Another pocket lockwood success

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Jmitchell
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Another pocket lockwood success

Post by Jmitchell » Sat Jun 17, 2006 2:53 am

I actually built this several months ago, but just finally got video of it.

http://media.putfile.com/k-47-30

Dang911
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re: Another pocket lockwood success

Post by Dang911 » Sat Jun 17, 2006 3:46 am

VERY NICE!! Looks like that had a nice kick to it. Great throttle range.... Any idea of the thrust? Also could you provide dimensions, I might just want to build that, for the times when I can't pull out my big lockwood.

Very impressed....
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Mark
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re: Another pocket lockwood success

Post by Mark » Sat Jun 17, 2006 2:38 pm

I wonder what the "mosquito-like" frequency is? Quite high pitched.
Mark
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James D
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re: Another pocket lockwood success

Post by James D » Sat Jun 17, 2006 3:03 pm

Nice.
The frequency is around 710 hz, What fuel are you using?

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re: Another pocket lockwood success

Post by Mark » Sat Jun 17, 2006 3:05 pm

What fuel was used? It looks like acetylene, the red-yellow glow at the very end of the run.
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kid jansen
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re: Another pocket lockwood success

Post by kid jansen » Sat Jun 17, 2006 3:29 pm

I've made a frequency analysis with Adobe Audition 1.5:

Image

I think dat the block before 10kHz is what the mic could record, the block after 10kHz looks like noise. The peak volume with the complying frequency is displayed at bottom right.

I couldn't make a better analysis, because the FFT size (scanresolution) is limited to 65536.

Graham C. Williams
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re: Another pocket lockwood success

Post by Graham C. Williams » Sat Jun 17, 2006 3:52 pm

That scan res should be more than enough.
Please, Right click and drag in the X-axis, frequency. Do this to highlight the region 500 - 1000Hz only. Zoom in more if needed.
On the Y axis (level) Right click and highlight the region -6 to -54dB.
With a bit of refining you'll see a nice response.

Graham.

steve
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re: Another pocket lockwood success

Post by steve » Sat Jun 17, 2006 3:59 pm

nicely done!
Im allways suprised when someone gets one of these to run correclty, since I had such a tough time developing the prototype. I guess once yoe hit the right dimensions it turns out to be a pretty forgiving design.
Image

kid jansen
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re: Another pocket lockwood success

Post by kid jansen » Sat Jun 17, 2006 4:13 pm

I've filtered out the noise, and had a look at the spectral view, and noticed something really funny, there are multiple peakes:

time1
711 Hz
1431
2142
2896
3574
4285

time2
700
1431
2153
2885
3563
4242
4952
5652
6319
7773
9173
9829

time3
700
1410
2121
2820
3574
4242
4920
5630
6319
7019
8462
9130
9819


(the frequencies are accurately measured with the frequency analysis function)

You can see those peak frequencies as bright yellow lines in the spectral view.

Image

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re: Another pocket lockwood success

Post by Mike Everman » Sat Jun 17, 2006 4:29 pm

Take a breath, here. You're over-analyzing not enough data, and it's a waste of your time. Anything much beyond the operating frequency is suspect.
You'll notice that all those peaks you're seeing are multiples of that base operating frequency.
Mike
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Jmitchell
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re: Another pocket lockwood success

Post by Jmitchell » Sat Jun 17, 2006 6:54 pm

Yes, also to clear up any confusion, this was originally Steve's design.

Dang911
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re: Another pocket lockwood success

Post by Dang911 » Sat Jun 17, 2006 11:27 pm

So has Steve published the design anywhere on the forum, if I recall he made a thread some time ago, I will go look. Also what fuel did you use. If this can be run on propane, I will built it for sure.
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Jmitchell
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re: Another pocket lockwood success

Post by Jmitchell » Sat Jun 17, 2006 11:42 pm

Propane won't work, as far as I know. You need acetylene. I was running around 11(!) PSI into it, and couldn't get a flame out, I was more worired about the gas pressure going above 15 PSI!!!

Dang911
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re: Another pocket lockwood success

Post by Dang911 » Sun Jun 18, 2006 12:36 am

15 psi with propane? You don't have to worry about psi so much with propane. I run some of my jets at 65+ psi in a injector with better results than 12 psi at an equal flow rate. Propane is pretty stable.
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Mark
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re: Another pocket lockwood success

Post by Mark » Sun Jun 18, 2006 12:55 am

I've wondered in the past if a simple straight tube closed at one end would run, sort of like a jam jar effect, only more perky. Acetylene is really peppy stuff, and very forgiving in the rich to lean spectrum.
And it would be hard to image using the jam jar shape with acetylene, certainly you would want more length to width aspect lest it go bang instead of fluttering or pulsejetting in some likeness.
The straight tube would have to refresh itself much less, because acetylene isn't as fussy as a normal fuel. Perhaps you could get it up to a pulse-detonation reaction in a small pipe. Maybe the pipe could even be a typical pulsejet shape, but without any breathing from the front end, a half a pulsejet so to speak like this snorkeler that just breathes from the tip only. Again, the acetylene pipe jet would be very small, along the same line as Steve's micro Lockwood.
Mark
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