June 2004 - Above shows the longest arc that I have ever achieved - 66 inches from the discharge point (doorknob) to an aluminum downspout. (Photo is clickable for a larger image) This marked the unfortunate point in my coiling career where I now have to set up outside of the garage, subject to the wind, weather, ambient light, and neighborhood relations. Coil specs here are: 15/60 NST @140VAC in, 120BPS propeller sync gap, .04uF cap, 7x30 toroid, 2-layer Cu tubing primary, 6.3x28 in 26AWG secondary.
Above is one of my latest pictures, taken in July 2000, with my Olympus C3000 3.3 megapixel digital camera. This camera features the option of full manual control, essential for spark pictures. The shot was taken with aperture of f\ 2.8, and an exposure time of about 2 seconds. Streamers which connect to something come out very nicely but unattached streamers are somewhat dim. The remarkable thing about spark pictures taken with this camera is the clarity of the banjo effect - each "bang" produces a separate, visible streamer, nearly but not quite parallel to the others. This shot is with my 6" secondary, 15/60 NST, Maxwell .02uF/45KV cap, and single static vacuum gap. The multiple streamers despite having a breakout point are telling me that I need a larger topload!
Above shows my coil running with it's single segment static spark gap. I have two foil bumps on the top of the upper toroid to promote breakout. This is the same configuration that with a single bump, yields 51-inch arcs. Note how much brighter the arcs that connect to the ceiling are compared to the ones that just go off to the left. The ceiling is made of a steel mesh with some sort of cement applied to it. Note also the garage door track and the control wires running beside it. Always disconnect all wires going to one's garage door opener before running a coil!
This photo is similar to the one above it, but the tank capacitor is the Multi-Mini polypropylene cap instead of the Fair Radio Sales cap. Exposure conditions were probably different than the previous picture (I know I had a small incandescent lamp on in this shot to light up some of the coil features). I've noted no performance differences between caps.
Above is a picture I took when using my 12 segment RQ static gap. I am using only the smaller 4.5 x 15 inch toroid. This causes several simultaneous streamers to form, which looks nice in pictures, even if they're not record-setting in length. This is about a 5-8 second time exposure at f/ 2.8, ASA 200 film. At the time this was taken, I still believed in using chokes in the NST protection network.
Above is how I determine the maximum streamer length. I place a foil bump on the side of the larger toroid, aimed at the foundation wall on the left. The straight-line distance from the tip of the bump to the wall is 51 inches. When a streamer connects to the wall, it's much brighter than ones that don't connect, so it's easy to see if the distance is met.
Here's one of our playful cats, enjoying my Tesla Coil. Don't worry, cat fur is a naturally good insulator!
Can you say "double exposure"?
This photo shows my coil when it still had the flat spiral primary. With the primary mounted below the Lexan support plate, I couldn't bring the secondary any closer to improve coupling. I suspect that at the power level I'm running at, and with my relatively narrow secondary, I needed the increased coupling found in a conical primary.
Notice the parallel-lines appearance of the streamers. I've heard this referred to as the "Banjo Effect", but don't know why. It demonstrates that what appears to the eye as a continuous, luminous streamer, is actually a series of separate, short-lived arcs that all follow a similar path. The channel shifts upwards due to it's high temperature. Each short-lived arc is due to one "primary bang", or primary capacitor dumping it's charge.
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