Today's Message Index:
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1. 09:21 AM - Fw: Choke versa Parallel Info (TeamGrumman@aol.com)
2. 05:01 PM - Re: Fw: Choke versa Parallel Info (Archie)
3. 05:57 PM - Atkins rotary (Scott Trask)
4. 08:18 PM - Re: Atkins rotary (Archie)
Message 1
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| Subject: | Fwd: Choke versa Parallel Info |
--> Engines-List message posted by: TeamGrumman@aol.com
Sorry to not remember who the race engine Guru is on the Engines List. This
is especially for him and other engine builders.
There is a discussion going on in the Grumman-American (Tiger, Cheetah, etc.
) group on what the effect is on having the cylinders in Lycoming have so much
choke. The discussion also talks about the best ring gap.
Here are a couple of posts. Sorry they are so long.
**** Please give me/us your oppinion, ****
The response needn't be lengthy, I'd just like to know the real skinny (boy,
what does that say about my age?) on this.
Thanks. Gary
Post #1
=A0 Gangster Fast Eddie now owns SR22 with a IO 520N Continental, and asked=20if
he could cross post my cylinder wear reply to the SR 22 list.=A0 I think this
may help Grumman owners further understand the relationship between cylinder
barrel life, and cylinder barrel choke.=A0 Eddie stated that many SR22 engines
need top end work at 400 to 700 hours on their new engines which is the same
think I have noticed since Continentals latest cylinder and piston
revisions. Read below.
Eddie, thanks for the consideration on asking permission to cross post. Feel
free to do so. And since you were so nice to ask, here is the story on your
Continental engine as I see it.
=A0=A0 Continental's are now different then the Lycoming's in regards to
cylinder barrel choke.=A0 The Continental cylinders use to have choke just
like the Lycoming cylinders until they introduced a new piston that has a
steel ring cast into the aluminum piston to form the groove that the top
piston ring fits into. Continental did this because on some high time
engines the piston ring groove in the soft aluminum piston would wear, and
get much wider.=A0 The wide piston ring groove would not give enough support
to the piston ring, and the ring would some times break.=A0 Soon after the
insert pistons were installed some broke their entire heads off.
Continental decided that the piston heads must have been running into the
choked area at the top end of the cylinder before the cylinder heated up,
and expand the choked area to provide a straight cylinder barrel. As a
result of this thinking they reduced their choke to .001"to .0035" maximum
if I remember exactly.=A0 Now when the cylinder is heated up the rings end up
running on a tapered cylinder wall that is larger in diameter up at the top
end where all the heat is then down at the bottom where it is much cooler.
Now just like a worn out choked Lycoming cylinder the rings must expand out
of the ring groove to stay in contact with the larger diameter cylinder at
the top end of the cylinder.=A0 With the rings expanded out of their groove
they do not get the needed support from being in the piston groove fully,
and they roll on the cylinder wall at top, and bottom dead center where the
piston changes direction of travel. All of this ring rolling around causes a
tremendous amount of cylinder barrel, ring, and piston wear.=A0 We have
repaired many low time Continental cylinders because of this.=A0 Many of these
cylinder wear themselves=A0 .005" to .007" oversize in just a few hundred
hours.=A0 We repair these cylinders by over sizing them to P .015", and re
introducing as much choke as possible back into them which is usually around
.006" to .008".=A0 We have had great success with these repaired cylinders,
and they run to TBO with out sucking down oil, or breaking pistons.
=A0=A0 I will also add that aluminum pistons with steel inserts are from the
diesel engine world.=A0 While diesel engines have a lot of compression, and
they subject pistons to high loads they operated about 150 degrees cooler
then a piston in a air cooled engine. I believe it is the different thermal
expansion rates of the aluminum piston, and the steel insert that caused the
top of these pistons to break off.=A0 These pistons were all tested
ultrasonically while being turned to test the joint between the piston and
the insert. An inspector was expected to check each one while viewing a
analog gage for deflection which would indicated a defects. I think they
really need to hook an alarm to it. A Continental engineer stated to me that
it was their new center vented oil control ring that was working to
efficiently causing cylinder wear by not allowing enough oil past it to
lubricated the compression rings. I think that's a bunch of bunk, and told
this engineer that in a heated phone conversation many years ago.=A0 I also
told him that the guy that designed it should be fired, and it turned out to
be him.=A0 A bunch of choice words flowed back, and forth at that point that
were very color full to say the least.
