My First Balloon Tank Attempt

I would secure it.

I use flourescent light tubing sold at Lowes or Home Depot. It's plastic and cuts easily.

Here is a poor picture of what I am talking about, disregard the limp TD. It was an interesting maiden flight.

I'll bet it was an interesting flight. Thanks also for the idea and suggestion to secure this thing. I guess a film tank it will be, or maybe a fluorescent light tube as well. Off to go shopping for supplies, or dumpster diving....

Regarding your fluorescent light tubing idea (or film tank, hotel shampoo bottle, etc). Is it just there to keep the fuel delivery device secure? Probably a stupid question, but I just gotta ask.

Yes,

Just to keep it secure. There are some pretty extreme forces going on in flight and that little brass nipple is not enough to keep the balloon attached.

Yea..  you'd get a ten+ minute flight out of that balloon I would think! This is something I've been wanting to try too. I would try to make a fairing/nacelle for the balloon. I wouldn't let it flap in the breeze. I've made some un-tested prototypes using the clear-plastic tubes that single-stem flowers are shipped from the florist in. The balloons I chose, are longer.. as opposed to wider. Search your local "party" supply store.. they have a good selection of sizes/shapes. Keep in mind; you shouldn't need to inflate the balloon.. just fill it. Cut it shorter if you need to reduce the fuel capacity.




Like I said; my approach is un-tested as of yet.. but the tube affords a rigid/semi-streamlined mount and also protects the balloon. I've read that you need to fill with a syringe.. and suck all the air out of the balloon prior to filling. I would imagine this to be a reliable stunt-tank for a reed-valve engine. My silicone pick-up line is notched thru the wall in a few places. I used a small 1/8" paper hole-punch.. but you accomplish the same by cutting a couple v-notches using a razor knife. The idea is; if the balloon collapses over one fuel inlet.. there's another to provide a feed. Since there's no air in there.. you shouldn't experience an interruption in flow.

I agree, it needs to be secured from flopping around. You'd be fighting centrifugal force pulling the fuel away from the engine with it straight out to the side.
Here's one like I've used. This is not adequately secured, but something like Ron and Roddie mentioned work well. You can use silicone line with notches cut in it internally instead of the brass.

Again, thanks all for the help, pictures, and advice. I now have a lot to go on. And roddie, yours is very similar to the one I made with the exception of the balloon design.

Blowing the dust off this thread.... (there's a few balloon tank threads.. ) but I had posted here back 9 years ago. Still; I've yet to to try-out any of my balloon-tanks. I think I was on the right track though.

Here's a pair of very small balloon-tank systems that I just put together last night.. that I'm hoping will work-out for the boat (rigger) that I've been working on.







The Tee fittings came from McMaster Carr Co. and the silicone tubing is .062" X .093" which came from Amazon. The "tubular" red balloon has an approx. 7cc. capacity.. and the smaller round red balloon has between 3-4 cc's capacity. I'll try using a "pinch-off" on the line just downstream of the TEE (to the engine..) while evacuating air and subsequent purging with fuel. My rigger engine is equipped with a choke tube which will aid in pulling fuel into the carb.

Nice Roddie…. When you go thru the testing procedure for boat use let us know how it works out…. I’ve used a single line balloon for CL application and a two line for RC…. Filling and air removal are a little different for each one but both provide steady runs all the way to the end…

rdw777 wrote:Nice Roddie…. When you go thru the testing procedure for boat use let us know how it works out…. I’ve used a single line balloon for CL application and a two line for RC…. Filling and air removal are a little different for each one but both provide steady runs all the way to the end…

That's what I'm counting on Robert.

I do not know if this could be used for a single use or if the plastic is fuel compatible, but just an idea for ease of plumbing.

I have been using 2-line unpressurised balloon tanks in my small RC planes for many years. One important step for proper fuel feed is to evacuate all air pockets from the balloon after filling. Hold the plane or boat vertical with the fill tube on top while the filler syringe is still attached, and pull on the syringe piston until bubbles stop rising from the balloon. Then press back to the balloon the fuel only .

balogh wrote:I have been using 2-line unpressurised balloon tanks in my small RC planes for many years. One important step for proper fuel feed is to evacuate all air pockets from the balloon after filling. Hold the plane or boat vertical with the fill tube on top while the filler syringe is still attached, and pull on the syringe piston until bubbles stop rising  from the balloon. Then press back to the balloon the fuel only .

