Ring Chatter (or slap)
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Ring Chatter (or slap)
Anyone had this or want to take a stab at explaining its causes and symptoms. I'm hopefully reaching the end of the road in getting my engine running properly again after a tear down and inspection. Ring chatter is what the mechanic said was wrong with one of my cylinders. I want to arm myself with some knowledge on the subject.
Edit to add: 4 pot Lycoming
Edit to add: 4 pot Lycoming
The only time this would be an issue in a normally aspirated engine that is properly set up is at very high altitudes like 15 K +. To generate enough power to hold altitude you have run with high RPM but the max MP will only be in the teens and there will be not sufficient cylinder pressure to hold the rings firmly against the cylinder walls.
The result is scuffed cylinder walls and damaged rings. I have only seen this once in a C 182. After the owner insisted in in trying to cruise at very high altitudes his next annual found all of the cylinders with very low compression and a lot of blow by past the rings. 12 K USD for 6 new cylinders fixed the problem
The result is scuffed cylinder walls and damaged rings. I have only seen this once in a C 182. After the owner insisted in in trying to cruise at very high altitudes his next annual found all of the cylinders with very low compression and a lot of blow by past the rings. 12 K USD for 6 new cylinders fixed the problem
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This is a follow up thread from another I started last spring when I had a prop strike, the engine was torn down and inspected as per the FAA regs but never ran right when I got it back ( the aircraft is only 8 years old and the engine had 275 SNEW when the incident occurred) . I've spent the last 9 months taking it back to the engine shop trying to zero in on the problem after many misdiagnoses and unneeded fixes and tweaks that didn't solve the main issue. Specifically the bottom plug on cylinder number 1 kept gunking up at low rpm, running a fine wire (hotter burning) plug would fix the rough running I assume by burning up the oil that was fouling it when testing the mag that was related to that bottom plug, but if I put the regular plug back in it would foul up again when taxiing or operating at low rpm. It was agreed with the insurance and engine shop that a brand new cylinder/piston/ring kit would be installed which they are doing now. Prior to starting the job on Thursday the mechanic told me the problem was caused by "ring chatter"' which he describes as the join part of the ring not being seated correctly allowing oil past and through onto the plug which gets fouled up then causes a misfire unless it is cleared with excessive leaning during run up. The reason I asked the question is this isn't the first time I've been given a new explanation for the problem then after the recommended fix the issue resurfaces, I want to better understanding what he is telling me about this "ring chatter" which worryingly is at odds with what BPF describes and the compression checks come back within tolerance which also leads me to doubt the mechanics opinion.
Edit to add: ATC I had the timing verified by a second shop so I know that's not the issue.
Edit to add: ATC I had the timing verified by a second shop so I know that's not the issue.
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Piston slap was quite common in older motorbike and older aero engines. It used to be very common in police triumphs sold on to the public. It was the sign of being well used. It tended to reduce as the engine warmed up. Ring slap is when the ring journals are a bit worn so the ring isn't stable in the piston. This was very rare and I can't really see the cause unless the bore is so worn that the ring wobbles. It could be because the wrong oversize ring was fitted after a rebore.
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I have followed your sorry tale from the start and you have my sympathies.
Is this effect/problem also an audible effect or visible as witness marks on the bore?
I must admit to not having heard this term before, and have spent much of my hobby life inside engines of one sort or another (not my profession) but have no experience of aircraft power units apart from reassembling a C65 and a C90.
The rings should be a good running fit in the grooves so I cannot see how any chatter can occur especially at the RPM that this will operate. I fail to see how any effect can be caused by the ends of the ring assuming that it is 'gapped' correctly, and I think modern automotive and small engine rings are supplied to size these days although I always check square in the lower part of the bore.
Strange!
Is this effect/problem also an audible effect or visible as witness marks on the bore?
I must admit to not having heard this term before, and have spent much of my hobby life inside engines of one sort or another (not my profession) but have no experience of aircraft power units apart from reassembling a C65 and a C90.
The rings should be a good running fit in the grooves so I cannot see how any chatter can occur especially at the RPM that this will operate. I fail to see how any effect can be caused by the ends of the ring assuming that it is 'gapped' correctly, and I think modern automotive and small engine rings are supplied to size these days although I always check square in the lower part of the bore.
Strange!
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Duncan,
This saga has gone on so long that I find it a bit strange. These Lycosaurus engines are pretty much bullet proof, any engineer and his dog in this aviation business should know all that needs to be known about them by now.
I've never heard of the term "ring chatter" but would assume it means worn ring grooves, rings moving up and down in the grooves, piston slap is not the same thing, that's worn sloppy pistons swinging side to side as they move up and down the bore. This engine has been stripped apparently more than once?
I'm beginning to think someone is pulling woolies.
I've had a few faults in my own engine, stuck needle valve, half dead magneto, worn valve guides. And in every case the fault has been identified correctly and fixed correctly with no further trouble.
I don't know what the maintenance regime is on N reg or if the a/c is in UK or US, but I would recommend a word with my LAA engineer, in Tranent.
I don't even know if he is allowed to advise/look. If you want a third opinion PM for his details.
This saga has gone on so long that I find it a bit strange. These Lycosaurus engines are pretty much bullet proof, any engineer and his dog in this aviation business should know all that needs to be known about them by now.
I've never heard of the term "ring chatter" but would assume it means worn ring grooves, rings moving up and down in the grooves, piston slap is not the same thing, that's worn sloppy pistons swinging side to side as they move up and down the bore. This engine has been stripped apparently more than once?
