Author Topic: Souped up P47 with Zemke's 56th?  (Read 436 times)

Offline Naudet

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Souped up P47 with Zemke's 56th?
« on: June 06, 2002, 02:04:30 AM »
Can someone describe me in which ways those P47 were souped up?

And were they souped up for high altittudes, medium or low one?

Thx in advance.

Offline Daff

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Souped up P47 with Zemke's 56th?
« Reply #1 on: June 06, 2002, 07:18:44 AM »
From various anecdotal evidence, both the 78th and 56th FG using the following 'mods' as standard, as early as mid/late '43.
Paddlebladed prop (added approx 500 feet/min for climb)
140 octane fuel (allows higher MAP without detonating)
Higher MAP (Up to 72 inches)

Robert Johnson recalled 'trying it out' at 30.000 feet and hit 370 mph IAS which is close to 500 mph TAS.

Daff

Offline K West

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Souped up P47 with Zemke's 56th?
« Reply #2 on: June 06, 2002, 07:55:28 AM »
http://www.p47advocates.com/messages/531.html

 Mr Brodys' book has more details and perhaps Widewing could shed some light on the details he knows about. AFAIK nothing major was done to the airframe or "drive train" - except just about all in theatre P-47's having or being retrofitted with later model props. It was just re-aligning, tweaking and adjusting what was already installed to perform far above factory/USAF specs, recommendations and limits.

 Westy

Offline whgates3

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Souped up P47 with Zemke's 56th?
« Reply #3 on: June 06, 2002, 10:28:21 AM »
http://home.att.net/~historyzone/Seversky-Republic7.html

goes into detail about the later 'souped-up' (as if it needed it) versions of The Jug...apparently the elimination of the razorback slowed it down a bit, but various modifications ("the P-47D-30-RE, incorporated a new dorsal fillet at the base of the rudder assembly) and upgrades (C series P&W R-2800)...later (1945) The 56th got the P-47 M:  "The official maximum speed is 470 mph. However, over-boosting the engine could tweak another 15 to 20 mph out of the big fighter"...all sorts of interesting stuff is there

Offline HoHun

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Souped up P47 with Zemke's 56th?
« Reply #4 on: June 06, 2002, 10:40:12 AM »
Hi Daff,

>Robert Johnson recalled 'trying it out' at 30.000 feet and hit 370 mph IAS which is close to 500 mph TAS.

Hm, are you sure about the altitude? 370 mph IAS seems to work out to 606 mph TAS, which at 30000 ft is close to Mach 0.9. (Or is there a mistake in my calculations?)

The P-51D's dive speed is redlined at 330 mph IAS at 30000 ft, for comparison.

Regards,

Henning (HoHun)

Offline funkedup

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Souped up P47 with Zemke's 56th?
« Reply #5 on: June 06, 2002, 03:36:49 PM »
It wasn't just Zemke's guys or the USAAF doing this kind of thing.  It was done everywhere there were pilots who wanted to live and mechanics who knew a little about performance.

Offline -ammo-

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Souped up P47 with Zemke's 56th?
« Reply #6 on: June 06, 2002, 04:24:14 PM »
Quote
Originally posted by funkedup
It wasn't just Zemke's guys or the USAAF doing this kind of thing.  It was done everywhere there were pilots who wanted to live and mechanics who knew a little about performance.


Exactly. This practice was done wherever creative crewchiefs and mechanics existed.  Polished exaust and intake manifold ports, oversized wastegates, highly polished AC skin, extremely tuned induction systems and exaust systems...all of this was *tweeked* to get the most out of the AC.  Bob Johnsons D-5 (lucky) is a highly publicized example because of his book. Maybe that is why the reference to the 56th's jugs is always mentioned.
Commanding Officer, 56 Fighter Group
Retired USAF - 1988 - 2011

Offline MiloMorai

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Souped up P47 with Zemke's 56th?
« Reply #7 on: June 06, 2002, 08:03:26 PM »
One did not mess with the Napeir Sabre, that was a court-martial offense.

Offline Animal

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Souped up P47 with Zemke's 56th?
« Reply #8 on: June 06, 2002, 09:04:31 PM »
Quote
Originally posted by MiloMorai
One did not mess with the Napeir Sabre, that was a court-martial offense.


Was it a fragile engine?

Offline funkedup

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Souped up P47 with Zemke's 56th?
« Reply #9 on: June 07, 2002, 12:29:24 AM »
Sabres had some major reliability issues.  They were cured eventually but not before the reputation of the Typhoon had been irrepairably damaged.  

The biggest problem was the sleeve valve system.  It didn't use poppet valves like pretty much every aircraft and automotive engine.  The cylinder sleeves had carefully shaped holes in them  and were driven up and down by cranks via skew gears and a hollow driveshaft.  They sleeves were driven so that the holes in the sleeves matched up with intake and exhaust ports in the cylinder walls, allowing mixture and exhaust to pass at the appropriate times.

The problem was that the sleeve had to move at very high speed and still seal off the ports and maintain compression.  This represented serious challenges in metallurgy, lubrication, and precision manufacturing.  And they weren't able to really get it right until a year or so after the Typhoon was in service.  

The engine had PLENTY of power.  The question was getting enough reliability for missions over the Continent.  If they had a reliable Sabre the last thing they wanted to do was mess with it to get more power.  It was a remarkable design and probably the most modern of WW2, but the technology wasn't quite there at first.

Now an engine like the R 2800 was just the opposite.  They were quite conservative designs.  They used tried-and-true technology and were pretty much unbreakable.  So they kept pushing the power up until they started breaking things.  That's basically what the P-47M program was about.

Bristol radial engines also used sleeve valves.  Probably the most notable is the Centaurus which powered the Sea Fury among other things.  These were probably the ultimate radial.

