Hobbico's "Cox Super Fuel"

Can't say this would be relevant to Cox engine fuel but we run Castrol Semi-Senthetic engine oil in our Ford 4.2 V-6 and with good results.

Is the prejudice against senthetic lubricats based on factual documentation or traditional thinking?

SD

I am against synthetics from experience. When I got my first Cox engine I ran it on Cool Power. This was before I knew of this forum or the requirements for Cox engines. The engine lasted a very short amount of time before it was clapped out. Zero compression and the ball and socket was showing serious amounts of play. I got my second engine and ran it on Omega fuel. It had a small amount of castor. The engine showed the same fate as the all synthetic Cool power fed engine. The ball and socket did fare better though.

The Omega had about 5% Castor. 17% total oil and it still mangled the engine.

RR

P.S. We now only run Sig Champion for Cox engines. We mix our own fuel for anything else. We have yet to have an engine wear out since the fuel switch about 2 years ago.

I'm actually thinking about doing a test on a few engines to see what happens. How long would you say it took for the engine to wear out?

I ran a fuel very much like this one and the engine started showing signs of burning up after 30 minutes of runtime or so.  It now needs a new piston and cylinder. I'm running SIG Champion 35.

You'd have a hard time making it 50/50 oil, and still have the total oil content around 17-25%.

Four Cycle water cooled auto engines and 2 cycle air cooled aircraft engines are completely different and I think the answer to Super Dave's question is mixed between tradition and sound technical reasoning.

Too many manufactures ALL demand a specific oil content and some proportion to be castor oil for a reason. They engineered to engine and know perfectly well the failure modes they see on warranty returns. I doubt any of them have a monetary interest in the production or sale of one oil over any other oil. Meaning I tend to believe the Enya, ASP, Fox, McCoy, Cox, Norvel, Magnum, and Rossi literature of all the engines I currently own... every one I listed requires some percentage of the total oil mix to be castor oil

OK that is my .02c

WingingIt74 wrote:I'm actually thinking about doing a test on a few engines to see what happens. How long would you say it took for the engine to wear out?

Do not even try full synt lube unless you explicitely want to ruin your engine. Cox engines have been designed for castor that leaves a thin varnish on wear parts that practically separates metal parts and while thus avoiding metal-to-metal contact and wear, will also seal occassional micro-scratces on the soft cylinder wall and will thus heal engine wear.

I have COX engines that have run 50+ hours (especially Tee Dee 010-s are undestructable) that show original compression. All I had to do was reset the balljoint 1 or 2 times...

As only a few  vendors in Hungary sell fuel blended with castor (almost all brands carry synt oil only), I usually blend my mixture from its core ingredients (nitro is also not an easy buy here)

SuperDave wrote:Can't say this would be relevant to Cox engine fuel but we run Castrol Semi-Senthetic engine oil in our Ford 4.2 V-6 and with good results.

Is the prejudice against senthetic lubricats based on factual documentation or traditional thinking?

SD

  It is based on experience.   Synthetic offers superior lubrication over the temperature range it is designed for.  Water cooled engines, or even air-cooled engines with high pressure lubrication systems (so cooled oil is constantly being supplied to bearing surfices) will do great on synthetic.    

When you exceed some critical temperature (varies with exact oil, and I don't know exactly what any of them are anyway) synthetic either evaporates (smoke) or breaks down into things that are not good lubricants.  You go from great protection to no protection.  Once lubrication is lost, the bearing heats up more, and damage is rapid and severe.   One lean run on a Fox .35 running synthetic will ruin it.

Castor does not flash-off (smoke) or break down under extreme heat like synthetic or even petroleum based oils do.  Instead it does the opposite of breaking down.  The castor oil molecules actually start joining up (polymerization) which thickens the oil, keeping it in the bearing.  Under extreme heat the polymerization goes to extremes and forms a varnish. If this happens in a cox cylinder, it hurts performance if the varnish gets too thick, but performance returns after the varnish is mechanically removed with steel wool or scotch bright.

Cox engines are rather peculiar in lacking a wrist pin.  The required motion is done with a ball and socket joint, and the socket part of that bearing is the piston.  Very few other engines do this.  The piston gets very hot, and it will cook out any oil other than castor.

In addition to serving as a pivot, a wrist pin in more conventional also slows the heat flow from the piston to the upper rod bearing.  I once modified a moped engine to move the wrist pin bushing from the rod to the piston skirt, (dual bushings) to get more bearing area, and also to allow the oiling holes to be on the bottom where the flywheels could sling oil at them.   The experiment failed because (I think)  putting the bearing in that location makes it run much hotter than forcing the heat to come in through the wrist pin.  The solution to blowing out those moped rod bushings turned out to be running castor oil instead of the "better" synthetic.

Castor is sort of magic in this regard.  A chemist could probably concoct a synthetic molecule that would do this, but refining castor beans is cheaper.  Oh, and it smells like victory.

Lapped iron/steel engines benefit from baked on varnish that castor forms.  It makes for a wear layer.  Synthetic lubricants remove that varnish.  50/50 seems a good balance of varnish building and varnish removal.  On old lapped iron engines cleaning the varnish might make the engine so loose that it has no compression.

Phil

Take a look at this fuel it looks very good I was going to try it but already purchased the sig 25% champion fuel witch works great by the way.

1 qt 25% NITRO HYPERFUEL FOR 1/2A .049 .020 .010 25% PURE CASTOR OIL


http://www.ebay.com/itm/1-qt-25-NITRO-HYPERFUEL-FOR-1-2A-049-020-010-25-PURE-CASTOR-OIL-/251261786156?pt=US_Radio_Control_Control_Line&hash=item3a805e982c

pkrankow wrote:Lapped iron/steel engines benefit from baked on varnish that castor forms.  It makes for a wear layer.  Synthetic lubricants remove that varnish.  50/50 seems a good balance of varnish building and varnish removal.  On old lapped iron engines cleaning the varnish might make the engine so loose that it has no compression.

