Electrostatic machines are electromechanical
devices that produce "static electricity", or electricity at continuous
(DC) high voltage. They were fundamental in the early studies about
electricity, started in the XVII century, in the form of "friction
machines", and their development culminated at the end of the XIX century
with the development of powerful "influence machines". Today, some
specialized uses for them continue to exist, but they are mostly seen as
demonstration devices in physics laboratories, with much of their history
I started experimenting with these machines
by 1973, building a first series of machines. With this I learned a lot
about electricity, and I still think that all people interested in
electricity or electronics shall try these machines to get a real feel of
the subject. At least, high voltage static electricity is something that
you can see and feel. Eventually I abandoned the subject for several
years, but in 1996 I renewed my interest in this subject, started to study
and build new machines, and set up these pages.
Below are pictures and descriptions of my
old machines, of machines that I built more recently, of machines built by
others, pictures from old books and papers related to electrostatic
machines and other high-voltage devices, and also some pictures from
museums. There are also extensive references, covering classical and new
materials. This site is always in construction. I plan to add more details
about the machines depicted and historical material, as soon as I find or
receive more data from interested people, build and experiment with new
machines, and have time.
Está também disponível uma seção em português.
To navigate through this site efficiently,
use the "open link in a new window" function of your browser to see the
pictures in the links, and use its search function for searching. Recent changes.
"Ignis ubique latet, naturam amplectitur
Toepler, Bonetti, Voss, Bohnenberger, and Nicholson
- A Wimshurst
machine  that I built in 1974. Front
view, back view, and with two Leyden
jars. A schematic diagram, with the disks
represented as cylinders, and a description of how the Wimshurst machine works.
- A Ramsden friction machine , built in
1975. Small (18 cm acrylic disk), but useful to test the insulation of
materials and for for starting the influence machines in humid days.
- A Lebiez machine,
or simplified Voss machine [p31], in front
view and in back view. Built in 1975 as a
kind of Voss machine, and rebuilt in 1996 in this form. Schematic
diagram, with cylinders instead of disks for my machine. This machine is
equivalent to Lord Kelvin's "replenisher" (see below), with better
insulation. The classic Voss machine, also known as Toepler-Holtz
machine, is better and is built in this way,
with charge collectors and inductor plates separated. A possible similar
true Voss machine is shown here and here.
- A small cylindric
simplified Voss machine built in 1997, with the same structure of
the previous machine. Side view, and another
view. It is similar to a Dirod machine .
- A symmetrical 2
disks Toepler machine , with some modifications, built in 1997.
Side view, another
view. A drawing. A schematic
diagram, with the disks shown as cylinders. This machine has excellent
performance, and can generate higher voltage and even more current than
a conventional Wimshurst machine with the same disk size. In 1999, I
built a larger machine. Look at the bottom
of the page here for a description.
The first classic Toepler machine (1865) was
built in this way , with a different
interconnection and disks with two sectors only. Toepler described also
a symmetrical machine (1866) that is very
similar to my machine (the picture shows a sectorless machine and a
similar device used as voltage multiplier). schematic
- My first sectorless Wimshurst machine, or Bonetti machine  (ray-tracing
drawing), built in 1997, with 31 cm disks. A drawing.
Another view. Pictures of the actual machine,
in front view, and back
view. A detail of the charge collectors and
neutralizers. Pictures (video frames) of sparks from this machine:
A short spark, a long
spark with a loop, and a longer one. The original
Bonetti machine (1894)  used series of brushes as neutralizers
instead of combs.
- A Holtz machine
- of the first kind, that I built in 1997. A drawing.
Another view, and a schematic
diagram. Pictures of the actual machine, in front
view, and back view. This machine was
the first really powerful influence machine, invented in 1865, and was
very popular, even requiring external excitation to start. An apparently
complete actual machine is here. Some
additional pictures, from books by H. Pellat: A Holtz
machine  (the fixed disk is in a wrong position), a better
picture , a double Holtz machine ,
and a machine with neutralizer and friction starter
. And another good picture . This
picture shows a machine with a more modern
structure . A multiple machine . Here
is a picture of the Holtz machine of the second
kind, that uses two counter-rotating disks, as the Wimshurst and
Bonetti machines. A drawing of a possible
- The Leyser machine
(1873) , is variation of the Holtz machine with the output taken
at positions that would be under the inductor plates in the regular
machine, and the neutralizer bar where the original output circuit would
be. This is the schematic diagram of the machine,
with a cylinder instead of the disk. This is a different
design due to Weinhold (1887), with wood inductors and no
insulating plate . This diagram 
shows how it operates. Initial plans for a machine that I have built are
here, in front view and back
view. The version that actually worked was somewhat different.
- A double Voss machine,
or double Toepler-Holtz machine, with classical structure, built in
1998. A drawing, and a photo
of the machine. This is a good self-exciting machine, invented in
1880. With 27 cm rotating disks, it produces sparks with up to 10 cm and
more than 50 uA of short-circuit current.
- A Bohnenberger
machine (1798), that I built in 1998. A drawing,
and a picture of the machine. An ancient
machine of the "doubler" type, it is not a powerful machine, but is very
interesting. See more about "doublers" in the section about influence
- In June 1999 I made experiments with a bipolar Van de Graaff generator, (drawing)
similar to the original
machine, but smaller.
- This is a large
Bonetti machine, that I started to build in December
1999. The disks are old ebonite disks that come with the Radiguet
& Massiot Bonetti machine that I recently restored. A drawing
of it. Front view, and back
view. Another view of it, and another.
Some sparks, that may reach 20 cm..
- In April 2000 I finished a Wimshurst
triplex machine. (drawing). It's a
double Wimshurst machine, using the close proximity between the central
disks to increase the output current, through greater induction and
mutual shielding. Pictures of the machine, in front
view, back view, and side
view. The machine produces a high current (100 uA with the 36.5 cm
disks rotating at 16 turns per second, 4 times more than a single
Wimshurst machine with the same disks). With the original design, it
reached only 8-12 cm sparks, eventually
reaching 14 or 15 cm on dry days, because
with the rather small separation of the sectors it easily sparked
through them and the neutralizer bars. With half of the sectors
removed, it produces consistent 15 cm sparks.
- By the same time, I made also a working version of Bennet's doubler, a curious simple influence
- In August 2000 I made a version of Nicholson's
doubler, the first automatic influence machine (1788).
- In January 2001 I completed a double
machine, following closely the original
design of [p84] (1920), but with modern materials. Front
view, and back view. A collection of parts. Partial assembly.
Assembling the neutralizer. Neutralizer and
other details assembled. Back
view. The machine, almost complete. Back.
The disks, and the switches.
The complete machine. back
view, side view, other
side, and another view, with only
painting missing. The machine works quite well (13.5 cm sparks, 100 uA
current) for the two 28 cm disks.
