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Ring Engine Compression
Greetings,
Ijust purchased a n.i.b. OS.61 SF ring engine that has never been run (ran?) Ihave always had ABC engines and this is my first ringed engine. The engine turns over fine, is in great shape, etc. Idisassembled to verify the "no runtime", and oiled it to make sure everything turns over smoothly. It is obvious this has never run, including break-in. What Ido notice when I install the glow plug is there seems to be very little, almost no compression. Is this normal on a ringed engine? Perhaps the ring needs to seat with a run-in? I did not remove the piston/liner assembly as this is obviously new with the rest of the engine. Before Ifire this up, I wanted to check on this. My ABC version of the .61 SF is an awesome and reliable engine with plenty of compression. Appreciate any feedback. |
RE: Ring Engine Compression
You'll be amazed at what a difference even 5 minutes of slow, rich running will make. In about an hour it should hold compression like an ABC engine does only it will still hold it long after the ABC engine has start to show signs of wear.
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RE: Ring Engine Compression
Great! I was hoping this would be the case. Thanks!
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RE: Ring Engine Compression
Break it in slobbering rich for a while, just the opposite of an ABC engine.
Ernie Misner |
RE: Ring Engine Compression
Thanks Ernie, will do. I guess this is normal not to have a lot of compression (hardly any) on a new ringed engine. Does the ring expand, or simply conform to the cylinder wall?
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RE: Ring Engine Compression
Yes as mentioned already the ringed engines need some run in time to get the ring seated in order to provide the best performance.
One thing to mention is that some engines use a Dykes ring on the piston. This type of ring is located right at the top of the piston. The Dykes ring has low resistance as the piston moved up and down, and when on the combustion cycle the ring is forced outward to seal the cylinder as the piston is heading down. So engines with Dykes rings feel like they have no compression. But usually when you give them a quick strong prop flip, you can feel the ring engaging and the compression increases enough to let the engine fire up and run. The Dykes ring ism a evolutionary development that allowed a piston ring engine to turn higher RPMs than a conventional ringed engine. But even the Dykes ring has a RPM limit too. Then the lapped piston engines with no rings could rev a little higher than a ringed engine as there is no ring to flutter and cause a power loss when the engine reaches a certain peak RPM. Later the tapered cylinders with ABC, ABL, AAC came about, no rings too, and they allow a engine to turn much higher RPMs, up to the engine design limits. |
RE: Ring Engine Compression
That pretty much covers it
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RE: Ring Engine Compression
Wait, there's more! Some ringed engines will appear to have compression when you turn them over in one direction and none or little in the other direction. That's usually the non-pinned rings like in a 4-stroke though and if the gap winds up facing, say to the left, there will be more or less pressure on that side of the piston depending on which direction you are turning the engine over. No kidding!
Ernie Misner |
RE: Ring Engine Compression
Hook it up to a gallon jug of fuel and let it run nice and rich for a good long time.
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RE: Ring Engine Compression
I would rather suggest that after maybe 15 minutes on the ground for initial breakin then fly the plane moderately to get the airflow over the engine cylinder for cooling. Only short bursts at wot increasing until the engine has probably another 5 or 6 flights of 10-12 min each. This has become my practice for the last several years.
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RE: Ring Engine Compression
ORIGINAL: JeffH Hook it up to a gallon jug of fuel and let it run nice and rich for a good long time. While not totally broken in till well after a gallon of fuel is run, I would think two tanks or so would be enough before flying. Set it on the rich side, and be prepared for the compression to be up and down for a gallon of fuel or two. |
RE: Ring Engine Compression
You only need to run a few tanks, two or three maybe, sometimes more to iron out the kinks and get it adjusted reasonably well.
