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Old Nov 27, 2011, 11:16 PM
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I finally tried a pressurized bladder tank

That no-pressure bladder I was working on last week is a dog in the air. Great in the shop and great for flying flat laps and a loop here and there. But worthless for any wild flying.

I made my first pressurized bladder today. I had some tube shaped balloons and I put one inside another for double thickness, and inserted the same perforated tube I used in the other bladder. I put that into a 1.5 ounce turkey baster syringe and mounted it to the underside of the Stuntman23 wing. It works perfect, best fuel feed I ever had with any engine and tank.
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I had always thought cranking a TD with a pressure feed was some fancy dance. Maybe it is for you guys that use higher pressure, but this was easy. With the NV closed I primed it through the venturi and spun it over to burn some but not all of it off. Then opened the needle a tweak at a time until it cranked, then kept riching it up until it held on. It ended up being happy at about 3 turns with the 128 TPI NVA.

I put a Top Flite 6x4 nylon prop to help chop through the wind and to keep it a little slow for the test flight. I sent it off and it never stutters or misses no matter what I do. It is just as happy upside down as right side up or any other position for as long as I want. In other words it works perfectly.

The only unfortunate thing was I balanced the plane with an empty tank. That was a very bad mistake. I felt like I was flying a wild pig with a mind of its own, plus it was a little windy, 15-20 mph. Next time I'll know better and balance it with a full tank. Probably should have used a 6x3 rubber ducky. Anyway, I flew a bunch of inverted laps and it drew fuel perfevtly. Unfortunately the pig did one perfect figure 9. So now I need to buy a new needle because mine is bent, and by bent, I mean FUBAR.

Does it matter what brand as long as it's 128 TPI? Maybe I can't buy just a needle by itself. Is Texas Timers the only source for fine thread NVAs? I can't seem to find any other. I don't know what my brand is, but I can find out, just have to ask fit90, he gave it to me. I thought I had it in a position so if I landed upside down it would just unscrew a little, but I kinda landed hard. No shame, I even posted it on YouTube.
Luckily I have other videos that prove I can actually fly a plane.
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Old Nov 28, 2011, 01:27 PM
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Surprised the no pressure balloon tank failed you. Too small a fuel line? Too small a balloon. Dunno.. somethings' weird, should of worked perfectly.
No matter.
USE thin wall surgical tubing for the Bladder. Use a Syringe to fill it/control amount injected a bulldog type clamp on the fuel line until it fires up on prime. USE a 5 x3 rubber ducky.... And 42' lines ... Tach revs to less than 25K in hand.
Gotta learn to avoid dorking as well. At least keep the NV less than break the plastic tight so it can rotate back.. when you bury it
KK needle assembly.... pretty near universal. Still sold, saw it listed just the other week (different 'name' same part), but most of my fave links are Dead. Can't find it just now.
Try that RJL twit?
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Old Nov 28, 2011, 01:42 PM
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Texas timers has some nice NV:
http://www.texastimers.com/
As well as parts to make pressure bladders:
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Old Nov 28, 2011, 05:26 PM
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Quote:
Originally Posted by Bare View Post
Surprised the no pressure balloon tank failed you. Too small a fuel line? Too small a balloon. Dunno.. somethings' weird, should of worked perfectly.
No matter.
USE thin wall surgical tubing for the Bladder. Use a Syringe to fill it/control amount injected a bulldog type clamp on the fuel line until it fires up on prime. USE a 5 x3 rubber ducky.... And 42' lines ... Tach revs to less than 25K in hand.
Gotta learn to avoid dorking as well. At least keep the NV less than break the plastic tight so it can rotate back.. when you bury it
KK needle assembly.... pretty near universal. Still sold, saw it listed just the other week (different 'name' same part), but most of my fave links are Dead. Can't find it just now.
Try that RJL twit?
The no pressure bladder worked great on the bench, but I didn't have it in a good container for its shape, letting it flop too much. It was round and I needed a tubular shaped balloon like the one I use for the pressure bladder, only bigger to hold enough fuel. I'll try it again for the Jumpin bean or the Li'l Satan with the Medallion.

I thought of leaving the NV loose enough to move back without bending, but I guess it was still to tight. Remember I mentioned before, that's my only fault, over tightening.

Dorking pisses me off to no end. I usually only do it when the engine unexpectedly cuts out. I think I finally have that solved. I should have balanced with a full tank, and shoulda not flown again hoping the balance would come back as I used up the fuel. Yada yada yada.

Got a new Texas Timers NVA ordered, $15 bucks. I'm going to build a new plane with the proper nose to mount a TD/Medallion.

I know it's not a Norvel, but I like my two new engines. Much better than fuel challenged 8cc Bees.
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Old Nov 28, 2011, 09:54 PM
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Alright I'm ready to fly now, I just bought a pair of short needles for $5 each from Texas Timers and enough stuff to kit up a couple of bladders. I did some good reading on the clcombat.info website. They have lots of good information.

