Old pulse jet engine ???

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gone2fly
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Old pulse jet engine ???

Post by gone2fly » Wed Sep 23, 2009 8:03 pm

Check out his pictures. I know someone that found one of these engines in a box of junk and is asking questions about it.

I saw one of these engines on this forum yesterday with pictures with a box but I can not find it anymore. Does anyone know where to find the thread about this engine.

http://www.clstunt.com/htdocs/dc/user_files/34670.jpg

vturbine
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Re: Old pulse jet engine ???

Post by vturbine » Thu Sep 24, 2009 12:14 am

Hi Gone2fly, it was in the thread you first started.... I'm afraid we got a little off topic in our enthusiasm!

viewtopic.php?f=2&t=5500&start=0
No problem is too small or trivial if we can really do something about it.

Richard Feynman

vturbine
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Re: Old pulse jet engine ???

Post by vturbine » Thu Sep 24, 2009 12:34 am

Good photo, we now see the plug penetrates the aluminum(?) collar. It makes me wonder if it is aluminum because that has to be a hot area, however, probably the stainless tube is fit inside, and heat transfer is slow enough not to exceed the aluminum's yield point. Also we see the backside of the carb not sure what the dark ring to the right is.

It sure would be great if we could get a shot of the valves from this owner.

You say check out his pictures -- are there others than that one?


EDIT: okay, tracked it down, here it is:

http://stunthanger.com/smf/index.php?to ... .msg127832

Mark?

Check out that valve!

They said RCM reviewed it and panned it because they couldn't start it (reminds me of my own engines). Apparently they tried white gas and when it was finally flooded and leaking out the tailpipe, had a fire.

Some puzzlers:

1.) The spark plug location in the box illustration is different than the one on the physical engine in the above url, and different than the one pictured earlier. One has the plug in the aluminum head collar, the other far down the tailpipe.

2.) A glowplug is shown, not a spark plug, and has the coil expanded and pulled outwards. If a glow plug was used, wouldn't the appropriate fuel be methanol instead of white gas? Was RCM using the wrong fuel?

3.) Are there two different versions of these engines -- one with a spark plug, and one with a glow plug, designed to use different fuels?

4.) I'd love to see webpilot analyze that valve!

2nd EDIT:

Okay, here's more information:

viewtopic.php?f=2&t=2019

No problem is too small or trivial if we can really do something about it.

Richard Feynman

vturbine
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Re: Old pulse jet engine ???

Post by vturbine » Thu Sep 24, 2009 2:46 am

I noticed that there was a Laird drawing mentioned, but I couldn't locate one anywhere on the Internet.

However :D Amaaaaaaaaaazingly, I did find on my old hard drive a copy of the P-80 Instructions! Copied from a website years ago, for what reason I don't even know. I have a tendency to grab info and store it, often without reading it, if it looks interesting.

No mention of what the fuel is supposed to be, by the way -- it just refers to "fuel". Really interesting description o the variable inlet length. No mention of the screen.

Anyway, here it is, formatted to fit a little better:
p-80Instructions.png
No problem is too small or trivial if we can really do something about it.

Richard Feynman

Mark
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Re: Old pulse jet engine ???

Post by Mark » Thu Sep 24, 2009 3:37 am

A few things that I would do is go with methanol rather than white gas and use a 1/4 32 inch spark plug which will fit the same threading as that glow plug. I bought a half dozen small spark plugs and a matching 1/4 32 tap so that I could tap my 1 inch plumbing pipe with it when I was toying with the straight motif. Methanol is so much less fussy than gasoline. And a hot spark plug is much more forgiving than a glow plug.
I used a fine brass screen in my intake in order to break up any large droplets of fuel before being ingested through the reed valve, hoping that that would help.
I must say it is hard to get a good starting impulse for straight pipes of small size using ordinary fuels; I've been there. It's kind of like lighting a jam jar without the lid, barely a weak woof/no confinement. So that's why I took to corking and rubber stoppering the tail and then sparking the fuel/air mixture. Again, I had a poorly designed fuel feed system and crude reed valve which only bought me about five seconds of running before it would flame-out or slowly just lose steam after a zesty few seconds of seemingly steady pulsejet action. Nothing like being teased. ha
Maybe my fuel flow was unsteady or maybe the "large" reed valve I made was fussy and inconsistent in motion because of my warped retainer/reed stop that I adjusted endlessly. Straight ducts seem to be very fragile, at least when they are so small and using ordinary fuels.

