I am wondering how much castor oil to add to a half-gallon of Tower fuel for breaking-in my OS 46AX.

I have a half-gallon fuel mixing jug, and a bunch of quarts of Tower fuel, which is 10% Nitromethane and 18% synthetic lubricant. I heard somewhere that you can add an ounce or two of castor to increase the oil content, and to add a more protective oil to the blend.

Any advice?

Thanks.

Get a quart of Benol castor from tower,, just take the full half gallon bottle and fill it the rest of the way to the top,,thats what most of us do that fly 1/2a to add castor in.....Rog

I wouldn't worry about it. I've never altered my fuel for breakin. Just break it in by the book and you'll be fine. With my 46 AX, I just richened it up for a few runs, but not sloppy rich. Just messy rich, but still 2-cycle mode. Let it get hot so the taper and piston will fit right. After just a couple of tanks, I put it on the plane and flew it. Continued a bit rich for the first gallon of fuel, and then leaned it out after that. It runs like a scalded dog. I would like to see a stronger .46 produced--I don't believe it's out there.
You'll love this engine. Perfect runs right out of the box. This thing has NEVER flamed out on me, not even during run-in. It idles pefect, and the top end is unbelievable. BTW, I own a lot of different engines--magnums, saitos, zenoahs, weed-wacker conversions, evolutions, OS, the list goes on and on. This one is one of my favorites....can you tell?

How much castor to add?

None

The engine will break in perfectly if you use that fuel and do what the instructions in the manual suggest.

I've lost count of the number I've done for guys at the field and done a number of my own. It's a product that does what it's advertised to do. It breaks in excellently well on just a run or two, doing the needle twiddling that the book suggests.

Every one that we've broken in as recommended is still running like gangbusters. A number of them are going on 3 years old.

I agree with 2slow2matter. Yes, I know that some of the engine manufacturers say to use castor only blends for break-in but I have never had a problem yet. I have use Cool Power 15% for almost 10 years now and never had one single engine problem resulting from synthetic lubrication. IMHO the real key to breaking-in an engine is to take it easy on the engine for the first 15-20 flights. Keep the engine running rich and you'll never have a single problem with it. I wouldn't worry about adding castor to your fuel, all that's going to do is build up brown gunk on the muffler!!

Ken

Wow, not the answer I was expecting! I thought I mentioned to here that I got Tower fuel, without really knowing the oil content, and people said that I should add castor oil to it, with some reference like you shouldn't feed your baby food when you don't know what's in it, or feeding your dog the worst kind of dog food 'cause it's cheap. The manual does say to use castor oil or castor blend if possible, but that it will run fine if you don't.

I guess I should have gotten a receipt for that bottle I just bought!

Oh well, thanks guys, this makes it a lot easier.

I run in every engine, regardless of type, using 25% all castor because there's more parts in an engine to run in than just the piston/liner. Mainly the conrod. If you read the Jett instructions they say it takes around 30 minutes to run in the rod while the piston/liner is done in the first few minutes. Castor is a far better oil for a plain bearing to run on so that's what I give them at the beginning of their life.

If you said before that you wasn't sure of the oil content, I would agree that adding some castor oil would be a safe precaution. However, above you stated 18% oil content, so there is no need to add anything. You probably recieved the recommendation to add the castor oil simply because of the unknowns you had stated. The oil content (percentage) is much more of an important factor than the type of oil used be it synthetic or castor.

Breakin used to have a huge effect on performance back in the days of iron pistons and wide tolerances.

A quality engine today is CNC produced and the alloys are amazing. Experience shows that the OS46AX does not need yesterday's breakin. If you choose to do it, no problem. It'll eventually break in when it finally gets warm enough, and when enough revs have worked in every surface that needs just that. Which happens in a couple of runs anyway.

And if you want to feel more secure no matter what, then add a bit of castor. It won't hurt unless you put way too much into the mix.

Castor isn't magic except for one property. It will stand up to damaging high temperatures. The engine won't see those temps at all unless you screw up the needle adjustment and run the engine too lean. So nowadays it's insurance for them what feels the need of assurance.

You're right! At first I couldn't find the oil content of Tower's fuel; it doesn't say anywhere on the label. I think that's when I started hearing stuff and asking about oil content and adding castor. I later saw that they advertise that it meets OS Max specs, so it SHOULD have at least the 18%. I am assuming that it is a synthetic blend because a search of Tower's fuels show the only ones that contain castor are the premium blends, which Tower's generic fuel obviously is not. Nowhere does it actually say that the fuel is 18% lubrication, but again, it says it meets OS Max standards.

Well I have 6oz of castor that I have no other use for, and 3 quarts of tower fuel. From what I'm gathering from this thread it wont hurt to mix it together. Using all 6oz would be a 22.8% oil blend, which is OK to use for the first 3 quarts?

Since you have the castor handy, you might as well add it to the fuel. It definitely will noit hurt anything. Having 22% oil just means the percentages of alcohol and nitro are slightly decreased so you'll have slightly less power than you would have without the added oil.

..............and hope that it doesn't gum up your needle valves.

You could keep it for those times you just can't go poop....

With engines, fuels and this hobby.....everything is a compirmise If it gets too difficult....well profit suffers. So there is a tendancy to make it more user friendly and easy so that something like fuels, oils and breakin are not scary and confusing.

Even with tolerances being closer and beter metals used in engines, there are a few things that have not changed. Friction in a new engine is going to be more than in an engine that has been broken in, thats a constant....more friction = more heat, and not just higher engine operating temps, localized heating of certian components.

Picture this, the moment that ingition takes place in an engine, the piston is accelerating, the rod is under compression and the pressure is felt at the small end on a very small surface area and the large end on a somewhat bigger area in comparasion. Oil tends to squeeze out, now with the parts being new, there is more friction and heat. You want an oil that sticks in there and does not squese out and or allow metal to metal contact.

I know how hard castor oil is to clean up, it tends to stick to everything, which is a good thing for breaking in engines. Also in addition if things get too hot in one area castor does not leave the scene and forms a varnish that like a calus on your hand stays there to protect the parts. I guess one could say when the going gets tough, well castor just gets tougher.

I break all of my engines on minimum of 50% castor and 50% klotz at a total content of 25%-28%. If I use Omega, I will add a considerable amount of castor to the mix prior to breakin. I add 4 oz of castor to Omega as a normal fuel once the engine is broken in.

More lube during breakin will not hurt anything and castor has the ability to protect the engine parts if things get rough.....

Thats what I do....everyone has a different decision to make and there is no wrong decision

Richard