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Re: Secondary size


  Mike -

  You are correct in that the maximum inductance for the TC secondary coil
has a 10/9 ratio of radius to winding length with a fixed wire length. You
can find this inductance quickly with the JHCTES computer program. The
program will also indicate this ratio has two undesireable characteristics,
a high volts per turn and a short winding length that could cause
flashovers. With the program you can change the inputs to eliminate these
unwanted conditions.

  You asked if anyone has built a coil with a high radius to winding length
ratio like Tesla's Colorado Springs coil. This was done by Robert Golka in
the 1970's. He told me he got 50 foot output sparks using 150 KW. I did not
ask him if these were controlled sparks!

  The JHCTES does not cover such large coils, but as a test of the program
I show a JHCTES printout in the Tesla Coil Notebook of a coil this size but
using instead only 60 KW. The secondary coil is 50 feet in diameter by 8
feet high with a 6.25/1 ratio of radius to winding length. The program
showed a spark length of 37 feet. The numbers appear to be in the ballpark.

  John Couture

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At 10:04 AM 10/17/98 -0600, you wrote:
>Original Poster: Hollmike-at-aol-dot-com 
>
>In a message dated 10/16/98 5:49:53 AM Mountain Standard Time,
>tesla-at-pupman-dot-com writes:
>
>> Knowing this length you can design a
>>  secondary coil that will give you the maximum inductance without
>>  overloading the power transformer.
>John C.,
>   Based on the Wheeler equation, the maximum inductance of a coil with a
>given length of wire occurs when the radius/winding length is 1.1111(or
10/9).
>That would produce a very short, fat coil that would not necessarily be the
>best geometry for a TC secondary.  Tesla did use coils that were relatively
>short, with a large radius, but I believe he found it necessary to space wind
>the coils to prevent excessive voltage stresses between the turns.
>   Has anyone built a coil with such a geometry?  If so, how did it work?
>MIke
>
>
>