Ring Chatter
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Thats kinds of what I want to know.
I heard it mentioned in relation to a potential problem with high RPM and very low MP (15" or less say).
Its full name is Piston Ring Chatter.
It might also be called Piston ring slap.
I just realised I might be posting this in the wrong forum
I heard it mentioned in relation to a potential problem with high RPM and very low MP (15" or less say).
Its full name is Piston Ring Chatter.
It might also be called Piston ring slap.
I just realised I might be posting this in the wrong forum
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piston ring chatter
You might find the info your'e looking for in this article http://www.warmkessel.com/jr/flying/td/jd/78.jsp
Join Date: Mar 2000
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Ring chatter, or more commonly in America, ring float, is caused by very low ICP's during high RPM, very low MP/BMEP ops.
This ain't especially good with large radial engines, not so critical with small GA non-geared piston engines.
Also, another item that has brought rather costly repairs to big radials is excessive master rod bearing wear, during the same high RPM, low MP ops.
Best avoided.
This ain't especially good with large radial engines, not so critical with small GA non-geared piston engines.
Also, another item that has brought rather costly repairs to big radials is excessive master rod bearing wear, during the same high RPM, low MP ops.
Best avoided.
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From “R-2800” by Graham White
The two primary functions of piston rings are (1) to seal the piston against the enormous gas pressures generated during the power stroke and (2) to reduce the flow of oil into the combustion chamber to a minimum. The spring tension in a ring is not very important, since the major component of the radial pressure for sealing is provided by gas pressure behind the ring exerting pressure against the cylinder wall. Spring tension, however, does play a more important role in the case of a badly worn cylinder. Side clearance in the piston ring land is a key dimension. Sufficient clearance needs to be provided to allow gases to flow over the top face of the ring and pressurise it against the cylinder wall. On the other hand excessive clearance will result in hammering of the ring against the lands, resulting in premature failure. This is especially true of the vulnerable top ring land. Early designers failed to realise the importance of sufficient land clearance. This resulted in collapsed rings, the gas pressure would tend to force the ring inwards thus destroying the seal. Ring face width was another area of controversy. The proponents of a wide ring face argued that there was less chance of the oil film being squeezed out, particularly towards the top of the stroke where boundary layer lubrication exists. This, of course resulted in less cylinder barrel wear. On the other hand, a wider ring carries more inertia, resulting in a greater tendency to ring flutter. Ring flutter is the phenomenon caused at high piston speeds, typically 2500 feet per minute and higher, when the ring will float off the lower ring land consequently destroying the gas seal. This results in violent blow-by and significant loss of power. For many years this phenomena was thought to be caused by radial vibration of the ring. Under normal circumstances, as the piston rises on the compression stroke, the ring is held, at first by inertia, and later by gas pressure, against the lower ring land. In this way, the full clearance above the ring is available for gas pressure to seal the ring against the cylinder wall. And at the same time the lower land is completely sealed. At some critical piston speed, however, the ring’s inertia will exceed both friction and gas pressure during the compression stroke and allow the ring to float off the lower land. Under these running conditions the ring will lose the gas seal and collapse resulting in the classic case of “ring flutter.” Rolls-Royce ran into ring problems when developing the 1931 Schneider trophy “R” race engine when it had an oil consumption of 112 gallons per hour. (No, not a misprint)
You will note it does not mention “chatter” – perhaps a case of terminology. The good folk at http://www.enginehistory.org are very helpful should you have questions.
The two primary functions of piston rings are (1) to seal the piston against the enormous gas pressures generated during the power stroke and (2) to reduce the flow of oil into the combustion chamber to a minimum. The spring tension in a ring is not very important, since the major component of the radial pressure for sealing is provided by gas pressure behind the ring exerting pressure against the cylinder wall. Spring tension, however, does play a more important role in the case of a badly worn cylinder. Side clearance in the piston ring land is a key dimension. Sufficient clearance needs to be provided to allow gases to flow over the top face of the ring and pressurise it against the cylinder wall. On the other hand excessive clearance will result in hammering of the ring against the lands, resulting in premature failure. This is especially true of the vulnerable top ring land. Early designers failed to realise the importance of sufficient land clearance. This resulted in collapsed rings, the gas pressure would tend to force the ring inwards thus destroying the seal. Ring face width was another area of controversy. The proponents of a wide ring face argued that there was less chance of the oil film being squeezed out, particularly towards the top of the stroke where boundary layer lubrication exists. This, of course resulted in less cylinder barrel wear. On the other hand, a wider ring carries more inertia, resulting in a greater tendency to ring flutter. Ring flutter is the phenomenon caused at high piston speeds, typically 2500 feet per minute and higher, when the ring will float off the lower ring land consequently destroying the gas seal. This results in violent blow-by and significant loss of power. For many years this phenomena was thought to be caused by radial vibration of the ring. Under normal circumstances, as the piston rises on the compression stroke, the ring is held, at first by inertia, and later by gas pressure, against the lower ring land. In this way, the full clearance above the ring is available for gas pressure to seal the ring against the cylinder wall. And at the same time the lower land is completely sealed. At some critical piston speed, however, the ring’s inertia will exceed both friction and gas pressure during the compression stroke and allow the ring to float off the lower land. Under these running conditions the ring will lose the gas seal and collapse resulting in the classic case of “ring flutter.” Rolls-Royce ran into ring problems when developing the 1931 Schneider trophy “R” race engine when it had an oil consumption of 112 gallons per hour. (No, not a misprint)
You will note it does not mention “chatter” – perhaps a case of terminology. The good folk at http://www.enginehistory.org are very helpful should you have questions.
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Just came across this interesting tale, the outcome of low boost and high RPM and the damage it can do.
http://www.beaufortrestoration.com.a...lEngineer.html
http://www.beaufortrestoration.com.a...lEngineer.html
