Breaking schedule for OS .15

[Anonymous]

I have a new OS Max III. How should I break it in? I have 25% nitro w/20%syn/cas blend for fuel. Also do they run consistently on pressure?

[DAN BERRY]

Dump the synthetic oil. All castor is what you want.
Put on the prop you’re gonna fly with and run it. A lot. And then run it some more. It takes a while to break iin that iron piston.
Pressure for certain.

[Anonymous]

Dan, will the engine run reliably even if only partially broken in?

[SIMON BLAKE]

Hi Randy:
Back in the day people used to break in a lapped piston motor like that for a good hour, running the first 20 minutes really rich and then gradually leaning it out. Pretty well all fuel used castor oil.
These days, it’s more a matter of where you live and what fuel is available. I live downtown in a large city so running engines in the back yard is out of the question. And the only good fuel available around here is Sig Champion, which I believe is a synthetic/castor blend. I have been using Sig Champion 35 in competition for at least 20 years now and it works extremely well in lapped piston engines like the Max III series. If you are using Sig 25 that should be fine for breakin and test flying.
On the rare occasion when I do have to run in an engine, I usually do it at a field during a competition because we don’t have a local flying field. So I try to keep it as short as I can get away with. Rubber/glider flyers get irritated! I suspect about 10 minutes running, starting rich and gradually leaning the engine out would be enough so that you can fly with that engine. The OS engines have always had a pretty good piston/cylinder fit from the factory. And they have a good needle valve which works fine on pressure. If it has a venturi restrictor, you should remove that.

[DAN BERRY]

Randy, you’ll know when it will stay lit. I have an OS 29 that took a lot of bench time to get to where it would stay lit without overheating. I wasted a lot of time trying to use a small prop. Dick Hall told me to break-in with theprop that I intended to run. It needs the correct load and fuel to get the temp correct. Then a run and cooldown cycle. Repeatedly.
Run it on the ground or in a plane until it will hold a setting without barking too much. In between flights with the Marval B might be a good option. 30-40 secs and let it cool. If you have neighbors with a Harley Davidson motorcycle, now is your opportunity to get even for all of their loathsome noise. 🙂
I would recommend a different needle than the stock one. I like the Supre Tigre clone that I get from Virginiahobbysport.com. No clicker, just a collet.
That engine wants castor oil, as do all the engines from that era. It will handle 35% pop, but I’d get it running smooth before jumping into that.
On bladder pressure, you can remove that venturi restrictor for a bit more RPM.
What size motor and prop are you working with?

[Anonymous]

I’ll be running with an 8/4 prop which was recommended to me along with fuel which may be 20% castor…..I’ll have to check on that.

The engine I bought on eBay and if I recall now it was converted to F/F with a better NVA. As I mentioned it is a new engine.

I’ll be flying it in Vintage F1C on a Ramrod 432 with a 20 second engine run (Yeah!). Thems the rules so I’m not complaining. I’ll be flying against several experienced competitors so I don’t have high expectations but I do want the engine to be reliable for the entire run. I can tweak things in later flying.

As you might guess I am burning the midnight oil to get the airplane and engine system ready for this contest which is in two weeks….my usual process. The last time I flew gas was about the time this engine was produced

[DAN BERRY]

Try a 7×4 APC.
You’ve got time. It just requires irking the neighbors.

[Anonymous]

Thanks Dan, I’ll give that a try……of course the neighbors are already irked.

[DAN BERRY]

Just remind ’em, you could be blasting a non-muffled Harley in the driveway.

[Anonymous]

First experience running the OS was a good one. After rigging up the pressure bladder and installing the 8/4 prop it started up pretty quickly and ran steadily. It touched 15,000 on the tach a couple of times on 25% “pop” and 20% castor. I ran the engine possibly a half dozen times and seems very consistent in those runs. After I’ve run it in I’ll start to tinker with some different props as recommended. Thanks for the help!

[JLorbiecki]

The tricks that I have always used for break in is to run them fast and somewhat rich- I would not run more than a 7 1/2 x 3 on it and let it run on 10% with castor. Run it for 2 minutes or so. It should be rich but not blurbling-

The idea is to get the heat up but still have plenty of fuel running thru it to keep it lubricated. If you do not get any heat in it, it will never break in-or take a long time. Run a few tanks thru it and then try leaning slightly. When it will hold a setting and run the tank thru, it is ready to throw…

Steel liners like to be broken inthis way- ABC and AAC liners are a whole different story- these need to be run hard and, if set up right, will only take a few runs to have them ready to go…

Good luck..

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