Good evening fellows.

A while back i came across the thread here on universe where one of th pros was giving detailed description on breaking engine in.He was talking about all types from ABC to ringed.
At that time i read through and went on but today i need to find that thread.One guy at the club did show interest about learning to break engines in and he wanted to include part of the thread in monthly newsletter.I promised him i'll get the text since i though i saved it on my computer but i looked and couldnt locate it . And I spent at least two hours looking through the archive but can't find it.[:@]
And I know i am not gonna be able to write as good about the process as that guy wrote.So if anyone by any chance have a link to the thread or have detailed description on how to break engine in please help out .
Thank ahead.
Mitty

I copied this and printed it for my own use. Luckily I saved a copy on my computer. The Author is shown at the bottom. Hope this is what you asked for.



This issue is revisited time and time again by many modelers. Every week, or two, another modeler opens a new thread, asking questions about this subject. I have referred many of them to the original thread.
Since the original thread was started, a little over one year ago, it was visited by nearly 6,000 RCU members.
Many have added some useful input and I have also reached some conclusions.

I thought it would be a good time to enter a new thread, based upon the old one, with some omissions and necessary additions, to further extend the useful life, power and reliability of the now very common tapered-bore engine.


Most engines with a ring-less high silicon aluminum piston, running in a plated cylinder sleeve, have a conically tapered bore.

This means the bore diameter is smaller at the top of the sleeve than it is at the bottom.

The purpose of this smaller internal diameter upper cylinder is to cater for the differential heating (and expansion) of the cylinder, when the engine attains its normal operating temperatures.

The upper part of the sleeve, near the head and the combustion chamber, is much hotter than the lower part of the sleeve. Therefore it expands more and when at operating temperature; the part of the sleeve in which the piston reciprocates, becomes nearly cylindrical.

The piston in these engines is made of a low expansion, high silicon content, aluminum alloy (hyper-eutectic?), so it expands no more than the brass (or aluminum in AAC), base sleeve material, when heated.

All these engine's pistons have an interference fit at the top of the bore, so the engine "squeaks" or even seizes when turned over when cold. Even more so when it is new.

Because of this fit, these engines need special break-in procedures. Harry Higley, David Gierke, Clarence Lee, Dub Jett (Jett Engineering web site, read about break-in) and the late George Aldrich wrote about these principles and they work.

If such an engine is broken-in slobberingly rich and four-cycling, as you would normally do with a ringed engine, or with a lapped meehanite (cast-iron) piston engine, it could be run-out, worn or broken, instead of being run-in.

If the sleeve is allowed to remain tapered, during the break-in, the interference fit at top stroke would get the piston and the plating scuffed, with ABN engines being more susceptible to plating damage.
Lower costs of waste product disposal are the only reason some engine manufacturers prefer nickel plating to hard chrome.

Also, in every non-firing revolution (every other revolution when four-cycling) the piston is pushed, into the seize at the top of the bore and then pulled back down, out of the seize, by the con-rod. These repeated compression-tension cycles can ultimately cause the con-rod to fail, due to metal fatigue (this was once common in some older K&B ABC QM engines).

Even if the con-rod remains in one piece, the loads imposed upon its bushings/ends by piston shoved in and out of the cold, tight sleeve top, could potentially hog out the con-rod ends (bushings). Much more so than would running a racing engine at a rich two-cycle, with normal fuel, from the start.

Even if no immediate failure occurs (and in most sport engines it will not), the piston's crown will be worn down, as much as it would by many hours of normal use.


Dub Jett writes that the actual target of the break-in is the bottom end.
Since ball-bearings don't need anything of the sort (as well as not requiring any more than 2% oil in the fuel), the targets are obviously the sliding bearings; the con-rod bottom end, the con-rod top end, the crank-pin, the wrist-pin and the wrist-pin bosses in the piston.

If the engine is a bushing bearing engine, like the Thunder Tiger GP, or the OS LA engines, the crankshaft main bearing (bushing) needs the same treatment that the con-rod ends are getting.


To protect these bottom-end parts during the break-in, without resorting to an extra rich mixture setting, that will potentially result in the problems described above, a special fuel formulation should be used for break-in.
Use fuel with degummed Castor oil (unless it is a YS two-stroke; then add synthetic) added to it, to a balance of 25% total oil.

