I'm sorry my friend....I wasn't ignoring you....I was busy with something
else. Comparing our ringed glow engines, especially a 4-cycle glow
engine to an automobile may not have been the best analogy. However,
the point was....would you have the engine set to run extraordinarily rich
to facilitate the break-in of the rings ? Of course not.

An automobile engine has two compression rings, one oil scraper ring, and
the oil control rings.

The rings of an auto engine do not come into the concern of the break-in
procedure because:

1. The precision of the clearances in the engine, the cross hatching, the
quality of the rings, and the controlled temperatures that the engine runs
in (water temp) all but eliminates any problems with the initial break-in
(sealing) of the rings.

2. The fuel mixture, controlled by electronic computers and of course,
fuel injection....eliminates any disparity in the mixture. You will never have
a too lean, or a too rich mixture in an auto engine. The computer will assure
that all is well with the mixture, as well as the ignition timing of the engine.

Our aero-model engines have a certain limitation that one must consider. We
have only only ring on our pistons to do the whole job. In the case of the
ringed two cycle engine, the ring must seal properly, and at the same time
have a minimal ring gap to insure adequate compression and the complete
"pumping action" of the two cycle engine.

The four cycle engine has only one ring as well. Here is where the problem lies.
We must have proper ring seal to insure proper compression....but at the same
time, we must have just enough blow-by to lubricate the rest of the engine.

If....and the big word here is "if" the operator fails to seal the ring on his two
or four cycle aero-model engine....due to improper procedures....he can and
will experience a lot of trouble, and he just might have an engine that turns
out to be unmanageable, or as some say....a POS.

I'm not saying this will happen in every instance, nor am I saying the engine
cannot be brought back to a serviceable condition by changing the operation
....and effecting the remainder of the break-in....to where the ring actually seats.

Some Old Time mechanics will nod when I mention the "Bon Ami" procedure,
in which powdered cleanser was dumped into the carb of an engine running
wide open in an attempt to seat the rings of an engine that had been improperly
broken-in, and suffered from excessive oil consumption and poor performance.

FBD.

Actually DU it wasn't aimed at anyone in particular...it's just something that I recalled reading and hearing about as I read thru this thread

I will say one (more ) thing...and that's that I doubt that I'll run a ringed engine quite as rich initially in future. I have wondered if I was running an engine to cool, and if that perhaps might have a detrimental effect?
Lots of food for thought in this here thread...[8D]

skiman762....I appreciate your input, and I can see you are trying to help
and participate in the conversation. I can see also that you are not an engine
mechanic. That's OK....not everyone is.

Lycoming is not in the business of making single cylinder, single ring...two
or four cycle model aero engines. Their procedure for controlling compression
and blow-by in their aircraft engines is so different from ours....

....to call the difference like "night and day" would be an understatement.

One thing I can positively guarantee you 100% true, for tonight and the rest
of your life....Lycoming would not have you richen up their carbs to have the
engine running sloppy rich....to facilitate "break-in" of the rings.

Whether you agree with me or not, the only way to properly seat the rings
of an engine is to operate the engine the way it was designed to run....

....it's really just that simple.

Take that to the bank....forget the Internet Experts, that never worked a day
as a real mechanic....with proper training. "Home" (shade tree) mechanics
need not apply.

The Internet....a place where, with 15 minutes of Google, you can argue with
anyone about anything.

FBD.

[X(] whoa, I had no idea that my topic was gonna get this much attention. Guess I could give a little more info for it. I have a TT 120 ringed engine and here these last couple of flights, its just been a turd with a propeller. it has very poor power at full throttle and runs very hot, doesnt idle good or rev very fast, and sometimes it even has a mind of its own [&:] acting eraticly, no matter how much I play with the needle. and I really dont know much about ringed glow engines (the plane/engine is really my dad's that im trying to get info for) cause im more of a abc guy

Are ringed engines suppose to be really easy to turn over, or are they suppose to have the "tight" compression feel like an abc engine? This TT 120 has pretty much no feeling of compression when you spin the prop by hand, but is does start pretty well. but another thing is I dont how this engine was broken in, or if it even was broke in correctly. my dad ordered a GMS 120 and he was wanting me to break it in for em.

