Small Wimshurst generator from cardboard and CDs
The Wimshurst influence machine was a popular machine at the end of the 19th century to generate high voltages.
From it’s development ~1883 it superseded other devices such as the “Holtz” and “Voss” machines. It was one of the first ways to generate high voltage to more or less conveniently take Röntgen pictures around the turn of the century. For example, this 1909 book on radiography: Radiography and the “X” rays in practice and theory with constructional and manipulatory details by S.R. Bottone has an interesting chapter on Wimshurst machines, how to hook them up to a Crookes tube and how to take X-ray pictures. My little Wimshurst machine should in theory be able to do the job, but it will take a very long time to get 10 good flashes. And the tiny crank is not ergonomic. And I don’t have a Crookes tube.
The Wimshurst machine got superseded around 1924 by more practical generators like the Marx generator which is still used today in laser printers and CRT television (Although those are getting obsolete too).
And for extreme high voltages, it got replaced around 1929 by Van de Graaff generators which were used for example for the early particle accelerators
This instructable will show how I built a small Wimshurst influence machine with two CDs, pieces of scrap cardboard and some tin foil. These are instructions for materials and tools that I had lying around, just to provide ideas for other people. Of course it would be better not to use cardboard and to make the device much larger.
The instructable consists of the following steps:
Step 1) First, the workings of a Wimshurst machine will be explained.
Step 2) The materials and tools are shown.
Step 3) CDs are cleared.
Step 4) Metal strips will be made from aluminium foil AND aluminium tape and glued onto the CDs.
Step 5) Wheels are made and glued to the disks.
Step 6) The axles are mounted in a support structure.
Step 7) A socket is made that will hold the mechanism.
Step 8) A base is made on which the Leyden jars and the mechanism will be mounted.
Step 9) Two Leyden jars are made.
Step 10) The neutralizer rods are made.
Step 11) A crank is made.
Step 12) The sides of the socket are closed up.
Step 13) The base is adapted so that everything can be mounted without them shifting around.
Step 14) The electrodes are constructed from wire and aluminium foil.
Step 15) Debugging
Step 16)The results.
A very interesting website containing all sorts of builds of all sorts of electrostatic machines is the following:
If you have any interest in this subject, it is really worth checking out.
There is also an other instructable: http://www.instructables.com/id/Whimshurst-Generat…
The build process isn’t really documented, but there is a list of materials. If you look at that, you can most likely find the equivalent in my machine with some documentation on its function and how it relates to other parts.
Step 1: How a Wimshurst influence machine works
As this is an electrostatic influence machine it evidently uses electrostatic influence or induction to generate static electricity.
This electrostatic induction is nothing more than the effect of a charge onto nearby objects without a physical contact. For example, a positive charge will attract a negative charge and repel a positive charge. Therefore, in a conductor, charges will be redistributed as to make the electrostatic potential constant throughout this conductor.
The classic example is an electroscope in the vicinity of (but not in contact with) a charged object.
This is a video of the youtuber RimstarOrg which gives a very good explanation on electroscopes. (he also made a CD wimshurst machine, but mine is esthetically a bit more elegant and requires far less tools)
Most electrostatic machines use inductance to produce a net charge in an object. The simplest version is an electrophorus.
If for example a positive charge is brought near a conductor, it can be seen that this conductor is polarized. (simply said, this positive charge moves all the (negative) electrons a bit towards it. And of course charge x vector is a dipole moment.)
Fig. 1 Conductor in vicinity of charge
One can now ground the end of this conductor which will remove the positive charge located there
Fig. 2 One end is grounded
If one then removes the connection to the ground and the inducing charge, one can see that there is a net negative charge left in the conductor.
Fig. 3 A net charge remains
This is a video of such an electrophorus in action. Check out the channel of this youtuber Thomas Kim. He has all sorts of interesting electrostatic machines made from PET bottles and CDs, he doesn’t provide much information, they are probably intended as demonstrations. He also has a CD wimshurst machine. (but mine produces bigger sparks. I did get the Idea of using aluminium tape for the second pair of disks from him.)
A Wimshurst machine and all other electrostatic influence machines are nothing more than elegant, mechanized versions of a sort of double electrophorus.
