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Re: Safety Gap Is Firing Too Much And Too Wide!

Original poster: "Barton B. Anderson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <tesla123-at-pacbell-dot-net>

Hi Nolan,

Tesla list wrote:

> Original poster: "tmoore by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> I have been running my 2.375" coil each run was about 30 seconds .  I
> noticed that every few runs it would just stop, spark gap didn't fire, no
> streamers, just the hum of the neon transformer.

Ok. Just thinking about this only, I would say the total gap width is just
slightly too
wide and could stand to be narrowed some.

>  So I added a safety gap to
> the capacitor.  The cap is a Maxwell rated 35kv -at- 0.03uf , and the safety
> gap is 2 12awg copper wires wrapped around the cap connected on each
> terminal the gap was set at .25" and fired contently.

I would recommend placing the safety gap across the sparkgap instead of
directly across
the cap so there is some primary reactance associated with safety gap
firing. The caps
rating isn't all that high, so you'll want to keep it safe from overvolting
by "not"
opening the safety gap up to reduce safety gap firing. The 12awg copper
wire is more like
a needle gap and at 0.25" spacing should arc at about 5kv. As it is a
needle gap and if
arcing often, will heat up pretty fast thus lowering the arc voltage, thus
firing more

>  My spark gap total is
> set at 0.1875",  3 gaps of 1.125" diameter copper pipe that 3" long.

Ok, about 13kv arc voltage, which sounds about right for a 12 to 15kv supply.

>  So I
> set the safety gap to .5 and then it still fired constantly after that I set
> it to 0.75".  I ran it for about 10 sec and then the safety gap fired a
> couple times about 5 seconds later it would fire contently. I ran it twice
> with that setup and the same thing happened.

Ok, arc voltage for 0.5" is ~5.6kv, and 0.75" is about ~5.8kv. Note, the
needle style gap
here may be the problem. You might want to go the route of brass door knobs
1/2" sphere's set at 1/4" spacing or slightly more). Another neat idea I've
heard some use
is a horn gap which is like a small jacobs ladder configuration. I would
probably use
something larger than 12awg however to increase the ROC.

>  Why is the safety gap firing
> so much with as spacing of 0.75"? Also what is the voltage to breakdown the
> space of .75"?

The arc voltages above were per North, but note I use the approximation
symbol because I'm
not completely sure if the equations I used apply directly to needle gaps.
I think the
main reason your safety gap is firing is due to it's style, in that once it
heats up, it
will start arcing continuously as if it took the place of the sparkgap.
Note, it could in
affect be placed across your sparkgap - the safety gap in this
configuration is a safety
back up in the event there is a problem at the main gap. Note, if you know
your main gap
arcs at X voltage, then you could build a 2-pipe safety gap which has a
little over the
total main gap spacing, which would be a simple way of assuring a similar
arc voltage
characteristic. Also, I recommend air over both to keep the gap(s) cool for

Hope this helps,

> Any tips like to fix this problem cause I think 0.75" for a
> spark gap is over 35kv? Thanks for your Help!!
> Sincerely,
> Nolan Moore