David Hobby wrote: > > Andrew Crystall wrote: > ... > > > Look, I don't want PLANS! I just don't believe you > > > made it, and you've done nothing to dispel this. > > > How about 20 questions? > > > > > > 1) Did it use an explosion? > > > > A capacitor. Which expoded once when I was test firing it. > > This design flaw fortunately was kinda-antipated and it missed me. ... > A good thing it did. Big capacitors can store a lot > of energy. So all I need to do is pick up a 100KV, 20 Farad > capacitor, from that war surplus store by Area 51... > > ---David
I was trying to clean and straighten out the lab supply closet this afternoon and came across some capacitors labeled "2500 MFARAD." I hope that the "M" in this instance is supposed to stand for "micro," otherwise I am somewhat leery about putting the equipment in the hands of beginning students . . .
Funny, I can't even find the building anymore. Now where am I going to get all my experimental supplies? So it sounds like we need to scale back the size of the capacitor some. I googled a bit, and found an archived exchange at:
http://yarchive.net/metal/large_capacitors.html
I've snipped it some, but this seems to be about what you can get.
> > > >>The suggestion of using capacitor discharge sounds like a good idea to > >>me. It would not be expensive or complex if made from surplus equipment, > >>although it would not be very practical for commercial sale. A 1000 > >>microfarad capacitor bank at 1000 volts gives 500 joules which is in the > >>order of the energy of powder charges used for fire forming typical > >>cases. ... > > Back to the capacitor discharge methods, if anyone still cares... > At least in the Phoenix area you can find large capacitor fairly > cheap. Oil caps which are at about the limit of what a person > can lift are used for power line correction. A few of them in > parallel should do the job nicely. They're designed for AC but > will handle DC ok. Some have built in bleeder resistors, but > that wouldn't hurt this use. One might use electrolytics in > series/parallel with diodes and resistors to prevent reversing > the polarity, but they aren't the best for pulse work. > > It's not hard to build a triggered spark gap which will handle > thousands of amps. Three metal disks in a row. THe middle one > is connected to a spark coil and held at a voltage halfway between > the other two until time to fire. THen a pulse of either polarity > will break down one size, with the other following immediately. > Plain air will carry the current.
30kV/cm in dry air.
-- Ronn! :)
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