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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: Larda » Fri Mar 07, 2008 3:14 pm

Thanks.
Next time i will take the scale with me and measure more exact how much aluminium i use.
I take the powder and wrap it in foil to keep it in place.

Normally i clean the chamber and barrel every time, but i think that you can get away with doing a few shots before cleaning.

Yes you could put all the caps it in parallel for lower ESR, and it will make it possible to get a higher current pulse.
But if you are discharging them into a load with a little higher resistance, then you can get higher current with the caps in serie/parallel and a higher voltage.
I can rearrange the capacitors in my bank to 0,36F 400V if i want, maybe i try that some day and see what gives the best results.

The current limiting resistor is used to limit the charge current so i'm not risking damaging the rectifiers.
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Unread postAuthor: benstern » Fri Mar 07, 2008 6:10 pm

I am extremely impressed with this. Great job!

I too would like a new section of the the forum devoted to electronic based cannons.
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Unread postAuthor: SpudMonster » Fri Mar 07, 2008 7:02 pm

I can state unequivocally that this is one of the most impressive cannons I have ever seen. The workmanship, innovativeness, and the overall "Holy crap" factor are really incredible. Great work! :thumbright:
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Unread postAuthor: clide » Fri Mar 07, 2008 8:15 pm

Haha, that is amazing :lol:. That video has got me grinning ear to ear, it is a great combination of noise, impressive muzzle blast, and great destruction.

What are the overall dimensions and weight of the capacitor bank?

Great job.
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<a href="http://gbcannon.com" target="_blank"><img src="http://gbcannon.com/pics/misc/pixel.png" border="0"></a>latest update - debut of the cardapult

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Unread postAuthor: fatcat » Fri Mar 07, 2008 9:06 pm

That is an amazing idea(and gun). I hope we will see more of these around.

I looked around the internet but didin't find much info on Electothermal weaponry. where did you come up with an idea like this?
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Unread postAuthor: Larda » Fri Mar 07, 2008 9:09 pm

clide wrote:What are the overall dimensions and weight of the capacitor bank?

The bank weight about 73Kg.
Tomorrow i will do some more shooting and try to determine the muzzlevelocity..
What do you think is the best way to do that on a ETG?
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Unread postAuthor: cenzo188 » Fri Mar 07, 2008 9:47 pm

that is amazing. If I had the shop, time, and money i would totally build one of those. It would be nice to know the FPS of the projectile, if you happen to have a chronometer (I probably spelled that wrong).
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Unread postAuthor: Larda » Fri Mar 07, 2008 9:53 pm

cenzo188 wrote: It would be nice to know the FPS of the projectile, if you happen to have a chronometer (I probably spelled that wrong).


Unfortunately not, i was planing to try a ballistic pendulum, or try to use a microphone to record the sound of the projectile.
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Unread postAuthor: chartreusesnot » Fri Mar 07, 2008 10:48 pm

to determine the speed, you can shoot it into a hanging block of wood, or something that it will stick in, and measure the mass of the projectile and hte wood, and measure how far up it swings. This is called a ballistic pendulum, and it is very inaccurate. Look it up on wikipedia for calculations. Or you could get a Chrony.
^^^^^^
Edit... Heh didn't read ^^that^^
^^^^^^
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Last edited by chartreusesnot on Mon Mar 10, 2008 12:41 am, edited 1 time in total.
_Fnord wrote:OMG you have broked teh universe!!!11exclamationpoint!1!

http://www.youtube.com/watch?v=UnKN7LXqizw
http://www.youtube.com/watch?v=oVm_3eEPEgM
http://www.youtube.com/watch?v=wLNjMSGxp00
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Unread postAuthor: Larda » Fri Mar 07, 2008 10:55 pm

The problem with a normal Chrony is that will have a problem with the big muzzle-flash from the ETG.
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Unread postAuthor: bigbob12345 » Fri Mar 07, 2008 11:00 pm

well to fix that you could simpley move it back from the chrony 10 or 20ft but then you risk hitting the chrony which would be bad.
I say just make a ballistics pendulum as mentioned above which isnt very accurate but will give us a rough idea of how fast it is going.
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Unread postAuthor: MrCrowley » Fri Mar 07, 2008 11:09 pm

Very very very nice!

Those videos were great too :)
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Unread postAuthor: ghostman01 » Fri Mar 07, 2008 11:25 pm

wow this thing really packs a punch sort of like the electricity is the firing pin and aluminum is the black power
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Unread postAuthor: starman » Sat Mar 08, 2008 12:23 am

ajdevi92 wrote:wow this thing really packs a punch sort of like the electricity is the firing pin and aluminum is the black power


Some modern consumer fireworks use aluminum powder as the primary fuel with an oxidizer agent blended in. Aluminum has an amazing amount of potential energy just waiting to be released...just needs a fairly high level of energy to release it. This gun certainly applied the right levels...VERY VERY nice shootin'....

I can't see this as the next "spud gun" type. Too expensive, too dangerous.
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Unread postAuthor: Hailfire753 » Sat Mar 08, 2008 12:44 am

Wow, I never thought this much carnage was possible with a homemade electrothermal gun! Absolutely Amazing.
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