Here's some info on the Kavan carb.
http://www.mecoa.com/faq/carb/kavan/index.htm
Presentation is Everything

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Re: Old pulse jet engine ???

Post by Mark » Fri Sep 25, 2009 1:24 am

After reading Jerry's description of this valve which has a 9/16 inch petal reed/disk suspended in the center of the maze-like spider spokes, I was wondering if anyone had a name for this type of valve or what company might make it? It's funny, it's almost an optical illusion the way the maze at first just looks like a bunch of zigzag curved segments with nothing in the center.
What other use might this reed have had other than in the P-80 Jet-Stick? Something very delicate I suppose. ha
Might it too have been used on some make of piston engine to regulate air and/or fuel flow, as other parts of the head of the P-80 seem to be Frankensteined from model engine parts? Could it be a Kavan part?
Attachments
jet3.JPG
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Re: Old pulse jet engine ???

Post by Mark » Fri Sep 25, 2009 11:47 pm

Here's kind of the same philosophy in that P-80 Jet-Stick reed valve design. It occurred to me it might be like a compressor reed, at least it has some similarity to it anyway. I guess a small one could be driven at a fairly high frequency if it has but a small amount of play.
Scroll down the page a bit.
http://www.china-pump-manufacturers.com ... ve-61.html
http://www.china-pump-manufacturers.com ... e-c25.html
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vturbine
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Re: Old pulse jet engine ???

Post by vturbine » Mon Sep 28, 2009 1:25 am

P-82 literature.
(click twice for higher resolution view)
p-82.png
Looks like there's an annular slit between the intake cone and the engine CC ala Reynst?
p-82-1.png
p-82-1.png (2.06 KiB) Viewed 9004 times
But why a set of fins in a valveless? and presumably in aluminum, since it looks very much like the valve head, on the p-80, not the same, but similar, with similar plug placement?

Curioser and curioser.....
No problem is too small or trivial if we can really do something about it.

Richard Feynman

vturbine
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Re: Old pulse jet engine ???

Post by vturbine » Mon Sep 28, 2009 2:25 am

More info:

viewtopic.php?f=2&t=2010

In that photo, I can't tell if there is a gap, and the head looks as shiny silver as the tube -- possibly a stainless turning? Expensive to produce, if so, as was that valve on the P-80.
Turbocraft_p82.jpg
That valve on the tank looks like brass, and the brass tab on it makes it look suspiciously like the air valves used on aquariums.
No problem is too small or trivial if we can really do something about it.

Richard Feynman

Mark
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Re: Old pulse jet engine ???

Post by Mark » Mon Sep 28, 2009 12:47 pm

Good eye there, it does look like an aquarium valve. Funny how this is yet another part borrowed/cobbled from things at hand rather than designed exclusively for these P series engines. Here's some aquarium valves I have, and I see the mounting flange looks similar to the one in the P-82 picture.
Attachments
060608194624[1].jpg
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vturbine
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Re: Old pulse jet engine ???

Post by vturbine » Tue Sep 29, 2009 9:20 pm

DynajetJerry, does your P-83 have an annular slit at the base of the inlet cone, or is that just a print artifact?

Do you think that the valve might be an aquarium valve, as Mark shows above?

Do you have any better pictures of the engine, especially the fuel valve, inlet, and CC details?

Thanks for your time! :D
No problem is too small or trivial if we can really do something about it.

Richard Feynman

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Re: Old pulse jet engine ???

