Back when I used to fly control line planes, my engines all had one speed: WIDE OPEN! Now, with my RC planes, we have a choice as to engine speed, especially on run in. Altho the directions on the engines I've purchased appear to give nebulous guidelines on run-in engine RPM, they appear to suggest WIDE OPEN STILL, even the 4-cycles. They do instruct you to run the engine VERY rich to keep them from overheating. I know I wouldn't think of buying a new car and breaking in the engine at balls-to-the-wall full speed (or any other mechanical device). I'm thinking of breaking in my new OS .40 4-stroke at less (maybe half throttle) than full-speed.
Can anyone give me any feedback from their experiences as a guide?

Actually you do want to break in at wide open throttle. You wont be running at full speed though, you will be using the fuel mixture to control engine speed (richening the high end needle to slow down the revs). The reason for this is that in this way you will always be running rich during break in providing the extra cooling and lubrication needed at this stage of the engines life.

There are different guidelines from different manufacturers as you've seen. You are probably going to get many other views also. Ringed engines should be broken in as you state. Lapped engines are varied! Saito guidelines are the only one I follow when breaking in a Saito otherwise I fill up the tank and run it rich @ about 3,500-4,000 rpm and just let it run. Then let it completely cool and run another tank. 3 tanks and you can then lean out the low for a reliable idle and the hi to a slightly rich setting and go fly. YS's I set on the second tank and go fly! Hope this helps.

Jackster,

Only for tapered bore engines (ABC/AAC/ABN/Plasma ceramic) is it imperative to do the break-in at full throttle, high RPM and a slightly rich mixture. This is because these engines must reach their correct operating temperature, so the cylinder sleeve will become parallel, due to differential heating and the break-in will proceed as it should.

For a cast iron ringed engine, that in its life will run at 10,000 RPM at full throttle, it doesn't matter how rich you make the mixture, it will not be able to sustain 4,000 RPM at full throttle.
It will have to produce less than 1/6th of its maximum HP, to do it and the mixture will be "too rich to fire".

If this is what the engine manufacturer says and you want to follow his instructions to the letter, you will have to partly close the throttle (to about 1/4 open) and richen the low speed mixture (by opening the idle needle), because the main needle has no direct control whatsoever, over the mixture at this throttle setting.

So you either disregard what he tells you about the throttle setting, or what he tells you about the RPM.
You cannot keep the cake and eat it at the same time.

Some car engine manufacturers tell you not to exceed 2/3 of the maximum RPM (If the red-line is 6,000, then it is 4,000 RPM...), or to sustain full throttle acceleration for more than a few seconds, for the first x hundred kilometers, or miles.

In either case, you must heat-cycle the cast iron ring, with several (10-20) very rich, short (20-60 seconds), 2/3 RPM runs and complete cooling in between them. Cast iron pistons need the exact same treatment, to anneal the piston and to stabilize its size.
After that initial treatment, 20-30 minutes of rich running will put an end to it.


I invite Thunder-Tiger's and OS' engineers; those who wrote these impossible-to-fulfill break-in instructions, to prove to me that if I do the break-in as I described in the previous paragraphs, the engine's lifespan will be compromised, or its power, or its reliability.

They will not bother to try, because they know it will not happen.

These break-in instructions are merely a warranty "trap-door", if they happen to receive too many warranty returns...

The Saito recommendation is very do-able, it says 1/4 to 1/3 throttle opening and 4,000 rpm for ten minutes. The Saito recommendation has never been to run it wide open and richened down to 4,000 rpm, the engine would be so cold and wet it would never break in. And they certainly don't recommend the warm it up and shut it down ten times method. I have broken in about 15 Saitos and several other fourstrokes using Saitos 40 minute procedure and all turned out perfect.

Thank You "Hobbs Ole Man," That has been my point all along. I have used a similar method on my outboard boat motors for years, have yet to burn out a powerhead or throw a rod on one. That hot chill hot chill method makes no sense. I know i will get a response from some one that has run racing engines, I have spent enough time around tracks to know most race engines are run once and rebuilt or cycled out.

hobbys,

The instructions with my OS160FX: http://www.osengines.com/manuals/160fx-ring-manual.pdf pages 10-11.

Saito"s latest break-in instructions: http://horizon.hobbyshopnow.com/shar...itosingles.pdf pages 4-8

Super tigre instructions for ringed and ABC are here: http://www.supertigre.com/manuals/sup-manual.pdf pages 19-25

Old green cast iron lapped piston with steel sleeves engines must be run at the four stroke break and then heat cycled. It doesn't hurt to heat cycle (let it cool completely between runs) and I usually do it with all my engines. Old school.

