ABC engines vs. Ringed: Which is better?
Terrantula
performance:
Subj: Ring .vs. AAC & ABC
Date: 95-12-12 06:59:36 EST
From: BENN...@mailgate.navsses.navy.mil
To: Terra...@aol.com
Terry - This one is a pretty open & shut case. Every single model engine
on the planet will benefit from a properly set up AAC or ABC liner /
piston assembly. Rings are in a constant state of blowby, reheating the
fresh incoming charge, further reducing performance. Some ABC / AAC are
better than others. You must have the proper liner taper to get the
perfect seal at TDC, good real chrome plating (OS electroLESS Nickel
SUCKS!!!), and good high silicon content piston alloy.
This is why I base all of by OS heli engine tuning around the Performance
Specialties (Nelson) AAC and ABC pistons and liners.
Take a good AAC / ABC assembly with oil in it, crank it up to TDC by
hand, hold it there for a bit and there will be zero comparison to this
same test with a ring. Pssffffttt goes the ring! Now add in the actual
high pressure combustion when running, and it is no contest.
Even though the AAC / ABC might feel a bit tight at TDC due to the liner
taper, especially when new, the hot film of oil has no chance to be
squeegeed away at operating speeds. This is why properly run &
maintained AAC / ABC will last a very long time compared to the ring.
- Bruce
Please note: If you want to respond to Bruce directly, please use his
email address, BENN...@mailgate.navsses.navy.mil. If you simply hit the
reply to message button in your software, your comments will go to me.
Thanks,
Terry Gamble,
Phx, AZ
Terrantula
Since it's a dark and snowy night (well actually it's beautiful here, but
it must be dark and snowy somewhere), let's start a discussion on the
relative merits of ABC engines vs. ringed engines, particularily as it
relates to beginners and entry level 40 size engines. Since it was my
idea, I get to go first!
My personal opinion runs counter to conventional opinion. I favor ABC
engines over ringed engines for beginners. Part of my reasoning is because
of where I live and fly.
The traditional argument in favor of ringed engines for beginners goes
something like this: Ringed engines are more tolerant of dirt and debris.
The ring literally cleans some of the grit off the side of the cylinder
wall, and the cylinder walls are less likely to be scored. (It's the ring
that's usually damaged) In the event of severe dirt ingestion, you can
always replace the ring. Also, ringed engines are a proven technology.
There are several examples of reliable, proven ringed engines to choose
from.
Suprisingly, it's because I fly in a very dirty environment that I have
developed a preference for ABC engines. Where I fly, the nearest blade of
grass is miles away, and we take off and land literally in the dirt and
sand. Each crash is a grit ingestion festival. Then why would I favor
ABCs? It's because after each crash the engine must be disassembled to be
cleaned out anyway. To proceed without a thorough cleaning would be to
commit engine suicide, even with a ringed engine.
Although not a big deal for an experienced modeler, ABC engines are easier
for a beginner to take apart and clean without hurting anything. Simply
remove the carb, head and backplate, and slide the sleeve right out of the
engine. The piston, crank, and bearings can be left in place. Everthing's
exposed enough to be thoroughly cleaned out and oiled. Reassembly is a
snap because there are no worries about recompressing the ring. I realize
that In some areas of the country people rarely disassemble their engines,
and in fact, many are afraid to. Out here, it's a matter of necessity. I
just sold the engine off my original trainer, and it had been taken apart
and cleaned 15 or 20 times.
ABC engines typically require little break in, and it can usually be done
right on the plane. Ringed engines sometimes require extensive bench time
to be broken in properly. Example...I just put a new Super Tigre GS .45 on
my son's airplane. Break in was accomplished on the plane. It only took
about 3/4 tank of fuel for the engine to settle down and develop a smooth
high power setting. We then set the low speed needle, and he was flying.
The engine hasn't missed a lick and though I'll probably readjust it after
a couple more hours in the air, it shows no signs of needing it yet.
ABC engines are more tolerant of being run over lean, something a beginner
is more apt to do. When a ringed engine gets too hot, the engine usually
seizes and you wind up with a varnished cylinder or worse a broken ring or
scored cylinder. When an ABC engine gets too hot, the piston enlarges to
the point where you get a noticable sag in RPMs. This is easier to
recognize and correct, and in any event, the piston usually frees up as
soon as the engine cools, with no obvious problems. (I'm sure it doesn't
do the engines any good, but they're usually ready to fly after they've
cooled and the mixture has been reset.)
