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Re: Tuning .....
From: "Barton B. Anderson" <mopar-at-uswest-dot-net>
Mark, great post! This kind of info is useful to the novice, and good for the
old pros too. Thanks for posting. The next coil you build (or existing coil
you
change), might actually hit coulping and misc. right on the nose and still
have
the pri/sec turns lined up. But, make it adjustable (just in case).
Bart
Tesla List wrote:
> From: Mark Finnis <mefinnis-at-medicine.adelaide.edu.au>
>
> Principally for the novices .... like me ;-)
>
> A few weeks back I posted my "first (almost) light" pictures ....
>
> http://www.cobweb-dot-com.au/~dkfinnis/images/second_light_1.jpg
>
> which were encouraging but less than I would have expected for a 6" coil
> and 15 kV at 120 mA (NSTs).
>
> So for the benefit of other beginners/novices these were the changes:
>
> 1. At the suggestion of Malcolm Watts, changed the copper-plated steel
> tube primary for solid copper 1/4" tube. Small increase in spark distance,
> moderate increase in intensity.
>
> 2. Built a new spark gap, as discovered the modified large
> copper-tube/bolt-electrode gap had destroyed itself. This time spent some
> money & bought tungsten electrodes from a TIG welder. Only three pairs as
> this is all they had in stock (can always add more later!). Added these to
> decent heat-sinking and produced current gap:
>
> http://www.cobweb-dot-com.au/~dkfinnis/images/sparkgap_mk5_2.jpg
>
> This produced a *marked* improvement in length and intensity, about 6".
>
> 3. Read various comments on "coupling" on the list, and the relation of
> this to quenching, so thought I'd "de-couple" the secondary, as I had set
> it initially with the secondary base turn = height of primary. I built the
> coil so changing this was easy to do - moved up 1". Amazing improvement in
> spark length. Previous best to earthed ball about 34", now out to 44" with
> regular strikes and previously ignored pieces of the pergola became very
> attractive ....
>
> http://www.cobweb-dot-com.au/~dkfinnis/images/run5_01.jpg
> http://www.cobweb-dot-com.au/~dkfinnis/images/run5_02.jpg
>
> gettin' warmer ;-)
>
> While I had read small differences like this could have a dramatic impact,
> I have to confess I didn't really believe it. So, if your a beginner &
> building a coil - make it adjustable !!!!
>
> Two more improvements planned:
>
> 1. Bigger toroid. (actually arrived yesterday but got dented in transit,
> so is having to go back .... $%%^#-at-$&-at-#^&&& ...... damn! )
>
> 2. Flat plat capacitor. Current cap is rolled P/E with "end-connections"
> and a long roll-length of 3.5m. Still for first pair of home-made caps
> they have endured a heap of punishment !
>
> Cheers,
>
> Mark
>
> http://www.cobweb-dot-com.au/~dkfinnis