BrightGarden

I'm starting this thread after the topic of Cox Super Power Fuel being harmful, or not, came up in another thread and took on a minor life of its own.
Background - returning to the hobby/addiction after more than 25 years, I innocently thought I would build a small fleet of curious and sometimes historical .010 to .15 planes.
I had a few Cox engines sitting by from many years ago - among them a Tee Dee 051 from the early eighties with at most an hour of run-time.
Also, I saw a few engines on eBay and other sites I bought.
Along with that, I found out how expensive fuel had become and (innocently) ordered 4 quarts of Cox Super Power Fuel CSPF while I was at it, through Tower.
It cost about $50 with shipping and hazardous material surcharge.
The case had just shown up when I started reading snippits here and there on the major RC forums that there is a big question about the modern mixture for CSPF.
This thread is the culmination of a few things I have become aware of along the way.

The simple issue is that if you read Cox engine literature, you void the warranty if you run a fuel that has less than 10% castor oil with a total of 20% lubricant in the mixture. Like 10% castor oil and 10% synthetic for a total of 20% lubricant.
The current Cox formulation has 1.8% castor oil and 16.2% synthetic - total of 18% lubricant.
(See attached image of current Estes-Cox/Hobbico CSPF formula web page, below.)

This formulation would apparently void the Cox warranty, if there were actually one around these days.
(See old Cox literature about this, attached below.)
Using the current formulation for CSPF is going against requirements for the engine. Apparently.

The single weak point with using too low of castor oil concentration in the fuel is that the fairly unique design feature of virtually all Cox engines use a ball and socket connection point between the conrod and the piston, instead of a hinge and a wrist-pin.

So far, I have found accounts in online RC forums of the current CSPF formulation a) being as good as it ever was or that b) engines die within three tankfuls of the fuel.

In one technical thread, it was responsibly stated that it depends on what synthetic lubricant(s) is(are) used. I will find that info and either reference it or reproduce it here in this thread.

To get some first-hand knowledge, I figured I could just get two new Cox 049 engines and run one with the CSPF and the other with Sig Champion 25%, with appropriate break-in on each engine using the corresponding fuel. Would the CSPF engine die a dramatic death?

I am standing by now for an eBay order of two Cox Surestart 049's to arrive this week, I hope.
As I mentioned, I already have almost one gallon of Cox fuel (in quart bottles), and I ordered the Sig fuel so it should arrive soon, too.

I have a temperature gauge and a tach on hand to take some readings along the way.
At this time, that is about the extent of my intended setup.
I am not an expert on engines, just a sport flyer at the moment, but willing to learn as much as possible along the way.

A number of experts and/or voices of experience have chimed in already and I have gotten a little knowledgeable about what makes a responsible test.

• I also ordered a piston/connecting rod reset tool to do a prelim reset on both engines
• There was an account of lapping compound being left in the ball and socket after manufacture and delivery to the store shelf - I will disassemble each engine and clean them, looking for said lapping compound.

For the most part, we may not be able to expect any more Cox-design engines will ever be manufactured - we're living on existing stock.
That is why it seems incomprehensible we would use an inadequate formulation in the engines when that would end-of-life them, depleting whatever reserves we have.

In my learning process so far, I have not seen any response from the manufacturer of the fuel, which is muddled through distribution through Hobbico.
Anyone with those connections could help by chiming in.
The most responsible thing at this point is to get an authoratative response from Estes-Cox/Hobbico letting us know how the fuel is formulated.
I would think there would be experts here that could decipher that for us - the good and the bad.

Well, I'll let you know when the setup is ready after the engines and Sig fuel arrive.

