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Tuning a Fox .35. Need advice. - Page 2 Empty

Tuning a Fox .35. Need advice.

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Post  Ken Cook Mon Feb 10, 2014 4:58 am

Matt, how new is this engine? Just for the record, breaking in a engine with NO muffler is in my opinion far superior to using one. My field however has a strict muffler rule. A leaking needle valve or tank will cause a very erratic and hard to set needle condition.  Let me suggest this to you, put a 9x6 on the engine while it's on the stand. It's far less load and it will get it out of the vibration area. I may be diagnosing this incorrectly, but one thing a Fox will do especially when new is vibrate. Put a little Armor -All in your fuel ( 1-2 squirts to a gallon) and run it again. Set the engine running in a two stroke with a slight return back into a 4 stroke. Audibly, it will sound if the engine is changing back and forth in rpm's and not a steady monotone high pitched run. If the Fox isn't ready for this, it will sound if someone is clamping down on the piston and it will slow down even further and lock up and stop. If this happens, don't panic, nothing is wrong and let it cool down. DOn't touch the engine it will be hot and if this happens a few times, you will notice the discoloration on the case and head of burnt oil. Again, not a problem. I personally take them apart and do a thorough clean up of several parts and I no longer try to break them in by using gallons of fuel. While I did this with many, I can say from my experiences my methods nowadays not only get me in the air quicker, but it also gives my conrod a lot more life. The conrod is not the best of the bunch in the Fox and it's subjected to a lot of force usually egging out the large end and also the wrist pin hole in the piston. My suggestion of a smaller prop but with 6 pitch keeps the rpm's up and load off of the engine and also gives it more cooling when it needs it most. Let us know your findings, I really enjoy playing with these and pretty much made it a hobby in itself. Ken
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Post  Cajun66 Mon Feb 10, 2014 5:58 am

It's an older engine.
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Post  Cajun66 Mon Feb 10, 2014 2:41 pm

My thanks go out to Sharon at Foxengines. She fixed my snafu in nothing flat.
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Post  Cribbs74 Mon Feb 10, 2014 3:17 pm

Good deal, glad she was able to help. I was hoping they would still supply parts. So I assume you grabbed a new style NV? If so how much?  Of you don't mind me asking that is.

Ron
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Post  Cajun66 Mon Feb 10, 2014 4:52 pm

I cancelled the order for now. A friend who owns the LHS tells me he can set it up with a remote needle valve and spray bar.
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Post  Ken Cook Mon Feb 10, 2014 5:13 pm

Not that it wouldn't work, but using a remote needle valve could cause some hesitation problems. One thing is that your needle doesn't respond readily to adjustments, it also typically likes to try and siphon back into the tank upon start up. This is problematic with the LA engines as they suffer the same problem.  The Fox likes to be wet on start up. If your experiencing difficulty now, your probably not going to be happy with a remote setup. The stock  Fox needle is quite the topic of discussion as it can be very problematic. With a little bit of fuel tubing however, it can almost totally fix your problems.  If you have a 3-48 screw that's long enough, you could grind your own taper onto the end. I've done this and it works far superior to the stock needle due to it fitting the spraybar properly.  The stock needle fits very sloppy as the threads are formed and not cut. Ken
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Post  gossie Wed Feb 12, 2014 9:46 pm

I'm new to this site but have used Fox 29/35 engines for a long time in Free Flight Vintage models. Perhaps my info. may help?
I always mix my own fuel because then I know what I'm getting. Fuel mix is 50% methanol, 25% castor, 25% nitro.
Prop. 9 X 6 Windsor or APC. Medium long reach plug.
Engines on suction feed. Choke the engine to draw fuel to the carb. One drop of fuel into carb. and one drop into exhaust......turn it over once by hand.
On with the 2V battery to the plug.
They hand start on one or two flicks or instantly with a touch of the electric finger onto a 2in. spinner.
No muffler so plenty of noise. Needle never needs touching. Can't remember ever blowing a plug.

Hope that helps. Smile 
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Post  Ken Cook Wed Feb 12, 2014 11:23 pm

I don't want to sound like I'm trying to argue with what works for you. I tip the nitro can myself . Just realize that your suggestion of 25% nitro is going to eventually make the Fox shed parts. In fact I see this happen frequently on just using 15% nitro. I do realize the reason your bump starting the model for free flight, but the Fox isn't designed for a electric starter and I'm pretty sure your aware of that.
Using a electric starter on a Fox, especially one that maybe inverted or even side winder format can rip the nose right off of a control line plane if that engine is over primed. Seeing that in control line the tank is slightly higher than centerline, this can quickly load an engine and therefore the above can happen. The Ringmaster for instance doesn't utilize it's doublers back onto the spar and this is the point it will take the nose off if the starter is used improperly. In addition, there's so much end play on the Fox, your grinding the rod into the backplate and also compromising a already weak designed rod. My advice for those willing to try a starter would certainly be not to do so until you obtain a reliable starting sequence.

Running a spinner on control line planes may look cool, but typically is short lived. The majority of planes build nose heavy and therefore unless needed for nose weight I would omit the spinner. It just makes clocking the prop a royal pain and when the Fox backfires it loosens the prop which now requires the spinner to come off . For those that want to sport fly this may not present an issue, but for those flying competitively you just may have to take an attempt to make the needed fix. Ken
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Post  gossie Wed Feb 12, 2014 11:54 pm

Hi Ken,

I understand exactly what you are saying.
The FOXs have all been vertical. Also my suggestion of ONE drop of fuel into exhaust and intake.
I do agree 25% nitro is lots for a Fox 29/35 but have in mind it's started, off with the lead and the model a Playboy Snr. is launched using an under 15 second engine run per our Aussie Vintage Power rules.
I should thing my excess use, and agree it is a little over the top, but because it's all short run stuff unlike CL or RC that has kept my engines in fine fettle.

