I am finishin a 1/48 scale Thunderbolt and am getting ready to weather it. The problem is that i am having trouble finding good pictures of where the plane got most of its wear and tear. Plus finding a good picture of the exhaust stains and color are very hard. If any body could direct me to an internet site that has good pictures or a book with some good pictures do tell.
The simple answer is that they didn’t have exhaust stains. Since the turbo was in the rear of the fuse and the exhaust was “recycled” and relatively cooler, you didn’t see the blackening of the lower fuse the way that you would see the exhaust stains on the front of something like a P-40 or -51.
Most of the wear and tear would be around the access panels and other areas that saw frequent handling.
Hope this helps.
It’s true, I’ve seen plenty of black & while photo and you just don’t see exhaust stains as you do on other aircraft types.
Sorry about those guys. I guess they never looked under a P-47. You may have posted this question at another site, if so I’m sorry for repeating myself.
Yeh, cooler exhaust gases or not radial engines are big, dirty and if they’ve been worked hard thay’re probably spitting out their fair share of oil
Not the best of color but I think you’ll get a better idea. The area on the D-Day Stripes is most likely oil/carbon. I see no reason for mud/dirt to be in that area. If you ever poured dirty oil on a flat white car I’m sure you’d get the same results. HTH.
Those are some pretty neat pictures. The streaking that starts near the wing root is the exit for the waste gates, where exhaust is dumped overboard to regulate turbocharger turbine speed and manifold pressure, the remainder of the exhaust exits aft under the belly which is where the turbocharger is located. Look at the bottom of a B-17 or B-24 nacelle, or the top of a P-38 tail boom for the same turbocharger, GE made them all but unlike the P-47, their turbos were not covered by fairings. The P-38 tail booms got nasty on top aft of the turbos, as the waste gate was located on the aft side of the turbo, as it was on the bombers.
When the turbo was off, the exhaust was directed to the waste gates just in front of the wing roots, and those areas did get some staining. The turbo was off when the engine started up, so the thick exhaust from the cold engine came out there.
A couple of those pictures show the streaking from the waste gates.
Bill
Mind your manners.
A few points here:
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The P-47 uses an external supercharger powered by an exhaust-driven turbine, aka a turbosupercharger. When the engine’s running, it’s running.
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All the exhaust gas is channeled through the turbine and the excess is dumped via the waste gate at the back of the turbine housing. On the P-47 this is located on the belly aft of the wing.
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The small shudder doors in front of the wings are the oil cooler vents. They leak oil by design through a relief valve but there is NO exhaust gas coming out.
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Radials are oil slinging pigs. As proof the Jug carried an oil reserve of just over 28 gal. It’s hard to get good views but the belly would be filthy after a short time in service.
Pat
Pat:
I offer a few comments and references which lead me to conclusions different from yours:
Point 1: Whether the turbocharger is turning or not is not so relevant as whether it is raising the manifold pressure above ambient. While it may or may not be spinning at dead idle (and I would not know as I have not crawled under a running P-47 to check) it will not be producing any “boost”. That would be undesireable.
Points 2 and 3: Regardless of the installation, not all of the exhaust will flow through the turbine wheel of the turbocharger. On the P-47, the turbocharger wastegate is just aft of the oiler cooler doors, as shown in the photo from Detail and Scale #54 on the P-47. It is in the exhaust stream before the turbocharger. It is true that the wastegate on most GE turbochargers is at the aft end of the turbocharger housing, but the housing is designed in such a way that the wastegate vents the pressure from the exhaust stream in a plenum before it reaches the exhaust turbine. The GE turbos are not like a modern turbocharger, which has two centrifugal impellers, one in the intake stream and one in the exhaust stream in reverse flow so it takes energy from the exhaust. The GE turbo had a centrifugal impeller for the fresh air, and the turbine wheel is an axial flow design. The exhaust that runs through the turbine wheel goes overboard to the atmosphere as it exits the turbine wheel. See the page from the Allison V-1710 manual showing a cutaway and the fluid and air flows for the GE turbochargers.
Point 4: I would certainly not argue the point that radials tend to leak oil, and it does not take much of a leak to make a big mess. They have a lot of parting surfaces, and I have worked on R-2800’s in Sikorsky CH-37’s. However, leakage is not the major reason for the large oil capacity in an air cooled aircraft engine, cooling is. About 40% of the cooling of the engine is done by the oil, as it rests in the tank and of course as it passes through the oil coolers.
John,
Thank you for your remarks. You pointed out an error in my post which I will address below. You did however raise some additional questions.
The function of an a/c supercharger is to “mechanically pump air from the atmosphere surrounding the aircraft into the engine manifold at the pressure required to obtain the rated power output of the engine.” It is kind of relevent if it’s turning because how else does it accomplish this? As I stated in my original post the supercharger can be disengaged (not recommended) but the turbine runs when the plane runs. There is no way to completely shut off the exhaust nor would you want to.
