Re: "kicker"

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Dr. Duncan Cadd by way of Terry Fritz <twftesla-at-qwest-dot-net>" <dunckx-at-freeuk-dot-com>

Hi Chris, All!

>I have a question: Can anyone point me in the direction of what a
kicker coil
>is exactly, how they function in a tesla coil, or how they are made?

It's simply a coil with a bit of inductance to it, say a few hundred
millihenries or so upwards.  Maybe 1000 turns 18AWG on a cylindrical
iron wire core 7" by 1".  Without going to all that bother, you could
simply use a small choke wound with thick wire.  Something of that
order anyhow.  If you connect to e.g. a 12V battery, and then break
the contact, when the contact breaks there is a nice big blue spark
caused by the back emf induced in the coil by the collapsing magnetic
field, the strength of which is

E = -L (di/dt) volts

where L is the inductance in henries and di/dt is the rate of change
of current (the minus sign simply shows that the induced voltage is in
opposition to the initially applied voltage, as required by Lenz's
law).  Usually you have a small capacitor, say 2uF at 400V or so
across the contacts, which reduces contact wear and soaks up that
reverse voltage by charging the cap with it.  Mind your fingers if you
try this out - the back emf will bite you.  Use insulated pliers to
hold the wire instead!

However, if you have connected across the interrupter mechanism a
suitable cap in series with the primary of a Tesla coil, when the
interrupter opens you will get strong rf ringing in the LC circuit
across the contacts and this can be used to drive a TC in the normal
way.  I've seen a circuit diagram and illustrations for one of these
things but never built one.  FWIW kicking coils were also used as
simple spark transmitters in the early days of "wireless" and a
miniaturised version, the buzzer, or preferably shunted buzzer (really
little more than an electric bell without the bell) was used as a
tuning aid for spark sets and crystal receivers in conjunction with
wavemeters and decremeters.

>I have
>one of the morris and lee (edmund scientific, science first)
coils...had it
>since I was in my teens. the little induction coil thingy (with the
>interrupter) is puzzling me. Is it a kicker? or is it an induction
coil?
>There is no spark gap other than the interrupter, and the 2 caps are
in
>"equidrive" config. Just curious!!


This I am not familiar with, but from your description it sounds like
a kicker.

Dunckx
G1 #1113