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Post by stansdds on Jan 31, 2009 10:57:33 GMT -5
Maarten has posted some interesting information and it is greatly appreciated. One wonders what might have happened if the P&W redesign and testing had occurred much earlier and 3000+ hp R-2800's had become regular production units.
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Post by ashaman on Feb 15, 2009 9:02:49 GMT -5
Maarten has posted some interesting information and it is greatly appreciated. One wonders what might have happened if the P&W redesign and testing had occurred much earlier and 3000+ hp R-2800's had become regular production units. Much earlier when, exactly? Before the war? I don't think the R-2800 would have been able to reach those powers easily back then, even had the the redesign been made back then. The problem is not in " if", but in " how"? With what kind of fuel? I'm speculating here, but humor me please. A R-2800 working at 2800hp ( let alone a hypothetical 3000hp) surely could not use the 80/87 octane gasoline that was normal before the war. I doubt, even using ADI, that reaching that power ratio would have been profitable ( as in keeping the engine's life competitive) even using the 100/130 octane either, which was still widely unavailable then anyway, seen it would ( by what I can find on the net) come around only in the first 40ies, when the war was in full swing and civil aviation was put to hibernation to follow the army's requests. The 115/145 octane gasoline would come after the war ( in 1948, I read), and was unavailable back then... so speculating about a pre-war 3000hp high manifold R-2800 is only a lazy way to while away time on a slow Sunday ( like today). ;D PS Yes, the TC R-3350 could reach 2880hp with 100/130 gasoline ( Wet? Dry? Can't find a source on the matter), but it had the PRT, which were never used on the R-2800, so it's a moot point.
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Post by Tom/CalClassic on Feb 15, 2009 11:00:44 GMT -5
Considering that the discussion was talking about being in competition with the R-4360 (first production engine shipped in January 1945), I think the discussion mentioned could be safely thought to be POST war. While that wouldn't have affected aircraft like the L-049 (engine decision made too early), what would it have done for the Super Connies, or the DC-7's?
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Post by ashaman on Feb 15, 2009 15:36:52 GMT -5
Considering that the discussion was talking about being in competition with the R-4360 (first production engine shipped in January 1945), I think the discussion mentioned could be safely thought to be POST war. While that wouldn't have affected aircraft like the L-049 (engine decision made too early), what would it have done for the Super Connies, or the DC-7's? Well going by what Maarten wrote, the R-2800 reached 3500hp with the appalling MAP pressure of 140" and the power of 3800hp with the even more terrifying MAP pressure of 150"... to obtain 3000hp, and supposing a linear increment of power over MAP pressure, the engine should have received something like 125" MAP pressure... At what MAP pressure worked the R-4360 at the same power levels? I'm asking because I really have no idea, of the same power levels ( and for obvious reasons ) I only know the max MAP pressure of the 3400hp R-3350 Turbo Compound of the Starliner, that with its 59" shows quite the difference. I'm sure the engineer Frank Walker did everything he did because he was proud of the R-2800, and to brag a little about his engine's qualities, but from there to release a certification for an actual production engine to work at those pressures would have been a long jump.
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Post by Tom/CalClassic on Feb 15, 2009 19:37:33 GMT -5
Hi,
Yes, I certainly agree. And the reliability wouldn't be that great, I would predict.
The 4360 used R-2800 sized cylinders, so it had similar MAP values. That's how we fly the B377...
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Post by volkerboehme on Mar 19, 2009 14:19:12 GMT -5
Hi,
there can be considerable differences between engine performances in the manufacturer's lab and actual aviation use. The most importenat one probably is cooling - you can run an engine much harder if you put it right downsteam of powerful fans that keep CHT under control. An aircraft taking off at full power wil have much less cooling airflow - it is standing still at the beginning in the first place, and the cowling only is a compromise between drag and cooling as well.
Maybe a quick note back on the R-2800-engined Connie: The original L-49/C-69 prototype, s/n 1961, was originally fitted with R-3350, but got converted with R-2800s later during WWII, the designation was changed to XC-69E for that refit. It was later sold by the War Assets Administration to Howard Hughes, who hardly used it (something like 12 hours flying time in 2 years or less) and then sold it to Lockheed for a profit. Lockheed made a number of test flights in this configuration and then stretched it to the 1049 Super Constellation prototype, still with R-2800s, now comparing the performance to the previous data on the short version. Subsequently, it was used to flight test the radomes for the Warning Star radar picket versions. The plane was later fitted with various engines in the #1 and #4 (outboard) positions. At one time, it was fitted with a R-3350 on #1, R-2800 on #2 and #3 and an Allison Turboprop on #4 position. Probably quite a handful to keep thrust under control.
If you want to see a pick of the R-2800 engine installation - search for pics of the Super Constellation or Warning Star prototype configuration. That are R-2800s.
Best regards, Volker
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