This fuel will only be used for test-stand break-in, so you shouldn't care that the engine may not idle well and may provide less power. All engines will start, run and could even be peaked on such a fuel. You will only need about a quart of it, so the cost of preparing it will not be precariously high.


Using fuel with 25% oil will make any blubbering rich running unnecessary and will prevent the damage caused by any very rich and cold running period, without risking any bottom end damage.
Strangely, that short, blubbery rich minute, can cause the exact damage to the con-rod, that it is meant to prevent.

The high oil content prevents the need to choose between two evils, since you have both the two-cycle rich, operating temperature running, as needed for the piston and sleeve and the copious amounts of oil, needed to protect the bottom end.


Using the break-in formulated fuel, tapered-bore engines must be broken-in at a somewhat rich two-stroke mixture setting, beyond the point it starts to two-cycle, but not too lean.
It must be run with the throttle wide open and idling will achieve nothing during the break-in.

You may begin with short initial runs, but this is not really necessary.

Many sport type engines are virtually ready-to-use, just start and fly.
But I prefer treating my engines, as well as any engine I am entrusted with its break-in, as if it is an expensive, racing engine

Dub Jett recommends using a prop with the same pitch as the flight prop, but with one inch less diameter.
This, to lessen the load on the engine without compromising the cooling.


Run the engine initially for a total of 15 minutes, in a somewhat rich two-stroke mode.

After that the engine should be leaned gradually for short periods and then richened back (still two-cycle) to cool.
After about 5 minutes doing that, try to lean the engine carefully to maximum RPM. If the engine can hold maximum RPM without sagging, for 60 seconds straight, you have completed the break-in.
If it sags richen it immediately, to prevent damage, repeat the first part of this paragraph for 5 more minutes and then try again.

Repeat until the engine can hold peak RPM for 60 seconds.

The engine must not be allowed to run for any length of time during the break-in, at a four-cycle rich setting.
After the break-in is completed, there is no problem with four-cycling because the interference is minimized and is no longer a wear issue, even if the engine is run lukewarm.


After the break-in is completed, the TDC pinch should be retained. Not as tightly as when new, but it should be perceptible when the engine is turned over without a glow plug.

I have had ample experience with breaking-in ABC engines made by Rossi, MVVS, OS FSRs and various Chinese OS clones, as well as ABN engines made by OS, Thunder Tiger and Webra.


The only non-success was with my own OS.40FP, before I had adopted this break-in technique.
It peeled the nickel off about 25% of the bore.
It still ran for years afterward, though, until it broke in a bad crash.

_____________________________

Sincerely,

Dar Zeelon - ISRAEL
[email protected]

MVVS Engines Support Forum

EXACTLY!!
THANK YOU SO MUCH HANKPAJARI!!! Thats it!

Mitty,

I have Dar Zeelon's method on all my ABC engines. It has worked every time without fail. He knows what he is talking about and if you use his methods you can't go wrong.

Regards,
doubledee

Mitty,


I have not (yet) written a thread, describing a special break-in procedure for ringed-piston engines.

This is because the customary, rich, four-cycling method, many use at most flying fields, works well for them.


Thank you David and HankPajari.

Don't forget there is a difference between breaking it in an properly tuning it.

I think there is one fallacy in that text. ABN is not more suseptible to plating pealing than true ABC - it's the process that is at fault when that happens rather than the materials. ABN is sincerely cheaper than ABC and it is an inferior hardness but it is a very good substitute (used in many full sized engines - like my Porsche's flat six) for true chrome.

Just an aside really.

Since this thread is about AB? type engines I thought I'd show you this Russian ZEUS .61, it is hands down the tightest engine I've ever bought. Even now with 10 to 15 hours on it, it still does a good imitation of a turkey call when turned over with the glow plug out. It cannot be turned over by the prop driver even with the plug out. As you can see it is wearing a Webra carb and SuperTigre swing muffler. The original carb and muffler were small, it is not a powerhouse by any means but is an interesting engine with absolutely beautiful machine work inside and out.