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Post  crankbndr Fri Jan 04, 2019 1:39 pm

Towards the end of the spark era Dooling recommended castor and methanol and Im sure nitro and other chemicals were tried.
The racers were blowing these up with exotic fuels. I read the early gas sparkers used gas and 90 W oil.

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This is a spec sheet for the Dooling
cox 049 gasoline - Page 2 Scan10


Another guy named Underwood set out to strengthen the crankcase and made the Yellowjackets, these are rare and very collectable. Mine is a repro from Woody Bartelt.
The Dooling parts would fit the new case.
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Post  wmazz Thu Jan 10, 2019 9:15 pm

GallopingGhostler wrote:
Gasoline has a higher heating value than Methanol. It would be more economical as one doesn't need to carry as much fuel as they would with glow.

The prospects seem promising

That is certainly the up side, but rc gasoline conversions are hard on the con-rod
bearing. An RC car manufacture sells a gasoline conversion (~.32) and it uses a
roller bearing on the connecting rod to prevent failures.


Bill M.

I wonder if leaded gasoline made small engines more reliable?
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Post  GallopingGhostler Fri Jan 11, 2019 6:04 am

wmazz wrote:
GallopingGhostler wrote:Gasoline has a higher heating value than Methanol. It would be more economical as one doesn't need to carry as much fuel as they would with glow. The prospects seem promising
That is certainly the up side, but rc gasoline conversions are hard on the con-rod bearing. An RC car manufacture sells a gasoline conversion (~.32) and it uses a roller bearing on the connecting rod to prevent failures.

You have a point there, Bill, something I hadn't considered in my statement, and there is a scientific reason behind that con-rod bearing failure.

SMOKEmUP: Fuel Comparison: Gasoline, Methanol, Nitromethane

Gasoline has an air fuel ratio of 12.8:1. Methanol has an air fuel ratio of 6.0:1. This is why one gets a longer run time with gasoline over methanol. Roughly twice as much methanol is required to maintain combustion. Even if one retains the same 2 cycle oil (Castor/Synth) quantities, during the 2 cycle combustion, that fuel oil mixture is roughly halved, meaning that the interior bearing surfaces receive roughly half the oil that they would normally get with methanol.

I wonder if leaded gasoline made small engines more reliable?

Over time, gleaning from various automotive magazine articles, lead in the fuel, besides being an anti-pre-ignition knock agent, lubricated the valve seats and valve face that contacted the valve seat. Without required going to hardened valve seats and valves. This also went for 4 cycle small engines that didn't mix oil with the fuel for lubrication.

If it benefited 2 cycle small engines? It could be possible there was, but with oil already in the fuel for lubrication, appears that any additional benefit was probably minimal, except that in the case of high compression engines helped to prevent pre-detonation.

The 1934 Brown Junior 10 cc (0.60 cu.in.) petrol engine had a compression ratio of 6.5:1, and as such it was preferred to run on white (unleaded) gas due to its low compression ratio not requiring octane boosting.

Your thoughts? - George
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Post  wmazz Fri Jan 11, 2019 10:33 pm

Nothing scientific to add, but I have first hand experience with the NGH 9cc RC gasoline engine.
I participated in a long thread @rcgroups. I was initially interested in the NGH because it used
a version of a float diaphragm carb similar to what Watercraft carbs from SeaDoo's and JetSki
used, but also similar the Walbro carbs I used on GoPeds and RC Zenoah. In fact the pump and
diaphragm used Walbro parts.  

Besides the carburetor problems, connecting rod bearings failed. There was talk about oil ratio,
and some people ran oil ratio similar to larger engines. But the owner of NGH thought it was caused
by the engine leaning out, possibly while someone was tuning the carb for peak performance.

Since then I have watched other companies produce miniature gasoline engines like the 1/8 RC
car/buggy. It showed up in a few model shows, but its release took a couple of years, and resulted
in a roller bearing connecting rod and a plug cap integrated into the tall cylinder head.