=A0 Based on the above, running a Continental engine a little on the cool side
is the way I would go if you want the cylinder barrels, pistons, and rings
to last.
Time to get back to work, good luck with your new bird.
Bill & Carol Scott
Precision Engine L.L.C.
=A0=A0 In regards to Cliffs posting I would say that a Porsche race car engine,
and how it is operated has little bearing on how an aircraft engine is
operated, and the amount of time it is expected to operate. There are many
mechanical difference between a Porsche engine, and a aircraft engine. A
Porsche engines cylinders are oil cooled, and may have 5 or more oil coolers
on the engine.=A0 A Porsche engine does not run over square pistons like a
Lycoming or Continental, that is pistons that are larger in diameter then
their length, this allows the piston that is not cocking around in the
barrel to support the piston rings much better, and keep the rings from
rolling on the cylinder wall.=A0 The Porsches piston runs with much less
operating clearances with the cylinder barrel then a aircraft engines
piston.=A0 The Porches cylinder barrels have far less thermal expansion as a
result of being oil cooled which allows for the tighter operating clearances
between the piston, and cylinder wall to be acceptable.=A0 Most aircraft
engines run at a steady state cruise power 98 % of their life unlike a
Porsche. There are many more differences between these engines but I do not
have time to write a book.
=A0 Another point I would make is that the top of the cylinder barrel on an
aircraft cylinder is screwed into the aluminum cylinder head, and is
subjected to high temperatures that does cause cylinder barrel expansion.
A cylinder running in a test cell with worn out cylinders with no choke will
produce more power briefly but has no service life.=A0 It is the amount of
time that the top of the cylinder barrel, and the lower part of the cylinder
barrel is exposed to combustion heat that determines the thermal expansion
of the barrel at different stations.=A0 The piston shields the lower part of
the cylinder barrel from the heat of combustion almost all the time compared
to how it shields the top of the cylinder barrel from heat very briefly.=A0=20A
firm understanding of how long the piston shields various stations of the
cylinder wall from heat, and its effect on thermal expansion at each station
is that's important.=A0 The=A0 cylinder barrels choke profile must be designed
with the cylinder barrels temperature hence thermal expansion in mind at
various barrel stations if you want to have straight cylinder barrels for
your piston, and rings to run on at operating temperatures.
Ya, one of those WASG's. Thanks to all that told me what this means, I
laughed so hard I had tears in my eyes, and my chubs hurt=A0=A0 :-)
Bill & Carol Scott
Precision Engine L.L.C.
Post #2
data, other than articles by John Deakin, such as
http://www.avweb.com/news/columns/182155-1.html
He states, in part:
During the past 15 years or so, quite a number of people (including me) have
come to the following conclusions:
1) Engines built by TCM prior to about 1991 usually ran to (and beyond) full
TBO without much work on the cylinders.
2) Engines (and cylinders) built during or after the 1991 strike at TCM have
consistently suffered from seriously excessive premature cylinder problems,
with very few making more than about 500 hours.
There was a VERY interesting account of three Bonanzas which all required
cylinder work at low total time. It's not coming up on a Google search - it
did
before, so maybe it got pulled.
In any case, I have the article as a text file if anyone is interested.
Post #3
Ok Gang,=A0 Bill Scott is on the right track about cylinder heat expansion.=A0
He
will also tell you that we did not agree on this subject in the past and it's
never too late to learn and there is still much to be learned on this
subject.
=A0=A0 He has mentioned to me that the curve is much too radical at the top=20and
this I full agree with him on.=A0 This may be the real problem, I don't like it
at all.=A0 In my opinion it shoul be a more gradual curve at the top so it does
not jam the piston and rings so quickly.=A0 For me trhe way I look at the
problem
or I should say all engines do not need or should need the same choke
profile.=A0 As Scott says the piston wobble is where the trouble lies. Now how
do you
keep that piston from doing that.=A0 One thing Ill gurantee and that is never
to
reuse an old piston on rebuild.=A0 Oh! I beed blast and they are OK, Bull ain't
so, ring groove wear will definately let the rings roll and flop. There goes
your TBO. My old chrome cylinders have have ring flop grooves at the top very
bad and some at the bottom where that piston reverses.=A0 We don't want any=20at
all and there is a reason for it and untill we get rid of this problem we'll
have early black oil and heavy carbon before the 25 hours is up.=A0 Why do we
have
these flop grooves? WHY !!! I don't see this problem as bad in Continental as
bad as I do in Lycoming.=A0 Continental did use a 4 ring piston same as the=20Lyc
C2C.=A0 I.ve lost track on Continental because I don't work on them any more
because I'm a Pratt man not a Wright.=A0 All the C2 engines used the 4 ring
piston
or did but but a lot are changing over to the L2C 3 ring design.=A0 The 4 ring
piston in my opinion in the C group give better give better ring support both
at the top and bottom of the stroke.=A0 C design engines are not hi-performance
but longivity engines.=A0 The C-152 change cylinder like popping pop corn.=A0 I
gave up telling the training out fit its time to change a jug when I see that
prop jerk to stop on shut down=A0 Many times was ask how I knew that engine=20was
going to fail in flight.=A0 Just psychic, can just feel it in my bones.