You really need to heat cycle the engine as that helps it run in much faster than simply hooking it up to a gallon of fuel and letting it run non-stop. You want the engine to heat up and cool off. Also at first you want to run the engine for short period of times at a rich full throttle and then back it off to a high idle letting it cool off, then repeat. As the engine gets run in more, the full throttle intervals get longer and longer. Heat cycling is where you run the engine for a few minutes and stop it, let it cool off, then repeat. Some engines, such as the vintage free flight ignition engines from many years ago, only run a small fuel tank for maybe a minute or less and then you let the cool off and repeat the engine run, and so on. You couldn't run these engines very long, especially at first when new. Now with the ABC engines, they basically run them near their top speeds as you need them to heat up and expand the cylinder out straight so the piston doesn't get shrunk down with the swaging effect from the tight taper or pinch in the cylinder. But you still need to run them on the rich side some at first though. |
RE: Ring Engine Compression
In order for the ring to seat properly the engine needs to get up to operating temperature.
Running motors blubbering rich is old school. Modern engines are built to very close tollerences and need very little break in. Too much fuel and it wont create enough friction in the sleeve to properly seat the ring. Run it a little rich for a few flights. Raw fuel pouring out the exhaust does nothing but waste fuel and prolong the break in. |
RE: Ring Engine Compression
Running motors blubbering rich is old school. |
RE: Ring Engine Compression
I would respectfully disagree, though they need to be somewhat rich, pouring raw fuel does nothing.
I've broken in a pile of nitro helicopter engines. Start out a little rich and it will run richer/cooler as the ring starts to seat. You lean it a little as a time until the motor no longer requires tweaking (3-5 tanks depending on oil content of the fuel), then you let it rip. I'm talking engines without a prop blowing on them running at 16-18K so they are operating in a lot harsher environment as an airplane engine. |
RE: Ring Engine Compression
You should run new Saitos as blubbering rich as the manual recommends.
I'm with Earl with heating up non ringed engines quickly. |
RE: Ring Engine Compression
But only for the first 10 minutes on the Saito. I don't run ringed two strokes sloppy wet, just where they break into fourstroke. Then when you fly it, it fourstrokes part time on the level, two strokes in a climb and fourstrokes full time in a dive. I don't break in any engine at the point you need glow power after starting.
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RE: Ring Engine Compression
I run 2 strokes hard after the first minute or two.....depending on how they sound, etc. i use the same rpms like you for each tank on new Saitos, but they get a lot of wide open run time after the first 10 minutes.
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RE: Ring Engine Compression
RTFM - that is the best advice to heed. I have owned and run many OS engines both ringed and ABC, though I am down to just two these days, both ringed, due to thinning out my collection.
Generally speaking, a person who invests in an OS engine does so because they want an engine that will give good service for a long time. That long relationship starts with with the all-important break-in period so getting it right counts for a lot. Ignore the impatient jokers who advocate running too lean too early - if they want to torture their engines to a premature death then that's up to them - that stuff is for cheap 'throw away' ABC engines and people with money to burn. Manuals for most engines can be found online if you didn't get one with the engine. |
RE: Ring Engine Compression
person who invests in an OS engine does so because they want an engine that will give good service for a long time. For longevity try a Enya, Fox, or the older SuperTigre's (not sure about the Chinese versions). For bfreak in just be sure it is very rich, a 4 cycle run is not mandatory but helpfull to prevent overheating. Also read your manufactures instructions as not all engines are the same. |
RE: Ring Engine Compression
You can also consider an engine to be a 'throw away' if the parts are too expensive.
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RE: Ring Engine Compression
I think (ok I'm sure) that if you RTFM from OS it will say they require very little break in.