Bill M.
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Post  GallopingGhostler Sat Jan 12, 2019 12:02 am

Bill, being curious, I took a look at the engine manual for the Evolution 10GX 10cc Gas Engine with Pumped Carburetor (EVOE10GX2).

Horizon Hobby: EVOE10GX2-Manual-EN.pdf

Towards the back is the exploded parts diagram, surely enough the lower end of the conrod assembly has a removable bearing. Whether it is a ball bearing or bronze one, that I can't tell from the diagram, but usually bronze bearings are pressed in and not considered as user serviceable and usually not shown on parts diagrams, so it is probably a ball bearing.

The Brown Jr. used a fuel oil ratio of 3:1. Oil was 60W mineral oil. Its conrod has bronze bearings. Both the Evolution and NGH use a 20:1 fuel oil ratio, oil being 2 cycle oil.

Don't have any experience on these very little gassers for model aircraft, so I can't speak from experience. I'm wondering if one were to use Castor oil as significant component in the oil mix might have helped to prevent conrod bearing failure in the NGH 9 cc. Don't know if having some Castor content may gum up the carburettor.

If there is better success with the 10GX, it would seem than for only $60 more might be a better engine. Again, I haven't really kept up with these engines.

I did notice though that Horizon is offering the 8 cc Evolution gasser, which is a touch smaller than the NGH.

At one time, Hobby King had the NGH 9 cc on sale for a touch over $100. Since you mentioned about conrod bearing problems gives me a sense of relief for not jumping onto the band wagon.
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Post  robot797 Sat Jan 12, 2019 3:14 pm

cant the lac of oil be solved with more oil
like I use 20% oil right now
but if I were to use 40%
I get more lubrication and I have to open the needle a bit

I see only pro's (and one con with that methode)
finer control over fuel (I only have half a turn right now and its twitchy)
more lubrication
heat gets removed quicker (with the unburned oil)
the con is the fuel tank get emptyed faster


ps I found a use for the conversion
it will be build onto a 80 car (to bad it aint a cox car)
and it will be something to brag with
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Post  wmazz Sun Jan 13, 2019 2:33 am

The NGH had tuning constancy problems too. The first engines used
exhaust pressure, but that led the engineer to use a modified Walbro
carb to supply fuel. But that set-up had problems keeping the needle
and seat open.

Perhaps a finer tapered needle valve. The original Cox needle was designed
for nearly twice the fuel flow compared to gasoline. A smaller diameter
venturi may help too.

For any of my high performance engines, I like using a rich oil ratio, and
I prefer the fortified castor Maxima sells as "927."


Bill M.

I don't know what 20% oil is like, we use ~5% on the racing engines and
the NGH. Perhaps 6 to 7% maybe a better starting point.
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Post  gkamysz Sun Jan 13, 2019 9:56 am

40% oil is excessive. Is there evidence of problems at 20%? Oil doesn't cool the engine significantly. Adding castor won't save a rod bearing, unless the oil you are using has extremely low viscosity. I fine thread needle would certainly help here. I don't know enough about which horseshoe backplates have them, but I have a couple with the 128tpi needle.

NGH9 has a lot of problems overall. I got a blown one to see what the problems were. The crankshaft heat treat is bad. The original and spare were both soft. This wouldn't cause immediate big end failure, but longevity is questionable. I just don't have much to day about poorly developed and built engines.
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Post  robot797 Sun Jan 13, 2019 1:09 pm

well currently
I only have a problem with the fuel supply when I wanna run the engine rich
it wobbles between flooded and not flooded
so the needle is good enough for high rpm
and I am thinking of extra oil just as a precausion
(also I mix synthetic and organic oil that is why i think the oil will pull some heat away)
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Post  gkamysz Sun Jan 13, 2019 1:15 pm

As long as the needle is allowing you to tune it where you want it. At very rich settings, factors other than the needle itself come into play.