Hi Andras, Are there any instructional-videos on the web (YouTube)? I'm pretty sure that I understand the concept.. but I know that many people are more "visual" in the way of interpreting certain processes.

Roddie,

I do not have any videos on how to evacuate the balloon tank, but attach below a photo of one of the tanks, having  separate filling and supply lines.





This shows the belly of my Quickie100  with the hatch removed ( many moons ago and before tens of hours of fantastic air-time, still crispy and clean with no castor infusion into the balsa...looks different today, unfortunately) . The left side line is the supply line with a filter, and the right side line with the black plug is the filler, and this line ends right after it crosses the "stopper" plug in the neck of the balloon...so the end of the filler line is flush with the top of the balloon storage space, when the plane is held nose-up (like in the photo), thereby all air  bubbles will accumulate there in a nose-up position, which can be evacuated through the filler line, when its end is still attached to the filler syringe. Pulling on the syringe piston with the plane in nose-up position will draw the air pocket from the tank top..after the air evacuated - which is clearly visible if a transparent/clear syringe is used - , one can pinch the supply line with your fingers, remove the syringe, and close the line with the black plug.

I trust to have clarified..

Here’s another visual Roddie… Same tank as Andras described, … In fact, I learned these from him …..The fill/ air evacuate line is the one that is plugged…. The brass tube is flush with the back of the stopper as described…… The other line is feed to the engine…. The brass tube is connected on the inside to a length of silicone fuel line that is perforated along its length similar to yours….. There is not a Tee fitting in this system….Interestingly, The latex balloons last a surprisingly long time….. I give them a hard vacuum at the end of a flying session to pull out anything that is left then store in a dark place….

Thank You BOTH!!!

Just for comparison’s sake, Here’s a single line tank I made for my Firebaby CL plane…. To be somewhat close to the original design….. The original’s were simply one piece of neoprene tubing from the engine to the back of the balloon….. I used a piece of brass tubing thru the stopper to the back of the tank with the pickup shown…..

On this one the nose of the plane is pointed down and the air goes to the back of the balloon after the fuel is injected…..Air is then pulled out with the syringe until a solid stream of fuel appears…Then connect to the engine…

Thanks again Robert! I'm testing the use of a short (approx. 1/2" length) of rigid tube inside the "neck" of my balloon.. with silicone tubing covering that rigid tube.. and using a small zip-tie around the balloon's neck to seal.. rather than using/making a stopper. (without the rigid tube, the softer silicone tubing would collapse with the tightening of the zip-tie; thus preventing flow)

This is also a weight savings; as opposed to using a conventional-type stopper inside the balloon's neck.

I’ve tried several methods of doing a balloon tank, and the last one I came up with was my favorite for control line.  Unfortunately, I don’t have a picture of it.  But it’s pretty simple to explain.

I just take a round party balloon of the size I want.  I think it was a 7” balloon I last used.  It should be a balloon made for Helium use.  What you do is get a tube of your choice, fuel tube with notches along the length for me, and cut it the length of the balloon plus about a ½ inch.  You could use a small brass tube, or just plastic tube notched along the length if you'd prefer.  Then you take a pair of nail clippers and nip the end of the balloon.  Push the tube through the mouth of the balloon and through the small hole you nipped on the end.  I used a small cable tie to cinch the mouth and the end of the balloon around the tube making it fuel tight on both ends.  Attach your fuel tube from the mouth end to the engine.  Attach a short piece of fuel tube that can be plugged on the other end.  I just left the fuel tube open on the end so that I could plug the nipple of a syringe into it.  

To fill the balloon, I clamp the fuel line between the tank and the engine, then fill the syringe most of the way with fuel.  I squeeze the air out of the balloon before plugging in the tip of the syringe filler to the rear of the balloon tank.  Since the syringe isn’t completely full I can pull the plunger back a little to suck the last of the air out of the balloon.  Then I hold the syringe up so the air I sucked out is at the rear of the tube, and press the plunger in to fill the balloon to its natural round shape.  DO NOT fill the balloon so that it is blown up under pressure with fuel.  This IS NOT a pressure tank like a bladder.  If I remember correctly, a 7” balloon will hold almost an ounce of fuel in its natural shape.  Once the balloon is full of fuel, remove the syringe nipple from the tube and plug it by your favorite method.  Voila!

The Up, Up, and Away Mark


edit: Maybe I'll make a video and put it up on YouTube. I haven't put up a How-To video in a while.

That's a good explanation Mark. It's not always an easy matter to "write" a procedure (sans photos/illustrations).. in a manner that's clear and understandable.