- In March 2001 I made a curious AC
electrostatic machine, apparently new, that I named as "half Wimshurst machine".
- And by April 2001 I extended the same idea to a three-disks
machine, that I named as "unfolded
- A Wehrsen machine,
completed in April 2002. It is a prototype for a large Wehrsen machine
(see below), that I started to build in August 2001. Some parts
for it at the start of the construction. Almost
complete, by March 2002. Back view. Working, it performs quite well, with 11
cm sparks and 70 µA of short-circuit current.
- An electrostatic
linear motor, completed in January 2002.
- A large Wehrsen
machine, first tested by August 2003. Almost
complete by July 2003. Another view, back view. Ray-tracing picture.
Just before the first test. First test.
The machine is still without its definitive rotating disk due to
construction and insulation difficulties.
- This is a Toepler-Dirod machine that I was
building by March 2004, still without spark terminals, and with
terminals. It's connected as the symmetrical Toepler machine, but uses Dirod-type
disks. A drawing of the final machine. The
machine works, but is weak.
Bennet's doubler. A curious little machine that I built in April
Nicholson's doubler. A version of Nicholson's doubler with
back-and-forth movement, built in May 2004. So far not so good as the
- A rotating
Bennet's doubler, with a new construction using sectored disks,
built in 2006. Photo of the machine. Another
- Wilson's machine, the oldest influence
machine with symmetrical output, in a reproduction made in 2007. A good
and interesting machine.
- A Van de Graaff
generator with external belt. A big machine for "hair rising"
demonstrations, completed in 2007.
doubler with reciprocating levers. A new structure for Bennet's
doubler based on Wilson's machine, built in 2007.
- An "electrostatic orrery". A classical
demonstration device, built in January 2009. It is quite heavy, but
site shows some similar old devices. Video.
- Henley electrometers built in 2009.
Classical instruments first described in 1772. A video
of them operating with an electrophorus. Videos of experiments with an
- A Wimshurst
machine with insulated sectors, built in 2008-2009. This machine
is highly insensitive to humidity.
- See also the comments about machines that I have restored, in the
section about influence machines below. Of special interest, the Ducretet and Roger and Radiguet and Massiot machines.
- Electronic version
of Bennet's doubler. An electrostatic generator suitable for
electrostatic energy harvesting.
- Pfaff and Svanberg
multiplier. A complicated multiplier with four plates, described
in 1846. Built in 2011.
machine. A simple symmetrical machine described by Lord Kelvin in
1867. Built in 2011.
- Experiments with enclosed
spinners and flames. In 2011.
- The Gläser machine,
that for awhile is a cylindric Wimshurst machine. Built in December
- Some simple high-voltage
- Belli's doubler, and
comments about the machines developped by Giuseppe Belli.
- A bigger Half Wimshurst machine,
completed in January 2014.
- Polarity detectors.
Simple electronic electroscopes. Completed in April 2014.
- Tubular electronic
doubler of electricity, made in January 2015.
Machines built by others
- A big Wimshurst machine built by Jim
- A sectorless Wimshurst machine with 60 cm
disks. This machine was built by Ed Wingate. A spark
from this machine. Another sectorless Wimshurst
machine, with 30 cm disks. Similar to the one described by R. A.
Ford in . A more recent picture. Side
and base view. Neutralizers, Charge
collectors. Another view. This machine
was built by J.
Hardesty and Ed
Wingate. Photos sent by Steve
- An old Wimshurst machine repaired by Johannes Zolk in 1996, with the
original broken disks replaced by LP records, with good results. Front
view, and back view. Photos sent by J. Zolk.
- A "shake-sphere" machine , built by Joachim Bolz and his students in
1997. It is an influence machine using two balls in a tube, moved by
shaking the tube, instead of disks. It works as my Toepler
machine above. An schematic diagram of
it. Photo and drawing by J. Bolz. Operation
of the machine.
- Complete plans for a beautiful Wimshurst machine, built by J.
M. S. van Gelderen in 1997. Plans for the disks,
a top view, a back
view, a side view, and details of the
terminals and Leyden jars.
Pictures from the machine, seen from the front
and back sides, and from above here
- Ricardo "Rike" built
this Wimshurst machine in 1997, using LP
records for the disks. It produces 7 cm sparks. Another
- A beautiful large Wimshurst machine (40 cm disks), built by James
T. Garavuso in 1998. A frontal view, another,
a side view, a back view with the terminals in storage position, another,
and a view from above. Details if the charge
collectors, neutralizers, and secondary
spark gap. This machine produces 12 cm sparks.
- A Toepler machine, built by Maximiliano
Guzman, from Spain, in 1998. The disks have 27 cm of diameter. A
later version used larger shields and a speed multiplier in the crank.
- A Wimshurst machine, built by Raymond
Zaborski, from the USA, in 1999. The small intersector distance
and the neutralizers at low angle result in intense current and easy
self-excitation, but relatively small spark length.
- A big motorized Bonetti machine, built by Emery Wayman, from the USA,
in 1999. The machines has disks with 61 cm of diameter, and produces
sparks with up to 28 cm of length. Some sparks from the machine: 1,
2, 3. The terminals
balls have 7.5 cm of diameter. Mr. Wayman has built also a similar,
smaller, machine with motors driving directly the disks.
- A motorized 2 disks Toepler machine, built
by Roger Magnuson
in 1999. The disks have 20 cm of diameter. Another
view. Note the small Leyden jars built in the terminal supports.
- A classic Wimshurst machine, built by Ronald
Coleman in 1999. Detail of the crank, and
of the charge collectors. The machine is
prepared for an upgrade with larger disks.
- A Wommelsdorf condenser machine with double rotation,
built by Bert Pool, following plans
in a thesis written by Wommelsdorf in 1904. Another
view. This machine is a compressed version of a multiple Wimshurst
machine, with sectors mounted between pairs of insulating rings,
interconnected through the external or internal edges of the rings. One
set of rings/sectors is held by the inner side and the other by the
outer side, and both turn in opposite directions.
- A well built small Wimshurst machine, made
by Harry Boneham, from Canada. The support structure was machined from
aluminum, with the disks having 18.5 cm of diameter. Another
- A Wimshurst machine, built by Terry
Baines, from England, in 1999. With 30 cm disks, it produces
sparks with 3 cm.
- A Wimshurst machine, built by Alex
Rice, from England, in 1999. The machine has 32 cm disks, and
produces sparks with 10-11 cm of length. The spark is a double exposure.
A spark from the machine. In 2000, he built an
- A Wimshurst machine, with 18" acrylic
disks, built by John Clark,
from England, in 2000. It produces 3" sparks.
- Dan Bowlds, from
Kentucky, USA, designed this original machine.
