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Re: spark gaps


>Date: Wed, 16 Oct 1996 19:39:16 -0500 (CDT)
>From: Mike Hammer <mhammer-at-midwest-dot-net>
>To: tesla-at-pupman-dot-com
>Subject: spark gaps
>
>Hello all,
>
>In my never ending quest for more power and longer spark
>I have come to a bottleneck. I believe the gap is now my limiting factor.
>Running at about 1.2 KVA I notice that as I run the variac up towards
>maximum the spark output actually decreases slightly. I believe that the
>gap may not be quenching well as I turn the power up.
>
>I have built an 8 electrode cylinder gap similar to the design
>from the funet archives. The 7 gaps are set at .025 inch for a total of .175
>inch.
Mike,

I'll let Richard comment on this.

>I used 3/4 inch copper tubing and a piece of 4 inch PVC to house it.
>A small muffin fan provides air for cooling. (I'm a use what I got kind of guy).
>
[snip]
>3. I have seen references to vacuum gaps in the archives but very few details.
>   Could somebody who has built one give some details and what kind of results
>   were obtained. 
>
Check out 

	Surplus Center
	1015 West "O" Street
	P.O. box 82209
	Lincoln, NE 68501-2209
	800-488-3407
	402-474-4055
	402-474-5198 (fax)

on page 121 of the '96 catalog:  Item: 16-1048 is a 60 CFM 115V blower

	115 VAC
	3450 RPM
	1/9 amps
	5 stage blower
	18" H2O vacuum at 0 CFM
	60 CFM open outlet
	10" dia by 10"
	18 lbs.

	$18.95 U.S.D. plus shipping;( not to bad.

IT's quite! I've used one for 2 years for a shop vac when I'm not
blowing my gap;) It will really quench your gap.



>4. The message I get from the list archives is that rotary gaps are not 
>   for neons. The message is loud and clear that using a rotary on a neon
>   is inviting transformer failure. Why? What is it that promotes a failure?
>   I'm not likely to build a rotary anytime soon but would like to know just 
>   the same.
>
Mike,
	Think about a static gap: it's just sitting there waiting for
the voltage to rise above it's breakdown voltage (10KV - 15KV) ... The
voltage across the neon will not exceed this value.

NOW think about a rotary gap. It is NOT just sitting there waiting for
the voltage to rise above it's breakdown voltage........ No, it's
rotating; and changing it's breakdown voltage, to many hundreds of KV
at max spacing. So the voltage across the neon will rise, to the
neon's output voltage times the "Q" of the neon's leakage inductance/
primary cap, to the breakdown voltage (100KV??) of the rotary gap.
Eventually, the phase of the "resonant voltage" and the rotary's
breakdown voltage will max ( at several hundred KV) and the poor neon
will blow.

	jim