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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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28,8Kj ElectroThermal Gun! (Soon handheld)

Unread postAuthor: Larda » Thu Mar 06, 2008 11:59 pm

To start with i must say that aim not sure if this is the right place to post this, it doesn't fit in any of the categories.
So please feel free to move this if its in the wrong place.

Some time ago i started building a fairly large capacitor bank that aim planing to use for my rail-gun project.
Its consist of 24, 15000uF 400v capacitors for a total energy of 28800 Joules.
The capacitors are arranged in 3 parallel banks that are wired in series for 1200v and 40000uF.
To test the capacitor bank i decided to build a ElectroThermal Gun.
The ETG (ElectroThermal Gun) works by discharging the capacitor bank threw fine aluminium powder and foil inside a chamber.
The electric current then heats the aluminium enough to make it evaporate and turn into plasma.
When the aluminium turns into superheated plasma it expands and the pressure in the chamber increases, the plasma also heats the air so it expands.
The expanding gases then force the projectile down the barrel like a conventional (spud)gun.

The ETH have a 12mm smooth-bore barrel that is screwed into a steel chamber with a electrode that goes threw a insulator in the end, the power is then feed into that electrode and threw the aluminium-powder.
Some videos.

Test shot 1:
http://www.vimeo.com/751433
Test shot 1, Second view:
http://www.vimeo.com/751469
Test shot 2:
http://www.vimeo.com/751476

I hope you like it, :D

If i made any typos please don't kill me, my English is not so good and its 6AM so i really need to get some sleep. :sleepy1:

Edit:Typos
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Attachments
chamber.jpg
The chamber of the ETG.
You can also see the two 35mm2 cables connected to the chamber.
barrel.jpg
12mm ID smooth-bore barrel.
capacitorbank.jpg
The 28,8Kj CapacitorBank.
damage1.jpg
The projectile first went right threw a total of 60mm of wood, the continued threw the bricks and ricochet on a dumpster.
comparison.JPG
The ETG compared to a calliper and a small ETG i also made of stainless steel.
flash.jpg
The muzzle-flash caught on film
Last edited by Larda on Sat May 03, 2008 9:42 pm, edited 2 times in total.
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Unread postAuthor: Killjoy » Fri Mar 07, 2008 12:07 am

Good god thats incredible. I've heard of these discussed but never actually seen a finished working one.
Thats incredible, nice work.
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Unread postAuthor: Davidvaini » Fri Mar 07, 2008 12:10 am

I only see 1 bank in that lower picture... where are the other caps?
Also what gauge wire is that leading to the gun?
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Unread postAuthor: jackssmirkingrevenge » Fri Mar 07, 2008 12:17 am

Fork in hell, that's brilliant :D

Some time ago i started building a fairly large capacitor bank that aim planing to use for my rail-gun project.


Is that the same railgun you have built this pneumatic for?

If i made any typos please don't kill me, my English is not so good and its 6AM so i really need to get some sleep.


I'm just going to pick on one if I may, 'cause it's hilarious:

"The expanding gases then force the projectile down the barrel like a conversational (spud)gun."

When you're spending enough time in your workshop for your projects to start talking to you, definitely time for some fresh air :) the word is "conventional". But it's just a silly typo, with launchers like that you can make all the typos you want, can't wait to see that railgun :D
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Unread postAuthor: Killjoy » Fri Mar 07, 2008 12:17 am

Also what gauge wire is that leading to the gun?


Looks like 4 gauge but I could be wrong. I forgot to ask, whats your
projectile?[/quote]
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Unread postAuthor: Larda » Fri Mar 07, 2008 12:18 am

Davidvaini wrote:I only see 1 bank in that lower picture... where are the other caps?
Also what gauge wire is that leading to the gun?

