Vince, I've come to the following conclusion based on all inputs so far including those most intimate with the fuels, the manufacturers, model aircraft magazine writers, and long term serious engine enthusiasts.

The metallurgy of the legacy engines a generation ago utilize steel pistons or steel piston rings running in lapped steel liners. Cox engines utilize the same steel on steel and have steel connecting rods running in the steel ball and socket joints. For these, not using Castor oil in fuels could provide a shortened service life.

The following is stated in the manual for the OS 10/15/25 LA plain bearing Aluminum piston running in a Brass liner that is Nickel plated (ABN) engines:

ADVICE ON SELECTION OF FUEL, GLOWPLUG & PROPELLER Fuel [....] Synthetic oils are permissible but are less tolerant of a "lean run" than castor-oil. If, therefore, a synthetic lubricant is used in the fuel, readjust the needle-valve to a slightly richer setting, as a safety measure, in case the fuel/air mixture becomes too lean through maneuvers in flight. If a higher nitro fuel is used, the engine should be checked out to make sure that it is sufficiently run-in to operate on that particular fuel without overheating. Do not use fuels containing less than 18% lubricant.

Basically, one can get away with using fuels with sufficient synthetic lubricant in modern ABN or Aluminum piston running in a Brass sleeve that is Chrome plated (ABC) engine, including those with a bronze bushing supporting the crankshaft if prevented from overheating. However, use of Castor oil will protect a hot running ABN/ABC engine (overly lean air/fuel mixture, inadequate cooling - cowled engine, and/or using an oversized propeller).

Yup, sounds good to me. 20% is a safe bet for oil content. Steel on steel likes castor. ABC/ABN plain bearing likes castor but works fine with synthetic. ABC/ABN ball bearing don't need castor but a blend is a safe bet. It should be noted that little engines (of modern design) follow the same rules. All relating to planes of course. Heli's and cars and boats have their own rules...

Again, it's not typically an issue for the everyday sport flyer. Whatever is on the shelf at the hobby shop will do (typically a castor/synth blend) so long as you tune properly. I used to run everything from .049 up to .65 on 15% nitro with a castor/synthetic mix. But an old (or old design) engine is definitely safe with 20% castor oil in the mix.

Good info guys. See you all in a few months when this comes up again.

Cheers,
Vince L.

Originally Posted by OkiThumper

17 Nov 2012 Anyway, I was able to successfully run my Fuji .099S-II R/C engine today on O'Donnell 30% Heli Fuel with a Swanson Associates Fireball Hot Standard plug. Some time back I could not get it to run reliably on standard glow fuel, ended up using an OS Max 15FP that did. [....] It is baffle piston by design, but uses ABC construction with an aluminum baffle piston run in a chrome plated brass sleeve. It's got a rather low compression ratio of 5.5:1, putting out 0.16 horsepower at RPM's of 2,500 - 12,500, recommended props 7x4 (FF) or 7x5 (CL and RC). Weighs 4.3 oz. without muffler, heavy like an Enya. Interesting that they don't recommend the 8x3 or 8x4 props like Enya and older OS Max baffle piston engines do.

The instructions state a break in prop of 8x3. I found out from others that Fuji might have been seeking a flywheel effect with the heavier prop. Out of curiosity, I tried the Masters Airscrew (MA) 8x4 prop, not having an 8x3. I figured that at least should have the same flywheel effect, but might cause the engine to overheat because at higher RPM's it has greater resistance. Interestingly, the best flywheel action I had was from an MA 7x4 prop. It is heavier than the Tornado 7x4.

Now that I've got some time built up on the engine, I again tried the 8x4 prop. It spun it without complaint, a little lower in RPM but with respectable thrust. I don't have a tachometer; otherwise I could quantify it for others. There is an advantage to it's lower 5.5:1 compression. I haven't tried it yet on a 9x4 prop. The test will really be when test flying, TBD.

So, this little jewel, the last of the Fuji 099S-II as a baffle piston ABC (earlier were iron/steel piston in a lapped steel sleeve), is a respectable powerhouse for "A" size "nitro" slow flyers.

There is one caveat; thus far it still remains a hard to start engine, taking me over a dozen flips to start it. OTOH, my OS Max .10 baffle, .15 Magnum and .15 OS FP plain bearing Schneurles are easy to hand start, with only a couple flips on a chicken stick. (Didn't have an electric starter to verify the Fuji with.)

