Re: Giant Wimshurst Machine - could use some guidance
Sulaiman, Sat May 10 2014, 01:00PM

For elegance of construction I suggest 'doorknob' ceramic capacitors, e.g.
however, you should consider lower capacitance / stored energy,

If you used these capacitors to make two towers of 25 series capacitors each
the stored energy would be > 30 Joules ... a fairly impressive bang

Re: Giant Wimshurst Machine - could use some guidance
Wastrel, Sat May 10 2014, 01:40PM

A Leyden jar is just a glass container coated on the inside (and for lower voltages, optionally on the outside) with metal. Your machines capacitance needs to be tiny. Hopefully someone can chime in with actual values for what spark energy is safe without ear defenders. Lose the MMC idea.

I don't know if a 4 ft device will reach the voltages you expect, school models tend to be unimpressive next to van der graaf machines, 75kv versus 250kv. Voltage may scale linearly but lots of problems, capacitance, forces will scale squared. A million volt wheel pushing 100ua might be quite difficult to turn.

With sharpish ends you shouldn't need a million volts but don't rule out an enclosed gap at lower pressure to get the effect at much lower voltage. A sign that says "If using this machine without the enclosed spark gap, ear defenders MUST be worn." might be helpful even if the spark is unimpressive in room air. There is a degree of showmanship to these things.

Build some smaller versions first to get an idea what materials work. Whimshurst machines are temperamental and can fail to work at all if the air is slightly too humid or the moon is in the wrong place...

Re: Giant Wimshurst Machine - could use some guidance
Dr. Slack, Sat May 10 2014, 02:06PM

I've seen really big Wimshurst machines simply use a large sphere on each electrode as the capacitance to ground (annoyingly can't see anything like it in the first few pages of 'google images wimshurst'). At >1MV, only a few pFs is needed to make a healthy bang. Air has a lot to recommend it as a dielectric. Google for sphere to ground capacitance formulae.

Re: Giant Wimshurst Machine - could use some guidance
Antonio, Sat May 10 2014, 03:36PM

For 18" sparks in a Wimshurst machine you need disks with three or four times this in diameter, maybe a bit less with good insulation and small sectors. Assuming that sparks between sphere terminals only occur with length up to 4 times the diameter of the spheres (see my avatar image), 18" sparks would require 4.5" spheres. The breakdown voltage between two 4.5" spheres separated by 18" can be calculated as 298 kV at sea level. A spark gap with the positive ball smaller can produce this same spark length with less voltage, 151 kV with one 2.25" sphere.
It´s better to use double balls, as frequently seen in these machines. So, the required voltage is not so high. Leyden jar capacitors can be safely used, and are very easy to make from plastic containers. For greater insulation two can be connected in series at each terminal. The jars can have less than 100 pF of capacitance.

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Sat May 10 2014, 09:29PM

Thanks for everyone's feedback so far.

Bear with me here, I have a rough understanding of most of these things, but not solid enough to make decisions based on them.


What I keep hearing is that you can get a spark gap 1/3 the size of the wheels. So, 18" gap = 54" wheels (4 and a half feet).

Sadly, the goal isn't simply "high voltage sparks", they for whatever reason chose a Wimshurst. They do like the contraptiony feel of the spinning wheels, it's flashy and gives the visitors something to do between sparks (sparks can't be generated all the time, too distracting from other exhibits).


Interesting. I knew there were going to be non-linear issues, I just wasn't sure what they were. Could you elaborate?

Well, obviously one would be that the diameter of the wheel is 4x 1 foot, but the area of the wheels is now 16x the 1 foot model. But I'm more concerned about the electrical considerations.

In terms of force, I can gear the machine however I want. If they want sparks every 5-15 seconds, I have to figure what kind of average effort is being put into the machine, and size the capacitors appropriately. If it's too hard to turn, I'd need less capacitance.


Well it'll be in a hall I presume, so, ear protection isn't something they could expect visitors to wear. I'll have to consider that as an issue. I've not heard how loud discharges get.


They've already been playing with a tabletop 12" machine. And yeah, you're not the first to suggest they're twitchy buggers.


Can you explain the context of "ground" in this sense?

Obviously it's not a mains powered device so there's no safety issues with ground in that respect.
Obviously the machine will have one side or the other that I'll refer to as "ground" for the sake of grounding things, enclosure if any, whatnot.

... is there another issue with the actual ground (as in, floor/dirt)? I'm peripherally aware of capacitive losses and such, but not really in a tangible "how does this effect design" kind of way.



I'm a bit lost. I thought breakdown voltage of air was about 75kv/inch. How would you get 151kV to jump 18"?

I understand air plasma has about 2% the resistance of air gas, but, that requires it to be arced already.

When you say "spheres" is that hollow spheres acting as capacitors? Designs I've seen so far just use solid brass spheres much smaller.

It's also been suggested to me that sharp needles, rather than smooth spheres, would greatly reduce the voltage needed to initiate a spark because corona is already going to tend to leach in that direction.


The issue with Leyden jars, that I've worried about, is maintenance and gradual degradation/catastrophic runaway once perforations start appearing. If it was for me, I'd say no problem, I know the symptoms and I'll just repair it now and then if it needs it. But this is an exhibit. It has a large budget to build it well the first time, after which I think it's expected to work reliably for a long period of time without hiring contractors to repair it.

I am not set in stone on any of this, I"m just going by my best understanding of the material so far, so by all means feel free to criticize and educate me. I'm not here to show off or brag.

Re: Giant Wimshurst Machine - could use some guidance
Antonio, Sat May 10 2014, 11:24PM

The figure of 75 kV/inch is for breakdown between parallel surfaces. Between spheres the breakdown voltage depends on the geometry.

The spheres are the spark gap spheres. The longest capacitor-discharge spark possible between spheres is about 4 times the diameter of the spheres, and about two times this if one of the spheres is much larger than the other and the smaller is positive.
Points don't produce long sparks because they leak the charge generated by the machine at low voltage and the capacitors are not charged. You get just corona. The same if the terminal balls are too small.
Leyden jars fail completely at the first perforation and have to be replaced. But they last forever if sufficiently thick from the start.
You can use large metal balls as capacitors, as in this machine with 2.15 m disks:

Note the large terminals.
Expect frequent maintenance necessary. These machines accumulate dust fast and have to be cleaned at every few days of use. Enclosing everything in a sealed box kept clean and dry inside may help. Think carefully about a solid construction, since it's a big machine and its weight and the force necessary to turn it are not low.

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Sun May 11 2014, 12:14AM


I thought I was doing okay, and then I saw all those formulas and not a lot of examples or context for them. My brain fuzzes over on that, so, that'll take me a few days to work through.

Interesting though, had no idea there was a difference between parallel surfaces and spheres. That completely changes the numbers, I'm glad you mentioned it.


I don't understand that 4x diameter stuff. Electricity will jump between the shortest points, it's not going to hold up to infinite voltage just because the spheres aren't large enough, no?

Also, correct me if I'm wrong, but I don't think there's a way of determining which way the Wimshurst charges. Polarity will be a cointoss, so, I won't be able to cheat with a small ball sadly.


Not sure I want to go with that route, but, good to know there's another option.


For safety's sake I'm starting to lean towards pressuring them to putting it in a clear enclosure. Keeps moisture out too.


Yeah, I'm looking at probably half inch drive shafts, standard pulleys, that kind of thing. I'm not as worried about that.

Thanks for the advice so far, it's been very helpful.

Re: Giant Wimshurst Machine - could use some guidance
Eleccentric, Sun May 11 2014, 12:18AM


That is my understanding as well, though this applies only to well-designed machines. I built four of them before I finally had a design that met my ambitious expectations. With sectored disks is manages about 1/3 the diameter, and with sectorless discs I get about 2/3 the diameter. However, forgoing sectors means that it is not self-starting, and makes it almost impossible to start in humid weather, so it wouldn't be a good idea on a museum installation. You'd need some sort of retractable charge spraying brush and the whole thing would have to be kept in a climate-controlled case.


Reducing capacitance isn't going to be too difficult with Leyden jars, depending on how you construct them. Perhaps you could put them in place without attaching the "nice" outer metal electrode first, just wrap it in cheap aluminum foil for testing and remove it in strips until you get a good value of spark rate vs difficulty of cranking. Then you can install the correct amount of beautiful copper or brass shim stock. The inner electrode doesn't have to be adjusted, and it will only add significant capacitance in areas covered by the outer electrode.


An 18" discharge isn't necessarily deafening, but the more capacitance behind that spark, the louder it will be. The goal should be to use the least amount needed to achieve your desired spark.



As a general rule of good practice, do two things: Avoid hygroscopic materials for your insulators, and avoid small radii on all conductors. This means absolutely no sharp points or bends in your HV conductors (except your collection combs), and though this is less critical for the neutralizers, you don't want sharp points on anything anywhere near your lovely gently curving mirror-smooth conductors.


Ground in this sense is going to be halfway in potential between the two sides. If you want to attach it to earth ground, do so to the outer foil of both Leyden jars. This will equalize the voltage on each side of the machine, reducing corona and ion wind discharges to surrounding objects. There should be very little current moving into or out of the earth ground, so it doesn't have to be low-resistance like one used for a large Tesla coil. I don't use an earth ground on my Wimshurst machines, but I do attach the outer foil of each Leyden jar to one another.

Listen to Antonio over anything I say. A lot of what I know about electrostatic machines came from studying his website. His mentioning of dust collection is very important, and perhaps is another argument in favor of an enclosed display. Also, avoid using rubber belts, or anything that will be degraded by ozone or nitric oxides.




The shape of a conductor directly influences the gradient of the electric field around it. The larger the gradient, the more likely that space will break down into a spark or corona. Sharp bends or points create sharp gradients. Theoretically, two perfect spheres of infinite size in a perfect vacuum could hold off infinite voltage. Also, the type of charge, positive or negative, affects the likelihood of charge leaping off the conductor. Hence asymmetric balls to take advantage of this asymmetry.