Ohh, i meant 3 rows that are wired in series, only one bank so fare.
But i have enough capt to built at least to more identical banks. :D
I use 35mm2 cables, that's about AWG 2, but aim planning to upgrade to at least two in parallel.
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Last edited by Larda on Fri Mar 07, 2008 12:22 am, edited 1 time in total.
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Unread postAuthor: Davidvaini » Fri Mar 07, 2008 12:21 am

Id say get 2 banks and up the power... Your base seems to be able to support it and 2 banks would create 4X more power :D

but over all its very decent and looks like a good little project you have going on.
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Unread postAuthor: Larda » Fri Mar 07, 2008 12:32 am

Killjoy wrote:
Also what gauge wire is that leading to the gun?

Looks like 4 gauge but I could be wrong. I forgot to ask, whats your
projectile?

I used two projectiles, first was a broken Center drill, the second a broken solid carbide drill, really hard and really heavy. :D

jackssmirkingrevenge:
Thanks for the correction. Sometimes the spellcheck choose the wrong word. :lol:
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Last edited by Larda on Fri Mar 07, 2008 12:36 am, edited 1 time in total.
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Unread postAuthor: POLAND_SPUD » Fri Mar 07, 2008 12:33 am

wow... :shock:
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Unread postAuthor: Lentamentalisk » Fri Mar 07, 2008 1:03 am

Really nicely done! My friend and I are working on building a Cap bank and dis/charging circuit, mainly for our microwave gun, but we will also be testing it on on an ETG.
Why is it that everyone all of a sudden is making ETGs?

Yet again, very nicely done!
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Unread postAuthor: jackssmirkingrevenge » Fri Mar 07, 2008 1:05 am

Ragnarok's going to cream his pants when he sees this :D

could we have some more detailed damage pics?
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Unread postAuthor: Novacastrian » Fri Mar 07, 2008 1:45 am

Effin wow, thankyou very much for making me aware of your project :D I will not for one second pretend that i know the faintest about what you have built but <GOD> that is some nice (stuff that words can't describe).

I agree with JSR, come on Rag where are you homeboy-Check this sh!t out!

Edit: Alright so i know how it works, but but but but i gotta get me one of those :twisted: It looks so sick.
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Unread postAuthor: Gunner » Fri Mar 07, 2008 4:52 am

Larda, Thats amazing gun, but I`d like to know that can you shoot trough the 10cm wood and I would like to see more damage pics. Thanks.
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Unread postAuthor: Ragnarok » Fri Mar 07, 2008 6:25 am

Novacastrian wrote:I agree with JSR, come on Rag where are you homeboy

*Little fruit machine noise as head pops into view*
Answer: At that time, asleep, and I don't have JSR's superhuman powers to be on the forum as he sleeps (if he even does...)

There's not really much I can say to that wonderful piece of work - No real suggestions for improvement (at least, not practical ones.)

What I can say is that, I don't quite get Davidvaini's "2x cap bank = 4x power" theory - electrical power, possibly, if they were wired in series (but not quite - inductance and heating would slightly blunt the electrical power, but it would increase in that sort of region).
However, assuming we're talking about kinetic energy, no - that would require a doubling of efficiency, and by that logic, you could break 100% efficiency by just adding enough banks.

Well, I'm certainly impressed, and I'm looking forward to seeing either your next project - or any more info on this one. :thumbleft: - Not quite the right emoticon, but they don't do a suggestive "smile, thumbs-up and nod" one, that'll have to do.
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Does that thing kinda look like a big cat to you?
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Unread postAuthor: Larda » Fri Mar 07, 2008 7:09 am

Thanks for your comments, everyone!
Lentamentalisk:
What voltage and capacitance are you using?
Any link?

Here is a few more damage pics, really not that detailed but i can take some more this weekend when i do some more shots.
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Attachments
switch.jpg
The switch i using.
projectile.jpg
Second projectile made out of a broken solid-carbide drill. Weight 72.6g
Its 12.00mm and the ID of the barrel is 12.04mm.
projectile.jpg (25.97 KiB) Viewed 30093 times
damage2.jpg
Damage.
damage.jpg
Damage.
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