If you calculate how much heat the oil can carry away, vs. total heat input from burning fuel, you'll see it's negligible.
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Post  robot797 Sun Jan 13, 2019 1:44 pm

true true
but even then themore lube the better XD
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Post  gkamysz Sun Jan 13, 2019 2:49 pm

At some point you're just throwing money, even if it's pennies in this case, through the exhaust.
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Post  robot797 Sun Jan 13, 2019 2:59 pm

Very Happy
gasoline is like 10 times cheaper as nitro
i dont mind trowing pennies away
if it means the engine runs better and longer
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Post  GallopingGhostler Sun Jan 13, 2019 7:34 pm

Regarding 40% oil content, somewhere I read, it may have even been the well known engine tester Peter Chinn, (or Paul Gilbeaut?) that the practical limits on oil content (all Castor) was 25%. This was due to the small passageways in the fuel system, couldn't handle the thicker viscosities of the fuel oil mix well.

Greatest concern in the Cox engines has always been maintaining adequate lubrication of the ball and socket joint for the con rod piston end. It is below the hottest area of the piston where combustion occurs. Castor has a higher flashpoint, doesn't vaporize as readily as synthetic oil.

If Castor can keep this socket joint lubricated, I can't see why it can't do the same for the lower con rod end at the crankshaft.

You do have one advantage to attempting this experiment on a Cox engine. Parts are relatively cheap and available, so if excessive wear occurs, it is easy to fix. Since I know of no one else attempting this experiment, you're developing valuable experience that can be shared with others, if they decide to do so.

Going to all Castor 20% to 25% may be a way to go with gasoline? With oil basically cut in half due to the greater stoichiometric efficiency of gasoline and increased heat while running, using all Castor seems to have merit, no?
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Post  robot797 Sun Apr 28, 2019 9:46 am

i made the final decision
i am gonna build it into a boat
i got a 051 tee dee for cheap
the hull i plan on using isnt build for speed but to compensate for that i am planning on giving it a kitchen rudder (just to be weird)
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Post  crankbndr Sun Apr 28, 2019 10:57 am

One of the unique properties of castor is it is soluble in alcohol, gasoline not so much. You might want to try gear oil or other heavy weight oil in gasoline. Two Cents
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Post  robot797 Sun Apr 28, 2019 11:26 am

castor desolfes just fine for me
also it is used in race 2 stroke dirtbikes
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Post  gkamysz Sun Apr 28, 2019 12:43 pm

Castor made for gas engines aka Klotz Benol, Maxima Castor 927 will have no trouble with gasoline, though most will say something about coming out of solution at low temperatures. Drug store castor will generally not blend with petroleum solvents. Virgin castor oil is processed to allow this. An alternative is high viscosity "racing" two stroke oils.
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Post  robot797 Sun Apr 28, 2019 12:53 pm

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Post  GallopingGhostler Sun Apr 28, 2019 4:36 pm

gkamysz wrote:Castor made for gas engines aka Klotz Benol, Maxima Castor 927 will have no trouble with gasoline, though most will say something about coming out of solution at low temperatures. Drug store castor will generally not blend with petroleum solvents. Virgin castor oil is processed to allow this. An alternative is high viscosity "racing" two stroke oils.

That may explain the higher cost of the Klotz Benol over drug store Castor. Anyway, I use it to supplement my store bought glow fuel so I can run my old iron piston with carbon steel sleeves engines without damaging or excessively wearing them out.
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Post  gkamysz Wed May 01, 2019 8:39 am

Two stroke castor is hardly just castor oil modified so it blends. There are generally additives to further improve it's performance. Maxima Castor 927 runs so clean it's amazing.
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Post  GallopingGhostler Wed May 01, 2019 9:55 am

robot797 wrote:https://eurol.com/en/products/eurol-racing-1-ricinus/
this is the stuff i use

Thanks for posting robot797, I didn't even know such an oil existed. Smoking

I would have to check (can't find the Duke Fox ad/article I saved), but wasn't Castor oil with a flash point around 550 Deg F? Eurol ricinus is 300 Deg F. I haven't used Eurol or equivalent, may be okay (in my humble opinion, which may leave a lot to be desired Old Bugger ), but if I had some, would probably relegate it to stunt and non-rigourous sport use. Tired w/ Coffee Read drunken
(Again, I'm not being critical because I am not an engine authority nor ever pretend to be. Embarassed ) lol!

