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Post  RknRusty Thu Mar 29, 2012 10:26 pm

I've been trying to improve on my pressure-less balloon bladder so it's a quick field change and less glitchy than version 1.0. I'm still using the same balloon that holds about 35cc, but works as well with 20cc, which gives the Medallion around 5 minutes of flying time.

The parts needed are a 10 cc syringe, preferably a luer-loc type for the twist-on needles, a 5/16" brass tube, a helium quality party balloon, zip ties and some wide OD fuel tube.
Cut a piece of brass tube shorter than the balloon and perforate it as shown. Deburr it thoroughly, inside and out. Then drill a hole in the rubber plunger and press the tube through it with the pointed side to the rear. You can see the cut-off end of the syringe in the photo. I use a mini butane torch to smooth all the plastic edges and also to give it a ridge to help hold it in place.
Balloon Bladder, ver. 2.0... yes, another project 0329121101

Now insert it into the syringe and use a tool to press the plunger all the way to the base of the syringe tip. Then I used the mini-torch to soften the plastic around the plunger, lay it on the table and use a straight edge to press and roll so the plastic compresses and holds the plunger and tube tightly. The silicon rings are to help the balloon stand off as it collapses so as to hopefully delay the lean end run as long as possible. In my version 1 bladder test, it began to lean and stumble near the end of the fuel supply. The larger one on the rear end is to protect the balloon from the edge of the tube, even though I did smooth it as much as possible.
Balloon Bladder, ver. 2.0... yes, another project 0329121106

Now insert it into the balloon as deep as it will go into the neck. This helps keep the bulk of the fuel over the C/G on my plane. Cut off the excess and zip tie it. I staggered the ties to help prevent leaks.
Balloon Bladder, ver. 2.0... yes, another project 0329121122

Now you have a lot of options for connecting it to the engine and for fueling. I used an orange luer-loc adapter(www.texastimers.com, click on Pressure Bladders in the left column) that screws into the tip of the syringe and has a fuel line barb on it. However a piece of fat fuel line will screw in very tightly and work fine as in the next picture.
Balloon Bladder, ver. 2.0... yes, another project 0329121124

Some more fueling options:
Balloon Bladder, ver. 2.0... yes, another project Th_0329121127 Balloon Bladder, ver. 2.0... yes, another project Th_0329121126

See how I secured the tail end to keep it from flopping in the wind, and also to hold it in place while flying inverted. A zip tie on the tip end of the balloon and a dacron string secured to a rubber band. Pull the rubber band tight during your pre-flight each time you fuel it.
Balloon Bladder, ver. 2.0... yes, another project 0329121205

Here it is with about 30cc of fuel (air in this case). This one will hold a little more. C/L flyers, better make sure you get all of your dizzies out before trying that much fuel. Or it will be tortuous at best. Do not over-fill it. You don't want to stretch the balloon and cause it to presurize.Balloon Bladder, ver. 2.0... yes, another project Ugh
Balloon Bladder, ver. 2.0... yes, another project 0329121208
Remember to evacuate ALL of the air before hooking up the fuel syringe. Careful not to pop one of the pickup holes). I have plastic hemostats used for clamping fragile medical tubes, but you can tape some hemostats to do the job. And I fumble a lot until I get the hang of the fueling routine.

There are different ways to handle cranking it. This list is for front rotary engines which may be easier than Bees. The tankless Bee is described later

  • The air has been evacuated and it's full of fuel. The line is clamped. The needle is already set(the first time is trial and error, about 5.5 turns on the Medallion. After that, just leave it alone).
  • The glowplug is hot and waiting.
  • Unclamp the fuel line. This is where different engines and bladder positions will vary, and you'll just have to get the hang of priming the Bees. With my balloon above the inlet, I have positive fuel pressure, so fuel will flow as soon as I unclamp the feed line and I can see the carb get wet. If it doesn't flow and purge the air that's always just in front of the nipple, tip the nose down and it will flow and prime the engine, tip it back up making sure not to let it draw air back in. Do not prime the exhaust port.
  • If the bladder is below the inlet, it's likely to start pulling air in through the needle valve, so tip it down before unclamping. Keep it slightly nose down while flipping the prop. Keep it level for balloons above or even with the inlet
  • After unclamping the line, without hesitation give the prop a flip. It should start. Haha. If you waste any time between flips the engine Will flood. Close the needle or clamp the line and flip and flip and flip and flip until you burn off the flood and try again. Starter springs make it much easier to start without flooding. That's painfully evident in the earlier video too.
  • Fly the plane.


For Tankless Bees, once you get fuel to the back of the engine, you'll probably have to prime the exhaust port and give it a rip. They might not be so prone to flooding, but the reed might let some into the crankcase. If you have the knack, you can prime it that way. It might take a slight press on the balloon to prime the crankcase. I do not know for sure, as I have never tried. Again, if you flood it, close the needle or clamp the line and burn the flood off before you try again.

I ran my setup this afternoon and it cranked right up and when the fuel ran out it went from normal steady full speed to off. No lean roll, no warning. If you like some warning, leave the spacer rings off of the brass pickup tube. I think with a fresh balloon and a few zip ties you can put another balloon on in the field in a few minutes. The old discarded balloon I've been screwing around with all week while trying to figure this out, looks like it would still work fine. Then again it might feed the engine decomposing rubber and trash the glowplug. But I think the helium quality balloons are pretty durable. I even constricted one in a cutoff turkey baster tube and flew a Tee Dee pretty well under fairly low pressure.

