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Re: Toroid made easy



Original poster: "D.C. Cox" <resonance@xxxxxxxxxx>


A very clever idea Gary.

Can you provide some photos to Terry so he can post them in the archives?

Dr. Resonance


I cut 2 pieces of .040" flat steel into a donut shape. Donut is 20" outside diameter with a 6" diameter hole. Metal plates are welded together along the outside and inside edge only. A very small pipe fitting is welded to the surface of 1 sheet of metal near the center. A 5 lb. bag of charcoal is ignited and given enough time to turn the 2 metal plates red hot. Air is slowly blown into the fitting and the red hot metal is blown up like a balloon. The flat metal will blow up into a toroid shape it is sorta like blowing up a car tire innertube. Let it cool. Grind the welds smooth and reweld if needed to make it smooth. You can also do the same thing to make a sphere. I did the same thing with two 20" circles no donut shape this time it made a very nice sphere. It only takes a few minutes for the metal to turn red hot so the charcoal is basically wasted. It would be good to make about a dozen toroid and sphere parts get them all welded together and heat them red hot one by one it would not be so wasteful on charcoal. I have not tried any really large ones yet but I see no reason someone couldn't cut out some 48" donuts shapes to make a large toroid. When the metal blows up like a balloon the outside diameter gets smaller. You can get a 98% accurate idea of the actual size by bending a sheet of paper into a radius to see how large your finished balloon shape toroid will be.
Gary Weaver