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Re: Re. metal case caps

    On the subject of proximity of metallic objects to the primary. I added a
strike rail to my 8" coil, approx. 3" above the primary and it made the coil
totally un-tunable to the point that arcs were breaking out all over the
secondary until I removed the rail. The proximity of a grounded metallic
object severely affected the operation of my coil.
    My question, is there any way to overcome this type of "symptom" when
adding a strike rail?

                Thanks,
                            Jason

Tesla List wrote:

> Original Poster: Gary Lau  11-Feb-1999 0805 <lau-at-hdecad.ENET.dec-dot-com>
>
> >Original Poster: dferguso-at-ebmail.gdeb-dot-com
> >
> >hello coilers- can anyone tell me if metal cased caps are ok to use in
> >close proximity to the primary (like underneath the primary where many
> >coilers place their cap) if it is steel, i take it that eddy currents
> >would be a problem and cause unecessary heating and rob power from the
> >secondary.  how about aluminum or stainless, i am guessing that eddy
> >currents wouldn't be a problem, but wouldn't the mag field of the primary
> >induct into the capacitor case? would the capacitor case be 'seen' as a
> >closed loop, which from what i understand is very undesireable , such as
> >to have a closed loop on your secondary. the reason why i ask is that i'd
> >like to make the case for my cap out of metal, since i am familiar with
> >metal fabrication , the cap would look sharp, and the case would be
> >rugged and leakproof.  the cap would have a plexi top, and the plates,
> >busses,etc would be adequately insulated from any parts of the metal
> >case. any input on if i am missing something would be greatly appreciated
> >- thanks, doug
>
> I don't think there is any problem.  The same situation exists for NST
> cases, and when you think if it, if you take the case off of your cap,
> what do you have?  Metal plates.
>
> I think the issue of eddy currents and other closed loops is often
> overstated.  I performed an experiment related to this once.  I normally
> have a strike rail just above the outermost turn of my primary,
> consisting of a grounded loop of .25" copper tubing with a 0.75" gap
> between the ends.  For grins I shorted the ends with a piece of 20 gauge
> wire and ran the coil.  Performance was visably no different than without
> the short, although the wire did become quite warm.
>
> Gary Lau
> Waltham, MA USA