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Fuel for Old Fox C /L Engines

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Old 12-16-2012, 10:26 PM
  #1
sehlers
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Default Fuel for Old Fox C /L Engines

Hey Folks ,
Was going to get some of the old Control stuff out to play with . Since I fly R/C I was thinking I could just add some Caster to the Synthetic blends I use now .

Anybody know if taking typical 18-20% oil content fuel up to say 22 -24 % total oil content with caster ,will be enough ? I could use some straight castor
based fuel bought just for them ,but thought I would ask if any consensus of doing this worked well enough .
Steve
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Old 12-17-2012, 02:39 AM
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Default RE: Fuel for Old Fox C /L Engines

I would only use Castor oil in your old Foxes Steve
Minimum of 25% castor. The Original Fox Fuel blend was 29% Castor. 10% nitro
That was not for lube purposes as 25% is enough but 29% castor made the Fox 35 Stunt engines do the 2 stroke/ 4 stroke switch better.

Cheers

Fredo
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Old 12-17-2012, 02:43 AM
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Default RE: Fuel for Old Fox C /L Engines

I've always heard that the general school of thought is NOT to run sythetic fuel through an engine that was perviously run on castor since it will strip out the benificial varnish that seals the piston/liner and crank bearing surfaces. SIGstill makes 25% all castor fuel with nitro at 5-10%. Ialso purchased some extra castor oil to bring the level up to 28% for some of my older engines like the Fox .35's.
Justin
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Old 12-17-2012, 03:06 AM
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Default RE: Fuel for Old Fox C /L Engines

My Fox 15 runs nicely on 5% Nitro and 20% castor.

8X4 prop.

G
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Old 12-17-2012, 04:43 AM
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Default RE: Fuel for Old Fox C /L Engines

Fox engines use old style iron/steel technology and take advantage of the castor building up varnish to protect the piston. Using blended fuel will strip the protective varnish and quickly reduce the compression. I would stick with all castor fuel.
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Old 12-17-2012, 06:32 AM
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Default RE: Fuel for Old Fox C /L Engines

Ok Guys , Thanks for the Jog of my memory . I now remember the why and will use some straight Caster Fuel . Was trying to
do the easy thing for me ,when all I fly now are ABC and late ringed engines and have gallons of fuel for them . I think I will also
do an R/C conversion to a straight venturie on one of my ABC's to use in at least one airplane for Grins .
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Old 12-17-2012, 11:00 AM
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Default RE: Fuel for Old Fox C /L Engines

You won't go wrong with straight castor. A while back I put one of my 1977 Fox 35s on an Old Time Stunt airplane. This engine had maybe a thousand flights, probably on all castor fuel, back in the day. I have put several hundred flights on it with Sig Champion 10% nitro, 20%oil, half castor, half synthetic. It has all the compression one could ask for, generally first or second flip start and steady reliable run. I did get it off lean one time and it froze in the air. No damage or change that I could tell.

I lapped the piston and cylinder before I ran the engine for the first time. Also, I long ago went to 11 x 5 props on Fox stunt 35s. Should mention that I accidentally built the airplane it is in backwards, so had to learn to fly the OTS pattern flying clockwise.
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Old 12-17-2012, 01:54 PM
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Default RE: Fuel for Old Fox C /L Engines

Back in the fifties Fox used to advertise their "Superfuel" (5% nitro, 28% all-castor) for trying to recover worn-out engines by creating the famous castor varnish seal. Some swear that ~25%-28% castor is necessary for enclosed Fox .35's. Others seem to get by with smaller percentages.

Some castor (~half) in the lube can prevent or lessen damage during too-lean runs on iron/steel setups. Unlike AB(X) setups, iron/steel can suffer damaging thermal runaway if the piston expands faster than the cylinder. Most iron piston engines run well on 20%-22% lube.

The problem with some RC fuels is that they are set up for larger BB engines with ABC, AAC, AAN, etc. setups. Some apparently have ~17% (by volume) lube.This is not quite enough for a smaller sleeve bearing iron/steel engines. It won't immediately trash them but they may have shorter useful lives.

These guidelines are for run of the mill engines. There are more expensive engines that have better metalurgy and use more specific types and percentages of lubrication. You shouldn't go wrong by adhereing to what the manufacturer recommends.

Your choice.

George
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Old 12-17-2012, 02:43 PM
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Default RE: Fuel for Old Fox C /L Engines

Reading this makes me realise that I have done a bad thing. Some years back I has at a model auction and saw a Nobler with a Fox 35 in it, I was surprised when no one bid on it and ended up with it for $40 odd dollars.
I learned all about models by flying CL from the age of ten, as all the kids in town were into CL back then, but I had not picked up a handle since starting in RC. I just used the synthetic fuel I had on hand at the time, it seemed to run just fine with it, until I decked the model in some windy conditions.( I would have run back for line tension when I was more current flying CL)

I was looking at the engine the other week, and it seemed to turn over ok, I'm keen to build another model as my interest has been sparked again after reading Chip Hydes post in the RC Pattern forum about his new interest in stunt.

Hopefully I have not killed the Fox, it did about ten flights before its forced retirement, the Nobler I bought has built from a kit, but since I had it the ARF version came out, I will see if any are still in the Australian shops, or it will scratch building time for me :-)
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Old 12-17-2012, 04:24 PM
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Default RE: Fuel for Old Fox C /L Engines

matt13
We have a CL club here in Adelaide if you're interested. The field is the soccer field in Unley Rd opposite the BMX track in the South Parklands but only on Saturday. Most of us get there around 12pm and you'd be more than welcome to come check us out anytime.
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Old 12-17-2012, 11:23 PM
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Default RE: Fuel for Old Fox C /L Engines

Thanks for the offer, I will deflently take you up on that early in the new year, I was looking you guys up on the MASA web site, but did not know what time you kick off from.
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