All internal-combustion engines benefit, to some degree, from extra care when they are run for the first few times known as running-in or breaking-in. This allows the working parts to mate together under load at operating temperature. However, because O.S. engines are made with the aid of the finest modern precision machinely and from the best and most suitable materrials, only a very short and simple running-in procedure is required and can be carried out with the engine installed in the model. |
RE: Ring Engine Compression
ORIGINAL: Sport_Pilot OS is not known for longevity. For longevity try a Enya, Fox, or the older SuperTigre's (not sure about the Chinese versions). The oldest engine I have still in use is an Enya 45 6001 that has two rings - it will probably out-last me! I love my Super Tigres, but have never owned a Fox engine that I can remember... Ringed is the way to go if you want an engine that will last - run it in right http://www.rcuniverse.com/forum/js/f.../thumbs_up.gif |
RE: Ring Engine Compression
ORIGINAL: BarracudaHockey I think (ok I'm sure) that if you RTFM from OS it will say they require very little break in. All internal-combustion engines benefit, to some degree, from extra care when they are run for the first few times known as running-in or breaking-in. This allows the working parts to mate together under load at operating temperature. However, because O.S. engines are made with the aid of the finest modern precision machinely and from the best and most suitable materrials, only a very short and simple running-in procedure is required and can be carried out with the engine installed in the model. |
RE: Ring Engine Compression
That would be an excerpt from a ringed heli engine, they don't vary greatly though.
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RE: Ring Engine Compression
Although heli engines don't have much of a life expectancy - once ranked with buggy and ducted fan engines - a very ditterent operating environment to propped aero engines.
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RE: Ring Engine Compression
Oh dear - OS are definately not the flavour of the month - I have just read about the nickel plating peeling at the 'pinch' in sleeves of some ABN engines.
Thread is; <font size="+1">OS 46FX problem - see pics</font> |
RE: Ring Engine Compression
roojoose- you can find a ton of references to the known peeling problems with the 46 FX if you search RCU via Google or Bing. You will also find numerous pics.
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RE: Ring Engine Compression
ORIGINAL: roojoose ORIGINAL: Sport_Pilot OS is not known for longevity. For longevity try a Enya, Fox, or the older SuperTigre's (not sure about the Chinese versions). The oldest engine I have still in use is an Enya 45 6001 that has two rings - it will probably out-last me! I love my Super Tigres, but have never owned a Fox engine that I can remember... Ringed is the way to go if you want an engine that will last - run it in right http://www.rcuniverse.com/forum/js/f.../thumbs_up.gif |
RE: Ring Engine Compression
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RE: Ring Engine Compression
Nice going, Cap'n, I have retained 6 ABC engines including the first one I ever bought (25 years old now), I just prefer ringed engines.
Most on here would agree that it is the first few runs/tanks/gallons that make or break the longevity of an engine. |
RE: Ring Engine Compression
Next thing based on this logic will be a Cerium Oxide fuel additive to help polish the moving parts into their 'closest fit for max power' Some poeple will believe anything.http://www.rcuniverse.com/forum/js/f...bout_smile.gif |
RE: Ring Engine Compression
Ok ringed model glow engines do not use motorcycle techniques for running in a engine.
The Fox engine methods would apply to most ringed engines though Fox engines have a hardened cylinder sleeve that can take a little longer to get the ring seated against it good. To break in a Fox ringed engine one should run the engine in a four cycle mode. This is because in this condition the cylinder pressure is near the maximum. One needs to develop as much cylinder pressure as is practical to drive the ring into the cylinder. The driving of the ring into the cylinder is what allows the cross hatch in that hard Fox liner to shape the ring to conform to the cylinder bore. The power stroke (cylinder pressure) in the four cycle mode is noticeably higher than in the 2 cycle mode because it has a cleaner and larger inlet charge (more efficient scavenging between firings). Now since the Fox is a sleeved timed engine the heating around the sleeve is not uniform. One needs to thermal cycle the engine to allow the cylinder to reach its final operating shape, rather slowly. A engine is broken in when the piston ring can seal against the cylinder when the cylinder is in its final shape under full power (heat load)! There is no heat treating going on in the metal's grain structure of the ring or in the cylinder just dimensional changes as a result of thermal growth! Now a lapped meehanite iron piston and leaded steal cylinder do go through a stage where the grain structure is changed. But this is due to work hardening not heat treating. Like I've said before; too fast too soon too hot too bad. http://www.pspec.com/breakin.asp But unless you are racing use props more in line with what the engine manufacturer suggests. |
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