Author Topic: Fox Stunt 35 Fuel and adding Castor (Read 2267 times)

uglystick40 · « **on:** April 23, 2019, 08:46:13 AM »

Hello everyone, I am new to the Forum, I wanted to ask a question. I apologise if it is one of those questions that have been beat to death. I have two fox 35 stunt engines, one of which I got for my 13 birthday even, the other is the anniversary engine. I am trying to do the right thing and run enough oil. I have taken a gallon of 15% omega removed 12oz of fuel and added 12oz of castor (byron lube booster) If I understand correctly I end up with 13.5% nitro, 26% oil, and 60% methanol. 25-29% oil. I also read that fuel is measured by volume not weight. So I end up with a gallon containing, 17.4oz nitro, 32.88oz oil, and 77.7oz Methanol. I think it should work...I am missing something...Is there a trick to mixing it? I cannot keep the engines running on it. they die within a minute of removing the glow plug. I have tried os#8, miracle, type-F, MC-59, and MC55. Ihave had no luck. If I run straight 15% omega without oil, the engines run perfect. I don't undersatand, Please help. Thx in advance!!

Tom Vieira · « **Reply #1 on:** April 23, 2019, 10:25:10 AM »

attached is the mix I use, they seem to like it. i also use Klotz BeNol for my castor. the base fuel is Wildcat Premium Xtra 10%.

i split it in half amongst two jugs, and add half the oil called for to each one, so 13oz and a splash in each jug.

Dennis Toth · « **Reply #2 on:** April 23, 2019, 11:06:07 AM »

Stick,
Your blend is at the upper end of what the Fox likes to run on. What prop are you running? The Fox will turn a 10x6 quite well if the tank uniflow vent is mounted pointed into the free air stream. To get them to run reliably with the stock Fox NVA you need to make sure the two holes are positioned across the venturi when looking down just out of sight (the holes are drilled off center so when positioned they will be just out of view). Add a short piece of fuel tube between the ratchet wheel and the spraybar boss to seal the threads against the boss. Don't try to run it to slow a fast 4 cycle to a rich 2 works well. Once you get it working look up the stick in the bypass mod for profile mounted engines to get a more reliable run. Don't mount it on hard aluminum pads as the Fox has a mold draft angle to them that needs to crush into normal maple mounts. If you have the hard mounts add a 1/32"plywood pad between the engine and the mount to act as the crush pad and this will prevent the engine from binding when you tighten it down.

Best, DennisT

uglystick40 · « **Reply #3 on:** April 23, 2019, 11:24:23 AM »

I have the motor on ringmaster, I am running a 10x4 APC prop. I have a 3.5oz Brodak uniflo tank, I have been plugging the overflow port. The brass tube that faces the propeller I have been leaving open. I have the original NVA I also have a piece of fuel line on the needle valve, I do this in my other RC engines as well. I have been running the motor rich horizontal (4-cycle) and having it mostly clean out with the propeller facing up, I figured this is in the ballpark. Ironically, It will run for a minute or so in the air, the die. I would get a loop or two, then die. I have ordered some Brodak 10% 29% Caster fuel to try, maybe it will help...I know its bad, It runs perfect on 15% Omega...I know, Im bad....I was gettting frustrated...

Dave Hull · « **Reply #4 on:** April 23, 2019, 01:47:27 PM »

'Stick Four-Oh,

Your numbers are a little off, and your original post may have mislead some about your running too much oil, but that would not seem to be the root of your problem.

Per your remove and replace recipe, you have:

Nitro: 13.6%
Oil: 24.8% (56.5% castor, 43.5% synthetic)
Methanol: 61.6%

Everyone's opinions vary on the "right" mix for a Fox, but personally, I would prefer more castor and less synthetic in the mix. Further, running approximately 25% oil is not too much, and nowhere near the "upper end" of what a Fox will tolerate. Anything above 30% is probably just a waste of oil and will make it harder to keep the plug lit. As you are not close to that, your problem would not be from running too much oil.

There is no "trick" to mixing fuel. Any sequence works. But just like making cake, candy and pie, you want to measure accurately for best results.

The real questions are:
1. How fresh were your ingredients? Was the "good Omega" that runs fine of the same vintage as you used for your new mix? If so, then...

