MJD

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Got a toy in a big box from Germany last Tuesday. Hardly a prop plane but I tried, see the last pic. Thought you speed heads might get a kick out of it though.

Virus not-quite-ARF all composite delta for pulsejet or turbine. Has 2 x 1 litre built in fuel tanks, and a pair of Graupner 707 elevon servos pre-installed. Mine is a "second" that had a number of surface flaws, but I got those filled and sanded out over the last few days. Cut out the hatch today, now downstairs to make the rails for the hatch, next is trim out the bottom of the vertical fins to clear the elevon linkages, then epoxy those on, fill/sand the junction, then time for prime and paint. Not much to it. Fuel system is a 6v turbine pump, with ESC to control fuel flow between off, lean and rich. Dry weight maybe 8-9 pounds, 14-15lb thrust.

Here's someone else's: https://www.youtube.com/watch?v=6RmEtfQ81zA

Just need some heavy bungee, and hearing protection..

Kmot

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Gnarly!

aspeed

Make sure the little Co2 motor isn't on the back end of the other one.

airraptor

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man I want one of those. Sound so awesome

MJD

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Needs a small bullet cam, but I suppose I could box in a GoPro on the front of the top hatch.. hmm.

I think two weeks out is a fair guess. I blended in the hatch by wrapping its edges with packing tape (= excellent epoxy release), screwing it down then buttering epoxy fairing compound into the crack. Popped it out today, a qick touch up and the hatch line is down to a whisker. Next job is bonding on the vertical stabs, after hollowing the bottom to clear the linkages. After that not much before the paint room!

Oh joy, just got my order from KlassKote in the mailbox .. time to obsess over paint patterns.. got metallic green, metallic charcoal, white/red/black/blue.. hmm. Needs some neon too, likely the tips or verticals, for that I'll use some acrylic or just enamel and overshoot with gloss clear epoxy.

One feature is brilliantly simple and solid - inside is a (I think) 3mm steel rod running the length of the airframe - the front end is bent into the launch hook, and the rear end is formed into a horizontal loop embedded in the TE - for mounting the rear of the pulsejet and the launch restraint. So the force from the bungee bypasses the airframe until launch.

Major distraction from other lingering projects... sigh.. no attention span. But c'mon, this takes priority!

MJD

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OMG I ran the pulsejet yesterday. Yeehah! It is pretty impressive, one of those things where video just doesn't cut it.. behind the engine, it hammers your chest and blows **** everywhere, it's great!

Took a bit of fiddling to get the throttle curve set where it needed to be, I never did an injector flow test but just figured I'd sort it out on the test stand. You should see this thing suck fuel - on a rich mixture it's eating somewhere around 400cc/minute, I can watch the level dropping in the 500cc fuel tank on the stand. I haven't made my tailpipe spark probe yet, so we lit it with a blowtorch across the tailpipe. It works, but you need a fine touch on the fuel flow and air to kick it into resonance. After a couple of starts it was routine. I flooded it totally a couple of times, shut off the fuel and blew air through it and watched it spout fire like an oil well for a while. Cooling the engine with the leaf blower was perfect - the heat soak never got to the valves, they were a-ok afterwards.

A howling OPS .65 is pretty impressive, but this is off the scale. Gee, no pressure on the first flight.. with this thing thundering away and everyone waiting for you to look like you know what you're doing .

Pond Skipper

This is kewl for chur.

I have seen these in vids, do you have throttle of any kind with your set up? I would like a micro size one to help keep the noise down at my local field some thing that could fly a 15 to 20 oz plane.

aspeed

If you want to keep the noise down, this is definitely not the way to go, no throttle as they are hard enough to keep going. I used to let go of one when I was a kid, and as soon as it would fire up, everyone would hide behind their cars. Really. You may try a rocket or Jetex for something small. There may be something at a fireworks store, like a big bottle rocket or something that may last a bit longer?

MJD

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Sounds like a job for an EDF or a Kolibri turbine unfortunately (still too big).

Here's a park flier pulsejet: https://www.youtube.com/watch?v=tlkkgdFGfKs

Evidently not a lot of thrust, but quite kewl.

MJD

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No throttle, some minor thrust control via fuel flow/mixture is all. Fire it up, pull the release, and hang on.. until you shut it off or it runs out of fuel.

MJD

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This looks like it might be fun.



Having run the engine and sledgehammered that image into my mind, putting the two together gives me the willies. Pull the pin and hang on for dear life.. with my left hand quivering over the stop lever..

