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KiwiBiggles
Senior Airman
Interesting. The photo of the B-42 installation is extraordinary. I hate to think how many harmonics you would have to deal with in a drive shaft that long.
Stephan Wilkinson
Airman
- 27
- Oct 20, 2007
The artist's rendering under "P-38 With Radials Is a Bad Idea" is pretty amusing. The artist seems to have used mid-1930s DC-2 Wrights and cowlings as his radial ideals, while properly nacelled R-2800s were in fact very compact, small in diameter and of course powerful. "P-38 With R-2800s Is a Good Idea"?
wuzak
Captain
R-2800s weren't small in diameter. 52.5" over the engine.
rogerwilko
Airman 1st Class
- 102
- Mar 5, 2009
I don't understand how the spark plug cooling arrangement works??
Stephan Wilkinson
Airman
- 27
- Oct 20, 2007
They were a lot smaller than that single-bank radial in the artist's P-38 rendering.
Shortround6
Major General
HOW CAN YOU SAY THAT!!!!!
Just look at the accuracy of the P-39 drawing with the V-3420 stuffed in it
BTW there were just under 4 inches difference in diameter between an R-2800 and a R-1820. the P&W was about 7% smaller.
Just look at the accuracy of the P-39 drawing with the V-3420 stuffed in it
BTW there were just under 4 inches difference in diameter between an R-2800 and a R-1820. the P&W was about 7% smaller.
GregP
Major
The spark plug coolers are simple. There are two aluminum tubes that stick out of the lower cowling going forward. The back end of the tube is plugged. The tubes go back along the row of exhaust plugs (the outside plugs near the exhaust outlets) and have holes in them that direct the airflow onto the spark plugs.
Works very well and costs very little in drag.
Hey Milosh,
Thanks for this post. Although I worked on Allisons for about 2 years at Joe Yancey's shop, I never saw that particular presentation before. Good find!
Works very well and costs very little in drag.
Hey Milosh,
Thanks for this post. Although I worked on Allisons for about 2 years at Joe Yancey's shop, I never saw that particular presentation before. Good find!
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GregP
Major
It was very good-looking and significantly outperformed the B-17, but the B-17 was doing the job. Ergo, no change. While I love the Allison, there was nothing wrong with the B-17 "as is" and the change to the V-1710 would have resulted in better speed, but not by too much. If you don;t get significant changes in performance ... in a bomber ... then why change? In a fighter, a 25 mph increase might have been worthwhile. In a bomber, especially when the defending fighters can catch either one easily, what is the gain?
I agree with the decision to stick with the Wrights.
The driveshatfs in the XB-42 weren't all that long and were supported by bearings at suitable intervals.
I decry that the V-3420 wasn't really used. It did NOT have the tendency for oil leaks inboard (betweeen the two block) that caused the German He-177 to catch fire so frequently and could have been a very good engine for the U.S.A. .
I agree with the decision to stick with the Wrights.
The driveshatfs in the XB-42 weren't all that long and were supported by bearings at suitable intervals.
I decry that the V-3420 wasn't really used. It did NOT have the tendency for oil leaks inboard (betweeen the two block) that caused the German He-177 to catch fire so frequently and could have been a very good engine for the U.S.A. .
One thing the Allison Powered B-17 would have achieved is the faster B-17 which might have then matched B-24 speed and simplified mission planning and simplified the escorting of the bombers.
The Allison also had much more power, it seems to have developed further than the R-1820 and allowed grater take-off weights and even greater speed.
The Allison also had much more power, it seems to have developed further than the R-1820 and allowed grater take-off weights and even greater speed.
wuzak
Captain
The greater take-off weight with the Allisons was offset, I would guess, by the extra installation weight.
The V-1710 weighed 150-200lbs more than the R-1820. The cooling system weighed 430-500lb per engine (from America's Hundred-Thousand, the latter figure for the P-38J, the former for the prototype).
The problem with the XB-38 was that airframe modifications were required, in that the leading edge between the nacelles was removed and a radiator group put in its stead. Had a QEC module been developed with radiators included, the project may have stood a better chance of going into production.
But it was still unlikely. The XB-39 was developed from the B-29 with a QEC module for the V-3420, but it wasn't proceeded with even though it showed a greater performance improvement than did the XB-38.
The V-1710 weighed 150-200lbs more than the R-1820. The cooling system weighed 430-500lb per engine (from America's Hundred-Thousand, the latter figure for the P-38J, the former for the prototype).
The problem with the XB-38 was that airframe modifications were required, in that the leading edge between the nacelles was removed and a radiator group put in its stead. Had a QEC module been developed with radiators included, the project may have stood a better chance of going into production.
But it was still unlikely. The XB-39 was developed from the B-29 with a QEC module for the V-3420, but it wasn't proceeded with even though it showed a greater performance improvement than did the XB-38.
