Re: spark size and JOHN FREAU's FORMULA

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

Original poster: "by way of Terry Fritz <teslalist-at-qwest-dot-net>" <FutureT-at-aol-dot-com>

In a message dated 1/3/03 6:51:45 PM Eastern Standard Time, 
tesla-at-pupman-dot-com writes:

Dan, Paul,

I agree with all this.  Also, the spark lengths do not seem to track
exactly according to the square law.  Larger coils are able to meet the
formula's results relatively easily, whereas very small coils may not be able
to.  I experimented some with more complex formulas using various
roots such as the 1/16 root, etc., in an attempt to make the formula
"track" better.  There's info in the archives about this, but generally
I just consider the formula to be a guide for one to gauge the
"efficiency" of their coil.  It's true that many coils give sparks that
are 50% or less, of what the formula "predicts".

Happy New Year,
John Freau


>For example, in our latest Table Top Competition, the results are as follows
>where max theoretical arc
>length is based upon John Freau's formula:
>
>POWER        ARC LENGTH        MAX. THEORETICAL ARC LENGTH
>143        13"            20.32"
>184        10.75"        23.05"
>152        10"            20.95"
>152        9"            20.95"
>
>As you can see, even in this competition category, these coils are all
>putting out less than 50% of the
>maximum arc length determined by John Freau's formula.  Only the first entry
>puts out slightly more than
>50%.  Of course this data is based upon 4kV tesla coils.  The efficiency of
>coils may increase in proportion
>to the primary voltage etc..., however I do not have data at this time to
>back that assumption.
>
>So in summary, Paul, if I would be very happy if you got your coil putting
>out anywhere over say
>15 inches.  Anything over 20 inches with a 9kV/30mA NST and I'd say you have
>an excellently built coil ! ! !
>
>Good Luck
>
>Dan
>