Phil

So would it be a good Idea to run any normal RC car 20 or 25 % nitro fuel once in a while through the cox motors to clean up all the varnish built up in them?
Not saying run a full tank maybe run like one min through them or 30 seconds or something to clean them out?

Yeah I saw that the other day.  Not bad,perhaps a bit more oil than needed. I would try it except shipping will be twice the purchase price. 

Ron

Excellent explanation, Kevbo, and Phil too for tacking on an additional good comment.
Reptile, I don't think running a Cox on car fuel even once would be a good idea. It may clean out some varnish, but you don't want to clean any of it out of the ball socket. As Phil said, a 50/50 mix maintains a good balance to keep the cylinder varnished while not allowing it to build up to an excess. If you want to devarnish a Cox engine, just remove the cylinder and use some 0000 steel wool wrapped around a dowel and wet with solvent. And go easy so as not to take too much off or you may end up with no compression. And wash it thoroughly before re-installing.

reptile wrote:

pkrankow wrote:Lapped iron/steel engines benefit from baked on varnish that castor forms.  It makes for a wear layer.  Synthetic lubricants remove that varnish.  50/50 seems a good balance of varnish building and varnish removal.  On old lapped iron engines cleaning the varnish might make the engine so loose that it has no compression.

Phil

So would it be a good Idea to run any normal RC car 20 or 25 % nitro fuel once in a while through the cox motors to clean up all the varnish built up in them?
Not saying run a full tank maybe run like one min through them or 30 seconds or something to clean them out?

Cox engines are designed with castor oil in mind.  They are lapped steel piston and cylinder. 

Engines can also be cleaned easily.  The outside can be cleaned with a toothbrush and a splash of fuel to remove quite a lot of varnish.  If done regularly the outside will look nice for a long time.  The inside can be cleaned with a bore brush, brass or nylon, when necessary, which is when RPM is sagging after the engine heats up.  Castor varnish is sticky when hot.

When the engine is running properly it will not build up excess internal varnish very quickly.

Phil

reptile wrote:Take a look at this fuel it looks very good I was going to try it but already purchased the sig 25% champion fuel witch works great by the way.

1 qt 25% NITRO HYPERFUEL FOR 1/2A .049 .020 .010 25% PURE CASTOR OIL


http://www.ebay.com/itm/1-qt-25-NITRO-HYPERFUEL-FOR-1-2A-049-020-010-25-PURE-CASTOR-OIL-/251261786156?pt=US_Radio_Control_Control_Line&hash=item3a805e982c

It looks good, but to me, it's mystery fuel. No idea about the mixing methods or component quality or control. With shipping it's more than Sig. Since the loss of Mike McGraw's Glowplugboy fuel, I've come to terms with the idea that 50/50 is what we need for our 25% sport fuel. Reputable dealers like Rich's Brew and Powermaster have pure castor in the 15% and below variety too. And their QC is well known and proven.

Pretty good write up on fuel, he seems to like syn, castor mix.

http://stunthanger.com/smf/index.php?topic=457.0

That's a good article. I just read it the other day and copied the text and saved it. I've saved a few of Randy's write ups.

Just clarify a couple of things:-
1. Degummed castor oil is the ONLY way to go imo.
2. Methanol is widely used in many high performance motor sports.
3. Nitromethane is widely used in drag racing.
Even where I am (in the unfashionable western end of a spiral arm of ...) there are a number of places supplying these ingredients.

As a complete aside, we used to have a restaurant called "Milliways" in Perth.

Okay, for us ding-dongs out here, that have measuring cups, could you convert the recipe to ounce-like volumes, so we (ME) have a better idea of how to mix, for ourselves?

It would make it just a little easier to get started.

Thanks so much!

To make a quart of 20% castor, 25% nitro
                  20% castor= 6.4 oz
                  25% nitro  = 8   oz
                  55% meth  =17.6 oz
                                    32 oz

I think Glowplugboy made 18% castor, 25% nitro
                  18% castor  5.76  oz
                   25% nitro   8      oz
                   57% meth  18.24 oz

GUS THE I.A. wrote:Okay, for us ding-dongs out here, that have measuring cups, could you convert the recipe to ounce-like volumes, so we (ME) have a better idea of how to mix, for ourselves?

It would make it just a little easier to get started.

Thanks so much!

Get yourself a metric measure and make life easy for yourself. For a litre of fuel 8% = 80ml, 12% = 120ml and so on. Even for difficult numbers:- 5.56% = 55.6ml, 12½% = 125ml. How can you go wrong? Join the developed world.

dinsdale wrote:Get yourself a metric measure and make life easy for yourself.  For a litre of fuel 8% = 80ml, 12% = 120ml and so on.  Even for difficult numbers:- 5.56% = 55.6ml, 12½% = 125ml.  How can you go wrong?  Join the developed world.

Absofreakinlutely!
I cannot fathom the stupid that drove the rejection of converting to the metric system back when it was up for discussion in the '70s. What... because we'll have to buy a whole 'nother tool set? Well, guess what! It's one of the things I love to grumble about. When I'm working on small things I always use metric dimensions unless it'll throw something off too badly. We're stuck with 8ths, 16ths, 32nds, 64ths... and to add insult, miles. Why is a mile not 5000 feet? A foot not 10 inches? We screw our own system up with inconsistencies like that, and so forth and so on...... [/rant]