RE: Static Spark Gap question

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

Original poster: "Lau, Gary" <gary.lau-at-hp-dot-com> 

It is commonly assumed that a multi-segment N-segment gap of X inches per 
segment will have the same breakdown voltage as a single (N*X) inch 
gap.  This is not at all true.  The only way to determine the proper number 
of gaps in a multi-gap is to do so experimentally.

What's wrong with applying 140V to an NST through a Variac?

Gary Lau
MA, USA



Original poster: "WIZZARD ." <pbobyk-at-hotmail-dot-com>

Apply the 15KV accross a safety gap and adjust it so it "just" stops arcing.
Remove power, then measure the opening of the safety gap.
Divide this number by the number of gaps between your pipes.
Pipes should be installed as parallel to each other as possible. Each gap
doesn't have to be perfectly spaced unless you really like that appearance.

More pipes means less space in between each pipe.
Small gap spaces get clogged and/or shorted by surface irregularities on
the pipe usually in a short period of operation time. Overall coil
performance suffers. ( Fine sandpaper time )

My NST 15KV/120mA NST powered coil uses a RQ gap with 10, 3/4" Cu Pipes
about 4.5" long.
A good circulation of air through the gaps is needed for this power level.

Tips to avoid dissapointment :-)
         1) Don't make the main gap larger than the safety gap.
         2) Don't use a mains resonant capacitor.
         3) Don't apply 140 VAC to NST through a variac.
         4) Use a Terry Filter!

Members correct me if I'm wrong.












 >Original poster: "Gerry Reynolds" <gerryreynolds-at-earthlink-dot-net>
 >
 >Hi All,
 >
 >I'm building a 15kv 120ma coil system and want to start with a
 >multi-segmented spark gap.  I know that Dr R doesn't like total spark gaps
 >in excess of 240 mils but I do plan on setting my safety gap appropriately
 >and leaving it alone.  I'm planning on a 16 pipe string with each copper
 >pipe being 3 inch long by 0.625 diameter.  Three gap spacing arrangements
 >are being considered that will allow me to vary the total gap in 5 mil
 >increments.  This will be done by having the center gaps be of smaller
 >spacing than what the string is based on.  The smaller gaps will be
 >shorted out (as necessary) in various combinations to get the 5 mil
 >increment.  The following shows the smaller gaps in the center of the
 >string based on 20, 25, and 30 mil spacings:
 >
 >a. 20 mil spacing   .... 20 10 15 20 ....            maximum total gap 285
 >mils
 >b. 25 mil spacing   .... 25 10 15 20 25 ....       maximum total gap 345 mils
 >c. 30 mil spacing   .... 30 15 20 25 30 ....       maximum total gap 420 mils
 >
 >Questions:
 >
 >1. For this power level, what is the current thinking on maximum number of
 >segments?
 >
 >2. Is there a rule of thumb on the maximum gap between any two segments?
 >
 >3. What is the "expected" optimum total gap required for this power source
 >and how much would this need to be increased for my 5000 foot elevation?
 >
 >Answers to these question will help me identify a design center and choose
 >an appropriate spacing range.
 >
 >Many thanks for any help,
 >
 >Gerry R
 >Ft Collins, CO
 >