2. How confident are you regarding your measuring technique? What did you use to decant exactly 12 oz.?

3. Are you trying to run the engine too hard? A 10x4 APC may let it spin up and the Fox doesn't really like that so much. Hard on the crank, and harder to keep cool, and thus more oil likely needed. The Motorman had some good points, there.

4. Are these engines actually broken in? If not, then as they heat up they can bog down and flame out.

5. Are these engines varnished up on the piston and liner? If so, you may get the same result. They heat up, bog down and flame out. These are not abrupt stops. More like a painful, multi-lap death. Note that running all-synthetic fuel will tend to strip off the castor varnish, free up the engine, and get you all ready to damage the P/L fits if you overheat the engine on the next run....

6. You have changed plugs, so I'll rule out that line of thinking.

7. Do you have a tank problem? Will the plane run out a whole tank on the ground with the inboard wingtip up?

Divot McSlow

Dennis Toth · « **Reply #5 on:** April 23, 2019, 03:56:39 PM »

Stick,
Dave is right the oil around 25% is OK for the Fox. If it is running OK on the ground then cutting in the air it is likely not a fuel mix problem. Two things on Ringmasters, make sure the tank is mounted so that the back is kicked out at least 1/8" and that the fuel line pickup is above the first fin (about 1/8" above the center of the plug). The Foxes like the tank offset. The second thing is to mount the uniflow vent up above the fuse in the free airflow stream. Many profile uniflow tanks have the vent coming out the top of the tank out on the outside end, this puts the vent in a turbulent airflow area and the pressure at the uniflow inlet is all over the place. I had this on my Ringmaster and went nuts trying to get a consistent run. I put the pictured vent on and I can now set it anywhere I like and it holds.

One last point, you mentioned that you are running a 10x4 prop. The Fox 35 doesn't have the rpm range to handle that prop. A 10x6 wood or a 9x6APC is more in it's wheel house.

Best, DennisT

Dan McEntee · « **Reply #6 on:** April 23, 2019, 04:48:03 PM »

Quote from: uglystick40 on April 23, 2019, 11:24:23 AM

I have the motor on ringmaster, I am running a 10x4 APC prop. I have a 3.5oz Brodak uniflo tank, I have been plugging the overflow port. The brass tube that faces the propeller I have been leaving open. I have the original NVA I also have a piece of fuel line on the needle valve, I do this in my other RC engines as well. I have been running the motor rich horizontal (4-cycle) and having it mostly clean out with the propeller facing up, I figured this is in the ballpark. Ironically, It will run for a minute or so in the air, the die. I would get a loop or two, then die. I have ordered some Brodak 10% 29% Caster fuel to try, maybe it will help...I know its bad, It runs perfect on 15% Omega...I know, Im bad....I was gettting frustrated...

OK, you say it runs perfect on 15% Omega. Does it run the tank out? Does it change any from beginning to end? If so, then your tank should be in the ball park. The issue would be with your fuel. Omega is like, 18% total oil out of the bottle, I believe. It may be the castor that you added is not comparable with the stuff in the Omega. The 10-4 prop shouldn't be a deal killer either as long as the model isn't too heavy. I have run 10-4 and 10-5 props on Fox .35s quite a bit when it suited the airplane. The Brodak fuel should help eliminate some questions about fuel, just be ready for a different needle setting. If you added too much oil to the original fuel, you cut down the amount of alcohol needed to fun and you are now "gas lean." If you cut the nitro content, then you have to turn the needle in more to get the RPM you need, thus leaning it even more. If you don't have enough "fuel " in your fuel, it could flame out very easily. Remember, it takes the alcohol to make the reaction. The fact it runs acceptably on straight Omega is the give away to me.
Type at you later,
Dan McEntee

uglystick40 · « **Reply #7 on:** April 23, 2019, 07:29:16 PM »

Wow! Great information everyone! Thank you so much for helping me. So to answer some questions. running on the 15% Nitro 18% oil omega I get 3.5ish minutes of run time. It seems to do this fairly consistently. I have put 5 or so flights on it with the Omega, it is the same every time. I have kept it pretty rich, The head is not black...LOL!! So, the anniversary edition motor I have mostly been fighting with is pretty new, It may have a gallon through it. I will put a 10x6 on it for now on...As far as fuel age goes, I just purchased 4 cases of fuel last week "club buy" I am using on of these gallons..I used a graduated syringe to draw out the fuel...I will plan on tilting out the back corner of the tank, the tank I have on it is a little long , I will have to change it, I have already ordered one...I see where you put the uniflo vent. I will solder up one and put it on! I wanted to mention, I have a muffler on it, I am not running tank pressure, I have drilled out the stinger to .312, this seemed fairly common size to drill them out to..Sorry if the information is a little discombobulated!!

