ring/no ring
09-14-2004 | 09:42 PM
#1
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From: Round Rock,
TX
ring/no ring
It's probably a question that has been asked before, but I'll ask anyway. I noticed that OS offers ringed and non-ringed glow engines of even the same series. I'm assuming that the non-ringed engines have the tapered sleeve/cylinder instead. I'm assuming the ringed engines have piston rings like that in a car engine. Right? Because there are both types of engines, there must be advantages to both. Right? Help me out here; what are the advantages of both? Or of one type over the other? Why are both types of engines out there? Thanx. Jim
09-15-2004 | 07:21 AM
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RE: ring/no ring
There are basically 3 types of engine designs from the ring-non-ring category. One is a ringed engine. Two is the older, rarely seen anymore, steel sleeve-iron piston design and three is the plated brass or aluminm sleeve with a silicone doped, aluminum piston. This 3rd type is most prevalent now.
The ABC type was invented by Super Tigre back in the 1960s for their control line speed engines. The idea was to make the sleeve expand more with heat than the piston so the engine didn't seize during a lean run.
Years later as RC became more popular, we had, and have, many, many people with virtually no engine experience trying RC. This caused a problem with regard to break-in. All of us who have been flying for years know that the key to a good running and long lasting engine is the break-in. Newbies, who know nothing about model engines, literally refuse to break in an engine. The manufacturers have simplified and cut down their break-in instructions to the bare minimum and still people won't do it. If you read between the lines in the engine forum, you will find people asking about break-in and they are implicitly begging someone, anyone, to tell them to forget it, drop the darn engine in a plane and go fly.
For this reason, in my opinion, the ABC type is used for the popular engines. Face it, an ABC engine, for the most part, is bullet proof as long as you don't run it in a rich, 4-cycle at first or run it so lean you fry the piston. If you crank up an ABC type, lean it out until it breaks into a 2-cycle and hold this for a minute or so, you are safe to fly. It's a manufacturer's dream. Let 'em crank up and go fly, they won't hurt it.
I break mine in on a bench, cycling the speed to let it cool between successive full throttle runs, but I know people who run even a half tank through a new engine and fly. Maybe theirs doesn't run quite as well as mine or last quite as long, but before they are worn out, the guy has already bought a newer one. Sure it takes several tanks for the idle to come around to a nice tick-over, but that's life in RC with a new engine.
Larger and more expensive engines and 4-strokes area different story. These guys need a break-in, running rich or you are going to do damage. The manufacturers hope that you could normally expecy someone buying an expensive engine to pay more careful attention to the break-in instructions.
I do worry about the new OS FL-70 that is non-ringed. I looked at their fuel tnk set-up with upper and lower pressure lines and another line from the muffler to the crankcase. The bearings of a 4-stroke get lubrication from fuel that blows by the piston ring to the crankcase. With an ABC type, you don't get much of this. I think this is what the muffler-to-crankcase line is for, to let residual ol in the exhaust to travel back to the crankcase to lube the bearings and lower end. I feel if you don't connect this up properly and use it as a vent, oil drain, as on other 4-strokes, you have a disaster waiting to happen, a potential lower end failure. Maybe I'm wrong.
The ABC type was invented by Super Tigre back in the 1960s for their control line speed engines. The idea was to make the sleeve expand more with heat than the piston so the engine didn't seize during a lean run.
Years later as RC became more popular, we had, and have, many, many people with virtually no engine experience trying RC. This caused a problem with regard to break-in. All of us who have been flying for years know that the key to a good running and long lasting engine is the break-in. Newbies, who know nothing about model engines, literally refuse to break in an engine. The manufacturers have simplified and cut down their break-in instructions to the bare minimum and still people won't do it. If you read between the lines in the engine forum, you will find people asking about break-in and they are implicitly begging someone, anyone, to tell them to forget it, drop the darn engine in a plane and go fly.
For this reason, in my opinion, the ABC type is used for the popular engines. Face it, an ABC engine, for the most part, is bullet proof as long as you don't run it in a rich, 4-cycle at first or run it so lean you fry the piston. If you crank up an ABC type, lean it out until it breaks into a 2-cycle and hold this for a minute or so, you are safe to fly. It's a manufacturer's dream. Let 'em crank up and go fly, they won't hurt it.
I break mine in on a bench, cycling the speed to let it cool between successive full throttle runs, but I know people who run even a half tank through a new engine and fly. Maybe theirs doesn't run quite as well as mine or last quite as long, but before they are worn out, the guy has already bought a newer one. Sure it takes several tanks for the idle to come around to a nice tick-over, but that's life in RC with a new engine.
Larger and more expensive engines and 4-strokes area different story. These guys need a break-in, running rich or you are going to do damage. The manufacturers hope that you could normally expecy someone buying an expensive engine to pay more careful attention to the break-in instructions.
I do worry about the new OS FL-70 that is non-ringed. I looked at their fuel tnk set-up with upper and lower pressure lines and another line from the muffler to the crankcase. The bearings of a 4-stroke get lubrication from fuel that blows by the piston ring to the crankcase. With an ABC type, you don't get much of this. I think this is what the muffler-to-crankcase line is for, to let residual ol in the exhaust to travel back to the crankcase to lube the bearings and lower end. I feel if you don't connect this up properly and use it as a vent, oil drain, as on other 4-strokes, you have a disaster waiting to happen, a potential lower end failure. Maybe I'm wrong.
09-15-2004 | 09:21 AM
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From: Brantford, ON, CANADA
RE: ring/no ring
In addition to what has been written before the essential difference between the two is the suitability for it's end use.
A ringed engine is not suitable for high rpm engines. The ring floats in it's slot. On each stroke of the piston the ring floats up and down, albeit a small amount. On a high rpm engine the ring is battered up and down and very soon goes into self destruct mode.
That is the reason for the ABC type of engine. Nothing to do with preventing damage during lean runs.
Any engine relies on the correct piston/liner seal at TDC. This tight seal can not be for the length of the stroke or the engine would be too tight to turn over, hence the taper. The correct running fits for this type of engine are when the engine is at operating temperature, not when it is cool. The piston/liner materials are such that the liner expands slightly more than the piston at temperature to establish that fit. The worst thing that can happen to this type of engine is to continually turn it over when cold, or, run it too cool.
ED S
A ringed engine is not suitable for high rpm engines. The ring floats in it's slot. On each stroke of the piston the ring floats up and down, albeit a small amount. On a high rpm engine the ring is battered up and down and very soon goes into self destruct mode.
That is the reason for the ABC type of engine. Nothing to do with preventing damage during lean runs.
Any engine relies on the correct piston/liner seal at TDC. This tight seal can not be for the length of the stroke or the engine would be too tight to turn over, hence the taper. The correct running fits for this type of engine are when the engine is at operating temperature, not when it is cool. The piston/liner materials are such that the liner expands slightly more than the piston at temperature to establish that fit. The worst thing that can happen to this type of engine is to continually turn it over when cold, or, run it too cool.
ED S