Consider using chain drives or enclosed gear drives, as most belt materials will break down into a fine dust that will stick to everything, especially in the presence of electrical discharges. Ozone, UV, various nitric oxides and the numerous exotic high oxidation number creations of plasma will be produced by the machine, IIRC.

Re: Giant Wimshurst Machine - could use some guidance
Antonio, Sun May 11 2014, 02:14AM

The problem is that the spark is a capacitor discharge. The capacitors are charged slowly by the very low current that these machines produce, and the terminals must hold the charge until sufficient voltage for breakdown is reached and enough charge is stored to feed a spark. Small terminals or points leak at low voltage and do not form sparks. In systems that charge the terminals fast or with with high current, as Marx generators and Tesla coils, even points produce long sparks. But a Wimshurst machine produces just hundreds of uA at most and charges the terminals slowly.
The polarity of the machine is really random, unless some form of precharge is used. Terminals with two balls allow adjustment of the terminals so the positive terminal inclinated in the direction of the negative works as an asymmetrical gap.

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Sun May 11 2014, 06:05AM


Yeah, it's just a function of surface area so, increase or decrease that and I'm set. I'm building a prototype to tinker with, so, lots of tinker time.

Was actually considering using aluminum duct foil (not duct tape, the better stuff). Which reminds me, I was also thinking of using that on the wheels for the metal sectors. Any reason not to? Alum creates that continuous black AlumOx ruboff. Any reason aluminum is usually used? Any reason not to use a more aesthetically pleasing copper or brass or phosphor bronze, or a more durable stainless steel?

And speaking of materials.. not set on wheel material either. Plexi, acrylic (fragile), polycarb, glass (heavy and maybe dangerously fragile at the speeds it'll be moving, shrapnel hazard). Any suggestions?


Heh. Until recently I was thinking the opposite. Spend as much of the budget here as possible, since it will create the hottest and brightest and most intense sparks. When weighing time/effort of cranking the wheel hard enough, I was tentatively pessimistic about that. When weighing safety I backpedaled, and now weighing noise I'm in full retreat to in line with your comments.


I've been trying to figure out how much of skin effect occurs for this kind of thing. If it's 1/5 to 1/15 hz, there's no RF in the conventional sense, but, the sudden discharge and, the whole deal with it being static has me uncertain.

For conductors I was considering copper or brass pipe for aesthetics, but also simply welding cable (can buy it in thick segments and is easy to bend). I was also considering making a twisted cable out of many strands of enameled wire (basically emulating Litz wire). Is there any point in that? Any ballpark size for my conductors? I was figuring half inch just to be safe.


They asked me about a safety ground and, I was mostly sure it didn't need one really, because it's not mains powered, but I thought there might be some other reason to do it.

Do I have to worry about visitors touching a single conductor, or just getting caught between both conductors? With static charges, it seems that, relative to the visitor, either side is still at a massive charge difference and will discharge to or from either end.


Well, another hobby is making things from junk bicycle parts, so, I'm all aboard with that. It's actually what the original plan was, for the wrong reasons, then moved into belts, and now probably back full circle. Oh well, right things for the right reasons.



Ahh, so stacking the small balls on top of the large let it discharge whichever way allows spark quickest? Or, are you saying they have to be adjusted every single time the wheel is cranked?

Would it be possible to cheat and just hook a low voltage power supply up to the caps (or a DC generator also driven by the machine, or... something) to ensure one terminal to always be positive and the other negative? I don't care if the contraption is built on a cavern of lies, if it helps the overall result.

Thanks again for the feedback, I'm learning tons. You guys are great.

Re: Giant Wimshurst Machine - could use some guidance
Proud Mary, Sun May 11 2014, 10:56AM

This here paper may help you out. It has both Wimshurst theory and plenty of practice and practical that goes as far as engineering drawings, optimizing disk speed and size, choice of materials for conductors and insulators, single and multiple disk machines, comparison with belt-type electrostatic machines - in a word, the whole nine yards:

Cosman, B.J., Disk Type Electrostatic Generators MIT MSc Thesis, May 1937

Re: Giant Wimshurst Machine - could use some guidance
Dr. Slack, Sun May 11 2014, 11:15AM

Antonio, that's the machine I had in mind. Note the big balls added to the conductors behind the machine.

I feel I don't know enough about Wimshurst machines to understand why the cross conductors on that one are not at 45 degrees, like they are on almost every other machine I've seen.

As the machine produces a balanced bipolar output, 'ground' is neither terminal. If you look up formulae for capacitance a 'sphere' has ground at infinity, the integral does converge and you do get a finite capacitance. The formulae for two concentric spheres has some 1/R terms on the bottom, and what happens is once the enclosing sphere gets much bigger than the internal sphere, it is the diameter of the inner that dominates the value.

The formula you need is the concentric spheres one, with the inner sphere being whatever you add to the conductors, and the outer 'ground' sphere being a crude average of the radius of the enclosing room, and a theoretical 'zero voltage' virtual ground plane between the positive and negative spheres. It would be impractical to compute an analytical value for the outer radius, but it's bounded above by half the room diameter, and below by half the distance between the added spheres, and doesn't affect the value much, so you don't need to be too careful. You might worry that the room isn't really a ground conductor, but it has wires and pipes in the walls, and building materials of normal moisture content are perfect conductors compared to megavolts and microamps of the Wimshurst.

There are two problems to this project
a) getting it working
b) still having it working in a year's time, or ten year's time

I'm sure you'll manage the first, a bit of advice, enthusiasm, care, no trouble.

Still having it working in a year, when dust has settled, people have put greasy finger-prints on it, both of which attract surface moisture, and all the charge is leaking across the insulators before it can jump across the gap, will be your biggest issue.

You might want to consider exactly how the machine is physically built, so that it's either
a) very easy to keep clean or
b) very easy to dismantle and reassemble for a thorough clean from time to time.

Will there be anybody in the Science Centre to 'love' it, give it care and cleaning, when you're not around?

Re: Giant Wimshurst Machine - could use some guidance
Antonio, Sun May 11 2014, 01:00PM

This work is very interresting, but it deals with a version of a Van de Graaf generator using a disk instead of a belt. The charging system is electronic. Some of the theory and construction details are valid for a Wimshurst machine too, of course.

The terminals have to be adjusted depending on the polarity. They have to be adjustable anyway, because the machine will not reach the same maximum spark length every time, depending on humidity, pressure, temperature, cleanliness, etc.
Precharge can be done by spraying charge from a HV power supply through a point opposite to one of the neutralizers. It's more practical to adjust the terminals.


The angle of the neutralizers controls the maximum voltage, high angle increasing it, up to a point where the machine ceases to work because the charge increasing mechanism stops. In a large machine the neutralizers can be almost vertical.
The capacitance of an ideal sphere far from other bodies is ~55 pF per meter of diameter. It's directly proportional to the diameter (an not to the surface area, as it may look).

Re: Giant Wimshurst Machine - could use some guidance
Proud Mary, Sun May 11 2014, 02:29PM

Interesting to see that a patent for an improved Wimshurt machine has been granted in this century, in 2002, in fact:

Re: Giant Wimshurst Machine - could use some guidance
Antonio, Sun May 11 2014, 06:30PM

I have seen this patent before. Apparently a Wimshurst machine with several pairs of neutralizer bars instead of just two. Would rise the output voltage faster, but would produce less voltage due to the decreased insulation and at most the same current of a conventional machine, as it's not possible to increase the maximum charge density in the disks.
The proposed structure seems very strange, with a partition between the disks and the sectors mounted on the sides of the disks that face each other.


Aluminum foil or adhesive tape for the sectors is easy to find and easily replaceable. Aluminum oxide does not appear to be a problem. Copper, bronze and brass are good too, but tarnish easily. Stainless steel would be ideal, but is more difficult to find in thin foil. May be more difficult to glue precisely too.
For disks, I have used only acrylic. Policarbonate probably works too, or any other rigid plastic. Glass is heavy, difficult to cut and drill, breaks easily, and may be too hygroscopic, and so conductive (use Pyrex glass).

Re: Giant Wimshurst Machine - could use some guidance
Eleccentric, Sun May 11 2014, 08:15PM


Aluminum is cheap and easy to cut. So long as your neutralizer brushes are soft enough the oxide rub off shouldn't be a problem. I use carbon fiber brushes from printers, normally used to remove charge from the paper - they are exceedingly soft and springy, and plenty conductive at these voltages. Other than being more prone to tarnish and corrosion, copper or brass will work fine as well. Stainless will be more difficult to work, but it perhaps the most durable choice of easily available sector materials.

More important than the metal the sectors are made from is the corona loss from the edges of the sectors. They have a sharp edge all around. I have seen designs that laminate the sectors between two thin discs, and then only make contact on the edge of the disc or through a small raised bump that protrudes through the outer laminate surface.


I have used vinyl, bakelite, acrylic, and HDPE. All could be made to work, but the best results by far were with HDPE. According to R.A. Ford's book "Homemade Lightning" the most ideal material would be G-10 fiberglass laminate, which is very similar to material used for making printed circuit boards. HDPE is somewhat hygroscopic, but G-10 is minimally so. Of course, these suggestions won't work if you want to stick to transparent discs.



The skin effect does not apply in this case. Litz would be a waste of time and money and likely be a source of leakage. The rapid discharge will create some RF, but not until the spark has already appeared. Large diameter metal pipe will work very well, with gently curved bends and any joints buried inside spheres, ideally with involute edges - like the way the underside of a Van de Graaff generator's terminal curves inward around the insulating pipe/pedestal/belt support.

