Today's Message Index:
----------------------
1. 01:38 AM - Re: Re: Ring flutter? (AzevedoFlyer@aol.com)
2. 07:23 AM - Re: Knock sensors? (Noel Loveys)
3. 08:06 AM - Re: Knock sensors? (Hinde, Frank George (Corvallis))
4. 08:21 AM - Re: Knock sensors? (Monty Barrett Sr)
5. 08:53 AM - Re: Re: Ring flutter? (Monty Barrett Sr)
6. 04:51 PM - Re: Knock sensors? (lessdragprod@aol.com)
Message 1
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| Subject: | Re: 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
Message 2
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Thanks... I had heard of LOP before long enough ago to have completely
forgotten.
When in technical school we were always told to lean ROP
Noel
> -----Original Message-----
> From: owner-engines-list-server@matronics.com
> [mailto:owner-engines-list-server@matronics.com] On Behalf Of
> Greg Young
> Sent: Monday, October 15, 2007 7:35 PM
> To: engines-list@matronics.com
> Subject: RE: Engines-List: Knock sensors?
>
>
>
> LOP=lean of peak, ROP=rich of peak
>
> Regards,
> Greg Young
>
>
> > -----Original Message-----
> > From: owner-engines-list-server@matronics.com
> > [mailto:owner-engines-list-server@matronics.com] On Behalf Of
> > Noel Loveys
> > Sent: Monday, October 15, 2007 8:43 AM
> > To: engines-list@matronics.com
> > Subject: RE: Engines-List: Knock sensors?
> >
> > <noelloveys@yahoo.ca>
> >
> > I've seen the term LOP used a few times..... But have no idea
> > what it means.
> >
> > Noel
>
>
>
>
>
>
Message 3
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LOP is the most efficient place to run the motor. From my reading of the
Lycoming power chart it has about a 10% reduction in the BSFC in LOP vs
ROP (BSFC =.45 at 50F LOP and .5 at 80F ROP).
Rumour has it that the only way the old Howard Hughes Connies made it
across the Atlantic was to run the motors LOP.
Its about the only place I run my motor apart from take off and landing.
Frank
RV7a TMX IO360
-----Original Message-----
From: owner-engines-list-server@matronics.com
[mailto:owner-engines-list-server@matronics.com] On Behalf Of Noel
Loveys
Sent: Tuesday, October 16, 2007 7:22 AM
Subject: RE: Engines-List: Knock sensors?
Thanks... I had heard of LOP before long enough ago to have completely
forgotten.
When in technical school we were always told to lean ROP
Noel
Message 4
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The Wright 3350 engines in Super Connies and also the B-29 were operated
LOP. The FE had the most important job on the flight crew. As I
remember,
The FE also had a set of throttles.
Monty Barrett
-----Original Message-----
From: owner-engines-list-server@matronics.com
[mailto:owner-engines-list-server@matronics.com] On Behalf Of Hinde,
Frank George (Corvallis)
Sent: Tuesday, October 16, 2007 9:04 AM
Subject: RE: Engines-List: Knock sensors?
<frank.hinde@hp.com>
LOP is the most efficient place to run the motor. From my reading of the
Lycoming power chart it has about a 10% reduction in the BSFC in LOP vs
ROP (BSFC =.45 at 50F LOP and .5 at 80F ROP).
Rumour has it that the only way the old Howard Hughes Connies made it
across the Atlantic was to run the motors LOP.
Its about the only place I run my motor apart from take off and landing.
Frank
RV7a TMX IO360
-----Original Message-----
From: owner-engines-list-server@matronics.com
[mailto:owner-engines-list-server@matronics.com] On Behalf Of Noel
Loveys
Sent: Tuesday, October 16, 2007 7:22 AM
Subject: RE: Engines-List: Knock sensors?
Thanks... I had heard of LOP before long enough ago to have completely
forgotten.
When in technical school we were always told to lean ROP
Noel
Message 5
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| Subject: | Re: 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
-----Original Message-----
From: owner-engines-list-server@matronics.com
[mailto:owner-engines-list-server@matronics.com] On Behalf Of
AzevedoFlyer@aol.com
Sent: Saturday, October 13, 2007 7:00 PM
Subject: Re: Engines-List: Re: 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
Message 6
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| Subject: | Re: Knock sensors? |
I talked with one of the local pilots who was a flight engineer on the Connies.?
They not only operated the engine LOP, they increase the manifold pressure to
recover the power lost by operating LOP.
As Don described it, the sequence went like this to set the cruise power mixture
and power setting.? (They used a power gauge.)
When they leveled out at cruise altitude, the power gauge?showed a number with
the initially rich mixture setting.? They would calculate?a reduced?power setting?by
subtracting 10% or 15% (depending on the supercharger blower being in high
or low blower) from the original power setting.
They would lean the mixture.? As the mixture is leaned, the power gauge would show
an?increase in power, and then show a?decrease in power.
When they got to the lower?calculated power setting, they had the mixture set.
Now they increased the manifold pressure until they reached the original power
setting.
Sounds simple.? Just do this smoothly on four engines at the same?time.? :-)
For our normally aspirated engines, the capability of obtaining the power recovery
isn't there.
I suspect the same power reduction and fuel fow reduction could be done running
Best Economy and reducing the manifold pressure.? Someone interested in doing
a test program?
Regards,
Jim Ayers
-----Original Message-----
From: Monty Barrett Sr <MONTY@bpaengines.com>
Sent: Tue, 16 Oct 2007 8:25 am
Subject: RE: Engines-List: Knock sensors?
The Wright 3350 engines in Super Connies and also the B-29 were operated
LOP. The FE had the most important job on the flight crew. As I
remember,
The FE also had a set of throttles.
Monty Barrett
-----Original Message-----
From: owner-engines-list-server@matronics.com
[mailto:owner-engines-list-server@matronics.com] On Behalf Of Hinde,
Frank George (Corvallis)
Sent: Tuesday, October 16, 2007 9:04 AM
Subject: RE: Engines-List: Knock sensors?
<frank.hinde@hp.com>
LOP is the most efficient place to run the motor. From my reading of the
Lycoming power chart it has about a 10% reduction in the BSFC in LOP vs
ROP (BSFC =.45 at 50F LOP and .5 at 80F ROP).
Rumour has it that the only way the old Howard Hughes Connies made it
across the Atlantic was to run the motors LOP.
Its about the only place I run my motor apart from take off and landing.
Frank
RV7a TMX IO360
-----Original Message-----
From: owner-engines-list-server@matronics.com
[mailto:owner-engines-list-server@matronics.com] On Behalf Of Noel
Loveys
Sent: Tuesday, October 16, 2007 7:22 AM
Subject: RE: Engines-List: Knock sensors?
Thanks... I had heard of LOP before long enough ago to have completely
forgotten.
When in technical school we were always told to lean ROP
Noel
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