# Re: Another formula to throw on the fire

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From: 	D.C. Cox[SMTP:DR.RESONANCE-at-next-wave-dot-net]
Sent: 	Thursday, December 11, 1997 6:57 PM
To: 	Tesla List
Subject: 	Re: Another formula to throw on the fire

Great idea!  It's an equation I have never seen in print before.  One
question:  Is the radius measured from the center of the circle??  Not sure
what you mean by center of the tubing?

DR.RESONANCE-at-next-wave-dot-net

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> From: Tesla List <tesla-at-pupman-dot-com>
> To: 'Tesla List' <tesla-at-poodle.pupman-dot-com>
> Subject: Another formula to throw on the fire
> Date: Thursday, December 11, 1997 8:13 AM
>
>
> Sent: 	Wednesday, December 10, 1997 9:57 PM
> To: 	tesla list
> Subject: 	Another formula to throw on the fire
>
>
> I computed a simple integration for finding out how much tubing or wire
> is need for a primary coil that may be of use to those building coils.
> The formula is as follows:
>
> For a flat (or slightly banked) spiral primary coil of:
>
>      Outside (final) radius of Ro (Both Radii measured from the center of

> the tubing)
>      N number of turns
>
> The total length of wire/tubing (L) required is:  pi * N * (Ro + Ri)
> Pretty simple end result, eh?  Independent of units chosen too, as long
> as you are consistant of course!
>
>
> ---------------------------
> For completeness, here is my entire calculation:
>
> The integrand was radius as a function of Theta:
>
> R = (W/2pi) * (Ro - Ri)/N + Ri    where W is Theta in Radians
>
> Integrating the radius this over all 2*pi*N turns (henceforth 2piN) we
> get L:
>
>       _ (2piN)
>      /
> L = / [(W/2pi)(Ro - Ri)/N + Ri] dW
>   _/
>     0
>
>
> L = [(Ro - Ri)/2piN] * [(2piN)^2/2] + 2piN*Ri
>
>
> L = piN(Ro-Ri) + 2piN*Ri
>
>
> L = piN(Ro-Ri)    [Q.E.D.]
>
>
>
>
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