If you want to use cable, go for high-voltage rated silicone insulated wire, not welding cable. It is easily available at voltage ratings of 100kV, and I imagine that some searching could find it at even higher ratings. You could also sleeve it in appropriately sized silicone tubing to add more voltage strength.

On my best-performing machine I use 1" diameter copper pipe. The larger, the better. But, the smoothness of the joints is more critical. A tiny fleck of metal shaving on the terminal of an otherwise perfect Van de Graaff can completely spoil the output, as it bleeds off the charge.


YES. While the output of this machine will almost certainly not be lethal to a healthy person (in my nonprofessional opinion), it would definitely be very painful experience for anyone, and could be disastrous for someone prone to seizures, with a pacemaker or implanted defibrillator, or otherwise with some sort of neurocardiogenic vulnerability.

Re: Giant Wimshurst Machine - could use some guidance
Proud Mary, Mon May 12 2014, 02:05PM

I was interested to see in the Disk Type Electrostatic Generators paper I posted above, the authors' use of conductors made of wood sprayed with zinc paint.

I don't recall seeing zinc spray cans on sale, but there is certainly conductive nickel metal spray available for instant screening and shielding.

As we are only talking μA with these electrostatic machines, this antique method could still be very useful to the home constructor like myself who has a small wood lathe, but not one for working with metal.

Re: Giant Wimshurst Machine - could use some guidance
Antonio, Mon May 12 2014, 11:18PM

Zinc paint exists too Wood is a so bad insulator that in some applications can be safely used as conductor without treatment. Wood can be dried in an oven and boiled in insulating resin, or just paraffin, becoming a reasonable insulator. Alessandro Volta made an electrostatic machine entirely in wood (but didn't leave good documentation of it).

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Tue May 13 2014, 12:51AM


I gave it a read. Hard to tell sometimes what they're talking about in particular, but it was low level enough that I made some sense of it. I liked how it was written a bit as a trial-and-error thing, so you got to see why things were the way they were.


Well I won't be "around" ever really, but, yes, there is a staff, presumably maintenance staff too. I'll be sure to have a chat with them about regular maintenance and how that affects the design now.


Initially what they were looking for was a perfect, calculated design they could send off to a fabricating lab. One that would engineered perfectly with the proper numbers from the proper formulas and then just built.

I talked them out of that immediately. That's just not how these things work. Almost everything needs to be adjustable, tweakable, etc. It's not like this is ballistics or chemistry where you just know and calculate everything ahead of time. The machines are finicky and the science is fudged. Any numbers used would be approximations and a lot of the constants aren't constant.

I also pointed out that interacting with the machine and seeing how changes influence it would be interesting to visitors, but I don't know if I was as convincing in that.

I suggested if they are worried about it, to just set the spark gap to some unambitiously close worst-case amount such that it always fires. I.E. Design for 24", set it to 18". Or, make it variable.


Fascinating. Another one of those things I not only didn't know the answer to, I didn't even know it was a question to be asked.


Well I'm sure if I shop around I can find whatever I need. Even if it's just stainless foil that I have to superglue myself.


Glass scares me. High edge speed, sudden catastrophic failure, etc. No thanks. Luckily they agreed.

I have a dumb question about the term "Dielectric". Is it synonymous with "electrical insulator"?

I see them used somewhat interchangeably, but not entirely. In some contexts it seems as if you want to avoid using a material with a high dielectric value but a low insulative value. In other places it appears as if when you have one, you have the other.


I had a copier tech and fellow HV enthusiast suggest the same thing to me. I'm very much leaning that way now, as I have a bottomless supply of copying machines.


Hrm, you lost me.

By edge you mean, if the sectors were paper, it would be the edge that gives you the papercut, yes?

That is because, being foil, and thin, they are a sharp (narrow anyway) edge?

If so, I'm good until the lamination part, then I can't picture it.


Ahh, I'm familiar with G-10, it's used by knifemakers when building prototypes.

I'm fairly sure, but not positive, that transparent discs are highly desired, if not an absolute need. It functions largely as a display piece.


I didn't think so, but, I know there's contexts that I'm missing, so sometimes I get suspicious and ask about things I don't think matter.


Do you (or would it be beneficial to) fill the pipe with any additional conductor (wire), or is the resistance of the pipe low enough to not be a concern?

I can easily source some large copper pipe, probably as large as required. 1-2" seems reasonable.

What is your method for bending the pipe smoothly? I was going to pack with sand and wrap around an appropriate mandrel. I've tried the water-->ice fill method and for short lengths it's basically no better than empty. I could borrow some conduit benders but they have such strict radii.

...

One additional question that's come to mind...

The spacing between wheels. Across the sides of the wheels is the full voltage potential. It doesn't appear that machines are built with the wheels a sparkgap's distance between them, but, how then do they not short? Do I need a larger insulator on the wheel?

Related, I also read that the farther apart the discs, (and the thicker their material?), the lower their power generating capacity. So, seems that you want to put them as close together as possible without becoming a hazard.

Oh, and one more... attaching the wheels to an axle. Are there issues with bearings and the shaft being conductive, or is the middle of the wheel, by geometry, sufficiently far away from the HV to not mess with it?

Thank you everyone again for being so patient.

Re: Giant Wimshurst Machine - could use some guidance
Dr. Slack, Tue May 13 2014, 08:43AM

Insulator or dielectric?

They mean more or less the same thing, Things like mica, plastic, glass, oil, SiO2 could all be described as either. The difference comes when you use them in an application.

Where you are just interested in the bulk resistivity, and possibly the mechanical properties, perhaps for protercting wires, or mounting terminals, then you call it an insulator.

Where the dielectric constant matters, both real part (capacitance) and imaginary part (losses), you tend to be using it in a capacitor, or between lines in a fast processor chip, and call it a dielctric.

So a sheet of FR4 GRP board. If you mount mains terminals on it, you'd probably call it an insulator. If you ran a 50 ohm track across it, you'd call it a dielectric.

Re: Giant Wimshurst Machine - could use some guidance
Antonio, Wed May 14 2014, 12:10AM

The full voltage appears between the two sides of the machine, identical in both disks. They are oppositely charged just in the top and bottom, at the space between the neutralizers, but there the voltage is low. The machine can spark across the center if the sectors are too close to the center, or across the sectors (and the neutralizers) if they are too close.
The distance between the disks controls the rate of the charge buildup. At some distance the charge multiplication factor falls below one and the machine doesn't work. If the disks are too close sparking can occur between the disks at the top and bottom quadrants, wasting energy. There is an optimum spacing, between these limits. For a small machine it is as close as possible, but for a large machine can be 1 cm or more.
Use ball bearings mounted in the bosses that hold the disks. The shaft (upper axle) can be conductive. With symmetrical voltages at the terminals it is at ground potential. The bosses are better if made of insulating material, but this is not critical.

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Wed May 14 2014, 03:51AM


So to be clear, while they have different terms in different applications, they are the exact same property, right? There is no case of something insulating well but being a poor dielectric, or vise versa.


Not doubting, but I don't understand how this can be true. Maybe I missed something.

Suppose:
- The disc is separated by, oh, 2cm, and,
- The sectors are 1cm away from the edge of the disc, and,
- The machine will generate 350,000v which normally shorts across the spark gap.

With only 4cm total airgap between sectors from one disc and around to the other side of the other disc, how does the machine not short around the disc edges as soon as the voltage potential is sufficient to do so (long before it bridges the spark gap)?

Re: Giant Wimshurst Machine - could use some guidance
kilovolt, Wed May 14 2014, 07:41AM

Hello Matt

This is a very interesting project indeed
I've built two wimshurst machines, one which is extremely simple with CD-Discs, the other one with acrylic glass discs with 30cm diameter.

In practical, the real challenge in building such a big wimshurst machine will be the parallel rotating of the two discs with a gap between them as less as possible. This will be by far the most difficult issue in the building process. Of course there are some other aspects as for example that every conductor must be rounded down at these voltage levels, because the very small power of such a machine shouldn't be wasted witn corona discharges. But in fact, the mechanical aspects are the most important ones.

Very best regards
kilovolt

Re: Giant Wimshurst Machine - could use some guidance
Finn Hammer, Wed May 14 2014, 09:02AM


At the 9 hour, and the 15 hour position, where the charge collectors are situated, there is no potential difference between the sectors on the 2 disks, therefore no possibility to arc. The potential difference is between 9hour position and 15 hour position.

The machine works by establishing a charge difference between sectors on opposite plates at the neutralisor position, where there is a relatively big capacitance between these sectors, then move these sectors as far away from each other as possible, lowering the capacitance, and, in turn, increasing the potential.

Hope this helps.

Cheers, Finn Hammer

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Wed May 14 2014, 09:47AM


I think my solution to this will be to glue large (1" thick) acrylic circles onto the piece, inside of the sectors near the axle. I can't do that between the discs, but on the outside there should be no size constraints. This will help provide some rigidity along the length and help keep it square and 90 degrees to the axle.

I might even make several such inner disks, even 1" at 48" diameter is a pretty thin wheel.

For me personally, your comments strike a particular note as I often handle the electricals no problem, even the large components easily, but it's a matter of "Okay, now how does it mount/couple?" and that takes up most of my time.

Build a 170VDC power supply from junk? No problem. Few minutes to wire it. Mount it inside a case somehow? Rest of the day.


Ahh, so if I've understood correctly, the maximum potential *is* between discs, but 180 degrees across the opposite disc. So, they will be actually close to 48" between max potentials (and decreasing the closer they get, self-solving the issue).

If so, I do understand it better now, yes. Thank you.

Re: Giant Wimshurst Machine - could use some guidance
Antonio, Thu May 15 2014, 12:39AM

About the distance between the disks, I made this machine, where the distance can be easily adjusted:

Both driving pulleys are at the back side, with one turning the axle, fixed to the front disk, and the other the back disk. Four ball bearings are used, two to hold the axle and two in the boss fixed to the back disk.
I tried also the sectors covered by an insulating layer and accessed through buttons. The idea worked very well.