Okay, another one of my projects posted. By George, I've re-invented the wheel! I'm sure I'm not the first to do it almost exactly this way.

Beware, I have yet to perform a flying performance test, so don't run out and copy this quite yet. It could turn out to be a piece of crap. But I'm confident enough to go ahead and post this report. If it needs tweaking, I'll append it. This weekend is looking good for two days of flying. It's about time for me to get my flying legs working.

And that's all I have to say about that.(Forrest Gump)
Rusty



Last edited by RknRusty on Fri Mar 30, 2012 8:46 pm; edited 2 times in total

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Post  John Goddard Fri Mar 30, 2012 10:49 am

We're liking that Rusty.
Very Happy
I think I see some of Young Hanks products in there and now I've finally realised all my
TD woes have been head gasket (or rather lack of them) related (DOH!) I can't wait to try
that out.
Won't be just yet though as neighbour gave me a (051 provoked) hard stare yesterday,,,,,
ooops
lol!
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Post  RknRusty Fri Mar 30, 2012 11:20 am

John Goddard wrote:We're liking that Rusty.
Very Happy
I think I see some of Young Hanks products in there and now I've finally realised all my
TD woes have been head gasket (or rather lack of them) related (DOH!) I can't wait to try
that out.
Won't be just yet though as neighbour gave me a (051 provoked) hard stare yesterday,,,,,
ooops
lol!
Glad you approve, John. I need to tidy up my mounting method, but it's ready for a trial as it is now.
Hope your finger feels better.
I run 3 gaskets in my .051 with 35% nitro. And I don't bother to remove one if I use an occasional tank of 25%. It's a scary fast engine, especially scary the first time I saw the nylon prop flexing back and forth while adjusting the needle. Watch those knuckles!

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Post  PV Pilot Fri Mar 30, 2012 11:50 am

I wonder if you could use a spring loaded clothesline clip, to allow just a bit of fuel to sneak thru the line to get it started without flooding. Some quick way to release ALL the pressure right as it fires. That seems to be the major hurdle in getting a constant pressure system started correctly, otherwise you instantly flood and hydrolock.

One of my Norvel's has backplate pressure, and it will instantly flood if it dies,,fuel pouring out of the carb area. I either pinch the pressure side or fuel side, which ever is closer and the quickest and it cuts the flow, usually.
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Post  RknRusty Fri Mar 30, 2012 12:56 pm

I tried a clothespin the other day on my pressurized bladder and it kept slipping off. Maybe I need to try a new one. But this balloon has no pressure except for gravity, all you have to do is tip the nose up to stop the flow. Just not so much you start drawing air back into the line. Be sure and relieve any pressure before feeding it to the engine. You just have to figure out what angle to hold your plane to get the right amount of feed for starting. I got lucky and my stooge holds it in the perfect position.

Everybody has a routine that works best for them. I get a little fumble fingered when everything gets slick with oil. They make medical clips that hang on the line and are easy to use, and you can't drop them.
Once I launched my Stuntman with the pressure bladder only to look up and see a pair of hemostats flapping the wind. I had forgotten to take them off of my air purge tube. Of course I had an audience that day.

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Post  RknRusty Fri Mar 30, 2012 1:14 pm

Keep in mind, this balloon is strictly zero pressure other than gravity. It has no need for a fine thread NV either. Do not use a bored venturi because it has to have engine vacuum to pull the fuel in.

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Post  PV Pilot Fri Mar 30, 2012 1:38 pm

Ahh, ok. I thought it was a pressure system.

Even with the small hassle of flooding if not careful or fast, backplate pressure sure sems to wake up a Norvel and make it alot more responsive to needle changes. 1 needle click, 2,,3. and it is a vast change from rich to lean and peaking rpms. a very fine pointed and smooth surfaced needle.

I took a peek under the microscope at that needle and it is machined very well.
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Post  RknRusty Fri Mar 30, 2012 2:59 pm

Some people have put a balloon setup like mine inside another balloon and run CC pressure to the outside balloon to compress it.

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Post  nitroairplane Fri Mar 30, 2012 3:01 pm

RknRusty wrote:Some people have put a balloon setup like mine inside another balloon and run CC pressure to the outside balloon to compress it.
That is cool!
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Post  RknRusty Fri Mar 30, 2012 3:10 pm

PV Pilot wrote:Ahh, ok. I thought it was a pressure system.

Even with the small hassle of flooding if not careful or fast, backplate pressure sure seems to wake up a Norvel and make it alot more responsive to needle changes.
Definitely for the highest power and smoothest performance, use a pressure system. I use the Texas Timers equipment on the TDs, though I have run them on this type too, and it ran okay. Better than a wedge tank.

This balloon system is good and reliable for just fun flying, and safer too. No safety glasses are needed and no bladder explosions, etc. I consider it a step up in performance from the wedge.

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Post  RknRusty Fri Mar 30, 2012 7:20 pm

This needs to be done to the pickup tube outlet end
Balloon Bladder, ver. 2.0... yes, another project Bladderpckuptube
Next time I change the balloon, I'm going to replace the black rubber plunger with a slice of a wine cork. The plunger works fine and holds everything in place nicely, but I don't want it to deteriorate and pollute the glowplug. Some people report having trouble with syringe plungers decomposing.

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Post  stevej Sun Apr 01, 2012 12:08 pm

Jim Walker developed balloon tanks for the Firebaby in 1947.
http://www.americanjuniorclassics.com/firebaby/firebabyhistory-1.htm
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