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Re: Stainless steel convoluted duct toriod: my experience



Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx>

Hi Dr.,

Hey, the pics were great. I'll probably give a mesh toroid a try next toroid I build of any size. Thanks for sharing the pics, they kind of put the mechanics in perspective. Do you have any pics of the mesh on the discs? That is another part of the detail that was missing in the pics. Obviously I can predetermine what "I" would do, but what you have done would probably be a better method.

Take care,
Bart

Tesla list wrote:

Original poster: "resonance" <resonance@xxxxxxxxxxxx>



I still think the mesh toroid method is the way to go. I have made several 8 x 30 and 60 x 16 toroids in this fashion. When finished we spray them with black conductive paint. They work great for larger and even medium size coils that you intend to pump a lot of power into. I will send the fabrication photo details to Terry and perhaps he can post them in the archives section for your viewing.

http://hot-streamer.com/temp/DC_Cox/

An 8 x 30 size costs approx $125 to fabricate plus two days of your time. They work great --- you will see them run on our large coils at our Teslathon next week.

Dr. Resonance



Original poster: "Scott Hanson" <huil888@xxxxxxxxxxxx>

Jim -

I found Rubber-Cal/Ducting.com in Santa Ana, CA about two years ago, and stopped in one afternoon. They are primarily a distributor of industrial hose, and do not stock much duct material that would be useful for toroid fabrication. They do have an interesting sample shelf with 1' sections of a lot of different duct & hose products. Before getting excited, look at the pricing; its outrageous, in my opinion.

Another option is the convoluted stainless-steel duct material used as chimney liners in the Midwest & East-coast areas. (search the web for "chimney liner"). It doesn't seem to be widely used on the West coast. Its available in several different stainless-steel alloys, in sizes from 3" OD to 16" OD. I think all this stainless steel duct material is manufactured by only one or two sources, and sold for different end uses.

I obtained a 6-foot long section of 6" diameter duct, fabricated from alloy 316, to evaluate its use in damage-resistant toroids. First off, it is truly crush-proof and dent-proof. I think it would easily survive all the drops and knocks that quickly turn an aluminum duct toroid into junk. Whereas the convoluted aluminum ducting is fabricated from extremely soft alloy, the stainless steel material is thicker and MUCH, MUCH harder & stiffer. I don't know if the stainless steel strip starts off as half-hard material, or just work-hardens during fabrication, but it ends up being like a huge spring. Its intended use is for basically straight runs lining a brick or masonry chimney. Trying to form it into a torus of reasonable diameter is almost impossible, at least with the 6" diameter material. Larger diameters would be likely be even worse. First, you'd need a piece at least 1.5X or 2X longer than needed to form the actual toroid to allow you to form a 1-1/2 turn helix. The material is so stiff that you can't form the "ends" into a radius, they just stick out straight. You'd need to form the 1-1/2 turn helix, cut the straight "ends" off, and then try to find some way to flatten out the helix so the cut ends could be aligned and joined to form a torus. The joining process would also take some ingenuity, as the material is too thin to TIG weld, so some sort of insert would probably need to be fabricated to align and secure the open ends.

Bottom line is that the stainless-steel duct material itself looks promising, but the process for converting a length of this stuff into a presentable toroid needs to be worked out. I just haven't had enough free time to develop the fabrication process, so my ducting still sits in a big box gathering dust......

Regards,
Scott Hanson