Hi Jared,There is of course a max inductance for an h/d ratio for a given wire length. I did a personal study of this sometime back.
http://www.classictesla.com/download/max_L_table.pdfWhat not everyone realizes is there is that max inductance is not the same for resonant and low frequency inductance.
Your 22g 12"x48" coil would yield 1720 turns. Consider the toroid and primary in place and your nearing about 54kHz, so the frequency "is" low. But due to the high turns, the proximity losses increases as does the dc resistance. DCR is about 86 ohms and ACR is about 177 ohms. This does add up to a lossy coil in the end. I know from experience because I've built one similar except using 24g. I even ran it on pole pig power. Sure it will perform if enough power is put to it, but it does take more power.
The common h/d recommendation of the 5:1 range is not only considering the h/d ratio, but the wire size that fits into that ratio and how that wire size electrically affects impedance.
A coil should be sized for the energy across the gap and the time involved. The transformer of course has to be sized to accommodate the power needed for the cap size and charge rate. The later is far easier.
Take care, Bart Jared Dwarshuis wrote:
For a given length of wire your inductance will be greatest with an inductor that has a large diameter and a short height. However if you make your coil to short you can get problems with flashover from end to end. Wire is reasonably cheap compared to capacitors and NST. Using a lot of wire is the easiest and cheapest way to increase spark length. I would recommend using 22 gauge on a 12 inch by 4 ft concrete form.This will give a nice low frequency and if (when) you upgrade to using more NST (or a pole pig) you will be all set. Finer wire also works and I would not be surprised if one could drop down to as fine as 28 gauge for a pole pig powered coil. But fine wire does not seem to survive strikes very well so we use the thicker stuff as insurance. (tiny wires are hard to wind, they get crossovers easily) Jared Dwarshuis On Dec 14, 2007 12:47 AM, Tim Meehan <btmeehan@xxxxxxxxx> wrote:I hate to ask this too - but what is the optimum aspect ratio for a secondary? I've run JAVATC, and have built a feeble (but pretty) classic tesla before ... and have read but probably poorly understood a few papers. I think that I'm ready to build version two of the static-gap, NST-powered, properly filtered and protected coil. I just want to make sure that I learn as much as possible before I start purchasing things that probably won't suit my needs.
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