RE: Proper sparkgap for a small coil design

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

Original poster: "Mudford, Chris" <chris.mudford-at-agresearch.co.nz> 

Hi Dr R

And what would you say to a two MOT with doubler producing around 11 kV
at several hundred mA feeding 47 nF MMC powering a 3.5" coil?  My 5 gap
copper pipe gap does not cope well with the heat.

Cheers, Chris (NZ)

-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Wednesday, 11 August 2004 12:26 p.m.
To: tesla-at-pupman-dot-com
Subject: Proper sparkgap for a small coil design

Original poster: "Dr. Resonance" <resonance-at-jvlnet-dot-com>


With a 15 kV 30 mA xmfr, 9 spark gaps would be severe overkill.  The
heatlosses and light losses from all those sparkgaps will "steal" power
that
you want to translate into the sec coil.  Ionizing each of all these
sparkgaps takes power which translates into energy lost.

With either 12 kV or 15 kV, 60 mA xmfrs, we use two gaps of 1/2 inch
dia.
tungsten electrodes fitted into 1.25 x 1.25 brass block to aid cooling &
quenching.  With a 30 mA xmfr a single gap with a large surface area
(hence
the 1/2 inch dia.) will cool and quenching properly.

Dr. Resonance

  >
  > I am new to this and just added a note about the clamps I use and
your
  > reply brings up a question. I just started to make parts for my first
  > coil. The power will be from a 15Kv 30ma NST . I just completed my
spark
  > gap and it is 9 tubes about 4.5 long spaced, .030 . The material is
7/8
  > dia 6al4v Ti ( left over from BMX bike stuff). Was this a bad choice
for
  > material ?? I thought it would hold up well.
  >
  > Rich