Dave Hull · « **Reply #8 on:** April 23, 2019, 09:04:27 PM »

'Stick Four-Oh,

According to the Morgan fuels data, their Omega is 17% oil. And of that oil, only 30% of it is castor. That is a great way to ruin an old-school iron piston/steel liner quickly. Have you looked at the exhaust oil after one of those runs? Was it gray, dark brown, or a little bit sparkly?

There should be no reason the ~~Morgan~~ Byron Lube Booster (all castor) would be incompatible with their fuel. (Edit: My error pointed out below by Dan.)

If the engine has not been running steady, I would also be looking at fuel contamination. Crud from a tank, whether new or old. Fox fuel with a lot of castor in it would be less able to flow in a partially plugged needle valve than the straight Omega. Do you filter what is coming out of the jug? Out of the tank? Did you backflush the needle? In any event, the needle setting for the two fuel mixes will definitely be different.

If you used a syringe to do your measuring, you can hardly go wrong, unless the phone rings and you forget how many you pulled out already....

On Foxes I have run, I found they can be sensitive to the backpressure of a muffler. One in particular gave me trouble: a new 35 Stunt with the factory muffler. After taking off the muffler and breaking it in thoroughly, it was better. After ditching the stock muffler and using a well-drilled tongue muffler it became a sweetheart motor. If you opened up the factory muffler to .312" it should help, but I would point out that the header on a stock muffler is quite restrictive. The extra backpressure makes it more prone to overheating.

Don't be fooled by a lack of a blackened head thinking that you have not "cooked" your engine. The mostly synthetic fuel may not carbon up like the all-castor fuel would. There are lots of well used Foxes out there with a black crust that are fine---and probably some new-looking engines with a faint tan stain that have a P/L fit that has gone away. Check your exhaust oil routinely to see if you are "making metal."

Based on your last post, a completely new question set arises: how did you get a gallon of fuel thru it if it is giving you problems? Did you ever have it running well? Was that in a plane or on the bench? What fuel mix were you using at that time? And, if you thought things were going well, when did it change? When you put it on a plane? When you changed fuel? When you installed a muffler? When you put the plane in the air?

Good luck with your engine!

Divot McSlow

Dan McEntee · « **Reply #9 on:** April 23, 2019, 09:12:20 PM »

Quote from: uglystick40 on April 23, 2019, 07:29:16 PM

Wow! Great information everyone! Thank you so much for helping me. So to answer some questions. running on the 15% Nitro 18% oil omega I get 3.5ish minutes of run time. It seems to do this fairly consistently. I have put 5 or so flights on it with the Omega, it is the same every time. I have kept it pretty rich, The head is not black...LOL!! So, the anniversary edition motor I have mostly been fighting with is pretty new, It may have a gallon through it. I will put a 10x6 on it for now on...As far as fuel age goes, I just purchased 4 cases of fuel last week "club buy" I am using on of these gallons..I used a graduated syringe to draw out the fuel...I will plan on tilting out the back corner of the tank, the tank I have on it is a little long , I will have to change it, I have already ordered one...I see where you put the uniflo vent. I will solder up one and put it on! I wanted to mention, I have a muffler on it, I am not running tank pressure, I have drilled out the stinger to .312, this seemed fairly common size to drill them out to..Sorry if the information is a little discombobulated!!

