Stunt Engines

[Casey]

Anyone know the pros and cons of an ABC Stunt engine versus a Ring Stunt engine?

[RknRusty]

ABC and ABNs are more forgiving of a screaming lean run. It pretty much won't hurt them, but a steel P&L will turn to toast on a long badly lean run.
Other than that, I can't tell any difference. If treated right, either will last a very long time. I've never run a ringed engine, but I think my statement is still relevant.
Rusty

[Brett Buck]

Anyone know the pros and cons of an ABC Stunt engine versus a Ring Stunt engine?

  More durable, more consistent, very forgiving - and all the good stunt engine designs of the last 30 years are all AAC/ABC/ABN. Ringed engines are just for nostalgia purposes at this point.

    Brett

[Brett Buck]

Are you guys serious?  I have seen, nearly EVERY, OS ABN engine that was ran lean have the coating peel on the liner.  Now true chrome is another story.  All these were in RC applications.   I consider ring more durable and capable of longer life than a ABN engine.   In fact, I feel OS engines with ABN are crap and quit owning them.  Now, OS ring and lapped design are super engines. 

  Given that I have flown something on the order of 3500 flights on ABN engines (including any number of near-full-peaked flights) with absolutely no failures and only one indication of wear after about 3000 flights, I would have to disagree with you on that one. I think Paul Walker had a similar experience, finally wearing out a 40VF after some astronomical number of flights (more than most people have flown or will fly, in their entire lives). Even George Aldrich, who was prone so similarly trash ABN systems , admitted he had never seen it in an unmodified engine used in stunt.

   Brett

[Tim Wescott]

Perhaps "used in stunt" is the key here.  Our conception of "lean" is a bit different from a typical RC'ers conception of "lean".  (Our conception of "just right" would be described by a typical RC'er as "blubbery rich").

[Brett Buck]

Perhaps "used in stunt" is the key here.  Our conception of "lean" is a bit different from a typical RC'ers conception of "lean".  (Our conception of "just right" would be described by a typical RC'er as "blubbery rich").

   At the 98 NATS, I was tweaking my 40VF and went "over the top" on the ground, and left it set at dead peak. That's when (after 8 years of competition flying) I knew it was done. Hard to get any leaner than that and still have it run. There's no "peeling nickel" on that one, it's just worn out.

   Brett
     

[RandySmith]

I have seen more OS engines than most people here, the number is in the 1000s, , I have also seen the majority of these that were stock, untouched, un modified sleeves.
I have personally modified many sleeves, and the rate of failure is not as high as the stock ones, this does not mean it makes the sleeve tougher, most likely reason is they , for the most part went to CL flier, that treated them better, with  better fuel and runs.
 and I can tell you for a fact, they have a huge number of them peel the liner coating.
 I have also seen many that have worn thru the super thin soft nickle and were running on the brass, this happens routinely, if you running them hard, as a heli or RC airplane pilot would, if you know how to run the in CL stunt, and use good fuel, proper oil, and set them so they do not go lean, then normally no problem until they get worn,
 the People like Brett, that know how to set and run them, have near zero problems .
Henry Nelson, and Dave Shadel had a huge business  replacing, the OS piston sleeves  with the much superior Chromed ones, or honing the nickle out and re-chomeing the  sleeves.   by the way you would have an extremely hard time honing chrome from a liner.
Some may not want to hear this, but it is fact!

Randy

[Chris McMillin]

I have a couple of used 46 FX engines I started with my usual 20 to 22 % oil fuel and they run for many seasons as the kids flew RC without any peeling signs. The 46 and 55 AX I bought new performed perfectly for 25 and 5 gallons each so far, both in Classic Pattern ships. I have never had trouble with a 46 VF, or any Nelson/PA liner in Stunt. I notice guys making new liners for worn out liners on old Pattern engines like 61 VF, and Hanno's because high usage but most guys add oill up to the recommended 20 to 22% on the OS instructions and these engines were flown until they wore through the liner coating, not peeled.
I don't think helicopters run engines very nicely and perhaps like Speed and Pylon they're considered replaceable at sooner intervals than in aerobatic use of any kind.

[Steve Helmick]

The ABN/ABC/AAC engine should run smoother (lighter piston) and give better MPG than a ringed version of the same engine, all else being equal. This ("all else being equal") pretty much requires a custom P&L, such as the Nelson/Randy Aero AAC OS .46VF (which I have been flying for some years) and the ST G.51 with the recently available Brian Gardner ABC conversion.