So, ABC engines are easier to take apart and clean, easier to break in,
and more tolerant of being run too lean. What more could a beginner want?
(Also note: The entry level engine from all manufacturers, including OS,
is an ABC engine. I don't think cost to manufacture alone is the reason.
If there were a significant advantage to ringed engines, I think one of
them would have jumped on the bandwagon.)
So what do you guys think? Am I crazy? I have taken the liberty of getting
a reply in advance from Bruce Bennett, our performance engineer in
residence. I will post it separately, so as to minimize the chance
Robert Adkins
>
> Hi all!
> engines over ringed engines for beginners. Part of my reasoning is because
> of where I live and fly.
>
> The traditional argument in favor of ringed engines for beginners goes
> something like this: Ringed engines are more tolerant of dirt and debris.
Spider Guy..:-)
I must agree. Most ABC engines are broken in enough to be reliable after
a tank or 2 of fuel, and withstand dust well. Large grit is murder,
though.
Due to the low friction, they produce more power and run cooler. The ones
I have never feel the sting of the electric starter. A flip or 2 with a
chicken stic starts them reliably.
I think the "conventional" wisdom comes from older guys that accept new
technology slowly. I always recommend recommend an ABC engine for
beginners that can afford them.
Your partner "hates ABN". I have found that as long as you don't inhale
any sand-size stuff, that they act exactly like ABC. I have an OS FP .25
ABN with a mousse can muffler that turns a 9x6 prop at 14000 RPM and has
over 700 flights on it! And the RPM has never dropped from new! And ABN
breaks in easier than ABC. Now, if there were any weaknesses in the
plating process such as thin areas, contamination, etc...then ABN will
fail very early. If you get 20 strong runs, then you will get great life
from ABN. I DO prefer ABC...But ABN is 99.5% as good.
So...don't feel that recommending ABC for beginners makes you a radical.
I recommend AILERONS for beginners, and with LOTS of throw! I also eat
rare chicken....(kidding 'bout the chicken) Now I'm a radical!
Bob
Paul Zirwes
terra...@aol.com (Terrantula) wrote:
> The traditional argument in favor of ringed engines for beginners goes
> something like this: Ringed engines are more tolerant of dirt and debris.
> The ring literally cleans some of the grit off the side of the cylinder
> wall, and the cylinder walls are less likely to be scored. (It's the ring
> that's usually damaged) In the event of severe dirt ingestion, you can
> always replace the ring. Also, ringed engines are a proven technology.
> There are several examples of reliable, proven ringed engines to choose
> from.
I read this argument before I purchased my OS 60 FP ABC engine. Dirt
is a major concern, since I fly off off dirt fields at least half of
the time. Instead of taking the performance loss (and added part
count) of a ringed engine, I spent $2 on a Bru-Line air filter and a
few more on a Final Fuel Filter. Logic would dictate that dirt isn't
good inside ANY engine, be it ringed or ABC.
> Suprisingly, it's because I fly in a very dirty environment that I have
> developed a preference for ABC engines. Where I fly, the nearest blade of
> grass is miles away, and we take off and land literally in the dirt and
> sand. Each crash is a grit ingestion festival. Then why would I favor
> ABCs? It's because after each crash the engine must be disassembled to be
> cleaned out anyway. To proceed without a thorough cleaning would be to
> commit engine suicide, even with a ringed engine.
When I "trimmed" my Right Flyer 60 into the ground, nose first, there
was a ugly mess of sand, dirt and fuel all over my engine. I put my
thumb over the air filter and sprayed the whole thing down with
alcohol, which got almost everything off the external engine. When I
opened up the carb and crank, there wasn't a speck of dirt in sight.
My Right Flyer is now repaired and back in action, with the same OS 60
FP engine cranking me happily through loops and rolls.