OK, now we are getting somewhere. 3.5 minutes on 15% nitro is in the ball park, if you are indeed using it all. At this point, don't over do the running of straight Omega. If you can wait for the Brodaks to come, do that and see how that runs for you in both engines. If the first engine is well broken in, you probably haven't done any damage yet. If the second anniversary engine needs more time, use the Brodaks fuel for that also while you figure your ratios out. If all runs well on the Brodaks fuel, and your run time goes up with the lower nitro, I think you can look harder at something wrong with the first doctored gallon of fuel. Also at this point, make only one change at a time, so you can keep track of what works and what doesn't. It will be worth the methodical way to figure this out.
Type at you later,
Dan McEntee

Dan McEntee · « **Reply #10 on:** April 23, 2019, 09:15:44 PM »

Quote from: Dave Hull on April 23, 2019, 09:04:27 PM

'Stick Four-Oh,

There should be no reason the Morgan Lube Booster (all castor) would be incompatible with their fuel.

Divot McSlow

Hi Dave;
Just to point out, he said it was Byrons Lube Booster, different brand. Might still be a significant element of the problem.

Type at you later,
Dan McEntee

Bill Adair · « **Reply #11 on:** April 23, 2019, 09:20:29 PM »

If you have run a gallon of Omega fuel through that Fox 35, I'm afraid that you may have ruined the engine already!

Morgan fuel may have changed since I first used it, but I doubt that very much. I even called Morgan years ago and asked what their oil content was. They lied to me, and said it was 20 percent! I had already evaporated samples of my Omega fuel, and estimated the oil content at just over 12 percent!

They should print a very noticeable sign on their containers stating "Warning! Do not use this fuel in any plain bearing iron piston engines!" Morgan fuel is formulated for ball bearing engines only!

They don't call Morgan fuel "Cool Aid fuel" for nothing.

In their defense, many brands of current fuel have way too little Castor for early plain bearing engines, and in particular R/C car fuel of any kind.

You should set that Omega fuel aside for cleaning parts, and order fuel from one of the fuel sources that blend to order. I used to order all mine from SIG, but am out of touch (age) with current sources. Others here can recommend good fuel sources for you. I think you can order most in quarts, to avoid haz-mat fees.

A new Fox engine should be run-in on fuel with 28 percent Castor oil, and after a careful break-in, will probably run fine on 25 percent Castor, or a blend with at least half Castor lube. Fox engines were never designed to use synthetic oil, as the manufacturing tolerances were typical for the day (all over the place!).

Bill

Dave Hull · « **Reply #12 on:** April 23, 2019, 09:51:16 PM »

Dan,

Good catch on my casual mistake about the two different brands. Typing too fast = mental error. I know they come from different manufacturers because I looked them both up to see what the ingredients were claimed to be before I did the percentage calculations. So my thought remains this: the Lube Booster is supposed to be straight castor. I know of no reason it would not be compatible with any "low nitro" fuels.

I have no special knowledge about the actual oil content of Morgan fuels. I have not done a boil-down test like Bill references.

I've run a Fox hard on 10/20 All Castor for Fox racing. You can't overprop and you really can't afford to miss the needle setting. And it's a given that some engines will never work well, and some will work well for a few races. If you find one that works well race after race, and beats you year after year, look at it closely--my money says it isn't stock inside.

Divot McSlow

Bill Adair · « **Reply #13 on:** April 24, 2019, 01:29:07 AM »

"I have no special knowledge about the actual oil content of Morgan fuels. I have not done a boil-down test like Bill references."

Hi Dave,

Don't know if you read a much earlier post of mine, where I mentioned the reason for the tests?

At that time I was club secretary, and news letter editor, as well as part time instructor pilot at our R/C club. After having too many new flyers show up at the field with plain bearing iron piston engines (like K&B Sportsters), and Morgan Cool Power or Omega fuel for R/C flying lessons, I decided to spread the word about the fuel problem that was frying many of their engines on the maiden flight. If new flyers showed up when I was training I had an easy solution, I provided free fuel for them to use until they could get their own.

So I ran a series of tests by begging for samples of various fuel in the news letter, and catching anyone I could at the field opening a new container of fuel that I did not already have. The fuel I was able to test samples of was Omega, Fox, SIG, Byrons, Red Max, and several other popular fuels available at that time (almost twenty years ago).

I had quite a variety of fuels offered for testing, and all of them except Morgan had the ingredients marked on the container labels.

