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28,8Kj ElectroThermal Gun! (Soon handheld)

Built a pneumatic cannon? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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Unread postAuthor: mark.f » Mon Mar 10, 2008 10:10 am

I only just saw this thread today, (been too preoccupied with airguns for the past few weeks to take must interest in spudding).

Holy Crap! You've done what most of use have been talking idly about for months! (Sorry Rag). To actually see somebody build and experiment is amazing. Even I've thought about ways to do this will steel wool and standard SCH-80 pipe, but I don't think it would have had near the efficiency and power of your design.

Good job on progressive thinking, and I hope other members don't rule out this possibility as the "next generation" of spudding, because anything's possible. A lot of people here are smarter than some people think, and this operation principle is not beyond their grasp.
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Unread postAuthor: DYI » Mon Mar 10, 2008 10:13 am

The concept certainly isn't beyond most members' grasp, but the $30k capacitor bank probably is :wink:
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Unread postAuthor: Jared Haehnel » Mon Mar 10, 2008 10:15 am

steel wool and standard SCH-80 pipe


I don't think pvc would stand the heat and it would take a lot of energy to turn steel into a plasma.

30k....hmmmm the things I could buy...
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Unread postAuthor: DYI » Mon Mar 10, 2008 10:27 am

Quote:
steel wool and standard SCH-80 pipe


I don't think pvc would stand the heat and it would take a lot of energy to turn steel into a plasma.



He's talking about SCH 80 steel pipe.
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Unread postAuthor: Larda » Mon Mar 10, 2008 11:49 am

Ragnarok wrote:From that video, and guessing from the markings on your back board, it looks like you're doing about 260-270 m/s (860-880 fps), which is around 3200 Joules (2400 ft-lbs) of kinetic energy. That's a phenomenal amount from a 12mm barrel of that length, and it would seem you're achieving an average pressure of around 10000 psi - possibly more, I'm not sure how long your barrel is, so I guessed around 40 cm from the picture in the opening post - which is a full order of magnitude above anything anyone else has yet achieved (at least, that I can think of).

So, it's not actually supersonic, only about 80% of the way there, but no doubt if you used a projectile of somewhere under 50 grams, you could manage to break the sound barrier.

It's also a respectable 11% efficiency. Ooh, I can see more of these being made.


I must have been sleeping when i uploaded the video, the pendulum weights 4500g not 5500g that i stated in the video.
That gives me "only" about 210m/s (690 fps) , 2000 Joules (1470 ft-lbs) and a efficiency of 5.5%.

starman wrote:I would be interested in the possibililty of adding some water in with the aluminum powder, possibly somewhat little less powder to make room in your chamber. If you added a minimalist (or more even) burst disk, you could experiment with different slurry mixtures and see what works best.

This is based on the aluminum powder flashing to plasma and thus flashing the water to steam. The military has been prototyping the plasma/steam combo for several years and it supposedly has multimach potential if configured correctly. It may require more power to work properly than you have here, but, maybe not.

I actually i did try that by adding 4ml of 50/50 mixture of Water and Isopropanol. Because i only have one velocity measurement i cant tell if it made any different.
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Unread postAuthor: Jared Haehnel » Mon Mar 10, 2008 12:25 pm

Quote:
Quote:
steel wool and standard SCH-80 pipe


I don't think pvc would stand the heat and it would take a lot of energy to turn steel into a plasma.



He's talking about SCH 80 steel pipe.



Sorry spring just sprung forward and hour so I'm not yet awake....
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Unread postAuthor: starman » Mon Mar 10, 2008 11:36 pm

Larda wrote:I actually i did try that by adding 4ml of 50/50 mixture of Water and Isopropanol. Because i only have one velocity measurement i cant tell if it made any different.


You'll probably need to go to a burst disk arrangement to see any further benefits with steam beyond your present blast...and possibly a different chamber configuration. You might try preheating the slurry to some greater tempurature than room temp and then fire it before it can cool down. If water is involved, the closer to boiling it is, the more chance you'll have of a steam flash.
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Unread postAuthor: Larda » Mon Mar 10, 2008 11:54 pm

Copperboy wrote:Satan i Gatan!!

How did you machine your "chamber"? Nice work! :)

Copperboy:Sweden?


Some Pict's of the chamber.
The chamber is made of Cr-Mo- steel.
The brass parts is later made of Teflon.

And a short video of me milling hex on the en-caps.
http://www.vimeo.com/773647

starman:yes you are probably right.
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ETG3.jpg
ETG4.jpg
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ETG7.jpg
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milled.jpg
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milled_deburred.jpg
milled_deburred.jpg (36.17 KiB) Viewed 3101 times
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Unread postAuthor: Gunner » Thu Mar 13, 2008 1:43 pm

Thats amazing, just keep updating us by pictures :D
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Unread postAuthor: SpudFarm » Thu Mar 13, 2008 1:47 pm

i just cant get how those work...
can somebody explain detailed?

EDIT: i just got it :)
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Unread postAuthor: Gunner » Thu Mar 13, 2008 2:12 pm

I have not too understanded it yet, but I know that plasma pushes the bullet but could someone draw a little scetch how does ETG works?Thanks.
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Unread postAuthor: POLAND_SPUD » Thu Mar 13, 2008 6:37 pm

Are you going to build new guns... you know with longer barrels or in bigger/smaller calibers ?
could you provide more information about this gun ? what is the volume of gases/plasma produced? are you going to measure it somehow ?
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Unread postAuthor: Hotwired » Fri Mar 14, 2008 8:38 am

Probably the best hobby ETG out there :)

I know powerlabs had one started which blew up several spark plugs but it's dwarfed by the power of this.


Whats it like with nothing in the chamber but the spark?
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Unread postAuthor: Larda » Fri Mar 14, 2008 9:47 pm

POLAND_SPUD wrote:Are you going to build new guns... you know with longer barrels or in bigger/smaller calibers ?
could you provide more information about this gun ? what is the volume of gases/plasma produced? are you going to measure it somehow ?


What information are you interested in'? I don't really know the volume and i have no idea how to measure it.

Actually i have already built a smaller caliber ETG.
Its the first prototype i built and its made out of stainless-steel, the barrel is 7mm and the gun is about 135mm long.
I only tried it with a smaller capacitor bank the results was so promising so i built the current one.
Two videos of the prototype.
I had some newspapers in the box to stop the projectile but instead of stopping it embedded itself into the wall. :evil:
http://www.vimeo.com/786297
http://www.vimeo.com/786306

And YES that is in my living-room.... :P
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pocket_ETG.jpg
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pocket_ETG2.jpg
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Unread postAuthor: LikimysCrotchus5 » Fri Mar 14, 2008 11:20 pm

wow that is very nice very a small caliber launcher, you really wont see too many mini launchers doing that.

I think thats really nifty. And let me tell you that the recoil there doesnt lie about its power.

Nice work, again :)
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