> Although not a big deal for an experienced modeler, ABC engines are easier
> for a beginner to take apart and clean without hurting anything. Simply
> remove the carb, head and backplate, and slide the sleeve right out of the
> engine. The piston, crank, and bearings can be left in place. Everthing's
> exposed enough to be thoroughly cleaned out and oiled. Reassembly is a
> snap because there are no worries about recompressing the ring. I realize
> that In some areas of the country people rarely disassemble their engines,
> and in fact, many are afraid to. Out here, it's a matter of necessity. I
> just sold the engine off my original trainer, and it had been taken apart
> and cleaned 15 or 20 times.
The first thing I did when I bought my engine was disassemble it
(excluding the piston) and inspect it for any metal shavings, etc,
that might still be there from the manufacturing process. It was a
snap and I had never disassembled an engine before! Many people
suggested I buy an OS FP class engine because they are reliable, easy
to start, break-in and tune, and (if properly cared for) will last a
long time. I know several people who have run their FP engines for
years, and others who seem to replace their (non-FP) bearings or rings
every season. If simplicity, reliability, and reasonable performance
are important, the OS FP class ABC engine seems to be the best bet
around. To me, reliability is more important than brute power at this
stage of the game.
Still I wonder how my Right Flyer would hover with an OS 61 Hanno...
;)
Have fun,
Paul
----
************************************************************************
From high in the mountains above San Diego . . .
* _O_ Paul Zirwes
*** : InfoCenter Systems, Inc.
^ ***** ! / \ Julian, CA
^^^ ******* !!! +++ ========================
^^^^********!!!!! ++++++ pzi...@cts.com
**********************************************************
(c)1995 by Paul A. Zirwes, All Rights Reserved
Pippen
: My personal opinion runs counter to conventional opinion. I favor ABC
: engines over ringed engines for beginners. Part of my reasoning is because
: of where I live and fly.
: Although not a big deal for an experienced modeler, ABC engines are easier
: for a beginner to take apart and clean without hurting anything. Simply
: remove the carb, head and backplate, and slide the sleeve right out of the
: engine. The piston, crank, and bearings can be left in place. Everthing's
: exposed enough to be thoroughly cleaned out and oiled. Reassembly is a
: snap because there are no worries about recompressing the ring. I realize
: that In some areas of the country people rarely disassemble their engines,
: and in fact, many are afraid to. Out here, it's a matter of necessity. I
: just sold the engine off my original trainer, and it had been taken apart
: and cleaned 15 or 20 times.
: ABC engines typically require little break in, and it can usually be done
: right on the plane. Ringed engines sometimes require extensive bench time
: to be broken in properly. Example...I just put a new Super Tigre GS .45 on
: my son's airplane. Break in was accomplished on the plane. It only took
: about 3/4 tank of fuel for the engine to settle down and develop a smooth
: high power setting. We then set the low speed needle, and he was flying.
: The engine hasn't missed a lick and though I'll probably readjust it after
: a couple more hours in the air, it shows no signs of needing it yet.
: ABC engines are more tolerant of being run over lean, something a beginner
: is more apt to do. When a ringed engine gets too hot, the engine usually
: seizes and you wind up with a varnished cylinder or worse a broken ring or
: scored cylinder. When an ABC engine gets too hot, the piston enlarges to
: the point where you get a noticable sag in RPMs. This is easier to
: recognize and correct, and in any event, the piston usually frees up as
: soon as the engine cools, with no obvious problems. (I'm sure it doesn't
: do the engines any good, but they're usually ready to fly after they've
: cooled and the mixture has been reset.)
: So what do you guys think? Am I crazy? I have taken the liberty of getting
: a reply in advance from Bruce Bennett, our performance engineer in
: residence. I will post it separately, so as to minimize the chance
I think you make a lot of sense! I bought a ST GS45 and loved every
revolution! It's a great engine and has loads of power. However, I think
one has to be careful WHICH ABC engine to get. OS makes "ABC-type"
engines, not true ABC. I've got an OS 46SF ABC which has a worn liner
that costs a bomb to replace. Apparently, the liner has not been coated
by the material a true ABC liner should have.
So, do be careful which ABC engine you get. Hope this helps! Enjoy...
Ian Maclaughlin
>. I have an OS FP .25
>ABN with a mousse can muffler that turns a 9x6 prop at 14000 RPM ....