Test was run by measuring the same sample size (10cc as I recall) with a graduated syringe, and injecting those into three separate cups in the muffin tin. Four types of fuel could be sampled per tin, and I marked each row of three with a pen, so I would knew which fuel they contained. The pan was set on a shelf in my well ventilated garage, but covered by the shelves above to minimize any fallout . No one parked in the garage, and there were no sources of spark or flame to worry about.

I found that the volatile components evaporated in three or four days in warm weather, so the residual could be collected by tilting the pan up on one end for another day or so, and then sucking the remaining oil back into the syringe from the corner of the cups. Of the dozen or more fuels I tested, I found that every fuel marked with the ingredients on the jug was exactly as indicated, but the Morgan fuel (Omega) measured just under 13 percent oil.

Not a scientific test by any means, but every sample measured spot on except the Morgan fuel! I even made sure that all three samples of Morgan fuel measured exactly the same, and they did.

The test results were published in our news letter, and I got nothing but praise from club members at the next meeting. Our club membership was about a hundred members at that time, and our meeting attendance was so good that we often filled the grade school classroom where we held our meetings.

Anyway, my newsletter archives were lost many computer failures back, and I've yet to find the backup so I'm going by memory here.

Now I'm embarrassed to say that my local hobby shop stocks nothing but Morgan fuel (in gallons), and a few small cans of the new Cox half-A fuel (that they finally got right after many complaints from us Cox fans). They also don't stock glow or diesel engines, and haven't had a new half-A prop on the shelf in many years!

Stopped in a few days ago to get a new gel cell for my flight box, and the shelf was bare. The clerk told me they can't get them anymore since Tower and Great Plains went under. Checked Amazon and found dozens of 12 volt gel cells, and many of them for under $20, so the home and business alarm systems saved our bacon.

Bill

uglystick40 · « **Reply #14 on:** April 24, 2019, 04:28:31 AM »

Wow, Bill! That is scary! I have been running cool power or Omega for a very long time now! I go through 2-4 cases a year, and have for 15yrs. It veries depending on how much electric or gas I am flying at a given time..LOL!! I have primary access to Byron, Morgan or VP at the local hobby shops. May be I need to run a different brand after your finding...Grr...Most of my Nitro engines are Bearing, OS, thundertiger, supertigre or saito. I have a few FP/LA, but I have more SX, AX, FX...etc...I am wondering if I need to take my 25FP/LA 40FP/LA engines and run them, I have quite a few...I am starting to think I am not smart enough to run a fox 35...LOL!! (sorry bad joke)...I will have Brodak fuel by the weekend, I will try it. I have 6 different time period 35's, not all on planes, picked them up at swap meets over the years, might try one of them and see the difference...my other engines do not have muffler lugs, I like mufflers!! Muffler may be the problem...idk I think I will try the motor without it as well...

Dennis Toth · « **Reply #15 on:** April 24, 2019, 06:13:54 AM »

Stick,
If the Fox has a good compression seal it should be fine. I have run them on lots of different fuels (including Morgan) and as long as they don't lock up they will survive. Best to use the Brodak they you have coming. The Fox isn't hard to get to run good but the tips mentioned in these thread make it pretty easy, they sound harder then they are. Key with the Fox is not to go flat out lean. I like to see a little smoke trail coming out in level flight, this shows it has enough oil to keep it cool.

Best, DennisT

Bill Adair · « **Reply #16 on:** April 24, 2019, 10:46:59 AM »

Sorry for the confusion, but I've been talking about newer engine break-in here. All your other engines with ABN (OS) and ABC technology are fine on 20 percent oil. It's only the plain bearing iron piston engines such as Fox, K&B, McCoy Red Heads, and similar 1950 technology that have the problem, and adding Castor oil to fuel with 20 percent lube will work for break-in. Some of the better brands of early engines, and even the smaller displacement Fox engines, will run fine on less then 25 percent lube, but I'm not sure why?

The fuel calculator previously mentioned will tell you how much oil to ad, to get up to the correct percentage.

http://www.nitrorc.com/fuelws/

You probably should use no more than 10 percent Nitro to start with, as Fox 35 stunt engines are best run on 5 to 10 percent Nitro anyway. Starting with 20 percent oil shows adding 8 ozs of pure Castor per gallon, will get you to 25 percent.

