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Re: Size DOES matter?

Original poster: Steve Conner <steve@xxxxxxxxxxxx>

At 23:16 02/06/05 -0600, you wrote: 
I cant say i know of any good reason why a small
coil cant be pushed to produce sparks maybe 5X its secondary length,
but it just doesnt happen that way.

Well surely there is a limit. 5x maybe, but you wouldn't expect 50x or 500x! Why? Malcolm Watts and I seem to agree that it's all down to the electric fields. A small coil bunches all the field in close to it, a big one spreads it out further so it can grow streamers over a bigger area.

If we took the analogy of a farmer's field, a big coil spreads the "fertilizer" out all over the field but a small one dumps it all in a pile in the middle. Which one do you think will grow more taters by the end of the season ;)


I am a bit surprised that you only got 33"... my coil which is
slightly smaller does 36"

Aw come on! That 3 inch difference isn't statistically significant ;)))) If I had waited 5 minutes I probably would have got 36".


>looks like that "brick wall" from the old days of 
untuned-primary SSTCs has returned, except now the sparks are much
longer than before :-).

Well if what we are saying is true, the brick wall is a limit that any coil design will run into and the only way round it is to make the resonator and toroid bigger. I remember Malcolm Watts talking about it in the past so maybe we should call 3x your secondary length the "Watts Limit" or something ;) John Freau's famous research coils that set the efficiency benchmark had a "Watts Number" (=spark length/secondary length) of about 2.2.

I wonder what sort of a performance number you get if you multiply the Watts and Freau numbers together?

=(Spark length/secondary length)*(Spark length/sqrt(power))
=(Spark length^2)/(secondary length*sqrt(power))

So it brings in a "wow factor" for producing big sparks from a small coil, that offsets against the efficiency penalty of doing that.

Conner, Steve