Cheers - Poughkeepsie Pete

Pond Skipper

Ref: full thread
http://www.rcgroups.com/forums/showthread.php?t=1325147


Cox oil testing findings
[HR][/HR]Good Morning,
About 2 years ago I started doing an investigation on the lubrication requirements for the Cox type engines using the "ball and socket" piston joint and steel piston/cylinder. This investigation was aimed at "sport" flyers using nitromethane contents 15% and below using un-modified reed valve engines. Two types of tests were run, one was a long term endurance test of 10 hours running at ideal mixture settings, turning a standard cox 6-3 "black" prop. The other test was a fligh simulation test where the engine was run on a small fuel supply that allowed a start, initial slightly rich run, lean out, and stop that would take approximately 6 minutes per cycle, again on the same propeller as the 10 hour endurance. The total time for the flight cycle testing was also 10 hours, or 100 cycles. All engines were broken in using standard procedures on their respective test fuels. The results were very interesting, and not what I originally expected. The base fuel used was 15% nitromethane, 20% castor oil by volume. The base fuel engine failed 8 hours into the 10 hour endurance test by wearing the connecting rod through the crown of the piston. The wearing surfaces of the ball and socket were not "varnished". The same test run with a synthetic oil in place of the castor ran for the full 10 hours without failure although the rod and piston joint showed .008" of wear. The flight cycle testing engine failed on the castor mix at 4.4 hours by the same piston failure, the rod had just broken the surface of the piston crown and affected starting, although the engine would still start via an electric starter. Again no "varnishing" was present in the joint. The synthetic oil engine passed the 100 flight cycles, but showed slightly more cylinder wear near the exhaust ports and a similiar .008" of wear in the ball/socket joint. So from the first basic tests it was clear that the ball/socket joint does not run hot enough with 15% nitro fuel to cause castor oil to polymerize, "varnish" and prevent metal to metal contact, which is of course castor's key strength as its anti-wear capability in liquid form is lower than other oils. The synthetics while better in the liquid form at anti-wear, do not have the capability to protect hot areas such as the cylinder near the exhaust port as well as the castor. A third test was run with 15% nitromethane fuel, 2% castor oil and 18% synthetic. The engines passed both the 10 hour endurance and 10 hours of flight cycle and both showed about .008" of wear in the ball/socket joint. Slight varnishing around the exhaust ports showed the castor was doing its job protecting that specific area, otherwise the engines were spotless inside. In a final effort to reduce the ball/socket wear an oil made up of 8% castor, 90% synthetic oil, and 2% tricresyl phosphate was used at the same 20% as previously with 15% nitromethane. The engines using this fuel passed both tests, with just under .002" ball/socket wear, slight varnishing around the exhaust ports, and overall excellent condition. This test was repeated with 16% oil volume with no degredation in wear and a 6% increase in RPM. To go back to determining the failure mode of the all castor fuel 30% nitro fuel was blended with 20% castor oil. The engine though needing to be de-varnished every 2 hours passed the 10 hours of testing without a ball/socket failure. The crankpin and crankcase wear was however higher than any other test. I did a final test using 20% of my synthetic/castor/TCP mix and 30% nitromethane, the engines ran the full 10 hours without needing a de-varnish, and the ball/socket and crankpin joint were in excellent condition. So from my little bit of testing, I have concluded that for my Cox design sport engines, a fuel mixture with castor/synthetic oil/and TCP will provide excellent service with as low as 16% total oil volume however I did not test the 30% nitromethane fuel at that oil level. This eliminates the gumming of engines in storage, sticking reeds etc.


Authors Additional information as the discussion progressed:
To clarify, no a reset was not done, I have made the tooling and have done so in the past but felt it was not part of this testing. I should also note that the wear in the ball/socket joint was not deformation from "pounding", it was strictly metal to metal contact, microwelding, and tearing of the piston material. If you put tension on the piston and rod assembly, no measurable change had taken place, so I feel fairly comfortable that there were little to no reversal loads with the 6x3 prop. Again I chose this as a "sport" flyers type cycle, not racing. All that being said, I personally feel a "reset" would have not changed the outcome as I see no way it would reduce the loading and wear on the upper surface of the ball and socket. In fact it might have restricted oil to the joint, which I believe is a weak point in the design to start.

The first cox engines DID have a real wristpin, and connecting rod. I have made pistons for a couple of mine along with aluminum connecting rods. Had to find a use for that box of old worn out cylinders that was taking up space. Anyway from what I found, on 15% or less fuel on a typical stock reed engine, it seems as if the piston and rod run just cool enough to prevent the varnishing. Now unfortunately its not easy to measure the temperature of that joint, so I dont know how close I was to the temperature needed to varnish the castor. Might be just a little, might be a lot. I think as a matter of course, it seems that the level of castor in the oil, could follow the nitro content and be a good "rule of thumb". I.E. 5% nitro=5% castor(95% synthetic) or 20% nitro = 20% castor (80% synthetic) etc. I think this would give engines that run cooler, a better lube package for their application and running conditions, and engines that run hotter a better lube package for them. Seems funny though that an oil that protects the best at extreme heat, underperforms at lower temperatures. I personally dont think I would ever go 100$ synthetic unless the engine cooled very well, which many of the AAC types do, just not the little steel wonders.


