Re: Secondary size

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

Original poster: FutureT-at-aol-dot-com 

In a message dated 1/16/04 11:32:33 AM Eastern Standard Time, 
tesla-at-pupman-dot-com writes:

>John:
>OK maybe I missed some of what you were telling me out of frustration
>from all the just do this answers.
>
>I know this is not a formula per say but it is nice to have a response
>with examples and then an observation of those examples that makes some
>sense.
>Thank you for the input.
>
>And thanx for humoring me and my relentless questioning on the subject.


No problem.   Also I forgot to mention that the heights I mentioned are
near *minimum* workable heights based on experience, although
I guess that could have been deduced from my comments.  I don't
recommend using a height that close to coil breakdown.  For
example for a 42" spark at 120 bps, I generally use a coil from
19" tall to 24" tall.  For a 15/60 NST I'd probably use a 6" x 27"
tall coil at 120 bps.  Much of these height decisions, etc., are based
on practical knowledge of what produces a good, well behaved,
reliable coil.   Also if the coil is too short, sparks are likely
to strike down and hit the primary.  At which height this occurs
will depend on many factors for a given input power...  Factors such
as toroid diameter, primary diameter, toroid height, breakrate, etc.
Some folks may prefer that the sparks hit the primary at times,
if so then that must be taken into account also.

John



>Luke Galyan
>Bluu-at-cox-dot-net
>
>-----Original Message-----
>From: Tesla list [mailto:tesla-at-pupman-dot-com]
>Sent: Thursday, January 15, 2004 6:42 PM
>To: tesla-at-pupman-dot-com
>Subject: Re: Secondary size
>
>Original poster: FutureT-at-aol-dot-com
>
>In a message dated 1/15/04 10:28:26 AM Eastern Standard Time,
>tesla-at-pupman-dot-com writes:
>
> >Original poster: "Luke" <Bluu-at-cox-dot-net>
> >
> >Ok lets say the break rate will be 120bps
> >The power input will be 900watts (15KV -at- 60mA)
> >The expected spark length is 50"
> >How does one choose a secondary height from that?
> >Please do not just tell me what height to make it.
> >I want to hear WHY.
>
>
>As can be read from my comments below, the coil would be
>basically proportional in length.  The sparks in the example below
>are 2.56 times the coil length.  Using this same proportion
>would give us a secondary 19.53" tall for your proposed coil
>example above.  The length to height ratio keeps this proportion
>to keep pace with the voltage involved for the particular spark
>length.  This proportion was found to be suitable at 120 bps
>based on various coils I've built.  Actually I was able to push
>the sparks to 60" using the 23" tall secondary, but occasional
>racing sparks occured, so I was pushing things too far at that
>point.  If a very large or very small coil is built, the proportions
>may be different, I'm not sure.  Actually I just remembered I built
>a smaller coil using a 12" tall secondary and was able to get
>34" sparks before breakdown, so this does give a similar proportion.
>
>Please understand that these ratios, etc., are approximate
>figures.
>
>John