A Wimshurst machine consists out of two parallel, counter rotating discs with metal strips. The strips pass under so called ‘neutralizer’ rod which do the separating out of the charges on the strips and the strips also pass under combs which harvest the accumulated charge on the strips.
An excellent explanation of the workings of a Wimshurst machine can be found here:
It is however French, if you know some French, it definitely is worth a read (as it also gives instructions on how to use a Wimshurst machine for electrostatic painting).
The machine I have built is the mirror image of the one explained in that link, so I will give a brief, parallel English explanation.
One can see in the main pictures of this step, that there are 6 different zones on the discs. (and since everything is symmetric, those same 6 zones appear on the other side of the discs)
Even before the discs start spinning, there will be some static charge on the metal strips. Because just touching or handling the disks is enough to charge them a minuscule amount. This charge will amplify itself as the discs are spinning.
For example, the schematic starts in zone 1 with a net negative charge on the back disk strips. The field of this charge induces some polarization of the second disk. In much the same way as Fig. 2
As a front metal strip passes under the front brush of a neutralizer rod, some negative charge gets repelled trough the rod to a strip on the opposite of the disk.
This is similar to Fig. 2 where the “ground” is replaced by an other piece of conductor.
When the contact with the brush of the neutralizer rod is lost, a net positive charge remains on the strip. (If you subtract a negative charge, you’re left with a positive charge) Similar to Fig. 3
So, the back disc still has the net negative charge and the (upper) front disk strips now have a positive charge.
Secondly, the front disk strips on the other (bottom) side now have a net negative charge.
Remember that the back disk also turns, but in the opposite direction. In zone 4, the back disk gets in contact with the back neutralizer rod. And the negative charge on the back is produced in exactly the same way as in zone 2.
The positive charge repels the positive charge (or attracts negative charge since it’s mainly negative charges that move) on the other side of the disk.
Similarly, zone 5 is the opposite of zone 1 wherein the net positive charge on the front disk polarizes the back disk. As the back disc moves towards zone 4.
Here, the strips of the back disc and the front disc with the same charge pass under a comb-like structure.
As both strips on both disks have the same charge, they repel each other. Secondly the comb acts like a Faraday cage so the charges on the strips desperately want to escape outwards toward the comb. And this is what happens.
The comb does not need a physical contact with the strips as it has conducting points and electric fields towards points are always very strong, so there the air will break down a bit and the resulting ions provide a path for the charge on the strips to escape towards the low potential of the combs. When running a Wimhurst machine, this is visible with a small purple line from one of the points to the disks.
The charge on the combs immediately gets diverted towards Leyden jars where the charge/voltage will build up till there is a spark. (preferrably in a spark gap, or across the strips of the disk) Or, if there are much sharp edges, it will go away in coronas or ionic winds.
Wikipedia has an interesting animated gif that shows everything said previously
in an animation, but it is a bit complicated to deduce how everything works from it and the compact explanation with it.
In theory, the metal strips are not really necessary and this should be possible with only some charge on the surfaces of the disk. A Wimshurst machine without metal strips on the disks is called a Bonetti Machine. But one needs a static electricity generator (for example an ordinary Wimshurst machine) just to start this generator.
Step 2: Materials and tools
This Wimshurst machine is completely made out of scrap and small pieces of everyday common materials. With only simple manual tools.
I just used the tools and materials lying around, and obviously they are not ideal. For example cardboard is a horrible choice of material for any project involving static electricity, but it’s the only one I can work with for the moment.
The materials used:
- Cardboard: More precisely paperboard, not the sort they make boxes out of.
Various thicknesses are used, 1.5 mm, 1.2 mm and 0.5 mm, those are the most common and I had some lying around. But other thicknesses will work equally well, as long you have a sturdy kind for important structures, and a thin, flimsy kind for curved surfaces.
- CDs: The metal coating comes of easily from fujifilm CDs, I had an other kind which was harder, but I forgot.
- Aluminium foil OR aluminium tape: for the metal strips on the disks
- Electrical wire: A strong kind for the combs and electrodes, and a thin, multi strand wire for general connections, making the combs and the bristles.
- Some transparency sheets: to make some Leyden jars and to use it as some insulation.
- 2 rubber bands: To make the driving axle turn the disks.
