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Re: Big Toroids, collective conscious brain storm



Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>

At 03:00 PM 9/12/2006, Tesla list wrote:
Original poster: "Scott Hanson" <huil888@xxxxxxxxxxxx>

Several different fabrication processes COULD be used for fabricating toroids, but only a few would be realistic candidates for the low-volumes of Tesla-coil enthusiasts. Some of these processes are:

1. Roto-molding:

2. Blow molding:

3. Vacuum-forming I think the best candidate fabrication process for toroids in the sizes we are interested in, and in realistic quantities, is vacuum-forming. In this process, a sheet of thermoplastic is supported in a frame, and then heated by infra-red lamps or overhead gas burners until it is quite soft. T



Of course this takes a fairly large machine, but it is quite simple and (theoretically) could be home-made using aluminum or steel angle-iron, banks of infra-red heating lamps, and a "cheap" vane-type vacuum pump along with a big vacuum reservoir.


A vacuum cleaner will provide more than enough force.

But consider this. Since you're going to be seaming around the "equator" anyway, why not vacuform octants (i.e. quadrants of a toroid). A 2x2 foot piece of plastic is quite reasonable to handle.


A good friend of mine has a large vacuum-forming system that is used primarily to form aircraft parts (interior panels, etc), and I have watched this system in use over the years fabricating many different types and sizes of parts from different types of plastic sheet.

In fact, you could probably find a local place that would be happy to make the "buck" that is the form (made from wood, so it's something that is home fabricatable) and to zap out endless quantities of untrimmed panels. You would be responsible for trimming the panels and gluing it up.

You could easily put a small "lip" on the edges to make the joining easy.



4. Yet another process that could be used is vacuum-bagging.

This process is extremely simple from a tooling aspect, but is very labor intensive and really requires a lot of experience to get good results. It is as much an "art" as technology.

Very very much..


I have talked to my friend previously about forming some prototype toroids using either his vacuum-forming or vacuum-bagging setup, but just have not had the time to follow up. Some of his vacuum-bagged aircraft parts have to withstand lightning-strike testing, with a fairly high level of electrical conductivity, so I'll check to see what the material options are. It would be very nice to see a lightweight, absolutely dent-proof, reasonably-priced black carbon-fiber composite toroid that was conductive enough for Tesla coil topload use without requiring an external conductive coating.



Or a vacuum-formed ABS or polycarbonate toroid that was equally-dent proof, either covered with aluminum tape or sprayed with conductive nickel-based EMI shielding paint.

I'd go ABS or styrene.. easy to glue, not brittle (if you pick the right material and filler) cheap

and figure out someway to apply a conductive coating.

Regards,
Scott Hanson