Radial engine 2-stage superchargers (R-2800, etc) - Aircraft of World War II

gjs238 · 03-26-2009, 02:26 PM

Can anyone shed some light on the development & use of multi-stage/multi-speed superchargers in the radial engines of WWII?

When did radial engine 2-stage superchargers become available?
I understand later versions of the F4U Corsair had 2-stage superchargers.

Allison seems to have taken a lot of heat for lack of development of 2-stage superchargers, but what about the makers of radial engines?

How did radial engine supercharger development compare to that of inline engines?

hrandy · 05-30-2009, 10:18 AM

I believe the first two stage mechanical supercharger was on the P&W R-1830-19 in 1938. Later -76 and -86 variants of the two stage R-1830s were used on Grumman F4Fs. There were some significant problems with engine surging that were not well understood at the time but were probably connected to poor diffuser design.

All the wartime P&W R-2800 powered F4Us as well as Grumman F6Fs had 2 stage mechanical superchargers.

While Rolls-Royce, Bristol, Napier, Daimler-Benz, Junkers, BMW and others were receiving generous financial support in the 1930s from their respective governments, Allison and all the other American engine manufacturers got no money from the U.S. government. Additionally the USAAF wanted all their high altitude aircraft powered by single speed mechanical superchagers assited by turbo chargers. This worked well with bombers with podded engines, but was a disaster with small single engine fighters. By the time the USAAF realized the error of its ways it was too late for Allison to make up lost ground to Rolls-Royce or Daimler-Benz.

The Allison 1710 in my opinion was a better basic design than the Rolls-Royce Merlin. It suffered greatly in comparison to the simply brilliant two stage two speed after cooled Merlins. The small engineering department at Allison simply coudn't develop the 1710 as quickly as the large well funded engineering department at Rolls-Royce.

Nothing on the radial engine side compares to the sophistcation of the two stage two speed after cooled Merlins. For long range bombers the turbocharged radials were the best. Of course turbojets were about to eclipse all piston engines as the war ended.

gjs238 · 06-01-2009, 11:00 AM

Quote:

Originally Posted by hrandy

All the wartime P&W R-2800 powered F4Us as well as Grumman F6Fs had 2 stage mechanical superchargers.

I thought only the F4U-4 "4-Hog" had 2-stage supercharging, using the -18W engine (?)

hrandy · 06-21-2009, 03:20 PM

Every reference I have seen states that the F4U-1 and the F4U-2 were powered by either the R-2800-8 or 8W. My favourite R-2800 book, Graham White's "R-2800 Pratt and Whitney's Dependable Masterpiece" shows the -8 and -8W as two stage intercooled engines. The second stage supercharger had a fixed drive ratio of 7.93 to 1, while the first stage supercharger had neutral, 6.46 and 7.8 to 1 ratios available.

Graham White's book has a few pages of information on the Corsair. On Page 463 he states that the only production Corsair with a single stage engine was the F4U-6 (AU-1), which was produced as a ground attack aircraft well after the end of WWII.

I've often wondered if the two stage R-2800s were worth the cost, complication and weight. It seems to me that the BMW 801 was close in output to the two stage B series R-2800s in a much more compact, lighter and probably cheaper package.

Another comparison that makes me wonder about the value of the two stage intercooled R-2800s is the big difference in speed between the P-61B (two stage mechanical supercharged C series R-2800-73s) at 366 mph at 20,00 ft. and the P-61C ( C-series R-2800-57s with CH-5 turbo-supercharger) at 430 at 30,000 ft. These are both two stage engines engines but the P-61C is a lot faster despite the very unaerodymanic looking turbo-supercharger housing under the engine nacelles.

jerryw · 06-21-2009, 10:35 PM

I came across the PATENT for the -32W "sidewinder" type superchargers recently. Makes interesting reading.
The number of the doco is US 2,667,298 and it is titled, "Arrangement of Opposed Superchargers".(Five very nice drawings) It can be downloaded free from the uspto.gov website.
Written by the designers, it gives a lot of insight into the thinking at the time.

gjs238 · 06-26-2009, 12:40 PM

Quote:

Originally Posted by jerryw

I came across the PATENT for the -32W "sidewinder" type superchargers recently. Makes interesting reading.
The number of the doco is US 2,667,298 and it is titled, "Arrangement of Opposed Superchargers".(Five very nice drawings) It can be downloaded free from the uspto.gov website.
Written by the designers, it gives a lot of insight into the thinking at the time.