One good thing about this engine is the very finely threaded needle valve assembly. So, as cantankerous as it is, I've gotten her to work. (There's no welfare in my engine drawer.

I'm just curious if there are others out there who have had a stubborn to cooperate engine out there.

Oh, and I have a comment about the O'Donnell 30% Heli Fuel with 18% synthetic oil. Even peaked out, the Fuji was putting out an nice steely blue oil vapor mist from the muffler. So, it appears that the synthetic even on the 8x4 prop was doing its job. Perhaps it is time to bust some myths on non-Castor oil fuels?

Hey ! you can use ATF for all I care.
But I've ruined OPS abc pistons/liners on Synth oils.
These are/were pricey rascals, consequently a memorable lesson.
Synths are NOT near as effective as the Brochure Babbles claim Or the gullible believers, for that matter :-)
Castor is ugly stuff, but it Works.. 'nuff said.

Bare, weren't those OPS engines racing ones, with high compression heads? Perhaps run lean?

My ABN's / ABC's are all sport engines with lower compression heads.

The old stuff needs castor, otherwise it will make a nice trashcan deposit.
It's gooey, gummy, nasty, but it is the only thing that will preserve your old glow motor if you run it.
The old sparkies and diesels are another matter.

Actually JKinTX, today I ran Wildcat 15%. It's got Castor. Ran fine in the Fuji 099S-II ABC with 8x4 prop. After further running in, this engine with its low 5.5:1 compression seems to like the larger prop, turns with authority without overheating. Adjusted the low speed needle and idle, has a nice moderate idle. Looks like I found my engine for the Hobby Lobby electric Miss Stik Senior (55 inches or 1,400 mm span Texaco styled cabin floater).

Ran the Enya .19-VI TV for the first time since buying off E-Bay (attached). It is used but with a lot of compression. When I first got it, noticed the crankshaft was slightly bent; straightened it and mounted a Tatone EM-4 compact muffler. Running it today verified I properly straightened it,, runs true, pulls a 9x4 Master Airscrew prop with authority. Adjusted the low speed needle and idle, has a really nice tick over speed during idle.

The mounting holes show signs of being mounted on a plane. It takes a lot of force to bend a crankshaft, I figure it must have been in a crash. It came without prop nut and washer. I improvised a prop washer by drilling out a fender washer and found a nut to fit.

After several minutes running, the engine seemed unusually hot. Either I've got an engine that's not fully broke in, or the aftermarket muffler is too restrictive, IMO. I have a Tatone Peace Pipe muffler, will try that to see if it will help. If needs further run-in to break in, then, I really got a bargain (essentially a new engine).

I think I've found the ideal engine for Hobby Shack's venerable 45 inches or 1,150 mm wingspan The Real Thing. The .19 should change that from being a pussy cat.

Regarding my comments about heli fuel, I really shouldn't be so facetious. Out of curiosity I picked up 2 quarts. After research found it doesn't have Castor oil. Most manufacturers permit synth fuel in their ABC/ABN engines with the caveats that 1) above all, don't run engine lean; 2) don't run engine hot by overloading with oversized props. So, I plan to burn up this fuel in my ABC/ABN engines. For my steel lapped cylinder engines and the Coxes, I'll be running the Wildcat fuel with Castor oil content.

I don't have any ignition engines or really old, worn lapped piston engines, so I don't have to go there.

Originally Posted by OkiThumper

Actually JKinTX, today I ran Wildcat 15%. It's got Castor. Ran fine in the Fuji 099S-II ABC with 8x4 prop. After further running in, this engine with its low 5.5:1 compression seems to like the larger prop, turns with authority without overheating. Adjusted the low speed needle and idle, has a nice moderate idle. Looks like I found my engine for the Hobby Lobby electric Miss Stik Senior (55 inches or 1,400 mm span Texaco styled cabin floater).

Ran the Enya .19-VI TV for the first time since buying off E-Bay (attached). It is used but with a lot of compression. When I first got it, noticed the crankshaft was slightly bent; straightened it and mounted a Tatone EM-4 compact muffler. Running it today verified I properly straightened it,, runs true, pulls a 9x4 Master Airscrew prop with authority. Adjusted the low speed needle and idle, has a really nice tick over speed during idle.

