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"Slinky" Primary / Sloped Archimedes Spiral Primary Equation



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From:  John H. Couture [SMTP:couturejh-at-worldnet.att-dot-net]
Sent:  Wednesday, August 19, 1998 12:26 PM
To:  Tesla List
Subject:  Re: "Slinky" Primary / Sloped Archimedes Spiral Primary   Equation


  Bert -

  Thank you for replying to my post. However, it appears that I was not
specific enough with details and you misunderstood my questions. It is true
that changing other TC parameters will certainly change the TC output.

  What I had in mind and referring to your diagram and equations was only
changing one variable and that was the angle "X". For example, if a coiler
had a choice of using a flat spiral or a cone type with R = 3, Z = 5, and
N= 10 turns which should he use to get the best output? The secondary would
be a typical H/D ratio of about 3 or 4. The angle could be anything from
zero to 45 degrees which would require the usual tweaking.

  As I mentioned in my post the cone inductances (Lp) vary only slightly
with angles from zero to about 45 degrees. In fact the differences in this
case are less than 2 uh of the flat spiral inductance. This is less than
the normal wiring connection inductances. With secondary inductance (Ls)
constant the Ls/Lp ratio effect would be very small and within the error of
actual tests. 

  The bottom line is I do not believe it is worth the extra work of
building the cone type primary because the advantages, if any, are
negligible. Do you know of any equations or actual tests that would prove
otherwise?

  John Couture

-----------------------------------------

At 12:07 AM 8/19/98 -0500, you wrote:
>
>----------
>From:  Bert Hickman [SMTP:bert.hickman-at-aquila-dot-com]
>Sent:  Tuesday, August 18, 1998 8:45 PM
>To:  Tesla List
>Subject:  Re: "Slinky" Primary / Sloped Archimedes Spiral Primary  Equation
>
>Tesla List wrote:
>> 
>> ----------
>> From:  John H. Couture [SMTP:couturejh-at-worldnet.att-dot-net]
>> Sent:  Monday, August 17, 1998 2:41 PM
>> To:  Tesla List
>> Subject:  Re: "Slinky" Primary / Sloped Archimedes Spiral Primary  Equation
>> 
>>   Bert -
>> 
>>   These questions came to mind as I was using the equations you show for
>> the TC inverse cone type primary.
>> 
>>   1. What are the advantages/disadvantages of the cone type primary?
>
>An inverse conical primary will couple better to secondaries with a high
>H:D ratio. This is oftne the case for small diameter secondaries (on
>small coils) where H:D ratios may exceed 10:1. However, as we the
>elevate the outer primary turns, we also tend to reduce the standoff
>voltage to the between it and the toroid. For larger 2-coil systems,
>this can become the coil's performance limiting factor, since it leads
>to excessive torroid-to-strikerail hits and excessive corona losses.
>
----------------------  big snip

>-- Bert --