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Path: utzoo!linus!philabs!cmcl2!seismo!umcp-cs!cvl!umd5!zben
From: zben@umd5.UUCP
Newsgroups: net.analog
Subject: Re: Jacob's Ladder
Message-ID: <554@umd5.UUCP>
Date: Sun, 2-Jun-85 22:53:07 EDT
Article-I.D.: umd5.554
Posted: Sun Jun  2 22:53:07 1985
Date-Received: Tue, 4-Jun-85 08:06:56 EDT
References: <72@biomed.UUCP>
Reply-To: zben@umd5.UUCP (Ben Cranston)
Organization: U of Md, CSC, College Park, Md
Lines: 34
Summary: Some tips

In article <72@biomed.UUCP> lagasse@biomed.UUCP (Robert C. Lagasse) writes:
>      I have tried building a Jacob's Ladder using a 2-transistor oscillator
>feeding a T.V. flyback transformer but I have had problems with it:
>...
>        2) The H.V. arc produced wants to stay small in length.  That is, it
>does not want to climb up the rods and lengthen and finally break away
>unless I blow on the arc with an airstream (really!).  

Mine is a 12 KV neon sign transformer with coat-hanger-wire electrodes.
The bottom gap is about 1/2 inch and the top gap about 5 inches.  The major
causes of "hanging up" I have seen in almost 20 years of experimentation:

1. Too much "slope" - the electrodes separate too quickly.  The effect of
   a Jacob's ladder is caused when the hot air generated by the spark rises.
   As hot air is easier ionized than cold, the arc will rise with the hot air
   but if the slope is too much the effect of the electrodes separating will
   swamp the hot air effect and the arc will stay at the bottom.

2. Electrodes not straight.  If the electrodes have little bends or knees in
   them the arc will tend to hang up at that point.  The finest ladder I have
   seen was at the Ben Franklin Institute in Philadelphia, PA.  Their 
   electrodes were perfectly straight and nearly four feet long with a very
   gentle slope - the arc took literally 6 or 7 seconds to go the distance.

My advice to you is to rework your electrodes.  Make sure that they are as
straight as possible, with a gentle slope (15 degrees or less) and find out
exactly where the arc is hanging up.  Examine that point.  If there is a 
bump of metal or anything there, FILE IT DOWN!  Sharp points give off arcs
much more easily than flat areas.  (Yes I know why, but it's too involved to
try to explain it here).

Good luck, and remember, this kind of electricity can kill!
-- 
Ben Cranston  ...{seismo!umcp-cs,ihnp4!rlgvax}!cvl!umd5!zben  zben@umd2.ARPA