I have been waiting for the right conditions to fire up my 10" TC and today the conditions were right. I noticed last winter I got some of my best sparks when the air was dry. All day Friday I got static electicity shocks when I slide across my truck seat to get out. Also noticed lots of flashes of light from static in the dark when I moved the blankets in bed. The same condition I had last winter when I got some of my best sparks.
I got my 10" TC out Saturday evening and set it up in the drive way with the help of a friend. Maximum measured spark was 116" long with no rotor. I used an aluminum ladder on the right side and a basket ball goal on the left side as targets. I could get a continious measured 84" arc to either target. This is a continious 84" non stop hot frying arc, not an arc that starts and stops over and over again. But when I moved the target farther away by just 1" I could not get a continious arc. At a measured 85" the sparks from the sphere were long split streamer looking for a place to strike. After trying to find a place to strike for several seconds the arcs would start striking the ground and objects near by. Many of the arcs to the ground were over 9 feet long. One strike to a stick on the ground measured 116" long. Its strange the arcs would jump over 9 feet to ground when it was only 85" to the metal basket ball hoop.
Many of the arcs traveled toward the target then made a 90 degree bend and struck the ground. I tried to estimate the arc path to ground and get the best measurement as possible but this is only a guess, many of the arcs measured about 10 1/2 feet long.
Another strange thing was the continious 84" arc to the targets. At first the arc would be very straight but after a few seconds it would start to bend and get crooked like lighting does with lots of bent places in the arc. Sometimes the arcs would go up very high 3' and 4' and curve back down striking the metal basket ball hoop 84" away.
I could not get any sparks to break out on the 38" sphere without a break out point. At first I thought something was wrong and I double checked my connections. I changed the primary tap and still got nothing. I figured the sphere was too large for the system and I didn't have enough primary taps to find resonance frequency. With a 2" long nail on the side of the sphere I had no trouble getting arcs at turn 12 on the primary. I put a nail on both sides of the sphere and could get an arc to both targets. This is the 1st time I have run my 10" TC using the 38" sphere.
I was surprised that the spark gap worked so well. I have been thinking about building a rotor but now I am not sure I need one. I noticed by adjusting the fan speed of the spark gap it made a big difference on spark output. I found with the variac set at about 75% I got the longest spark output. If I increase or decrease the variac by 5% the spark output would drop. I got several 30 second runs with no over heating problems.
I ran out of film and didn't get any pictures of the long strikes to the ground. When the weather gets right again I will set up the TC and get some more pictures. Picture tc10-1.jpg is a pic taken about 1 hour before sun down just after I set up the coil. Its a good view of the system. Picture tc10-2.jpg is 5 second exposure of an 84" arc to a metal rod leaning up against the basket ball hoop on the left and some 79" arcs to the ladder on the right. Picture tc10-3 is a 10 second exposure with the same targets as before. I put 9 pics on my web page if anyone wants to see them all at http://home.earthlink.net/~gweaver. Click on My Tesla Coils and Related Items. Then go down to coil #7 to the pictures.
My secondary coil measures 10.5" diameter 32" long wound with 950 turns of #20 wire on a pvc pipe.
The primary is 14 turns flat wound 1/4" copper with 1/4" space between the tubes. Inside diameter is 14.5" on a wooden form. Outside diameter is 28.5". The primary is tapped at turn 12 and I got almost no output tapped at turn 11 or 13.
I am not using a rotor. I am using a Richard Quick variable speed vacuum fan spark gap with 8 gaps. Each gap is .025 inches. Its built inside of a 4" diameter pvc pipe 6 inches long. It has 9 copper tubes 3/4" dia. by 2" long.
Capacitors are oil filled rolled polyethylene in a pvc pipe. I have 4 caps in parallel. 3 caps are .01 uf each and the other one is .005 uf all rated 40KV. Total capacitance is .035 uf.
I am using my 38" diameter stainless sphere as the toroid on top of the coil.
I have 2 donut ferrite chokes wound with about 40 turns of #12 insulated house wire.
Power supply input is 240 volts 40 amps and 18KV output current limited to 9.6K