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Author Topic: Fuel for Fox 35  (Read 1424 times)

Offline John Watson

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Fuel for Fox 35
« on: July 05, 2019, 08:53:48 AM »
Fired up an old Fox 35 with a muffler. It will run for a minute then quit. It heats up. I need to get some high content castor ? What about % nitro? A proper mix? these are questions I have. Thanks

Offline John Watson

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Re: Fuel for Fox 35
« Reply #1 on: July 05, 2019, 08:58:15 AM »
I saw Brodak has 29% castor with 5% or 10%...………..

Offline Brett Buck

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Re: Fuel for Fox 35
« Reply #2 on: July 05, 2019, 08:59:47 AM »
I saw Brodak has 29% castor with 5% or 10%...………..

  Either should work, presuming that the engine is not already damaged. 10% runs a bit cooler in actual use, since you can run it richer for a given amount of power. I would not assume that the engine is properly broken in, either, so unless you know the history completely, assume that it is not.

    Brett

Offline John Watson

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Re: Fuel for Fox 35
« Reply #3 on: July 05, 2019, 02:44:25 PM »
Is it still available?...………

Offline Brett Buck

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Re: Fuel for Fox 35
« Reply #4 on: July 05, 2019, 03:35:18 PM »
Is it still available?...………

  No, but any 29% castor fuel will be similar. Adding oil to a Fox is almost as good as adding nitro.

    Brett

Online Dan McEntee

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Re: Fuel for Fox 35
« Reply #5 on: July 05, 2019, 07:04:36 PM »
Fired up an old Fox 35 with a muffler. It will run for a minute then quit. It heats up. I need to get some high content castor ? What about % nitro? A proper mix? these are questions I have. Thanks

     It has not been established what fuel you are using? You may be able to add oil to what you have. It's it's got castor in it already, you should be able to add oil. What fuel are you using?

    Type at you later,
  Dan McEntee
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Offline John Watson

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Re: Fuel for Fox 35
« Reply #6 on: July 06, 2019, 03:00:57 PM »
All I have is some synthetic RC fuel but I just ordered some Brodak 29% 5% they were out of 10%...…………..

Online Dan McEntee

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Re: Fuel for Fox 35
« Reply #7 on: July 06, 2019, 10:36:29 PM »
   Well, that should do the trick for you. That's all Fox Super Fuel was, 29% all castor and 5 % nitro.  More nitro does help them run a bit cooler as Brett mentioned, and if you are at a higher elevation and can get it, 15% nitro. If you can get the nitro, alcohol, and castor, it's the easiest to mix yourself, especially in small quantities like quarts or a gallon at a time.
   When you run the fox on the new fuel, it may take a few tank fulls to build up castor varnish on the piston again. If you have it on a test stand, leave the muffler off for a few runs also. Treat it like you are breaking the engine in for the first time. If you do not know the history of the engine, that may be exactly what needs doing! You would be surprised how many of these 'old" engines are actually more or less brand new and need breaking in.
  Type at you later,
    Dan McEntee
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Offline GERALD WIMMER

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Re: Fuel for Fox 35
« Reply #8 on: July 07, 2019, 05:47:24 AM »
Hello Not all Fox 35's are the same with some much tighter then others depending on not just the quality of build but what era they were made (Shinny case ones were the tightest?). Sometimes I grow impatient with new motors and swap them out for a used/run in engine to get consistent flights.
Regards Gerald

Offline RandySmith

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Re: Fuel for Fox 35
« Reply #9 on: July 07, 2019, 12:41:45 PM »
Fired up an old Fox 35 with a muffler. It will run for a minute then quit. It heats up. I need to get some high content castor ? What about % nitro? A proper mix? these are questions I have. Thanks

John
I still have my Fox 35s from the 1970s, I used 28% oil with 1/2 synthetic and  half castor, today I use the same with 1 ounce Aero-1 fuel supplement, they  are  still in great shape. NOT worn out even with many hundreds of flights, and  not burned black with castor burned onto everything, That fuel mix really made them run great and last a long time, The  Except below explains why, it is cut from my fuel article pinned at the  top of this  forum
I will also tell you that you should try to use slightly more nitro in the fOX 35 than it needs because of the reason given in this thread, BUT be  very careful  with 15% nitro, it will  break FOX crankshafts, also wood props are what you want if your using  high nitro, Heavy plastic props  aid in shooting  cranks out of the front of the engines !