A bare disk rotates behind an insulating plate, that holds four wood
blocks painted with conductive ink. The lateral blocks are connected to
blades collecting charges from the back surface of the rotating disk,
and to Leyden jars made in the supports. The upper and lower blocks are
inductors, and are charged from the terminal blocks through single
corona points, also made of wood. Opposite to the inductor blocks there
are interconnected neutralizer blades. The terminals are directly
connected to the Leyden jars in the supports. An elegant structure for a
small motorized machine (the disk has 6" of diameter) that works
essentially as the Voss machine. The machine requires an initial charge
to start, and produces sparks with 1" of length. Back
view, Lateral view.
- A Wimshurst machine with acrylic structure
made by Scott Nagel in 2000.
With disks with 14.5" of diameter, it produces sparks
with up to 6". Another spark. Note the
separated small balls in the positive terminal, and the good dimensions
for the sectors in the disks. The charge collectors, with some sharp
corners, were later modified.
- What is probably the largest working Wimshurst
machine was built by Paul
Hendriksen in 2000, for a technical show by ROVC
, in the Netherlands. The machine uses two glass disks with 2.15
meters of diameter (2 cm more than the large
machine built by Wimshurst in 1884), 12 mm thick. The output
voltage reaches 1 MV, producing sparks of up to
1 meter. It turns at up to 100 rpm, producing 10 uA of current. The
output voltage is too high for Leyden jars, and so two copper globes
are used as distributed capacitors. Details of
the driving pulleys and a curious discharging mechanism. A long
spark, another, and more sparks.
Eventually (by 2008), the machine was installed in the Technorama
museum, in Winterthur, Switzerland. Mr. Hendriksen also build several
other machines: A large Van de Graaff
generator, 2.5 meters tall, that produces 80
cm sparks. A sectorless
Wimshurst machine with 50 cm disks, that produces 28 cm sparks. It
uses an adjustable capacitor, seen here with its minimum,
medium, and maximum
capacitance, that allows control of the intensity of the sparks, between
a minimum and a maximum,
continuously. The machine uses charge
collectors at just one side, and to start it a simple
friction rod is used. A hand-cranked Van
de Graaff generator, with an unusual toroidal terminal. A small friction machine, with a 25 cm disk, that
produces 2.5 cm sparks. A curious electric clock,
powered by high-voltage between the two balls below. Detail.
Several high-voltage demonstration
- A big Wommelsdorf condenser machine with 10 55 cm disks was built by Serge Klein, in France, in
2000. It can produce 25 cm sparks and up to 0.7 mA of current. Frontal
views, from the left and right
sides, a view of the motor that turns it,
detail of the disks and inductors, and another
view. The disks are composed of three disks
glued with epoxy glue, with the central disks separating two sets of
intercalated sectors. The inductor plates are also enclosed between
plastic sheets glued with epoxy glue. It works better with the
neutralizer brushes removed, with the gap between the disks and the
neutralizer bars making the role of the gap in the neutralizer circuit
of the classic machines. The machine was
later upgraded to 12 disks, with better brush
supports, in an attempt to increase the output current. A spark
from the machine. Mr. Klein has also built other machines, as a Dirod, a
Wimshurst machine, a big Bonetti machine,
that produces 30 cm sparks, a machine
similar to a Felici machine with disks and
operating in open air, and a triplex sectorless
Wimshurst machine. Another view.
- A nice Wimshurst machine, built by Julian
Phillips, in New Zealand, in 2000. With 30 cm disks, it can
produce 7 cm sparks. Another spark,
and a description of it.
- A very simple setup was developed by Michael
Foster, in Los Angeles, USA, in 2001, to produce long
sparks by frictional electricity. He used nothing more than a long
PVC tube, a paper towel, a very simple Leyden jar capacitor, and a
special positive terminal to excite long sparks. A description
of his procedure.
- a Wimshurst machine, built by Luca
La Valle, in Rome, Italy. He built also other high-voltage devices,
as a Van de Graaff generator and a Tesla coil.
- A curious small Wimshurst machine, designed
by Fausto Gazzi, in Bologna,
Italy. Mr. Gazzi deals with ancient
instruments, and frequently makes restorations, as of this 4
disks Wimshurst machine.
- A nice Wimshurst machine, built by Chris Kitching,
from England, in 2001. Top view, detail
from the charge collectors, and a spark with 14.5 cm produced by it. The
acrylic disks have 36 cm of diameter and 4 mm of thickness, and are
mounted on nylon bosses. The balls at the spark gaps and joints are
softened steel balls.
- This and this
Bonetti machines I found at eBay. They are similar to the machine
described by R. A. Ford . Builders unknown.
- Tony J. Meijers, in the
Netherlands, built this nice Wimshurst machine.
With 37 cm disks, it produces 14 cm sparks. Note the driving system,
without crossed cords. Front view. Back
view. He built also this Triplex Wimshurst
machine, in 2000, that with 41 cm disks produces 24 cm sparks. It
also has a curious implementation of the driving system, with the
driving axle making an angle of 10 degrees with the upper axle, so the
crossed cord that drives the central disks don't touch itself at the
crossing. Front view. Back
view. Side view. Other
view. Assembly of the disks. A thick 24 cm
disk at the center and disks at the outer sides impede sparking to the
center of the machine. The Leyden jars also have increased insulation.
- Georges Hublart, from France,
built this Wimshurst machine, motorized and
with a curious construction. Side view. With
33 cm disks, it produces 16 cm sparks. Note
the chains driving the disks. He has also other high-voltage devices, as
a Van de Graaff machine.
- A Wimshurst machine, with conductors
insulated within PVC tubes and LP record disks covered by adhesive
plastic foil, built by Ben
Noviello, USA, in 2002. It produces 10 cm sparks.
- A Wimshurst machine, built by Rod
Heidel, from the USA, in 2002. With 20 cm disks, it produces 5 cm
sparks. The frontal structure is a capacitor.
- A beautiful Wimshurst machine, built in
cherry wood and brass by Gerald
J. Schaefer, from the USA, in 2002. The disks have 18" of
diameter. Side view, Frontal
view, With two demonstration devices. An intense spark from it.
- A symmetrical Toepler machine, built by J. Keverline, from the
USA, in 2002. With 30.5 cm disks, it produces sparks
with up to 16 cm. The disks have increased
insulation with a material used to insulate tool handles. This resulted
in voltage high enough to pierce the spark shields, that had to have
their thickness increased to 4 mm.
- A Wimshurst machine that was once used for
demonstrations at the Science Museum,
in London, England, restored in 2002 by Rob
- A large Bonetti machine, built by Karl
Kehrle, in Germany, in 2003. With 80 cm polystyrene disks, it produces
63 cm sparks, between a pair of aluminim balls (8, 12 cm) at the
positive terminal and a 30 cm styrofoam ball covered with aluminum foil
at the negative terminal. The glass Leyden jars have 720 pF each. Mr.