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Thu May 15 2014, 01:44AM


Oh I see now. Interesting. I presumed the amount of current pulled off the wheels was related to the amount of brush contact area (bro-science heard elsewhere), but it seems evident from your experiments that the size of the sectors determines current per speed and the pickups only need to make small amount of contact to transfer the charge.

Sadly, aesthetically, I think having visible sectors is desirable. If I could cover them with a clear film (48" wide packing tape) I would do that. It would keep the sectors nice and purdy but, I guess it would look like old packing tape after a while.

I think I'm getting the hang of this.

On spacing between sectors...

Maximum voltage is at 180 degrees on a wheel, right?

So, the space between sectors must cumulatively add up to more than the desired spark gap, else it will short across the disc (another reason to laminate an insulator over them), right?

Is that basically the only reason you need a bigger wheel? Just to have sufficient space between sectors to actually get that arc, or are there other elements of physics in play?

I'm curious about the number of sectors. Why have, for example, 24 instead of 240? What impact does the number of sectors have on a machine?

Re: Giant Wimshurst Machine - could use some guidance
Dr. Slack, Thu May 15 2014, 08:00AM

If you want to see what a machine looks like in the limit of an 'inifinite' number of sectors, have a look at the Bonnetti machine. It's basically a sector-less Wimshurst. The drawback is that whereas a wimshurst will self-start, a Bonnetti needs to be started (needs a few kV to get the cross conduct brushes emitting, whereas the metal contact on the wimshurst cross conductors will conduct from nearly nothing). Ceratinly from a looks point of view, a winshurst is a better proposition for a gallery.

Re: Giant Wimshurst Machine - could use some guidance
Wastrel, Thu May 15 2014, 02:04PM

There are discontinuous points along the wheel, such as the reverse side where neutralisation happens. I'm under the impression that the gap between sectors needs to be a minimum amount how ever many you have, so it's a fight between arcing, corona and having enough metal to move the charge (unless you are spraying as in the Bonnetti machine).

I've suspected for a while that because charge is being moved against a voltage gradient and then is collected on the inside of a conductor that Van de Graaf action is happening too. Antonio's point about the angle of the neutralisers would seem to support that theory.

I think a lot of theoretical factors are less important than rules of thumb and trial and error, since what is going on is not simple.

Re: Giant Wimshurst Machine - could use some guidance
Newton Brawn, Thu May 15 2014, 02:48PM

Hi Everyone,

As advised by Antonio, the machine with 2.15 m disks:

Is one disk is in movement and other disk is stoped ?

Or both disks are turning, in oppositive directions ?

Thanks

Re: Giant Wimshurst Machine - could use some guidance
Dr. Slack, Thu May 15 2014, 06:45PM


Both Wimshurst discs rotate in opposite directions

Re: Giant Wimshurst Machine - could use some guidance
Finn Hammer, Thu May 15 2014, 07:54PM

Matt,

I made some Wimshurst machines for the local Electricity Museum some couple of years ago. They had the disks made from FR4 pcb material, and with soldermask covering the area between the gold plated sectors, and 1 mm into them. The small holes at the inner end of the sectors were occupied by round headed phillips screws, which acted as buttons to make contact with the neutralizer brushes.





Another thing always anoyed me, was the crossing belt, which tends to wear out and spray the surface of the plates with rubber dust. Crossing belts to reverse the direction of rotation is an unacceptable makeshift way of doing things.
Using only one belt, double growed big pulleys and 2 extra small intermediate pulleys, this problem was overcome:





This mechanism fits into an ordinary frame.



Cheers, Finn Hammer

Re: Giant Wimshurst Machine - could use some guidance
Antonio, Fri May 16 2014, 12:31AM


Nice disks. Screws to access enclosed sectors shall be used with care because they can't perforate the disks. The disks have to be thick enough, or an insulating layer must be laminated on the inner side. In the Wimshurst I just glued the buttons over thin metal strips contacting the sectors below. A fragile solution, but worked.
There are several methods to avoid crossed cords. One is to mount the lower axle perpendicular to the upper axle, and use a single cord with an idle pulley:

Another is to mount the lower axle inclinated to one side, so the crossed cords don't touch.



I used adhesive plastic foil. It keeps the same look for long time. Could be transparent too.

The machine sparks through the disks if a too long spark is attempted, in the path going from one collector across the spacings of sectors to one neutralizer, continuing to the other collector through sector spacings from the other side of the neutralizer.

Longer sparks are the reason for larger disks, that also produce greater current due to the greater area of the sectors.

More sectors accelerate the startup of the machine and increase the spark length, but up to a point. There is no great reason to use more than 40 sectors. 32 is a good number, 24 is ok too, 16 causes some degradation, 8 is about the minimum.

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Thu May 22 2014, 03:33AM

I'm now in charge of building a prototype, not just giving some electrical specs.

Monday: "So how long do I have to build this thing?", "Well, soon, about 3 weeks, is that enough?", "It seems like lots, so it's probably not long enough."

Today: "We need it built and fully documented in a week."

Well okay then. Off I go.



Trying to decide on the right thickness of acrylic to use. It's expensive and I won't know until I get it wrong that it's wrong.

- Can't be too thick, or the current will be low.
- Can't be too thick, or it'll be a scary flywheel with a lot of energy (already looking like, 150 pounds of wheel weight).
- Can't be too thin, or mechanically it won't be stable.
- Can't be too thin, or electrostatic attraction will smash discs together.

No thinner than 1/4"... hopefully not as thick as 1/2". 1/4" was pretty wobbly with the 36" piece I held up.

I will probably buttress it with a thicker disc in the middle inside of the sectors. Another option is sandwiching the sectors between two discs, so that they're at least electrically close to the other wheel. Fill in the gap with silicone and smush it together with clamps.

Acrylic will be hundreds of dollars to maybe a thousand.



So, the wheels spin in opposite directors. Thus, they can't be locked to a shaft. Which is fine, they're driven by the other pulleys.

I had a hell of a time trying to figure how I'm going to attach smooth bearings to pulleys to the big wheels, all while not locking onto a shaft. This was my "solution".

Use bushings instead of bearings. 1/2" shaft, 3/4" bushings. Bushings fit inside the pulley and the collar thing. I weld a giant washer type plate to the collar, and then screw/bolt that through to the plate, flush.

I can't just use the pulley itself, because there's nowhere to bolt it to the big wheel. No material. And I can't weld a disc around it, because, well, at least at Princess they said it was cast iron. I dunno, looks pretty smooth for cast iron. It doesn't have the crumbly texture like other cast iron ones did. Anyone figure it's gotta be steel? It's no alum...



Also, I mentioned contacting the local power company for old stuff. They said "Oh, we were just there the other day, I'm going back this week, want to come with?" Here's what they pulled out just 'cause it looked interesting.









Apparently about half of the insulator thingies are actually not insulators, they're explosive fuses with a shotgun shell in them to blow apart the wires if they overload she said. I thought that was pretty interesting. The discs are rubbery on those, not ceramic.

Mmmmm.... tasty Pole Pig. Maybe I can score one for a Tesla Coil :)


Oh, and a few more questions...

In the previous post, the end caps for the 5/8" tubing, will that work? I'm not actually sure how to terminate the pipes. I've seen brass balls and stuff, is that too ugly/sharp? Do they need to be spheres?

Will the tubing be enough for the neutralizer bar and comb supports? I was planning on only using the 1" straight pipe for the output rods.

Do the combs actually touch the wheel? Some people said no, but in the tabletop one they do. In the tabletop one both the brushes and combs are made out of solder wick. I was thinking of using photocopier destatic brushes, hovering just barely.

Are the Leyden Jars connected to each other? I think the outer conductor is connected in common?

How thick do my Leyden insulators need to be? I was hoping to use just 4-6" PVC tube, cut however long. So, that stuff is.. I dunno, 1/8"-1/4" thick.


I'm a little bit panicking for time. I have enough time to build, but not a lot of time for things to go wrong with the build.

Re: Giant Wimshurst Machine - could use some guidance
Eleccentric, Thu May 22 2014, 07:43AM

Since this is a prototype, I suggest you use the tallest and most narrow plastic trash containers you can find for the Leyden jars. They will be made out of polypropylene, which is a much better choice than PVC, and you won't have to worry about sparks at both ends. Yes, connect the outer foils of each jar to one another.

When it comes to your brushes, those stiff brass ones you purchased are much too abrasive. They will scratch and ruin your sectors and disks. The neutralizer brushes should definitely touch the sectors. The high voltage collectors don't have to touch the sectors, but it may work better if they do.

You can also use wooden spheres for the joints in the high voltage conductors, so long at the metal bits make contact inside the sphere. Be sure to give them a smooth, glossy coating of paint or varnish.

The cheapest source for hollow metal spheres I have found are stainless steel gazing globes. A web search should turn up plenty of sellers. You really need something like these to terminate your high voltage conductors if you want to see some long sparks. Weld on a small stub of threaded bolt stock and drill a hole in the center of one of your copper pipe end caps, use a nut and lock washer to secure it, then just slip onto the end of the pipe.

My best performer uses a 4" stainless gazing globe on one side, and a 1.25" sphere stacked on a 2" sphere on the other. The latter were taken from two sets of Baoding balls (Chinese exercise balls).

I know you only have a week for this prototype, but when it comes to building the real beast I highly suggest you purchase a copy of Homemade Lightning by R.A. Ford and read the sections on Wimshurst machines as it contains a lot of best practices, though he focuses on sectorless designs.

The anti-static brushes from a photocopier will work very well as neutralizer brushes.

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Thu May 22 2014, 05:05PM


Very interesting, thank you. I am somewhat scared of Leyden jars and I almost don't want to use them, or at least at first, as little as possible.