Nice drawing!
It would be great to see a photo of this and any other supercharger arrangements.

03-26-2009, 02:26 PM	#1
gjs238 Member Join Date: Mar 2009 Posts: 97	Radial engine 2-stage superchargers (R-2800, etc) Can anyone shed some light on the development & use of multi-stage/multi-speed superchargers in the radial engines of WWII? When did radial engine 2-stage superchargers become available? I understand later versions of the F4U Corsair had 2-stage superchargers. Allison seems to have taken a lot of heat for lack of development of 2-stage superchargers, but what about the makers of radial engines? How did radial engine supercharger development compare to that of inline engines?

06-21-2009, 03:20 PM	#4
hrandy Junior Member Join Date: Feb 2008 Posts: 20	Two stage Corairs Every reference I have seen states that the F4U-1 and the F4U-2 were powered by either the R-2800-8 or 8W. My favourite R-2800 book, Graham White's "R-2800 Pratt and Whitney's Dependable Masterpiece" shows the -8 and -8W as two stage intercooled engines. The second stage supercharger had a fixed drive ratio of 7.93 to 1, while the first stage supercharger had neutral, 6.46 and 7.8 to 1 ratios available. Graham White's book has a few pages of information on the Corsair. On Page 463 he states that the only production Corsair with a single stage engine was the F4U-6 (AU-1), which was produced as a ground attack aircraft well after the end of WWII. I've often wondered if the two stage R-2800s were worth the cost, complication and weight. It seems to me that the BMW 801 was close in output to the two stage B series R-2800s in a much more compact, lighter and probably cheaper package. Another comparison that makes me wonder about the value of the two stage intercooled R-2800s is the big difference in speed between the P-61B (two stage mechanical supercharged C series R-2800-73s) at 366 mph at 20,00 ft. and the P-61C ( C-series R-2800-57s with CH-5 turbo-supercharger) at 430 at 30,000 ft. These are both two stage engines engines but the P-61C is a lot faster despite the very unaerodymanic looking turbo-supercharger housing under the engine nacelles.

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05-30-2009, 10:18 AM	#2
hrandy Junior Member Join Date: Feb 2008 Posts: 20	I believe the first two stage mechanical supercharger was on the P&W R-1830-19 in 1938. Later -76 and -86 variants of the two stage R-1830s were used on Grumman F4Fs. There were some significant problems with engine surging that were not well understood at the time but were probably connected to poor diffuser design. All the wartime P&W R-2800 powered F4Us as well as Grumman F6Fs had 2 stage mechanical superchargers. While Rolls-Royce, Bristol, Napier, Daimler-Benz, Junkers, BMW and others were receiving generous financial support in the 1930s from their respective governments, Allison and all the other American engine manufacturers got no money from the U.S. government. Additionally the USAAF wanted all their high altitude aircraft powered by single speed mechanical superchagers assited by turbo chargers. This worked well with bombers with podded engines, but was a disaster with small single engine fighters. By the time the USAAF realized the error of its ways it was too late for Allison to make up lost ground to Rolls-Royce or Daimler-Benz. The Allison 1710 in my opinion was a better basic design than the Rolls-Royce Merlin. It suffered greatly in comparison to the simply brilliant two stage two speed after cooled Merlins. The small engineering department at Allison simply coudn't develop the 1710 as quickly as the large well funded engineering department at Rolls-Royce. Nothing on the radial engine side compares to the sophistcation of the two stage two speed after cooled Merlins. For long range bombers the turbocharged radials were the best. Of course turbojets were about to eclipse all piston engines as the war ended.