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Ring Flutter?

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Fred Kerfoot

Joined: 11 Jan 2006
Posts: 14
Location: Tampa, FL

Posted: Wed Oct 10, 2007 3:38 am Post subject: Ring Flutter?

What is piston "Ring Flutter"??  I have an IO360.  Just how concerned should I be?

  

     Fred K

Help yourself to FREE treats served up daily at the Messenger Café. Stop by today!  [quote][b]

_________________
Fred K

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Gilles.Thesee(at)ac-greno
Guest

Posted: Wed Oct 10, 2007 3:46 am Post subject: Ring Flutter?

Fredrick Kerfoot a écrit :

 	  Quote: 	
		  

 What is piston "Ring Flutter"??  I have an IO360.

  


	


Ring flutter is an uncontrolled vibration of the piston rings when 

pressure against the cylinder wall and rpm are inadequate.



 	  Quote: 	
		   Just how concerned should I be?


	


In my opinion, no need to lose sleep over ring flutter on a Lyc.



Best regards,

-- 

Gilles

http://contrails.free.fr

esmith6(at)satx.rr.com
Guest

Posted: Wed Oct 10, 2007 7:39 am Post subject: Ring Flutter?

I would be concerned...I suggest you check your engine  timing...Also if your fuel is old, it has lost some of it's volatility, and I  would drain it and replace it with "fresh" gasoline...Are you burning Auto  Gas?..The book says that 360 needs 100LL (all of them, 160 and above require  it.)....................Good  Luck.......................CHEERS!!!!.............................Gene  Smith.

 [quote]   ---

jrccea(at)bellsouth.net
Guest

Posted: Wed Oct 10, 2007 8:53 am Post subject: Ring Flutter?

There are autogas STC's available for the  160.

 JimC

 [quote]   ---

apilot2(at)gmail.com
Guest

Posted: Wed Oct 10, 2007 5:44 pm Post subject: Ring Flutter?

I guess I just don't see how you relate a question about theoretical ring flutter with engine timing or age of fuel. I'm missing the connection. Actually a 180 only requires 91-96 or 91 mogas with STC.

Only the 160 and the 200hp versions need the extra octane. 



On 10/10/07, Gene Smith <esmith6(at)satx.rr.com (esmith6(at)satx.rr.com)> wrote:[quote]        I would be concerned...I suggest you check your engine  timing...Also if your fuel is old, it has lost some of it's volatility, and I  would drain it and replace it with "fresh" gasoline...Are you burning Auto  Gas?..The book says that 360 needs 100LL (all of them, 160 and above require  it.)....................Good  Luck.......................CHEERS!!!!.............................Gene  Smith.

 [quote]   ---

GrummanDude

Joined: 15 Jan 2006
Posts: 926
Location: Auburn, CA

Posted: Thu Oct 11, 2007 10:57 am Post subject: Ring Flutter?

Finally, someone who paying attention.



Ring flutter is very rare.  Especially at less than 2700 rpm.  Piston 

ring seal depends on a balance of four forces: combustion pressure, 

ring inertia, the ringâ€™s radial expansion pressure and crankcase 

pressure. Ring flutter is uncontrolled oscillation due to an imbalance 

of those forces. Once a pistonâ€™s rings go into flutter, their ability 

to scrape oil off the cylinder wall as the piston moves downward is 

impaired, blow-by increases and oil consumption rises dramatically.



The combination of high rpm and low crankcase pressure typical of low 

engine loads causes those four forces to become imbalanced. The small 

amount time the engine sees regular, high-rpm, light-load operation, is 

rare.  Even so, if that happens, you may experience ring flutter and  

high oil consumption, but not likely.

--

_________________
Gary
AuCountry Aviation
Home of Team Grumman

Fergus Kyle

Joined: 03 Jun 2007
Posts: 291
Location: Burlington ON Canada

Posted: Fri Oct 12, 2007 5:37 am Post subject: Ring flutter?

Piston Ring flutter:

	`....seems to me we had the same problem on the Super Connie (Old

Bob may comment here). This aircraft was named the largest 3-engined

airliner on the Atlantic. So. on pain of death no Driver, Airframe, would

ever reduce the Brake Mean Effective Pressure (BMEP) below 90 with the RPM

at cruise or descent because the condition would induce 'ring flutter' and

an earlier engine change was inevitable.

	I suspect my employer's profit was based more on engine changes than

seat mileage.

Cheers, Ferg

glcasey

Joined: 01 Jul 2007
Posts: 23

Posted: Sat Oct 13, 2007 4:37 am Post subject: Ring flutter?