I actually need to read up on Leyden Jar construction more, what parts have to be insulated from what, etc. I don't have bottoms for the PVC right now.


The other feedback I've got on it was that they are not hard and springy enough. Heh.

On a prototype, I don't care much, but, also within a week, I need to have documents written up describing to an artist and a fabrication shop how to make these decisions and build one (they'll decide how to build it, I have to tell them what they can and cannot do). I found some stainless foil on McMaster, so, I'll suggest that for the final build.


Why would I use them at all? For example, why not *only* have the metal?

Will the wood prevent corona discharge from bad/pointy joints or is it purely mechanical the way you're suggesting it?



Bingo. Thank you muchly. $110 for 2x 4" and 2x 2" on McMaster for stainless floats. Instead of doing that, $70 for 4x 5" and 4x 2.75" for Gazing Globes from Amazon. Great.



Thanks for the tip, I think I will use this method. But, won't there be weird angles and hollow spaces between the two? Do I need to fill those with solder?

For exaggerated example, I am imagining a Basketball sitting on a table, there's all that convex space underneath it.


Interesting. So, why did you go with the

Large <--> Medium/Small

paring rather than

Medium/Small <--> Small/Medium

pairs on each side?



Told them to buy the E-book and I'll rifle over it at nights when their shop is closed.

Thank you again.

Re: Giant Wimshurst Machine - could use some guidance
Eleccentric, Thu May 22 2014, 06:43PM

The machine will run without Leyden jars, but the sparks will be weak and not as long. It will be very informative if you run it in a dark room after you've let your eyes adjust for 10 minutes. Set the elcetrodes far enough apart that no sparks appear, and the whole thing will light up with purple and white glow discharges, and you will see a stark difference between the side with negative charge and the side with positive charge. You will also see all the points of corona leakage on your high voltage conductors, like little purple down feathers. The fewer of these that occur, the better your machine will perform.

The neutralizer brushes only need to make electrical contact with the sectors, and since we are talking about very high voltage with extremely miniscule current, even something with a very high resistance like the anti-static brushes from a photocopier will work as well as something much more conductive. Those brass brushes you bought are intended to be abrasive - you can remove rust and corrosion with them while not leaving deep scratches in steel. The carbon fiber brushes from the photocopier are designed to do exactly what you want them for - to pick up a static charge from a delicate surface - whether it's paper or foil or plastic doesn't matter. You could use the brass brushes as collector combs for the high voltage pickups, but don't let them touch the sectors. Also, bear in mind that you do not need the collector brushes/combs to cover the whole length of the sectors. So long as at least some part of the sectors pass underneath the brushes, pickup will occur. The further inward that your brushes reach, the lower the ultimate voltage of the machine.

The wood suggestion is for ease of machining and lower cost. The wood will shield the joint in much the same way that metal would. I have not done this myself, but from what I've read this is a viable alternative. It will be much easier to carve a wooden sphere to have involute edges around the conductors than to machine a hunk of aluminum or brass to the same shape. The involute edges are a refinement, don't worry about it unless you get to the point of tweaking things. I've used normal plumbing pipe T-unions with good results, though the edges of the union are a source of leakage. a bead of solder run around the edge and then filed/sanded/buffed smooth to make a gentle transition should eliminate this as a problem. I didn't do this since I wanted the parts to remain removable. I filed down the edges anyways, which may have helped.

A better solution than directly welding a stub would be to use a steel T-nut deformed into a cup shape that matches the curvature of the sphere, and silver-solder it in place. The stud would be secured to the pipe end-cap and then the T-nut would thread down onto this. The proximity of the sphere will shield the "sharp" shape of the conductor immediately beneath it - the large radius of the sphere forces the E-field to have a small gradient.

The electrode configuration was chosen since that's what the machines making the biggest sparks use. It was also limited by what I had on hand.

Good luck!

Re: Giant Wimshurst Machine - could use some guidance
Newton Brawn, Thu May 22 2014, 07:44PM


Awesomatt,

Well, a good start.

Maybe you may start with sketching the wood base, adding the dimensions and the details how to joint the structural elements...
The wood base has to provide suport to the drive shaft and weells shaft...
If you post the sketch I can draw in Autocad
Regards
Newton

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Thu May 22 2014, 09:40PM


Oh, that's new info to me. Why do neutralizer brushes farther inside reduce the voltage?

Is that true of the combs as well? I was figuring the combs should cover the full length of the contacts.


I was planning on using plumbing fixtures as much as possible, yeah.

Newton - Thank you very much for the offer but they have in-house people to do that for them. I just have to have things ready for them to describe how much artistic and engineering license they have with it.

Re: Giant Wimshurst Machine - could use some guidance
Eleccentric, Thu May 22 2014, 10:44PM

I was referring to high voltage collector combs, not the neutralizers. I use the terms brush/comb interchangeably, since either could really be either.

A search of images of Wimshurst machines will reveal that many do not cover the whole breadth of the sector with the high voltage collector. Some use a soft brush in contact with the disc, some use sharp pointed tines of a comb that do not touch the disc.

Re: Giant Wimshurst Machine - could use some guidance
Antonio, Fri May 23 2014, 01:46AM


For a very high voltage machine, no sharp corner or end in the conductors can exist. An assembly of balls and tubes works well. The balls can be made of wood, as said, with the tubes in contact inside them.

The neutralizer brushes must touch the disks, lightly but with good contact, or the machine does not start. The charge collectors don't have to touch the disks.

The outer plates of the Leyden jars are in contact. I like to put a secondary spark gap between them. High-voltage pulses appear there when the main terminals spark.

The jars must be thick. About 4-5 mm, probably, is enough. Two jars in series can be used for greater insulation, one inside the other. With tubes you need to close the bottom, what is almost impossible, or just leave a margin as great as in the other direction, with the internal and external plates at the center.

Those nice ceramic insulators can be used in the assembly, if you find how to fix them to other parts.

About mounting the disks on the uper axle, I use a single steel axle, with two ball bearings at each of the bosses, with the disks fixed to the bosses with three flat-head screws. Metal disks can be used at the inner side to avoid stressing the disks, and rubber spacers between the disks and the bosses, allowing some adjustment of the verticality of the disks by the pressure of the screws. I make first the holes in the disks with the exact size of the axle, and once everything is aligned and the screws fixed, I enlarge a bit the hole so only the bearings touch the axle.
To obtain uniform flat disks in acrylic is not easy. Select the plates when buying them, looking for flatness and uniform thickness.

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Sat May 24 2014, 03:14AM


I've seen both styles yes. It's the one piece of the machine I don't really understand how or why it works. How they pick up voltage and what they do.

I've seen the pointed tines, I wondered if they are supposed to be sharp on purpose, or if they should be blunted. Or if actual contacting brushes are easier.

I like the idea of combs simply because, visually, it's different and easier to explain that they have a different purpose.

Today's Progress:

- Got the ugly 2x4 frame and MDF baseplate complete
- Settled on an acrylic thickness at the shop (3/16", 4.75mm)
- Settled on height, drilled out the wheel axle (upper) mount
- Mounted the crank pillow block bearings for the (lower) crank
- Drilled and bolted the 6" pulleys to the 12" ones (12" ones needed some way to afix to the shaft, 6" were bought earlier and were supposed to be returned but under time crunch I'm using those pulleys just as a collar with a set screw).
- Arranged for one friend to lasercut the giant wheels at the local hackerspace.
- Arranged for someone else to use the big CNC Shopbot router to cut the wheels, as a backup plan.
- Figured out a mounting method for the big discs to the little pulleys to the upper axle, and for someone to help lathe the discs (little pulleys are steel, not cast iron, meaning they can be welded, so I'll weld a disc to them, which bolts to the shaft).
- Ordered and rush shipped 4x 5" and 4x 2.75" spheres (thanks Eleccentric for the tip!), it arrives tomorrow.
- Ordered and rush shipped Homemade Lightning book, arrives tomorrow.



My philosophy is that the only tangible reward people get for taking time out of their day to help me, is seeing that their help made a difference. So as promised, I'm making a best effort to document the build in as interesting a way as possible.

Here are the pics I didn't take yesterday. The 6" pulleys ($15 each?) used as collars, bolted to the 12" plastic pulleys (machinable plastic? From some coathangered exhibit).



And the frame as of last night:



Ghetto mounted pillow block bearings ($6 each?). I will have to go back later and bolt them down properly somehow. Or not, it's just a prototype.



Closeup of the large pulleys.



And today's work begins! Lower drive assembly is complete today. A couple pics of it mounted and a handle attached.

That took me a couple hours. The axle did *not* want to go into those bearings. I don't get it, they say "China" right on them, a country world famous for its craftsmanship!

I ended up slightly bending the 1/2" axle trying to hammer it on there with a rubber hammer on a 2x2. Nope. Out comes the 20 ton shop press. Oops, I did it wrong about 1/4 of the way in, flip it around, press it out, start the other way and continue. Took a while to tweak the spacing even preliminarily.



The handle was meant for a 3/4" shaft. It has a set screw, so, some masking tape is working magnificently as a cylindrical shim:



After trying a scribe on a swingarm (worked well but slow), a laminate cutter on another swing arm (melted where I paused to change my grip) earlier this week with moderate success on sample pieces... the 3/8" acrylic arrived today and it was time to put the shopbot to use because computers are faster, right?

2 hours later, we got it to cut (8 minutes total cut time). Had to manually play with some G-code to get it to avoid the center where we bolted that big plate. Took a while to jig up. First time we tried cutting at 6" per second which snapped the bit after a foot. 1" per second with the new bit. Videoed this for later.



Some to-be-repurposed PVC for Leyden jars, maybe, if that's what works.



The gazing globes arrived. I ordered a string of 8 (4 medium 4 small), so they have small holes in them. Bonus! This will help me align them for mounting. Only the tip will need to be filled with a finishing nail ground smooth or something. 5" and 2.75", on a 1" pipe (just laid out, not mounted):



Rollin' rollin' rollin', let's get those big wheels goin'! H'yah!



