MJD

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I figure it's high bloody time to get down to it and build something for my big pulsejet. Now, the reed valve looks a bit like a prop, is that okay?

I'd get ejected from the jet forum for this, besides you guys are more fun.

The nose section is easy, nothing more than a glass nose cone and tubing I have in my rocket collection already. Not really a big build now that I think about it. Wings are foam core, 1/64ply skin with some strategic composite reinforcement within, and with 2" thick refractory brick under the motor. Well not really.

This is not a kit prototype or anything, so has to fit between the cracks. But everything has a beginning, and I am happy with the design layout now, it took one pot of tea and a bowl of Red River Cereal to finish the basic details. I am probably gonna mold a pair of glass cells to fit 1l IV bags, to satisfy the rule about rigid fuel cells. Like it makes any difference when you smack the ground at 230mph, but rules are rules. It needs about 1200cc of fuel for startup and 3 minutes of flight.

Should be fun. Gotta hit someone up to make me a pair of mounts, the rest I can do.

MJD

soarrich

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There was a German guy on YouTube a couple of years ago with a plane that looked like this. He used a catapult start off the ground, the thing did about 250 mph if I remember correctly.

MJD

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They are all over Youtube, just type pulsejet in the search box and you'll find a bunch. Esp "450 kph delta"

[link=http://pulsejet.amtjets.com/index1.html]Team Helmond pulsejets[/link]

is where the basis for this design came from, look at the KB-70 there.

As noted, this is scaled by 0.95. My pulsejet is nominally rated at 15 pounds / 67 Newtons, but will provide up to 18 pounds / 80N if you don't mind climbing up a steeper part of the specific fuel consumption curve. So I reduced the size a hair to compensate, I didn't want it to be underpowered. The motor itself weighs only about 900 grams, 2 lb, and I think I can get this airframe to the 7-8 pound mark if careful.

Gear on board would be: Rx, 2100 mAh 3s LiPo plus ESC to drive the fuel pump, big NiCad pack to power servos, honking big elevon servos, and a fuel pump. Plus ear plugs and a Gravol dispenser for the pilot. And the Reitschcam in the cockpit to record the mayhem.

MJD

Bundubasher

MJD, see this site - it includes a pic of a launcher
http://www.airtoi.com/pulse.htm

I think they have the plane you have plans for.

Another site : http://www.aardvark.co.nz/pjet/
WHere the guy uses a Bobcat with wheels so no launcher ordolly required.

I roughly estimate my pulse jet to be around 14 lb thrust

soarrich

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I can understand how you guys in the bush can get away flying these noise makers, but how can he get away with it in Europe?

MJD

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That site belongs to someone that is either part of their group or associated with them I am pretty sure. There's probably not a pulsejet site in the world I haven't bookmarked over the last 5 years. There aren't that many actually, a quick Google will find tha vast majority. The KB-70 is one of several designs that are all variations on the same theme sized to the motor being used - a big delta with IV bags in the wing for fuel, twin fins outside of the pulsejet, and a nose section. Much like Diamond Dusts and Demons are almost the same but they are not the same. Because the specs of the Team Helmond pulsejet and mine are either the same or mine is a hair less powerful, I reduced it to 95%. The fuel consumption rate on mine is lower, so I decided I could thin the wing a hair and still get 1.2-1.3l fuel capacity from the two 1L bags. So with the size reduction and slightly thinned wing, it should move along just fine. Faster than any prop jobbie I've been flying or am planning to fly, that's for sure.

For some of the creme de le creme of model pulsejet weork, find coverage of the early to mid '80's QSAA rallies when Jorg Vogelsang was on his big pulsejet safari. The Me-163's, V-1, Me-328 (right number..?). He built a few extremely large valved pulsejets, about 50# thrust, and some smaller units. His motor designed and field mechanic was a German pulsejet guru named Heinz Ollarius - not sure of the last name spelling. His Me-163's had in air restart capability courtesy of onboard HV ignition. High wing loadings all, no mamby-pamby floaters in his fleet. He said he ended up installing a drag chute on the V-1 to slow it down as he got low over the landing zone. Having done the basic math on my Fi103R design, I can understand how the wing loading would be way up there, there is little wing to work with. Whatever the pulsejet weighs, you automatically need about 1.5 times that in the tip of the nose to compensate for the CG offset. The full scale V-1 was so tail heavy they ended up putting 1800pounds of high explosive in the nose just to balance it..

MJD

MJD

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Here's the Team Helmond group flying on of those KB-70's, check it out: [link=http://www.youtube.com/watch?v=JrbP2C7Hg5w&feature=PlayList&p=6BB4D6E77EF496B2&index=3]Team Helmond flight demo[/link]

combatpigg

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Those guys make it look easy. That launcher is pretty slick, too.

MJD

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They spend more on a field bench than some of us spend on the hobby in two years.

If you find the right videos you'll see some of them not having a good day too.

MJD

mk1spitfire

[youtube]http://www.youtube.com/watch?v=WymNgZXLsRs&feature=related[/youtube]


[youtube]http://www.youtube.com/watch?v=kzeI33TebSw&NR=1[/youtube]

MJD

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The Sagittario might be the only conventional-looking aircraft ever actually designed to accomodate pulsejet power and offered as a kit. I'm not sure, but wasn't it first designed to fit the Zanin pulsejets? I could be wrong, but I thought the turbine version came afterwards. In any case, it is a nice configuration and more pleasing to the eye than the standard bolt-a-pulsejet-to-the-top-of-a-delta fare. Mind you those do work really well, no wonder there are so many.

MJD

Bundubasher

MJD,
I found this link - it is in the Netherlands somewhere - about the fastest PJ I've come across sofar. I can see now why the turbine jet jocks mayfeel a little , shall we say..... nervous......?.....

http://www.rcgroups.com/forums/showthread.php?t=587022



I'll have to do some bench runs first to optimize the PJ setup and then size the plane around it.

MJD

My Feedback: (1)

[link=http://www.youtube.com/watch?v=fELbIozXyGI]Fast delta[/link]

This is about it for these things, the highest clocked speeds I've heard of are 440-450kph.

[sm=bananahead.gif]

I tend to think having an RC assist old timer in the pits might be good stress therapy between flights.

BTW Bundu: if you download this, you can use the Excel "goal seek" tool to back calculate performance with a moderate degree of accuracy. IOW seek a goal equal to your tailpipe diameter and look at the performance entry requried to get it. You can then iterate and make estimated guesses. Or just run it, but this is fun anyhow. [link=http://www.beck-technologies.com/pjetcalc.html]Pulsejet Calculator from Beck Technologies[/link]

MJD

Bundubasher

Thanks MJD, handy info.

mk1spitfire

Yer mike not too many kits with intregral pulsejets.

Mike I keep looking out for you at the winter olympics Rc speed flight competition!

Theres a starfighter here.(enclosed), not enough thrust for vertical rotation.
[youtube]http://www.youtube.com/watch?v=LrJaemuD-yE&feature=related[/youtube]

and different model, the salamander.External

[youtube]http://www.youtube.com/watch?v=3ScVuXyuj28&feature=related[/youtube]

MJD

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The poor Czech women's hockey team needed a boost of some kind.. 18-0 yesterday against the Canucks. I wonder if there is a gender test before the games?

MJD