Jim,
Thanks for the good information. Yes I remember when I first started this
only 1 gap was firing so I moved the gap that wasn't firing in a hair or so
and they both fire when the voltage is brought up with the variac (or
always on 120vac - no variac). I think I will look into some sort of a
"clear" shell or enclosure tube like area for the fan (and for noise
reduction perhaps) (and maybe cut it down to 1 spark gap) - but will wire
it in series for 2. I will also set the initial gap with just the NSTs when
I get a chance to play with it again at my new garage in a few weeks. I
have usually only ran it for 1-2 minutes at a time so far during my
showings with friends and I haven't seen any adverse effects with the gaps
"glowing red hot". All looks fine - just a couple of big bright lights from
it while running - as expected.
Thanks,
Tim
On Wed, Apr 8, 2015 at 10:59 PM, Jim Lux <jimlux@xxxxxxxxxxxxx> wrote:
> On 4/8/15 7:55 PM, Timothy Gilmore wrote:
>
>> Gary,
>>
>> I found a photo hosting site and posted some pics of the coil early on.
>>
>> http://tdg8934.smugmug.com/Sample-Gallery/
>>
>> The fan is a 120 vac squirrel cage fan blowing on the tungsten spark gaps.
>> However, I don't think its really that strong but I was told this is what
>> was needed so I bought it. I don't have a lot of tools so I'm buying what
>> I
>> can to get it together quickly. The sucker gap you have sounds great but
>> may be too complicated without the experience and materials to do this.
>>
>
> with a narrow gap like you have, there's not a lot of surface area, so you
> need decent air flow. If you have problems (e.g. coil performance starts
> to fall off after a minute or so, or the electrodes glow red), you can
> probably use some cardboard to increase the air speed in the gap area.
>
> I use a parallel copper pipe gap, which has huge thermal area, and a very
> low speed fan keeps it cool.
>
>
>
>
>
>> The gaps on my coil are set about 1/4" or so apart. Using my 130vac 20A
>> variac, it starts sparking on the gaps at about 1/2 to 2/3rds power of
>> 120+vac (to 145vac "measured" max when 20A fuse blows before getting to
>> this).
>>
> The way to set the gaps is to connect just the NST (no primary, no caps,
> nothing else) and set them so they just fire (or don't fire if you're
> braver) at the max voltage you want to run at.
>
> NSTs do not like overvoltage: they're designed for low cost and they don't
> spend anything extra on more insulation.
>
>
>
>> I did not know about how to set the gaps properly (i.e. as you said no
>> caps) from the NSTs.
>>
>> As stated before I am moving in another week or so...so I can't make these
>> changes till next month most likely. I will set the gaps to serial not
>> parallel.
>>
>>
> Parallel gaps are like one gap: one will almost always fire before the
> other, and once it does, there's not enough voltage on the unfired gap to
> fire it.
>
> Series gaps have more loss. If it works ok with one gap, then just use it.
>
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