- 2 toothpicks (or wooden rods), for the disk axle and crank handle.
- A larger rod for the driving axle. (I used a metal one, but a wooden one is most likely better)
The tools used:
- For measuring and drawing:
- a ruler
- a compass
- a caliper for more precise measurements
- For cutting
- some X-acto knifes
- For drilling:
- I used a small archimedes drill to drill holes
- Some screwdrivers to enlarge the holes since I didn’t have larger drill bits
- Bending/cutting wires:
- Fine plier
- Wire cutter
- General purpose tape
- Electric tape (but take a kind that actually sticks unlike the one I used)
- Double sided tape (to stick to things that should remain removable)
- For gluing:
- Paper glue: for gluing cardboard.
- General purpose contact glue: For gluing other stuff.
Cyanoacrylate (the kind of glue that dries in seconds and bonds very strong): to glue the handle to the metal axle.
- For sanding
- Sand paper
- For soldering
- A soldering iron (I forgot the picture)
Step 3: Clearing CDs
The main components of a Wimshurst machine are the two disks.
The Wimshurst machines requires two disks, so two CDs are used.
One can just scratch of the metal layer on a cd with an abrasive sponge. Depending on the CD this takes some effort.
An easier way is to just scratch up the plastic coating on the metal layer and soak the cd’s in a small layer of Hydrochloric acid. Surprisingly, the metal doesn’t etch away but one can just rub it off very easily.
Step 4: Metal strips
On the discs there have to be small metal strips.
I have made two different types of discs. One pair with ordinary kitchen aluminium foil strips. And a second pair with aluminium tape. (Because I ruined the first pair and it wasn’t good anyway) Both methods work equally well, the only difference is that it is much more work with aluminium foil since it is so fragile and you have to use a good glue to attach them to the plastic disks.
The strips are glued in a circle around the center of the disk.
There are are some things to take in account.
The strips are conductive
This means that there is a theoretical upper bound for the maximum spark length. If the voltage on the Leyden jars gets too high (the spark gap too big), a spark can jump from the collecting combs, across the gaps between the conducting strips, towards a neutralizer rod, across some more strips towards the other collector comb. So the theoretical upper voltage is “a bit more than” the sum of the distances from the combs to the strips and all the gaps between the strips that are crossed. A bit more than the distance because arcs like to consist of one single piece, it requires some more voltage to consist out of different parts.
So you want lots of strips with as much distance between them as possible… BUT:
Charge will leak away
There will be “corona” at every sharp conducting point connected to the Leyden Jars. As mentioned before, the air around sharp points gets ionized easily. The most intense coronas can be visible in a very dark room as a tiny purple glow around sharp points. And since this Wimshurst machine is so tiny, pretty much everything is sharp. You can get rid of it a bit by putting small spheres at the ends and not bending wires in sharp bends. But still, the wire is thin and will emit by itself. That’s why more professional machines always use copper tubes and wires even though the current is negligible.
But the message is that charge leaks away (and tiny machines leak a lot), so the machine must provide a sufficient current to counteract that leakage. Therefore the strips must have a fairly large area.
So, you have to find some equilibrium between size and amount of strips.
Two templates were made, first one to position 18 strips around the disk and later a template for 16 strips was made for the aluminium foil strips to add some more space between the strips. Both templates are attached here in a .svg and a .png format.
To make the aluminium strips:
Some foil was carefully cut (with a sharp knife) into tiny rectangular pieces of 30 mm x 12 mm. But if I would redo it, I would take 20 mm x 10 mm!
Then all these rectangles were cut into a trapezoid shape so that one side remains 12 mm, but the other is now 7.5 mm.
And finally all the corners of the aluminium strips are rounded with scissors. Because as mentioned earlier, sharp points leak the charge away in the air.
To make the aluminium tape strips:
The aluminium tape is much sturdier than than the foil, so a small template was made and traced onto the tape and cut out with scissors. And this tape can be pasted directly onto the disks.
The clean (and transparent) CDs are attached to the templates with some tape and the strips are glued on one by one.
Step 5: Making the rubber band wheels
The CDs will be driven by rubber bands. These rubber bands will be guided by some wheels of which two are attached to a driving axle and two are attached to the freely rotating disks.
