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From: "Gerald L. Hurst" <>
Newsgroups: alt.engr.explosives
Subject: Re: Question for the electronic pro's out there...
Date: Thu, 21 Oct 1999 08:39:38 GMT

I have no interest in spud guns, but I did once run a
set of experiments for a legal case in which I fired
bags of ANFO from a PVC tube using gasoline or
hexane.  This was before the spud gun craze.

In order to generate a spark from a distance, I wired
up a junk ignition coil and appropriate capacitor
using the same circuit as is found in older automobiles.
This way I could strap the coil onto the gun along with a
6 or 12 volt dry cell battery and feed the  low voltage
over whatever distance I wished.  The device works
like a one-legged Tesla coil, imparting a spark pulse
of umpteen thousand volts.   When you close the circuit,
current begins to flow through the coil, building up a
magnetic field which collapses on breaking the circuit.
The suddenly shrinking magnetic field induces the high
voltage in the coil.

You can pick up a coil and capacitor from any auto
salvage  dealer and a lantern battery or two will furnish
a zillion sparks.

The old Model T Ford used a coil with a built in
vibrating switch all mounted in a wooden box.  With a
 6 volt dry cell battery attached to the input, you had a
dandy Tesla coil that would toss out a continuous
spark an inch or so long.  I would guess that one can
still buy these units from antique auto supplies, but they
probably have a hefty price tag.  They used to be in
the Sears catalog.  The unit plus a lantern battery fit
nicely into a cigar box with two stove bolt electrodes
sticking out  ready to ambush the girls.

When I was a kid, they actually taught courses in
electricity in school.  We learned how to build shockers
based on the same principle, using hand-wound coils
which were fashioned into buzzers to produce a steady
output that would cause the hand and arm muscles to
tighten.  Early in the course, the teacher would wire one
of these gadgets to the door of the classroom/lab to
shock the first entrant.  We quickly learned to test the
knob by holding a key or knife to it before risking a
stinging arc to the finger.

The old guy also loved to string a long thin wire over the
chairs of the front two rows to bring everybody to their
feet in a microsecond.  Of course, this only worked one

I don't suppose they teach this sort of stuff in 7th grade
anymore.  Oh yeah, and I bet they don't teach how
to make a magnetic canon that fires steel projectiles
using a pulse of 117V AC.

It's ironic that kids these days get a huge dose of
electronics but seem to learn almost nothing
about electrical and electromechanical gadgets.
That's progress, but the world seems a little
poorer for the absence of spit and baling wire

Jerry (Ico)

Night Runner (Stobl) <> wrote in message
> Hey all,
> I know this technically doesn't have anything to do with explosives,
> but i saw a few"spud gun" questions a while back so i thought it
> wouldn't hurt to ask.  Here's my deal.
> I made a spud gun which i mounted on a tripod. (sort of like a
> cannon).  anyway,  right now im using dry wall screws in the sides of
> the combustion chamber with a gap of about 1/2" with teh spark being
> created by a pizo-electric(sp) grill ignitor. (best setup i could
> find. because of the huge spark)  But this is limited by me actually
> having to hold the gun.  What i want to do is run an extension cord
> from the spud gun about 10-15 feet away, to here i can let little kids
> push the button to make the gun go off.  I tried hooking up the push
> button grill ignitor to the wire but because of the distance, no spark
> emitted between the two screws.  So now im stuck.  I was trying to
> figure out some solution to this but haven't really gone far enough to
> actually do it.  here's what i have so far:
> 1.   hook the wires a couple of 9v batteries.  (i don;t think this
> will work because of the power drain and the fact that that probably
> isn't strong enough)
> 2. Somehow hook the extension cord to some kind of switch which in
> urn, would be connected to a household outlet. (US)  but i was worried
> aobut blowing a fuse or breaker or jsut plainly shorting out the
> house.   Would this work if i jsut conencted a house current to the
> drywall screws with some sort of switch (i have many high power ones)
> blocking the path until im ready for it?
> 3.  I jsut recently took apart an old monitor.  I saved the power
> supply on the circuit board hoping that maybe because that is a high
> voltage power supply i could hook that up soem how.  but bad thing is
> is that i stripped the circuit board of all of its parts and trashed
> it.
> Ok.  So is there some way i can hook this up to maybe a 12v 3amp power
> supply (have one for a cb) or directly to a household outlet?  i'd
> really apprecaite the help as as soon as i can get this working i am
> supposed to bring it to a local school for a demonstration or
> something like that.   I'd REALLY apprecaite any help at all taht i
> could get, with the fact also included that im trying to make do with
> what i have around teh house (no high voltage generators, nothing like
> that.. )
> Thanks.
> Blake..
>                           Stobl (Night Runner)

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