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Low Voltage Capacitor ETG

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hen918

Sun Nov 02 2014, 12:55PM

Registered Member #11591 Joined: Wed Mar 20 2013, 08:20PM
Location: UK
Posts: 556

You have to be very careful with hydrogen and oxygen; under pressure they can spontaneously combust, leave them at RTP or below.

You need everything as strong as possible (better over-engineered than under-engineered); I would use 12.9 bolts, they are hardly more expensive than 8.8 ones, and a lot stronger.

spectre

Sun Nov 02 2014, 01:08PM

Registered Member #42773 Joined: Sun Jan 12 2014, 03:38PM
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Posts: 7

hen918 wrote ...

You have to be very careful with hydrogen and oxygen; under pressure they can spontaneously combust, leave them at RTP or below.

You need everything as strong as possible (better over-engineered than under-engineered); I would use 12.9 bolts, they are hardly more expensive than 8.8 ones, and a lot stronger.

That was what i meant with 0.5 bar. On a pressure gauge set to 0 at normal the oxygen/hydrogen mix would read -0.5 bar

reason for 8.8 was that is our standard bolt, but yeah 12.9 is better... would making the blast chamber and barrel from titanium be worth the hassle of machining? it is not that expensive as a material, it is the machining that jacks the price up. (b*tch to work with)

hen918

Sun Nov 02 2014, 01:23PM

Registered Member #11591 Joined: Wed Mar 20 2013, 08:20PM
Location: UK
Posts: 556

Oh I know, I'm a maintenance engineer that works in a company that machines titanium, nimonic, stainless, aluminium and brass for aerospace. The machines that breakdown most often are the ones that often machine titanium. Everyone moans when they get a job in titanium.

I don't think titanium would be worth, it stainless steel would probably be best: not too difficult to work with, not too expensive. The last thing you need is a titanium fire!

Shrad

Sun Nov 02 2014, 07:09PM

Registered Member #3215 Joined: Sun Sept 19 2010, 08:42PM
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if I was to make an ETG propelling charge, I'd use a tab of aluminium dipped in some kind of wetting agent which would leave only a pellicul, then dip it in sulfur powder and either dry or bake gently to make it stick (at safe, 50Â°C temp I'd say, but take care to verify it won't self-ignite)

this will make the same result as a flash powder mix if you have made sure to get the right ratio

maybe a dip in Fe2O3 would also prove to be of some use ;) and you'd be able to stock it safely

hen918

Sun Nov 02 2014, 07:21PM

Registered Member #11591 Joined: Wed Mar 20 2013, 08:20PM
Location: UK
Posts: 556

hummm, thermite ETG, interesting...

Thomas W

Sun Nov 02 2014, 07:26PM

Registered Member #3324 Joined: Sun Oct 17 2010, 06:57PM
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Hmm, this might be a little over complex... but what about this:

Bore out a barrel in stainless steel, then insert a strong ceramic tube inside, drilling holes in the bottom of the barrel for electrodes and a magnatron end. Fill up the tube with aluminium fileings and activate the magnatron, causing all those bits of aluminium to heat up, possibly even close to the plasma stage, then dischage your energy into there. The ceramic would be needed to keep anything from shorting out.... Its just an interesting idea.

spectre

Sun Nov 02 2014, 07:30PM

Registered Member #42773 Joined: Sun Jan 12 2014, 03:38PM
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Posts: 7

Shrad wrote ...

if I was to make an ETG propelling charge, I'd use a tab of aluminium dipped in some kind of wetting agent which would leave only a pellicul, then dip it in sulfur powder and either dry or bake gently to make it stick (at safe, 50Â°C temp I'd say, but take care to verify it won't self-ignite)

this will make the same result as a flash powder mix if you have made sure to get the right ratio

maybe a dip in Fe2O3 would also prove to be of some use ;) and you'd be able to stock it safely

So, by using Fe2O3 on aluminium, i will be igniting and plasma-ing(?) thermite? sounds fun, will give that a go.

how about gun cotton?

to make it clear, this is a fact finding and ideas thread, i will start a build and fire thread when the parts are ready.
is there interest for a build thread, or do you guys just want to see things being shot?
and if a build thread, how detailed?

Shrad

Sun Nov 02 2014, 08:23PM

Registered Member #3215 Joined: Sun Sept 19 2010, 08:42PM
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Posts: 780

I guess the vaporization of the aluminium pad will also vaporize the deposit it holds, and that the reaction occuring between aluminium and the other product will be catalysed by vaporisation and pressure buildup...

another go would be to make a barrel bottom out of ceramid and a separate barrel, with electrodes at the bottom of the barrel cup, and ram flash or thermite powder in the cup to replace the fuse

hen918

Sun Nov 02 2014, 09:36PM

Registered Member #11591 Joined: Wed Mar 20 2013, 08:20PM
Location: UK
Posts: 556

sounds like this ETG will end up shooting iron vapour. I'd like to see it!
The thermite reaction does not release any gas though, so it wouldn't accelerate the projectile much, and you would have to use a non-oxygen gas to stop it reacting with the aluminium instead of the iron oxide.

Shrad

Mon Nov 03 2014, 08:25AM

Registered Member #3215 Joined: Sun Sept 19 2010, 08:42PM
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Posts: 780

haha I guess you're right

as far as I know, the flash powder mix will release a decent amount of gas when used with KNO3 or KMnO4 due to the oxygen, so I guess that the aluminium pad can be dipped in KNO3 paste before it is in sulfur...

do not try this with KMnO4

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