The keen eyed (?) might have noticed the two gaping holes in the wing, Shame that. I was curious about the amount of mechanical slop in the servos.. more than a clevis hole diameter, clack clack clack. I was under the impression it had Grauner 707 servos, but when I peered in with a flashlight (the elevon servos are built into the wing, very securely I might add) I discovered they were Hitec HS645MG's. I had some troubles with their kindred 625's in my prototype Demon.. two didn't move at the same rate, like mixing aileron with elevator for moment. But mostly the slop had me PO'ed, so I marked out a 70mm hatch and out with the Dremel and diamond cutoff wheel, with a roughly 45 degree bevel cut so it will be easy to rebuild. But ouch. Lots of grinding and prying to get the servos off, they were very well stuck down with a tough filled epoxy.

I must confess the servos did not survive the procedure.. victims of aggressive bonding and short patience due to having to remove them in the first place vie the top of the wing that only a short while ago I was wet sanding. Oh well. The screwdriver punching through the amplifier board was the first sign things weren't going smoothly. After that it was no holds barred, they're toast, Gonna get some nice tight, strong HV servos and run a separate pack for the servos, and the Rx off the speed control BEC. No reason not to, the pump is just a can 300 motor running at about 40% speed, and I'll use a 1800 mAh pack on each.

MJD

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I didn't actually mean to upload those higher res attachments, I tried to cancel it and upload the smaller versions, but I had some difficulty. They pictures aren't good enough for that.

Pond Skipper

There is a micro pulse jet engine running on a bench test vid - could work with anything under 8oz all up flying weight / was about 7in long.. sounded odd being so small.

aspeed

https://www.youtube.com/watch?v=zn4YVYdp8lE Is that it? I don't think I quite understand its operation, but it looks cool.

Pond Skipper

I have seen that one. The lil one I saw had a small vintage type RC gas engine spark plug to keep it running and a fuel tank and a throttle / fuel valve controlled the thrust. They are simple valveless pulse jet vs shutter type vs (reed) type like whats here in this build thread.

https://www.youtube.com/watch?v=cFK2B6txOL8

vent/shutter type

https://www.youtube.com/watch?v=QY308O42Ur4

Pond Skipper

https://www.youtube.com/watch?v=aQuToSKaLzk

how pulsejet engines works

https://www.youtube.com/watch?v=p8FSa5peEUk

https://www.youtube.com/watch?v=jEnNMTMZadw

How to make a pulse jet engine for a RC plane

https://www.youtube.com/watch?v=obFnt5KKrVc

Having a reed valve up front allows more air intake and during combustion the valve closes maximizes thrust is really the way to go. The vent or shutter type open up even more air intake increasing the volume to allow agressive fuel burn for max thrust within the realm of these types of jet engines.

MJD

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Here's a parkflier pulsejet..

https://www.youtube.com/watch?v=tlkkgdFGfKs

Gotta be all of 3-4 oz thrust, but cool nonetheless;

MJD

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http://youtu.be/yW_85lMnPxo

These two ( the cameraman and blower wielder..) were feeling the effects of a few hours of BBQ and socializing, they made a shaky but determined ground crew. I think my igniter battery might have been failing, spark was okay outside the engine but never got a pop on spark. So blow torch ignition instead.
It's loud. Check out the flameout then restart about a minute into the run.

Pond Skipper

Do you have a feel of consumption I know these pulse jets can be thirsty. Any idea how many oz you will need for a 5 min run?

Pond Skipper

I like the noise level of the park flyer engine too bad no solid run yet on video.

MJD

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About 350cc per minute I think, a bit more if you go heavy on the fuel flow. That's a 500ml jar. Guys are getting near 5 minute flights with a pair of 1 litre tanks on the YT videos. There are no specs with the engine.

MJD

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Shot the first coat of primer this afternoon. Finally! Ordered a 50ft length of 3/4" OD 1/8" wall latex tubing for the launcher, seems about right - 50lb pull at 300%, 60lb at 400%, so 4.5-5g at release.

MJD

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https://www.youtube.com/watch?v=4tIJE3dm0ys

As the paint cures.. may as well fool around with the engine. Here I get it started in 1:14, I'll go for 30 seconds next time..

arcticflyer

Luv it! That plane oozes speed just sitting there at zero

Here is a pic of mine. I am in the process of building a Bruce Thorpe Delta Vortex and will be mounting (2) YES TWO of the HK pulse jets to it. Will be following your build with great interest!

Hope you got my reply to the PM...if not let me know!

MJD

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Sure did! Got back Thursday evening from a week of trade shows and meetings, all done, back to more important matters, Went in yesterday to shoot the charcoal underside but (a) forgot the A side and (b) the heat was off and the whole place was at about 40F. But got some masking done. Another week of evening fiddling I guess.

Got my HK unit mounted to a plank today - call it a test bench if you will - with some room ahead to fiddle with fuel systems. The pressure bladder/Cline regulator system is known and works, I'm looking forward to tinkering with some alternatives. 10 spare reeds for next to nothing.. why not?