On Oct 13, 2007, at 5:27 AM, Gary Casey wrote:



 	  Quote: 	
		   I've heard this before, but consider this:  The piston rings run at  

 no load half the time regardless of manifold pressure (BMEP).   

 During the exhaust and intake strokes the pressure is very low, so  

 if the rings were going to flutter why don't they do it then?

 Gary



>

> Time: 06:37:28 AM PST US

> From: "Fergus Kyle" <VE3LVO(at)rac.ca>

> Subject: Ring flutter?

> Piston Ring flutter:

> 	`....seems to me we had the same problem on the Super Connie (Old

> Bob may comment here). This aircraft was named the largest 3-engined

> airliner on the Atlantic. So. on pain of death no Driver,  

> Airframe, would

> ever reduce the Brake Mean Effective Pressure (BMEP) below 90 with  

> the RPM

> at cruise or descent because the condition would induce 'ring  

> flutter' and

> an earlier engine change was inevitable.

> 	I suspect my employer's profit was based more on engine changes than

> seat mileage.

> Cheers, Ferg

_________________
Gary Casey

AzevedoFlyer(at)aol.com
Guest

Posted: Tue Oct 16, 2007 12:38 am Post subject: Ring flutter?

Gary,

 Baring gross factors like excessively worn groove or mismatched axial  clearance between ring and groove, ring flutter results from inertial forces +  pressure unbalance between the top face and lower face of the ring. Mostly, it  restricts itself to the first compression ring but I've seen the 2nd and  occasionally even the 3rd (oil ring) undergoing flutter. For  this unbalancing to occur, some gas has to leak into and pressurize the  inter ring (1st - 2nd) cavity. Along the expansion stroke, this stagnation  pressure becomes higher than the pressure acting over the top of the 1st ring.  When this occurs, the 1st ring lifts from its lower face contact with the  groove. How flutter progresses from this point onwards can become a very complex  process. On the other hand, if you ran an engine without any load on it at high  revs, inertia will become predominant and lift the 1st ring, causing  flutter. In a plane, such a situation might conceivably occur if you dive with  throttle closed and the propeller drives the engine to a sufficiently high revs.  Lastly, flutter refers to a rapid oscillation of the ring in the groove. Not to  a normal change of lateral face contact of the ring with the groove. This last  is usually precluded by either ring geometry (torsion) or by adhesive forces  generated by oil surface tension.

 Cheers,

 Miguel

 N8714D

 PA22/20-150 



See [quote][b]

MONTY(at)bpaengines.com
Guest

Posted: Tue Oct 16, 2007 7:53 am Post subject: Ring flutter?

In many years of aircraft ( and other engines, some of which are very high speed ), I don’t think I have ever encountered a positive ring flutter situation.  

The ring damage I have seen other than excessive groove clearance has been caused by not enough end gap, high power being used before cylinders were up to the proper temperature, ( 300 F ) and detonation.  An interesting observation is that a large percentage of new piston rings are NOT FLAT, but have a wavy surface.  A couple of manufactures’ go to great lengths to insure the surfaces a absolutely flat.  They use very sophisticated equipment to inspect for this condition.  

   

Pressure is always present behind the rings during the compression, power strokes and even thru the blowdown period of exhaust.  Pressure is what makes the ring seal.  

I agree that the pressure behind the 2nd ring is not as high as the top ring.  

   

High engine speed, high forward speed and low manifold pressure is more likely to damage counterweights on the crank;  that is the big danger with operating an engine in this manner.  Also dangerous is the fact that the cylinder barrel and head will cool at a much faster rate with the above mentioned operating procedure than the piston, which leads to the barrel shrinking down on the piston.  I have seen piston top lands with metal “ pulled “ .  This phenomenon is usually referred to as “ shock cooling “.  

   

The current design piston rings are semi-keystone ( half wedge ) which are designed to move in and out radially so not to “ stick “ in the groove and to help the ring seal when the cylinder is NOT up to temperature.  Older designs were full keystone.  Some engines still use full keystone rings.  

   

Some piston rings also have an angle cut on the inboard edge to allow some “ twisting “ of the ring and is used for a couple of purposes; 1. to place a sharp corner of the ring to the barrel face for oil scavenging,  2. to reduce barrel wear because the tension of the ring is somewhat reduced when the ring is “ twisted “, 3. to allow the ring to  

“ hydroplane “ over an oil film.   Plasma filled rings are rarely twisted.  In fact, a plasma filled ring should be installed with great care so as NOT to twist the ring.    

   

Monty Barrett  

   

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