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.
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.
A Wimshurst
machine [1][2] 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 [2], 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 [10].
A symmetrical 2
disks Toepler machine [4], 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
[4][9], 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 diagram [p39].
My first
sectorless Wimshurst machine, or Bonetti
machine [4][5][8] (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) [31] used series of brushes as
neutralizers instead of combs.
A Holtz
machine [2][4]-[7] 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 [6] (the fixed disk is in a wrong position), a better
picture [7], a double Holtz machine
[6][7], and a machine with neutralizer and
friction starter [6][7]. And another
good picture [14]. This picture shows a
machine with a more modern structure [22]. A multiple
machine [24]. 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 machine.
The Leyser
machine (1873) [4][19], 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 [19]. This diagram [19]
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)[4], 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 machines below.
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 machine.
In August 2000 I
made a version of Nicholson's
doubler, the first automatic influence machine (1788).
In January 2001 I
completed a double Wommelsdorf 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
Wimshurst machine".
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.
Bohnenberger's
Bennet's doubler. A curious little machine that I built in
April 2004.
Bohnenberger's
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 other doublers.
A rotating
Bennet's doubler, with a new construction using sectored
disks, built in 2006. Photo of the
machine. Another view.
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.
Bennet's
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 works. This
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 electrophorus: 1,
2.
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.
Replenisher
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 2011.
Some simple
high-voltage measurements.
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.
Double
electrophorus machine, made in April 2015.
Electronic
version of Wilson's machine, made in May 2015.
3D-printed
electronic electrostatic machines, starting in 2015.
A big Wimshurst
machine built by Jim Banas.
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 [8]. 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
Cole.
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 [10], 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
and here.
Ricardo
"Rike" built this Wimshurst
machine in 1997, using LP records for the disks. It produces 7
cm sparks. Another view.
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
view.
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 improved machine.
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 video
about the machine.
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 devices.
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 [8].
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
Skitmore.
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
[49] 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 Alain
Tramasaygues, 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 24 cm.
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
site.
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. Another
spark.
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,
another spark.
A
Wimshurst machine, built by Emiliano
Salinas 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. Another
view.
A well built
Wimshurst machine, built by Leonardo
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
sparks.
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, another view.
Several
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 Wimshurst machine, with 61 cm
disks, built by Haywood
Turner, from the USA.
Wimshurst
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 here.
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 Voss 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 R. 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
view. Sparks..
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
sparks.
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 collector.
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 cm disks.
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.
More details are available here.
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
Jones.
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.
A big
Van de Graaff generator, built by Luis
M. Buresti, from Argentina. The terminal has 60 cm of diameter,
an the latex belt has 10 cm of width. The pulleys have 5 cm of
diameter and turn at up to 3600 rpm. The machine can reach 450 kV
(measuring by spark length between spheres) at 15-17 μA. He also
built this Greinacher multiplier, that
can reach 300 kV. at 100 μA. The devices are being used in
experiments in nuclear physics.
The first
electrostatic machine [15], was built by Otto
von Guericke [16] 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 [50][53] 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) [7]. 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 [51][52] (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 [2]. Another
picture [7], another [12], a good
drawing [17], and a picture of a large
machine [14]. 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) [50][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 [21].
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
Awbrey.
A Nairne
electrostatic friction machine [7], 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) [9]. 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 [16][21] that he had made in
1784, that is now in the Teylers
museum.
A similar machine,
now in the Deutsches Museum, Munich, Germany, belonged to Georg Ohm
(1830?)[21]. Another view. Photos sent by
Hans Bussmann
(I could not find it there in september 2008).
A belt
machine [50] 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 [21].
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 [3], and another, from H. Pellat
[7]. This was the last popular structure for friction machines, as
shown in these catalog pictures from the 1920's: this
and this are from [17], and this
is from [22]. 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) [43][21] 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 [2], 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
[9]. 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 of electricity". 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. It was used as instrument for the amplification of
small charges, but could also generate electricity starting from
natural imbalances. The original machine proposed by Nicholson
didn't require a connection to ground, but versions with explicit
ground connections are also possible, as this
[28] or this [65][66], similar to the
one designed by Desormes and Hachette
[p115], and this,
built by Wimshurst [p14]. An actual
machine exists in the Musee
d'histoire des sciences, in Geneva, which 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) [4]. 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 [54]. Multipliers directly
based on the electrophorus were studied, by Volta himself [p110]
and Lichtenberg.
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 cycles [4].