And BTW, not to long ago I got a os 46 ax for my plane (aresti 40). I mounted the engine on the plane (no cowl) and broke it in going by how the manual said to do it, but I dont remember if it was exactly or not.. Started it up, opened the throttle wide open and ran it "4 cycle rich" for 1 tank. and man what a oily mess that was [:'(] . let the engine cool down till it was cold to the touch. ran it wide open rich again but this time turned the needle valve in till it was really singing like it should for about 5 seconds, then back to runnin rich for about 10 seconds. I did this part for 2 tanks of fuel. after that I took it and flew the guts out of it, and its been running perfectly ever since. I guess I've probably ran 2 gallons at least through it by now.

and from all that i've been reading on this topic, I think I've decided how im going to break this new engine in. im gonna just let it warm up till its warm/hot to the touch then go wide open with a fairly rich setting, lean it out a bit and let it scream for about 5-10 seconds and richen it back down for about 10-15 seconds. repeat this for about 2 tanks, letting it cool down in between, then take er out and fly the hussie wide open

LMAO,
Dave you are incredible. Keep up the good work.

Big Bopper

You must be kidding. The tolerances in a auto engines are nothing compared to a model airplane engine. Cox tolerances were with in 25 MILLIONTHS of an inch. NO auto engine ever had tolerances that close. Thousandths of and inch at best in auto engines. The rings aren't part of the break in in an auto engine????? That is one of the biggest part of auto engine break in. The rings must wear and mate with the cylinder. Rings are made out of cast iron and relatively soft so they will wear in. That's why a new engine will burn oil oil until the rings break in. Chrome rings take forever to break in and wear the cylinder much faster.

Temp in an auto engine is controlled by water temp??? Tell me about Volkswagon and Porche. Remember the Corvair? That goes for airplane engines too. Not a whole lot of water cooled aircraft engines out there.

Auto engines have two compression rings. Have you ever looked into the cylinder of a McCoy 60? Or a Forster 99, or any of several other model airplane engines? They have TWO compression rings.

Fuel in an auto engine is contolled by computer and fuel injection?? I just looked under the hoods of my 58 and 64 Cadillacs trying to find a computer and fuel injection system. I sure couldn't one. I drive an 81 Datsun 210 every day to Tacoma. It has a one barrel carburettor and there sure ain't no computer under the hood. My 85 Caravan has a two barrel carb.

Bon Ami in the venturi?? Yes sir, break in the rings and wear out the crankcase bushing or ball bearings as well as the rod bearing at the same time. Let's pour carborundum in there and really speed up the process.

That's enough for this post.

Bopper:

And I laugh when I see yur avatar - I recognize the picture. Want to buy a vowel?

Haw.

Bill.

Aaahhh man...I love this place!

Bill....

....I see now that loughbd hasn't a clue. He wants to argue about everything.

Maybe he wants to buy a vowel.....[X(]

FBD.

I don't have a clue??? I'm not the one that said auto engines don't need a break in and that the rings in a car engine don't wear in. I'm also not the guy that said the tolerances in an auto engine are tighter than in a model engine. YOU did.Why is it when I say something, it's arguing but when YOU say something it's the gospel truth not to be contradicted or questioned????

Dave:

What Bruce is neglecting to mention, or even consider, is that a one thousandth inch error on a four inch small block Chevy bore is equivalent to a 0.000001" error on the 0.401" bore of a Cox 0.049 engine. Roy Cox claimed one millionth inch accuracy, but I've measured as much as a tenth of a thousandth difference in brand new Cox pistons. Cox' claim was mainly hype, but they were close enough that most could be run without hand fittung.

And yes, I was on speaking terms with Roy Cox in the early 1960s, Bruce. Also Johnny Brodbeck, Bill Wisniewski, and... Want to drop some more names, Bruce?

Bill.

So was I pal, Working in the industry you get to meet and know lot's of the big boys. Ralph Brooke, Hazel Sig, Maxey Hester, Joe bridi, Ken Willard, Cliff Werick, Jack Albrecht, Garland Hamilton. I was at Ken Willard's funeral and my dad was a pall bearer. Knew and flew with all of them. Big deal. Drop all the names you want. Wanna see a picture of me and Hazel Sig. Want to see a picture of their house?



