Groundhog Thread Part Deux - P-39 Fantasy and Fetish - The Never Ending Story (Mods take no responsibility for head against wall injuries sustained) (2 Viewers)

[GregP]

Yah. It's the only pic of an aux-stage engine I could find with any indication of an aux-stage bearer mount.

 

[special ed]

.Re: post 64 by eagledad in FW-190F: how effective... I wonder why the Russians didn't use their wonder weapon super groundhog to catch the Fw 190F when their Yak-3,Yak-9 couldn't and La-7 only barely could.

 

[Dash119]

Yah. It's the only pic of an aux-stage engine I could find with any indication of an aux-stage bearer mount.

Greg,

Not being critical at all, I knew where you were going with the image. I just have to comment when my profile image is used in a post...

Kim

 

[pbehn]

Yep................................





View attachment 634748

Engine was in-between the pilot and the cannon

Did anyone slap Larry upside the head and say "squeezing the pilot in behind the engine isnt putting the engine in the front"

 

[P-39 Expert]

Please explain the term "construction drawings". I'm familiar with: Detail Drawings, which depict an individual part; Assembly Drawings, which describe an object made up of two or more parts; Installation Drawings, which shows a part or assembly in its installed location, and; Sectional View Drawings, which cut away part of an object to show the shape and construction along the cutting plane. There are also schematics which describe, at some degree of abstraction, systems within an aircraft. So what are "construction drawings"?

I presume you're referring to the "drawings" you cited in this post: XP-39 II - The Groundhog Day Thread. Those are Installation Drawings showing the station positions in the airframe. They ONLY show the distance between stations. They DO NOT show the height or width dimensions.

Just because compartments are "exactly the same length" does not mean that a 3-dimensional object will fit in that space. You need distances across length, width and height...and you also need to reflect any changes to those measurements to see if the physical space is sufficient...and, even then, there may be issues fitting an assembly into the available space because other parts or assemblies might get in the way.

Same width too.

 

[P-39 Expert]

Hey P-39 Expert. We all KNOW the engine compartment (the part where the power section goes ... you know, the engine block and cylinders) is the same size because the same engine block fits into it. What ISN'T the same size is the compartment aft of the engine compartment, where the auxiliary stage would go. I just got back from the museum and measured things on both the P-39 and the P-63. Go back to post #3,403 and look at the P-39 side views.

Notice the bulkhead just below the antenna mast and the bulkhead just aft of the rearmost exhaust stack. From the bulkhead under the antenna mast to the aft exhaust stack is 3" 9" on a P-39 (the one I used is a P-39N) and 4' 5" on the P-63. If you subtract the smaller measurement from the larger measurement, the difference is 8 inches using the "Measure" app on my cell phone. Doesn't sound like much, but it is the difference between the Aux stage fitting and not fitting. Also, the rear area in the P-63 is big enough for the Aux stage supercharger. In the P-39, it is NOT big enough for the aux-stage to fit inside. As I stated in an earlier post, you COULD knock some sheet metal out to shoehorn it in, but then you'd STILL have the CG issue that requires moving the wing or the pilot and you'd STILL have to supply a bearer mount for the aux stage after you move the existing bulkhead and whatnot back there, like oxygen bottles. Moving the pilot forward would put him firmly in the cannon breech area, so he'd not likely relish that idea. Seems better to move the wings aft a bit for CG purposes.

Hence, the P-63 Kingcobra, with all the changes built in to make a aux-stage Allison work.

You CANNOT fit a 2-stage Allison into a stock P-39 airframe and, if you DID by banging sheet metal around, the aux stage would have no support to mount on, and it would rock back on the tail.

Not sure what you are thinking, but I have had two different museums that own P-39s, one of which has restored both P-39s and P-63s to flight status, tell me a 2-stage Allison won't fit in a P-39. My own measurements confirm that. Now, I can't show you a 2-stage Allison installation in our P-63, because ours is being restored with a single-stage engine, but there are several such pictures floating about. Here is one:

https://ww2aircraft.net/forum/attachments/p-63-ephrata-airfield-july-44-jpg.356901/


You can see the compartment aft of the power section is pretty full.

If you want to insist that you can make an aux-stage Allison fit into a P-39, please feel free. Nobody ELSE can get it done. Perhaps you can get into Mr. Peabody's WayBack Machine and go back to show them all how it is done. Failing that, since Sherman and Mr. Peabody might not be very cooperative, SHOW ME HOW TO DO IT. Get Allison Aux-stage engineering drawings and a Bell P-39 engineering drawings and show that the equipment and the supports fit where everyone else says they won't fit. Show it clearly and with measurements, accounting for everything needed to make a 2-stage Allison run.

Or ... please stop making that claim.

Same size Greg. Same length, same width.

 

[FLYBOYJ]

Same size Greg. Same length, same width.

Same width too.

 

[buffnut453]

Same width too.

Then why do you have so many people, including staff who actually restore P-39s, saying that there isn't room for the supercharger? Are they all idiots who can't even use a tape measure?