Kehrle wrote a book
 showing experiments with a similar sectored machine, that with 90
cm disks produces 47 cm sparks.
- A Toepler machine with 48 cm disks, built by
from France, in 2003. This improved version,
with the inductor plates mounted inside a box, worked better. This is a
curious Van de Graaff generator also built by
him, that can produce 30 cm sparks. This is his Van
de Graaff with external belt. He also built a Dirod
machine. Another view.
- A sectorless Wimshurst machine, with 60 cm
disks, built by Grant
Vincent Wells, in New Zealand. It can be operated by hand or by a
motor, has an electronic startup system, and produces sparks with up to
- These two machines were built by Alan
Kerley. The larger machine is a Voss machine with a 21" and 17.5"
disks, and the other is a small Wimshurst machine made from CD disks.
- This is a Wimshurst machine made by Keith
Stuart, by 2000, in New Zealand. It produces 10 cm sparks. He also
restored an old machine (probably German, from around 1900) for the
Auckland Museum of Transport and Technology. Front
view, back view. By the end of 2003, he made
a curious combination between a symmetrical Toepler machine and a Dirod.
Side view, other
side, top view, end
view. With 12 cm disks, it produces 4 cm sparks.
- A motorized Wimshurst machine, made by Thomas Rapp, in Munich,
Germany, in 2004. Another view. The disks have 30 cm of diameter. More
informations and other projects can be found at the author's
- A Van de Graaff generator, made by
Richard Linder, in Burlington, USA. The terminal is a stainless steel
sphere with 45 cm of diameter. The bottom roller
is made of Nylon, and the top roller of
Teflon. The belt is made of 0.4 mm Mylar foil. Mr. Linder makes demonstrations
using it at the Burlington Science Center. For the 2004-2005 school
season, he built a larger machine, with a
36" terminal. The 6" belt is made of vinyl impregnated nylon. It
produces arcs with 18" to 24" to a 1.5" grounded sphere.
- A Wimshurst machine, built by Ricardo
Triches, in Brazil, in 2004. Another view.
- A big Van de Graaff machine, built by Harold
Pollner, in California, USA, in 2004. The terminal has 30" of
diameter, the comumn is 9" PVC, the belt is made with 4" Neoprene, and
the machine is powered by a 1/4 hp 1725 rpm ac motor. Excitation is by
rolling friction between the belt and the lower roller, that is a 4" PVC
coupling mounted over a wooden core. It produces 22" to 27" sparks, but
from the rim of the sphere opening to a grounded target electrode
positioned below the sphere, (as in the picture). Sparks from other
points of the sphere reach only 6" to 7".
- A small Wimshurst machine, with 20 cm
disks, built by Hannu
Eloranta, from Espoo, Finland, in 2005.
- A nice Wimshurst machine, belonging to Dr. Alistair Miller,
England. The machine has 19" disks and produces 6.5" sparks. It was
built by Anthony Swift, that runs a museum
dedicated to Victorian science in North Yorkshire, England.
- A motorized
Wimshurst machine, built by Peter
Bradley, in England. Spark picture.
- A curious friction
machine built as a Gramophone, by Kaj
V.M. Heiden, in the Netherlands. A spark.
- Several Wimshurst
and Bonetti machines built by Jarrod
Kinsey. Another view. He experimented
also with Wimshurst machines with sectors
made with conductive ink with excellent results. Some laser
experiments powered by electrostatic machines. An interesting comparison of sparks. This is a Holtz
machine completed in January 2009, with simple construction but
excellent performance, as seen on this
video. Another view.
- A Wimshurst
machine, built by Christophe
Branger, in France, in 2006. Another view,
and another. Spark,
- A Wimshurst
machine, built by Emiliano
Covarrubias, from the Universidad de Sonora, Mexico. The acrylic
disks have 40 cm of diameter, and the structure is made of polystyrene.
It procuces 6 cm sparks.
- A big
Bonetti machine, made by Hal Pollner, in the USA, in
2006. With 25" disks, it produces 11" sparks. A Van de Graaff generator
is used to excite the machine.
- A well built Wimshurst machine, built
Giacomelli, in Italy, in 2006. All parts are made in machined
metals and acrylic. Front view, charge
collectors, lower pulleys, upper
pulleys and insulated neutralizers, and top
view. The disks have 40 cm of diameter, and it produces 16 cm
- Two Lebiez machines, one hand-cranked and
other motorized, made by Milan
Manchich in 2007.
- Two Wimshurst machines made by Brian
Philips in 2007. First machine,
another view. It uses a flat capacitor
instead of Leyden jars. Second machine,
machines and other devices, built by Luiz
Alberto Feijó Junior, in Brazil.
- A Wimshurst
machine built by Vaughn
P. McDowell by 1986. Back view, side view.
- A set of
machines, Wimshurst, Voss and Ramsden, built by Leonardo
Cannone, from Italy.
- A big
machine, with 61 cm disks, built by Haywood
Turner, from the USA.
machines and Van de Graaff
generators, built by Harry
McCarty, from the UK.
- An electrostatic
motor, built by Dan
Bowlds, from the USA.
- A Wimshurst
machine, rebuilt by Rod
Heidel in 2008. The original is described above. One of the Leyden
jars exploded in a test due to glue vapors inside the PVC tube. So, take
care with ventilation on these constructions...
- A Wimshurst
machine, built by Carlos Alberto Vargas Alfaro, from Peru, in
2008. There are some videos
- A Wimshurst
machine built by Kevin
Acres in 2008. Side view. The machine, compared to another machine built by his
grandfather 70 years ago. Back view. The
machine has 27 cm disks, and produces 8.5 cm sparks.
- A sectorless
machine, built by David
Hodges, in 2008. It uses combs in the charge collectors,
neutralizers, and inductor chargers.
- A Wimshurst
machine, built by Rosalino
Trobbiani, from Italy, in 2008.
- A beautiful Wimshurst
machine, built by Jon
Bodsworth, in England. The machine was originally built 25 years
ago, and recently (2008) reformed. Front view,
side view. The glass disks, coated with
shellac, have 22 cm of diameter. The machine produces 6
cm sparks. The structure was made with mahogany and brass, the
insulators were made with polyester resin, and the sectors were cut from
aluminum litho plates.
- A Voss
machine, restored by Alan
Recce in 2009.
- A Wimshurst
machine with classical look, built by Douglas
Johnson, in 2010.
- A Wimshurst
machine, also with classical look, built by Leonard
Solomon, in 2010. Another view.
- A powerful Bonetti
machine, built by Günter
Pecher, in Germany, in 2010. With 60 cm disks, it produces 40
cm sparks. Another view. He built also
this Van de Graaff generator, with a 70 cm
terminal, that produces 60 cm sparks.