The mounting holes show signs of being mounted on a plane. It takes a lot of force to bend a crankshaft, I figure it must have been in a crash. It came without prop nut and washer. I improvised a prop washer by drilling out a fender washer and found a nut to fit.

After several minutes running, the engine seemed unusually hot. Either I've got an engine that's not fully broke in, or the aftermarket muffler is too restrictive, IMO. I have a Tatone Peace Pipe muffler, will try that to see if it will help. If needs further run-in to break in, then, I really got a bargain (essentially a new engine).

I think I've found the ideal engine for Hobby Shack's venerable 45 inches or 1,150 mm wingspan The Real Thing. The .19 should change that from being a pussy cat.

Regarding my comments about heli fuel, I really shouldn't be so facetious. Out of curiosity I picked up 2 quarts. After research found it doesn't have Castor oil. Most manufacturers permit synth fuel in their ABC/ABN engines with the caveats that 1) above all, don't run engine lean; 2) don't run engine hot by overloading with oversized props. So, I plan to burn up this fuel in my ABC/ABN engines. For my steel lapped cylinder engines and the Coxes, I'll be running the Wildcat fuel with Castor oil content.

I don't have any ignition engines or really old, worn lapped piston engines, so I don't have to go there.

Enyas take FOREVER to break in. I ran nearly two gallons of fuel through the last .15 I had and it was still too tight.
If running any type engine that uses the case as a bearing material- CASTOR, otherwise you won't have an engine that runs well for long.

JAK

Originally Posted by JKinTX

Enyas take FOREVER to break in. I ran nearly two gallons of fuel through the last .15 I had and it was still too tight. If running any type engine that uses the case as a bearing material- CASTOR, otherwise you won't have an engine that runs well for long. JAK

AFAIK, I have no engines like that. They all have at least bronze bearing inserts.

Yes, that is what I have gathered.

However did find one oddity. I mounted in the test stand today a Gilbert .074 Thunderhead engine I bought some 5 or 6 years ago from Tower Hobbies. It was in one of their special sales flyers. for under $15. Crankshaft has considerable wobble, quite noticeable. I'll find out more when I run it tomorrow.

I'll second the advice here, in that I fly my engines on a mixed castor/synthetic homeblend of fuel. I find that 10% castor / 10% synthetic is a good blend for smaller, older type engines such as the Cox .049's that I like to run. They seem to thrive on it so long as its got at least 15% nitro in there, too.

Anything larger I generally run zero or 5% nitro, 9% synthetic and 3% castor. This might seem like low lubricant levels to some but it does work and my engines haven't lost compression... well at least not yet! I also like a grade hotter plug than standard to take advantage of the low or no nitro fuel.

Having said all that there is a guy at the field who runs FAI 20/80 mix exclusively and has been running the same OS .46 for over 20 years without problems.

Cheers - boingk

That is quite a testimony, boingk on the OS .46 and FAI fuel. A case of 4 gallons Cool Power Omega FAI fuel with Synth/Castor oil blend costs $50.99 US ($48.80 AU) from Tower Hobbies. Same fuel with 5% nitro costs $61.99 ($59.33 AU). It goes proportionally up with additional nitro. If one doesn't need nitro, there's a cost savings.

Is it just me or my observation has some truth? The Wildcat fuel with Castor/synth oil blend did seem a touch more slippery when flipping the props than all synth oil fuel.

Originally Posted by OkiThumper

AFAIK, I have no engines like that. They all have at least bronze bearing inserts.

Yes, that is what I have gathered.

However did find one oddity. I mounted in the test stand today a Gilbert .074 Thunderhead engine I bought some 5 or 6 years ago from Tower Hobbies. It was in one of their special sales flyers. for under $15. Crankshaft has considerable wobble, quite noticeable. I'll find out more when I run it tomorrow.

Crank rock is a character trait of these it seems, at least on the ones I have seen.
If you run any Cox or other similar .049s (which is what this thread was about to start) these are all shaft in case bearing engines with no bushing and they need the castor, otherwise you will have crank rock out the wazoo real soon...

Not just you mate, the Castor really does give some slip to the feel of a fuel.

One reason its so good - apart from helping any flashspot temps - is that it exits the engine unburnt and helps to dump excess heat very effectively, thereby actually helping keep your engine cool both through lubrication AND waste heat management.

