Radial vs liquid cooled engines

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Are your grand kids watchmakers then?

Turbines depend on extremely close tolerances both dimensionally and mass wise (to obtain the dynamic balance needed). Far tighter tolerances than on piston engines.

On any of the variable stator angle engines just one stator off angle will cause the engine to self destruct within seconds. Clearances are so critical that many of the bigger engines have manifolds around the outside of the turbine spraying "cold" (as in 200-400C) compressor air over the outside of the turbine case to shrink it to maintain blade tip clearances at the required dimensions.

On piston engines the connecting, master and articulating rods and the piston weights can vary considerably inside any single engine. The weight of the cylinders and all their mechanisms have no weight limits.

For many years the Australian Civil Aviation Safety Authority allowed the PT-6 turbine engines to run 12,000 hours between overhauls - well beyond what Pratt and Whitney recommended and far beyond what any piston engine is capable of. I am not aware of any failing but the overhaul cost would have been horrendous as erosion and cracking of internal parts would have put many of those parts outside repairable limits.
 
I was indulging in a little hyperbole. I didn't really visualise anything like the Photoshopped image of the cylinder poking out the top of the cowling.

But I think my facetious point might have a bit of unexpected depth to it: the anecdotes about R-2800-powered fighters dragging themselves home with a cylinder or two missing in action might well reflect that that radials in general, with their distinct cylinders, are more prone to this kind of damage than monobloc V12s. Maybe we don't get the same heroic stories about Spitfires, P-51s, P-38s etc because that kind of damage just didn't happen to their engines.
 
Yeah, its kind of hard to lose one cylinder when they're all solidly connected together...
 
Or disadvantage. If one cylinder lets go does it take one or more adjacent cylinders with it?

Granted it is less likely but if the detontaion forces (not combat damage) are enough to blow a cylinder off a crankcase (or head off a cylinder) on the radial what happens to the bolts holding down the head or cylinder block on the inline? The cylinder head (or parts) might not depart the airplane but head gasket (or equivalent) may no longer seal well enough to get any useable power from the affected cylinder and/or one or two adjacent ones?
A flailing rod on a a radial may very well chew up the crankcase. On an inline a flailing rod can punch holes in the cooling jacket, or bottom cover/dry sump.
The radial might last as long as the oil (losing quarts per minute). but the Inline is not going very far either if the coolant is leaking out and/or it is losing oil in large quantities.

I am fully willing to accept that many radials did NOT make it home with cylinders missing. But inlines had a few problems of their own.
 
How long would an R-2800 oil system hold out with a jug missing? The large drop in oil pressure and continuous flow overboard must have locked up the engine quite quickly. Radials being more dependent on oil for cooling than a liquid cooled counterpart
 
I have read that radials leaked more oil, were slower to start up and warm up.
Liquid cooled engines with ebullient cooling systems could save several horsepower by eliminating water pumps while providing more uniform engine cooling.
 
BAGTIC said:
I have read that radials leaked more oil, were slower to start up and warm up.
Liquid cooled engines with ebullient cooling systems could save several horsepower by eliminating water pumps while providing more uniform engine cooling.
Click to expand...
The oil is because half of their cylinders are upside down. The inline Gipsy series engines (in-line, inverted) always have oil under them. Not sure what an inverted liquid-cooled engine is like.
The warming up issue is due to having air-cooling. Close the cowl flaps and they seem to warm up reasonably quickly.
 

That may depend on where in the mission the damage occured. It may depend on how much oil they put in to begin with. A P-47 could hold up to 28 gallons of oil. oil was used during the flight.
Early B-26s could hold 42.5 gallons per engine. F4us held either 20 gal or 24 gal and F6Fs held 19 gal max.

Coming back after a long flight and a fair amount of the oil could be gone. Getting hit early and you could loose a few quarts a minute from a P-47 and still fly for 20 minutes or more before the bearings were in any danger. At a low power setting (about as low as the plane would stay in the air to minimize the vibration?) the engine might last a number of minutes at below normal oil pressure before it seized.

It was done a few times. How many more times I don't know, but even the R-1830s had a reputation for taking abuse and lasting, several B-24s made it home with one or more engines dead and the remainder running in the red for hours.
 
Oil pressure ? In the old days recip engines ran with zero oil pressure, and you'd be surprised how long even the more modern ones can. Oh and there are still many piston engines built today that don't even have an oil pump or a pressurized lube system.
 

Ok, list the ones that don't use oil pumps or pressurised lube systems that are not used in lawn equipment or model airplanes.
Ford gave up on splash lubrication with the Model T in 1927.
 
Shortround6 said:
Ok, list the ones that don't use oil pumps or pressurised lube systems that are not used in lawn equipment or model airplanes.
Ford gave up on splash lubrication with the Model T in 1927.
Click to expand...
Engines are engines. I did not specify a certain application.
 
PWR4360-59B said:
Engines are engines. I did not specify a certain application.
Click to expand...
No you didn't.
Like a lot of your posts. Vague references that you want us to look up or puzzle out rather than give links.
And applications do matter in order to do that "proper engineering" you talk about. A low stress, low rpm engine can get away without pressure lubrication much easier than a high stress and/or high rpm engine.
Type of bearing material can make a difference too.
Engines are not engines unless you think you can stick 12 Briggs and Stratton lawn mower cylinders/pistons on a common crankshaft/crankcase and beat a Ferrari.
 

Have you ever worked a turbine? Put one back together? It too takes someone with technical expertise. Tolerances are very precise. Not putting something exactly as it should can be catastropic.

It's not as simple as you pretend it is. What do I know though? I'm just an A&P who has worked on hundreds of PT6's and T700's. No skill required at all...
 
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I am aware of any AIRCRAFT engines with no pressure lube systems although most rotary engines used piston pumps and the lubrication was total loss. Many older engines had pressure lube for the crank-case but grease (Bristol Mercury and Pegasus) or splash (some deH engines) for the valve gear. Interestingly the Bristol Pegasus IIM3 manual requires the valve gear to be greased every three hours yet the Sunderland operated on 14 hour patrols.

Non aircraft engines are not of interest to the majority on this site.
 
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