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LHMark
Topic Author
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Piston Engine Configurations

Tue Oct 26, 2004 2:05 am

Can anyone help me with a question? What are the relative advantages between radial and in-line or Vee piston engine designs? I know radials don't need a radiatior. Is there anything else?
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dl757md
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RE: Piston Engine Configurations

Tue Oct 26, 2004 2:53 am

Inline and Vee configuration have less frontal area and therefor less drag.
It is true a radial and any aircooled engine no matter what the cylinder arrangement doesn't need a radiator, however a liquid cooled engine doesn't suffer from the affects of thermal shock. Thermal shock occurrs when an airplane descends and the engine cools too rapidly causing damage. Liquid cooled engines don't suffer from this because the thermostat controls the coolant temperature.

Dl757Md
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kaddyuk
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RE: Piston Engine Configurations

Tue Oct 26, 2004 3:21 am

Whoever said "laughter is the best medicine" never had Gonorrhea
 
Dalmd88
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RE: Piston Engine Configurations

Tue Oct 26, 2004 4:55 am

Also most horizontal opposed are aircooled. There are many more of these flying than any other type of piston. They have a small frontal area, and weigh less than water cooled. Dr Porsche also had some pretty good luck with them on the street and racetrack.
 
LHMark
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RE: Piston Engine Configurations

Tue Oct 26, 2004 6:48 am

KaddyUK, thanks a ton for the links!
"Sympathy is something that shouldn't be bestowed on the Yankees. Apparently it angers them." - Bob Feller
 
kaddyuk
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RE: Piston Engine Configurations

Tue Oct 26, 2004 7:41 am

No problem, Im glad to be a help...
Whoever said "laughter is the best medicine" never had Gonorrhea
 
411A
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RE: Piston Engine Configurations

Tue Oct 26, 2004 8:28 am

So-called shock cooling is not a problem, so long as the engines/throttles are handled by a professional, who positively KNOWS what he is doing.

The radial design offers superb weight/horsepower ratio, and in addition, offers simplified cylinder/parts arrangement, and also, offers (in some designs...the CurtisWright turbocompound series for example) over one horsepower per cubic inch displacement.

In-line engines can not hope to compete in this area, due to their design.
Close, but no cigar.
 
Illini_152
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RE: Piston Engine Configurations

Tue Oct 26, 2004 8:40 am

Horizontaly opposed engines are rather limited in size; I think the largest was the Franklin O-805 at 805 CID, but I don't know if it ever saw service. As they get larger, opposed engines from the same problem that plagues other air-cooled engines; keeping the rear jugs from overheating.

Radial engines can generally be made larger than other air-cooled engines, due to their larger frontal area and better cooling, their size topped out at around 4360 CID at 3500hp.

The largest V-type engines were liquid cooled and largely solved the cooling problem of larger engines, but liquid cooled engines add another system that can fail. I think the most bizzare of these has to be the Allison V3420- a 24 cylinder double-V engine (I think VW is calling these W engines now in their supercar). If you've seen it the thing is the size of a VW! Take two V-1710's and bolt 'em together.

http://www.wpafb.af.mil/museum/engines/radial.htm has some interesting info on most piston engines that were in service until around 1950 or so.

What is really amazing is how much power the racers at Reno have been able to squeeze out of these things. 4000+ hp out of a 60 year old engine designed to make 1700 hp is an amazing sight, though doesn't bode well for longevity!

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pilotpip
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RE: Piston Engine Configurations

Tue Oct 26, 2004 1:31 pm

One of the major design considerations in a horizontally opposed engine versus an inline engine with aircraft regards forward visibility. With their lower-profile it's easy to see how this would be an advantage over an inline design.

It would be neat to see some larger engines come into existence again. I'd imagine that with newer composite technologies and computer design it would be possible to eliminate the problems associated with cooling those rear cylinders. Many aftermarket cowls for older aircraft have done away with cowl flaps by shaping the air inlets to optimize airflow over the cylinders without the need of the cowl flaps and larger openings that increace drag.

I would also imagine that in some of the larger displacement engines that they may run pretty rough with all of the pistons moving in the same direction. A lycoming O-360 has pistons that are roughly twice the size of the ones in your chevy 350. That's a lot of mass moving back and forth at a high rate and I'm sure that if that force wasn't being countered by a piston on the other side it would really stress the airframe as well as the engine over time.
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SlamClick
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RE: Piston Engine Configurations

Wed Oct 27, 2004 12:15 am

And who could ever forget the Rotary, like the LeRhone? Similar in layout to a radial, but the crankshaft bolted to the airframe and was stationary. The rest of the engine rotated around it, with the propeller bolted to the crankcase.

(Not to be confused with the Wankel, which is often called a rotary.)

Largest opposed (or Boxer to you Euros) I can recall being in mass production was the Lycoming O-720.
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EconoBoy
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RE: Piston Engine Configurations

Wed Oct 27, 2004 3:24 am

It's interesting to note the different philosophys of aeroplane designers in WWII. In the US, radial engines dominated, with a couple of exceptions, like the Allison in-line engine used in the Lockheed P38. In Europe, it was the opposite - with a few exceptions like the Folke-Wolf 109 and the Hawker Sea Fury. Why was this?
Incidentally, the Folke-Wolf and Sea Fury both show how the larger frontal area of the radial installation can be mininmised by very tight cowling; little bigger in area than an in-line.
 
