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[moved] Very High Voltage Coil Gun

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Travlax1

Thu Apr 03 2008, 04:30PM

Registered Member #1388 Joined: Wed Mar 12 2008, 04:42PM
Location:
Posts: 23

Ok, so im starting to get ready to build. Unfortunately, the maxwell didnt come through but instead I now have four 375 uF, 4000 V capacitors. I will start with only one and will potentially add on depending on the results. Now I'm getting ready to build the launcher. I'm thinking of using a wood block and putting the coil on that with epoxy and a layer of paper on top with expoxy on it (I've heard this is very strong and works well). However, I'm wondering if anyone has any shopping list or list of materials or a website that has all the stuff I need still:

- low gauge magnetic wire
- T-switch that can handle this size discharge
- diode? (I've heard that its expensive to get one strong enough and that it can dampen performance too)
- Safety precaution? (Should I have some kind of enclosure for my capacitor(s) and launcher?) if so, is a plexi-glass box good?

Electroholic

Thu Apr 03 2008, 06:23PM

Registered Member #191 Joined: Fri Feb 17 2006, 02:01AM
Location: Esbjerg Denmark
Posts: 720

what is a "T-switch"?

are you sure you need diodes? are your caps polarized?

Travlax1

Fri Apr 04 2008, 06:19PM

Registered Member #1388 Joined: Wed Mar 12 2008, 04:42PM
Location:
Posts: 23

I guess by t-switch, I mean a mechanical switch versus the SCR thing. The capacitors are arriving tomorrow and I'm not sure if theyre polarized or not. Does anyone know a website or forum post that lists exact products to buy or a website the carries most or all of the equipment?

ramses

Fri Apr 04 2008, 07:57PM

Registered Member #1208 Joined: Thu Jan 03 2008, 05:30PM
Location: Chesterland, OH
Posts: 154

you would have to build a mechanical switch yourself. you could just copy TDU's, which is powered by bed springs, and triggered by removing a large piece of plastic holding the plates apart with a long, insulating string.

plastic protection for insulation around caps would be good, but a non- conductive blast proof box (probably polycarbonate or lexan) around the work coil is almost necessary. at 4000v, they are probably not polarized.

by "low gauge", I would guess you have like AWG 6 in mind? eBay may be good for the magnet wire, but my hardware store sells AWG 4 bear for $1.30 USD per foot. you could blow-torch it and bend it, let it cool, put heat shrink over it and then heat-gun it. AWG 4 is around 3/16" in diameter. Torch is not necessary, but would make it a heck of a lot easier to coil it. even if you let it cool before bending, it would still be annealed (made soft with heat) I suppose you could just chuck it into a fire if you wanted. same effect, but you'd have to dig it out...

play safe, and remember that copper is an excellent conductor of heat (when you touch the hot copper wire, expect you skin to turn black and fall off!

ramses

Travlax1

Mon Apr 07 2008, 06:28AM

Registered Member #1388 Joined: Wed Mar 12 2008, 04:42PM
Location:
Posts: 23

So, for the protective case for the coil should I find a lexan or plexiglass piece that I could sandwich the coil with? Also, this cant be too thick, if im correct, because it lowers efficiency the further away from the coil the projectile is placed? And for the wire, is there something special about magnetic wire versus the spools of wire I have laying around that are simply either a bunch of strands of small wire inside a plastic insulation or one thick wire in a plastic insulation?

Last call for any shopping lists that people know or a checklist of all the parts that I'll need for the final construction of my coil?

ramses

Mon Apr 07 2008, 07:34PM

Registered Member #1208 Joined: Thu Jan 03 2008, 05:30PM
Location: Chesterland, OH
Posts: 154

about the coil protection- just protect from shrapnel moving sideways.

i will guess you decided to go with the pancake coil. you hopefully won't be looking down on the coil the way the projectile will be moving, so, since the projectile will be moving that way, I see no reason to protect that direction from coil shrapnel. standard insulated wire works OK, but magnet wire is better. i recommend that you watch
this

I didn't make it, but another member here did, I'm sure he won't mind.

ramses

Andyman

Mon Apr 07 2008, 08:07PM

Registered Member #1083 Joined: Mon Oct 29 2007, 06:16PM
Location: Upland, California
Posts: 256

Magnet wire simply allows more turns in a smaller space. With the high voltage you're going to be dealing with, I think the jacketed wire would be safer. One nick in the insulation of the magnet wire, and you could have a high current, high voltage short between layers. As long as the jacket isn't TOO thick, it will be fine. Something like 300V insulation would work. The numbers on the insulation of wires are EXTREMELY conservative. I've tested 600v wire at 12,000v and no insulation failure. Of course there was a ton of corona, but no arc. Aaanyway...

Travlax1

Mon Apr 07 2008, 08:36PM

Registered Member #1388 Joined: Wed Mar 12 2008, 04:42PM
Location:
Posts: 23

Ok, I think I'll go with the jacketed wire as I'm more concerned with safety than performance. Now, I'm back to the switch question. I have 4 375 uF 4kV capacitors. I will start with just one and possibly work my way up. I've been told that with a regular knife switch it would arc and they reccomended that I use an Insulated gate bipolar transistor (IGBT). What do you guys think? I would really like to use a mechanical switch and would prefer to buy it rather than building one on my own. any ideas? And whats a good place to get the lexan to build the encasement for the coil?

Andyman

Mon Apr 07 2008, 09:40PM

Registered Member #1083 Joined: Mon Oct 29 2007, 06:16PM
Location: Upland, California
Posts: 256

Well, any igbt that can switch that much current would probably cost as much as a house. Try a trigatron or a solenoid switch. One stationary brass terminal and a second actuated brass terminal. Don't let them touch, or they will permanently weld. Let them get close enough to spark but not touch. Or use a stationary triggered spark gap.

Travlax1

Tue Apr 08 2008, 05:37AM

Registered Member #1388 Joined: Wed Mar 12 2008, 04:42PM
Location:
Posts: 23

Either option looks fine, but I am very new to this and dont have a source for any of these items. Where would I go to find a trigatron? I looked online and couldnt find one anywhere. Anyone have a link to a particular model that would work for my application? Thanks

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