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Rail gun

All non-spudgun related discussion goes here such as projects, theories, serious questions, etc. All "off-topic" posts (aka useless posting, determined by moderators) will be removed.
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Rail gun

Unread postAuthor: Rambo » Sun May 14, 2006 4:49 am

Yesterday I tried to make a rail gun with my 650000mf capacitor(my BFG ignitor).The projectile was a piese of aluminium foil.At 12v when I push the botton it only makes a tiny spark between the projectile end the rail The capacitor remains fully chrged.I think the only think I can do is to rise the voltage.What voltage do you think should be enough, and what is the voltage for the camera flash ignition?
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Unread postAuthor: Benny » Sun May 14, 2006 4:55 am

use a camera flash to charge the capacitor, what material did you use for the rails? by the way, most camera flashes are around 330 volts.
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Unread postAuthor: Rambo » Sun May 14, 2006 5:53 am

The rails are just an ordinery iron.I can't charge 6,5v capacitor with 330v.
I shold try the gun with 400-1000v and more copacitors.
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Unread postAuthor: rna_duelers » Sun May 14, 2006 5:55 am

The projectile needs to be moving before the charge is ran through the rails it needs it direction of motion and.I found this cool web site and he has a small table top one maybe have a look and see how it works i remember seeing pics of it on here.
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Unread postAuthor: Rambo » Mon May 15, 2006 1:06 am

Another question.What trigger should I use.At low voltage it's easy, but at 1000v and a lot of amps.It can be a very expencive tiristor.
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Unread postAuthor: rna_duelers » Mon May 15, 2006 1:19 am

Go ghetto,make one that is very simple such as two connections that when you touch together the circuit is complete,it will work and wont cost much at all.
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Unread postAuthor: Rambo » Mon May 15, 2006 1:58 am

The problem is that for this gun I will use more then 500v>there will be too much loses in the swich.May be if I sqash the two contact plates with a hummer :lol:
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Unread postAuthor: FiveseveN » Mon May 15, 2006 9:10 am

Go for triggered spark gap . After SCRs, spark gaps are preferred for this aplication. I have an idea for a simple trigered spark gap; will be posting soon. If you use mechanical switching not only will the two plates be welded shut, but you'll lose most of the energy from resistive heating.
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Unread postAuthor: Rambo » Wed May 17, 2006 11:01 am

I just made my naw rail gun.It uses 8 110V 2200mf capacitors.It fires small balls from aluninium foil.But it can't do any damage :cry: Because I have no botton I tuch the wire from the gun to the capacitor.The spark is so huge that I cant remember the spark in the gun.
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Unread postAuthor: FiveseveN » Wed May 17, 2006 12:39 pm

Man, if I had as many toys as you do when I was your age :lol:
I said I'll draw a triggered spark gap, I'll do it tonight. It should solve your trigger problem.
But why have you wired your caps in series? Do you use a high voltage source to charge them?

8 X 2200mf @ 110V in series = 2200mf @ 8800V
8 X 2200mf @ 110V in parallel = 17600mf @ 110V

And I don't see a charging resistor. Careful there :)
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Unread postAuthor: Rambo » Wed May 17, 2006 12:58 pm

I don't think it's going to work with less then 300v.I charge the capacitors two by two with 220v.
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Unread postAuthor: FiveseveN » Wed May 17, 2006 2:51 pm

Here's a good description of the trigatron: http://www.angelfire.com/80s/sixmhz/trigatron.html

You should use large screws, sharpened at the end, for the main electrodes and a smaller screw, even sharper, for the trigger electrode.
For 220V, the distance between the main electrodes should be about 0.7 mm, but I could be wrong.
You feed the trigger electrode from a high voltage source - the higher voltage, the better. You could start with the sparker you've been using on combustions. If it doesn't work, make the gap smaller or try a different HV source. An air ionizer would be perfect.
Connect only the negative output of your HV source. If it still doesn't work, add another trigger electrode opposite to the negative one (you will connect this to the positive output), so the main electrodes and the trigger electrodes are at a 90 degree angle.
The triggers should be close enough to eachother to create a spark, but far enough from the main electrodes to prevent arc-over and discharge through the HV source. That would hurt :)
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