Re: Spark length equation and pri. program

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Jonathon,

On 27 Jun 01, at 12:25, Tesla list wrote:

> Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<Kidd6488-at-aol-dot-com>
> 
> Hi, all...
> 
> I have been thinking lately about the relationship between spark length and
> voltage. current isn't a factor is it? for example, 12kV can jump about
> half and inch, and 1MV can jump, (guessing here) two yards? I was trying to
> figure out an equation to find max. spark distance by voltage, but haven't
> been able to do so. Someone had to already find it, and I'm probably just
> re-inventing something, but hey, its worth a shot...

In general, you can't judge voltage by distance. Charge availability 
is certainly a factor. Read how lightning works for an idea of what's 
involved. Lightning establishes a connecting path in steps of 100 
metres (feet?) or so. In particular, relatively small distances can 
give some indication of voltage and are a useful indicator of what a 
coil is doing *in single shot mode*. 
 
> Also, I need some guidance on making a primary. It will be a flat spiral,
> using Greg's design with the 7 pipes... I just don't know how many turns
> I'll need. I have a 12/60 NST, MMC will be 11x2 .1uf GG (ggek group), and
> static gap... Is there a simple program to determine turns, and tapped
> turns? Also, I don't know if anyone replied to my post about the
> double-tapped primary, or if i accidently deleted it :-( ... but I'll
> re-post...

You need to know the lowest frequency your secondary is ever likely 
to be made to run at. Then, knowing your primary capacitance, you can 
calculate a maximum inductance your primary is likely to need. There 
are equations for calculating your primary turns based on that 
knowledge in the list archives. My apologies for not being bothered 
to repeat them for the umpteenth time.

Malcolm