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Best coil and fastest switching system for 8kJ

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Myke

Thu Jul 31 2008, 03:56AM

Registered Member #540 Joined: Mon Feb 19 2007, 07:49PM
Location: MIT
Posts: 969

A very big backpack? That would be quite a heavy backpack imo.

Steve Conner

Thu Jul 31 2008, 10:30AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

If you want something that looks like a gun and works like a gun, regular ammunition propelled by gunpowder is much more practical. An 8kJ coilgun probably needs a trolley to carry it around.

In short, if you want a mean looking gun, get the necessary permits, go to the gun shop and buy one. If you want to learn about electronics and electromagnetism, make a coilgun.

Barry

Thu Jul 31 2008, 03:30PM

Registered Member #90 Joined: Thu Feb 09 2006, 02:44PM
Location: Seattle, Washington
Posts: 301

Who wants to wear 8kj of explosively charged acid on their back? Not me. I probably couldn't lift it anyway. The capacitors alone will weigh between 200 and 600 pounds, right?

But I'm gonna stay at least 20 feet away from 8kj of charged capacitors and ensure they are enclosed in a blast shield. I just hate it when internal arcs or leakage makes them explode.

If I recall correctly, an AK-47 high-velocity round has about 2kj of kinetic energy.

How about insulation? I assume your capacitors will carry >1kv so you can reach the 8kj energy level. The high voltage shielding and insulation requirements might be important if you're going to carry it, and it isn't easy. An arc can jump through a pinhole defect in rubber you cannot see with the naked eye. If it were me, I'd limit maximum voltage to about 300v. I'm a wimp but I'm still alive and sport a full set of appendages.

Just forget about making a portable 8kj coilgun. You might be able to make a three-stage 200j/stage portable coilgun. Maybe. Do your homework first, figure it out.

Cheers, Barry
I used to have a handle on life but it broke off

R.G

Thu Jul 31 2008, 04:21PM

Registered Member #1608 Joined: Sun Jul 27 2008, 12:20PM
Location:
Posts: 10

Dudes, IÂ´m not going to use it on 8kj ALL the time, first testing on low volts, and something else, IÂ´m not gonna use it in the field, or somethinge like that. I figure that a voltage converter connected to the normal grid would help as much, and be much safer than a capacitor bank on your back, and for the wires, Im gonna use a thick rubber seal, around a centimeter thick, with an inner lining of Teflon, and maybe even a spaced tube around the cables.

ItÂ´s destined to be more of an ornament than an actual weapon.

And BTW, I live in Holland, and 2 years ago, even semi automatic weapons were banned from civillian use, since our goverment consists out of pussy richie riches, who have no experience in life in general, and are scared of everything that can threaten their power, or live.

I donÂ´t know why they havenÂ´t banned axeÂ´s and knifeÂ´s yet.

Fraggle

Fri Aug 01 2008, 12:25AM

Registered Member #1526 Joined: Mon Jun 09 2008, 12:56AM
Location: UK
Posts: 216

I`m pretty sure that even a luke-warm disc shooter is technically illegal in the UK so an 8kJ gun-shaped coilgun would probably land you in prison over here!

Barry

Fri Aug 01 2008, 05:24AM

Registered Member #90 Joined: Thu Feb 09 2006, 02:44PM
Location: Seattle, Washington
Posts: 301

"Deal death from above to all pussy richie riches! Die! Die!" Oopsie, no, wait, that might be me, so umm, never mind. Nothing to see here, move along ...

R.G. tell us about your capacitors. What did you choose, and how much does your 8kj weigh?

This sounds like a cool project with judicious use of perspex and blue LEDs.

Cheers, Barry
Build a man a fire and he's warm for an hour, set a man on fire and he's warm for the rest of his life.

Dr. SSTC

Fri Aug 01 2008, 07:24AM

Registered Member #1407 Joined: Fri Mar 21 2008, 07:09AM
Location:
Posts: 222

carring caps in backpack would be very inneficent s most energy would be wasted in the jumper cables

Barry

Fri Aug 01 2008, 03:54PM

Registered Member #90 Joined: Thu Feb 09 2006, 02:44PM
Location: Seattle, Washington
Posts: 301

jovica wrote ...

carring caps in backpack would be very inefficient as most energy would be wasted in the jumper cables

Not necessarily. You need to design the cable length and cross-section such that its resistance is negligible compared to the coil resistance and capacitor's ESR. They will certainly be very thick. I've seen a successful 7kj coilgun that used 3 parallel welding-machine cables in each connection.

The cable inductance is also a concern so you'll want to keep connection lengths as short as practical.

R.G

Fri Aug 01 2008, 08:18PM

Registered Member #1608 Joined: Sun Jul 27 2008, 12:20PM
Location:
Posts: 10

I wanted to use 8, maybe 10 Epcos 12000 mfd 400 volt capacitors, 960 Joules each, and measure 21,5 cm high and 7,5 cm diameter, but also check out his:

that site has a lot of nice things on it.
So give it a try.

Furthermore, the gun is going to weigh around 4 to 5 kilo's, and it to be made out of aluminum, aluminum oxide, and teflon, the two latter to insulate the coils and circuit boards.

And the coilgun doesn't break any laws I know of, so....

rp181

Fri Aug 01 2008, 10:06PM

Registered Member #1062 Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529

those epcos caps are really expensive.

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