The disk wheels
The wheels attached to the CDs consist of 3 large disks ( Diameter ≃ 38 mm so that it fits in that small bumpy ring on a CD ) and a small disc (Diameter: just small, I didn’t measure, it doesn’t matter much. Look a the first picture.) The cardboard is about 1.2 mm thick for the large disks and 1.5 mm for the inner, small disk. (But the thicknesses are not important, as long as a rubber band fits in the wheel)
In each one, a hole is drilled in the center and enlarged so that a toothpick can be inserted without much friction. Everything is sanded around the hole so that no rests from drilling the holes stick out.
Then all disks are glued together in this way: 2 large ones, the small one, 1 large one.
Then, those wheels are glued onto the CDs with the double cardboard layer into the small ring on the CD.
On my second pair of CDs I have used double sided tape so that if I want to change the CDs by new ones, It doesn’t stick so much and one can just get the wheels of and stick them onto the new CDs. This is very hard if you glue the wheels onto them.
Two small pieces of “butter paper” or “Baking paper” then go in between the two CDs as to minimize the friction when they rotate in opposite directions.
The driving axle wheels
The wheels on the driving shaft are made similarly, but with only two large disks (Diameter ≃ 4.8 cm) and a smaller disk (Diameter ≃ 4.4 cm).
Between the driving wheels, spacers are added so that the thickness becomes roughly equal to the thickness of the two CDs. This spacer is a bit too large which is good as it will later on reduce some tension on the CDs.
As a driving shaft, I have used a small metal rod that was lying around, but I strongly suggest to use wood or something else because it was very hard to fix the wheels (and later the crank) onto the driving shaft with glue.
Step 6: Mounting the shafts
Now there are two sets of wheels of which two are glued onto a driving shaft and two are attached to the discs.
The infrastructure onto which the shafts and wheels are mounted are two pieces of cardboard. The shape of the cardboard piece is constructed by drawing two circles with a diameter of 5 cm with their centers 7 cm apart on cardboard of 1.5 mm thick. (Note that this shape is probably too broad, as I have noticed fine, thin arcs jumping from the combs to the cardboard. perhaps 3 cm wide circles would have been better. See the “Debugging” step on how I prevented those small arcs. )
Holes are drilled and enlarged into the centers of the circles so that the driving shaft and the disk shaft can be inserted and rotate freely. (Although it is not necessary for the Disc shaft since the disks themselves can rotate freely around the shaft)
For each side two small circular spacers (0.5 mm thick cardboard) are cut out and so are some circles cut out of baking paper to reduce the friction.
The shafts can then be mounted into those pieces of cardboard.
Nothing is glued in this step so everything can be unmounted again.
Then finally rubber bands can be added. On one side, a rubber band simply goes around both wheels. And on the other side, make the rubber band cross itself.
This will have the effect that when the driving shaft is turned, the two disks will rotate in the opposite direction.
Step 7: Making the socket
The most important part of the machinery is already complete, but it still requires some infrastructure to hold everything together. Some sort of slot in which the mechanism will be inserted.
This is done by simply cutting out 4 half circles of 12 cm (the same size of a CD, but this size doesn’t matter) in strong cardboard.
In all the 4 half circles, a hole is drilled and enlarged for the driving shaft. They must be large enough so that the driving shaft can rotate without friction.
On two of the half circles the pieces that hold the wheels is placed so that the axle wheel holes are aligned and the piece is perpendicular to the straight edge of the half circle. The edge of the support piece is traced out and cut out of the half circle.
One should be able to slide the support pieces into their half circles and it should be very tight. Sand down some edges or glue in some small pieces of cardboard if necessary.
The half pieces of cardboard with this shape cut out are glued onto the remaining two remaining complete half circles.
A small slit is cut from the top to the hole. This slit is where the driving axle will slide down when the mechanism is inserted into the slot.
The mechanism with the wheels and disks is assembled again, the two half circle things are pressed onto the long support pieces and the thickness is measured.
A piece of cardboard of 12 cm x this thickness is then cut out, this will be the base of the socket.
Some rectangular spaces are cut out (never mind the small pieces you see in the picture, I didn’t use those) , their dimensions are the with minus the thickness of the two half circle pieces.
