Question re fuel

I have heard that you can use R/C synthetic fuel in a Fox 35 if you mix a pint of castor oil into the fuel. Is this true? I am having trouble finding all castor fuel locally in Miami Fl, for mi foxes.

>I have heard that you can use R/C synthetic fuel in a Fox 35
>if you mix a pint of castor oil into the fuel. Is this true?
>I am having trouble finding all castor fuel locally in Miami
>Fl, for my foxes.

That would bring the total oil content from about 17% (on some fuels) up to about 26% (or 23% if you started with 14% oil), but the majority would still be synthetic. 26% is about the minimum oil content you would want to use with the Fox, but I get a little squeemish in using anything but all castor. If you started with some SIG 50-50 (20% oil) and bumpted it up with additional castor, it wouldn't be as bad.

Just remember, these engines need oil and they need castor. You will find very few people (and then only with a special engine) running less than 50% castor in any stunt application, so doing so with a Fox 35 could be very risky if you want the engine to last.

LAST EDITED ON Oct-12-03 AT 09:06 PM (CDT)
 
Try the local motorcycle shops that sell dirt bikes or water craft,ask for Klotz Beanall it is a degummed caster oil that I have been usind for about ten years in steel piston/liner engines mixed at 29% for Fox 35,Super Tigre 35-46's and down to 20% for Cox .049's.I think that what Leonard said about 50% oil was in a 50%-50% mix of the 29% total oil content. I have found if the engine was broken with all caster fuel and you run a caster/synthetic fuel it will clean off the build up on the piston and liner and lose compression.

Start with Sig 20% oil, 50-50, pour out 8 ounces (use in a smaller engine, maybe), and add 8 ounces of castor. This will bring the mix to 25%, majority castor. I have been using this for years in a variety of Fox Stunts with no problems.

Another option is to go to the Fox web site www.foxmanufacturing.com and order the superfuel by the case.

Doug Taffinder used to make an excellent stunt fuel called PAC which had 23% castor with 1-2% lubricin that worked well in the fox.

Just a few words on fuel for a Fox, I've done over a 300 hundred hours on bench and in flight testing with different fuels. I’ve torn engines down and inspected them for heat and wear. Number 1 cause of engine failure is overheating, I’ve also reworked over 1100 Fox 35’s since 1985.

Synthetic oil is a great lubricant but does not cool like castor, castor is a great coolant but does not lubricate as well as synthetic. Synthetic is also a very good cleaner.

If you do this make sure you start with 15% nitro since adding 15 oz of castor will reduce your nitro content to 13.4%. I have, with success used 15% nitro and 18% oil and added 15oz of castor. I’ve used Byron’s as my back-up fuel; this leaves you with 17.9oz of synthetic and 22.7 oz of castor.

Here are my recommendations for Fox .35’s

FUEL: NO LESS THEN 28% OIL AND 10% NITRO.
15% nitro works best but uses more fuel. The engine runs cooler and produces more power on 15% nitro. (DO NOT USE 5% NITRO it overworks the motor and over heats it).
Oil should be at least 25% Castor and no more than 3% Synthetic. 28% all Castor well never fail you. Remember that most manufactures use at least 2% synthetic as a cleaner. You should use only pure methanol, Baker AA castor and pure synthetic. Hundreds of hours have been devoted to researching fuel blends,
Good fuel and proper oil content is the single most important thing you well do to insure good engine runs and long engine life.
WHY so much Castor oil: The Fox .35 is very thinned skinned and needs large amounts of oil to cool it.
Most all repairs are done because the engine has been overheated, 99% of all crankshaft breakage and, front bushing failure is due to less then 26% oil used or less than 10% nitro
To sum up fuel if you run a cheep fuel you well never be happy with your motor.

LARRY,

I have serveral modern ABC engines,.well, i have 4 really:

1- OS.35 VF

2- OS.32F

3 - Magnum (Randy Smith reworked) Gp .40

4- CB .46 stunt (made in Brazil, same or more powre as a ST.51)

I NEVER use anythibng with less than 50% castor.

If I hadn't beem strict about this my OS.32F would be history, one hot summer day I got a lean,mean run on it, and got out of ut unharmed.

Had I ben using all syth, forget it!

God bless you!

In Christ,

Ion:
Let me stress that I said I have used the 18% oil and 15% nitro with 15oz of castor added with success, I in no way recommend it. Remember that I also run 1oz of Aero 1 in my fuel too. I always run 1/2 and 1/2 mixtures in all my other motors. I always try to run 15% nitro and 28% castor in my Fox 35's but like everyone else in the world sometimes I can't get it. This has been my backup fuel for several years now but I also take the chance of hurting a motor to when I do this.

