Tettra bubbless plumbing&filling

Tettra bubbless plumbing&filling (Full Version)

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Methanolover -> Tettra bubbless plumbing&filling (1/28/2008 9:44:04 PM)
Hello bob! I got hold of a 18 oz Tettra bubbless tank. Instruction shows a different (from Jett) filling up procedure, involving a "air ejector-tube" (where air escapes as fuel enters the bladder) and use of a traditional fuelpump. What do you think about this procedure? don't you think the tank will be filled up with a fuel containing those small bubbles of air? Should I better use the Jett-procedure without that "air ejector tube" and use of a "Jett-tanker" BR Henrik

bob27s -> RE: Tettra bubbless plumbing&filling (1/28/2008 10:06:03 PM)
I guess I never considered what the instructions say with the Tetra tanks all that much. I believe the method decribed has to do with using a "vent" tube (third line) that goes to the top of the fuel tank. Air and fuel vent out of that tube, which is then sealed off after fueling. The tank is pressurized then on the outside of the bladder. Someone told me they used the tetra tank in this fashion, and it worked ok. You fuel as if it were a conventinal tank. Does make things easier especially with the larger tank volume. And there is less risk of pressurizing or bursting the bladder. But as you noted, there is always a risk of a bubble of air left in the tank under some conditions. A good deal of making this work is to ensure that the vent ends up where the top of the tank is, and this where the air bubble might form. I have always filled tetra tanks using the same extract-and-fill method used with the Jett tanks. Takes a couple of loads of fuel, and some clamping the fill line while making the change. But it has not proven a large problem. Bob

Methanolover -> RE: Tettra bubbless plumbing&filling (1/28/2008 10:35:26 PM)
Thank you bob!! for your reply. Maby I try with a third line on test stand while re-running in my .90LX About large tank volumes,, I've been thinking of connecting a tee and two check-valves to my Jett-tanker, one line going to the fuel container, and the other to the tank in the plane[>:] eliminating disconnecting and clamping fuel line when reloading, just pull and push the tanker until the tank is filled. Guess you tried that? with poor result. Right? Best R /Henrik

heliothiszea -> RE: Tettra bubbless plumbing&filling (1/28/2008 11:32:58 PM)
Henrik - I have two bladder tanks that I fill with the air injection / third line method. I fill the tanks from the carb line and hook up an over-flow fuel tank to the air ejection line. When fuel comes out the third/over flow line I wiggle the plane around to get the air bubbles to come out. When no more bubbles come out I plug the third line and re-connect the fill line to the carb. It works for me. I experimented with it on the test stand before I installed it in a plane. I have had fuel siphon out from the third line. The tanker is the more accepted method locally. I guess I wanted to see if it would work. Hope this helps - Seth

Methanolover -> RE: Tettra bubbless plumbing&filling (1/29/2008 7:17:00 AM)
Seth, Thanks for your input! I might test it on the bench. Do you have 2 bubbless tanks parallelly plumbed in your plane? works fine?

bob27s -> RE: Tettra bubbless plumbing&filling (1/29/2008 6:59:57 PM)
quote: ORIGINAL: Methanolover Thank you bob!! for your reply. Maby I try with a third line on test stand while re-running in my .90LX About large tank volumes,, I've been thinking of connecting a tee and two check-valves to my Jett-tanker, one line going to the fuel container, and the other to the tank in the plane[>:] eliminating disconnecting and clamping fuel line when reloading, just pull and push the tanker until the tank is filled. Guess you tried that? with poor result. Right? Best R /Henrik Actually that works, as long as the fill line does not syphon back and let an air-bubble into the system. I remember guys building "pumps" like that for filling Formula 1 bladders (pressure bladders) years ago.

heliothiszea -> RE: Tettra bubbless plumbing&filling (1/30/2008 12:28:13 AM)
Henrik & Bob - I'm sorry for the confusion . . . I have two tettra tanks. One in my club-40 pylon racing plane and one in a modified q-500 plane. I'm not running them is series. They are small tanks, 5.25 & 6 oz tanks. I've fixed my third line or "air line" so it turns up to the top of the tank where the bubbles rise. However, I cap the end of third line inside the tank with fuel tubing. The tubing extends up the last 3/4 of an inch inside the tank. I was worried the bladder might rub on the metal tubing and thought it might help . . . or maybe it was in of the directions. I don't remember. I think it is worth experimenting with on a test stand. You'll get to see what is happening and know if it will work for you. I feel like I'm having good success. The weather looks good for this weekend. I can take a picture if my description is not clear. It seems complicated to explain, I guess a picture could be worth a 1,000 words.

Methanolover -> RE: Tettra bubbless plumbing&filling (1/30/2008 9:46:39 AM)
Bob, Then I'll test it!! /Thanks!! Seth, No need for pic's, I have the picture clear[8D] I will try it coming weekend! that's all our dreadful weather here allows[&o] No flying. But I hope you´ll have a great weekend!! Henrik

MJD -> RE: Tettra bubbless plumbing&filling (1/30/2008 7:17:20 PM)
quote: ORIGINAL: bob27s I guess I never considered what the instructions say with the Tetra tanks all that much. I believe the method decribed has to do with using a "vent" tube (third line) that goes to the top of the fuel tank. Air and fuel vent out of that tube, which is then sealed off after fueling. The tank is pressurized then on the outside of the bladder. Someone told me they used the tetra tank in this fashion, and it worked ok. You fuel as if it were a conventinal tank. Does make things easier especially with the larger tank volume. And there is less risk of pressurizing or bursting the bladder. But as you noted, there is always a risk of a bubble of air left in the tank under some conditions. A good deal of making this work is to ensure that the vent ends up where the top of the tank is, and this where the air bubble might form. I have always filled tetra tanks using the same extract-and-fill method used with the Jett tanks. Takes a couple of loads of fuel, and some clamping the fill line while making the change. But it has not proven a large problem. Bob Since the filler inlet is submerged in the fuel can, I do not believe the fuel is full of air bubbles any more than the syringe is. I've filled my 8oz Jett tanks with a hand cranked fuel pump a few times when I have forgotten the filler syringe. Note this is not pylon racing but sport flying my Magnum. I filled it up until no more fuel flowed, then - nose straight up up - slowly cranked backwards until I saw bubbleless fuel in the fuel line. Had zero problems, but I wouldn't do this in a racing event without more repetition of the technique to weed out any issues I haven't encountered yet. However, it allowed me to fly without a one hour round trip to fetch the fueller. The engine ran cleanly and no blown plugs. MJD EDIT: I forgot - I also sucked the tank dry with the pump in reverse first, then pinched the fuel line, then filled the pump line with fuel before attaching back to the fuel line, to minimize air. There is of course a tiny bit of air introduced at first, but I think it is reliably withdrawn once full with the nose up. Seemed ot be anyhow.

heliothiszea -> RE: Tettra bubbless plumbing&filling (1/30/2008 11:23:12 PM)
Good Luck Henrik . . . hope the weather warms soon. MJD might have something also using a hand cranks pump. This should work fine especially with the ol' six shooter peristaltic pumps. It should be as good as a syringe. Something I may try on my next tank. - Seth

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