 

[P-39 Expert]

Gentlemen

The 2 stage Allison engine E9 (V-1710-47) was used on the XP-39E aircraft. However, to get it to fit, the fuselage was lenghtened 1.75 feet to accomodate the longer Allison E9 engine.

This is an error perpetuated over 75 years. The aft fuselage was lengthened, but lengthened aft of the engine compartment. Engine compartment is the same size on the P-39, P-39E, and P-63.

As GregP and many others have written, one could not just replace the the single stage Allison engine with the 2 stage engine in a standard P-39 without modifications of the airframe. IMHO, the P-39 was looked upon unfavorably by the US and GB because it did not have the range/combat radius required by those 2 air forces nor did it have the required high altitude performance that was desired.

P-39 with 120gal had 20% more fuel than a Spitfire V.

(Again stated by many on this forum) Again my opinion, the P-39 did relatively well with the Soviet Air Force because air combat on that front was mostly low altitude (under 20,000 feet) and the airfields were relatively close to the front (combat radius not as critical).

Eagledad

Source: Cobra, by Birch Matthews pages 170 to 174. pages include a table by Bell engineers comparing the dimensions of the P-39D and XP-P39E.

I need to get an asprin for my headache.

 

[pbehn]

Same size Greg. Same length, same width.

So why waste time and money on the P-63?

 

[P-39 Expert]

So why waste time and money on the P-63?

For the umpteenth time, the engine (V1710-93) was in production from April 1943 but the first P-63 airframe wasn't completed until October. Six months in mid 1943 was wasted when the engine could have been installed in a P-39.

 

[buffnut453]

The aft fuselage was lengthened, but lengthened aft of the engine compartment. Engine compartment is the same size on the P-39, P-39E, and P-63.

Yes, because if you read Greg's post instead of just ignoring it, he says the supercharger fits into the compartment AFT of the engine compartment. Why do you persist in saying black is white when all evidence screams that you're wrong?

 

[FLYBOYJ]

This is an error perpetuated over 75 years. The aft fuselage was lengthened, but lengthened aft of the engine compartment. Engine compartment is the same size on the P-39, P-39E, and P-63.

P-39 with 120gal had 20% more fuel than a Spitfire V.

You realize that your credibility here is almost non existent. Until you start putting hands on hardware, I suggest you sit back in your armchair and just listen.

 

[pbehn]

P-39 with 120gal had 20% more fuel than a Spitfire V.

It had the same amount of fuel on board as a Spitfire VII, VIII or some Mk IX all you need to do is plumb in the wing leading edge tanks 25 gals for the pair, we have been through this many times. If internal fuel was the winner everyone would be in Fairey Battles.

 

[FLYBOYJ]

For the umpteenth time, the engine (V1710-93) was in production from April 1943 but the first P-63 airframe wasn't completed until October. Six months in mid 1943 was wasted when the engine could have been installed in a P-39.

And if this was such a great idea those really smart AAF officers (maybe the same ones you spoke about who designed those wonderful charts that you don't understand) "would have" saw fit to issue a contract to Bell to do this - or better yet, maybe Larry Bell "would have" went forward with company funds to show the AAF this great idea you came up with 77 years+ later.

 

[pbehn]

For the umpteenth time, the engine (V1710-93) was in production from April 1943 but the first P-63 airframe wasn't completed until October. Six months in mid 1943 was wasted when the engine could have been installed in a P-39.

Seriously, are you suggesting that the solution was there for six months and it only needed someone as bright as you to suggest it?

 

[buffnut453]

Seriously, are you suggesting that the solution was there for six months and it only needed someone as bright as you to suggest it?

It's a pretty impressive ego, to be sure!

 

[buffnut453]

You realize that your credibility here is almost non existent. Until you start putting hands on hardware, I suggest you sit back in your armchair and just listen.

I'd settle for him actually reading and comprehending posts from other people...or at least asking questions about things that are unclear to him.

 

[Shortround6]

A few dates that may be of interest.
June 27, 1941 they (USAAC) placed an order for two prototypes of an enlarged version (of the P-39E) powered by the same Allison V-1710-47 engine. The designation was XP-63 (company designation was Model 24).

In September of 1942, even before the first flight of the prototype, the aircraft was ordered into production by the USAAF as the P-63A (Model 33)

The XP-63 Ser No. 41-19511 flew for the first time on December 7, 1942

The second prototype (41-19512) flew for the first time on February 5, 1943

The XP-63A flew for the first time on April 26, 1943

So the "expert" would have us believe that in all that time that they were working on the XP-39E and the P-63 projects (nearly two years just for the P-63 project) NOBODY walked over to a regular P-39 with a tape measure, spent a few minutes and called out across the hanger "hey guys, the new engine will fit in the old airplane!"

 

[pbehn]

I'd settle for him actually reading and comprehending posts from other people...or at least asking questions about things that are unclear to him.

Years ago all I knew about the P-39 and P-63 was that, because the engine was installed in the middle of the fuselage of the P-39, putting a bigger engine in it needed a bigger plane which was the P-63. I have learned all sorts of interesting stuff from many posters and all of it supports what I knew before, probably because it is so bleedin' obviously obvious.