"break-in" props
 

Are break in props really necessary ? why cant you just pick an appropriate size for the engine you have and just fly ?

RE: "break-in" props
 

You can
It's more important not to let the engine overheat like from running it on a bench, long uplines ,or hoverbatics.
Once things have a chance to heat cycle a few times by flying it easy for a gallon or so to lossen up leter rip.
Look at the breakin for a weed whacker oh there isn't any and they live a life of torture.
If an engine isn't machined correctly no amount of brealkin will fix it.

RE: "break-in" props
 

Ditto

RE: "break-in" props
 

Depends on the type of rings and cylinder wall lining. Sorta of speculating, and a bit from experience, but I think if your engine has twin or one smallish ring, more care is needed to allow seating to take place. Putting to large of a load might cause excessive amounts of hot gasses to leak past the rings and then all sorts of bad things happen. Larger single rings or duals from my experience tend to not need as much tender treatment. It's taking more than 12 gallons of fuel to get the rings seated in my currant engine. Two small rings. I've kept trying to put the larger prop on but only recently has it not lost compression when switching to the larger prop.

RE: "break-in" props
 

So what event or measurment to you use to say the rings are seated
and how did you determine the engine lost compression with a larger prop
do you do a cranking compression check or a leak down check
just curious you never can learn enough in one lifetime

RE: "break-in" props
 

Just by feel. After the engine is all cooled down its was very easy to pull the prop through compression after running the 28x10 prop. Then I'll put the 27x10 back on and it will rebuild the seal. About the last 6 flights have been on the 28x10 and it is holding compression. Still not quite as good as with the 27x10 and I'll watch by feel to see if more time is needed on the 27" prop.
I have a 3W56, it has one big ring. It has built and maintained compression from day 1. Using straight syn oil it took some time to get there. But it never fell off from having too large of a prop.

RE: "break-in" props
 

A leak down test is the most accurate. It provides a more accurate idea of the ring condition. A basic compression juts shows that the rings are maintainting a seal over a few revolutions. As for the break in prop thing, it's all about heat. Load an engine too much and it gets hot. That can be done with either a prop, too low or too high rpm, or all three combined. Keeping an engine within a "safe" temperature zone and load will not be a problem. A smaller prop than required for flight is the easiest way to avoid "loading" an engine, but keeping a new ringed engine too cold doesn't do it any favors.

For me, once an engine has lost compression I've never got any back. But that's just me. I have to replace the ring at minimum when it happens. Better to replace the entire top end but that gets pretty expensive in a hurry.

RE: "break-in" props
 

Fire up that engine thats been sitting all a lonesome in your Suk for a year and a half and learn a new 1 or 3 new ways to break in the worlds most PITA engine.

RE: "break-in" props
 

That's coming very soon. Prolly need a breaker bar to break the ring loose from the cylinder wall.... Btw, it's a Yak;)

RE: "break-in" props
 

I had chainsaw given to me that was frozen I poured about an once of wt40 in put the sparkplug back in and hit it with a heatgun did the heat and cool thing 4 times and put a strap wrench on the flywheel and she came free and seems no worse for wear

RE: "break-in" props
 

ATF is pretty good at this, as well. It takes patience and persistence a lot of times, not brute force.

But I bet Pat already knows that...;):D


Mark