- A great collection
of electrostatic machines, belonging to Jaap
Slikker, in the Netherlands.
- A sectorless
Wimshurst machine built by PV
Scientific Instruments, being used by a company in the US for
tests of sensitivity of communication equipments to static
electricity, after some modifications to reduce leakage. The machine is
used with this ion emitter. A photo
of the machine in the dark, showing corona covering the positive
side of the disks.
- A Bonetti machine built by Jeffrey
Keverline, from the USA. Top view.
Long sparks (~30 cm). Note the lower
axle monted at an angle to avoid rubbing in the crossed cord.
- A Bonetti machine with 49 cm
disks made by Rosalino
Trobbiani, from Italy, in 2010. Side
- A Wimshurst machine, built by Douglas
R. Johnson. Second version,
improving the spark gap. Another,
smaller machine with 8" disks, built in 2011
to test how small the sectors can be. With so small sectors it needs an
initial charge to start.
- A Van de Graaff generator, built by Julian
Phillips, from New Zealand. A description.
Sparks along the tube. More sparks.
Short sparks to a grounded sphere. Long
- A Van de Graaff generator, built by Douglas
R. Johnson in 2011. It produces 8" sparks to the ground terminal.
- A Bonetti machine, built by Leonard
Solomon in 2011. It has 14" disks and produces sparks of almost
6". It can be easily excited by holding an electrized PVC pipe near one
of the disks (in front of a neutralizer is usually the best) and holds
charge for days in dry weather. Detail of the terminal
assembly. Tensioner. Charge
- A nice Wimshurst machine, built by Joachim
Oberhage, from Germany, in 2011. Details
of the machine. Another Wimshurst machine
built by him. The machines use wood supports for the charge
collectors, what I would not recommend, because wood is a bad insulator
unless very dry. Even so, they produce 8 and 2 cm sparks with 30 and 20
- A Wimshurst machine with unusual structure,
built by Francesco Trevisan, from Italy. It uses two 40 cm disks powered
by PC cooling fan motors.
- Some Van de Graaff generators built by
Kees Kuyper, based on the
commercial scientific toy "Fun
Fly Stick". One of them. Another
curious machine is this double generator,
where one of them is suspended by the belt, having no support tube.
- An artistic Wimshurst machine, built by
Hans Wissmeyer, in 2013. With 24
cm disks it produces 6 cm sparks. Another view,
lateral view, and a video.
- A Wimshurst machine, built by Jens Thiergärtner, from
Germany, in 2013. With 32 cm disks, it produces
13 cm sparks. The construction is in acrylic
and aluminum. The neutralizer brushes use
carbon fiber. Back view.
- Disassembly for
restoration of a Wommelsdorf condenser
machine, by Frank James.
- A nice Wimshurst
machine with the driving axle perpendicular to the disk axle,
built by Mark Winquist,
in 2015. It has quite thick disks, 1/4"
thick with 12" of diameter, but works very
well. It was initially designed
with the software Sketchup.
- The first electrostatic machine , was
built by Otto von Guericke  by 1663,
using a sulphur globe frictioned by hand. The globe could be removed and
used as source for experiments with electricity. A picture of a working
replica of the machine, from the University of Oldenburg.
- Another important early researcher was Francis Hauksbee, that built
several machines using glass globes 
and cylinders by 1705.
- The friction machines were gradually improved through the works of
many researchers. This is the machine with a glass globe of the abbot
Nollet (~1740) . Eventually, the machines took a stable form,
with leather friction pads (Winkler, 1744), glass globes (Bose,
1751), and insulated charge collectors. Demonstrations
with these machines were common.
- Watson's machine  (1746) had a large
wheel turning several glass globes. The prime conductors were a sword
and a gun barrel suspended from silk cords. Watson made many experiments
with the Leyden jar, then recently invented.
- A Ramsden electrostatic friction machine
. Another picture , another
, a good drawing , and a picture of a
large machine . The first popular machine
using a disk (1766). Designed by J. Ramsden, an instrumentist that also
designed many other good instruments in the 1700's. A beautiful restored
Ramsden machine, found at eBay
in 1999. Photos by Fausto Gazzi.
This large machine I found in a museum
in Geneva, Switzerland. A simpler machine built by myself is shown in
the first section of this page.
- The machine of Le Roy (1772) [p26] was
suitable for the production of long sparks, due to the high insulation
between the friction pads and the charge collectors (see a more modern
version as the Winter machine, below).
- This large disk machine (1785) with 1.6 m
disks can be seen at the Musée du Conservatoire Nacional des Arts et
Metiers, In Paris, France. On its base is written the motto at the top
of this page. There is a picture of it in .
- A brass model of a Ramsden machine. A curious
decorative object, possibly from the 1930's or before. The disk has 3.5"
of diameter. Photos sent by Blake
- A Nairne electrostatic friction machine
, built in 1770, consists in a glass cylinder, a friction pad in one
side, and a charge collector in the other, both connected to insulated
conductors. Another one. The machine was used
for medical purposes.
- The van Marum electrostatic friction machine
(1784) . By moving the two curved bars with charge collectors, it was
possible to collect charge from the disk (bars as shown), or from the
friction pads (bars turned 90 degrees), producing voltage with any
polarity, as shown here. Van Marum is also
known for the big machine  that he
had made in 1784, that is now in the Teylers
- A similar machine, now in the Deutsches Museum, Munich, Germany,
belonged to Georg Ohm (1830?). Another view.
Photos sent by Hans
Bussmann (I could not find it there in september 2008).
- A belt machine  built by N. Rouland by
1785, had a charge collector with blades that collect charges from a
silk belt rubbed by two grounded tubes covered with hare fur .
- An old friction machine using a glass disk.
Another picture of the same machine. Photos
sent by Don Day.
- A Winter electrostatic friction machine. One
of the most efficient friction machines. A picture
from an old book , and another, from H.
Pellat . This was the last popular structure for friction machines,
as shown in these catalog pictures from the 1920's: this
and this are from , and this
is from . The characteristics of the machine are the disk frictioned
at one side, at both faces, with a pair of charge collectors at the
other side, shaped as rings with points turned to the disks. Sometimes a
large wood ring (Winter's ring) with a metallic core was attached to the
terminal, increasing its capacitance. A double adjustable version can be
seen on the first picture.
- The Woodward machine (1840)  was a
modified Ramsden machine, with the prime conductor located above the
disk, or disks, saving some space. It could also generate negative
voltage, by mounting the upper friction pad in place of one of the
charge collectors. This double machine is
in the University of Porto, Portugal. Partially disassembled.
Pictures by Marisa Monteiro.
- The Armstrong hydroelectric machine , a
friction machine using steam as charge carrier (1840). It is just an
insulated boiler producing a steam jet mixed with water droplets. A
better picture is here . Very powerful
machines of this kind were built for research.
