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Engine basics => Engine set up tips => Topic started by: frank mccune on June 27, 2016, 04:25:13 PM
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Hello All:
I am unable to stop the fuel line from supplying the engine with an inconsistent supply of fuel to the engine. This is not foam but voids in the stream of fuel to the engine from the tank.
I have done the following:
Balanced the props.
Changed engines.
Reinstalled the tank, metal.
Checked for leaks in the tank and fuel lines. The tank is a regular stunt tank with two vents and a supply.
Added Amour All to fuel.
Checked the integrity of the engine mounts etc. Nothing loose here. Perhaps an aluminum pad under each engine lug may help.
The plane is a Nobler built 1961-1962. It appears to be ridged with no flex or loose spots. Perhaps it is so old and dry that the fuselage is acting like a tuning fork. I can not dampen the vibration by holding the nose area in my hand. The engine is not vibrating much as indicated by the tip of the glow plug while the engine is running. I have seen much worse vibration without any erratic fuel supply.
Perhaps I should remove the tank and surround it in foam rubber to help deaden any vibrations. Anybody do this in a Stunt Plane? Or. Heaven forbid. strap a tank on the outside of the nose with a balloon in it ala the 50's. Lol
What did I miss sort of removing the covering and regluing all of the joints. Aaaaaaaaaaaaaaaaaarrrrrrrrrrrgggggggggh!
Suggestion or comments?
Tia,
Frank McCune
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The Tanks Only 50 years old , do you need to put fuel in it , or is some still there . :##
Blankety feed pipe mayve snapped inside , try tilting the plane about with a long length of tube fitted to the feed , and try sucking and blowing , to see .
The black foam meat tray type thingos at the supermarket make good packers / spacers for shimming tanks .
Some Dudes like SILICONE , like the fish tank / window / no more leaks clear tytripe for glueing in tanks .
Armourall Here now isnt good . Some People are saying it screws your glowplugs , anyway .
But if it loks like those wirde noodle in your filter , it may be armourall siliconeing it up .
If You Stand your plane on the outer tip , youd think it'd feed neat fuel , not bubbles . H^^
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This is likely a problem with harmonics in your old dried out or overly lightened front end airplane. I have one of my ships giving a little of that right now. Six or seven of these and one with the issue. The wing in this one is different though and I don't think it's transmitting/ transferring vibration out away from the nose to dissipate like the others do. You need to change the harmonics somehow by , say, fiberglassing the nose or like I'm trying, playing with two and four blade props rather than my standard three blade and at slightly different pitches and rpms. I'm finding better luck on mine this way. If they aren't already, fill in between your motor mounts with solid 1/2" sheet balsa as well.
Dave
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Hello Matt:
No, the tank did not have any fuel in it. I could have sold the fuel on E Bay to be period correct for a person who flies Old Time Stunt!
I turned the plane with the outboard wing down and sucked the fuel out of the tank to determine if this caused any bubbles in the fuel line. Nada! I turned the plane with the outboard wing down while the engine was running and I still got no bubbles! How can bubbles form when the pickup tube is submerged in nearly 2 inches of fuel? The next thing is to strap a tank designed for a profile plane to the outside of the plane to determine if indeed it is a vibration problem or a bad built in fuel tank. I checked the built in tank for leaks and again, Nada.
Perhaps I should just hold a tank in my hand while the plane is running to isolate all vibration. This will require some thinking out of the box! Lol No problem. Just remove the external tank from the plane after the plane is running and hold it in my hand away from the plane. I think that this is a job for at least two people! Lol It should provide couple of exciting moments. This is where one finds out who his real friends are! Who says modeling is not exciting? Just cut the rubber bands that are used to hold the tank to the outside of the plane while your helper, former friend, holds the plane. Hold the tank away from the plane and see if the problem goes away.
There must be a more simple way!!!!!! Lol " I picked a bad time to stop drinking."
Be well my friend,
Frank
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Hi Dave:
Thanks for your insightful reply!
I forgot all about the field of harmonics! This makes sense! Some times we MUST think outside of the box for solutions. I will play with different props, reinforce the front end and make other changes. There must be an answer to this problem.
I have been told that one forgets 80% of all that one learns in his lifetime. I guess that in my case, 80% of very little leaves very little knowledge to refer to for help.
A quote that I have remembered for may years is, "Do not be bound by reality." A paradigm for the 21st century?
Be well,
Frank McCune
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Are you using an in line fuel filter?
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Hi Chris:
Yes, I am using an inline fuel filter. I read somewhere that a filter would help with fuel foaming. NOT
Thanks for the reply,
Frank
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Well, that was my one tip, but looks like it's no good for your situation.
At least I will find out what worked when you do....
Hope it's soon.
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Frank,
First thing is to replace all the fuel lines with new, make sure all the edges of the metal tubing is smooth with no burrs. Test the run, if that doesn't cure it. Does the tank have brass tubing for the pickup tube? Is it a uniflow tank layout? If so, you could have a crack or small holes in the line near the front that could suck in air when the ship is tilled back or from the uniflow line. Brass tubing reacts with nitro and can develop cracks and/or small pin holes that cause the kind of issue you describe. Simple test is to connect a conventionally vented good tank externally and run the engine and see if that cures the bubble. If yes, built or buy a new tank.
Best, DennisT
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what of the exalted Armor All soulution??
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what of the exalted Armor All solution??
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Hi David:
I tried it with no success.
Frank
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I have no facts to back this up, but some time ago, I read on one of these forums that the Armor All spray protectant formula was changed some time ago. The "magic" that Armor All used to do to prevent fuel foaming evidently does not work as well now. (I still have a sufficient quantity of the old stuff to last for a few more years.) It takes on "squirt" in a gallon of fuel to keep it from foaming. I do not know if new Armor All does that, but it is easy to check out. Shake up a new gallon of fuel. You will see foam. Add a "squirt" of the Armor All. If it still makes foam after shaking, then there is no need to use it. It the foam fails to appear, it is a good bet that foaming fuel during flight should not be a problem. "Taters" notwithstanding. I will put up with "taters" if they form. My experience is that the plugs I use go bad long before any "taters" form.
Keith
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Hi All:
Thanks for the replies!
Ty: It is not a Fox! It is the old TL OS .35S that he converted to a .40.
I checked tank with air pressure while it is in the plane but a leak in a fuel tube that is in the plane may not show a leak doing this.
I will cut the tank out of the plane (ugh), and check for leaks while the tank is submerged in water. But before I do that, I will strap a tank made for a profile on the outside od the fuselage to see if it too produces any bubbles. If so, vibration may be a problem.
The tank has most likely been in the plane since it was built circa 62-63. There may have been some corrosion that has developed in the tank since then. This also prods me into removing the tank. Is there an easy way to remove a tank that has been glued in place for decades? Lol
Be well,
Frank McCune
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Just a thought, if the tank is that old and the tubing is made of brass it might have split inside the tank.
So the tank might pass your leak test, but there could be an air leak inside the tank.
The splitting problem with time is one reason that it is suggested to use copper tubes when making tanks.
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If it's not the tank, maybe a leak in the fuel filter or fuel feed line? Or maybe the tank is loose in the airplane? Have you gotten it out yet? I would cut out the bulkhead behind the engine and make the tank removable that way. Yes, it's inconvenient to have to take the engine out to adjust the tank height...but less inconvenient than cutting it out yet again. n~ Steve