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116" sparks NO ROTOR
From: gweaver[SMTP:gweaver-at-earthlink-dot-net]
Sent: Friday, January 09, 1998 11:25 PM
To: Tesla-at-pupman-dot-com
Subject: 116" sparks NO ROTOR
I got my 10" TC out Saturday evening Jan 3rd 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 the ground. 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 that was grounded.
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 14 turn 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 on the spark gap it mades 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. I put 9 pics on my web page if anyone wants to see them all
at http://home.earthlink-dot-net/~gweaver. Click on My Tesla Coils and Related
Items. Then go down to coil #7 to the pictures. I also linked the pictures
to the Tesla Coil Photo
page.
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 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
Gary Weaver