Wear was measured by compressing the piston and rod in a jig to ensure everything was straight and measuring the distance from the top of the piston to the bottom of the rod. This was to measure pure wear, not "slop". Sig castor was used as it seems to be a fairly universal "standard".

I had a sample of the oils run through our materials lab to verify the material, the "Sig" castor is just castor, no EP, no metals, no polys, no esters, just bean oil. The synthetic oil chosen was Morgan Cool Power "blue" 2 cycle oil, which is the heavier of the 2 they sell and is comparable to the straight castor. The Cool Power oil was checked, and it was found to be a very common ester type with a proven EP additive from the industrial world. It would not be ethical for me to tell what it is though. I doubt the "looseness" had any influence on the wear, there was no evidence of any load reversal on the joint and the "extended length" of the piston/rod never changed. So the "crimp" never loosened, it just wore into the piston crown. Usually on a 2 stroke any load reversal is either a misfire, or running without a high enough load, so underpropping could cause it.

Nope not a fuel supplier. I work in engineering designing engines for a living, and not models. If you have read carefully through what I have written, you will note that I did say that the castor varnish ( real simple terms castor loses a water molecule and crosslinks forming the varnish that protects the bearing surfaces ) is one of the best for preventing wear. However....without a high enough temperature to cause the change, castor in its non-drying form does not have the anti wear capability of some others. So while being the best for high termperature areas, it may not be the best for lower temperature bearing areas of the engine. Not black magic, simple tribology. Nobody is asking you to change what you do, im just sharing what I have learned from a controlled test ( as controlled as it can be ). If someone wants to share similiar test results I would love to talk about it. Unfortunately much of the information that floats around in public channels is just empirical, and many conclusions are drawn and expanded to cover things not relevant to the original failure.



I have found many "claims" in the hobby lubrication world. In reality most of the "synthetics" are industrial lubricants from either Dow chemical , Chevron, or Shell Oil. The EP additives are mostly OTS additves like Vanlube 972 or others. My background is full size engine design and I work at probably the last big 2 stroke company in the US. Model engines are a hobby of mine, I have built a few, modified a bunch and crashed my share. One thing I have learned is that there is no ONE answer for everything, and that every design has its own needs, and those needs change with application. I was a "castor only" guy for a long time, until I decided to try some other lubricants. Every lubricant has its strong and weak points, and having the right balance can make something superb for a specific engine design. I have a test mule PAW .049RC that has over a gallon of fuel through it, being a 95/5 Synthetic/castor blend and 20% total oil volume. Someday I may pull it down for inspection, but it is just as snappy as when new, and I have never had a "stuck" engine in spring. I enjoy the freedom of blending my own fuels and actually knowing what my engines are feeding on.


The test I ran at 30% nitro with the same oil "varnished" and carboned up as I would expect. Most of my 1/2A models are draggy, high wing area designs that require a lot of blade area to perform. The 6x3 has been the standard cox prop for about 50 years I think. A smaller prop would deffinately reduce the loads at the joint, but would be unsuitable for a lot of models.

So my final thoughts on this are pretty much as follows:
1-The surestarts are inferrior to older product in the ball/socket area and require different lubricants if larger (6x3 or 7x3) props are used with low nitro fuels.
2-Castor only outperforms other common lubricants if the bearing surface runs hot enough to "varnish" it ( common knowledge in the tribology world ).
3-It does not take much castor percentage to protect the upper cylinder area on a reed valve cox (5% by volume) if low nitro fuel is used.

I am going to keep my model flying on my synthetic/castor/TCP fuel for a year and see how it survives in the "field". No after run oils are ever used.

