NEW POOL TOY TOROID
This is my new 8" x 26" toroid. I built it to replace the 7" x 28" inner tube & foil toroid I'd been using. The inner tube toroid was a great performer, but it was so wrinkly, lopsided, and downright ugly, that I could no longer tolerate it. My new toroid is based on a vinyl swimming pool toy I bought at Wal Mart. After inflating it as hard as I could using lung power, I covered it with several layers of paper mache'. I used the traditional strips of newsprint saturated with a 50:50 mix of Elmer's white glue and water. At first I was disappointed by the wrinkly appearance, but I found that as the paper dried, it shrank and pulled itself drum-tight, resulting in a smooth finish.
Applying the paper mache' proved to be a tedious and time-consuming business, and the task stretched into days. I got tired of doing it, and the paper still was not thick enough to achieve the desired stiffness. To fortify the thin paper shell, I bandaged the torus with strips of plain white cotton bed sheet fabric from my wife's sewing scrap bag. I stuck the cloth strips in place with water/glue mix, then slopped on clear gloss urethane varnish. The fabric covering soaked up half a can of varnish, resulting in a rigid outer skin. The fabric strips produced a rougher surface finish, but I was satisfied with the compromise. Next, I covered the toroid with four, 30-foot rolls of 2" wide Aluminum HVAC tape. This went on quickly. I polished the tape down with the side of a curvy drinking glass until I achieved a smooth, almost chrome-like finish. I plugged the center hole with a disk of 1/2" plywood covered with heavy duty Aluminum foil stuck on with spray glue. I cemented the disk in place with a double bead of clear silicone glue. I'm pleased with the finished product, but if I had it to do over again, I wouldn't. Next time I'll use Aluminum flex duct.
The price is hard to beat. I spent almost nothing on it. The pool toy was $1.44. The cloth, paper, and fabric were all scraps. Appearance-wise it is better looking than a flex duct toroid, but not as nice looking as a spun Aluminum toroid or Gary Lau's Styrofoam core toroid. Still, my time is worth something, and this thing took way too many hours to build. If you're too poor to afford a spun Aluminum toroid or a custom Styrofoam toroid form, but you have plenty of spare time, then paper mache' is the way to go. The Tesla coil responded positively to the new top load, sprouting long, intense, blue-white sparks. Unfortunately, the output is just too much for my garage space. Every spark hits something--walls, ceiling, floor, etc. I guess I'm going to have to move outdoors in order to properly judge the improvement.