Re: (portable) physically large coils

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>

At 11:05 AM 3/8/2006, Tesla list wrote:
> Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx>
>
> Hi Jim,
>
> The secondary should be open frame, rigid, light weight, and 
> non-conductive. Obviously, rods can be used between sections.
>
> Each section must be "fastened" together nice and tight to ensure a 
> rigid framework. This is the most challenging.
>
> The insides of each section are not available. With this in mind, 
> either the top and bottom supports are ring style with fastening 
> crossmembers, or, the top and bottom rings are designed so that when 
> a section is placed on top of another section, pins sticking out 
> perpendicular at the ring edge enter a channel in the lower ring 
> section. A twist and lock approach.

I think you could go with a thin solid tube (imagine a fiberglass 
with the winding) and open on the inside.

You could have a couple members across the tube in a cross that you 
could have something like wingnuts or latches or velcro to attach together.

You might want a solid disc in the middle of the tube to prevent arcs 
down the middle.


> One of the protruding dowel pins could serve as a connection and 
> seat into a connection socket at the end of the channel. The top and 
> bottom supports need to be machined with some precision.

This is actually the challenge.. what sort of electrical connection 
would be mechanically secure and wouldn't have too many edges.  Maybe 
something like a ring of copper pipe on the end of the section that 
presses against a ring on the other section.


> I envision a 2" gap between sections (without wire) simply to 
> support the fastening of sections.
>
> The real advantage about a sectional approach is shipping (each 
> section could be crated and protected).


And, if you made the sections slightly different diameters (say, 18" 
at the bottom, 16" at the next, etc.) you could nest them for 
shipping. The English paper actually had tapered sections, so when 
stacked in one way it made a roughly conical structure, but if you 
flipped them all around, they nested. I seem to recall that it was 
openframe (wires on rods) construction and hexagonal or octagonal.


> Anyway, something along those lines.
But then, you're still faced with the portable primary.  But, I was 
thinking that if you just made 4 or 8 supports with notches, and laid 
a flexible cable into them for the flat primary spiral.

Or, go with a helical primary which would just be like yet another 
secondary segment, and you could nest them.  A two foot diameter, 2 
foot high helix with 10-15 turns might do nicely.

I think a 2x2x2 foot package is something reasonably 
manageable.  Certainly, 16x16x16 is (that's one of those standard 
medium sized moving boxes)

So.. you could have a 2x2x2 foot box that is the primary and all the 
secondary segments.
another double milk crate sized box for the transformer, sparkgap, etc.

And then, some sort of collapsible toroid.  I've had bad luck with 
inflatables, but maybe some sort of mesh cover over a framework might 
work.  Or, the traditional dryerhose and pieplate type design, except 
with a more rugged dryer hose that expands and collapses. (the usual 
ducting is "expand once")

you're talking a BIG coil here, so mirror finish on the toroid 
probably isn't all that important.

The suggestion of making the toroid in metal segments is a nice one. 
You could stick them all together and tape the seams with aluminum 
tape each time you deploy.

you'd also carry a roll of chicken wire to use as a ground plane/counterpoise.

> Take care,
> Bart