This will get most of us out of the woods.

The heating and cooling cycles can be done quite nicely while taking off and landing.

Thanx to everyone who responded to my question. The message I get is to run the engine on the rich side, and make sure the RPM'S aren't too high. Above all, DON'T let it run too lean and thus, overheat it. Do this for maybe three tankfuls and mount the engine on my plane. After that, the rest of the run-in can be done with normal flying and a slightly richer mixture than "optimum" for a few more flights.
I really appreciate everyone's input.

Jackster

David,

These flight/landing cycles, are probably what got your engines safely through the break-in. But I think a controlled, test stand break-in is still preferable. Allowing the engine to cool completely between short runs, gets the annealing done properly, within about two hours; not 2-3 weekends, as you would get when doing it your way.

The modern, CNC produced engine will survive even if it is not treated carefully, but is it the correct way?

I would prefer George Aldrich's words, to the LHS guy's words, although the engine will probably survive both ways.
I believe it will have a longer life after a George Aldrich type break-in.

One thing I do know, is that it's necessarily wrong to assume just because something is produced on a CNC machine, that it's automatically better. I've been a machinist/toolmaker by trade since 1965, and know that most things that can be made by computerized machines can also be made manually. Unless there's a fancy shape, which would have to be set up specially, there is nothing that an automated machine can do that a suitable manual machine in the hands of a skilled craftsman cannot, at least as far as engines go. In fact, I've had to "feel/hear in" critical, extremely close dimensions that the CNC couldn't do because of it's limitations. There's no "magic" that the CNC does to make it better. Maybe they can run production faster but not better. The "baloney" that the manufacturers put into their instructions/ads that just because their machinery is computerized, that everything's so much better that they need very little break-in is just a way to sell more engines.

After studying the different methods, I now believe the Saito instructions on engine run-in are the best overall. No messing around trying to get the "optimum" needle valve setting first, and looking for "white" exhaust and then "grey" exhaust while chancing detonation/overheating, before the engine is ready for it, like in the O.S. instructions. Just set the needle 2 1/2 open (very rich), start, and run 10 min. initially. Pretty straightforward to me, and very simple to do.
Thanks again, for everyone's help.
Jack

Jackster,

The beauty of CNC machining is that you get 200 sleeves and 200 pistons (and crankshafts, and...and...) and you take ANY one of each. They all fit their mated parts and all feel the same when spun around.
They will also be within 100 RPM, as far as their performance is concerned.

There are no "bad apples". The entire lot is either all good, or all bad. And a minimal measure of QC makes sure this doesn't happen, or the goods don't leave the factory.

The fit between the parts is such, that they actually do need a minimum of break-in time, to achieve the correct fit.

CNC is used to machine valves and their seats, for full size engines.
After that, you don't need to grind them with silicone carbide paste, to make them seal. They seal like ground valves and seats, immediately after being manufactured, without the added hassle.

Todays CNC manufactured engines are very close to that, but in the case of cast iron rings, or pistons, the heat treating - annealing, work is up to the modeler. By doing it properly he, or she, will determine the lifespan and the life quality of the engine.

They have not yet found a way for CNC to replace the annealing, but who knows? Maybe someday.

I will use a Fox engine as an example, I tried to improve the porting on a Fox cylinder one day, well my Dremel grinder wouldn't even scratch the cylinder let alone grind it. So why would it need to be annealed.

There is a world of difference in a water cooled engine like a boat engine and an air cooled airplane engine. The heat-cool cycle has been recommended by everyone who has worked in the model engine industry for years.

With a ringed engine, you need to run it rich some to seat the ring.

An ABC engine is really hard to hurt is you just crank it up, lean it out, then back it off a little and go fly. It is my opinion this is the reason nearly all engines are now ABC type construction. The great numbers of new people with no knowledge of engines and no desire to break one in has made ring engines less desirable from the manufacturer's standpoint.

David,

The part that gets annealed is not the cylinder sleeve.
It is made of heat treated, hardened steel in such engines. This is why it was not even scratched by your Dremel tool.

The cast iron piston, or ring, is soft to begin with, but after getting annealed it becomes hard. While the break in progresses, the cast iron part embeds some of the hard steel particles that come of the sleeve and uses them to hone and lap the sleeve.

Please read this web page: http://www3.telus.net/dieselcombat/breakin.htm .
It talks about Diesels, but the principle is identical.