See if your LHS carries SIG products. They should be able to get SIG Bakers AA castor oil. Or call SIG.

Thanks guys! Now I feel more confused...Dumb but Happy!
Fernando:+

Randy Powell tells me that Wildcat makes a Ducted Fan fuel formula that is 23% oil, and available in 15% nitro. The oil is a blend of castor and synthetic, but I can't say how that is split up, because I haven't been able to get any. But it does put you a leg up on getting to 25% or 29% oil content. Steve

A question for Larry Foster.
In your responses in thread #5 you said never use less then 10% nitro. While I agree with you and like 10%, you would think that Fox would have modified their Superfuel formula years ago if nitro would benefit their motor both in power and longevity.
That said I and probably a whole lot of other modellers have Fox 35's that have never seen anything else but Fox Superfuel.
I assume that any Fox 35 that is generally used in sport applications with it sticking out in the breeze is covered by this fuel, and only in a full stunt ship encowled and at weight would really need the additional nitro for the additional power and cooling.
Just need additional elaboration on the subject, not doubting your word.
Dennis

Dennis
The info I give is from years of testing and running Fox's, not only by myself but a lot of people that run them for me. 10% works good but I've yet to have anyone say that 15% didn't make it perform better. Also tear down on motors that have been abused on purpose shows less heat damage then those run on 10% and 5%. I took the same engine with three different P&L's and run a gallon of fuel threw each one in a screaming 2 cycle, then tore them down to see they effects. The difference in heat discoloration in the piston and sleeve was considerably less using 15% compared to 10% and 5%. The advice I give on fuel comes from many hours of flying and bench testing.

I’ve also found that the more experienced flyers demand more from their motors and the less experienced ones don’t seem to care if the motors are inconsistent. I’ve also had inexperienced flyers use a good reworked motor with good fuel and then realize that it’s much more fun to fly with a motor that gives peek performance.

I would not even attempt to explain why Fox does what they do. To quote what one of the guy’s told me from the factory “ why would you lap the piston and liner it’s just wearing it out before you run it”.

About ten years ago I built a motor for one of Foxes people and he commented that the motor had less vibration and higher peek RPM, then he sent my head back asking for a refund because he could use it in public.

>Dennis
>The info I give is from years of testing and running Fox's,
>not only by myself but a lot of people that run them for me.
>10% works good but I've yet to have anyone say that 15%
>didn't make it perform better. Also tear down on motors that
>have been abused on purpose shows less heat damage then
>those run on 10% and 5%. I took the same engine with three
>different P&L's and run a gallon of fuel threw each one in a
>screaming 2 cycle, then tore them down to see they effects.
>The difference in heat discoloration in the piston and
>sleeve was considerably less using 15% compared to 10% and
>5%. The advice I give on fuel comes from many hours of
>flying and bench testing. (snip)
>Larry

I don't believe that the above was a valid test, Larry. I will grant you that using 15% nitro fuel with the same oil content as 5% nitro fuel will generally result in a cooler run because we usually end up running more fuel through the engine. When we run more fuel through the engine, it is like increasing the oil content in your fuel. You can use 5% nitro with more oil and achieve the same results (cool running). But going to 29% oil is sufficient on these engines.

The Fox is a very low compression engine. It was purposely designed that way. It achieves its particular run characteristics because of this. Adding nitro actually changes those characteristics. You can achieve the same thing by lowering the head slightly. Nitro has less bang for the ounce, however, so we usually end up pouring more fuel through the engine when we add nitro. (And, as a consequence, more oil.) However, this may not be true if we run them overlean.

Fox 35 engines were not made to run in a screaming 2-cycle under any circumstances, much less for one hour. That is a good self-destruct test, I will grant. And these engines need oil. It is a good way to wear them out quickly. When you run them rich, they have "x" amount of oil going through them in a minute. When you run them lean, with the same fuel, they have a smaller amount of oil going through them--but more heat build up and more revolutions NEEDING more oil. It is a sure formula for destruction.

When you ran the engines with a lean 2-cycle, even using 29% oil was not enough. You are reducing the content per cycle to maybe half of what it normally sees, while running it twice as hard (where it needs more, actually). What helped the engine running 15% fuel was the fact that you would have to run it richer even in a dead lean two cycle. (Nitro has less bang for the ounce than the methanol it replaces, so you need to use more fuel for the same power output.) By running it richer, you are pouring more oil through the engine per revolution which helps the cooling and adds more protection (although still not enough.) Thus your destruction results were less destructive with 15% nitro fuel not because the nitro content allowed it to run cooler, but because you used more fuel and consequently oil to help cool it.

