Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!mailrus!uunet!isc-br!jimc
From: jimc@isc-br.ISC-BR.COM (Jim Cathey)
Newsgroups: sci.electronics
Subject: Re: Spark Coils
Message-ID: <2885@isc-br.ISC-BR.COM>
Date: 9 Jul 90 21:16:44 GMT
References: <9007032018.AA27882@ucbvax.Berkeley.EDU> <2082@electro.com>
Organization: ISC-Bunker Ramo, An Olivetti Company
Lines: 51

In article <2082@electro.com> eric@electro.UUCP (Eric) writes:
>Oil furnace transformers can apparently give 50kv sparks and up
>while car ignition types give 35kv.  To get some real sparks you
>...
>  Note: oil burner transformers are very dangerous.  I have had
>  pulled muscles, burns and bruses from being thrown.

They are nasty, at that.  I made a Jacob's ladder out of one once (in my
misspent youth) that wasn't too impressive as a ladder, but it would start
on fire a piece of paper placed in the arc!  'Real' ladders have much less
current and will merely perforate paper placed in the arc.

Sometime later, we had some problems with a steer that would just walk
through the electric fence (he twitched a little, but it didn't stop
him) and get into the barn to pull down the haystack at night.  Pissed
at having to fix the fence every day and clean up after this critter I
'enhanced' the electric fence.  (The fence in question was a short
temporary section we had put up for the summer.)  

I disconnected the temporary fence from the rest of the fences, and got
out an old electric fencer.  This fencer used a rocking mercury switch
to intermittently supply line current to a HV transformer.  I tapped
off the primary of this transformer and ran this power to the primary
of my oil transformer.  The secondary went to the fence.  Powered up
the fence -- nothing.  Looking into matters I found that the new fencer
burned through all the plastic fence insulators and shorted out to the
metal fence posts.  Grumbling that it mightn't be easier just to _shoot_
the damned steer I replaced all the insulators with porcelain ones.

Success!  I went into the barn to watch.  After I was out of sight for
a few minutes the steer came up to go under the fence as was his usual
habit.  He got halfway under when the charge hit him (the mercury
rocker was slow).  GRAWWWWWWWW, he fell to his knees, scrambled
backwards and ran extremely fast to the other end of the field.  He
didn't come close to the barn for days!  End of problem.  I left the
killer fencer up for a few days just in case, then restored things
to normal.  One nice artistic effect was the pretty purple glow around
all the insulators at night!  Nasty stuff, that HV.

In retrospect, I'm lucky I didn't kill the steer, though I doubt I
would have been heartbroken about that by that time -- _Dad_, on the
other hand...  

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! II      CCCCCC !  Jim Cathey
! II  SSSSCC     !  ISC-Bunker Ramo
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