The two half circle pieces are glued vertically onto the rectangular piece and the spacers are glued in between for support in such a way that they don’t obstruct the mechanism when it is inserted.
If everything is done correctly, one can slide the mechanism into the socket and everything should be secure and tight. So, no glue is used and everything can still be disassembled.
Step 8: The base
A ground base is cut out, this will be used to mount everything on.
The shape is based around half a circle with diameter 11.8 cm. On the straight side of the half a circle there is an extra rectangular area with the same dimensions as the bottom of the socket for the mechanism.
On the curved side, two circles with radius 6 cm with their centers on the crossing of the curve with a radial lines with a 45° angle with respect to the straight edge. These will be the locations for the Leyden jars.
This is a bit complicated to explain in words, so I will provide a schematic:
Step 9: The Leyden Jars
Leyden jars are nothing more than capacitors. But capacitors that can handle large voltages.
The best thing is to make them out of glass or some sturdy plastic. But nothing of an appropriate size available at the moment, so the Leyden jars were constructed out of some rolled up pieces of transparency sheet.
First the caps were made.
The caps consist of a small cardboard disk about 5 cm in diameter. And a small flexible strip of cardboard Diameter x pi long and 1.5 cm wide so can encircle the disk tightly. Two smaller pieces of cardboard are used to keep the strip closed and tight around the disk. Everything is glued together and one can see the result in the second picture.
This is done 4 times and two caps that will be used as the tops have a hole trough which an electric wire will run.
An A4 format transparency sheet is cut lengthwise into 3 equal pieces of about 7 cm. Two are joined with some tape to form one long strip. When rolled up, it will have more than one layer which increases the voltage it can handle.
Just before rolling up, a strip of aluminium foil 5 cm wide is attached with some tape. So that when everything is rolled up, there is an aluminium layer on the inside.
When rolled up, it is inserted into two caps and released to let it adjust to the size of the caps. It is made sure that the caps are still a bit too large as there are still some layers to be added.
The rolls and the aluminium foil are secured with some tape.
On the outside, a second strip of aluminium foil (again 5 cm) is added and secured. On the inside and the outside a small electric wire is taped on the bare aluminium.
The third and final layer of transparency sheet is now rolled around everything, covering up the outside aluminium foil. So that if one touches it, one won’t get a shock.
The completed roll should now fit tightly in the caps. And the inner wire should go trough the hole of the top cap.
The Leyden jars have the second purpose of being the support structure for the collector combs.
Four circles with a Diameter of 4 cm are drawn out on a piece of cardboard and a straight line is drawn 2.5 cm from the center of each circle. These semi-circle semi-rectangle shape are cut out and holes are drilled in the centers of the circles. In two of the four shapes, an extra hole is drilled in the neighborhood of the first hole.
Some thick, strong copper wire is used for the comb structure. It is hard to explain the shape in text and I refer to the pictures for the shape. (although they are not optimal)
The Leyden jars are positioned on the small circles of the ground base, a copper wire is bent in such a fashion that it goes trough the two red wire holders on the top of the jars towards the disks and bends around the two disks at some distance. Try to avoid the inward bend I made.
Some finer wire are soldered onto the comb structures making an effective comb. The small comb wires should NOT touch the rotating disks.
Step 10: The Neutralizer rods
As mentioned in the explanation of the workings, there still have to be some neutralizer rods.
For this, a piece of cardboard consisting of 12 cm long and ~1.5 cm wide strip with a 2 cm wide circle in the center.
This will be the support for the “rods”. Those rods are nothing more than a piece of stranded electric wire with the ends stripped and spread out like a bristle.
This wire is glued onto the cardboard pieces and the ends are bent inwards. Probably it is best to glue them on the other side than is seen in the third picture. To be more flexible in adjusting the distance between the neutralizer rods and the combs.
The rods should be fastened to the support pieces. I have attached them in a 45° angle with the collector combs (which are horizontal) But an angle of 60° is likely better as this increases the distance between the brushes and the combs which makes arcing over the aluminium strips less likely.
The neutralizer rods are fastened by making tiny hooks out of cardboard. A tiny piece of cardboard with a larger piece on top under which the cardboard piece can be hooked (or unhooked if wanted).