- The Lorente generator. A triboelectric
machine composed of four cylinders that roll together without friction,
under a slight pressure. The two outermost cylinders are metallic, and
the two central cylinders are of distinct insulating materials (nylon
and teflon). Opposite charges are collected in the metallic cylinders.
The basic machine produces voltages of some tens of kV, but several
modules can be stacked for more voltage. A coaxial
version is also possible. Pictures from actual models are here
and here. This device was invented and
patented by G. Lorente, who
sent the pictures.
- Rolling friction is also commonly used in models of the Van
de Graaff generator, although the principle of the charge
generation system on those machines is a mix of friction and influence.
- The largest classical friction machine was
built for the "Royal Panopticon of Science and Arts", in 1854.
- The first rotating influence machines were the "doublers". The first
was Nicholson's doubler [p14] (1788). It was a
rotating implementation of Bennet's
doubler (1787), a device based on Volta's
"electrophorus" (1775) [p110], that allowed great multiplication
of a small initial charge by a series of repeated operations
with three insulated plates. The original machine proposed by Nicholson
didn't require a connection to ground, but versions with explicit ground
connections are also possible, as this
[p115], designed by Desormes and Hachette, and this,
built by Wimshurst [p14]. An actual machine
exists in the Musee d'histoire
des sciences, in Geneva, that looks as this
machine (John Read's doubler) [p106][p114]. A version
of Nicholson's doubler used by Volta can be seen at the Tempio
Voltiano. See my
Nicholson's doubler. A similar implementation, where the two
plates that are fixed in Nicholson's device rotate, is Bohnenberger's
machine (1798) . Bohnenberger designed several other doublers,
as this automated
version of Bennet's doubler and this variation of Nicholson's doubler (1801)
[p107], both operating with back and forth movements. See my Bohnenberger's machine.
- Multipliers based on a different system are also possible, as Péclet's
condenser (1841) that increases the charges linearly with the
number of operations [p87] and a multiplier
with 4 plates invented by Pfaff and Svanberg
(see my version)
that combines addition and multiplication . Multipliers directly
based on the electrophorus were studied, by Volta himself [p110] and
- A similar adding device was Cavallo's
multiplier (1795), where a movable insulated plate was moved back
and forth, alternatively being grounded under the influence of a second
previously charged plate, and touching a third insulated plate close to
a grounded fourth plate. After some cycles, the grounded plate would be
removed, causing the accumulated charge at the third plate to rise its
potential to about the potential of the second plate times the number of
- Two Cavallo multipliers can be combined in Wilson's machine (1804), a curious machine that
incorporates essentially the same idea of the symmetrical rotating
machines developed much later.
- One of the scientists that studied doublers was Erasmus Darwin. His "commonplace
book" contains a sketch of a doubler,
that appears also in [p14], that is probably the first drawing of these
devices. His book "Phytologia" contains a drawing of a "pendulum
doubler", attributed to Bennet (see here).
- The next development was of symmetrical influence machines, using
influence to generate new charges and Faraday's shielding effect to
collect them. The first was Belli's machine
[p14] (1831), the first symmetrical influence machine. My Belli machine. A picture
of an elaborated actual machine. Belli developed also a different
machine using the same principle, shown here.
The same basic structure appears in Lord Kelvin's
"replenisher" [p92] (1867), in
schematic representation, and as constructed
. A simple machine built with insulated curved metal plates, used as
part of measurement instruments. Here
is a ray-tracing picture similar to a machine that I built by 1973. The
rotation of the central insulating bar with two metallic carriers,
touching the four contacts, causes accumulation of opposite charges in
the outer plates. Another similar machine was the Varley
machine  (1860).
- A device that can be considered an influence machine is Einstein's
"Maschinchen" (little machine). It was a mechanical voltage multiplier
resembling a multistage Belli machine without feedback. This
paper describes it.
- A curious machine  that appears to be
similar to Belli's machine, if the lateral brushes are connected to the
fixed plates. The same machine appears illustrating this advertisement
(1962) but with an added set of brushes installed, to separate the
output circuit from the inductor plates, as in the Voss machine.
- The Piche machine, or Bertsch machine
(1866) . One of the simplest influence machines, uses an insulator
plate (I), that is separately electrized by friction, and used to
generate charges in the rotating disk by induction. See the original
letters about this machine in the references.
A similar device is the Dubrowski machine
. This type of machine was called "continuous electrophorus".
- The Carré machine  (1868). A friction
machine below charges by induction a fast rotating disk, that transfers
charge to the upper conductor. It is similar in operation to the Bertsch
machine, but regenerates the charge in the inductor. A
better picture . A variation 
with slanted combs. A ray-tracing drawing. A photo from an actual machine, sent by John
Newman. A machine with a double terminal.
The Van de
Graaff generator [p4] is an evolution of this machine, with a
belt instead of the disk, and a more efficient charge collector at the
top. This machine is in a museum in
Switzerland. Another machine, in a Museum
- A double Bonetti machine from the same
museum, with curiously shaped neutralizer combs (?).
- The Cecchi machine, or "dielectric machine"
(1868) is similar to the Carré machine, and was developed a few months
before [p118], by Filipo Cecchi [p119], an
- A version with double excitation of
the Cecchi/Carré machine can be seen at the Museo
Galileo, in Florence. Another view.
The two friction machines, with glass and ebonite disks, generate
opposite charges, and the central ebonite disk is used as a current
- Another antecessor of the Van de Graaff generator is Righi's
electrometer [p55] (1872), that used a rubber string with brass
rings for charge transport, and a hollow sphere as charge collector. A picture of this machine . Similar machines
are also discussed in [p59] (1875), as a bipolar
machine, that must have grounded pulleys, and another,
that adds a neutralizer circuit and can use insulated pulleys.
- Righi studied also a belt machine [p59],
that antecipates a regenerative charging system used in some Van de
Graaff machines, and shows a curious polarity reversal phenomenon, where
for some time the belt operates with bands of both polarities.
- Righi designed this big Holtz machine 
(~1875), used at the Regio Istituto Tecnico de Bologna for teaching and
research. A drawing of a similar machine
- A Lord Kelvin's water machine (1867) [p91]. It is an influence machine that uses
water droplets instead of rotating carriers. It works in the same way of
the 2 disks Toepler
machine. Another picture  of a similar
machine. An improvement of this machine using two additional units for
output, avoiding the discharge of the inductors, was proposed by Fuller
in 1888 [p103] [ p62]. A different
version was proposed by Sylvanus Thompson in 1887 [p104].
