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Re: Formula for Inverted Cone Primarys
Subject: Re: Formula for Inverted Cone Primarys
Date: Thu, 05 Jun 1997 23:05:40 0700
From: Bert Hickman <bert.hickmanataquiladotcom>
Organization: Stoneridge Engineering
To: Tesla List <teslaatpupmandotcom>
References: 1
Tesla List wrote:
>
> Subject: Formula for Inverted Cone Primarys
> Date: Thu, 5 Jun 1997 07:35:25 0400 (EDT)
> From: teslaatamericadotcom (Bob Schumann)
> To: teslaatpupmandotcom
>
>
> Hello,
> A while back someone posted a formula for the
> inverted cone primary to calculate inductance. It
> involved SIN and degree of angle. If anyone could
> repost this formula I would extrememly appreciative.
>
> Thanks
>
> Bob Schumann
> teslaatamericadotcom
> http://www.americadotcom/~tesla
Bob,
Here's a post from back in January that should do the trick...
Subject:
Re: Guide to Primaries rev 1.01
Date:
Thu, 30 Jan 1997 21:28:27 0800
From:
Bert Hickman <bert.hickmanataquiladotcom>
To:
teslaatpupmandotcom
References:
1
Tesla List wrote:
>
> Subscriber: tom_mcgaheeatsigmaisdotcom Tue Jan 28 23:15:20 1997
> Date: Tue, 28 Jan 1997 23:11:20 0500
> From: Thomas McGahee <tom_mcgaheeatsigmaisdotcom>
> To: teslaatpupmandotcom
> Subject: Guide to Primaries rev 1.01
>
> [The following text is in the "ISO88591" character set]
> [Your display is set for the "USASCII" character set]
> [Some characters may be displayed incorrectly]
>
> THE GUIDE: TESLA COIL PRIMARIES
> Rev. 1.01 January 28, 1996
>
<MAJOR Snippola>
Tom,
Looks pretty good to me! Some fillin formulas would also be useful for
the helical, Archimedes, and inverse conical primaries. The helical and
Archimedes forms are from Wheeler, and the inverse conical is a hybrid
closedform that appropriately weights the vertical and horizontal
components of Helical and Archimedes inductances.
All dimensions are in inches, and L is in microHenries. While the
Archimedes calculation is a little "hairier" than the first two, it's
relatively easy to calculate for any desired angle, especially if set up
in a spreadsheet.

Case 1: Archimedes Spiral:
Let R = Ave Radius
N = Number of Turns
w = Width of Winding
 R  N Turns
o o o o o o  o o o o o o
 W 
L = R^2*N^2/(8*R+11*W)

Case 2: Helical Primary:
 R 
 o o
 o o
o o
L o o N Turns
o o
 o o
 o o
L = R^2*N^2/(9*R+10*L) (Vertical Helix)

Case 3: Inverse Conical Primary:
/
\  o
/ o
 o N turns / o
o Z / o
h o / o /
o / o /
 o / o / Angle = X
o \ o /
 o o 

 w  R 

< W >
Z = Coil Width (hypotenuse)
X = Angle of Cone
h = Z*sin(X) Effective vertical Height
w = Z*cos(X) Effective horizontal Width
W = R + w/2 Average horizontal Radius
L1 = W^2*N^2/(9*W+10*h) (Vertical Inductance Component)
L2 = W^2*N^2/(8*W+11*w) (Horizontal Inductance Component)
L = SQRT[(L1*Sin(X))^2 + (L2*cos(X))^2]

Safe coilin' to you, Tom!
 Bert 