Quitting shot for the day.

Re: Giant Wimshurst Machine - could use some guidance
Ash Small, Sat May 24 2014, 10:13AM

You should be able to solder the stainless spheres with silver solder and a strong flux, if required.

Re: Giant Wimshurst Machine - could use some guidance
Antonio, Sat May 24 2014, 01:10PM

Imagining how you will fix the small ball to the larger one. I would try to avoid solder, but this is an option. The frame seems be too close to the disks. They will spark to the frame close to the neutralizers, if they are set at a high angle. Why the double pulleys below?

Re: Giant Wimshurst Machine - could use some guidance
Dr. Slack, Sat May 24 2014, 01:43PM

To reinforce Antonio's point. At the voltages and currents involved here, wood is a conductor. If you do a google images search for Wimshurst machines, they *all* have a thin vertical frame that follows the zero potential region up the middle of the discs. The voltage increases to each side of the discs, becoming maximum where the takeoff combs are located. Any significant width on a frame will tend to short out the two sides if it is too close to the sectors.

You may want to rebuild your frame now, so that the diagonal elements become mere corner braces at the bottom, not overlapping the discs, rather than reaching up all the way to the axle. Obviously that's not going to be as stiff as you have at the moment. Then again, you might want to continue this build as is, to get your feet wet, learn whatever else you can at the same time, bearing in mind the sort of rebuild that might be needed next.

Re: Giant Wimshurst Machine - could use some guidance
Ash Small, Sat May 24 2014, 03:59PM


I was thinking more for joining the sphere to the copper tube. It is tricky soldering stainless but it can be done.

I've no idea how to join the two spheres, other than drilling two opposing holes in one, and soldering/welding some threaded bar onto the other, passing the threaded bar all the way through both holes in the other, and securing with a nut, and then mounting the sphere with two holes in so that the nut is inside the copper tube. (I can provide a simple sketch if clarification is required.

Re: Giant Wimshurst Machine - could use some guidance
Eleccentric, Sun May 25 2014, 12:16AM

A thought on the material making the frame: perhaps composite decking boards would be an affordable and much less conductive alternative to wood. I'm not certain of their composition, but it appears to be some sort of easily machinable plastic.

I suppose it would also be possible to braze the stainless spheres together, but it would have to be cleaned up afterward with files followed by progressively finer sandpaper to get back to a nicely smooth surface.

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Sun May 25 2014, 07:17AM



Hrm. Crap. I was mostly just scared of 100 pounds of counter-rotating flywheels not being braced like hell.


I had it in my comments... From the first place I went, 6" was the max. Then I found the 12" pulleys in the shop, but they were just bare plastic pulleys, no way to mount them. Since time is an issue, I just bolted the 6" pulleys to the 12" ones because the 6" ones had a set screw.

So, they 6" don't do anything other than afix the 12" pulleys to the shaft. And.. if needed, I could actually use them I suppose, if I wanted a 2x smaller ratio.


I knew this, sort of. It's the reason I rejected plywood or MDF wheels. But I chose to build it this way anyway. I thought it would be a small issue (wood isn't *that* conductive). I see I was wrong.

Again, I was scared of the flywheel energies.


No time to build multiple versions. The need to know if it's a doable project by Friday (working prototype) or they pull the plug and go with something lamer and less challenging (Jacob's Ladder or somesuch).

It's the centerpiece/showpiece of an 8-exhibit electrical thing. The other exhibits you learn things, this is to wow and get people talking.

So, what I will do is mount the wheels and crank them up to speed, get a feel for what gearing is reasonable. When I see what the rigidity is like, I will do as you suggested and chop the diagonals way down to corner braces and see how unstable it gets.

The A-frame is actually almost 4" tall (the upper axle is near the top) specifically so I had lots of wiggle room, so I could still have diagonals going 2' up instead of all 4.

Another thing I will/could do is space the frame out farther on the axles. There is maybe 6" of room between the A-frames, the axles are 18" long. The base is I think 30" wide, so, lots of play room there. The A-frames are built as individual units first, then mounted to the platform, so, moving them is as simple as changing 4 screws.


I understood. I may do this.

Or, I may TIG weld a metal screw onto the bottom of the small one and just thread it right onto the big one. Maybe squirt some JBweld into the hole on the big one before I screw into it and then let the JB weld add some internal support (let it cure upside down so the epoxy cures against the screw inside the ball. The walls are very thin.

Maybe I'll just drill a hole, weld a nut sort of flush, and a bolt to the other globe and screw them in. It's basically the method I'm using to fix the globes to the copper shaft, only I don't have access to the opposite side of the shaft.


Well if it comes down to it, there's lots of scrap acrylic sitting around.

Nylon rope tethered and tensioned to the peaks and corners instead of the diagonal braces could work too I think.

...

Not much of an update today, was busy doing other things. Homemade Lightning arrived, and I did a couple hours of shopping for plumbing fixtures to solder the copper tubing together.

Thank you all for the continual support, feedback, criticism and interest. Seems every time I get frustrated with an indecision or roadblock someone in the community has come to my rescue.

Re: Giant Wimshurst Machine - could use some guidance
Ash Small, Sun May 25 2014, 11:23AM

Just a tip, if you do try TIG welding the spheres, I'd drill them and add a supply of argon to the inside, otherwise you'll probably have some problems.

Re: Giant Wimshurst Machine - could use some guidance
Antonio, Sun May 25 2014, 12:37PM

About the frame, the solution of increasing their separation seems simpler, but you can do this after testing the machine, if some obvious leak appears. This machine will be hard to turn when charged. You will probably not be able to turn it fast enough for vibration problems. Allow for some method of increasing the separation of the disks, as larger separation turns it easier to turn, at the expense of slower charge buildup. The methods for assembling the spheres seem good. The extra metal pulleys can be used later for a motor drive.

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Tue May 27 2014, 08:56AM

I read most of R.A. Ford's "Homemade Lightning". Didn't answer most of the questions I had, scared me off of the stuff I thought I knew :(

It's becoming more and more obvious that this is the kind of machine that does not show fractional progress. Up until it's 99.5% done you get *nothing*, and then that 99.5-99.9% is where you progress through your entire results.

Intuitively, it would seem like "Well it works okay but not great, 60% spark distance until you go back and polish everything and make sure it's clean and joints are covered", etc etc. But that doesn't appear the be the case. It won't do a damned thing unless it's nearly perfect.

And, deadline looms, which adds stress to all decisions because there's not time to experiment or tinker.

Today's progress:

First, just because it feels like progress, I put the wheels on the upper axle. Was a waste of time and counter-productive (they have to come right back off), but, was satisfying to see anyway.



It's fairly large and intimidating:



The disks are 3/8" acrylic but I want to avoid as much wobble as possible, so I plan to buttressed them with 3/4" disks 21" in diameter.



I got to the shop around closing time today, so, instead of having help with the Shopbot, I drilled a hole in the router table, mounted a screw and churned out the new circles myself. Not bad.

The assembly I have the least confidence with right now is how I will be driving the big wheels. Note the little 1" pulley below. I'm going to drill into the collar side of that, tap 4 holes, and... hopefully spin both the 21" buttressing shoulders and the 48" wheel off of that. The shoulders and the main wheel will also be bolted together with nylon bolts and either nuts or I"ll tap threads into one of the pieces of acrylic.

I'm just not confident spinning a 48" 100+ pound disk from 4 nylon bolts an inch and a half apart from each other. Maybe I"ll also silicone the pulley to the shoulder?

In the past I considered welding a flat disc to the 1" pulley itself and then bolting that to the shoulder, but, Homemade Lightning poo-poos the use of metal just about anywhere. Also, there were questions as to whether the plate could be balanced (I think a small issue, and, turn it on the lathe to make sure).



Output terminals. I figured I'd solder (press fit for now) a T-joint onto the 1" copper pipe. It's nice and smooth, graceful curves. One piece of wood will handle the hinging action, the other will be the manipulable handle (though probably PVC to avoid conductivity to the user).



A bunch more little T-joints for the 1/2" copper tubing (combs/neutralizers), I figure I can make most of the U-shapes out of these, as well as use them to connect to the leyden jars.

Also, bought some reducers, they're smooth tapered enough I hoped. This would help narrow down to the neutralizing bars or something I figured. Instead I'll probably just go buy some ball bearings or brass balls.



Oh, and an action shot from cutting the shoulder disks.




It's passed the point of being fun and interesting due to the time crunch, now everything I do has "#### I hope this works/I don't screw this up/It doesn't take that long" looming over it. Tomorrow lots of shopping for joining hardware and probably some sector cutting.

Re: Giant Wimshurst Machine - could use some guidance
RAJEEV TUTEJA, Tue May 27 2014, 03:26PM

i am also making one with 36" disks. instead of frame i had got some carpenter to turn me stands for mounting.
some pics attached

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Tue May 27 2014, 07:11PM


Neat. Thanks for sharing.

My plan is:

First make it work, then
Make it work better, then,
Make it pretty.

Re: Giant Wimshurst Machine - could use some guidance
Eleccentric, Tue May 27 2014, 09:48PM

Don't let Homemade Lightning get you down - that book details how to built the BEST possible machines, and so focuses the finest details. It also is for sectorless machines, which are much more finicky. A machine with sectors will give you something even if it is built poorly.

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Tue May 27 2014, 11:50PM


That made my day, thanks :)

Re: Giant Wimshurst Machine - could use some guidance
Antonio, Wed May 28 2014, 01:07AM


You can test the machine after the neutralizers are in place, before mounting the terminals. You will see the disks charging and the cranking become difficult.

The frame could be smaller. The disks can come quite close to the lower pulleys without leakage, since the voltages at the bottom are small.