Post by dynajetjerry » Wed Sep 30, 2009 9:25 pm

vturbine,
My Turbocraft P-82 differs a little from your illustration in that it has no flared discharge. (Note that the cone is, almost certainly,) the engine's exhaust outlet, not its intake. As I said in my 2005 comments, I think the whole design is questionable; I'll add that it is probably dangerous for anyone to try to operate one with pressurized fuel, whether acetylene or propane. I'd recommend that an experimenter try some other, proven concept and avoid what appears to be blind alleys.
I have no pictures that are usable for copying my P-82 version. However, you are welcome to contact Don Laird to see what drawings he can supply. Again, I advise against trying any Turbocraft designs because they may be dangerous as well as of limited (or non-existent) usefulness.
Jerry
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vturbine
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Re: Old pulse jet engine ???

Post by vturbine » Wed Sep 30, 2009 9:57 pm

Thank you Jerry. No I wasn't planning on acquiring one and trying it out :D . I imagine it's worth more in mint condition than ignited, and far more valuable now than when it was made. Probably more valuable than my old pickup truck. I also know acetylene is NOT something I would want to transfer into any container, except perhaps my welding torch.

No, I'm really much more interested in the engine than the tank. I'm surprised to hear that the cone is the outlet -- since in the photo it looks like the fuel line leads there. But the photo is pretty hard to read. It's also amazing that the inlet/cc straight tube -- however you distinguish the two, is so much longer than the outlet.

So, questions again, where does the fuel enter the inlet and how? It looks like there is some tubing in the photo. Does yours have tubing? Is the non-cone end open or closed (like an odd Reynst)?
No problem is too small or trivial if we can really do something about it.

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Re: Old pulse jet engine ???

Post by dynajetjerry » Thu Oct 01, 2009 3:57 pm

vturbine,
I've not examined the engine for many years but can recall a few details. The two main parts are fastened together for operation, therefore requiring no external plumbing. The tank has a recharging fitting in one end and six brass discharge nozzles in the other. A crude needle valve "controls" the rate of flow of the pressurized fuel through the nozzles. The "engine" is fastened to the tank assembly, behind it and in line so that the nozzles are aligned with six entry ports in one end of the engine but at a slight distance from them. This allows the jets of fuel to induce a flow of air to enter the ports, mix with the fuel, and be ignited by the glow/spark plug downstream of the ports. In theory, the burning mix expands, is discharged from the engine, and develops useable thrust, the amount depending on the rate at which the fuel is discharged and, of course, the temperature of the fire.
It is possible the acoustics of the system causes a pulsating generation of thrust and, thereby, to qualify as a kind of pulse-jet but this is not obvious. The P-82 is really a pressure jet that is, almost certainly, extremely inefficient. With a total weight of about 1/2 lb., its power would be very likely be much less than its weight (it it functioned at all.)
Jerry
Louder is always better.

vturbine
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Re: Old pulse jet engine ???

Post by vturbine » Thu Oct 01, 2009 6:42 pm

Fascinating.

The cone, therefore, if indeed there is a gap, may actually be an augmenter of sorts, if air is induced there. The advertising page printed above calls the p-82 an "auto-pulse" engine, so pulsation must have occurred during running, unless this is just an arbitrary falsehood. Since pulsation is not necessarily an advertising advantage, it's hard to imagine promoting it unless there was some actual acoustical effect in tests. On the other hand, it's hard to understand just what part is the inlet, the CC, or the tailpipe from an acoustical pulsejet point of view. I guess it depends on where the burn is occurring.

From your description, it seems like at least a prototype would have been "lit" -- whether it was simply acting as a blowtorch or not would be the question. But nozzles injecting into air and with a source of ignition downstream would at least have produced a weed burner. Of course the lack of safety of the tank and valve is the most glaring reason not to try it today.

But it doesn't seem to be an engine that couldn't be "started" unless pulsing was required. As a pressure jet, it seems like it would work, it just may not produce much thrust. The advertising copy said 3 to 6lbs of thrust. That's difficult to imagine.

I would love to build a copy of this thing, without the real tank -- just a short open dummy tank as a holder for nozzles actually piped to an ordinary 20 lb propane tank with a proper control valve for stationary tests. It would be great to put to rest the speculations, one way or another.

Did you say Mr. Laird had drawings of this one? Or was it the P-80 valved job?
No problem is too small or trivial if we can really do something about it.

Richard Feynman

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