Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

Brainstorming: Demon + HK pulse jet

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Old 12-19-2015, 12:31 PM
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Rudeboy
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Default Brainstorming: Demon + HK pulse jet

So I finally got my hobbyking pulse jet working.
Natural reflex is to put on a Screaming Demon.

I have zero experience with flying pulse jets however.

So this is a brainstorming thread where everybody can chime in with thier ideas.

My main concern is fuel flow: this is a venturi fed engine, and it will be sensitive to fuel flow issues. Where do I put the tank? It needs half a litre of fuel at least I figure, so I have to take CG issues into account too. How will it react to G-forces? I have to put the tank below the fuel inlet or it will flood on the ground. Will it flame out in tight turns with the tank that low?


https://www.youtube.com/watch?v=Xn96GtNxJ7A
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Old 12-19-2015, 12:36 PM
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Back when I ran them, we used a uni-flow type of tank. As you get going, it would pressurize itself. The hard part is keeping it constant and no bubbles. The slightest bubble will shut the engine off. We also messed with different pills and spray bars. They can be very temperamental, but a lot of fun, once you get them dialed.
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Old 12-19-2015, 04:22 PM
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A air-trap tank like what we use on our turbines would seem to be called for here. Some guys have good luck using felt clunks, instead.
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Old 12-21-2015, 06:06 AM
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That's why I'm working on a regulated pump on mine. If you are burning gas then 8oz will get you by. The pumped pulsejets use clunk tanks and an air trap, or IV bags. Both work.

Small clunk tanks can be converted into air traps. Ditch the clunk, put fuel pick up center of the tank, one vent top corner, one vent bottom corner.

Last edited by MJD; 12-21-2015 at 06:08 AM.
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Old 12-21-2015, 06:52 AM
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Even with all of the radio gear and battery as far forward as it can go, a PJ powered Demon will be hopelessly tail-heavy. Adding a nose extension similar to the Vulcan bomber would allow battery and ballast to be stowed where it will do the most good. That would leave plenty of room for fuel, too.
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Old 12-21-2015, 07:32 AM
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That's what's on the drawing board. I already cut one fuselage, now I am lightening it up.
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Old 12-21-2015, 08:03 AM
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That added fuse/nose would have some advantages for E-power, too. Extend the motor far enough forward and now the battery can sit behind the front spar, not on top of it. Or, a pusher configuration becomes possible by placing the battery well forward in the nose. With E-power, the weight of the "fuel" never changes, so it doesn't need to be near the CG.
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Old 12-22-2015, 04:36 AM
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You guys think the "remote smoke valve" from Perry Pumps flows enough for a small pulse jet like the HK unit?
With a proper shut off I could probably place the tank centerline inline with the venturi of the engine.
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Old 12-30-2015, 09:58 PM
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modify the the fuel jet as on youtube vidios by chris lomas run on methanol pressure bladder and cline regulator
did this to mine 2 days ago works great
its goin on a cororoo spad delta cheap and dirty
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Old 12-31-2015, 11:32 AM
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That system is proven, yes.

I am experimenting with a simple and inexpensive-as-possible fuel delivery systems for naptha, and my goal is to fly a PJ Demon prototype with a stock HK engine versus on methanol and pressure bladders and other stuff, to make it more accessible and less mysterious to the average sport flier.
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