LeanOfPeak
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RE: Piston Engine Configurations

Wed Oct 27, 2004 4:22 am

I don't really see the dominance of radials in the US as far as fighters go. They were a good fit for heavy bombers (Which the US had a lot of) and in ground attack roles (Where their durability was a benefit), but as far as fighters went, the P-47 (Which got shoehorned into the ground-attack role with the advent of the P-51), the P-61, the -Cat series, and the Corsair are about all I can think of with radials. Vees went in the P-38, P-40, P-51, P-39/P-63... Seems pretty even, with the radials going in the heavier, more durable planes and the inline vees going in the lighter, nimbler, faster planes.

As for the dominance of inline vees on the European designs, I suspect that has to do with the influence of Schneider Cup racing on European aircraft design. The Schneider Cup racers (From which the Spitfire was directly descended) wound up mostly looking alike. Add in a design philosophy for fast, nimble fighters, and you get the Hurricane, Spitfire, Mosquito, Me-109, Me-110, the Il-2, the Yak-3, the Yak-9, and most of the Italian planes (And I'm sure I'm leaving some out) against chiefly just the FW-190 and the SeaFury.
 
SlamClick
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RE: Piston Engine Configurations

Thu Oct 28, 2004 12:25 am

LeanOfPeak I believe you are exactly right with the Schneider Cup influence. However, I must disagree on the subject of "dominance" of design.

Counting the P-38, P-39, P-40, P-51, and P-61 I can account for only 47600 aircraft produced. Of these, 9,500 were P-39s the majority of which went to Russia (or into the Bering Sea) in Lend-Lease.

On the other hand, counting only F-4F, F-4U, F-6F, P-47, TBM, B-17, B-24, B-25 and B-29 I get to 99,902 and when you add the PBY, PB-4Y, C-45/AT-11, C-46, C-47, C-54, N-2S, N-3N, AT-6, BT-13 and on and on, the preponderance of radials becomes staggering.

I like your screen name - recips anyone?

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EconoBoy
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RE: Piston Engine Configurations

Thu Oct 28, 2004 4:41 am

One advantage of an aircooled engine (admittedly not so important in times of peace) was that it could withstand more damage. In a liquid cooled engine, a bullet or shrapnel through a radiator or coolant pipe would soon result in overheating and seizure, whereas there were stories of radial engined planes making it back home safely with bullet holes in the cylinders.
 
L-188
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RE: Piston Engine Configurations

Thu Oct 28, 2004 7:16 am

Actually Slamclick very few ended up in the Bering Sea....they only had 90 miles to cross  Big thumbs up


In navel operations the Radial was clearly dominant, in Air ops, no so much.
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SlamClick
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RE: Piston Engine Configurations

Thu Oct 28, 2004 9:40 am

L-188 I know that. I just wrote it that way for grins. I've been told that a very large number never made it to Mile-30 or Eieleson from Buffalo and are presumably out there in the woods somewhere. I'm sure a fair number never made it all the way to the civilized part of Russia once they took over.

There is a dream of a lot of warbird types - finding a fairly intact one in a cold lake up there somewhere.

Overall, I'd bet that production of radials outnumbered inlines and vees about five or six to one. What got lost in my numbers was this; the bulk of the planes using radials used two or even four of them. Most of the ones using the V-12 used only one.



Happiness is not seeing another trite Ste. Maarten photo all week long.
 
L-188
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RE: Piston Engine Configurations

Thu Oct 28, 2004 9:47 am

Although Soviet numbers are hard to verify, my understanding was that their loses on the route over Siberia where less then the US loses on the Great Falls-Ladd Army Airfield route.

One difference is that the Soviets assigned pilots off the front line to ferring duty as a break from combat, so it can be argued their pilots where much more familiar with conditions. My understanding where that many US pilots where much fresher out of flight school. Also consider that the US pilots where getting factory fresh airplanes and essentally "finding the mistakes" in construction if you get my meaning.

I don't know if there are that many. A couple of P-39's have been pulled from lakes.

Russia on the other hand may be a different story. I suspect you may be right. But like I said the Soviets claimed a significantly lower loss rate.
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LeanOfPeak
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RE: Piston Engine Configurations

Thu Oct 28, 2004 10:10 am

As Econoboy seemed to be, I was focusing on the fighters, as the cargo planes, bombers, and ground-attack models were generally not as concerned as the fighters were with speed. They also had considerably larger frontal areas to deal with anyway, and could afford some frontal area tradeoff for good power-to-weight, reliability, and damage tolerance.

If we were going to deal with other classes of aircraft, we could make things interesting with the FW-200, Me-323, Ju-88, Do-17, Ju-52, Lancaster, Blenheim, Beaufort/Beaufighter, etc.

Re: The screen name, thanks. I wondered how many would recognize the reference.  Smile
 
FredT
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RE: Piston Engine Configurations

Thu Oct 28, 2004 4:43 pm

Recips are Real Aircraft, although possibly not as much as aircraft with no engine of course. I am still of the conviction that turbine engines only work due to an error in the calculations. When that error is found, they will all stop. Big grin

Interesting read here, for those reciprocally interested
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L-188
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RE: Piston Engine Configurations

Thu Oct 28, 2004 6:13 pm

Even the USAF played that game.

They had a prototype B-17 with Allisons flying around.
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