Allison V-3420 Engine questions

[262crew]

1) How was this engine block constructed?
2) Was it one casting?
3) Was it two blocks bolted or welded together?
4) Are the heads the same as the V-1710?
5) Did each crank turn in opposite directions?
6) Was the contra rotating accomplished by gearing?
The 3420 that is in the National Museum of the USAF was it meant to be in a boat or did they install the exhaust manifolds backwards? Here is a link to some pictures. Click on each pic for a larger view. Since there really isn't any technical data on the web, I was hoping someone here may have more information.

http://airpower.callihan.cc/post/2008/0 ... hotos.aspx

[Merlin540]

"The General Motors P-75 Eagle was a fighter aircraft for which the Fisher Body Division of General Motors Corporation in September 1942 submitted a proposal to meet a United States Army Air Forces requirement for a fighter possessing an extremely high rate of climb. The proposal was for an aircraft that used the most powerful liquid-cooled engine then available, the Allison V-3420 (essentially a pair of 12 cylinder Allison V-1710 engines mated to a common crankcase), and components from existing aircraft. The program was cancelled with only a small number of prototypes and production aircraft completed..."
Quote from Wiki link-

[51fixer]

IIRC it was a large casting for the block.
Basically coupling two 1710s into a common nose case.

4) Are the heads the same as the V-1710?
Yes, I believe the cranks were V1710 as well.

5) Did each crank turn in opposite directions?
Think they both went the same way.

6) Was the contra rotating accomplished by gearing?
The 3420 that is in the National Museum of the USAF was it meant to be in a boat or did they install the exhaust manifolds backwards? Here is a link to some pictures. Click on each pic for a larger view. Since there really isn't any technical data on the web, I was hoping someone here may have more information.
The P-75 was a bit different of an installation as it was a pusher and had an extension to drive the prop.

The one I saw at POF was on a pallet on the ground.

Rich

[DoraNineFan]

This photo shows what appears to be a new crankcase casting, with the remaining components coming from the V1710.
http://www.enginehistory.org/Convention ... V-3420.jpg

Compare this with the DB610, which appears to be two DB605s coupled to a shared reduction housing.
http://www.aviation-history.com/engines/db610a.jpg

[262crew]

Very interesting engine. 262crew, the link I've posted here is something you most likely know already, but it shows some additional photos that give others some idea of the double shaft configuration. There was a lot of research then to push the engine output. A Napeir Sabre engine is another solution that utilizes 24 cyliners, but in an H configuration.
The NMUSAF photo shows the exhaust manifolds attached in the wrong direction, if, as the photo caption asserts, that this engine was used in the P-75. The overall configuration looks right for the P-75, with an appropriate reduction box you'd see on an aircraft. Its also possible that this engine is a test article, and not used in an intallation, so the manifolds were placed for convenience only, maybe? to redirect the exhaust in some manner consistant with a test rig structure. Or they have it screwed on incorrectly.
http://www.enginehistory.org/w3420.htm
This photo shows a close up the the engine casing seen from head on. To my eye, the engine case looks to be a single casting, but a closer examintation or engineering drawings would prove that either way.
http://www.enginehistory.org/Gallery/Ji ... 201-18.JPG
Need some POF people to provide some shots of their engine!

Thank you, the fist link you posted http://www.enginehistory.org/w3420.htm has some very interesting info. I like the idea of the 3420-7 looks like it could have been used in something like the flying pan cake (Vought V-173 / XF5U-1)?

From that link.

"The W-3420‑7 was another arrangement for keeping the engine over the wing in the fuselage, but in this case it would allow the propellers to be on the wings in small, low drag, nacelles. This general configuration was proposed with either tractor or pusher propellers, and either propeller could run left or right hand, whichever the customer preferred. It was considered by Bell with pusher props for a follow‑on to its XFM‑1. McDonnell Aircraft's first aircraft proposal in 1939 was for a long range fighter powered by either an Allison W-3420 or a P&W H-3130 buried in the fuselage and driving two pusher propellers aft of the wing through extension shafts and angle gear drives. Only one W-3420‑7 was built, and it never flew.

The W-3420 combined two V1710s into one engine. Many parts were common between the two engines, although some parts were obviously different. Both of the engines shown below had two crankshafts rotating in opposite directions, although in some versions of the engine they rotated in the same direction."

[The Inspector]

Also installed on the one and only XB-39 'City of Lincoln' as a hedge in case the R-3350 couldn't be cured of its penchant for becoming a campfire in flight. It actually looked pretty cool as a really slicked out B-29

[Dan K]

Also installed on the one and only XB-39 'City of Lincoln' as a hedge in case the R-3350 couldn't be cured of its penchant for becoming a campfire in flight. It actually looked pretty cool as a really slicked out B-29

I used to kid Gary about this as "Plan B" just in case Fifi's re-engine plan didn't work out...

[warbird51]

The XB-19 was also retrofitted with Allison W-3420"s turning it into the XB-19A.

[Dave Hadfield]

Dan Whitney's book "V's for Victory", referred to above, is the bible on this sort of thing.

I really recommend it. A fascinating book, chock-full of detail and photographs. It's expensive, and worth it.

Dave