The reinforcing disks are a good idea. No problem in fixing them with nylon screws, but keep their holes distant from the sectors.

The small pulleys fixed to the disks shall have two bearings each, or a long metal tube forming a journal bearing over the axle. They also can't be too small, or the driving belts will slip. No problem in fixing the disks to them with metal screws from inside. Read what the book says about the precision required on the bosses. As they essentially control the parallelism of the disks their construction is critical.

Avoid silicone glue, or any glue. Glues are useless in blocking electricity and are ugly.

Use plastic for the handles. Wood is useless as insulator. PVC tubes are ok.

Be careful to not scratch the acrylic when making these disks. Keep the protective covers.

Re: Giant Wimshurst Machine - could use some guidance
Newton Brawn, Wed May 28 2014, 02:38AM

Hi Rajeev ,

I like the two posts supporting the disks, the style follows the time when the machines begining the generation of the electrical generation...
Conratulations, keep posting the pictures.
Newton

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Wed May 28 2014, 03:07AM


Hrm, was about to do that now.

How distant is "distant"? 48" wheels, 21" reinforcing discs, so there is 13.5" of space around the reinforcing discs. That has to be shared by sectors and any isolation gap I need.

I haven't even thought about how tall my metal sectors would be.

If anyone wouldn't mind giving this a stupid-proofing, here's my logic:

If max voltage is from the left side to the right side of the big wheels (where the combs are), and I have 40 total sectors, that means 20 total sectors per half. That means the space between sectors must be greater than t size of the arc I want to achieve (18"). Call it 20" so the math is easier. That means I need 1" separation between each sector (20" total across 1/2 the disc).

I don't want the sectors ending in sharp points, so there's no purpose in having them dagger down all the way, so, call it... half inch min width near the bottom of their rounded-trapezoid shape. So... 20x 0.5" = 10", plus 20" of separation... = 30"

Since that's across a half disc, my circumference needs to be doubled to account for the whole wheel (60" minimum).

Circumference = 2 * pi * radius
So,
Radius = Circumference / 2 * Pi
Radius = 60' / 2 * pi
Radius = 9.55" away from the center.

Well, my reinforcing discs are already 10.5" away, so, I will be trimming the metal sectors much less long than they could be.

Same math using 1" sector min width and 1" separation = 12.75" min radius.

Anyway, suppose it's something around there. What would be the necessary amount of separation? (The measurement marked "???")




I couldn't figure out a way to make bearings work, so I used phosphor bronze bushings instead. They seem to be okay so far. Per side, I am using 1 on the pulley and one for the two discs (4 total).


Whew. Good. I was scared with the nylon here. Metal it is!



The trouble is also that I do not have a drill press with a 24" long arm, so I can't be sure I am drilling the axle/bushings holes 90'. I have to use a hand drill.

If they end up crooked, I will have to shim where they attach to the pulley, or, use the lathe to "face" the side of the pulleys.


Oh? Hrm. Are they conductive, or is the issue the difficulty in applying them consistently?

For example, if I apply silicone to the two discs prior to screwing them together with nylon bolts, then squish the faces together, I think they will seal up just fine (not that they need to).


Yep, they're coming off when I have the sectors cut, and not before.

Re: Giant Wimshurst Machine - could use some guidance
RAJEEV TUTEJA, Wed May 28 2014, 03:51AM

for sector design i used a program wimshurt machine designer (WMD for short) and then i had a screen shot of the same which i imported into coreldraw and made the template for my size of disk.
photo attached

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Wed May 28 2014, 07:25AM


I searched for, then found this. I was thinking "*This* is the guy I should be talking to!"

And then I found out it is Antonio. One of the people here who has been most helpful to me :)

Since by Friday I'm supposed to convince people that this can be done... this may help a lot.

I crunched the numbers I arrived at for my design... lo and behold it suggests that it's possible to do exactly what they want with what I am building.

Re: Giant Wimshurst Machine - could use some guidance
Ash Small, Wed May 28 2014, 08:18AM


If you do have to use a hand drill, make sure you have at least one assistant to 'sight' the drill and tell you if it looks vertical. You may need two assistants if you are drilling vertically.

Another option (if I understand your design correctly) is to drill the holes in the plastic oversize, and then centre everything up when you attach the pulleys (I'd still use the above method for drilling the bolt holes).

EDIT: Another option is to use a 'MAG drill' (drill with magnetic base) if you have access to one. Lay a piece of heavy, flat steel on the disc and mount the MAG drill on that. You obviously need to take care not to scratch the disc, though (a second plastic sheet between disc and steel?). Once the drill is positioned you should be able to put some weight on it to hold everything in place while you drill (carefully). It's better to clamp the steel to the disc, but if you are careful, you may be able to get away with using an assistant to hold everything in place (maybe stand on it). Clamping would be safer!! (clamp everything to the bench, maybe, using extra plastic sheets to 'sandwich' the disc?)

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Wed May 28 2014, 07:04PM



I was alone in the shop, worked until 11pm.

Fairly confident I could drill straight down if I just observed my posture, I've done this before when it was the only way and didn't do too bad.

Didn't matter, the drillbit was a little crooked and it wandered off side, wobbbled in the hole (oversizing it) and messed up a couple hundred dollars worth of acrylic.

My junior high shop teacher's motto: "Rushing ruins things"

Knew it was the wrong method, knew I was rushing, just didn't have time to think or plan a better one.

Bought more plastic today, going to try again I guess.

Frustrating and discouraging.

That's not even the hard part, the hard part is getting 4 holes in the side of the 1" pulley and trying to use a 2" wide face to steer a 48" disc.

I said last night my odds of finishing on time dropped to 50%. That was probably overly ambitious.

Re: Giant Wimshurst Machine - could use some guidance
Ash Small, Wed May 28 2014, 08:50PM


Make a 'template' on a pillar drill. A disc of steel, maybe, narked out, centre-punched, and drilled accurately. Drill the centre hole undersize, drill a matching hole in the centre of the plastic sheet, and bolt the template to it, then drill the boltholes. Then mark out the disc itself, then drill out the centre hole in the template on the pillar drill again (you should be able to 'centre' it pretty easily, espacially if the drill bit has not been sharpened 'offcentre'-best to use a new bit here if possible, or turn up a 'point' on a lathe, for accurate centring), bolt it to the plastic using the boltholes, and drill out the centre hole, then cut the disc out (or, if you bolt the disc down to the table while cutting, cut it out before enlarging the centre hole).

Just my two cents worth

EDIT: I'd still advise arranging for an 'assistant' to 'sight' the drill for you, even using a drilling template.

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Wed May 28 2014, 10:53PM


This is basically what I did last night.

I cut one piece of 1/2" acrylic with a 1/2" axle hole, and then one 7/64" hole the right distance away.

Then, I took another piece of acrylic and drew a precisely square X on it, scribed lines fairly deep. I drilled out the center on t drill press to 1/2" when I was done.

Then I put a 1/2" bolt through the pair to secure them axially. I took the 7/64" drillbit in the drill press and plunged it through the first plate into the second plate where it lined up with 1 of the lines in the X. Then spun it to the next X, drilled again. Then a third time, then a fourth.

This made sure that my holes in the second template were all the exact same distance away from the center... and I had a jig I could place over the pulley to drill. I could also use the same jig to place over the acrylic.

But.. since I guiding myself through acrylic into steel, the steel shavings kinda abraded away the walls of the template a bit. So, makes it a bit of a moot point as a super-precise template.

Pulleys are now drilled and tapped. Once the acrylic shoulders are re-cut I can drill and tap them, put it all together, make up a belt and test the mechanical assembly.

Then, I have one day to make all the electrical assembly, diagnose it, etc.

Sorry it's been a boring read lately, I'll try to get some more pictures up tonight.


...

Questions:

1 -I have a question about the neutralizer bars. can they be shorted to each other? I.E. ... I won't do it purposefully, but if they're mounted basically to the axle, and the axle is metal, I figure there's not enough insulation there to prevent any voltage from arcing from one bar to the opposing bar through the axle.

2 - Antonio's WMD [ <-- search/scan for WMD] has a variable of "boss size" that, at some point, limits the length of the arc. Does this presume that the boss is made of a conductor? Or is it based on the fact that the screws (even if nylon) will puncture the discs? Or some other variable I have not considered?


*deep breath*

Monday or Tuesday is new deadline.

Whew.

Breathing room.



"Progress" of the last couple days:

Here's the "Center + 1 hole" jig I talked about earlier:



And here is the jig I used the other jig to make, to ensure all holes were equidistant from the axle. Also, there are the small pulleys that I drilled, tapped, and pressed bushings into:



Here is yesterday's ruining of a couple hundred dollars in acrylic. These are the 21" shoudlering discs. Holes are different sizes, and both are off center. Throw 'em away, cutting new ones tomorrow.



Also holesawed out a 2x4 base for the output supports (what the electrode arms will hinge on), and cut 2" PVC to length:



Will grow up to be leyden jars I hope. Take 4" PVC pipe (not shown), throw end caps on the bottom, screw caps on the top, and the screw in lids themselves will have the conductor in them.

I can cut them to be 24" tall or whatever they would need to be:



Chain, to connect the inside of the jars and the base of the jars to each other.



1/2" copper elbows for bends, and 3/4" vinyl tubing I probably won't use (wanted to sleave some 1/2" tubing over the copper, but it got stuck after about 3", so I bought 3/4" instead... which obviously looks terrible and saggy):



Some brass shim stock. Couldn't get phosphor bronze.



And the final result as of today (doesn't look much different, just the 2" PVC pillars added).

Re: Giant Wimshurst Machine - could use some guidance
Rod-on, Thu May 29 2014, 06:54AM

Fantastic project, you might want to take a look at a series of youtube video's made by Mr. Teslonian on how to make a huge Whimshurst machine from easy to find bits and pieces. Here is a link:

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Thu May 29 2014, 07:22AM


I'm familiar with his project.

