How do you break in a engine?

Can someone tell me the correct way to break in an engine.
?'s
What type of prop?
How long do you run the engine?
Time between runs?

Paul,

Randy Smith and I collaborated on an article for Stunt News back in March/April 1997. It was re-run in March/April 2000. Should be as appropriate today, as it was when written. Includes old style iron piston engines, the new ABC's, pipes, fuels, props, etc!

If you can't get hold of that, let me know and maybe I can scare up a copy for you.

Ward Van Duzer

Ward,
Not sure where I could find back issue of Stunt News? If know how I could get it via the net?
Thanks
Paul

Paul,
I have a copy of the 2000 article in both RTF and DOC format I could send to you electronically. The 1997 version (is different) is available only in print. This article was part of a two part article on "FUELS FOR STUNT" and "PROPER BREAK-IN PROCEDURES".

If your computer can open RTF or DOC files I'll send you those via email. If not I'll snail mail them (all) to you.

Please send instructions to [email protected] with "ENGINE BREAK-IN" in the subject line.

Otherwise you can get copies of back issues of Stunt News from PAMPA Products. If you are not a member of PAMPA, you NEED to join NOW!

>Can someone tell me the correct way to break in an engine.
>?'s

FIRST, WHAT KIND IS IT? This affects the fuel choice AND the rpm range that would be appropriate, and other aspects as well. Iron piston engines need a lot of oil in the fuel for normal running, and even more when new. High percentages of oil for modern engines may be an inefficient choice. Generally, SOME castor helps most CL engines, and Iron Piston engines' fuel mixes should contain no less than half castor when synthetic oil is in the mix.

>What type of prop?

Generally, smaller and flatter in pitch than the one to be used for flying. Iron piston engines need to be run slower when new. ABC and/or ABN or AAC engines need to be run just as fast new as they will be run when in normal use, and require VERY LITTLE breakin anyway.

>How long do you run the engine?

That's where the KIND of engine makes a difference. Iron piston engines could overheat the first few runs if operated longer than roughly 3-4 minutes per run.

>Time between runs?
>
Until it's totally cooled.

.

Kiwi

K,
This is a Fox .25 I got from the great guys in Tulsa.
It was in question if the engine was broke in or not.

>This is a Fox .25 I got from the great guys in Tulsa. It was in question
>if the engine was broke in or not.
>
All Fox 25's, TTBOMK, have iron pistons and steel cylinders. Therefore, the fuel should have even more oil than normal (more than 25%) in it, the rpm's should be less than normal, the prop should be a 7" to 7 1/2" club cut from a (wood) 10-4.

If it hasn't been run enough to be broken in, it should be "heat cycled" by running it in 3 minute sessions and allowing it to completely cool off between runs. To check on progress, you test an engine's ability to hold a lean setting for a few seconds at the end of the run. This is done by pinching the fuel line nearly shut. A new engine usually gets hot evem when running slowly, and too hot during the brief lean bursts to be able to run smoothly that lean.

Eventually, it *will* hold a steady lean run for that last minute of a run, without any excessive overheating, {if you can touch the cylinder fins with your fingers after shut down without discomfort (just a quick touch - some folks suggest a "grab" of the cylinder for this check)}, then it's probably ready to fly with.

.

Kiwi

Thanks Mr. K

I agree almost completely with Kiwi's instructions for an iron-piston engine

However, I believe that the first 5 runs should not exceed 1 minute, with the head-fin-touch-test following. And not just a quick touch to see if your skin sticks to the metal; a full quarter-second "grab"!

OK I have 5 one min. runs on this Fox .25. After each run I touched the fins and they are hot but not a OUCH! kinda hot. And I can hold it for a second or two. I only own two big props. One is a 8x6 and the other one is the one I am using during the break it is a 9x6. (I have a 9x4 on order) I am not sure what the RPM's are but the engine does not sound like it is running real fast. When I pinch the fuel line the engine runs much faster as it runs out of fuel.
Here is what I am thinking... if it is not real hot maybe it is broke in. (It was a in question when I got it from De Hill.)
If the engine is not broken in, at what point do I start to adjust the needle to up the speed of the engine. aka RPM's

Next run turn the needle in about 1/8 turn. Run it for a minute. If it does not sag, turn the needle in another 1/8 turn, and run again. Get it to where it barely speeds up when you pinch the fuel line. Now If it will run for a couple of minutes without sagging at that setting it is ready to fly. Open the needle maybe 1/4 turn and go fly. That will, hopefully, keep you from getting a lean run.

The term "sagging" is more obvious when applied to a plane in the air; the immediate effect of lessened speed is to start losing altitude. A fully broken in engine will keep running at a relatively lean setting that makes newer engines get too hot, and they slow down. With experience, you can hear fairly small changes in engine speed. You don't need a tachometer.

The usual way I describe the tests for whether an iron piston engine is ready to fly with is that your engine "holds" a steady full-lean setting for a full minute of running, and STILL doesn't get so hot you cannot perform the finger-touch check on it.

.

Kiwi