=A0=A0 I'de like to have the Nye Squirts in my block but can't that.=A0 Oil=20does
cool and the more you have in the right place up to a point the cooler that
engine will run.=A0 Every now and then some one will call me and said some
IDIOT put
the bottom ring in up side down but i fixed it and put it it correct.=A0 Wrong
son!=A0 it was designed that way but if you call Lycoming like I did they say
it
doesn't matter.=A0 Wrong again like I told them tey were installing slotted=20key
siuntered iron in the oil pumps in 71 and up engines.
=A0=A0 Take note guys & gals in the past engineers ran engines loose and ring gap
of about .020 to .030 was the standard in those days but the California
pollution people design laws have changed all of that.=A0 Briggs Stratten,
Honda,
Kohler and ECI all say .007 is now it and live with it.=A0 Briggs Warrany
records
skyrocketed and this made me a lot of money for Auto Fuel for my little Ratty
airplane. But not any more due to health problems that will not let me work
like this any more.=A0 Members have chewed me out and told to quit cheating=20the
people and to write again.=A0 Fellow typing expert I'm using a dictionary,=A0
hope
I'm improving.=A0 So the big question is what=A0 are we going to do about the
radical curve and the tight ring gap now?=A0 Well Bill Scott is trying and he's
young
and can carry on=A0 Bill did you wver get that ignition on your speed wagon=20I
flew for you at Butter-Fly Ville.=A0 Your wife said you had better.
=A0=A0 I look for Lycomining to go for the Nye Jet spray and Roller Rockers=20would
help also.=A0 I'm not a Mechanical Engineer but Electronic Engineer.=A0 Still I
wiil not run .007 ring gap on my engines=A0 .010 does fine for my break in's=A0
Make sure you use Meneral for the full 25 hour first in.=A0 And a lot of you
know
I'm a Marvey Mystery nut also love Av-Blend.=A0 Don't dare put any of this
stuff
in that engine makes break in.=A0 I like my rings to seat in the first 10
hours,
one did at 5 on a new cylinder and one went 20 on a chrome.=A0 Change that oil
at twenty five hours or any time the oil lite comes on to get that fine metal
out, take my word you can't see it but it's there.
=A0=A0 Guess I've used enought space
=A0 Fly safe, see & avoid.=A0 Love Yaa, E-Gap
From: FlyinFever@aol.com
Subject: Fwd: Choke versa Parallel Info
From: RandallWH@aol.com
Subject: Choke versa Parallel Info
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Ok Gang, Bill Scott is on the right track about cylinder heat expansion. He
will also tell you that we did not agree on this subject in the past and it's
never too late to learn and there is still much to be learned on this subject.
He has mentioned to me that the curve is much too radical at the top and
this I full agree with him on. This may be the real problem, I don't like it
at all. In my opinion it shoul be a more gradual curve at the top so it does
not jam the piston and rings so quickly. For me trhe way I look at the problem
or I should say all engines do not need or should need the same choke
profile. As Scott says the piston wobble is where the trouble lies. Now how do
you
keep that piston from doing that. One thing Ill gurantee and that is never to
reuse an old piston on rebuild. Oh! I beed blast and they are OK, Bull ain't
so, ring groove wear will definately let the rings roll and flop. There goes
your TBO. My old chrome cylinders have have ring flop grooves at the top very
bad and some at the bottom where that piston reverses. We don't want any at
all and there is a reason for it and untill we get rid of this problem we'll
have early black oil and heavy carbon before the 25 hours is up. Why do we have
these flop grooves? WHY !!! I don't see this problem as bad in Continental as
bad as I do in Lycoming. Continental did use a 4 ring piston same as the Lyc
C2C. I.ve lost track on Continental because I don't work on them any more
because I'm a Pratt man not a Wright. All the C2 engines used the 4 ring piston
or did but but a lot are changing over to the L2C 3 ring design. The 4 ring
piston in my opinion in the C group give better give better ring support both
at the top and bottom of the stroke. C design engines are not hi-performance
but longivity engines. The C-152 change cylinder like popping pop corn. I
gave up telling the training out fit its time to change a jug when I see that
prop jerk to stop on shut down Many times was ask how I knew that engine was
going to fail in flight. Just psychic, can just feel it in my bones.