Run these engines the way they are supposed to be run with 5% nitro fuel 29% oil and 15% nitro fuel with 29% oil, and the engine will last just as long and be just as cool. You may get a little more "bang" with the 15% nitro, but you can achieve similar results by using the hemi head. And, with either fuel, if it goes overlean, it will self destruct.

Valid argument I agree if you have a better way of testing then I would be more than happy to try it out. I have torn down more Fox's then most people will see in a lifetime and everyone that was run on 5% showed heavy heat distortion. Again I have come to the conclusions threw years of working only with Fox 35s. I am very well aware of the Hemi-Head since I use a design that Randy Smith and I came up with.
I was very reluctant to post what I did since people have there own opinions and very little testing to go along with it. I acknowledge that you are very well tuned and experienced in engines and fuel so what you say always carries heavy weight with me.

It would take a lot to convince me that running 5% nitro is they way to go with a Fox .35 since everything I have ever done with them says 10 and 15% is better for the engine and the run you get with it.

Again I must stress that I recommend MINIMUM of 25% castor and a MAXIMUM of 3% synthetic. I have had success with other oils but I also fit all my motors, break them in properly, build light planes and know my systems work when I put them in the air. This is the reason I have given away over 20 motors for people to test and report back to me what they were doing and the results. Threw actual testing in the air and on the bench do I come up with modifications and recommendations. I have destroyed a lot of parts and motors going to the extreme with them.

This is a copy of the data sheet I send with my motors.

FOX 35 REWORKED BY LARRY FOSTER
FUEL: NO LESS THEN 28% OIL AND 10% NITRO.
* 15% nitro works best but uses more fuel. The engine runs cooler and produces more power on 15% nitro. (DO NOT USE 5% NITRO it overworks the motor and over heats it).
* Oil should be at least 25% Castor and no more than 3% Synthetic. 28% all Castor well never fail you. Remember that most manufactures use at least 2% synthetic as a cleaner. You should use only pure methanol, Baker AA castor and pure synthetic. Hundreds of hours have been devoted to researching fuel blends,
* GOOD FUEL AND PROPER OIL CONTENT IS THE SINGLE MOST IMPORTANT THING YOU WELL DO TO INSURE GOOD ENGINE RUNS AND LONG ENGINE LIFE.
* WHY so much Castor oil: The Fox .35 is very thinned skinned and needs large amounts of oil to cool it.
* Most all repairs are done because the engine has been overheated, 99% of all crankshaft breakage and, front bushing failure is due to less then 26% oil used or less than 10% nitro
* To sum up fuel if you run a cheep fuel you well never be happy with your motor.
* PISTON GROWTH: You well notice a scratching affect on the piston during break-in this is normal. Fox uses a very hard liner and a soft iron piston that grows as it is heated and cooled. This growth is paramount to good engine performance. A slow break-in procedure as described below must be followed.
* PROPELLERS: BY&O, APC, BOLLY, REV-UP. 10x6 OR 10x5.
* GLOW PLUGS: Thunder Tiger, RO Jet hot, Fox Miracle Plug, Any RC Long that is a hot heat range.
* PROP-EXTENISIONS: Propeller extensions well reduce the life of the front bushing and crankshaft.
* FUEL TANK: You well need at least 4.5 to 5.0 oz of fuel for an AMA pattern.
BREAKING-IN YOUR FOX .35 REWORKED BY: Larry Foster
This must be followed to validate your warranty. It is very important to ensure proper piston growth.
* Propeller: 9X6 and 10X6 (Do not use wood because you most likely break them).
* 2 Glow plugs
* New Motor Starting Hints: Install the needle valve until it bottoms out lightly, then back it out three turns .Choke the motor 2 or 3 times after fuel has reached the needle valve, prime the exhaust port. Flip the prop a couple of times. Start it by popping it backwards against compression
1. With a 9X6 propeller, fuel the engine with 2oz of fuel.
2. Set the engine in a very fast four cycle. Do not run it sloppy rich, this can damage the connecting rod and piston.
3. Let the engine cool down completely.
4. Repeat this until you have run 10oz of fuel threw it.
5. Install the 10X6 propeller, open the needle valve one turn, and fuel it with 4oz of fuel.
6. Set the needle valve to a very fast four cycle.
7. Let the engine cool down completely.
8. Repeat this until you have run 16oz of fuel threw it.
9. Install a new glow plug.