I don't count flights, but sort of keep track of gallons, and "my" Magnum XLS .36 probably has 22-25 gallons through it, mostly PM 10-22GMA. I got it used from Mike Haverly and passed it along to Tim Wescott awhile back, still very easy to get a 1-flip start. Tim is using it on his Cartoon Mooney Mite for various things...teaching his wifey to fly, learning to fly left handed, and who knows what all else.    Steve

[Andrew Tinsley]

I think there may be a plus for ringed engines in helicopters, where the engines are regularly subjected to hot runs etc. At least when the ring goes you can fit another, maybe a cheaper option than a new P/L. Most ringed engines these days seem to be on large engines or helicopter engines. There must be a point where rings become the best option for larger sizes, otherwise our car engines would all be ABC!
I would say that it isn't difficult to wear out LA series engines, they are really cheap, cost cutting affairs. With the right fuel and settings, I have lost all Pinch after a couple of hundred flights and the performance is reduced, even I can notice it! Most other people using ABN have thicker harder coatings, Thunder Tiger are a different kettle of fish and are good. They have thicker and harder coats than OS.

Andrew.

[Steve Helmick]

"They say" that the reason Heli engines are ringed is that they run hot, then are throttled down and the piston seizes due to quick cooling. The looser fit of a ringed piston stops that nonsense. They also tend to pump oil out the front bearing, when converted to CL stunt use, which is a bit annoying, at minimum. These reasons make sense to me.  Steve

[Steve Hines]

How about a ABC ring motor that enya made. Old SR motors were good motors, F motors were not to bad, don't know when they went to nickel on cylinders, but OS has been a junk for a long time. There cheep but you get what you pay for.If you can get over 3000 flights on a os just think what you get from a PA or Jett. I do like ABC over ring, I think you get a little more power, but you never push a cl stunt motor that hard anyway. I also like how a well broke in ABC starts. If my brother ever puts one of his enye in a plane I will see how it starts.

steve

[RandySmith]

HP made a Gold cup 40 that was an ABC ring engine, they worked and ran well, and lasted longer than the steel version
, but not as long as my ABC lapped versions
Randy

[proparc]

Top of the line ABC control Line motors have been superior to top of the line Ring control Line for a long time-not really any debate there.

Where there is HUGE debate is in the RC world. I happen to own top of the line RC ring motors, and top of the line RC ABC motors and top of line combinations of both. And the answer is---no consensus!! Strictly depends on the quality and engineering of the respective manufacture.

Both types of motors are highly sought after even today,(maybe more so) depending on the make and manufacture. And, if you don't believe me, try to go after a Moki 61 LS Ring side exhaust with adapter NIB. Or, a Rossi 61 ABC Blackhead Side Exhaust with header NIB.

Or even MUCH MUCH worse, a Webra Speed 61 Long Stroke Black Head side exhaust with slide Dynamix carb NIB!!  I would love to just actually hold one, much less own one. It has a Ring by the way.

An OS Max Hanno Special NIB just went for-I believe $575.00. Those came in
Ring and ABC version. Either one will send you to the poor house.

[Lauri Malila]

I think the surface problems with lapped engines are caused more by users than the technology. It can go wrong in many ways.
I like my ringed setup (integrated AAC with first standard- and now Dykes-ring). I prefer ring because the seal remains the same through a wide temperature range, lapped tends to go worse when temperature goes up.
But it takes some skill to make it well, like with many other micromechanical, many things can be wrong.
Most of the negative comments about rings in here are caused by something made badly about 40 years ago, and since lapped technology came, it seems that nobody has bothered to think about making a good ringed setup anymore. But whatever works when used correctly.
L

[Rich Perry]

I would like to add that most RCer's just run the crap fuel they get at the LHS with no thought of the oil content.  Being that CL flyers pay more attention to such things, the ABC engines would most likely do better.  I have a lot of OS engines, and have never peeled a liner.   And yes, I am an RCer, for a very long time. But have come back home where I belong,  CL.

[Andrew Tinsley]

I much refer ABC or similar systems for stunt. Rings can go bad between runs and leave one struggling. However as noted above, the OS LA series are bean counter engines. Using a heavy airscrew, I have worn a liner system out in a little more than 2OO runs. A new liner etc brings the engine back to good health. When that is worn out, the bearing bush is showing signs of wear!
OK the LA46 is an excellent stunt engine but not well built, for similar of less money you can get a G42 which I find to be every bit as good as the LA46, but will last much longer.

Andrew.

[Steve Helmick]

I much refer ABC or similar systems for stunt. Rings can go bad between runs and leave one struggling. However as noted above, the OS LA series are bean counter engines. Using a heavy airscrew, I have worn a liner system out in a little more than 2OO runs. A new liner etc brings the engine back to good health. When that is worn out, the bearing bush is showing signs of wear!
OK the LA46 is an excellent stunt engine but not well built, for similar of less money you can get a G42 which I find to be every bit as good as the LA46, but will last much longer.

Andrew.

I guess that by "G42" you mean a Thunder Tiger GP .42? Are they still available across the pond? TT's are not easy to find here. It seems like they are divesting themselves of all things IC, if you look at their website. That's a real shame.  Steve