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Building Tips and technical articles. => 1/2 A building. => Topic started by: bob werle on May 20, 2009, 09:27:02 PM
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I have tried to make a balloon tank from the information I found here and now have questions on why they dont work. I am using a balloon alled water bombs, I have the inside tubing notched ib 2 places. There is a short piece of copper tubing in the neck and tie it in with a twist tie like they use on bags in the produce dept. of the grocery stores. The problem is it will not seal around the neck of the balloon. What am I doing wrong?
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Twist the tie tighter. Or use a rubber band, multiple wraps.
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A rubberband is the answer.
Larry
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Bob,
I have solved the leaking problem this way.
Like you, I place a short piece of copper or brass tubing at the neck. I then cover this splice with a 1/2'' long piece of large diameter silicone fuel tubing. This increases the diameter of the neck reducing the number of folds in the balloon neck when bound. Instead of wire or rubber bands, I buy a quantity of small nylon cable ties and use one per balloon. These can be cinched up tight by hand. The ties working against the flexible large diameter silicone tube at the neck gives a perfect seal every time.
Orv.
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I use fine brass wire and wrap it hard about 6 loops around. Then I twist and pull, twist and pull until the wire is clearly compressing the balloon into the fuel tube. Clip the end of the wire and bend it forward so it won't puncture the tank. Remind me and I will bring one to the next meeting. In fact, that might make a good show and tell demo.
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Thamk you for the information. I will try the fuel tubing under the ties first. It looks like the easy way to tighten the seal. Once again your help is great to a retread like me.
Bob
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How critical is the height of a balloon tank in relation to the venturi ?
I am redoing someone else's plane and plan to use a balloon tank with a
Norvel BigMig .061 . It originally had a TD .049 using pressure .
Bill
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Most all my .049s seem pretty tolerant of tank height, anything reasonably close to centered works well. Probably because we don't use a 4/2/4 break, but peaked out pretty close to max. Seems like that makes them less critical of fuel pickup location. Once peaked out they just stay there, upright or inverted--unless you're talking about an extreme tank misalignment!
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I have noticed a sensitivity to tank height in the AP Wasp. As such, the tank compartment on the Mark 2 version of the Sky Sport can be assembled on the centerline or shimmed up 1/16". Cox engines are OK fully symmetrical as far as I know, thus the ability to go with the neutral location.
The Mk 2 features 1/2" longer nose and trike gear. It should be available soon.
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How many flights are you guys getting before you have to replace the balloon tank ?
Bill
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How many flights are you guys getting before you have to replace the balloon tank ?
Bill
It isn't really a "number of uses" issue so much as a simple "time elapsed since first exposure" issue. Maybe a month, maybe 6 weeks, I never really kept track, I just keep several made up and if one starts getting a little sticky I replace it. It's not like cost is an issue!
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Bill, i have had some last as long as 6 months and some as long as 6 days. For the price there may be a small quality issue sometimes,, but over all they can't be beat ,, yet!! I do run some balloon tanks on the platters with the motor running very rich at launch in order to do a 4-2 break for training maneuvers and some will tend to vary the runs between upright and inverted flight according to the tank height, but for general purpose slightly rich 2 cycle running the tank height is not so critical. I have as many as 7 or 8 ready to go at anytime.. Keep working with your setups and i believe you will find one to suit your flying. These "tanks" and a decent running engine are way too much fun!!!! y1
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This thread needs pictures, even if it is ancient.
Not shown is the tubing inside the balloons -- it has several holes drilled across the tube, so that the fuel can always get to the motor.
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Tim Wescott, is that a pill bottle for the tank container? If not what then? Thanks a lot
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Tim Wescott, is that a pill bottle for the tank container? If not what then? Thanks a lot
It's a sheet of 5-mil acetate (windshield material) rolled in a cylinder and held down by two screws and a little plywood strap.
Because it's open on both ends, the feed line for the motor has a lug soldered onto it, which is held down by a motor mounting screw. That keeps the balloon from sliding out the back of the tube.
Folks have recommended saving promising-looking bubble-pack containers, and using the "bubble" part to contain the balloon. I haven't tried it. I did try a ping-pong ball on the Beginner Ringmaster before I made the surround out of 1/64" plywood. Did you know that ping-pong balls are very soluble in model airplane fuel?
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Did you know that ping-pong balls are very soluble in model airplane fuel?
No I didn't. I was of the understanding that ping pong balls were celluloid which would resist fuel, but I never tried an experiment.
Phil
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No I didn't. I was of the understanding that ping pong balls were celluloid which would resist fuel, but I never tried an experiment.
In my second photo above, you can see a balloon surround that's made out of plywood -- it's lite-ply top & bottom, with 1/64" ply wrapped around that. Originally I had cut a circle out of the fuselage just big enough to hold a ping-pong ball, with the firewall neatly glued to that, and braces, and all that lovely stuff. Only after I had everything nice and finished and pretty, with a balloon stuffed into the ping-pong ball and everything, did I slosh some fuel on it and watch the thing just absolutely melt in front of my eyes.
"Frustration" does not quite capture the feeling I was experiencing at that moment.
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In my second photo above, you can see a balloon surround that's made out of plywood -- it's lite-ply top & bottom, with 1/64" ply wrapped around that. Originally I had cut a circle out of the fuselage just big enough to hold a ping-pong ball, with the firewall neatly glued to that, and braces, and all that lovely stuff. Only after I had everything nice and finished and pretty, with a balloon stuffed into the ping-pong ball and everything, did I slosh some fuel on it and watch the thing just absolutely melt in front of my eyes.
"Frustration" does not quite capture the feeling I was experiencing at that moment.
That is an elegant cavity. I was not sure what I was looking at before!
Yes, verify then use. I have been doing that with various paints since dope is hard to get for me.
Phil
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That is an elegant cavity. I was not sure what I was looking at before!
Some informative pictures:
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Some informative pictures:
I like it! But how do you get the balloon in and out? Also dose oil from the 2-cycle fuel collect in the cavity?
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I always Epoxy coat the interior as fuel does get in.
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There's holes in the bottom to let excess fuel weep out, and to let the air out as the balloon fills.
And yes, the inside's painted with epoxy.