Step 11: The crank
To actually work, one needs a way to rotate the driving axle.
The simplest way is to use a simple crank.
The crank is made of cardboard and a toothpick.
The crank consists out of two main parts being an “arm” and a freely rotating “handle”.
The arm consists of a shape defined by two circles, one with a diameter of 2 cm and one with a diameter of 1.2 cm with their centers separated by 2.5 cm. Trough both centers a hole is drilled, trough the large circle a hole that tightly fits around the driving axle and trough the small circle a hole that loosely fits around a toothpick.
Something like this:
3 extra (2 cm) large and 2 extra (1.2 cm) small disks are cut out. And again in the same way as before holes are drilled in their centers. The large disks are glued on the location of the large circle of the handle, two on the side that will face the machine and one on the other side. The small disks are glued on the location of the small circle, one on each side.
For the handle
Eight small disks with a diameter of 1.2 cm are cut out and a hole is drilled in their center. Seven of them are placed and glued firmly on a toothpick in such a way that they form a cylinder. The toothpick is trimmed on one side and the other side goes trough the hole on the small circle side of the arm. The last disk is glued on the end of the toothpick that went trough the arm. It is glued in such a way that it is firmly attached to the toothpick, but not glued on the arm so that the handle can rotate freely.
This is a schematic of the assembled arm. Notice that the handle is in no way glued to the arm as it must rotate freely.
Green = handle, Blue = arm, Red = glue , Orange = toothpick, Grey = driving shaft.
The crank can be pushed onto the driving shaft and glued with a very strong glue. I have added an extra spacer but it got glued to the crank.
There must be some distance between the crank and the mechanism so that the mechanism can still slide into the socket without the crank obstructing anything.
Step 12: Closing the socket
Until now, the socket which holds the mechanism has always been open on the curved side.
In this step, these sides are covered. This is a small step which would fit more in the step wherein the socket was actually built, but I try to follow the chronological events of the build. It is convenient to cover the socket up as late as possible since it is only of aesthetic value but prevents further tinkering on the inside of the socket. (For example to make the socket more tight or looser)
The mechanism is placed into the socket and the sides are measured up to the slit in the middle. It is noted where the discs enter the socket.
The resulting shape is drawn on a thin piece of cardboard and is cut out precisely. And it is made sure that the discs have no hindrance of the covers when they turn.
The piece of cardboard is curved around a cylindrical object and the result can be seen in the first picture.
The second picture shows the socket when the coverings are in place.
Step 13: Preventing the jars and mechanism to shift
Although already fully functional, the Leyden jars and the mechanism in its socket are still separate and loose. Turning the crank causes everything to wobble and the fragile strips on the disc to get damaged by hitting the comb.
It is better for the Leyden jars and the socket to be non-permanently fixed to the base so they cannot shift their position.
For the Leyden jars:
For each Leyden jar, a circle of the same diameter of the Leyden jars is cut out. In each circle a shape is cut out that is not rotationally symmetric (so, basically any shape but a circle, a square/rectangle is the most easy one).
The squares are glued to the base so that their circle fit around them in the place where the Leyden jars are supposed to be.
The circles are glued onto the Leyden jars, so that they can be placed upon the squares where they are fixed in their location and can not turn or shift.
For the socket:
The exact same thing happens for the socket, but instead of a circle, a rectangle with the same dimensions as the underside of the socket is used. Out of this rectangle, a smaller rectangle is cut. This in such a way that when the Leyden jars are fixed in their position, the discs do not touch the combs.
Concerning the last picture
I have cut two strips of thin cardboard to glue on the bottom edge of the socket. I don’t know anymore why I did that because they serve absolutely no purpose.
Step 14: The electrodes
Since the electrodes are so simple,
They are just two long pieces of stiff copper wire with 2 u bends that are squeezed with pliers around the copper wire on top of the Leyden Jars.
Spherical balls are made from crumbled aluminium foil (mainly because I don’t have metal spheres laying around and I couldn’t find any in the DIY store in the neighborhood)
These balls are made as spherical as possible and pushed upon the electrodes.
For some reason, I don’t fully understand why, the sparks are a bit larger with one large ball on one electrode and a smaller ball on the other.