You are correct and my response to an earlier post where I commented on the oil cooler doors was not entirely accurate. The port shown in the D&S photo IS an exhaust vent but I have found out that it is designed to vent gas before it reached the turbine due to the large volume produced by the R-2800. I believe this is the largest engine that utilized only one supercharger during WWII.
I did not mean to imply that cooling did not factor into the design of the oil reservoir but I assure you leakage WAS a major concern with WWII radials. As an example, SOP for the 98th BG while in N. Africa was to fill the deicer system with oil and plumb it into the tanks to gain an emergency reserve of 21 gallons. A lot of heavy bomber flight engineers have told me, “if it wasn’t throwing oil, it’s out of oil!”
Pat
The oil pressure relief valve on a piston engine engine does not vent oil overboard. In the R-2800 installations I’ve worked on (A-26, PV-2, F4u & P-47) the oil goes from the reservoir to the engine pump, thru the engine to the filter, then to the oil cooler(s) and finally back to the reservoir. An adjustable oil pressure relief valve is installed in the pressure side of the system just downstream from the oil pump. The valve is a steel ball which sets over an inlet hole, a steel spring pressing against the ball and an adjustment screw/bolt which sets the pressure against the steel ball. When the pressure in the system goes above the pressure set on the ball, the ball opens the inlet which lowers the system pressure. The oil vented around the ball is then returned to the oil reservoir. The oil pressure relief valve is set to open anytime the oil pressure in the engine is above 80 psi and the operating temperatures are in the normal range. The oil system is basicly a closed system. Your car has the same basic system except the oil pressure relief valve is not adjustable, rather depending on the spring alone to set the pressure. (and most of us don’t have oil coolers on our cars)
Pat:
I agree with everything you said in your last post, and thanks for your nice reply. It’s not like any of us “owns” knowledge, it’s just there to share. I certainly agree that radials leak if they are running, and the CH-37 was a good example, even though ours had a very high level of maintenance. Those engines were always running at pretty high power and the only airflow they got was from a cooling fan on the clutches.
I don’t have a P-47 manual, but I am still wondering if they had three wastegates, two up front (one on each side) and the standard one on the turbocharger itself. Seems like it would be difficult to control the turbo speed that way, but it is possible and the R-2800 is a lot bigger than the V-1710’s, R-1820’s, and R-1830’s that also used them.
John
Just a few data points. My father flew in WW II and saw many P-47s. He was a combat photographer who traveled around the Pacific for different tasks. He saw a lot of P-47s in New Guinea.
He made a point of memorizing the sound of every Allied aircraft he encountered because he thought it might save his life someday. If he heard something he didn’t recognize, he would make sure he was near a bomb shelter.
He said the P-47 on take off and landing sounded very different than in flight. It was louder and “breathier”. He though it was due to the exhaust being diverted to the stubs in front of the wings while on the ground. He may have asked someone about it.
Apparently the turbo could be turned off on the P-47 because I recall reading a story of a P-47 pilot in France who got hit on a ground attack mission and thought he was going to have to bail out because the plane was making expensive noises and he expected the engine to quit. On a whim, he shut off the turbo and the noises quit. He was able to fly back to base with no further incident. I believe he took a 20mm hit directly in the turbo.
Bill
Bill:
Perhaps there was a method of manually controlling the wastegates and opening them up, that could have done it. Hasn’t anyone out there got a manual? [:)]
well, it looks like you have to pay money to get an full operating manual, but here’s a brief checklist: http://rwebs.net/avhistory/opsman/pursuit/section6.htm
does does have a “supercharger - off” item.
Radials do leak more than most engines, due to clearances, and basic geometry. Some more than others - the Skyraider seems to be the most notorious spewer. They also have a higher rate of consumption as pointed out by John because it is used as a cooling medium. The rate of consumption allowed by my relatively small R-755B2 engine would be cause for grounding of a similar sized Lycoming (well simlilar power, not C.I.D.)
Thanks for the link, Bret.
Thanks John,
I certainly would agree with your comments that the purpose of all this is to exchange information in order to be more accurate modelers; this thread’s a great example. My apologies to the original poster for sending it off into left field! Seriously, there’s no reason for any of us to be uncivil about this kind of stuff.
I did come up with a plumbing diagram of the P-43 in the supercharger TM. Same plane, wrong engine. I don’t know about the in-lines but I do have manuals on the ‘smaller’ radials (1820s & 30s). They do not use an extra waste gate and pipe all the gas into the nozzle box, venting some before the turbo. I still think the wastegates near the collector ring on the P-47 is because that engine just produces too much gas. Maybe someone can add to that.
Pat
Bill and John,
I forgot to mention that in re-reading the B24 and 17 pilots manuals supercharger control is covered. I’m paraphrasing but it says that the supercharger should be left on at all times and only on final approach is it at the pilot’s discreation to shut it off. That would go a long way to explain the variations in engine noise. I would think that under 10K ft performance would roughly be the same w/o the supercharger.
Pat