gkamysz wrote:Two stroke castor is hardly just castor oil modified so it blends. There are generally additives to further improve it's performance. Maxima Castor 927 runs so clean it's amazing.
Perhaps that is why Klotz Benol Racing Castor smells like Klotz. lol!
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Post  roddie Tue Jun 27, 2023 9:01 pm

Bumping this thread.. because I'm curious if there's been any further thought/development on an ignition system with components lightweight enough (an airborne system) to power a 1/4A/1/2A single-engine model. I'd guess it'd need to be a radio control or free-flight cabin-type model.. as opposed to a U-Control type?

And what of the fuel? Maybe methanol will continue to be available for a while. Will it run on a CDI ignition? If not; then how about Coleman (known as white gas) stove-fuel? Is castor oil generally soluble in Coleman fuel?

A short query of Wiki doesn't answer those questions.. but tells me that Coleman fuel burns cleaner and is more highly refined than gasoline. Today's white gas aka Coleman-fuel contains very low Benzene.

Some observations of the O.P.'s (Peter's) video:

He's running a Cox .049 reed-valve engine with a spark-ignition and a two-stroke gasoline mix of 20% oil with 1/2 castor and 1/2 hybrid racing-synthetic I believe. Would that be a 20:1 mix?

The engine (as configured...) looks to have a conventional/Cox grey-plastic/"Horseshoe-type" carb. and there's admittedly a Cox-stock coarse-threaded NVA installed. noted.

There's a flywheel on the output side of the crankshaft.. which serves as a finger-flick start.. which is impressive in itself. Ease of starting... and zero reliance on cooling via an aero-prop mounted.

There's a Cox OEM heat-sink clamp which encases the top of the engine.. around the hottest part.. and helps to further dissipate the heat.....

and finally.... there's a custom-made [i]enclosure[/i.]... Huh... somewhat like I've been working on.. which re-routes exhaust-wastes out through a tube... Looks heat-restrictive (to the cylinder..) to me.. being of metal-skin.. It looks heavy too.. curious as to what it's made from.

My A Cheap Sportr Muffler thread has the back-pages...




I hate the thought of our little IC engines going the way of the buggy whip..
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Post  GallopingGhostler Tue Jun 27, 2023 11:51 pm

Roddie, just my personal opinion, but I think that adapting our little half-A reed valve gems to white gas might be impractical, due to the insufficient oil content to sustain the plain aluminum crank bearing and piston steel socket surfaces, which gets the greatest amount of heat. This is why 2 stroke small gas engines have crank roller bearings.

Even at a slightly richer 12.6 stoichiometric (12.6 parts air to 1 part gas) means that if you put 25% oil in fuel (oil is basically inert - for sake of discussion) reduces slightly the air required, you still roughly halve the available lubricating oil over methanol. Gas also runs hotter because it has a higher heating value.

Perhaps a conversion to diesel, if diesel fuel is easier to obtain and mix, may be the better alternative? (Haven't got a clue on availability of fuel components.)

Sanye ASP .52 (9.0 cc) gas burner seemed to be the smallest practical production gas engine. Evolution (still Sanye) went with a .60 (10 cc) gas burner. The spark electronics is the weight gainer. OS and Norvel went with a special glow plug that ignites in gas, but those are still larger than our .049's.

I'm not a fuels guy, maybe someone else can chime in.

There is an interesting discussion of fuels in this article:

https://www.enginelabs.com/engine-tech/by-the-numbers-tuning-with-air-fuel-ratio-and-lambda/
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Post  robot797 Wed Jul 12, 2023 6:04 am

of course the cdi can burn methanol
it starts even easyer

as for the lubrication
I have run the little engine for a few hours and it still runs great
it runs hotter but that is normal is there is less oil to carry heat way

as for the mix you could just add more oil and run it richer

the exhaust I use is tatone I like them because they dont have much restriction

as for why I did this
it is getting harder to get nitro here
and I want a solution so that I still can run engines

I also updated my design a bit
it now can run a prop
and the mount for the engine also holds the hall sensor
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