As far as tolerances go a millionth of an inch is a millionth of an inch. Doesn't matter if it was in a 10,000 cubic inch Submarine diesel or a Cox 010.

...yeah sure. I guess Bruce believes everything he reads.

I beg the forgiveness of the great masters. I will never question your authority and vast undeniable knowledge again. I forgot that I was one of the average morons with the knowldge of a rock. Who am I to even question the experts?

Good night

There's no forgiving your recent performance.

Now go away and let the experts teach the newbies.

Guys...I don't want to be argumentative, just curious...
How did they (Cox, or anybody else for that matter ) manage to get such close tolerances without such things as CNC machines? Hand fitting?
I worked in a fully equipped machine shop for a few years (until my mom had a stroke, so I'm taking time off to take care of her ) and ran parts on CNC lathes and mills, and the closest we ever bothered with was 5 tenths (half a thou )

Even 25 millionths...just one little spec of dust under the micrometer and that would throw off youir reading...right?!?

I do when it's written by people like Clarence Lee, George Aldrich, Dave Gierke etc. Those are well known authorities on the subject. Outside of RCU you guys are nobodies. Even here you are pretty much nobodies. Legends in your own minds.

Proptop....

....answer....they didn't. Member loughbd is loaded with "interesting misconceptions".

FBD. []

I think the only thing thats ever been accurately measured down to 25 millionths was a crickets weenie. But that was in 1965, so who really knows if the instruments were accurate?

proptop:

Back in the stone age we used what was referred to as an "Air Mike" for the really precise measurements, and centerless grinders for the finish sizing. The air mike could read to a millionth inch, and since it read the flow restriction on a column of air it automatically blew all the dust away, and the oil film as well. Now that we have laser interferometers we can measure to a billionth of an inch.

CNC machining is convenient, and gives part after part with almost no variation in any dimension. But anything you can do with CNC can be done by a skilled operator, provided he has machine tools of similar quality. But the unit production cost will be much higher - a lot more labor time by a high priced worker. Doesn't take a lot of skill to clamp a work piece in the chuck and push the button, then go to the next machine and do it again. This is the biggest selling point of CNC.

This is not to say you aren’t a good machinist, but you do have to admit the skill requirement for loading a transfer machine is minimal.

Bill.

All of you:

Listen up, guys. Millionth inch accuracy has been available since the 1930s. Do a little research on grinding the mirror for the Hale telescope on Mount Palomar. They used optical interferometers to check the grinding, and later, the polish.

Those close tolerances weren't commonly used because the instruments were expensive, and that that much precision wasn't necessary in everyday things. Now that lasers and greater precision tools are available we see many things decreasing in size, and reliability increasing because of the more consistent manufacturing.

Just consider a modern computer with the CPU running at a clock speed of 3 GHz and higher - some of the internal conductor strips are only two or three ATOMS wide.

Bill.

Thanks Bill...I've heard of those precision measuring devices, but we never really had the need to get that close. We made specialty fasteners, and the tolerences were usually .001-.003... I learned "cutter comp." and a few other things, but my time was for the most part spent restoring the bosses 1978 PA-18-150 on which I did a complete re-covering (ceconite ) job.

Aircraft engines are run richer than automobile engines on the ground and at takeoff. Not sloppy rich but a lot richer. They also have looser clearances because of the huge differances of cooling on the ground and in the air. As a result there is a lot of blowby till they get into the air and are running at operating temps. Still even without detergent oil they do not glaze if you follow their break in procedures.

Haven't messed with this since the 70's and not a machinist expert like you and Dave, but I recall an optical measuring device, while not sure it read in millionth's, I am pretty sure it would get down to 1/100,000.

Just to keep on subject. Not sure that you can even have break in glaze on a model airplane because of the differances in oil. For one I have never seen a model engine glaze, except the kind Bill talks about on a well worn engine. And even castor oil resists oxidation, synthetic oil will vaporize instead of oxidizing. In short I think the very rich four cycle break in has some validity. That doesn't mean you can't break in an engine by simply running it slighty rich, you can, but IMO the extra rich run in avoids overheating on that first critical run, and thats what I will do. Never had a problem with it, but have had problems when I could not get the engine to run rich due to poor fuel draw, and never really right after that.