Typically 375-400F, or about the temperature that PAG oils start to decompose. So in effect at the temperature that the PAG synthetics "give up" , the castor takes over to protect the parts. Unfortunately below this temperature the PAG's have better "lubricity". So when people talk about an oils ability to lubricate, they must be careful about what temperature they are talking about. As a note, the engine I was running on 100% PAG synthetic oil had nearly the same ammount of oil carryover (unburned oil) as the castor tests. And the engines themselves rarely got over 300F CHT. About the only area in the engine that seemed to run over 400F was the upper 2mm of the cylinder wall. An aluminum cylinder, or more heavily finned steel cylinder would probably drop this temperature.

Swinging a larger prop, I believe re-sets are a mute point. No signs of load reversal ( meaning no pulling on the crimp ), tells me that the crimp is literally along for the ride. Actually having a little load reversal would be good for preventing the failure I am seeing, as it would unload the top side of the ball and allow lubricantup into that joint. As it is now, if you swing a larger prop there is not much of a path for lubricant. I limited the castor as it was not really the better lubricant for the particular situation. Castor is great lubricant at high temperatures, but its not the greatest at lower temperatures. So since the ball and socket are running so cold ( probably under 300f ) the castor couldnt do as well at other oils...simple as that. I used the castor in the mix to protect the upper part of the cylinder. We will fly this for a year and see how it fares. Typically I burn about a half gallon of fuel in a year.


Anyway hope this is entertaining for people!

BrightGarden

Thanks Pond Skipper - that is the best info I have seen to date on the subject, and the source I mentioned in the original post - maybe you were the one that sent that to me, originally, it's sort of hard to keep track right now.
Summary
(My first reaction: "Whoa, 10 hours!" Where can I go off-grid to run two whining engines and not draw attention? Even 4.4 hours to a failure is significant.)
Surprising to me the 15 Nitro - 20 Castor mixture failed after 8 hours - no varnishing of the ball and socket. More wear + extra drag forces from cool castor?
Surprising - using all-synthetic had no failure ( had measurable ball joint wear). Key question I am learning to ask is "What synthetic???" This seems to be the crux of the mystery, now.
Now less surprising - flight testing with all castor - dead at 4.4. hours. No varnishing. Death due to wear + high viscosity of Castor at running temp? Nitro related.
Now even less surprising - flight test with all synth - "just" cylinder wear and ball joint wear.
makoman's reasoning: too cool running temp with 15% nitro. Aha - nitro content seems to have influenced results. Castor too cool, but synth nice and cool to do its work, not breaking down. Castor wouldn't varnish at 15% nitro. Nitro is the other variable, then.

When mako went to 30% that throws me off. More nitro means cooler temp, but he happened upon a good lube mixture with optimum results. TCP is new to me - mako is an in-industry guy.

So the conclusion is, "Mako, can you make me some fuel, please?"
Aah,kidding.
Part of the actual conclusion at this point is that there are even more masterful, custom blends for optimal performance - just not commercially available. Probably, because of cost reasons.
It matters to wear and failure rates what synth is used. That came up in the full mako thread.

Cheers, Peter
PS - I found contact info tonight for Estes-Cox and will ask them about the formulation, let them know we are performing an experiment. See if they respond.

Pond Skipper

Hi Peter glad to see there is now a official thread. Mako's info needed to be at the forefront prior to proceeding with new additional testing.
He didnt record humidity and ambient temps during testing and engine loads beyond just the prop but rather the mass of the plane used / type and flying speeds when unloaded as examples.

BrightGarden

Thanks for posting that, Pond Skipper and extracting other important parts of the mako - or should I say Dr. Mako - thread.
He defines what TCP is but I had to look up EP - Extreme Pressure (additive), it seems. Learning.
My equipment isn't lab-grade - more like cheap hobbyist grade - but the basics of taking an Off The Shelf OTS engine with OTS fuel and seeing what happens should have some value. Trying to avoid anything that invalidates the test. Maybe I'll run more than one engine through, seems worth it to get at real-world results.
Surestart engines sound the most vulnerable to the oil issue, so the results might amplify the effect the fuel would have on more tightly controlled manufactured engines like a Tee Dee.
Cheers -
PS Engine Update - not sure if the engines shipped, my seller on eBay is away for the week, it seems.