Step 15: Debugging
Since this is a very small Wimshurst machine and cardboard is absolutely NOT an ideal material for static electricity stuff, many things can and will go wrong.
First of all the mechanism. If nothing works, just turn the crank in the other way. I have it in the configuration that the front rubber band is crossed and the back (on the same side of the crank) is not crossed. And turning the crank in the opposite direction of the clock works, but nothing happens when I turn it in the opposite direction. (which is actually logical if you take in mind how this device works)
For the rest, it is a matter of isolating everything and reducing corona.
The ideal way to find leaks is to turn your machine (with the electrodes away from each other (with their balls mounted)) in a very dark room. Let your eyes adapt, and you will see glowing things and arcs and whisps, coronas,…
In essence there are only 6 allowed glowing places. The 4 neutralizer rod brushes, and the 2 collector combs (on both sides, so technically 8 places) these will be the brightest, but after a few minutes in the dark, you will see lots of things.
All the rest should be reduced as much as possible by isolation.
In the pictures, you can see some images, taken with a long exposure of about 15 seconds and one can see some corona on the brushes, but the other coronas are so faint that they are barely visible.
If the voltage gets too high, arcs will jump across the strips. If this happens too soon, one might conside rearranging the aluminium strips ont he disks.
As said before, every sharp point, bend or corener will have some corona which leaks charge away from the Leyden jars. This will reduce your ability to reach high voltages for large sparks.
For example, I had the combs too close to the cardboard support structure and in the dark, a very small, thin, purple glow emanated from the combs to the cardboard. I bent away the comb ends a bit which reduced this to some extent.
Secondly, extremely faint glowing tongues jump out from the metal strips on the disks towards the cardboard. These things are only visible in a very dark room with your eyes adjusted.
The solution to this is to cover all cardboard and non-essential conductors in electrical tape. And in the case of the aluminium strips, I added a very large circular transparency sheet spacer (Diameter 5.5 cm) next to the cardboard on the disk axle.
Arcing over the strips.
This can be seen in the pictures as the bright lights between the strips.
This is just a limit of the strips, this problem can be decreased by reducing the number and size of strips on the discs. For example, I went from 18 aluminium foil strips to 16 thinner aluminium tape strips. Now I don’t have arcing over the strips anymore. The maximum size of arcs on the electrodes is larger.
The leyden jars.
At one time, the wire connecting the two Leyden jars was touching one of the Leyden jars. And a small glow was visible on that location on the piece of transparency sheet. (indicating that transparency sheets are not ideal conductors too.)
So, I have 3-4 layers of rolled transparency sheet between the two aluminium layers in the Leyden jars. But the previous note indicates that this transparency sheet is maybe too thin and is slightly conductive. Therefore it is probably better to use glass or a thicker plastic layer.
The Neutralizer rod
And finally, the cardboard neutralizer rod in the vicinity of a Leyden jar started emanating a purple glow on a corner. This was eliminated by covering the neutralizer rods with electrical tape.
Step 16: Results
The Wimshurst machine is finished.
The pictures show the final machine fro different angles. (The electrical tape wasn’t really sticky and began to loosen again)
Secondly, some pictures of sparks are included.
The sparks in the pictures are about 1.2 – 1.3 mm large.
But much larger of nearly 2 cm are no big problem. Capturing them on video however was a larger problem as I had to sit in an uncomfortable position and was not able to turn the crank fast and long enough . Secondly, due to the extremely short duration of the spark, one has to have some luck to have them in frame.
As this is a very small wimshurst machine, one has to turn the crank long and fast to be able to fill the Leyden jars.
So, sparks from 1-1.5 cm are absolutely no problem. When the weather is dry, sparks up to 2 – 2.5cm are within range with some effort.
Because you probably want an animation, I have uploaded an a part of the video footage to an animated gif in the last picture.
It does takes some time to load.
I have uploaded a video too so you can hear the sound (although you won’t be impressed with the sound quality).
An other interesting thing about this small cardboard Wimshurst machine, is that it is easy to almost completely disassemble it to replace a single part and reassemble it again. I have made an animation of it in the one but last animation since I didn’t really know what to do with the pictures.
So, yeah, that was it, I hope you liked it.
I’ll be glad to answer questions. And thank you if you point out mistakes in my continental Euro English.