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IrC
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Wasn't actually asking a question, rather pointing out to him the movement of the turns was causing the breakage due to the tremendous force applied
by the magnetic field. Is why I went to tubing but your right about the low impedance being hell on the switching device. I wasted many monster hockey
puck SCR's before going to the trailer ball triggered gap. Loud but cheaper in the long run. You guys are getting me interested in playing with mine
again it's been stored in sections for years now. I also tried the casting but it also breaks apart soon. I used a bunch of JB Weld once and it broke
apart faster than clear acrylic casting resin. Never had any luck with any of those ideas. Probably OK for under a hundred joules I suppose so worth
trying.
"Science is the belief in the ignorance of the experts" Richard Feynman
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elementcollector1
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Quote: Originally posted by MadEngineer  |
Hi all, I'm the evil twin of MrHomeScientist and the one that built the coil gun he posted. He showed me the thread and I wanted to jump in with any
info on my design. I'm an EE by degree but shamefully threw this device together with back of the napkin calculations. |
Welcome to ScienceMadness! It's not shameful at all to build such a cool thing.
Hmm. I don't think I'm willing to spend this much on my coil. Thanks for the more precise info, though - it really does help!
[Edited on 29-9-2013 by elementcollector1]
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IrC
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Search around for surplus and think of hacker sources. You can build it for a fraction of cost if you do. Medium size setups more fun really. Less
headaches, less dangerous. Besides you can shoot it more often. Myself, I think the ideal size to build at minimum is a quarter squisher. Added bonus
is decent rail gun power range. That means in the 5,500 joule range but that's just me.
http://205.243.100.155/frames/shrinkergallery.html
http://www.matsceng.ohio-state.edu/~daehn/metalforminghb/tab...
http://www.powerlabs.org/railgun.htm
"Science is the belief in the ignorance of the experts" Richard Feynman
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elementcollector1
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As it turns out, there's an indicator light built in to the camera flash circuit I hacked to build the coilgun. It's some sort of tiny neon tube
shaped like a LED, and glows red when ready. All I have to do is unsolder it, stick some magnet wire in there so I can place it where I want to, and
resolder it.
Anyway, construction is still ongoing - right now I'm fussing over a sort of electronic 'trigger' that consists of two pieces of blank PCB with large
dots of solder on each one, and a wire in the solder. While the first board is stable, the second is on a hinge that is connected to a small thing
shaped roughly like a standard gun trigger, and works about the same - when the trigger is pulled back, the two boards touch due to the solder and
short. These are soldered to the two tiny prongs that stick out on the side of the camera circuit - visible here on the middle right:
<img src="http://www.spudfiles.com/spud_wiki/images/e/ef/Camera_flash.jpg" width="600" />
Apart from that, the only things left to do are solder the charge button, wire the coil and buy some capacitors. I'm planning to use a solderless
breadboard, so I can add more capacitors if necessary.
<!-- bfesser_edit_tag -->[<a href="u2u.php?action=send&username=bfesser">bfesser</a>: reduced
image size(s)]
[Edited on 21.10.13 by bfesser]
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bfesser
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I wouldn't recommend
using a solderless breadboard for prototyping high-voltage or high-current circuits. You may experience unexpected shorts and arcing between the
rails.
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Metacelsus
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Very interesting. In fact, I am working on a coilgun right now. I found eight 330V 1200uF electrolytic capacitors while taking apart some TVs (for the
flybacks). I have absolutely no idea why they were in there, but they're going to make an awesome (825 J) coilgun. I prototyped a 12V to 330V boost
converter on a perfboard yesterday, but I have yet to test it out. I think I shouldn't have problems with shorts or arcing, given the relatively low
voltage compared to the breakdown voltage of air. Pics will come soon, at least if I remember to post them.
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watson.fawkes
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| Quote: Originally posted by elementcollector1 | | It's some sort of tiny neon tube shaped like a LED, and glows red when ready. All I have to do is unsolder it, stick some magnet wire in there so I
can place it where I want to, and resolder it. |
The classical NE-2 neon indicator lamp has a breakdown
voltage of around 90 V, so you'll want something with better insulation than magnet wire. If you were buying it new, you'd specify AWM (appliance
wiring material) with 300 V rated insulation. You won't need much current; 24 gauge should suffice.
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elementcollector1
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| Quote: Originally posted by watson.fawkes | | The classical NE-2 neon indicator lamp has a breakdown voltage of around 90 V, so you'll want something with better insulation than magnet wire. If
you were buying it new, you'd specify AWM (appliance wiring material) with 300 V rated insulation. You won't need much current; 24 gauge should
suffice. |
Hmm. I have 12-gauge solid wire, as well as 12-gauge speaker wire. I also have some fairly thin wire that may well be 24-gauge, although I'll have to
check. Thanks for the tip-off!
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