Pond Skipper

He should have reset the ball socket but didnt have the reset tool.

We should all check the ball socket fit after engine break in and reset as needed to avoid additional wear. Reset as needed after a learned amount of runs by inspecting every so often. By doing so we reduce complete failing of a component initiated by allowing a loose ball joint to inflict wear to the piston, rod and crank pin.

Mr Cox

I'm a bit ambivalent regarding the socket issue and its resetting...

Logically I can't see what difference it would make in a running engine, as there should never be any tension in the conrod when the engine runs (at regular rpm). I have reset a few during the last few years (but didn't have any reset tool before that). I can't say that I have seen much, if any, difference in the running, but there is a slight difference when turning them over or trying to start them. Perhaps I simply haven't used high enough rpms...

The fuel test is very interesting, but perhaps hard to do in a scientifically sound way. There are many variables to try to keep track of, I doubt two surestarts are made the same when it comes to the cylinder/piston fit and the deck height etc. Then there is always the needle setting variable, should one try to lean out fully or run similar rpm or similar head temp, etc.

Looking forward to the test results though, the performance of two standard fuels in a standard application would give much more than the previous test and result of some unobtainable synthetic magic potion...

Pond Skipper

I have reset tools for the .010 , .020, .049, .074 and 09. I have used them all over the years. The loose socket allows the cylinder to advance further up the cylinder and in time can bang up against the glow plug. The loose socket adds additional heat to the top of the piston head and causes the crank pin to waller the rods fit to the pin. Additional vibration is induced as well adding more heat. The rod can stretch and snap in half if left to run in this state.Note the picture of his failed piston is related to not resetting the ball socket after hours of restrained bench running adds a lot of additional stress to the engine components.

Mr Cox

That would be rpm dependent though, and I haven't seen that happening at regular rpms. After resetting a piston the engine runs much the same, to me.

Pond Skipper

Yes has to get pretty loose for a ring to appear on the top of the piston.

BrightGarden

Update: Since I am waiting on shipment of engines and Sig fuel, I called the Hobbico/Estes-Cox customer support number this morning.
This is the page that the CSPF page leads you to, and I talked to "Chris."
I knew he wasn't a policy maker, but I was pretty direct that there is some information that says the CSPF harms Cox engines.

He directed me to submit an email to [email protected] - the third Hobbico entity involved.

Here is a copy of what I submitted.


[email protected]

To:
Hobbico
Estes-Cox
Cox Models Product Support
3002 N. Apollo Drive, Suite #1
Champaign IL 61822

Greetings,

I am someone returning to the Radio Control "RC" hobby after 25 years away. Recently, I pulled out some of my Cox engines I used when I was in my teens, and ordered 4 quarts of Cox Super Power Fuel “CSPF” from Tower Hobbies at the cost of around $50. This high price included the significant hazardous materials surcharge.

Very soon after I received the fuel I discovered a volume of information in online RC forums that discredits this product because of the lubricant blend that is stated on your website. This stated formulation is 25% nitro, with 18% total lubricants, of which 10% is castor oil. That is a total of 1.8% castor, 16.2% synthetic.

Original Cox engine literature states clearly that using less than 10% total castor oil voids the warranty.

The result of burning fuel with too little castor oil is the destruction of the ball-and-socket joint of the connecting rod and the piston. This joint requires the accumulation of varnish from castor oil, and synthetic lubricants don’t produce this result. The ball joint disintegrates without the varnish. Some accounts in online RC forums claim that this happens within a few tankful’s of inappropriate fuel.

I spoke with Chris on your customer support line this a.m. about your company helping the RC community with more information to address growing opinion that the product destroys engines. As a next step, he directed me to submit this email in order to get further with the issue within the Hobbico organization.

It is imperative on a number of levels that your company address the need for more complete specification of the synthetic component of the fuel.