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
[4][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"
[2][p92] (1867), in schematic
representation, and as constructed [12]. 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 [26] (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 [18] 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.
A machine simular
to a double electrophorus, described by G.
Fuller [p123]. It uses combs with points
to spread charge at both sides of an insulating plate, and then uses
two metal plates as in the electrophorus to obtain charges from it.
A regenerating system uses the extracted charges to reinforce the
charges in the insulating plate.
The Piche machine,
or Bertsch machine (1866) [7]. 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 [22]. This
type of machine was called "continuous electrophorus".
The Carré
machine [6] (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 [7]. A variation [14]
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][8] 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
in Spain.
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 italian researcher.
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
multiplier.
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 [41]. 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 [41] (~1875), used
at the Regio Istituto Tecnico de Bologna for teaching and research.
A drawing of a similar machine [42].
A Lord
Kelvin's water machine (1867) [1][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
[6] 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 [9][13][29] (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 [17]: A simple
machine, another, a double
machine, a quadruple machine (see one
here), and a multiple
machine. Two more simple machines from [18]: this
and this. And another
one, from [22].
A magnific
quadruple Voss machine, at the museum of
the University of Pavia, Italy.
Clarke's
lighter was a small Voss cylindrical machine used as a lighter.
Photos by Frank Jones.
The Shall
machine [64][5] was a variation of the Voss machine with the
inductor plates suspended behind slowly rotating insulating disks.
The idea was to prevent polarity reversals caused by charge
accumulation at the opposite sides of the inductors in machines with
fixed disks.
A Holtz-Wimshurst
machine [4][23], simple and with a frictional
starter [4][23]. 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 [4] (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) [1]. A
Line drawing of the same picture [2].
A Wimshurst
machine [6], similar to one that exists in the Museum
of the UFRJ Engineering School, and that I restored. Another
[14] 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 [24]. These pictures [23] 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 Porto, Portugal.
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 [23] (also appears in [4][5][8][26]). More informations
and pictures about this machine.
More Wimshurst
machines, from [14]: A large simple
machine, a double machine, a quadruple
machine, and an octuple machine. And also
two machines from [15], with ebonite disks
and Leyden jars with two sections, and with glass
disks. Two more large machines from [22]: 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 [4][23]: A laboratory
machine, a long spark machine, and a
twelve plates machine. Designs by J.
Wimshurst.
A "Voltana"
Wimshurst machine [34](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 [35].
Several machines,
from [38], 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 auctions.
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 [4][23]. A more practical structure was designed by
Lemström [5][8] (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 [5]. A single disk with sectors at
both sides, alternating, rotates between two pairs of
collectors/inductors. Picture from Engineering.
A triple
Bonetti machine [11]. 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 [26], with similar features.
A cylindric
Bonetti machine [11]. 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 machine
[26].
A machine that
appears to be a sectored Holtz machine
[22], 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 fixed
disk.
A motorized
Voss machine with a fully sectored rotating disk [26].
P. V. Schaffers
(1885) [4][5][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
[26].
"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 [1][26][27][32][34][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 [34]
also totally insulated behind celulloid plates. Some machines had
corrugated sectors for greater surface area, what increases the
output current [5], or mounted at different planes for higher
insulation [26]. They had switches to allow the direct connection
between the inductors and the output circuit, for startup as a
"replenisher" machine [32]. Two better pictures from [17]:
A large machine, and a small
machine. A simple machine, and a large
machine, from [22]. A machine with direct motor
drive [26]. A similar machine [p77].
Wehrsen's "Mercedes" machine
[34][26], 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 Phillipson.
The Wommelsdorf
condenser machine [1][17][18][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 [17]. 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. [5][8]. Schematic
diagram [27]. 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 [22] 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][46] along with a small
machine. A condenser machine powered by a steam
engine [46]. Wommelsdorf designed also machines with pairs of
disks rotating in opposite directions [45][p83], similar to multiple
Wimshurst machines, as this
[46], a triplex Wimshurst machine with a
central disk accessed through the edge.
Manual
of static electricity, from Wommelsdorf's company BEG.
Several of the
papers and patents
by Wommelsdorf are available here. See also my
Wommelsdorf machine.
See some tables
with the performances of several machines.
The Pidgeon
machine [26] 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 [5][26][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 view.
A "Dirod"
generator. A modern electrostatic machine, designed by A. D. Moore
[10]. 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 [10] 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 [40],
initially for applications in research. This
site,
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 machines.
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 forgotten.
