LET THE SPARKS FLY
There are 3 variables you can play with: size of
the spark gap, angle of the neutralizing bars, and
switching of the Leyden jars in and out of circuit.
Start with the spark gap set to about 1", the
neutralizers at 45° to the collector combs ( 90° to
each other), and the Leyden jars disconnected.
Turn the crank smoothly at a moderate speed. The
electrodes should produce a thin blue spark. Look
closely and you’ll notice that one end is brighter;
this is your positive electrode.
Stop cranking and engage the Leyden jars. These
can hold a charge for days. From this point on,
consider the machine “hot” until you short the electrodes by simultaneously touching both with the tip
of a screwdriver. Also be warned that Leyden jars
can acquire charge just sitting there, so you need
to discharge them this way each and every time
before you touch the electrodes.
Turn the crank again. After several revolutions
you’ll hear the neutralizing brushes crackle, you’ll
smell the fresh scent of ozone, and — CRACK! —
a strong blue spark will jump the gap.
Short the electrodes and reposition them a little
farther apart. Crank some more and you’ll see a
bigger spark. Repeat this procedure until you see
multiple small sparks jump from one of the collectors, across several sectors, to a neutralizing brush.
You’ve reached your maximum spark length.
After you find the maximum gap, you can adjust
the neutralizing bars. Narrowing their angle from
90° to about 60° will increase the maximum voltage
at the expense of a small decrease in current.
Your machine should require little maintenance, but
may require periodic replacement of the belts and
cleaning of the disks. Use only water to clean them,
or rubbing alcohol if you suspect there is oil on them.
THE ELECTRIC KISS (AND OTHER
Wimshurst machines had a place in Victorian entertainment. After a fine meal, guests might adjourn
to the parlor for games, discussion, and scientific
demonstrations. One can imagine the visceral
impact of the Wimshurst machine, with its spinning
glass disks, electrical discharges, and the loud report
of 6" sparks.
For the adventurous, in the right company, there
was a demonstration known as the electric kiss.
Two volunteers would stand on insulating surfaces.
Each would touch one of the 2 charge collectors
and then they’d slowly, without any other part of
their bodies touching, bring their lips together for
the inevitable “tingle” of electricity.
CAUTION: Demonstrate the electric kiss only
with the Leyden jars taken out of the circuit,
to avoid a painful jolt.
To demonstrate the Wimshurst machine with
Franklin’s Bells, see makezine.com/17/wimshurst.
For further reading, I suggest:
Ford, R.A., Homemade Lightning: Creative
Experiments in Electricity, 2001
Francis, G. W., Electrostatic Experiments: An
Encyclopedia of Early Electrostatic Experiments,
Demonstrations, Devices, and Apparatus, 2005
See the Wimshurst machine in action at
makezine.com/17/wimshurst and on Make: television,
Episode 103, at makezine.tv/episodes.