Re: Flat Coils

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Barton B. Anderson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <tesla123-at-pacbell-dot-net>

Hi John T.- 

The inductance is increasing because you are dramatically increasing the number
of turns in the helical compared to the flat coil to keep the wire length the
same. Inductance is a function of the turns. 

A helical or flat coil with the same length of wire must come out to the same
inductance as long as the length, wire size, spacing between turns, and number
of turns remains constant (if your going to do a comparison of inductance).
When accomodating these constants, you will need to wind a helical coil at a
diameter twice the inner diameter of the flat coil. You should find that R and
L remain the same for the same length of wire. 

I like your method of winding the flat coil. That's the route I would go. 

Take care, 
Bart 

Tesla list wrote: 
>
> Original poster: "John Tomacic by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> <tesla_ownz_u-at-hotmail-dot-com> 
>
> All these postings about flat secondary coils made me take a quick look at 
> the inductance of a flat coil and compare it to a helical coil I already 
> have.  Surprisingly, the inductance of the flat spiral coil is 60% higher 
> for the same length of wire. In this case the length of wire is 1478 feet. 
> Since the wire resistance is the same for both coils, is it safe to conclude 
> that the Q of the spiral would be 60% higher seeing that Q is proportional 
> to XL/R? 
> If so, then there is an advantage to using flat spirals as secondaries, 
> especially in magnifiers where it would be easy to feed the secondary from 
> the centre, and have a toroid around the outside circumference of the 
> secondary. 
>
> Also, I have an idea for winding the flat spiral, however, I still need to 
> try it out to see if it works: Place 2 round plexiglass discs close 
> together, separated in the center by a round spacer with spacer thickness 
> equal to wire diameter and spacer diameter equal to desired inner diameter 
> of coil.  Wire would then be wound around the center spacer by spinning the 
> whole "sandwich", and the plexi disks would keep the wire flat as the spiral 
> is built up.  One of the plexi disks could have 1/2 inch wide radial slots 
> in it to apply glue to hold the wire in place after the disc is removed (or 
> both disks could stay in place after finished). The spacer in the middle 
> could be a pvc pipe of desired diamenter and the plexi disks would have a 
> hole of the same dia as the pipe so that the discs could slide over the pipe 
> to the desired separation. 
>
> John 
>
> >From: "Tesla list" <tesla-at-pupman-dot-com> 
> >To: tesla-at-pupman-dot-com 
> >Subject: Flat Coils 
> >Date: Thu, 14 Feb 2002 19:15:32 -0700 
> > 
> >Original poster: "davep by way of Terry Fritz <twftesla-at-qwest-dot-net>" 
> ><davep-at-quik-dot-com> 
> > 
> > 
> > > > BTW -  One can ground the center and use the outer windings as the 
> >high 
> > > > voltage ends... 
> > 
> > >         Or vice versa, as in many of the Tesla patents.  He clearly was 
> > > intrigued by them, but don't remember seeing any pictures of apparatus 
> > > he built using them.  Has anyone? 
> > 
> >       pix in the Colorado Springs notes and 'Experiments with 
> >       Alternate currents of High Potential...' (or whatever 
> >       the exact title,  Not clear which were Secondaries, 
> >       which probe/test coils, perhaps. 
> > 
> >       One interpretation of the Colorado Springs notes argues 
> >       that the 'primary' in some/many pix is a single turn 
> >       (thus flat) down near the floor.... 
> > 
> >       best 
> >       dwp 
> > 
> > 
> > 
>
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