# Re: Tesla Software

```Hi Mark,

>        The basic formula for a flat spiral can be found in the funet
>archives in the file math.txt.  A flat spiral can be constructed out of flat
>ribbon (a la aluminum or copper flashing) or using soft copper tubing.  The
>latter is perhaps a little more popular.  Although a correction for the
>tubing thickness can be employed, the crude formula gets you close enough
>experimentally.

Right. I don't think anyone is looking for 99.9999% accuracy. This software
is intended to get things in close proximity to a functioning setup. There
will ALWAYS be fie tuning necessary.

>        People also construct primaries as solenoidal coils, and/or as
>inverted conical (inclined, also called "saucer") coils.
>        Wheeler's formula works fine for a solenoidal primary coil.
>        For an inclined flat spiral, I estimate the inductance in the
>following manner:  Assume one has a coil with inner diameter D1 and outer
>diameter D2, with the outermost turn elevated H inches above the innermost
>turn, with N turns.  Compute inductance L1 using Wheeler's formula for a
>solenoid with diameter D=(D1+D2)/2, N turns and height H.  Next, compute
>inductance L2 for a flat spiral using the funet formula using the parameters
>D1, D2, and N.  Next, compute angle=arctangent(H/T) (in radians) where
>T=D2/2-D1/2 (coil thickness).  Define F1=angle/1.5708, and F2=1.0-F1.
>Finally, compute the inclined flat spiral coil inductance L using the
>weighted average: L = L1 x F1 + L2 x F2.  This is simply a weighted average
>of a flat spiral coil and a solenoidal coil, with the weighting changing
>linearly as the coil height changes.  This formula will usually get you to
>within 10% or so.

Great. Thanks very much. I will build this functionality into the program.
10 is close enough I think.

>        Ideally, I would like to specify the capacitance, and then play
>around with the capacitor size and number of plates to make it work.  I
>would ALSO like to be able to just play around with the capacitor geometry
>and see what capacitance value I get, for most flexibility.  There should
>also be some general guidance in the program regarding a safe operating
>voltage based on the dielectric thickness and type of materials used.

This is what I have done. I have included a table of dielectric materials
with their electrical properties and have used this in the program itself.

>        For a rolled capacitor you get twice the capacitance.  I think the
>formula is the same except for the factor of two.  I'll have to check my
>notes at home.

Thank you. I appreciate it.
Graham
```