Ed_Moorman,

Some of these older "geezers", that grew on ringed engine (and some younger "geezers" who learned from them), misguide new modelers to break-in their new ABC/ABN engines, as they would a ringed engine. This causes the tapered bore engine damage and prevents it from ever making its intended power output.

And it is all done with good, honest intentions.

This is why I started the "Break-in in tapered bore engines" thread about 7 months ago.

Dar Zeelon:

Yes, the computer controlled machines are faster in production, BUT their tooling breaks/wears down just like any metal-working machine's does. Don't think you'll NEVER get a bad part out of a CNC. I've seen entire lots of parts from CNC's come back from a buyer, rejected because 1 or 2 parts which happened to be inspected by them as a %age of a batch were out of tolerance. In an imperfect world, etc. etc. Don't get me wrong, I've set up/programmed/run CNC also and they're remarkable in what they can do, but there's occasionally a "joker in the deck". You also need to fit mating parts the tedious way sometimes, because they STILL haven't found a way to work out the math/accuracy so "every one" will mate with "every one".
All that aside tho, CNC can produce precision parts cheaper as they need no breaks, health insurance, have no family problems, etc., so we wind up with a less expensive engine of fine quality. I still maintain however, they're not a magic bullet.
By the way Dar Zeelon, thanks for your input.

Hobbsy:
If the cylinder was chromed, it's hard as hell. At the factory, it was either honed or lapped (probably lapped) to it's proper size. In a run-in, the "give" would have to happen on the piston-side of this mating of parts. In order to "run in" to make a better seal, there HAS to be a harder material and a softer material to mate with it. The ABC, ABN definition (as I'm sure YOU know), is as always: Aluminum piston, BRASS cylinder liner, Chrome/Nickel plating. NO annealing occurs with the brass cylinder liner.

I have to agree with Jackster that CNC isn't the be-all and end-all of machining. Back in the 50's Cox started making their little engines (and the smaller the engine the more critical the fit) and even with the machinery available at the time they were able to take a piston at random and have a perfect fit to a random cylinder. Their tolerances were down in the millionth of inch range and even though they were a cast iron piston the suggested run-in time was on the order of 1 minute rich.

Jackster, DownUnder,

I do agree that CNC is not a magic bullet.
However, since the "human error" factor is taken out of the equation, tool breakage happens much less, than when "twitchy handed" humans do it.

When the first, "out of tolerance" part comes out, all subsequent parts will also be.
So modern CNC also uses its software, for inspection of the parts.

If a part does prove out of tolerance, the process is stopped and the bit, or whatever, is replaced.

Duke Fox awoke later and changed the suggested break-in instructions, to get the annealing done...
Please read contemporary instructions, for Fox (and Enya), Meehanite piston engines still in production.

Dar Zeelon:
I'm unfamiliar with software that automatically checks tolerances of CNC work in the machine. Altho I'm not debating your statement, I wonder about the method of checking to be sure of the part being in tolerance because of tool wear, breakage etc. Of course, you can set up a schedule of changing tooling using wear rates, tolerance checks, etc. using info gleaned from past records. "Twitchy handed humans" are amateurs. You can't be a skilled craftsman and be "twitchy handed". Yes, mistakes happen, but far fewer than you suggest.
As Down Under notes, these kinds of things CAN be accomplished by us "mere humans" quite capably and productively. Please, Dar Zeelon, give us credit for being more than complete incompetents.
Sincerely, Jackster

Had to edit to correct a spelling error, [error]

Jackster,

No insult intended.
But humans are not perfect; far from that. Neither are machines, for that matter.

I was talking with Dub Jett, who told me that a very expensive, Israeli made Iscar tool (http://www.iscar.com/), had broken in his hands, while manufacturing a part for a Jett engine. And he is a professional; not an amateur.

A human is more likely to slip, than is a CNC controlled lathe, or mill.

It is also true that amateurs are more likely to slip, than experienced, trained machine shop workers.

And after all; a CNC machine is programmed by a human and some CNC controlled mills even record his movements, while manufacturing a part, and are simply repeating them again and again, to manufacture subsequent parts.

Dar Zeeling:
Sorry I sounded hostile. Actually, I'm amazed at what modern CNC machines can do. They can save so much time as opposed to the way we used to machine many parts. Believe me, noone knows this more than I. Even in an environment where only one part is made, the machine can do a MUCH faster and acceptable job.
It's now time to move on. I think I've gone into "left field" with this thread. Thanx for all your input, my friend.

Jackster