FROM THE FUEL ARTICLE

" Years ago, most fuels had only one oil ,castor.  This is still a very good oil with many good but some bad points.  Some of its good points; it carries heat out of the motor and gives a good plating action on all surfaces, especially when they’re hot. It also has tendencies to move toward hot surfaces, helping to protect them.  A few of its bad points; it burns and sticks to the piston sides and the ring groove and all other parts that are hot enough, and will carbonize the chamber. It will stick rings in their grooves, freeze wrist pins and build up ridges on sleeves.  This causes excess friction and heat and will ruin your motor in time.

The alternative to castor is synthetic oil and almost all fuels have these in them; the vast majority has all synthetic.  Virtually all fuel manufactures use one type of synthetic; these are normally polyalkylene glycol based oils.  They are mostly made up of alcohol started linear polymers , of oxypropylene groups.  These are made by several companies and are available in a large range of molecular weights and viscosities.

This group of oils is the modern version of the old Ucon oils and also have good and bad points.  Some of the goods points; they are very good lubes without containing any wax; they have outstanding load carrying capacity, film strength, anti-wear properties, are resistant to sludge formation, and will help keep your engine clean.  The bad points are they give no rust protection by themselves, they don’t plate hot surfaces as well as castor and they burn at high heats.

As you can see, both oils have advantages and disadvantages to them; it’s for these reasons that they work much better blending together than they could ever work alone.  Throughout many years of flying ,testing and other research have proven this to me beyond any doubt; plus you can see this for yourself.  Recently, a friend of mine had a motor that would go into the pattern and lean out and act very inconsistently.  The only change that was made was to substitute one tank of my fuel in the model.  The results were drastically different; the motor now ran very smoothly, going into a two cycle instantly when the nose was raised and back into a four cycle instantly when the plane was leveled.  This was tried back and forth both fuels; his and mine.  The results were  the same every time. I see this type of thing happen much too often, and it is extremely frustrating for Flyers to deal with. They often blame these fuel problems on cooling, cowlings, motors ,fuel filters, and unfortunately some don’t have a clue how to recognize or  solve this problem. This is  a frustration that you can live  without!

I would like to tell you there is one Stunt fuel formula to run in all motors, I said I would like to tell you that…unfortunately this is not the case, and will never be as long as we have such a wide range of motors and running styles.  What I will tell you is a good formula for the most common types of engines.  Make sure you pick a fuel supplier who will give you consistent fuel day to day ,and will blend fuel for your motor needs or has fuel to match your needs.  Stay away from any supplier who will not tell you the oil percentage, or who say one type works for all motors. I see this  much to  often also, It is unfortunate, but a lot of fuel manufactures will try to fool you about the oil and nitro percentage. One trick is to measure  by weight and not volume. Doing so, they can claim that the fuel is  for example 18 % oil , when in reality it is only 14.9 % oil content. Using weight  for ingredient , they can put in a  lot less oil and nitro . Other things are changing oil types, going to cheaper Nitro’s, and adding in other types of Nitro parrafins.

   So what percentage do you try? For motors like Fox .35s, OS Max 35s or the old McCoy’s and K&B’s, use a fuel with 26 to 28% oil content; preferably half castor and half synthetic, up to 75% castor  is OK. These  motors have very small bearing surfaces, and are subject to much wear and heat, most are all plain bushing motors and most have unbushed rods. They need a lot of  oil  to help cool the engines. Since these motors run hot, they need  extra oil to keep them lubed,clean, and to carry out heat . If you have one of these that is  in very good  shape but, is  just starting to get some brown or black varnish plating on it, the synthetic mix will clean it  up for you, resulting in increased life.  Do not use the synthetic  blend in an old motor that has a lot of time on it with all castor fuels; the synthetic will remove the castor varnish off the piston and sleeve and will in some cases, leave you with the worn-out motor that had to start with.  Also always try to NOT use  prop shaft extensions with these engine, as it adds a  lot of  wear on the crankshaft bearing.


Regards 
Randy

Offline John Watson

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Re: Fuel for Fox 35
« Reply #10 on: July 07, 2019, 02:15:32 PM »
Thanks for all the input...…...I have four old Foxes that I would like to get flying again...…………


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