Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx> Hi Miles,My 13" secondary diameter coil was a sonotube form. It was my first coil. It was an excellent running coil but did go through some changes early on (added about 14" to the length). Before winding the form, I cleaned the inside and outside and gave it a find sanding. I insert a heat lamp on the ground pointing it up, and simply put the tube over it. This helped to dry out the tube (I kept an eye on it to ensure I didn't start a fire or anything). I then thinned down some polyurethane and coated the inside and outside. I wanted the urethane thin enough so that it would soak into the tube. Once I let that dry, I recoated with marine spar varnish on the inside. I then wound the form and coated the outside with the marine spar varnish (letting each coat fully dry before applying the next and lightly sanding). I put on enough coats until I had a smooth outer surface.
The coil ran great with the pig system and I had my best sparks with that coil. I eventually retired it after it fell over a few times putting nice dents into the side (funny, it still worked without problems). But, after the last time I knocked it over, a really BIG dent occurred as it landed on the end of a 2" diameter motor setting up on the ground (and of course, it hit that motor dead center).
Take care, Bart Tesla list wrote:
Original poster: "miles waldron" <mileswaldron@xxxxxxxxxxx> Is it OK to use one of those quick crete card board tubes from Home Depot that is 8 inches or 12 inches in diameter to build a 1200 turn #20 wire secondary? I want a big secondary to work with my 15KVA pole pig. The card board tubes seem to be waxed inside. If this is possible can someone provide any advice? If this is not a good idea, can someone please tell me why? Thanks!