Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx> Hi Bill, I've built a small flat secondary: http://www.classictesla.com/photos/ba0/52002-f3.jpgThe primary is a second flat coil below the flat secondary. The secondary was wound on plexiglas which I placed on a Lazy Susan for manually turning. I laid down thin 2 sided carpet tape across the entire Plexiglas and wound inside to outside. The tape helped hold the wire down in place. I later coated. I never did get it to arc from a sphere terminal sticking out the center without help from a grounded object. I did try a needle electrode in the center at some point during that time and it arced down to the secondary. It will also arc across the entire surface when out of tune (racing arcs from inside to outside which is actually pretty cool to watch). On my secondary, the top terminal was connected to the center of the coil.
Here's a pic of an arc using a couple wires to create the discharge: http://www.classictesla.com/photos/ba0/52002-f1.jpgThe arc distance is about 3 inches or so (this was a low voltage single MOT supply). I ended up burning the outer traces during a separate experiment some time ago and haven't played with it since. Someone else on the TCML has built several flat coils and could probably give much better info than I can (forgot the name, he hasn't posted in quite a while).
I think to really find out your question, it would be best to build a replica of the Tesla flat coil. These little flat coils we've built I don't think will tell much. I do however expect the arc to seek out RF ground which just happens to be the outer edge of the coil, so there is a high probability that this will be the most common strike hit. There will no doubt be other arcs that do extend outward (as they would with any terminal). Arcs horizontal to the floor are always the most common, so I expect a flat coil turned 90 degrees as in the "drawing" to arc out horizontally. Effort must be made to prevent breakout on the opposite side of the coil.
I think the artists drawings were drawings of what he/she saw. I think also that there are many arcs that hit the flat coil that was simply not detailed in the drawing. If you want to experiment with a program on this coil, you could use Javatc has it will handle both flat primary's and secondary's.
http://www.classictesla.com/java/javatc.html Take care, Bart Tesla list wrote:
Original poster: William Beaty <billb@xxxxxxxxxx> QUESTION: If we actually build a large pancake-style TC secondary, and mount a sphere terminal on the end of a central rod, then does the discharge tend to occupy a fairly narrow cone which is directed outwards from the pancake coil? Yes or no. If nobody has experimentally determined the answer by building and operating such a pancake-shaped secondary, then we have no business pretending that we know the answer. If we want to adopt a scientific attitude, then we're not supposed to choose sides or to leap to unwarrented beliefs, instead we should remain tenative in the face of the unknown, and as Faraday said, "Let the experiment be made." I was hoping that the experiment ALREADY was "made" by someone here, so they'd give an answer.