Sporty:

The late Saito engines are AAC as you said. But a lot of the earlier Saitos had a brass sleeve cast into the aluminum cylinder, and were true ABC engines.

Bill.

William,

If it is all like you and Christopher are saying, than nearly all applicable four-strokes are AAC, ABC and ABN.

But being ringed (are there any ring-less four-strokes?), they don't have a conically tapered sleeve.

I stand corrected then.

What about the OS.50SX and OS.91FX; do they also use brass base metal sleeves, or are their sleeves made of steel?

Is everyone going back to Super Tigre's ABC ring arrangement?

Dar:

There are still several ringed engines with steel sleeves. K&B for example has chromed steel sleeves in all their ringed engines, but granted, these are two stroke engines. All the little Coxes are steel sleeve with iron pistons, I think Fox still has some made that way also. Two stroke engines as well.

Actually, I can't think of any 4s engines still using steel sleeves except the OS multis. Saito has some ABCs, most of the newer Saitos are AAC. And YS, as you have mentioned, is Nikasil. And the Magnum/ASP engines are ABC.

The OS 50SX I'm not sure about, but I'd make a bet it's ABN. There was a big flap a few months ago about the OS 91FX, It was advertised as ABC. But when nobody could make one run they started getting taken apart and checked, OS and Horizon had to backtrack quickly when everybody saw the nickel plating in the cylinder. On brass, yes, but it was definitely ABN rather than ABC. And some did peel. Nowhere as many 91s peeled as 46FXs, but there were failures.

Just remembered another ABN 4s engine - the Thunder Tiger line.

Bill.

Hey Bill,

I have heard off these Acronyms before, but I forget what they mean. Can you define them?

ringed engines?

ABC?
AAC?
ASP?
ABN?

I would appreciate it. Then maybe I won't feel so ignorant in the future. To me its like you are talking in code, lol.



Wings

ABN Aluminum-Brass-Nickel
These are nickel plated instead of chrome, a cheaper process which is not as hard. OS & Thunder Tiger use nickel plating. Nickel wears off much, much faster than chrome.

ABC
From some companies this can mean Aluminum-Brass-Composite. This means they are nickel plated instead of chrome, but are trying to hide it.

AAC Aluminum-Aluminum-Chrome
Chrome plated aluminum cylinder with aluminum piston. Enya uses this sometimes. Some of the Performance Specialties aftermarket racing piston-sleeve sets are AAC.

ABCD
Super Tigre used this configuration once. It had an ABC set up, but the piston also had a Dykes ring (a type of piston ring that I won't go into here)

ASP is an engine brand.

I got this from the following site:

http://members.cox.net/moorman1/ABC.htm

Very good information!

Matt:

Sorry, the jargon does tend to accumulate.

ringed engines? A piston either has a lapped fit in the bore for sealing, or a mteal expanding ring around the piston to seal it against compression. Most small two strokes are lapped piston, I don't know of any four stroke engines that are not ringed.

Three of your next are methods of making a cylinder sleeve and piston set.

ABC? Aluminum/Brass/Chrome.
AAC? Aluminum/Aluminum/Chrome
ABN? Aluminum/Brass/Nickel

The first is the material ofthe piston. then the sleeve itself, finally the plating material the piston rides against. The ABC was the first, and is still good, but it makes a heavier engine than the AAC. ABC is still common, currently used by Magnum and others.

AAC is a later process, machining and finish is more expensive that ABC, but the material cost is lower. The late Saito engines, and the K&B Sportsters are two examples using AAC.

ABN is the least expensive of the three. The nickel being softer than chrome they are less wear resistant than either ABC or AAC. OS, current Webra, and Thunder Tiger are ABN engines.

These aren't the only ways to make an engine, the K&B ringed engines have chrome plated steel liners, some of the Fox engines still use plain steel sleeves with iron pistons. Don't laugh. I have some steel/iron engines more than 40 years old, still run well, but you must use castor oil with them.

ASP? This is the odd ball. What we get in the USA with the brand name "Magnum" is sold elsewhere in the world under the ASP brand.

Some others you might see. C/G, c/g, cg. and sometimes cog all mean center of gravity. CHT is cylinder head temperature, MAC - Median (or Mean) aerodynamic chord is the geometric center of the wing in the fore and aft direction. Used for relating cg position.

You will also see "Bushing Engine" which should be called a "Plain Bearing Engine" as many do not have a bushing, the crank runs directly in the material of the crankcase. All the Cox engines you will see are plain bearing, with no bushing. And like the steel/iron engines, long life requires castor oil.

That's enough for now. See another come on back. But to assure an answer, call with a PM or email.

Bill.

Gary,

For some reason you mentioned the 'bogus' ABC nickel composite, yet forgot about the original, true ABC, thus not completing the answer Matt was seeking.

True ABC is a low expansion, high silicon (hyper-eutectic) Aluminium piston, running inside a Brass sleeve, that has been electro-plated with Chromium on its inner, running surface.

This sleeve can either have a tapered-bore and a ring-less piston, or a parallel bore and a ringed piston, mostly in four-stroke engines.
The ring could be either conventional, or Dyke's type.

The true ABC started it all.

DAR:

You are right; I didn't read it after I copied it from a website--thanks!

G~

Wings,

If you are still strugling with 2 strokes dont move to 4 strokes yet, first get acquainted with 2 strokes, and then consider a 4 strokes. To my humble opinion I can suggest a Super Tigre 51 two stroke. This is an excelent engine, I have 5 Myself and NEVER had a problem with one, besides, they are ringed, so they are less vulnerable to dust particles, and the best of all is that they are not expensive, good power too.

There, there goes my 2 cents.


Happy flying.

I appreciate your advice. Let me tell that I have had by 91 magnum fourstroke since mid August and so far (knock on wood) it has given me absolutey no trouble at all. No dead sticks or anything. I may be in the minority but after havng one I don't see much a difference at all as far as the difficulty in tuning them etc.

Maybe I will eat my words, but the four stroke has been less trouble than the two strokes I've had.



Wings

My first RC engine was an Enya .46 MKII fourstroke and it was no brainer.

I'm with you wings, and I'm a Magnum convert from OS. I used OS for years because of their reliable performance and of course the name. I moved to Magnum about a year ago, and now have four, all four strokes, and wouldn't have anything else. I figure they improved the OS carburettor, and my Magnums start better than the OS, and I never have any trouble with any of them. No deadsticks either.

I don't see much, if any, difference in operating a 2 stroke or 4 stroke. After all they both use a glow starter, both have a carburettor and needle etc. If you open them up they're more complicated, but I don't find tuning any different. I wouldn't go back to 2 stroke; 4 strokes use a lot less fuel and have a realistic engine sound. Sure they cost more but the gap is narrowing.

I was out flying this morning and had about six flights with a newie, an Extra 330S, 63" span running a Magnum .91 FS. Great combination.