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Re: Safety gap issues

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

Hi JT,

Your three terminal safety gap should be grounded to the NST chassis. This is what it is trying to protect so it is the voltage of the bushing wrt the NST chassis that is important. The Terry filter (if used) also needs to be grounded to the NST chassis for the same reason. Whether you ground the NST to RF ground or mains ground depends on your setup (where the NST is located wrt the TC and whether indoors or outdoors for example). The safety gap should be set with the TC primary disconnected and adjusted to "just not fire" with the unloaded NST. Once set, dont mess with it. You can now increase the main gap spacing to just where the safety gap doesn't fire too often (static gaps) and you will be set to go. Of course, as always, adjust the tuning with the variac set to low output (say 30-50%) before going to full power.

BTW, three terminal safety gaps are appropriate for two bushing transformers. If using a one bushing transformer, then a two terminal safety gap is appropriate.

Gerry R.


Original poster: "JT Bowles" <jasotb@xxxxxxxxxxx>

Either I have constructed such a safety-perfect circuit, or my safety gap is being dumb.

I added a grounded middle node, and now it NEVER fires.(I think i saw it fire twice in a couple minutes of operation). Whats the deal? I am using my RF ground, the same one attatched to my secondary. I spaced the safety gap JUST over what the main spark gap is set at. So, whats the deal? could by ground be so used up that it is actually repelling a spark in my safety gap?

- I measured , with a ruler, it to be 8000 volts across the Saf. gap.
-my main spark gap is set up at around 7300 volts (also measured with a ruler device)
-my xformer is a 12,000 volt output *should I even worry about this*

Honestly being owned by my coil,
JT Bowles


From: "Tesla list" <tesla@xxxxxxxxxx>
To: tesla@xxxxxxxxxx
Subject: Re: SIZE of RF chokes?
Date: Sun, 20 Nov 2005 16:42:20 -0700

Original poster: "JT Bowles" <jasotb@xxxxxxxxxxx>

YOU SAID
:  "I happen to be the guy who created that formula.  I use 140 volts
into the NST.  This permits the NST to draw more than it's rated
power.  Besides the formula is a guide, not an absolute limit. "


OH, HOLY CRAP. SORRY ABOUT THAT. DIDNT KNOW. Alright then, maybe you can help me in the future, I need to go right now


From: "Tesla list" <tesla@xxxxxxxxxx>
To: tesla@xxxxxxxxxx
Subject: Re: SIZE of RF chokes?
Date: Sat, 19 Nov 2005 17:56:36 -0700

Original poster: FutureT@xxxxxxx

In a message dated 11/19/05 5:25:50 PM Eastern Standard Time, tesla@xxxxxxxxxx writes:


You said:
  "You may be pleased to hear that my TT-42 coil which gives 42"
sparks from a 12/30 NST, does not use any filter.  I just use
safety gaps."

42 inches cant be correct. According to
the......universal......sparklength formula, you should only get a
max of 37"  (  1.7*sqrt inputpower ) in watts )



I happen to be the guy who created that formula.  I use 140 volts
into the NST.  This permits the NST to draw more than it's rated
power.  Besides the formula is a guide, not an absolute limit.


By the way now I hate your guts, considering you're using the exact
same transformer as I, but getting.......3 times more power coming
out. I dont realllly hate you but...you get the idea



Ho, ho,  I see what you're saying.  We'll I'm sure you'll obtain the
performance and safety you're looking for.


With my current system in place, I get 9 to 11 inch discharges to the
air, and when i add a breakout point, pointed at a grounded rod - I
can stretch it to 15.5 inches

thats a total efficiency of about 50%

OK, but using just a safety gap is BS, i saw your site dude. You use
a terry filter. NOt to mention, just because your coil performs good,
doesnt mean it will last forever. I am very happy with 15" discharges
if I could get my coil to last..... 5 or more years. I care less about power.


You're telling me that I use a terry filter? How could you come to that
conclusion? It is a false statement. I don't use any filter on that coil.
It's true my coil may not last as long as it would with a filter. If you're
concerned more about having the coil last a long time and don't
care about getting the longest sparks, that is fine. A filter
won't hurt the performance too much anyway. I'm not telling
you that you should avoid the filter. Filters are fine and very
protective. I was just mentioning that I don't use a filter.

Please don't send me any photos, although I appreciate the
offer.  I just don't have time....overloaded by emails already.

John