Tiny pulsejet, oh so small

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larry cottrill
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Post by larry cottrill » Mon Aug 02, 2004 3:45 pm

Mark wrote:I found some needle valve on eBay that looked similar to the 6.5 inch pulsejet needle valve, do any of you know if this might be about the same kind or what kind was it exactly if you know?

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... :X:ON:US:2

Mark
Mark -

Probably not the same, but certainly similar -- the one in the little jet may even be made to fit the Norvel engines. In my opinion, though, it isn't worth buying just the needle for our purposes; you want the whole brass assembly, which is known as the 'spray bar'. In my early attempts at tiny engines, I always bought the Norvel spray bar assembly, with the long extension shown. I drilled the fuel port out a little, for increased flow.

These are Russian made parts, and have a very fine metric thread, naturally. Very nicely made pieces, and inexpensive for an import.

L Cottrill

Mark
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Post by Mark » Mon Aug 02, 2004 6:12 pm

I once bought a couple of Norvel needle valves recommended for the Craft pulsejet design. They are small but I would like a long skinny spray bar that I would only have a very small signature in the intake.
Mark
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Mark
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Post by Mark » Mon Aug 02, 2004 6:15 pm

Here's another angle, note it is set off-center.
Mark
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Tom
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Post by Tom » Mon Aug 02, 2004 6:17 pm

Now thats puuurdy.

Tom
Experience speaks more then hypothesizing ever can. More-so in chemistry.

Mark
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Post by Mark » Mon Aug 02, 2004 8:11 pm

Might as well post the plans that came zipped with the pics.
Mark
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Mike Everman
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Post by Mike Everman » Mon Aug 02, 2004 10:23 pm

Here is the response from the fellow that bought the tiny Jet:

"Mike, Nobody is as anxious to see if this small pulsejet works as I am! I was surprised (and disappointed) to see how expensive it got. One of my students, Rob Ordon, has been actively participating in your forum (he brought the auction item to my attention) and he will report on our progress."

We should be hearing soon.
Mike
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Bruno Ogorelec
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Post by Bruno Ogorelec » Tue Aug 03, 2004 7:57 am

Good to see the thing end up in 'proper' hands.

Stephen H
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Post by Stephen H » Tue Aug 03, 2004 10:08 am

1 1/2 years ago i got those two above pictures plus another one (below) sent to me by bruno. i just thought i'd post the other picture to compare sizes!
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Mark
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Post by Mark » Tue Aug 03, 2004 1:43 pm

Mike Everman wrote:Here is the response from the fellow that bought the tiny Jet:

"Mike, Nobody is as anxious to see if this small pulsejet works as I am! I was surprised (and disappointed) to see how expensive it got. One of my students, Rob Ordon, has been actively participating in your forum (he brought the auction item to my attention) and he will report on our progress."

We should be hearing soon.
I wonder how high he would have gone before yielding to a higher bidder? With all the pictures posted now, seems anyone could make one extrapolating from the design. Two things I didn't like, the sharp facets on the petal valve, it wasn't even rounded at the edges, just rough cut with snips it looks like. And the needle valve is a bit ostentatious, if I was a kid with a shirt pocket, I would want a shorter more proportionate needle. Oh, make that three things I didn't like, what the heck kind of a connection was that between the combustion chamber and the tailpipe? It looks like modeling clay work mushed to hold the tail pipe on. Nothing about this engine is glitzy, except the size.
Mark

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Post by steve » Tue Aug 03, 2004 6:20 pm

the needle valve could be cut short and operated just with the knob, and the weld and petal valve could be ground down without much trouble. kind of makes you wonder why the previous owner didn't do it. let's just say that if it runs I will be very surprised. (but if it dosn't it shouldn't be too dificult to lengthen the tailpipe)
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Mark
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Post by Mark » Tue Aug 03, 2004 8:28 pm

One thing I have found is that the aluminum head doesn't really seal air tight even if you have to walk it in or exert some effort. It will probably still leak even if close to perfectly round being that short too. I can't imagine it starting easily on Coleman fuel. Maybe if you heat it up. When the aluminum head gets hot from a running it expands more than the combustion chamber metal and after cooling will often leave it looser than when you first slid it into the combustion chamber, further worsening the fit.
These are some things I have had happen to me in trying to keep an air tight seal on a slip in head.
Mark

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Post by steve » Tue Aug 03, 2004 10:14 pm

I had the same thing happen on my valved engine. I tried to make it seal better by using the lathe to cut a groove around the perimeter and then cramming this full of steel wool. When I ran it the wool shriveled up/melted and was useless. If I could get some asbestos to put in the groove it would probably work but I don't think I can buy that anymore because it causes cancer. (then again, what dosn't)
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Post by Mark » Tue Aug 03, 2004 11:22 pm

Perhaps this stuff would work. When I made my 11 inch pulsejet I bought little gasket rings for kitchen sinks that cost about a dollar for a little ring, a tiny ring you could slip over your finger. But I needed this gasket ring to seal the 3/4 inch pipe combustion chamber to the head to get an air tight seal, essential when you need compression and feedback in a tiny engine. You can't afford any air leaks or else the engine isn't going to start, at least that is what I have found, the starting pressure wave just bleeds off when you go to start it if there is any leakage.
Mark

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Post by Mark » Fri Aug 06, 2004 1:24 pm

I thought I would like to try some experimenting with these little jam jar snorkelers about the same length as the 6.5 inch pulsejet. I was positing as you get shorter and shorter, enough backflow air could reach the combustion chamber in a very short amount of time.
With a fast burning fuel, you might be able to get a relatively stronger jam jam squidly action.
My chrome/brass syringe is 1.5 inches by 3.25 inches and it runs feverishly for a jam jar.
If you look carefully, a couple of these glass vials have double necks. Maybe with some side porting they would work as little Logans.
Just some ideas I'm toying with.
Mark

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Last edited by Mark on Fri Aug 06, 2004 3:03 pm, edited 1 time in total.

Mark
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Re: Tiny pulsejet, oh so small

Post by Mark » Wed Oct 06, 2004 3:20 am

I wonder how the 6.5 inch pulsejet is coming along? I haven't heard from the guys who bought it, how about you Mike? Maybe we could needle/rib them, and ask what's the hold up, declare it only has one moving part, etc. Maybe we should rename it the US 325.00

http://cgi.aol.ebay.com/ws/ebayISAPI.dl ... otohosting

Mark

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