Re: Triggered gap and safety gaps

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

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


>  I planned a tungsten carbide static gap and was on the verge of building 
one
>  when the triggered gap project caught my attention. On the surface it seems
>  so simple and it probably is. Except, initial setting and setup has me
>  concerned.
>  
>  An now you say it is easy to lose your NST? Help.
>  My basic multi-segment static gap has a total width of .28
>  I have a safety gap set for about .3 with Terry's MOV array.
>  And finally, with a 15/60 NST, I have an MMC of .0117, slightly LTR.

Ted, all,    (a long-winded response follows... ho ho)

Regarding my concern about NST safety using the triggered gap,
these concerns would be basically the same as the concerns
when running a sync gap at 120 bps.  I used to use matched
sized caps at one time for my sync gap systems, and although
I had no failures, it does seem safer to use LTR caps, because
the peak voltages are lower, and resonant build up cannot occur.  My
reasoning is that any 120 bps sync gap will stress the NST
a little more than a static gap, especially during initial phasing
of the rotary.  This is because a static gap will always fire if
the spacing is not too wide, but a sync gap has a "wider spacing"
in the sense that the gap cannot fire until the electrodes rotate
nearly into alignment.  The actual gap spacing of a sync gap
should be set narrow of course.  To get the most out of an NST
using a matched or resonant sized cap demands that the safety
gaps are set wide.  If you're willing to obtain less than the max
output spark lengths, then yes, the safety gaps can be set
narrower, and the NST will be protected.  Another way to say
this, is that with a matched size cap, one should not strive to
obtain max spark length from the system, but using LTR caps
one can more safely extract max spark length from the system.
The same precautions apply to triggered gap systems which
are similar to sync gaps in the sense that they must wait for
the trigger pulse to initiate firing.  If one is careful to be sure the
trigger pulse is there when it should be (phased correctly), and
it fires, and the safety gaps are not too wide, and one tolerates
less than optimal output spark length, then one can get
away with matched size cap operation.  But LTR operation is
safer.  It's safer for static gap operation too, because the gaps
can be set narrower for less NST stress.

>  
>  If I initially set the main electrodes of the trigger gap to, say, 1" 
apart,
>  the safety gap should fire, yes? 

Yes,

> Then, with the dimmer set midway, I
>  energize the trigger electrode which is barely in the path and midway
>  between electrodes. That should precipitate the main gap to fire...correct?

Yes, depending on the safety gap setting.
>  
>  Or, should I start with the main gap rods closer...say 1/2 inch.

As long as the safety gaps are not too wide, they should protect
the NST under any condition, in theory anyway.  In any case, true
LTR operaton permits the use of narrower safety gap settings for
a given spark output, so it's safer in all cases for any gap type.
Your cap is probably close enough to the matched size to be
considered a matched size.  I ran my coil for years with a 120 bps
sync gap, with a matched cap, and only safety gaps set at 1/2"
on each side of a 12/30 NST for protection, and I've had no failures.
Others have not been so lucky I'm told.

>  
>  I cannot afford to lose the NST so casually at this time frame so I want to
>  take whaever precautions are suggested to setup this new approach.
>  Marc has certainly been a big help.
>  But the initial setup process has been a stubling block and maybe you have 
a
>  simpler interpreation I can follow.

I've never used trigger gaps, and my ideas are based on general
matched vs. LTR precautions, etc.

John Freau

>  
>  Much obliged for any assistance.
>  
>  Ted
>