For more on this subject check out Graham White's superb volume.
« Last Edit: June 07, 2002, 12:38:54 AM by funkedup »

Offline Vermillion

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Souped up P47 with Zemke's 56th?
« Reply #10 on: June 07, 2002, 07:13:21 AM »
Now funked here I thought the R3600 was the ultimate radial, but I agree the Centaurus was impressive ;) Boy would I love to see the F2G as a perkie in AH.  For those unfamiliar with this baby, imagine a bastard crossbreeding of a La7 with a Corsair. Muahahahahhahah :D

Offline Widewing

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Souped up P47 with Zemke's 56th?
« Reply #11 on: June 07, 2002, 08:54:39 AM »
Quote
Originally posted by K West
http://www.p47advocates.com/messages/531.html

 Mr Brodys' book has more details and perhaps Widewing could shed some light on the details he knows about. AFAIK nothing major was done to the airframe or "drive train" - except just about all in theatre P-47's having or being retrofitted with later model props. It was just re-aligning, tweaking and adjusting what was already installed to perform far above factory/USAF specs, recommendations and limits.

 Westy


Generally speaking, it was common for American mechanics to "tune" powerplants to obtaim greater than rated power. Back in the 1940s, America was a nation of mechanics. Nearly every male over 18 owned an automobile, and most did their own repairs. There was no such thing as a warranty back then. Furthermore, many of these young men were tuners and into "hotrod" building. By the mid 1930s, performance shops were becoming more common throughout the nation. This provided for a highly skilled mechanic base for the military.

Col. Cass Hough was responsible for 8th AF Aircraft maintenance. He understood that his mechanics would not settle for "stock" engine performance. So, in effect, he turned a blind eye to unauthorized field modifications. Likewise, factory tech reps from the various aircraft and engine manufacturers introduced modifications to enhance performance. However, the modifications were never authorized by the AAF, yet were generally done with the knowledge of the Hough's office, but never spoken of in any "official" manner. Typical of this was Republic's modified wastegate for the R-2800 engine. Standard wastegate  springs were replaced by newly fabricated examples with a much higher spring rate. This kept the wastegates closed until much greater boost pressures could be obtained. Early efforts had some problems as the springs were not properly stress relieved and would sack out, actually causing a loss of power. Eventually, mechanics would take their arbor wound springs to the cooks, who baked then in their ovens at 450 degrees F for one hour. This relieved the stress and the springs maintained their rate and force. Indeed, it was an engineer in Col. Hough's office who suggested this. Hough estimated horsepower on the better tuned engines to approach 3,000 hp with water injection.

Other modifications included using auto body filler to fill gaps in the surface of the aircraft. Then, they were waxed to a high gloss.
many P-47s had their HF antenna posts removed or shortened. Many were fitted with fabricated whip antennas, of lower drag. Remember, speed wasn't the only goal. Increasing range was also a consideration, and Hough justified much of the unauthorized mods as fuel economy measures. No one in the 8th AF command interfered as long as results were positive.

When the P-47M arrived at the 56th, it suffered through much of the teething woes experienced with the early Jugs. Most pilots were content to fly their older aircraft because, in reality, they were just about as fast anyway.

My regards,

Widewing
« Last Edit: June 07, 2002, 10:47:47 AM by Widewing »
My regards,

Widewing

YGBSM. Retired Member of Aces High Trainer Corps, Past President of the DFC, retired from flying as Tredlite.

Offline Don

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Souped up P47 with Zemke's 56th?
« Reply #12 on: June 07, 2002, 09:11:51 AM »
Naudet:
The information is fairly extensive as to mods on the P-47, there were numerous changes made from P-47C to D models, and to modify it to be able to handle ground attacks etc. Following is an excerpt which may answer your question though. This info is taken from "An Illustrated Guide to World War II Fighters":

"Finally, measures were taken to improve the performance of the P-47D, especially in climb, at the lower altitudes at which it now almost invariably operated: the P-47D-22-RE introduced  a Hamilton Standard metal propeller of 13ft 0in. diameter with four wider chord 'paddle' blades, and the P-47D-23-RA introduced a similar Curtiss Electric propeller."

They had also done some things with the turbo charger exhaust system; redesigned vents for engine accessories, two additional sections of cooling gills on the rear of the engine etc.  But it was the prop that really made the difference to the improved performance of the P-47D overall.

Offline Sancho

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Souped up P47 with Zemke's 56th?
« Reply #13 on: June 07, 2002, 11:07:05 AM »
widewing, do you have a source for that information?  would love to read more about it.

Offline MiloMorai

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Souped up P47 with Zemke's 56th?
« Reply #14 on: June 07, 2002, 11:13:50 AM »
imho:)

The ultimate radial was the Lycoming XR-7755 that was to power the B-36 until "politics" reared its ugly head.

The ultimate mass produced radial was the P&W R-4360 Wasp Major. This is the engine used in the Goodyear F2G.

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If the automatic boost control of the Sabre was mis-adjusted it would allow too high a manifold pressure at low RPM > result detination and serious engine damage. No unauthorized meddling allowed.

trivia: the 6 centerless grinders (Sundstrand) were need by Napier they came from the P&W plant in Kansas City (P&W not happy)

These grinders were required because of the up to 0.010" out-of-roundness of the sleeves and cylinder insurts were the major cause of the engine seizures.

Another problem was Bristol would not share with Napier sleeve valve technoligy.

Did you know that Rolls-Royce was also working on sleeve valve engines,
the Eagle of 24H configuaration and 2807ci (46 l),
Pennine of 24X configuration of 2685ci (44 l) and
the Crecy V12 2 stroke  of 1593ci (26.1 l).