My new coil

To: tesla-at-pupman-dot-com
Subject: My new coil
From: Julian Green <greenj-at-swlogica.demon.co.uk>
Date: Wed, 12 Feb 1997 12:30:00 -0500
Subscriber: greenj-at-swlogica.demon.co.uk Wed Feb 12 23:07:37 1997
I have just recently completed the construction of my second coil.

The coil consists of a 10" secondary wound on HDPE pipe 950 turns of
1.02mm enameled copper wire.   The secondary consists of 11 turns of
3/8"
copper pipe, capacitors are home made poly/foil construction 0.03uF.

Powered by 11KV 5KVA single phase pole transformer using a home made
rotary spark gap based on a brush type motor with top speed of 15,000
rpm.

The toroid is pathetic, being the same diameter as the coil, I
could'nt wait to try the coil out so last week end I fired her up.

The first time of firing this coil was also the first time of using a
pole transformer, so I thought it best to do things slowly!

By turning to rotor on the gap so that two electrodes aligned I powered
the
coil up using a variac.   At about 10% the gap fires, and soon becomes
red
hot, not much good for coil firing but OK for tuning up using a
flurescent
tube.   Having found a good tune (turn 9), the rotary gap was started at
low
revs.

With more power being applied to the pole transformer large bangs and
rough
coil running the variac began to smoke and fuses blew.   12" sparks for
the
top of the coil - went to bed.

Using a pole transformer for the first time was scarey!   Good job I had 
practiced on a neon transformer first.   I always unplug HV supply when
making
adjustments even if the variac is at 0%.   I got a nasty shock from my
neon
when supply still connected and variac at 0%.  I later measured the
output 
of the variac - it was 2 volts, stepped up through the neon made
150volts.

With a fresh mind the next morning I repaired the variac (stuck brushes)
replaced the fuses, and used a 100 meter extension lead as resistive
balast.

This time I ran the spark gap at
about 40% and coil at 40%.   Things ran much smoother, no banging, and
no
blowen fuses.   Getting 2' arcs.   Increced power to coil to 100%. 
Sparks
now up to 3'.    Increaced power to spark gap to 80%.   The spark length
increaced significantly 4-5' the color of sparks changed from purple to
white/blue, noise increaced (need ear protection) - must be getting
better
quenching from the gap as speed increases.

Then desaster!  Vibrations on the spark gap cause the electrodes to
strike
shatering the rotor and bent the stationary electrodes.   Pieces of
spark gap
shot across the garage.

After re-building the sparkgap (better desgn this time) I can not get
longer
sparks than 4-5'.   Partly because the ceiling of the garage is in the
way.
Everything is being run at 100% power now.

Things I plan to do to increase spark length:

1)      More electrodes on the rotary spark gap.   Currently 2 increase
to 4
2)      Build a toroid
3)      Add more capacitance to the tank circuit in order to match new
        secondary resonance when new toroid fitted.
4)      Connect second pole transformer (5KVA)

Any tips on getting better/longer sparks are very welcome

Julian Green