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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: Lentamentalisk » Sat Mar 08, 2008 1:10 am

What is the issue with the muzzle flash messing with the chrony? How does that work? Does the chrony read the muzzle flash rather than the projectile?

@larda: I dont know exactly what voltage and such I will be using, but my friend works at a computer recycling center, and they have half a million extra caps that we are going to take.
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Unread postAuthor: SpudMonster » Sat Mar 08, 2008 4:53 am

Just out of curiosity, how well would magnesium powder work in this gun?
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Unread postAuthor: psycix » Sat Mar 08, 2008 7:15 am

You could also fire it into a box o truth built up from milk jugs full of water.
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Unread postAuthor: CpTn_lAw » Sat Mar 08, 2008 7:20 am

Some people here confused thi with a railgun...This is not a railgun. For an amateur project, it surely required less work. A Railgun doesn't work on that principle, it uses and electromagnetic-driven arc to propel a metal-like projectile.
What you have here, is more powerful man, it's impressive! I suggest you try adding some more aluminium powder before increasing the electrical power. Big up!
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Unread postAuthor: Ragnarok » Sat Mar 08, 2008 8:01 am

chartreusesnot wrote:This is called a ballistic pendulum, and it is very inaccurate.

They can actually be very accurate. A ballistic pendulum can give good readings, as long as the various values are known properly, and it's dimensions are suitable for the projectile.

However, it's not particularly easy to make or use one to get the best results out of them. However, they can easily be more accurate than a lightgate chronograph.

SpudMonster wrote:Just out of curiosity, how well would magnesium powder work in this gun?

Not quite as well. You'd lose a bit more energy to oxidisation, and presumably the higher resistance of magnesium would lose a little power too.

However, I don't know whether those changes would be too noticeable.

EDIT: Spieling Misstooks.
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Unread postAuthor: Larda » Sat Mar 08, 2008 8:10 am

What dimensions do you think are suitable for my projectile?
I was thinking something like 1:50 mass ratio.
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Unread postAuthor: Ragnarok » Sat Mar 08, 2008 8:29 am

Larda wrote:What dimensions do you think are suitable for my projectile?
I was thinking something like 1:50 mass ratio.

Well, the arm length is also important, and an educated guess at a velocity would also help decide on suitable dimensions. Still, it's quite a task to build a really good pendulum, and then you need to fiddle with all kinds of different maths.

So although you can get good results, it might be best to try sound recording first.
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Unread postAuthor: Gunner » Sat Mar 08, 2008 10:18 am

Could someone explain how does that gun works? :lol:
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Unread postAuthor: Eddbot » Sat Mar 08, 2008 11:59 am

good god, that's amazing :shock:

man... you really got to get to these things early 'cause reading 4 pages of posts becomes a chore :roll:
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Unread postAuthor: Ragnarok » Sat Mar 08, 2008 1:01 pm

Gunner wrote:Could someone explain how does that gun works?

Yes, either read the first post more closely, because it explains there, or you could follow this link and look there.

Yes, I'm all for not newb-bashing, but Gunner has been here long enough to know better.
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Unread postAuthor: SNDM » Sat Mar 08, 2008 1:52 pm

Holy smoke.

I once touched a half charged 300V capacitor, felt as though it nearly blew my hand off.
Id be too nervous to even go near your bank, just in case some sort of Darth Sidious reminiscent lightning bolt snaps up to me.

Those are incredible wires, incredible switch, bloody hell.
This is incredible, what sort of distance do you reckon it could launch your projectile to?
I respect that you probably cant see it through the muzzle "flash" (one heck of a "flash") and it may be too small too find.

I take my as yet invisible hat off to you, this is scary.
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Unread postAuthor: Larda » Sat Mar 08, 2008 4:50 pm

I just tried to measure the velocity of the projectile with a ballistic pendulum ,and i think i would have worked fine if the projectile didn't just went right threw the pendulum. :shock:
First i just thought that i got a bad shoot, but then i saw that it was two holes i the pendulum and a big hols in the wood i used as a bullet trap behind the pendulum.
So the projectile just made a hole in the paint bucket i used as a pendulum with over 100mm of wooden planks and 3 pieces of sheet metal.
Then threw 3 more 20mm planks and made a big dent in a 6mm stainless steel plate.
I will upload a video and some damage Pict's later.
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Unread postAuthor: windshrike » Sat Mar 08, 2008 5:16 pm

HOLY SMOKES :shock:
If I wasn't banned from having a bank that large, I'd have to make this.
Great job man amazing, and now you must test this against 1/4" and 1/2" plate steel.

I second adding more aluminum powder.
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Unread postAuthor: DYI » Sat Mar 08, 2008 5:21 pm

If I wasn't banned from having a bank that large, I'd have to make this.


Umm... Why are you banned from having a bank that large?

@Larda: What kind of armor do you have on the pendulum now? High speed tool steel should work unless you're using carbide projectiles. That's some really impressive power you've got there, for the size of it. If not for the fact that I don't have any hookups to acquire massive cap banks, I'd already be building one of these.
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Unread postAuthor: Ragnarok » Sat Mar 08, 2008 7:35 pm

Holy bejeesus!!!I knew there was a lot of power potential in electrothermal cannons, but... bloody hell. I thought what it did to the bricks was a lot, but having heard all of this, my jaw has actually dropped through the floor.

You know DYI, you might have seen that supersonic plasma powered cannon you wanted to. With power like that from a 12mm barrel, this may well be supersonic.

I can tell you, I want one. Pity that's far too much energy for me to safely use where I launch.

windshrike wrote:I second adding more aluminum powder.

More might not actually help. Too much might actually lose power.

Remember, the energy actually comes from the capacitor bank, not the aluminium itself, and the aim is to convert that to plasma as efficiently as possible, for which there will be an optimal quantity.
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