V-3420: any use for the engine?

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tomo pauk

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Apr 3, 2008
The Allison V-3420 was the 24 cylinder development of the known V-1710. While it was used to power some planes, it was never used in a mass produced one. So what plane, either mass produced or in prototype stage, would be the decent platform for the engine? Or maybe a plane that would copy the suitable foreign design or concept?
The dry weight of the engine was some 2600-2700 lbs, and was available as single stage, mech driven 2 stage, and turbo variants. Power was typically between 2300-2600 HP, military power; WER going to 3000 HP.
 
The B-39 (the V-3420 engine varient of the B-29) would have been a good application.

The B-29 with 2200 HP per R-3350 engine was always marginal on power. As soon as the R-4360 came out of the test cell, it was being planned for the B-29D, later renamed the B-50. What i think I know is that the 3000 HP plus per engine from the R-4360 made the B-29 a much better airplane to fly. The V-3420 powered B-39 could have gotten to that same place a whole lot sooner.

I think the biggest problem with the V-3420 was political. My theory is that too many generals remembered the poor altitude performance of the Allison powered P-39 and P-40 in 1942 and 1943, and the problems with the P-38 engines in the ETO. The only way Allison was getting another contract from the Army Air Force would be over their dead bodies.
 
Political, yes. But not in the sense you say, I think.

When the B-29 was in testing/starting production the USAAF suddenly found that long range escorts were actually required. Thus they pushed for the P-75, meaning that Allison concentrated on that program, delaying the B-39 program. The V-3420 had already been chosen as a back up to the R-3350, and a QEC module had been designed to fit on the B-29 nacelles. This was tested on the XB-19, which was previously powered by R-3350s. Unfortunately, instead of using proven components, that installation was also used to test an experimental turbo, which was not successful (at that stage).

The XB-39 flew without turbos, therefore, but still had much improved performance over the B-29, particularly, I would imagine, at take-off.
 
wuzak said:
B-29, B-32, B-26, Hawker P.1005 High Speed Bomber (proposed with Sabres and Centaurus), P-47.
Click to expand...

I'll add: F4U, F6F, P-61, maybe Typhoon/Tempest/Sea Fury, Firefly/Barracuda. Maybe Manchester.

An unconventional approach: Beaufighter, A-20, Mosquito, Martin Maryland - a single V-3420 replacing 2 wing engines.
 
It was a lousy engine for a single seat/single engine fighter, See the P-75. It was a bit wider than the R-2800 or even an R-3350 and the width was much longer than a radial. The Radials were only at max width for two cylinder rows. the W-24 engines are full width for 6 rows.
It is heavy, add the weight of the coolant systems to the dry weight and then compare.
In the early part of the war it was also pushing propeller technology. F4U was designed with that big 3 bladed prop because big 4 bladed props didn't exist. The first Lockheed Constellations used 16ft 3 bladed props on their R-3350 engines. The big four blade props do show up with the P-47 but the first ones had trouble handling 2000hp which is why they came out with the paddle blade props. Trying to use even more power in the same size prop isn't going to get very far.
People sketched a lot of planes with the engines buried in the fuselage and extension shafts going to tractor propellers, pusher propellers on the fuselage or tractor/pusher propellers mounted on the wings. 2 right angle changes of direction in each drive line. The practical problems of getting such schemes to work generally kept them on the drawing board or in prototype status. The P-75 barely made it into limited production using counter rotating props. The Douglas XB-42 Mix Master used counter rotating props.
 
Is there a reason to believe that a P-47 with turbo V-3420 would be any worse than the XP-47H or XP-72?
Or, the F4U with V-3420 to be any worse than F2G Super Corsair?
 
YUP!

While the R-4350 was a heavy engine (3400lbs) what you see is what you get. In the F2G Super Corsair it had no turbo supercharger and being air-cooled it didn't need radiators. It also made 3000hp at low level fairly easily (10.5lbs boost).

The V-3420 was wider (by 6 in) but shorter in height. It was about the same length and weighed a svelte 2660lbs but that is without radiators and for a single stage/single speed supercharger. , add 470 or so pounds (minimum) for cooling system. Power was 2600hp for take-off and low level. Engine used one big supercharger instead of two regular Allison superchargers. Performance at altitude without a turbo or mechanical auxiliary supercharger is going to be none too good. Both were on offer from Allison but then the weight goes up (3175lbs? for the engine used in the P-75). Allison had problems with fuel/air distribution on the V-3420 and many of them did not make rated power.
 
