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Old Mar 07, 2013, 04:38 AM
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I have several 10oz tanks on 20cc gas planes and never have a problem. I think Dar has it right, that a felt klunk absorbs the vibrated fuel without the need to be immersed completely.
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Old Jun 17, 2014, 02:53 PM
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UK, Cambridgeshire, Huntingdonshire
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Originally Posted by earlwb View Post
Normally one does not use muffler pressure with a gasoline engine setup. I suggest using a three line setup for the fuel tank, one line is the fuel line, one line is for the vent and the third line is for refueling and defueling the fuel tank. I use a large loop or two for the vent line so that the fuel doesn't siphon out if the plane is inverted.

The gasoline engines use a pump carburetor so they do not need muffler pressure. You can pretty much place the fuel tank any place inside of the airplane as the pump in the carb draws the fuel for the engine and provides the fuel at a constant pressure via the fuel regulator to the engine.
I don't understand - How do loops in the vent stop the tank siphoning out when inverted?
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Old Jun 17, 2014, 03:12 PM
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Ok Ok I asked that question before seeing those drawings. Alles klar!
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Old Jul 30, 2014, 10:37 PM
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Gotta ask in case someone is still on this. I am setting up my first gasser a 20cc evo the new small block one. I have it running great on the ground, starts easy etc. good transition nice top end. When I lift the nose high it revs up and point it down it wants to stall unless I keep throttle for 4000 to 5000 rpm before pointing down? Is this something to do with the needle valve setting or perhaps a bad tank setup? The plane is a h9 spitfire 60, I used the included tank but switched out the stopper and line for the HH recommended line. Went with a three line system and it uses carb pressure like a glow.

Any thoughts guys?

Marlin
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Old Jul 31, 2014, 09:50 AM
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East Texas
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Originally Posted by Fish99 View Post
Gotta ask in case someone is still on this. I am setting up my first gasser a 20cc evo the new small block one. I have it running great on the ground, starts easy etc. good transition nice top end. When I lift the nose high it revs up and point it down it wants to stall unless I keep throttle for 4000 to 5000 rpm before pointing down? Is this something to do with the needle valve setting or perhaps a bad tank setup? The plane is a h9 spitfire 60, I used the included tank but switched out the stopper and line for the HH recommended line. Went with a three line system and it uses carb pressure like a glow.

Any thoughts guys?

Marlin
Double check that the system is pressuring up. Check that the pressure line off the muffler remains attached and has no holes or is not kinked. If the needles are tuned without pressure for a good mixture going vertical, it will be far too rich coming down hill. Muffler pressure is critical on the gas Evolutions, except the 33 which has a typical Walbro type carb and uses no muffler pressure.
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Old Aug 05, 2014, 11:26 PM
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Thanks. I did a complete redo of all fuel lines. Got rid of the tubing they sent with the motor and went with more flexible gas fuel tubing. Was finding the HH stuff cracking lots. (Had two fuel leaks actually.).

Now onto yet another issue. Been seeing rf interference from the ignition. Ignition box is in front of the firewall. Rx is behind COG. When reving up higher on the bench I get un commanded spikes of aileron movement. The higher the rpm the more flutter.

Checked by physically touching the surface and it is definitely servo driven movement not flutter. At times full deflection. Does not happen when you first run it up it as things gave been running a bit then it starts to show.

Moved the sat Rx as far away as possible. About 15 inches away.

Is it possible the ignition module us acting up, putting out rf as it gets warm?

Any thoughts folks?

Marlin
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Old Aug 06, 2014, 12:55 PM
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The fuel tubing supplied by HH is stiff and it will crack as noted if stressed too much. However, there is one place it is completely necessary and that is the pressure tap on the muffler. The muffler gets too hot for tygon tubing. And... muffler pressure is a necessity with the carbs on the 10,15, &20 GX series engines.

Some interference is caused by a inadequately secured spark plug cable. Be certain it is fully on the plug. Another issue is actually not RFI from the engine, but signal overload from the transmitter. When checking, be sure to have the transmitter 8-10 ft from the aircraft. I've seen this and experienced it myself.

When RFI is coming from the engine, it can go into the receiver or often gets into some servos because of a particular wave length of the interference matching that of some of the servo cables. I'[ve also at times had to isolate a receive antenna further from a set of pull/pull rudder cables. The rudder cables seem to be acting as an antenna passing the RFI to the receiver because the receiver antenna was close coupled.
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Old Aug 06, 2014, 02:03 PM
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Originally Posted by AA5BY View Post
The fuel tubing supplied by HH is stiff and it will crack as noted if stressed too much. However, there is one place it is completely necessary and that is the pressure tap on the muffler. The muffler gets too hot for tygon tubing. And... muffler pressure is a necessity with the carbs on the 10,15, &20 GX series engines.

Some interference is caused by a inadequately secured spark plug cable. Be certain it is fully on the plug. Another issue is actually not RFI from the engine, but signal overload from the transmitter. When checking, be sure to have the transmitter 8-10 ft from the aircraft. I've seen this and experienced it myself.

When RFI is coming from the engine, it can go into the receiver or often gets into some servos because of a particular wave length of the interference matching that of some of the servo cables. I'[ve also at times had to isolate a receive antenna further from a set of pull/pull rudder cables. The rudder cables seem to be acting as an antenna passing the RFI to the receiver because the receiver antenna was close coupled.
This is great information and I thank you for this. I should be able to check for the signal overload on the transmitter by watching the MONITOR screen while I rev the engine up. If I see the two aileron channels start to flick about while I am not touching the stick then we know the culprit is that! I will also check that spark plug cable to make sure it is WELL seated, that certainly is a possibility.

Not sure what to do if the ignition box is leaking RF to the point of messing with the aileron servos out in the wings! Never so much as a twitch on rudder or elevator. Notice it when I have the COWL off much more than when the cowl is on, so that might be acting as a block when on and not when off. Given the wooden firewall between the ignition and the ele and rud servos, maybe it's just that simple. Was actually thinking about putting a little bit of metal / tin foil around the module between it and the firewall, as well as the sides leaving open the front for air cooling. The intent would be to act as an RF barrier between the ignition unit and the electronics on the plane.

Do you, or does anyone else, have any experience is doing this? Any issues? I don't see any bare wires, etc., that would create a grounding or shorting risk.

Thanks again for the great advise.

Marlin
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