Remember to run your engine a little rich the first couple of flights or until you know how it well run in the air. It can take up to 20 flights before it is fully broke-in. The piston needs to heat cycle and grow. It is important you let it cool down completely between flights your first day out. It is not unusual to have to Change the needle during the first 10 to 20 flights as the motor breaks in.

Again, your comments on using 5% fuel are interesting, but I have a feeling the problems that were exhibited may be due to people trying to run the engines too lean in order to get the power out of them.
They look for more than what the engine was intended to give. If they lean the engine out, then it will not get the proper lubrication pure and simple. We run 10-6 BY&O or the old Rev-Up EW props on the Fox with 5%, set it for a deep 4-cycle in level flight with a break when you point the nose up. That way it "comes in" just as you begin the maneuver, but always runs 4-cycle in level flight.

George Aldrich always used to complain about nickel plating on the OS engines. He didn't like it, accused the engines of "peeling" and said he had seen something like 50 to 100 examples of these engines that had "peeled". He later admitted that only two of these were CL engines and the rest were RC use. Most of the RC guys use junk fuel, run their engines too screaming lean (lean them to peak rpm on the ground, and they will immediately go over lean in the air). With improper lubrication, yes, there was a problem. Put less oil in the fuel, lean it out (so less goes through the engine) and this is a formula for instant destruction.

Now, on the Fox, I have seen lots of people try to run these without having them set properly. Now I don't know what mods you are doing to your engine(s). You may be lowering the compression even more than stock (maybe not). But the lower the compression, the more nitro you will need for a given amount of power when you run the engine in a 4-cycle mode. Basically, the engine needs a given amount of oil. That holds true whether you use 5% nitro fuel or 20% nitro fuel. The more fuel that an engine uses (whether it burns it or spits it out the exhaust) the more oil will pass through it at a given rpm. But if you are using 29% oil content, all (or nearly all) of it castor as you recommend, then 5% nitro fuel with the needle set for the engine to run 4-cycle in level flight will give adequate lubrication. Run the same fuel in a constant 2-cycle mode, and it won't.

But I would be leery of even 15% nitro fuel run in a constant 2-cycle mode as well, even though more fuel would be burned and, thus, more oil used by the engine.

I had a Fox 40 engine that I was running with 5% nitro, 20% all castor fuel. On one flight the stock Fox muffler I was using blew apart (a weakness of these things) and the engine went screaming lean on a flight that lasted 15 minutes. Now a normal flight was about 6 1/2 minutes and this happened somewhere in the flight. But even figuring 6 1/2 against 15, the engine was not only running faster (more revolutions per minute) but was only consuming about 40% of the normal amount of fuel (and oil) during this time period. And, yes, when the engine finally quit, it was destroyed. It needed a new piston, cylinder, and rod. It wasn't the 5% nitro fuel that hurt it, however. It was the over lean running conditions. In effect, I had changed the oil content to less than 8% oil under extremely hot conditions for an extremely long (fifteen minutes under those conditions is long) time.

If 5% nitro is used properly in these engines, there shouldn't be a problem. Even with a Fox. I just can't see wasting money on high nitro when it is not needed. Of course, hot weather or higher altitude can also make a difference. And if these cause people to run the engine in a leaner condition to try to make up for the loss of power, well, that, too, could be the problem.

Again I agree with you, as I've stated before the Fox 35 needs lots of castor not only for lubrication but more importantly as a coolant. With 15% you’re less likely to run the motor leaner, it produces more power and cools better. I personally have no problem spending a couple of dollars extra per gallon to insure good engine life and performance. One other thing you need to look at is you know how to run the motors and set them properly every time and put the right props on them. I have to assume every motor I sell is to an inexperienced flier or someone with an over weight airplane. Though you won't find anyone here in Tucson running less than 10% and the majority run 15% because of the performance increase.

Here is a list of the reworks I do:

Case:
Bushing hole and venturi blended.
Mounting lugs trued.
Mill the back plate surface true to the crankshaft so the rod doesn’t walk back and forth on the crank pin.
Liner bore is fitted to liner
By/pass port filled in and reshaped. The volume of the intake port is reduced approximately 30 percent. The port is reshaped to increase volume with the flow path.

Liner and piston:
Intake port is tapered and rounded with as little metal removed as possible.
Sharp edges on intake and exhaust ports inside of liner are removed.
Piston is de-burred.
Piston and liner are hand fitted.

