I find the Web to be a great source of Tesla coil design information, but some questions I haven't found answers. Here goes...
Q1) Why is the primary typically a pancake coil set at the very bottom of the secondary tower? Why not a concentric cylindrical coil?
My best guess that why the coil is at the bottom is to keep it as far away from the top of the secondary as possible to keep the streamers off of it as much as possible. No idea why the pancake coil is used.
Q2) What secondary wire gage is optimal? One site recommends #20 wire because of the lower resistance thus higher Q of the circuit. Others use #24 wire just fine.
Q3) Building the coils will be the cheapest and easiest part for me, therefore, I will do this part first. Before I build the supply, I will use my high voltage supply that gets its juice from a 9v DC 300ma wall wart. The output is from a flyback transformer and is DC. It will charge up a capacitor I made out of aluminum foil and Mylar film and make a deafening crack from a 1" spark. It takes a few seconds for the capacitor to charge. I'm wondering if streamers will be emitted, although only a flash, if the coil is pulsed only every few seconds rather than at a higher rate than the high power supplies.
Thanks for any help, John