhoon, Tempest, etc, so along with the Spitfire a range of perhaps more versatile aircraft for specific tasks.
The Americans had a wider range of fighters, but I'd suggest that the economics would mean that one type would have a larger production run, and therefore unit costs come down.
The Me109 by virtue of the largest production, even when the main aircraft plants has been damaged or destroyed must therefore be considered cheaper and certainly easier to produce, even in the most adverse conditions of round the clock Allied bombing.
You simply couldn't produce that number if it was too costly or complex.

But I'm no economist, and there must be ancillary costs of engine, equipment and servicing to factor in.
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  #35  
Old 23rd November 2018, 13:54
Jukka Juutinen Jukka Juutinen is offline
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Re: Bf 109 vs. Spitfire production costs

SM, yes, the data was very interesting. The reason for asking is an interesting article "Development and Performance of Aero-Engine Fuel Injection Systems" by A. R. Griffin published in Shell Aviation News. There's a graph showing sfc on the x-axis and bmep on the y-axis. There are 3 curves with 50 deg, 94 deg and 160 deg valve overlaps. They indicate massive increase in kock-limited bmep at lean mixtures with increased overlap.
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  #36  
Old 23rd November 2018, 15:41
schwarze-man schwarze-man is online now
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Re: Bf 109 vs. Spitfire production costs

Hi Jukka,
Good. I do expect that the DB605D/DB/DC and related late 605's had the same cam timing as the 605A as, although the camshaft is a different part number with the forward scavenge pumps drive, there is no information to suggest a major change of cam timing in the data that we have. Also, the timing is already pretty radical for a large 3litre cylinder running at only 2800rpm.
The article that you refer to sounds interesting. Do you have a link to it please?
Best wishes,

SM
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