I'm beginning to think someone is pulling woolies.
I've had a few faults in my own engine, stuck needle valve, half dead magneto, worn valve guides. And in every case the fault has been identified correctly and fixed correctly with no further trouble.
I don't know what the maintenance regime is on N reg or if the a/c is in UK or US, but I would recommend a word with my LAA engineer, in Tranent.
I don't even know if he is allowed to advise/look. If you want a third opinion PM for his details.
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Also there are only two ways that oil can get into the cylinder. Past the rings or down through the valve guides.
If you are getting good compression then it can only be the valve guides.
Fitting a new cylinder/piston/ring set should solve the problem but is a bit of an overkill.
A new set of valve guides, and perhaps new valves would, in my opinion, fix it.
Just my two pennorth.
If you are getting good compression then it can only be the valve guides.
Fitting a new cylinder/piston/ring set should solve the problem but is a bit of an overkill.
A new set of valve guides, and perhaps new valves would, in my opinion, fix it.
Just my two pennorth.
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Also there are only two ways that oil can get into the cylinder. Past the rings or down through the valve guides.
If you are getting good compression then it can only be the valve guides.
Fitting a new cylinder/piston/ring set should solve the problem but is a bit of an overkill.
A new set of valve guides, and perhaps new valves would, in my opinion, fix it.
Just my two pennorth.
If you are getting good compression then it can only be the valve guides.
Fitting a new cylinder/piston/ring set should solve the problem but is a bit of an overkill.
A new set of valve guides, and perhaps new valves would, in my opinion, fix it.
Just my two pennorth.
I truly wish I'd never bothered reporting the incident or making a claim and just bought a replacement prop and stuck it on myself right there next to the taxiway the day after the incident, them unbuttoning the engine for inspection has caused endless problems.
The shop had an electronic vibration analyzer which would specify where to put the spinner balance weights. The problem was the machine kept on giving difference answers. When an engine shop was consulted the first question they asked was "did the engine have a prop strike". The owner said no, but further investigation revealed that the serial number of the prop had mysteriously changed. Turned out the previous owner had left the airplane unsecured and a wind gust had tipped it on its nose bending one prop blade. He just slapped a new prop on and said nothing.
The engine was removed for inspection and the engine shop reported that the front bearing web was cracked almost all the way through and the engine was hours away from a catastrophic failure.......
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I'm not an aircraft engineer but have built quite a few other engines in my time, as an amateur. Isn't ring chatter caused by incorrect cylinder honing angle? The rings effectively "bounce" over the grooves left by the honing and don't bed in properly and don't scrape the oil as they should. This allows oil to reach the combustion chamber.
If your mechanic isn't honing the new cylinders correctly, changing them won't cure your problem.
If your mechanic isn't honing the new cylinders correctly, changing them won't cure your problem.
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The honing would have to be extremely course and exactly square to the bore to have that effect. The hone would have to be held stationary for some time to produce grooves that bad, requiring incompetence of biblical proportions.
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No, I don't think so. The honing angle can be quite critical and ninety degrees isn't the critical angle, it's much less. I always understood that it ought to be 45 degrees and anything shallower is less than ideal. Maybe a misunderstanding like that has caused the problem. But then, I'm just an amateur engine builder who likes to read up the theory, so what would I know?
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I did post a link (above) regarding the highly technical aspects of honing and ring chatter but from the responses afterwards figured it hadn't been widely read...These last posts confirm my suspicion.
Even if the honing angle is wrong surely it is the same in all four cylinders - or is it? Clearly something is different in that one cylinder that is oiling. Is there any possibility one cylinder was honed at a different time or setting to the others? Maybe the honing angles should be checked?
Even if the honing angle is wrong surely it is the same in all four cylinders - or is it? Clearly something is different in that one cylinder that is oiling. Is there any possibility one cylinder was honed at a different time or setting to the others? Maybe the honing angles should be checked?
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I would agree that 45deg is the ideal, but to cause chatter I think they would have to be close to zero. Just my opinion from a practical thinking point of view, I haven't read the theory either. Perhaps someone could explain chattering at, say, 30deg, 20deg? I can understand the oil transfer bit but not chatter.
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I would agree that 45deg is the ideal, but to cause chatter I think they would have to be close to zero. Just my opinion from a practical thinking point of view, I haven't read the theory either. Perhaps someone could explain chattering at, say, 30deg, 20deg? I can understand the oil transfer bit but not chatter.
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I would agree that 45deg is the ideal, but to cause chatter I think they would have to be close to zero. Just my opinion from a practical thinking point of view, I haven't read the theory either. Perhaps someone could explain chattering at, say, 30deg, 20deg? I can understand the oil transfer bit but not chatter.
Correction: I have read at least a part of the linked theory.
Halfway down page three is a reference to a standard passenger car having what amounts to far wider tolerances.
The average aircraft engine of this type is not a race tuned high performance engine with every ounce of power squeezed out of it. Followed by a complete rebuild after the race. It was developed from an engine designed to drive a farm tractor.
Correction: I have read at least a part of the linked theory.
Halfway down page three is a reference to a standard passenger car having what amounts to far wider tolerances.
The average aircraft engine of this type is not a race tuned high performance engine with every ounce of power squeezed out of it. Followed by a complete rebuild after the race. It was developed from an engine designed to drive a farm tractor.