I tend to run at least 1.5% of castor in my models because of these advantages. Plus it gives me the 'warm fuzzies' and smells good when the engines running, too!

Prices locally for methanol are $1.50 a litre, and nitro is $20 a litre. Castor is also $20 a litre (Castrol R30 from autostore) and synthetic is roughly similar. Thats why nitro based fuels are so much more expensive, especially if you don't mix yourself.

If I run 83% methanol, 5% nitro, 3% castor and 9% Klotz (my .46 mix) then I'm looking at a mere $4.65 per litre of fuel. Compare that to my 1/2A mix which I'm using at 67% methanol, 15% nitro, 10% castor and 8% Klotz; its worth $7.60 a litre, or $8.60 with 20% Nitro. More expensive, yes, but much cheaper than the premixed stuff!

FAI fuel, for comparison, is $5.20 a litre - more than my 5% nitro .46 mix. Thats due to its higher amount of lubricant, which is worth the same as nitro.

Gotta love homemixing fuels!

Cheers - boingk

PyroMan,

I just looked at your restoration-your motor looks beautiful!

If it helps any, I have been flying Wen Mac and Testors engines again for the last few months.

I just went through (last Saturday) three Testors and Three Wen Mac motors (in most cases, the Rotomatic clutch was glued together from castor oil for the last 30 to 50 years (the engines are of varying age).

Once freed up, the engines all ran well.

I have been using Glo Plug Boy fuel. Initially, the Testors and Wen Mac engines did not start well on this, and the needle setting was interesting (finicky and would not hold well). Cox .049's ran fine on it.

I remember, a very long time ago (when these things were relatively new), I had no trouble starting them, while some of my friends did. They were using Cox fuel, while I was using Testors fuel.

Some years later, I ran a Wen Mac engine and a friend who was an old school control line person, made a comment about the smell of the fuel. He said that it smelled like there was ether in it, and that was why the engines would start easily and run better on it.

You cannot buy ether, because it is used to make drugs. A fuel manufacturer directed me towards engine starting fluid (for carborrated automobiles and tractors). I found some that was 50% either.

I just sprayed a bit into the Glo Plug boy fuel and now the Wen Mac and Testors motors start like they used to-very easily. Two of them started on the second flip.

Not scientific, but the engines run very well.

Originally Posted by Ah Clem

PyroMan,

I just looked at your restoration-your motor looks beautiful!

If it helps any, I have been flying Wen Mac and Testors engines again for the last few months.

I just went through (last Saturday) three Testors and Three Wen Mac motors (in most cases, the Rotomatic clutch was glued together from castor oil for the last 30 to 50 years (the engines are of varying age).

Once freed up, the engines all ran well.

I have been using Glo Plug Boy fuel. Initially, the Testors and Wen Mac engines did not start well on this, and the needle setting was interesting (finicky and would not hold well). Cox .049's ran fine on it.

I remember, a very long time ago (when these things were relatively new), I had no trouble starting them, while some of my friends did. They were using Cox fuel, while I was using Testors fuel.

Some years later, I ran a Wen Mac engine and a friend who was an old school control line person, made a comment about the smell of the fuel. He said that it smelled like there was ether in it, and that was why the engines would start easily and run better on it.

You cannot buy ether, because it is used to make drugs. A fuel manufacturer directed me towards engine starting fluid (for carborrated automobiles and tractors). I found some that was 50% either.

I just sprayed a bit into the Glo Plug boy fuel and now the Wen Mac and Testors motors start like they used to-very easily. Two of them started on the second flip.

Not scientific, but the engines run very well.

Thanks! Just out of curiosity, are any of your Rotomatic springs still functional? My spring was broke when I got it and I read online that most of the springs these days are broke because of the age of the engines.

I'm a little worried about my engine. I've had it on my desk the last week or two as a reminder to buy fuel for it (which I've yet to do), but when I flip the propellor it doesn't seem to have very good compression. Compared to my .15 size engine's compression it feels like something is wrong with the .049. Now I know there is a large size difference and therefore a large conpression difference, but still I feel like it should have a but more resistance when flipping the prop. Is there a way to check the compression?

About the ether, I'll keep that in mind if I can't get the engine started. I have multiple cans of starting fluid around here of various brands so I should have something that could work.


Thanks,
Nicholas