Dennis is correct! Lower oil content than 25-28 percent may work fine, but only if the engine has already been run-in. The key is to always run rich when new, and hope it never goes lean during a flight. Problem is you never know when that may happen, and it can ruin those old engines.

All the Byron fuel I tested was 20 percent oil to start, so check the label and go from there.

None of my business, but why don't you use a first name here? Your among friends, but if you wish to be called Uglystick40 that will have to do.

Bill

BillP · « **Reply #17 on:** April 24, 2019, 11:00:32 AM »

Starts and runs long enough to get airborne and then quits...consistantly the same run? Sounds like fuel delivery to me as the fuel level drops. Several yrs back I had a problem with a Brodak uniflow and at least two guys I fly with have recently had problems with Brodak tanks. Mine was fixed by changing the uniflow position. The others just had leaks at the seam. I would try a different tank you know works.

uglystick40 · « **Reply #18 on:** April 25, 2019, 11:41:39 AM »

My fuel arrived today, I plan to see what happens after work..I have a Hayes 2 or 3oz tank, If it is still acting strange I would hook one up and see what happens with it! Ill report back. Thanks everyone!

uglystick40 · « **Reply #19 on:** May 02, 2019, 12:40:41 PM »

I have spent some time running Brodak 10% 29% Castor fuel through the 35 with a 10x6 Propeller. I have not has any issue, it just runs. I can adjust the needle rich and have it lean (ish) out when I point the nose up. It ran perfect never died or acted wierd. Thanks for all the advise. I wish I know why my fuel concotion doesn't work, but at least I know the solution. I also learned that 70' foot lines are a bit long for a ringmaster. I like it alot better on my 60' lines. wing overs and horizontal figure 8's get a bit loose on 70's...Thx again all!!

Dave Hull · « **Reply #20 on:** May 02, 2019, 08:38:12 PM »

Stick Four-Oh,

Glad you are now having successful runs with your Fox. That's what really matters.

In the thread above, there were several comments that your previous setup and operation could have been contributing to the problem, not just the fuel. Switching everything at once to a known happy place for a Fox was a good move, but it doesn't prove that either of the fuel ingedients or your mix ratio was your sole problem. Running too little castor (even at 25% total oil) in a relatively new/tight Fox will cause the engine to overheat and die. Running too little pitch and compensating by running too high an rpm may cause the engine to heat up and die. Doing all of this together....well.

Enjoy your new FoxMaster setup!

Divot

PS--If you want to drive Fox-oholics nuts, show up with a plastic jug of fuel that is made with Klotz Benol. Now Benol is pretty much 100% castor, but all Klotz oil has a dye in it that a true-blue Fox-oholic will associate with a synthetic oil. The oil is red, so the fuel turns out red or pink. A real Fox-oholic will only trust a fuel with an amber color, as one would expect from a mix using 29% Baker's caster oil, as purchased from SIG. Known good stuff for Foxes. If you can stand all the "advice" telling you to immediately stop using the wrong fuel, when you get to the bottom of that gallon and they begin to believe you about the Klotz Benol, you should switch strategies. Now I haven't tried this one yet. (I am still recovering from all the "advice" on my Klotz oil....) But I'd then mix up a batch of 29% caster using the Bakers or just buy a jug of SIG Fox fuel, and put a few drops of green dye in it. That should turn it into a bright green mix that looks a lot like a famous, all-synthetic R/C "coolaid" fuel. Stand back for another round of soulful counseling. While you watch their confusion as your Fox just chugs reliably down to the bottom of that gallon of fuel, too. Pure Netzeband pranking. Good for the soul. But not good around pacemakers or other medical devices. Caution is advised.

Dennis Toth · « **Reply #21 on:** May 03, 2019, 04:43:38 PM »

Stick,
Glade to hear you have a working Fox 35 system. Now that you have a base line you might want to try a tank of the original brew just to see and confirm that the doctored fuel was the problem. I use a mix of 50% Brodak 10%N, 29% castor and 50% Brodak 10%N, 23% Syn plus 1oz/gal of Randy's Aero-1, this has worked well for me.

Best, DennisT

Author Topic: Fox Stunt 35 Fuel and adding Castor (Read 2267 times)

Tom Vieira