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Re: tapered secondary form?



Tesla List wrote:
> 
> Original Poster: "Mad Coiler" <tesla_coiler-at-hotmail-dot-com>
> 
> To all coilers,
> 
> I am [and have been for some time] working on my first large coil, for
> use with my first pole-pig. I had thought I had an ideal secondary form
> but closer inspection reveals otherwise. I borrowed from work two
> plastic rubbermaid trashcans. These appeared to be quite sutable for
> coiling. I just stacked them and realized they have differing diameters
> between the top and bottom of the can. There dimensions are 17" tall,
> 13.5" diameter (base), 14.5" diameter (top). I have two of those. I am
> not sure how this slight angle will effect performance. And if it is ok,
> I was planning on stacking two of them for a ~14"x54" secondary. So
> would it be better if the larger dimaters were together at the middle or
> at opposite ends; for example curved in at the middle or curved out at
> the middle?
> 
> Thanks,
> Tristan Stewart (KC2EBM)
> Get Your Private, Free Email at http://www.hotmail-dot-com

Hi Tristan!

>From an electrical and performance standpoint, it shouldn't really
matter very much which way you go. From a practical perspective, I'd
recommend putting the larger ends at the top and bottom. This will
permit easier mechanical assembly (bottom-to-bottom of the trashcans),
will provide an insulating barrier in the middle of the coil to reduce
the incidence of internal flashovers, will reduce "sliding" of the wire
since any movement will be towards the common midpoint of the coil
instead of the ends, and the larger diameter at the top will reduce
e-field stress. Mounting them the other way would give you an
interesting barrel-shaped coil though!  

-- Bert --