Re: Triggered spark gaps for coils

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

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-uswest-dot-net>" <jimlux-at-earthlink-dot-net>

I think that this might be a good idea, and is one that I have been
seriously looking at to create a "singing disruptive coil" (rather than my
initial idea of the multi disk rotary gap with different numbers of
electrodes (a'la the Hammond B3 tonewheel), although the harmonic rotary
gap would be a mechanical marvel (if it works)).

 It would allow very precise control of the timing of breakdown.

I think that one of the potential problems would be cooling:  You'd
probably need some sort of airblast cooling of the triggered gap.  With a
rotary, you have the electrodes spinning around which greatly helps the
cooling.

However, sealed high rep rate triggered multigaps have been built,
typically using hydrogen as the gas (in some cases, from dissociation of
methanol).  The ones I've seen described use a series of closely spaced
copper "washers", with the triggering impulse capacitively coupled to
several of the disks in the middle.

An auto coil makes an inexpensive trigger transformer that works pretty
well in these applications.  It certainly has the rep rate and the
necessary insulation.  Some form of triac dimmer drive would inherently
provide a line phase locked trigger source. If you want a fancy drive
circuit, and want to spend a few tens of dollars, a standard electronic
ignition can be triggered nicely from a TTL signal.  I've used MSD 6A's to
fire cannons, etc. under computer control.  I would imagine that the
standard automotive HEI type module designed to work off a magnetic or
optical pickup would work as well, and be virtually free.

V8 running at 6000 rpm = 400 Hz


Tesla list wrote:
> 
> Original poster: "Lau, Gary by way of Terry Fritz <twftesla-at-uswest-dot-net>"
<Gary.Lau-at-compaq-dot-com>
> 
> >From my recent web searches and technical paper readings, there appears to
> be a large variety of commercially available 3-terminal triggered spark
> gaps.  And it seems that these can easily be home-made as well.  These would
> seem to be ideally suited for use as replacements for rotary spark gaps, but
> I've not been able to find any reference to this obvious application.  The
> only reference I've seen towards "amateur" applications is in can and
> quarter shrinkers.  While RSG's do have relative simplicity on their side,
> it seems as though there ought to be some worthwhile benefits to using a
> triggered static gap.  Has anyone attempted this?  Or am I attempting to
> invent a square wheel?
> 
> Gary Lau
> Waltham, MA USA