Bob- This is a bit off topic, but I am intrigued by a 25 FP that will
turn a 9X6 at 14,000 rpm. A 40 SF will barely turn a Zinger 9X6 at
14,000 with the stock muffler, so you seem to be getting power in the
same league. The 40 FP will max out at about 12,500 with the same
prop. What prop brand and fuel do you use?
Ian
San Diego
Robert Adkins
>
> Robert Adkins <"bobad@usa"@pipeline.com> wrote:
>
> >. I have an OS FP .25
> >ABN with a mousse can muffler that turns a 9x6 prop at 14000 RPM ....
>
OHHHH! SORRY! :-o
Naturally, I meant a 9x5!
This is still pretty strong though, wouldn't you say?
In fact, I have 2 of them. One turns 13,800, the other 14,000.
For such a light little guy - only 9.75 Oz for the motor, pipe, prop,
spinner nut, and pipe assy - it really hums!
The stinger in the end of the pipe is only .187 (3/16 in) and I still
use the tiny little stock air bleed carb!
What a little killer for only $85 dollars for engine and homemade pipe.
Again, sorry for the slip......But maybe, with a little port work....who
knows?
Bob
Bill Webster
june...@temasek.teleview.com.sg (Pippen) wrote:
> I think you make a lot of sense! I bought a ST GS45 and loved every
> revolution! It's a great engine and has loads of power. However, I think
> one has to be careful WHICH ABC engine to get. OS makes "ABC-type"
> engines, not true ABC. I've got an OS 46SF ABC which has a worn liner
> that costs a bomb to replace. Apparently, the liner has not been coated
> by the material a true ABC liner should have.
>
> So, do be careful which ABC engine you get. Hope this helps! Enjoy...
Did you know that there are several places in the US where you can send
your piston/liner to have it re-chromed/re-fitted?
Engine Rework:Bob Oge, 34 W.833 S.
James, St. Charles, IL 60174, (312)
888-2289
Performance Model Parts,Inc..
Clen Dye, 12233 S.1565 E. Draper,UT
84020, (801)571-7017
Pro-Stunt Products: Windy Urtnowski
9 Union Ave., Little Ferry, NJ07643
George Aldrich (sp) also does re-chroming.
Typical .40 size job is around $30, much less than a new piston/sleeve.
regards.
--
Bill Webster WWEB...@BNR.CA
Ian Maclaughlin
>Hi all!
>Since it's a dark and snowy night (well actually it's beautiful here, but
>it must be dark and snowy somewhere), let's start a discussion on the
>relative merits of ABC engines vs. ringed engines, particularily as it
>relates to beginners and entry level 40 size engines. Since it was my
>idea, I get to go first!
>My personal opinion runs counter to conventional opinion. I favor ABC
>engines over ringed engines for beginners. Part of my reasoning is because
>of where I live and fly.
>The traditional argument in favor of ringed engines for beginners goes
>something like this: Ringed engines are more tolerant of dirt and debris.
>The ring literally cleans some of the grit off the side of the cylinder
>wall, and the cylinder walls are less likely to be scored. (It's the ring
>that's usually damaged) In the event of severe dirt ingestion, you can
>always replace the ring. Also, ringed engines are a proven technology.
>There are several examples of reliable, proven ringed engines to choose
>from.
>Suprisingly, it's because I fly in a very dirty environment that I have
>developed a preference for ABC engines. Where I fly, the nearest blade of
>grass is miles away, and we take off and land literally in the dirt and
>sand. Each crash is a grit ingestion festival. Then why would I favor
>ABCs? It's because after each crash the engine must be disassembled to be
>cleaned out anyway. To proceed without a thorough cleaning would be to
>commit engine suicide, even with a ringed engine.
>Although not a big deal for an experienced modeler, ABC engines are easier
>So, ABC engines are easier to take apart and clean, easier to break in,
>and more tolerant of being run too lean. What more could a beginner want?
>(Also note: The entry level engine from all manufacturers, including OS,
>is an ABC engine. I don't think cost to manufacture alone is the reason.
>If there were a significant advantage to ringed engines, I think one of
>them would have jumped on the bandwagon.)