Too bad I don't have a fine thread spraybar on the Medallion, but It can wait. I'll revisit the zero pressure bladder for it. I'll lay a balloon in the first outboard rib bay on the Bean. Or maybe a latex un-lubed condom instead of a balloon. I can't possibly ask my beautiful pharmacist if they sell small ones.
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Old Nov 28, 2011, 10:40 PM
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Cool. yeah I figured when you went with a bladder for the fuel tank, there would be no going back. You can run those engines on right up close to the peak RPMs with the bladder.
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Old Nov 28, 2011, 11:39 PM
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Mine is running on what I'm sure would be called low pressure with the balloon. Should I expect to see a difference in output with the higher pressure from the TT tubing?
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Old Nov 30, 2011, 04:36 PM
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It can be a little bit trickier to start the engine and get the fuel flowing. But basically you get to run it at or near peak RPMs the whole flight.
some guys were boring out the intake venturi a little more as the engine doesn't need to suck fuel from the tank anymore too. But forget now about how far they go doing it though.
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Old Nov 30, 2011, 05:46 PM
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The Cox TD .049/.051 instructions recommend 5/32" ventuty size when running pressure.
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Old Dec 01, 2011, 02:41 AM
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I have a bored venturi that was given to me along with the engine. I'll measure it in the morning. I know it's larger than the one that was on it, which also has a screen.

I hope my Texas Timers bladder kit comes in the next day or so. I just have to find a good way to mount it. If the plane had been built for a beam mount there would be more room. I'll probably hang it under the wing again and try to keep the fuel bulge as far forward as possible. My turkey baster idea was troublesome, balance-wise. I hope to avoid adding nose weight.

I did find a needle for it in an old red postage stamp backplate from my looong gone childhood Stuka. 128tpi. I had to clean 40 year old baseball field infield clay off of it.

I have the Medallion mounted on my Jumpin Bean. Do you think I could run a low pressure balloon on it with a stock NV? Or would it be impossible to set the needle?

You guys have been patient with my goofing around, I appreciate that.
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Old Dec 01, 2011, 07:27 AM
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I think you could run a low pressure balloon for the Medallion engine. They weren't all that great for setting the needle with a regular fuel tank anyway, so it ought to be about the same, maybe easier as the engine doesn't have to draw fuel.
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Old Dec 01, 2011, 10:02 AM
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Try Doug Galbreath for a super cool needle set up for your Medallion,http://www.the-printer.net/DookCat.html .The Medallion is used by the guys that fly nostalgia free flight. They use Doug's needle and open up the venturi with a bladder tank .He also has the head for the Nelson plugs. Any old piece of cardboard or plastic tube should make a holder for a bladder tank. Just cap the end with some balsa and strap it down.The bladder should fit loose in the holder or it will give a false needle set.

Mike1484
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Old Dec 01, 2011, 10:27 PM
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Mike, I've read about that. When I got my Medallion I spent a whole evening searching out information about it.
My TT needles and bladder kit was in the mail at 10 AM this morning. I combined the TT instructions with the Clstunt tutorials and I love it. I had no idea you only needed an inch of tube to make a bladder. My first one was bigger, but perfect for the Stuntman, and will hold 2 ounces. I put a check valve and a Luer-Lock adapter on its ass end so I can screw the syringe on and off without clamping while I fill it.

I have a question though. I bought some Tee fittings. I would like to put one between the tank and the business end of the bladder to make it easy to evacuate the air prior to filling. But the Tee has such small inside diameter I don't want to restrict fuel flow. But that won't matter will it? The engine will just ask for a little more needle, right?

EDIT: I mounted it on the Stuntman and put 40cc in it and the plane balances perfectly. No difference full or empty so it should fly fine this weekend. I put a wider venturi and a 5x3 prop on it and cranked it with 20cc. It ran for about 2:30 or so. That's how long a Black Widow runs on 8cc. Super easy to crank, easier than with vacuum feed. I just spun it giving the needle little tweaks and when it started, I spun the needle open until it kept running. I got it on about the third or fourth spin. The needle runs good at one place, it's really sensitive. But That's the fastest I ever heard one run other than on youtube. It never wavered and would have flown straight up if I had let go. One thing; I held the plane by the fuse behind the wing and the exhaust oil on my hand was gray. That bothered me, but all of the oil on the plane was clear pinkish, no gray on the plane except near the tail. I hope that sounds normal

I can't wait to give it another flight. I'll prop it down to a 6x3 for the next test flight and get it on video. I don't think I'll be slamming the ground this time since it's balanced right.
I need to make a spare bladder. I have enough fittings for one more. I'll buy a few more fittings, and it looks like I'll be needing more fuel too.
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Old Dec 08, 2011, 05:45 PM
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Im just curious .....

....., Rusty, have you tried drilling out the engine case under the venturi? You know, where Cox provided a plastic nipple for pressure?

I have, & it did work better than W/O pressure of any kind .....

Anyone may answer my question, its not just Rusty Im asking .....

Laramie.
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Old Dec 08, 2011, 06:41 PM
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Yes I had done that years ago when we were pylon racing Cox engines. But we wound up using the Kustom Kraftmanship pressure backplates as they were easier to use.

You have to use the small neoprene tubing as the silicon tubing tends to slip off the small plastic fitting. But the black neoprene tubing will sort of glue itself on after a while, so you do not pull it off or the little fitting will break off on you. What I did was use a short piece of neoprene tubing and then a joiner tube to the silicon fuel tubing.

It is tricky drilling out the hole, as you need to use a small high quality drill bit. You also should take the engine apart to do it. I would suggest using a drill press so you can keep the drill bit straight easier or you could break it off. Now if one is careful and locks the crankshaft so the intake port is open to the hole, they could drill the hole through OK, but it is wiser to pull the crankshaft out too.

You also should get one of the extra fine threaded needle valve assemblies as it makes adjusting the needle valve so much easier when you are using pressure or not using it for that matter.

Yes the engines run much better with pressure of any type. You don't have to worry about allowing the engine to run a little on the rich side, so that it runs OK as the fuel tank empties. You can run the engine on the hairy edge of max RPMs with pressure. So you get a performance boost that way.
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