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JHCTES TC Program (was Round vs flattened primary tubing)



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From:  Bert Hickman [SMTP:bert.hickman-at-aquila-dot-com]
Sent:  Saturday, June 13, 1998 12:43 AM
To:  Tesla List
Subject:  Re: JHCTES TC Program (was Round vs flattened primary tubing)

John and all,

My comments are interspersed below...

Tesla List wrote:
> 
> ----------
> From:  John H. Couture [SMTP:couturejh-at-worldnet.att-dot-net]
> Sent:  Friday, June 12, 1998 7:27 PM
> To:  Tesla List
> Subject:  Re: JHCTES TC Program (was Round vs flattened primary tubing)
> 
<SNIP>
> >Steve,
> >
> >There can be a significant advantage! Let's build a pancake style
> >primary from 3/8" copper tubing with 1/4" clearance between turns. Let's
> >also specify an inner diameter of 10", and a maximum outer diameter of
> >25".
> >
> >3/8" round tubing:
> >In order to have 1/4" clearance between turns, we'd need a turn-turn
> >spacing of 5/8". This limits us to a primary with 14 turns, resulting in
> >about 72 uH of inductance.
> >
> >Flattenned 3/8" tubing:
> >Now lets make a primary using the same tubing that's been pre-flattenned
> >to form a copper "strap" that's approximately 1/2" wide by 1/8" thick.
> >Using this material, we can decrease the turn-turn spacing to 0.375"
> >while still maintaining 1/4" clearance between turns. We can now fit 20
> >turns in the same space, resulting in a primary with about 201 uH of
> >inductance, or about 2.8X the inductance!
> >
> >-- Bert --
> >
> --------------------------------------------------------------
> 
>   Bert, All -
> 
>   I get 12 turns instead of 14.  (25 - 10 = 15/2 =7.5 inch width of spiral
> turns
>   7.5 / 5 / 8 = 12 turns (72 mh)    7.5 / .375 = 20 turns (201 mh)
> 

Yep! I agree - I got the right inductance, but the wrong number of turns
- 12 is correct! That's what I get for trying to do calculations before
having my coffee in the morning... :^)

>   I ran the numbers thru the JHCTES program and found that the 20 turns of
> flattened tubing would apparently not make a practical Tesla coil because
> the inductance is too great. The secondary coil would be too large to fit
> the primary. 

John, this may in fact be true. The example I gave was really intended
to demonstrate that there was a significant improvement in the amount of
inductance you'd obtain. 

However, I seem to remember John Freau holding the current record for
streamer length versus input power while using a primary having even
significantly more than 20 primary turns. One might choose to use a
higher primary circuit voltage (1.66X) with the smaller cap to obtain
comparable energy per "bang" while increasing primary Zo high to reduce
I*E gap losses. Performance may actually turn out to be better in this
case... 

<SNIP>
> 
>   The advantage of the JHCTES program is that all of the
>   parameters can be varied to find many "what if" combinations.
>   Many coils have been designed and built using the
>   JHCTES program and they have all worked properly.
> 
>   Other combinations are possible but appear to present
>   problems. A larger toroid? Smaller sec wiring, etc?
>   Coilers who have the JHCTES program may want to try
>    other combinations.
> 
>   Any comments?
> 
>   John Couture
> 
> ------------------------------------------------------