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Re: [TCML] Are safety gaps necessary?

Hi David,
The TCML is place for advice and also for general discussion. My safety gap comments are only a discussion and I don't advise anyone to consider increasing the safety gap unless it's really firing way too often and your certain the main gap is set properly. And I certainly don't advise removing it, but it's just a consideration for myself I'm thinking about (and only thinking about at this point). A better alternative for most is to actually reduce the main gap a little. 
As far as strike rails, I have had strike rail hits and primary hits 
using them. I experimented long ago just removing the strike rail and 
although I did have a few primary hits, there were far less. This was a 
big 13" dia. coil. Spark control and power is real consideration here. 
If there's just enough power to reach the primary, then you can get 
quite a few hits. Power needs to be high enough to send those sparks out 
and away and a nice large and wide toroid helps (as does a nice compact 
primary). The ring can be a target of sorts. But none of this is written 
in stone.

My personal feeling is that there may be coils better off with a strike 
ring and coils better off without them. Field control, power, bps, 
primary, height, etc.. all play a role in the sparks character. The idea 
is to minimize primary strikes. One needs to experiment with their own 
system to find out what minimizes primary hits. If you find more hits to 
the primary without a strike ring, then add a little more power, change 
bps, etc.. experimenting to reduce them to almost nothing. Then try the 
strike ring again and compare.

Although I may state my experience, I won't advise anyone to simply 
remove a strike ring (at least not these days). My advice is that on 
this subject, coilers should certainly experiment with field control 
changing power, bps, toroid heights, size, etc.. Size is difficult 
unless you have a few toroids around, but the rest can be altered 
easily. These things affect the sparks characteristics (length, time, 
direction, dissipation, etc.). And they should do what works best for 
their coil.

Take care,
Bart

David Nelson wrote:

Gary, Bart, all.


Given the advice of this list, I have set my safety gap (on a static 
spark gap system) and when the coil is running I get occasional firing 
of the safety gap, about 5 or 10 per minute. I was thinking this is 
all good and it does give me a certain peace of mind. Now given this 
latest discussion I am starting to think that I should be opening my 
safety gap out more. BTW I have a strike rail which does get hit 
occasionaly and it seems that the primary is very inlikely to be hit 
with the strike rail in place.

Dave Nelson
----- Original Message ----- From: "Lau, Gary" <Gary.Lau@xxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Wednesday, June 18, 2008 10:05 PM
Subject: [TCML] Are safety gaps necessary?


I changed the Subj: line to reflect the topic...

Way to stir the mud, Bart!  It's good to make us examine our practices.


I thought about your post quite a bit.  Yes, it does seem hard to 
justify a separate static safety gap that is in parallel with the main 
static gap.  I think we've had to do some hand waving and wiggling 
when we describe to newbies the procedure for separately setting the 
main and safety gaps.  And I fully agree that a static gap is 
extremely unlikely to fail in the way that an RSG might.  So I was 
about to join the heresy and agree that safety gaps appear to be 
redundant and unnecessary with a static gap.

I slept on it and it dawned on me this morning.  What happens when a 
streamer strikes the primary?  If one exists, the 3-terminal safety 
gap fires, channeling the streamer's energy safely to RF ground.  If 
one didn't have a 3-terminal safety gap, the only path for that 
streamer energy is through the NST.  I think the NST would be happy 
that the 3-terminal gap exists!

So I stand by the advice to use a 3-terminal safety gap.

Regards, Gary Lau
MA, USA


-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
Behalf Of bartb
Sent: Tuesday, June 17, 2008 8:53 PM
To: Tesla Coil Mailing List
Subject: Re: [TCML] Chokes and Terry filters

I think all of us are preaching proper gap spacing via NST and gap
setting (workbench approach) which eliminates the various electrodes
chosen. Another aspect to consider is that DC typically runs at about
1.3 x Cres for his cap size. So he is taking advantage of some resonant
charging as far as bps is concerned. The static gap still clamps the
voltage regardless and I agree is the main problem with NST failures.

If I were to weigh in on the filter discussion, I would say the chokes
are unnecessary with a filter. However, I have even pushed my gap
setting wide enough to kill an NST even with a Terry filter installed.
This is when I realized the safety gap was useless due to my gap setting
and sort of what drives me to stress the margin between safety and main
gap needs to be large enough to allow the safety gap to work, otherwise,
it's just a waste of labor and electrodes.

I do push my transformers with what I can get away with. If it fails,
I'll just fix it or replace it. There are probably a few like me out
there on that subject. With that in mind, I've even been thinking about
doing away with the safety gap (my static gap coils only). The reason is
I have little margin and it's an annoyance when set correctly and
useless when it's not an annoyance.

The fact is, the probability of a decently built static gap failing is

slim to none. So, what's the point of the safety gap in that type of 
system?

Take care,
Bart

Lau, Gary wrote:

> Indeed.  I think the reason that DC has been successful in not 
killing > NST's is his
conservative approach to keeping static gap width small.  That, more 
than using
any kind of filter, is the key to long NST life, and that's what we 
should be
preaching.  But human nature being what it is, the desire to increase 
performance
has us opening the gaps to the max, and that's where Terry filters 
become useful.

>
> Regards, Gary Lau
> MA, USA



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