Re: Safety Gap Firing

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>

Hi Dennis,

Upon rereading your post, I realized that I answered a slightly 
different question than what you asked..

Your main gap probably has different geometry (like parallel pipes 
forming the gap) than the brass balls forming the safety gap.  As a 
result, for a given potential difference across the balls, there will 
be a greater E field stress than the same potential difference across 
a pair of parallel pipes with the same gap distance.  So, comparing 
gap distances betweent the two is sorta like comparing apples to 
oranges.  The bottom line is the safety gap fires before the main 
gap.  So, if the safety gap is properly set (and I believe it is from 
what you described), then your main gap need to be reduced.

Gerry R.


> Original poster: otmaskin5@xxxxxxx
> I'd sure appreciate some advice on this problem.  My coil seems to 
> run fine as I dial up the variac, but as soon as it hits the 110 
> volt setting, the safety gaps start firing.  I've reverified the 
> optimal primary tap point, so hopefully I've got the tuning right.
>
> Here's some info on the coil that might be helpful:
>    * 15/60 NST with a 35kv/0.03 uF Maxwell pulse cap
>    * spark gap - air-cooled segmented pipe - 6 gaps @ 0.03" each - 
> 0.18" total
>    * safety gap - 3 brass balls (1/4" dia.) - 2 outer balls 
> connected to the NST terminals & center ball to ground.  The 
> hot-to-ground gaps are 0.130" or 0.26" total.  This was the setting 
> at which the safety gaps just wouldn't fire with only the variac & 
> NST hooked up
> It doesn't make sense to me that the safety gaps can fire when the 
> spark gap separation is greater.  Any help for a struggling semi-newbie?
>
> Dennis Hopkinton MA