I do appreciate you post, and if I may suggest less nitro......10%? in CL or RC.

My main point of my post was to try and help a guy get his FOX running and running steadily as mine always do being the noisiest on the field so I'm told.
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Post  Surfer_kris Thu Feb 13, 2014 12:43 am

@Cajun66 wrote:
Tatone stand hard mounted to a bench.
10% fuel. Can't remember brand off hand.
10x6 balanced prop
Fox short plug. Med temp.

I can make it run, but only if it is tuned extremely rich.

I've seen similar problems with synthetic oils in old engines. Check what fuel you are using, you really do need 20-25% all castor in old-school engines...
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Post  gossie Thu Feb 13, 2014 2:04 am

@Surfer_kris wrote:
@Cajun66 wrote:
Tatone stand hard mounted to a bench.
10% fuel. Can't remember brand off hand.
10x6 balanced prop
Fox short plug. Med temp.

I can make it run, but only if it is tuned extremely rich.

I've seen similar problems with synthetic oils in old engines. Check what fuel you are using, you really do need 20-25% all castor in old-school engines...

Totally agree. Castor all the way for me thanks.

Just further to using the electric finger on let's say a FOX, I am flying Free Flight and to be behind the prop. then put it into the starter, off with the lead and launch. It all takes a couple of seconds.
If I decide to flick it and can feel a thermal arriving then the time I hook up the lead, flick, start, then have to climb over the model......it's big at 80in span, the thermal can be gone.....it's all such a worry for us Free Flighters. That's all okay in trimming or practice but in competition you need to be quick.
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Post  ama353 Sun May 04, 2014 1:34 am

I really have spent little time in these Forums, and logged in to see how Bernie is doing searching for a Fox 35 stunt engine for a customer.  Hence I've been looking at Fox 35 topics ...
 
Sometimes what I see seems to prove the old adage, "There's nothing new under the sun."  Really!
 
Call me a die-hard Fox fan I guess, but those poor engines can be both the most rewarding and the most frustrating, the most raved about and the most cursed ...  well, you get the idea.
 
I bought my first NEW stunt 35 about 1955 - after running a used Fox stunt.  Let me tell you, I was suddenly flying with the "Cadillac" of engines after spending endless hours simply trying to start competitive engines of the time, like say the McCoy "Super Stunt" series (my mentor described my .29 as having "the compression of a toothpick in a sewer pipe").
 
Another big change - when you buried your plane up to the leading edge in terra firma, you simply brushed off the dirt, removed the glow plug, flushed lots of fuel through every hole you could find, replaced the plug, started the engine, and flew again.  Those engines will run reasonably well with enough foreign matter in them to destroy many other engines.
 
(Which is why Duke Fox himself stated that ball bearing engines have less starting friction and MAY produce a slightly better top end, but if you're flying combat and may need to restart your engine in a less than "clean" state, choose needle or plain bearings.)
 
Now, let's think a couple of things through ... We ALWAYS filed a flat spot on our needles - in the 1950s - because the needle could then be screwed in further.  Much less chance of breaking a needle valve.  Very important when it took this teenager several weeks to come up with enough money for the engine ...
 
Having trouble disassembling the engine?  Use your head ... and the oven!  Put a cookie sheet reserved for this purpose - or something similar - in, set the oven at 350 degrees, and check the engine in a few minutes.  The case will expand with heat much more than the sleeve and piston.  If necessary, increase the temperature to as much as 425 degrees.  Be sure to use some kind of glove when handling the engine.    Laughing 
 
With enough heat, the cylinder sleeve will pop up when the crankshaft is rotated even slightly; the con rod/wrist pin/piston assembly will often literally drop out too.
 
I've cleaned hundreds of Fox 35 stunt engines over the years.  The antifreeze in the slow cooker treatment is beneficial if you're careful not to leave it (crankcase, head and backplate especially) in too long.  Dawn Power Dissolver has worked miracles for me - let's hope we find a substitute!  Then hot water, brushing gunk off with a stiff toothbrush, followed by dipping in Air Tool Oil and then fuel (or, in some cases, directly into the fuel mix).
 
Reassemble the engine with generous amounts of oil - I suggest a potpourri of Hoppe's #9 gun oil, 3-in-1 oil, and air tool oil.  And replace all gaskets.
 
There are those who say 3-in-1 oil will dry out ... well, my mentor passed away a couple of years ago.  He had several Fox and K&B engines he'd oiled up with it in the '50s, then wrapped the engines in rags and put them in covered coffee cans.  The engines turned over as freely as if they'd been run and oiled the day before.
 
This stuff has worked for me - I've cleaned up and sold thousands of engines over the past 15 years or so!
 
That's my story, and I'm sticking to it.
 
Dennis
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Post  ama353 Sun May 04, 2014 1:46 am

Fuel: I spent 7 years in a Chemistry Research Lab.  Blended fuels and sold them in several Upper Midwest states in the '60s.  I've done lots and lots of testing.
 
Comments: If you're experienced - and good at setting needles - go ahead and run a blend of castor/synthetic.  I actually sold a stunt fuel that was great for the Fox 35 - it was about 12% synthetic, 11% castor, 2% additive.  You could pull the backplate off a Stunt 35 and think someone had just oiled it with a clear oil.  Problem: that additive is no longer available in anything less than massive quantity, and at a price that might cause most banks to close.
 
If you're inexperienced, or maybe don't have a fine ear for setting the needle - use straight castor!  One overly lean run will do tremendous damage to engines with this "old" metallurgy.
 
That's my second story, and I'm sticking to it.
 
Dennis
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