1. It is the responsible thing to do. Your company should be encouraging growth of the hobby and supporting the customer. Right now a growing number of vocal members in online RC communities are frustrated with never getting an adequate answer from your company, and getting resentful that a responsible reaction has not been offered from you.
2. Cox engines are the gateway engine for so many hobby entrants. They are the most vulnerable with the least knowledge of the hobby. To have their first experience end in a burned out engine can send them away from any involvement in the hobby forever.
3. Cox engines are no longer being manufactured. The RC community won’t risk existing engines on CSPF without knowing the fuel is appropriate.
4. Most of the market wants to buy your fuel, revealing information is not going to hurts sales.
5. As was my reaction, enthusiasts will a) buy the Sig or other product, or b) mix fuel themselves. I feel I was “stuck” with $50 of possibly inadequate fuel - I won't risk using it on irreplaceable engines.

The responsible reaction would be to explain what the formulation of the product is. This is not going to hurt your sales, this is going to improve them. There is wide opinion in the community that CSP Fuel can’t be trusted.

I am not taking the word of RC community members’ accounts at face value. I have done a call-out online in the communities for the best information to come forth, including actual accounts of damage and destruction of engines. There are already numerous authoritative discussions on the subject rom people with far greater knowledge and capabilities.

Also, as I publicized with the online RC community, I am running my own experiment with the CSPF I have on-hand. I have two new engines on order to demonstrate the appropriateness of CSPF by indefinitely running properly broken engines in on both Sig fuel and the CSPF. From information others have shared on test results from general fuel testing, ten hours of operation usually reveals any inadequacies.

Your response with detailed information will be appreciated. I believe disclosing what synthetic lubricants are used in the Cox Super Power Fuel is to your own advantage, and will let the community decide the appropriateness for Cox engines.

Attached is a scan of the relevant part of original Cox literature stating the warranty invalidation if less than 10% total castor is used.

Sincerely,
Peter
Poughkeepsie NY

SnApRoLl-

Hi Pete, thanks for posting this thread.
I'm,curious to see if you get a Truthful answer from Hobbico or just a generic Run-Around "Thank you for contacting us, your concerns will be addressed" response.

Also, I'm not sure if this is true or not, but I have been told by a couple different Hobby Shops that CSPF is made by O'Donnell fuels.

Shawn.

BrightGarden

Hey Shawn,
When I spoke to Chris in phone support for whatever part of Hobbico the call goes to, of course he doesn't have the formulation at his fingertips nor is he a policy maker at Hobbico. I kept it pretty low key with him but let him know there was a concerned group out here that would just as soon buy the CSPF from Hobbico as get fuel from anywhere, else - it wasn't as though we were trying to steal the formula. I wonder how big a seller the CSPF is, anyway. It might just be that it is so low on the priority list that the feedback never gets noticed. I do feel strongly that it is the gateway fuel for people entering or re-entering the hobby. Like me, they will go online and buy the product that has Cox in its name. If the fuel does destroy engines, it would turn most people off from finding out why or pursuing flying model airplanes any further.

Let's see what, if anything, I hear back from them.
I wonder if finding the Hobbico/Estes-Cox people at an RC show like WRAMs or other flying event will help to get an answer.

BrightGarden

Just found this in my gmail - attached as a screen shot. Also, a screen shot of Hobbico's LinkedIn entry.

Cheers,
Peter

Cox International

My Feedback: (10)

I did receive a call today from a product manager at Hobbico and we had a good chat re. fuel. I will send him a link to this and other relevant posts.

Cheers
Bernie
www.coxinternational.ca

aspeed

Cool, now the gods are watching over us.

SnApRoLl-

Any chance that you will offer a true COX blend fuel?

Shawn

SnApRoLl-

Here is some good news regarding the CSPF. Looks like Hobbico is stepping up to the plate.
http://www.coxengineforum.com/t7143-...per-power-fuel Read the first post.

JohnAV8R

BrightGarden, thanks for the info. Lots of work and testing. An excellent write up.
I've used Cox TD .09's (7x4 MAS) for years and haven't run them overly hard.
I've always added a little castor to whatever fuel I was using and haven't really had any problems with the engines.

John

Boomerang1

TCP is the particularly nasty additive in aviation turbine oil that flyers of model turbines are trying to avoid by trying different
lubricants.

http://en.wikipedia.org/wiki/Tricresyl_phosphate

It's a neurotoxin & it's effects are cumulative. Worth remembering is that, as an additive in turbine oil, it's not designed to be burnt,
just circulated round & round in the engine. It's nasty when absorbed by skin contact, worse when ingested via the lungs. - John.