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# Railgun, High or Low voltage? Answered

Okay so i'm making a railgun, and need to get capacitors. Should i go with the ones in the 300-400 volts range, or somewhere around 15-50 volts? I would rather go low-voltage, as they seem to be alot cheaper.

Also, how would I go about making a charging circuit, schematics would be nice.

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seeing that nobody has provided an answer to the charger question yet, if cost is an issue I would suggest using both the capacitors and the charger out of dispossable cameras. you can get them for free from wal mart or any other camera film developing center. I used this method for a coilgun last summer, and it worked decently for my first attempt. although if you are buying capacitors, go with the highest ratings in both capacitance and volts that you can. the volts will give you a powerfull pulse, and the farads determine the length of the pulse. for example, if you have a billion volts with .000001 picofarads you will have no power, the same as having a billion farads at .0001 volts. so you will want the highest ratings in both capacitance and volts. just for a refference, photoflash capacitors are about the minimum you should use, which are about 330 volts at 120-160 microfarads. hope this helps.

an other option would be to use a -30k volt charge from a negative Ion generator.

Use high voltage ones. The cost is worth it when you see the results. Make sure that the caps have alot of capacitance as well.

What voltage are you going to be charging them to? They have to be rated for at least that high.

I think you misunderstood the question. What I mean is, what voltage range would a railgun work best at?

Highest voltage you can get that won't blow out the circuitry, I would presume. More voltage means stronger magnetic field.

(Actually, more _current_ through the coil means stronger magnetic fields, but to get more current you need more energy, which means either more caps or caps charged to a higher voltage or both.)

Try not to kill yourself...

A rail gun requires an arc between the rails, right? In that case, as much voltage as you can manage.

Well yes, but it needs enough voltage to cross the gaps between the rails.

No, that's done by the slug, which should present a dead short.

Steve

Ah, but I thought the slug was supposed to be an insulator, and the arc forms behind it. The arc can be kick-started by a thin filament of wire that stretches between the rails. When the rails are energized the filament vaporizes but the arc remains.

Not in any of the rail guns I've seen it don't - what does the driving ? An arc ain't going to push a slug.

It sure will! Look here.

But it would seem we're both correct - the armature can be either an arc of plasma or a solid metal sabot that splits away from the projectile when it leaves the barrel.

You are absolutely correct about the current though.  It needs to be very, very high.  So, as far as voltage is concerned it would probably depend on whether you use a sabot or an arc as your armature.

Since your energy storage is capacitor based, higher voltage is better than low, up to the limit of the insulation of your coils.

Steve