- The Schwedoff influence machine 
(1868). A very strange machine. The lower plates form a modified Holtz
machine, with inductor plates replaced by combs (dotted lines) charging
the lower surface of the lowest fixed disk with charge taken from the
charge collectors. This first machine provides bias for the sectors in
the lower plate of the upper assembly (the even-numbered ones with one
polarity, the others with another), that form a current multiplier. The
output is taken between the two insulated sets of combs over the upper,
rotating disk. This picture from the original
paper [p46] shows more clearly the connections. This is the charge
collector [p46] that completes the machine.
- A Toepler-Holtz machine, or Voss machine
with classical design. From a catalog from the 1920's. Two more pictures
here and here.
Pictures found in the Gemmary's forum.
- Several Toepler-Holtz, or Voss, machines from : A simple
machine, another, a double
machine, a quadruple machine (see one here),
and a multiple machine. Two more simple
machines from : this and this.
And another one, from .
- A magnific quadruple Voss machine, at the
museum of the University of Pavia, Italy.
- A Holtz-Wimshurst machine , simple
and with a frictional starter . These
were Holtz-type machines with several disks and improved construction,
as the inductors fixed in separate square glass plates, developed by
Wimshurst by 1878.
- The Kundt machine  (1868) was a mixed
friction-influence machine, similar to a Bertsch machine with the back
side of the disk frictioned by a friction pad with a silk flap attached,
as in a friction machine. At the front side are positioned two charge
collectors, as in the Bertsch machine. A similar machine was the Cantoni
machine (1869), that added a third charge collector at the back side of
the disk, so the machine can also be used as a friction machine.
- A good picture of a classic Wimshurst machine
(1883) . A Line drawing of the same
- A Wimshurst machine , similar to one
that exists in the Museum
of the UFRJ Engineering School, and that I restored. Another
 similar machine. That machine was built by F. Ducretet and E.
Roger, Paris, and originally should look as in this
(front) and this (back) ray-tracing drawings.
Here are comments about the restoration and
more pictures. This is how it is now, compared
with my 1974 Wimshurst. A large spark
produced by the machine in a demonstration. Another picture, showing two
of these machines connected as a generator and
motor pair . These pictures  show discharge images on
photographic plates obtained with one of these machines. A positive
discharge, and a negative discharge. A multiple
machine from the same instrument builder, at the University of
- Here is another Wimshurst machine from the
same museum that I restored (ray-tracing), a picture
of it, and some comments about the restoration.
- The largest Wimshurst machine ever built is
presently at the Science and Industry Museum in Chicago, USA. It was
built in England in 1885, with 7 foot glass disks 3/8 inch thick, and
produced sparks with 22 inches. This picture is from Engineering, Vol.
39, 1885, scanned from  (also appears in ). More informations
and pictures about this machine.
- More Wimshurst machines, from : A large simple
machine, a double machine, a quadruple
machine, and an octuple machine. And also two
machines from , with ebonite disks and
Leyden jars with two sections, and with glass
disks. Two more large machines from : A simple
machine and a quadruple machine.
- Wimshurst machines, from the collection belonging to Louie
Scribner: A French machine (Bonetti),
and a German machine (Leybold, 1901).
- Wimshurst machines that have full construction details in : A laboratory machine, a long
spark machine, and a twelve plates machine.
Designs by J. Wimshurst.
- A "Voltana" Wimshurst machine (1921),
used to run an electrostatic motor, and a bank
of Geissler tubes. A larger
machine, a smaller machine, another
machine, more Geissler tubes being lighted,
lighting a spinning Geissler tube, charging a
Leyden jar, and charging a spring,
that expands when charged .
- Several machines, from , that illustrate the state of the art by
1900: A classic Wimshurst machine made by
Bonetti, with Leyden jars that support the terminals, a complex double
machine and a large multiple machine made
by Ducretet, and a machine with large conductors,
that act as capacitors. The classic Bonetti
sectorless machine, a multiple Bonetti machine,
and a double Bonetti machine.
- Some multiple Wimshurst machines: A double
machine, built by the instrument builder E.
Balzarini, similar to the machines that appear in its 1907
catalog. Note the triple brushes at the neutralizers. A quadruple
machine, built by Newton & Co.
Back view. Detail from one of the charge
collector assemblies. Pictures from eBay
- Wimshurst machines with an orthogonal drive
system were built by companies as Central Scientific Co. A machine
with the Leyden jars serving as terminal supports. A small unusual
German machine. A larger
machine, and a big machine . One of
the pulleys below is driven by the crank. The other runs freely 1.
- A Wimshurst machine with cast iron
structure, including the neutralizers 1.
- The Wimshurst machine can also be built with cylinders
instead of disks . A more practical structure was designed by Lemström  (1899), with the two
cylinders turning around a fixed central axle, that also holds the
internal charge collectors and neutralizers.
The axle was separated in two sections by an insulating block at the
center. The machine was kept warm, dry, and ventilated by a heating
system and the sides of the cylinders, shaped as fans. See his patents.
- The Wimshurst alternating machine (1891),
that generates alternating voltage, synchronized with the rotation, with
a polarity reversal at each 3/4 of rotation of the disk. The operation
of this machine was considered difficult to explain . A single disk
with sectors at both sides, alternating, rotates between two pairs of
collectors/inductors. Picture from Engineering.
- A triple Bonetti machine . This kind of
multiple machine was used in early X-ray work.
- By June-October 1999 I restored a similar quadruple
Bonetti machine, built by Radiguet & Massiot (~1910), for my
university's museum. Some pictures of the machine
during initial tests and a report about the restoration are available.
- Another double Bonetti machine , with
- A cylindric Bonetti machine . A compact
design with high current output. This appears to be a large
machine built by Bonetti by 1894, where the cylinders had 50 cm of
diameter and height [p78]. Another cylindric
- A machine that appears to be a sectored Holtz
machine , said to be quite powerful. There are fixed inductors
on the back plate, that are charged by sectors at the back of the
rotating disk through brushes that project through two holes in the
- A motorized Voss machine with a fully
sectored rotating disk .
- P. V. Schaffers (1885) [p29][p32] described a machine that is
essentially a Wimshurst machine with the charge collectors at different
positions, with brushes at the charge collectors. The Schaffers machine
works as a combination of the Wimshurst machine and the Holtz machine of
the second kind, producing higher current (schematic).
A (bad) picture of a Schaffers machine .
- "Pneumatic machines", operating in compressed
air or other gases, were developed after experiments by W. Hempel
described in 1885. The high pressure increases the breakdown voltage,
allowing greater voltages and currents to be obtained.
- A Wehrsen machine [p77]
(1907). Wommelsdorf's idea, it is a highly insulated sectored
Holtz-style machine with sectors embedded in the rotating
disk, contacted through small buttons, and inductors
 also totally insulated behind celulloid plates. Some machines had
corrugated sectors for greater surface area, what increases the output
current , or mounted at different planes for higher insulation .