The 2 stage engine from P-75 indeed weighted indeed 3175 lbs (looking at the engine tables from AEHS), good for 2300 HP at 20000 ft, with cooling it would be some 3650 lbs. The single stage R-4350 was good for 2400 HP at 13500 ft - at 20000 ft, the V-3420 has ~10 % more power.
The best performing 2 stage V-3420 was good for 2300 HP @ 25000 (3275 lbs dry; 3750 with cooling?), the 2 stage R-4350 making 2400 HP @ 25000 ft (either 3685 or (in P-72) 3890 lbs). A two stage R-4350 from P-72 was using the remote auxiliary stage supercharger - not an option for the F2G?

The liquid cooled engine has more flexibility to reduce cooling drag, unlike the air cooled engine? What about the timing/availability?
 
The V-3420 was and IS a very good engine. It has the reliability of the Allison V-1710, which is WAY more reliable than a Merlin of any sort after the intake issues were solved, and they were solved by early 1943. It holds a tune MUCH longer than a Merlin and has a bit more than half the parts. The Fisher P-75 is a poor example, not becasue of the V-3420, but becasue of the airframe.

I think it would have been a very good engine for the Tempest as well as the B-29 and possibly some of the medium twin bombers.

Personally I like the unit that turns only one propeller better, but perhaps contra-props would be best for a ppowerful single engine fighter. The Skyraider would have done OK with it, but I think in retrospect the R-3350 was a great choice, too, so maybe we leave the classic alone and develop planes for the powerplant. I like the idea of a fast medium twin using the V-3420 and it could have worked out very well. In the event, we didn;t really need the development to close out the war, but it might have speeded things up a bit, who can say?

Like all the other "what ifs," we'll never really know, will we?
 
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Incidentally, the R-4360 never quite made the HP is was supposed to, and wasn't anywhere NEAR 3,000 HP early in its lifetime. Even today, when we have a lot of general knowledge about these things, the R-3350 powers past all the 4360's at Reno, where power is king.

I tend to discount the front running Merlins becasue they are all running Allison G-6 rods and are hybrid engines. Good ones ... but not really Merlins or Allisons. The stock Merlin rods will not take the power of the engine's potential at 3,600 rpm and 140" of MAP. The R-3350's and R-4360's are running their own parts and do quite well making high speed, but the R-3350 definitely has the upper hand in top finishes at Reno.
 
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Greg, what the engines may or may not do at Reno bears no relationship with what they were capable of in WW2. None of them would be rated anywhere near the (claimed) power of the current Reno engines.
 
Good point, Wuzak. OK, then the R-4360 was a bomb. It didn't make the power expected, was too heavy, and thus would not be in the running for anything in the presence of a V-3420 after the intake issues were solved. So, I'd say they produced the wrong engine.

I have never really had any use for the R-4360 at all, and the reliability of the R-3350 happened AFTER WWII, not during.

So during WWII, we chose to concentrate on the wrong engines. After WWII, the concentration on the R-3350 was vindicated, but it was not popular among B-29 creas at all during the war.
 
Certainly the potential was there for the V-3420.

But there were still issues - it didn't make twice the power of the equivalent V-1710.

The on-again, off-again nature of teh project can't have helped.

A late war, developed, V-3420 should have been capable of 3500-4000hp WEP.
 
The R-4360 has alot of potential that has never been addressed. The thing I favor of the Wright is the steel crankcase.
 
Another airplane that could have used the V-3420 is the B-36. As far as HP, the V-3420 stayed pretty even with the R-4360. As stated above, postwar a developed V-3420 could have been over 4000 HP, more than any R-4360 ever had.

I assume that the cooling drag for the R-4360 was fairly high. As in the Mosquito and the Mustang, properly designed radiators could have cut that cooling drag for a V-3420 installation to more or less zero.
 
Piper106 said:
As stated above, postwar a developed V-3420 could have been over 4000 HP, more than any R-4360 ever had.
Click to expand...

We are getting waaaay into what if land.

Basing a what if on what a late model V-1710 could do in WEP mode is rather IFFY and the P&W fans can point to the fact that an R-4360 did run for 22 hours in three days on a test stand at 4400hp. Since the war time standard for a WEP rating was 7 1/2 hours at the WEP rated level accumulated in 5 minute segments it seems that the R-4360 might have been rated at at over 4000hp WEP if their had been a war on and if it was felt to be needed. The engine was run as hard as 4850hp during this time and was run at 50 hours at 3500hp and 100 hours at 3000hp before being torn down for inspection.

An interesting article on the R-4360 can be found here;

http://www.enginehistory.org/P&W/R-4360/R-4360History.pdf
 
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