I'de like to have the Nye Squirts in my block but can't that. Oil does
cool and the more you have in the right place up to a point the cooler that
engine will run. Every now and then some one will call me and said some IDIOT
put
the bottom ring in up side down but i fixed it and put it it correct. Wrong
son! it was designed that way but if you call Lycoming like I did they say it
doesn't matter. Wrong again like I told them tey were installing slotted key
siuntered iron in the oil pumps in 71 and up engines.
Take note guys & gals in the past engineers ran engines loose and ring gap
of about .020 to .030 was the standard in those days but the California
pollution people design laws have changed all of that. Briggs Stratten, Honda,
Kohler and ECI all say .007 is now it and live with it. Briggs Warrany records
skyrocketed and this made me a lot of money for Auto Fuel for my little Ratty
airplane. But not any more due to health problems that will not let me work
like this any more. Members have chewed me out and told to quit cheating the
people and to write again. Fellow typing expert I'm using a dictionary, hope
I'm improving. So the big question is what are we going to do about the
radical curve and the tight ring gap now? Well Bill Scott is trying and he's young
and can carry on Bill did you wver get that ignition on your speed wagon I
flew for you at Butter-Fly Ville. Your wife said you had better.
I look for Lycomining to go for the Nye Jet spray and Roller Rockers would
help also. I'm not a Mechanical Engineer but Electronic Engineer. Still I
wiil not run .007 ring gap on my engines .010 does fine for my break in's
Make sure you use Meneral for the full 25 hour first in. And a lot of you know
I'm a Marvey Mystery nut also love Av-Blend. Don't dare put any of this stuff
in that engine makes break in. I like my rings to seat in the first 10 hours,
one did at 5 on a new cylinder and one went 20 on a chrome. Change that oil
at twenty five hours or any time the oil lite comes on to get that fine metal
out, take my word you can't see it but it's there.
Guess I've used enought space
Fly safe, see & avoid. Love Yaa, E-Gap
Message 2
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| Subject: | Re: Fwd: Choke versa Parallel Info |
--> Engines-List message posted by: "Archie" <archie97@earthlink.net>
As I have read a portion of the messages, I see a number of
opinions, many quite valid. Obviously, we are dealing with
procrastinating manufacturers, and feds afraid to lose their
retirement over making a common sense decision, I will
add info from our realistic racing technology scenario.
As far as I am concerned, choke, and the amount of it, is
moot. We tried that years ago in racing, caused more
problems than it solved, and was not worth the effort.
Theoretically it should have helped, but it did not.
As far as ring gaps are concerned, the optimum gaps
are obtained through blood, sweat, and tears.
Each engine takes on it's own individual personality,
even if it is a clone. This inclusive, gaps are determined
on the dyno, (for the most part), and are initially set at
less than the manufacturer's recommended minimum,
run through numerous pulls under varying conditions,
then removed for inspection.
The minimum gap is determined when the ring ends
indicate signs of "butting wear".
The trend is now heading toward modified steel rings,
as opposed to cast iron.
Archie
Message 3
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(not processed: message from valid local sender)
--> Engines-List message posted by: Scott Trask <sctrask@diisd.org>
Hi
I'm looking at Atkins rotary engine with Powersport's gear box on it. Looks
like it would be a nice engine. What you think?
Scott RV 7A
Message 4
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| Subject: | Re: Atkins rotary |
--> Engines-List message posted by: "Archie" <archie97@earthlink.net>
> --> Engines-List message posted by: Scott Trask <sctrask@diisd.org>
>
> Hi
> I'm looking at Atkins rotary engine with Powersport's gear box on it.
Looks
> like it would be a nice engine. What you think?
> Scott RV 7A
Atkins has a nice setup.
The powersport redrive is nice, but a bit pricey.
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