They had switches to allow the direct connection between the inductors
and the output circuit, for startup as a "replenisher" machine . Two
better pictures from : A large machine,
and a small machine. A simple
machine, and a large machine, from . A
machine with direct motor drive . A similar
machine [p77]. Wehrsen's "Mercedes"
machine , with one rotating disk, and with two
rotating disks, one at each side of the fixed disk. A similar machine, built in 1911, exists in the Cavendish
Laboratories, England. left view, right
view, back view. Detail from the switches,
and from the central inductor plates. The
machine is normally under an enclosure, and was disassembled for
cleaning and investigation of why it doesn't work anymore in 1999.
Photos sent by Tacye
- The Wommelsdorf condenser machine
[p84] (1902-1920) was the last of the classical disk
machines. It was basically a sectored Voss-style machine with double
induction plates, one pair at each side of the rotating disk, and with
all the sectors and inductor plates enclosed in ebonite plates. Some
models had a switch in the middle of the neutralizer bar. A simpler model . In the last versions, the disk had
a full set of embedded sectors, monted in alternate groups separated by
one or two thin insulating disks. The sectors were touched only at the
borders of the disk by brushes running in a V
groove there. The ebonite disk was covered by a material (celluloid or
bakelite) resistent to deterioration caused by ozone and other gases
produced by electrical discharges. . Schematic
diagram . Versions with multiple sections were also built, with some
versions combining different charging systems for the inductors, with
alternate sections charging the inductors from brushes at the edge of
the disks and others from brushes touching the sides of the disks, as in
a Holtz machine. Another version  with
older design, totally enclosed and with fixed contacts for the
neutralizer. Partial schematic diagram. A similar machine [p80], another,
an open machine, and a very
large machine [p81] along with a small
machine. A condenser machine powered by a steam
engine . Wommelsdorf designed also machines with pairs of
disks rotating in opposite directions [p83], similar to multiple Wimshurst machines, as this
, a triplex Wimshurst machine with a
central disk accessed through the edge.
- Several of the papers and patents
by Wommelsdorf are available here. See also my
- See some tables with the performances of
- The Pidgeon machine  was a Wimshurst
machine with fixed inductors positioned in a way that increases the
induction effect. Fixed inductors with same polarity of the opposite
disk were placed surrounding, insulated, each neutralizer brush. The
sectors were embedded in the disks [p53][p54][p111].
Pidgeon studied also machines based on "triplex
Wimshurst" sections (double machines with a single central disk),
with enclosed sectors, that produce more current. The first Pidgeon
machine had a quite strange structure
[p111], and the disks had slanted sectors for more uniform induction.
- Piggott made a set of experiments with radiotelegraphy and
"antigravity" using a compact double Wimshurst machine enclosed in a
pressurized box. Drawings from his patent
(1911) showing the machine. Front view, side view, top
- A "Dirod" generator. A modern electrostatic
machine, designed by A. D. Moore . It is a cylindric machine similar
to the Belli machine, or Lord Kelvin's replenisher, with metal rods as
carriers. The output is taken at the inductors.
- Another machine described in A. D. Moore's book  is the "shake-sphere"
machine. It is electrically equivalent to the symmetrical Toepler machine or the earlier Wilson's machine.
- From the 1940's to the 1960's, Nöel J. Felici, in France, developed a
series of high-power electrostatic generators
, initially for applications in research.
by Lyonel Baum, contains many informations about his work.
- Large medical electrostatic machines
were common around 1900, used for electrotherapy and radiography, and
were probably the most elaborate of these machines ever built.
- See also the several machines that I have built, in the section "my
machines", above. The linked pages have many informations about the
Other high-voltage devices, not
- Changing of subject, an Induction coil
, or Ruhmkorff coil (1851). A "fly-back" circuit with a mechanical
interruptor, that eventually replaced the electrostatic machines as a
practical source of high voltage. Its schematic
diagram , ommiting the secondary of the transformer, that is
wound with many turns of thin wire and well insulated. By 1867 Ruhmkorff
(instrument maker in France) was making coils that could produce sparks
with 40 cm. A spark image (16 cm) obtained
with one of these machines, with the terminals applied to a photographic
plate . The positive terminal was in the left.
- The Planté rheostatic machine. It produces
high voltage by charging a bank of capacitors in parallel and
discharging them in series. The connections are made by contacts in the
rotating cylinder . The input is obtained from a battery.
- A resonance excitator , with adjustable
inductances (L1, L2), Leyden jar capacitors (C1, C2), and a spark gap,
used in old experiments about resonance.
- Self-resonant coils  with different
lengths, that emit corona discharges when driven at their resonant
frequencies by the excitator above.
- Connection between an induction coil (J),
the excitator, and the resonant coils (Seibt experiment) . By
changing the excitator inductance, it is possible to put one or another
of the self-resonant coils in resonance. This experiment is a variation
of the "Tesla coil"
circuit, using a direct connection instead of a transformer. See my implementation of a similar system, and
follow the links to see my other experiments with multiple resonance
- Complete apparatus for the Seibt experiment
. A variation using a large open primary
coil . A curious experiment using a Tesla coil and a long
resonator coil, where corona to two wires demonstrates standing
- A classic Tesla transformer . A primary
coil with a few turns of heavy wire (or tubing), and a well-insulated
secondary with many turns. It produces a similar result if the primary
is inserted in series with the spark gap in the excitator above. Several
Tesla coils, from .
- Apparatus for Tesla experiments, with an usual
Tesla transformer, and with an oil-insulated
transformer . A large Leyden jar capacitor is connected in series
with a spark gap and the primary of the transformer. The capacitor is
charged by an induction coil, or a powerful influence machine. The other
devices shown are for demonstrations of the effects of high-frequency
high voltage. Similar apparatus with the usual air-insulated
transformer , and an experiment to demonstrate the high impedance of
a wire loop, using a Tesla coil with the primary coil inside
the secondary .
- An Oudin coil (1898) , a Tesla coil with
the primary and secondary windings forming an autotransformer. Another Oudin coil . See also my Tesla coil, that can also be operated as
an Oudin coil.
- A machine  invented by Elihu
Thomson (patented in 1900) used a
rotating frame driven by a DC motor with short spark gaps to connect a
group of capacitors in parallel or in series. The capacitors were
charged in parallel by a transformer powered by a slip ring connected to
the motor, with the operation synchronized so the charging was done at
some of the peaks of the transformer output voltage. Another picture
Toepler, Wommelsdorf, Holtz, and Unfolded Wimshurst machines
- Some final observations,
about pseudo-science, safety measures, and troubleshooting.
- Calculating the output
current of electrostatic machines.
- References - Books,
papers and patents about electrostatic machines, cited
between "" in the text.
- See also my links
about these subjects.
- Group in Facebook.
- Links to e-mail addresses or collaborators had the "@" replaced by
1 Found in the catalogs here.
Last update: 5 February 2015. Recent changes and updates.
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