Triggered gap

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>" <Hhchicken1-at-aol-dot-com>

Hi list! 
I have decided to make a triggered spark gap to replace my current 'vice and 
a nail'.  I thought I'd better post to the list before I fry myself... 
For the initial tests I will be using a NST labelled 6/35, although it seems 
to be able to jump a gap of more than a centimeter (!). For the gap 
electrodes, I am using the Earth pins from UK mains sockets - I believe they 
are made of copper, and they are much more substantial than the US variant.   
I have set two of them up at a distance where the NST with tank cap attatched 
will not bridge the gap, and have placed a third trigger electrode in the 
middle, offset by quite a large amount, so the gaps between any two 
electrodes are about equal.  With the NST and tank cap (no primary), this 
does not fire. 
For the trigger, I am using a car ignition coil powered by a dimmer switch 
and 3uF cap direct from the 240v 50Hz mains.  This produces (at a guess) 
around 40kV and when fired across a gap produces a tone that sounds quite 
like 50Hz.  I am all set to connect this to the main gap, but am unsure how 
to safely do it.  As the ignition coil is an autotransformer, if I connect 
the HV out from the coil to the trigger electrode, and the minus terminal on 
the coil (which is also connected to my dimmer) to one of the other 
electrodes, surely I will be almost directly connecting the HV from my NST to 
my dimmer switch?  Another problem is that my NST is not grounded, I realise 
that this is a must and will do that before I try anything. 

Thanks for any help you can give me - a schematic would be handy hint hint :) 
Henry Hallam