>So what do you guys think? Am I crazy? I have taken the liberty of getting
>a reply in advance from Bruce Bennett, our performance engineer in
>residence. I will post it separately, so as to minimize the chance
Terry, you are the all time champ at starting interesting threads of
discussion! I'm pretty much in agreement with you and Bruce, that ABC
is a better choice than ringed. Piston rings exist for one reason:
the aluminum alloy piston is undersize to allow for thermal expansion
that occurs at a faster rate than the expansion of the steel liner,
and the ring is needed to seal the gap. If engines can be built
without the excess clearance for the piston, there is no need for the
ring(s); ergo, the AAC, ABC, ABN, etc. construction. With liner
expansion occuring at the same rate as piston growth, the minimum
required clearance is maintained. This has been an evolutionary
process: Engines with iron pistons in steel liners did not need
rings. Aluminum pistons offered lower reciprocating mass, hence a
route to more power via higher rpm, but with them came the need for
rings, as noted above. ABC is at the top of the chain, its primary
purpose being to get rid of the sloppy piston fit and the need for the
pesky ring. As a practical matter governing choices, there just
aren't many .40 engines being offered with ringed construction these
days.
I would guess that about 8 out 10 beginners start with an OS 40FP
and an ARF trainer such as the the Tower Trainer 40. The 40 FP well
deserves its popularity, needing little or no break-in, easily flip
starts, the tiny carb bore minimizes fuel draw problems, etc. But,
what do you do with it after hanging up the trainer? Now one becomes
increasingly aware that this nearly idiot-proof engine that served so
well in that first airplane just doesn't have the grunt to haul a
sportier aircraft around.
There is still the retro option of a lapped iron piston in a steel
liner, and I think it can be a very good choice, particularly where
beginners are concerned. Fox and Enya still make them, and their
performance to cost and performance to weight ratios put most of the
ABC offerings to shame. Take the Fox for example. Can be had for
around $60 for the plain bearing version, about $10 more if you think
ball bearings are worth the hassle. Weight is 3/4 oz more than the
OS FP, putting it in 2nd place among all .40's, by a small margin.
Power exceeds the OS FP by a whopping 30-40 % at all speeds, and this
is where it really shines. To top that in the sport .40 engine class
(we aren't talking Jett or Nelson here) you are into a Webra or Rossi
at about 3 times the price. As for durability - this is basically the
venerable Combat Special with an R/C carb. These engines have
rototilled the flying field at 120 mph and then been bolted to a new
airframe for the next match. If you do break it, nobody responds with
service or repair parts better than Fox. All in all, this is an
engine you will use long after the trainer has been forgotten.
Disadvantages? It isn't idiot proof. It requires break-in. It may
need a dab of RTV to seal a gasket surface, or short length of fuel
tubing to seal the needle valve. If run overly lean, the piston may
sieze. The weight of the piston causes a bit more vibration than some
ABC engines. It isn't as pretty as the Japanese engines. In short, it
takes more care and understanding than a modern ABC engine like the
OS. But then, a Harley Sportster takes more care and understanding
than a Honda moped, doesn't it?
Bob
better?>, 'i...@nosc.mil (Ian Maclaughlin)' wrote:
>Robert Adkins <"bobad@usa"@pipeline.com> wrote:
>
>>. I have an OS FP .25
>>ABN with a mousse can muffler that turns a 9x6 prop at 14000 RPM ....
>
a
>9X6 at 14,000 rpm. A 40 SF will barely turn a Zinger 9X6 at 14,000 with
the
>stock muffler, so you seem to be getting power in the same league. The 40
FP
>will max out at about 12,500 with the same prop. What prop brand and fuel
do
>you use? Ian
>San Diego
Terribly sorry for any confusion I may have caused! Of course, I was one
pitch
off! I have 2 FP-.25 engines with mousse can mufflers, one gets 13,600
and
one gets 14,000 RPM......
BUT WITH A *9x5* PROP.
I use an APC 9x5 and 10 or 15% Red Max 18% castor.
I used to have an FP .40. Put a mousse can muffler and APC 9x7, got 13000
RPM.
Now use a Webra Speed .32 GT on that plane. Get 14,500 with APC 9x6. Same
weight as the FP .40, but really screams.
Again, sorry for the confusion.
Bob