Rod: Oil holes drilled and polished

Crankshaft:
Crankshaft is reground to reduce vibration, Intake port windows is de-burred and blended. Counter weight is milled and filled with heavy metal. Crankshaft and case are fitted.

Now my question is: Is rework on a Fox necessary? I have 4 foxes. One is a 40 (standard)and three are 35. One old, with the head dark brown to black and black inside, possibly due to using the wrong fuel. The other three have never been used, which I bought about 12 years ago. However I did try to "break-in" the .40 about 10 years ago, again with the wrong fuel. How much damage have I done?
I want to take this opportunity to thank all the people who contribute their knowlege to this forum. I, for one, learned by trial and error as a kid and always used foxes because they were the cheapest. I am just beginning to learn now, thanks to you good people. I really like what Al Rabe is starting to do with his contruction photos, and would encourage other expert builders and flier to contribute their knowledge too. Fernando:+

I think the short answer to your rework question is no, especially on the 35's.

However having said that, it is vital that you do some work---break in is a vital aspect of the Fox.

If you look at what Larry has said regarding his recommendations for his reworked foxes, it is also true for stock foxes.

So what do you give up by not reworking? Maybe some smoothness, maybe the infamous fox burp on profile mounted planes, maybe a little power. I would say take one of your Foxes, get some all castor fuel (at least 25%), and break it in. There are some easy mod's (like stuffing the transfer port with a piece of wood or JB Weld which fixes the profile burp (according to Fox experts). I think we have threads on SSW which cover these type things.

My final reply on reworks. My engines have won the OTS at the Nats on several occasions, VSC in Classic and OTS Several Times. A stock Fox produces 33.6 in oz of Torque at .334 HP, my reworks produce 42.4 in oz of Torque at .444 HP.

I am not the only one who can do this; Lew Woolard and Randy Smith produce a great Fox .35. I would stack mine or Lew’s or Randy’s up against a Stock Fox and show you a much better motor.

My best to all
Larry

Larry,
I don't argue that your rework isn't superior to the stock (I have one!), but just that it isn't absolutely necessary to rework a Fox to have a functional engine.

Sorry for any misunderstanding.

Thanks Alan, I do agree with you on that. A properly broke in Fox is a good running motor.

FYI-Break them in slow and they give good runs. Slow doesn't mean sloppy rich, Heat cycle them with a few ounces at a time in a very fast four cycle. Running them too rich can damage the piston and rod.

>My final reply on reworks. My engines have won the OTS at
>the Nats on several occasions, VSC in Classic and OTS
>Several Times. A stock Fox produces 33.6 in oz of Torque at
>.334 HP, my reworks produce 42.4 in oz of Torque at .444 HP.
>
>
>My best to all
>Larry

I can vouch for this. I have used Larry's Fox's in my Cobra that I have used at VSC. It is clearly stronger than a stock Fox, and it was able to survive running on 20% nitro with no problems to the piston or liner. It was running a very fast 4-cycle in level flight and as soon as the nose went up, it broke into 2-cycle. I was very happy with the motor, and when I show up again with a new Cobra (painted just like Steve's) it will probably have 25% in it's tank.

For a sport flier, 5% probably works OK, but they tend to run them overlean. If running 10 or 15 helps them, then why not. My guess is that even if they ran 15%, they would still run them overlean and cook them anyway. Len and Larry, you two can duke this issue out, but I sure like the way they run on 20%!!!

Haven't really tested 20%, so I'll play with it in the near future. Thanks for the kind words Paul.

In either the Argus or Cobra article, Steve said that he used a Fox .29 with extra head gaskets and 25% nitro.

I thought it best to stay out of this, but if PW can weigh in...

Having been beaten up in Classic by a local fellow who uses Larry's engines, I agree that they are quite nice in every way. Enough so that I am seriously considering buying one this winter for a favorite Classic model, my Oriental.

As to fuel, I have been using 20% and 25% (25% castor in both cases) mixes lately in my Fox 35s, although it needs to be noted they are ABC setups, the parts sourced in Russia, not Arkansas.

The really good news is that in 2003 I went a whole season of practice and contest flying without breaking a crankshaft in either of the two Fox 35s, one used in OTS, the other in Classic. I am not certain that beginning this season with prepping two cranks and carrying them to each and every practice session and contest had an effect. But in the past when I only had one ready-to-use crank in the toolbox I'd lose two or three shafts per year.

A recent contest: (Speed, as it were) "Fuel will be supplied by the C.D. 10 percent Nitro." Wasn't an entrant, was a Pitman; was skeptical of lubricants decided upon.

I don't understand the connection to my post.

Walter:+