were any big radials reliable
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The resulting design used nine banks of four cylinders arranged around a central crankshaft to form a four-row radial engine.
Just from observation the Lycoming engine appears to be "4 banks of nine cylinders". Happy to be proved wrong though.
Just from observation the Lycoming engine appears to be "4 banks of nine cylinders". Happy to be proved wrong though.
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Brian Abraham:
I think not. See: The Most Powerful Diesel Engine in the World
This 36 cylinder engine was destined to be the largest reciprocating engine ever built. The displacement was 7,755 cubic inches.
"Just from observation the Lycoming engine appears to be "4 banks of nine cylinders". Happy to be proved wrong though."
I think it's just the way they're looking at it. Where we're used to saying "2 rows of 9 cylinders," sectioning fore to aft along the crank, they're looking at it like 9 straight fours on a common crank, breaking it up every 40 degrees into a head for 4 cylinders. Is there a definition of "banks?"
I think it's just the way they're looking at it. Where we're used to saying "2 rows of 9 cylinders," sectioning fore to aft along the crank, they're looking at it like 9 straight fours on a common crank, breaking it up every 40 degrees into a head for 4 cylinders. Is there a definition of "banks?"
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I had a boss who once was a product support rep for Wright Aero, and he told me of an operator was failing R-1820 master rod bearings. After some sleuth work, he discovered they were using less than rated MAP for takeoff. This meant the centrifugal loads on the bearing were not fully balanced by BMEP. 
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Sure.
If the crankshaft were driven externally at rated speed without combustion taking place (as if an engine is shut down with a windmilling prop), then the master rod bearing sees only centrifugal loads.
But turn on fuel and ignition, and now the power-stroke gas load on the pistons, pushing "down" on the con rods, is in a direction opposite the centrifugal load on the master rod bearing.
Thus the balance between manifold pressure (MAP) and RPM is crucial to long TBO life on these engines.
P&W went through quite an episode of developing the right bearing alloy for the master rod of the R-1830 and the like. I'm sure Wright and Bristol etc. had the same tribulations.
If the crankshaft were driven externally at rated speed without combustion taking place (as if an engine is shut down with a windmilling prop), then the master rod bearing sees only centrifugal loads.
But turn on fuel and ignition, and now the power-stroke gas load on the pistons, pushing "down" on the con rods, is in a direction opposite the centrifugal load on the master rod bearing.
Thus the balance between manifold pressure (MAP) and RPM is crucial to long TBO life on these engines.
P&W went through quite an episode of developing the right bearing alloy for the master rod of the R-1830 and the like. I'm sure Wright and Bristol etc. had the same tribulations.
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We operated P&W R2800s on a super short cycle. Climb 7 mins, cruise 7 mins descend/approach 7 minutes. The biggest problems we had were not master rod failures, but "23 fin" failures, ie thermal shock cylinder failures, and a few ring land failures.
We had a steady program of power/cooling management that eventually resulted in most engines running out to 2,000 hrs. Not bad on 21 minute sectors, as this was the early 70s when P&W overhauls were getting scarce, especially with new cylinders.
Due to archaic regulations, once a year we had to do a C of A test in which we did a 10 minute climb at 90% max gross, with one engine actually feathered, and the other 3 screaming away at M.E.T.O power. As often as not a real engine failure occurred within 25 hours after that brutality.
Ah yes those were the days-NOT.
We had a steady program of power/cooling management that eventually resulted in most engines running out to 2,000 hrs. Not bad on 21 minute sectors, as this was the early 70s when P&W overhauls were getting scarce, especially with new cylinders.
Due to archaic regulations, once a year we had to do a C of A test in which we did a 10 minute climb at 90% max gross, with one engine actually feathered, and the other 3 screaming away at M.E.T.O power. As often as not a real engine failure occurred within 25 hours after that brutality.
Ah yes those were the days-NOT.
Last edited by ZQA297/30; 30th Mar 2010 at 15:03. Reason: grammar
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Sure.
If the crankshaft were driven externally at rated speed without combustion taking place (as if an engine is shut down with a windmilling prop), then the master rod bearing sees only centrifugal loads.
If the crankshaft were driven externally at rated speed without combustion taking place (as if an engine is shut down with a windmilling prop), then the master rod bearing sees only centrifugal loads.
I have an article discussing the very same thing (in different words).
When the Crank or rod goes concentric in the bearing bore.
The simple version is that when the shaft of the journal goes concentric in the bearing with no load.....the oil is not under the same forces and pressures.
This oil then begins to rotate with the shaft. When oil RPM between the bearing and journal reaches half the RPM of the shaft all cushion is lost.
The lack of cushion then allows the shaft (journal) to kiss the bearing.
Leading to bearing failure.
Our normal policy is that the only time the prop should drive the crank was short final....when wiping the power for landing.
Theory being this minimized the time the Journal could go concentric in the bearing
As a side note.....I've seen alot of failures after prolonged periods of disuse. It got so you could expect a failure within about 50 hrs if the engine had been sitting for a couple years. Even with proper pre-oiling