It's basically a "How-NOT-to" series. He doesn't seem to understand how a Wimshurst works, so he copies without context and made a lot of mistakes, resulting in a very sub-par machine.

He's also nuts. He believes the pyramids were giant tesla coils and the water channels in them are conductors. He believes energy "flows" inside water from the atmosphere down to the oceans (electrically, not as moving water) and we could all have free limitless energy if we built giant tesla coils.

Poor reasoning in general surfaces in all decisions people make :(.

Thanks for the support though.

Re: Giant Wimshurst Machine - could use some guidance
RAJEEV TUTEJA, Thu May 29 2014, 08:40AM

QUOTE BY AwesomeMatt
"Here is yesterday's ruining of a couple hundred dollars in acrylic. These are the 21" shoudlering discs. Holes are different sizes, and both are off center. Throw 'em away, cutting new ones tomorrow."
well I also MADE THE SAME MISTAKE. then what i did was screwed in a nut with plastic washers to protect the acrylic to both of the disks and mounted on a big lathe at my friends workshop and turned the outer rim to make it concentric with the holes. sure the disks were left a few mm small but what the ????, will not make any difference at all.

Re: Giant Wimshurst Machine - could use some guidance
Antonio, Thu May 29 2014, 12:18PM

Several random comments:
In the WMD program it's assumed that the center bosses are conductive, so it looks at their distance from the sectors.
About aligning disks with bosses and centering holes: I make the disks by first making the central hole with the exact size of the axle and then cut the disks by turning them around a similar axle. I use a template with the same central hole for the screw holes in the disks and bosses, and once everything is fixed in place and aligned around the axle I enlarge a bit the center holes in the disks. The disks can be fixed to the bosses with flat-head screws from inside, with a thin metal plate between the screw heads and the disks to avoid excessive stress. Screws with protuding heads can be used too in a large machine, but this limits the spacing of the disks. I place a spacer of soft material between the disks and bosses, to allow adjustments on the verticality of the disks with the pressure of the screws.
Use a lathe to align face and hole in the bosses.
Note that the neutralizers shorten the distance for a spark jumping across the disks. With the neutralizers at 60 degrees the distance is 1/3 of the sum of the distances between pairs of sectors across an entire disk.
The problem with holes in the disks is that they may short-circuit the machine at the top and bottom quadrants. Not a big problem, since the voltage there is low.
Glues usually don't resist high voltage and are easily perforated by sparks. And they turn maintenance difficult.
Verify if the tubes used as insulators are stiff enough, since they will support the heavy terminals and the charge collectors, that may touch the disks if they are not solidly fixed in place. You can add arms (horizontal tubes or acrylic bars) fixing them to the frame too.

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Thu May 29 2014, 07:19PM



My issue is that the drillbit itself was bent, and thus drill oversized the hole.

I don't know anyone with a 48" (well, 24") lathe, but I do have a big routing table. That was going to be my plan too, but, I can't add material back.


Fantastic. I couldn't think of a way this wasn't true, but, I'm glad I reasoned it out myself.


Interesting... I may try that method. What is "softer" material to you? HDPE/PVC, wood, or much softer like foam or cardboard?


Yes, acrylic bars were my plan.

Thank you all again for all your help. I would be far more discouraged without everyone's guidance.

Re: Giant Wimshurst Machine - could use some guidance
Dr. Slack, Thu May 29 2014, 09:52PM

wrote ...
I place a spacer of soft material between the disks and bosses, to allow adjustments on the verticality of the disks with the pressure of the screws.

Interesting... I may try that method. What is "softer" material to you? HDPE/PVC, wood, or much softer like foam or cardboard?

Maybe something like rubber sheet, or perhaps a rubber tap washer at each screw, but don't have it too stiff and crack the acrylic torquing it down. Be careful that an adjustment like that may become un-adjusted with time and vibration, so you might want to think about using 'nylok' nuts, or assembling with thread-locker.

Can I just say Awesome that I'm most impressed with your progress. It's good to see someone putting their nuts on the line and getting on and building something, maybe I'm just a little bit jealous. Keep calm and crack on.

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Fri May 30 2014, 12:59AM


Not my problem for a while, it's a prototype that's being discarded.

Discarded... to me. Then I'll fix it up a bit better I hope, with help, and time.


Well, it makes it easy to work on projects when someone else is buying the materials. That's what prevents me from doing most of mine. Not the cost really, just, that the cost is a barrier to curiosity because if it doesn't work then I wasted money.

It also helps that their main shop guy quit and the other is overworked with the backlog and most of the rest of the build staff is out on vacation, so, I'm in demand :p

...

I'm making the charge collecting combs right now. I'm going with the wire comb style.

I do not understand this part of the machine, other than "it picks up charge." I don't get how.

Anyway, I took some 12g wire and wrapped it around a pipe once then straight pointed towards the disc. The bar is about 6" long and there are 5 such wires on each side of each comb. Then I soldered it all.

Will that work? Should I have more combs? I see some designs with like, an actual metal comb, dozens of wires. Others use serrated-cut foils. Should I have thinner wire? Should the wire tips be sharp, flat, or rounded?

I don't really get what does what and why it does that, so it's hard to solve it with intuition.



I will trim them to length later, obviously.

Re: Giant Wimshurst Machine - could use some guidance
Eleccentric, Fri May 30 2014, 08:37PM

Those charge collectors should work OK. I expect you will see leakage off the back sides where the wire wraps around, though. It would probably be better if you drilled holes into the pipe, inserted straight lengths of copper wire, and soldered around the hole. That way the sharp points are all on the inner side, facing the disks, where you want them. Don't change it for now, though. This should get you going.

The wire tips should be sharp. The wedge shape left by the wire cutters is sharp enough.

You know how we've made a big deal about large diameter conductors and smooth curves for your high voltage carriers? This is the one place where the reverse is desired. A sharp point will bleed off charge, whether it is actually attached to the charged object or placed near it, so long as there is a potential difference between the sharp point and the object from/to which charge is moving. The sharp point creates a high gradient in the electric field, triggering ionic conduction through the air.

A series of needles or finer wire might work better, but if you decide to remake this part later, you'll probably get the best results either from shielded serrated foil like in Homemade Lightning or else a pair of soft carbon anti-static brushes. It would be minor improvement in output, I expect, unless these charge collectors end up bleeding off a lot of charge. You will be able to see whether this occurs by examining the machine with dark-adjusted eyes.

I have no doubt that you'll be making sparks with this thing early next week. Your determination shows, you've got a solid basic design in progress, and you're not afraid to be honest about what you do and don't know. That last part alone puts you head and shoulders above most people.

Re: Giant Wimshurst Machine - could use some guidance
teravolt, Fri May 30 2014, 09:24PM

copper mesh, screen works good to

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Sat May 31 2014, 06:36AM


So, the comb vacuums up arcs and I should see them in the air? Or is it invisible, like static itself?

I only actually saw a Wimshurst for a couple minutes a few weeks ago before I started asking all these questions, and it had brushes so there wouldn't've been any arcs to observe.

...

Progress:

- Assenbled but didn't solder the combs and conductor structure.

- Assembled and soldered one neutralizer frame (needs brushes).

- Cut PVC handles for electrodes.

- Cut 1" copper bar electrodes.

- Reamed 2" of handle, free-hand, with a 1" drillbit so it would accomodate 1" copper pipe from the electrode.

- Jammed one handled together, it appears to work.

- Drilled out 2x 2" holes in 2x4 surface to mount the PVC supports.

- 2" was too loose, so I wrapped it with green masking tape and yellow duct tape as a cylindrical shim so it would be nice and snug.

- Drilled out both PVC pillar supports for output electrodes (pivot pillars) using NOT the 1" drill bit (shattered PVC and spat chips) but the 1" hole saw. Hurray for practice pieces.

- Drilled 21 mounting holes in each new piece of 1/2" plexi. (1) 3/4" axle. (4) 1/4" holes to mount to the pulley. (8) 7/32" inner holes to mount to the big discs, (8) 7/32" outer holes to mount to the big discs.

- Cut out the new 1/2" plexi shoulders.

- Drilled 21 mounting holes in each of the big wheels. (1) enlarged the axle hole from 1/2" to 3/4" (0.761 on the shopbot for whatever reason, took some experimenting). (4) 1/4" holes for pulley mounting, (8) 1/4" inner holes, (8) 1/4" outer holes. These were different than the sizes on the small discs because these are through-holes and the small discs get threads tapped. Between the 4 discs, it was 5.5 hours on the Shopbot with help. A couple near-disasters had us thankful we used test cuts first.

- Tapped 32 holes. Stopped about half way through to power tap them, since plexi is soft.

- Threw in 4 (metal, button head) screws per side to mount the disc pairs to the pulley.

- Threw in 16 (nylon, mix of button head and tapered since no place had enough) screws per side to hold the discs to each other.

- Drilled out a second set of large pulleys to 1/2". I think I will go with the 1-loop drive belt thing that Finn suggested ( <-- link), because I didn't have to make an understructure (like the one Antonio linked).

- Mounted it up and gave it a whirl.



... Hot damn. First disc was almost perfectly balanced, straight up and down, spun like a charm.
... Whoops. Disc #2 looks like a drunk on a unicycle. More tweaking needed.

Some people in the shop stopped by to oooh and ahhh.

- Tried and discarded using bungees as drive belts. Nylon is super slippery and they were too thin anyway. A couple alternatives to go buy tomorrow.

- Drew up a "To do" list and a shopping list. But of course, got to the reno store at 9:02, closed at 9. Went to a different one, crap for stock. More shopping tomorrow morning.


... I bought some realllllly thin threaded rod that I think I can use to hold the globes together and to the shaft. That was one of the remaining unknown assemblies, hopefully it works out. Also picked up some nylon hardware (all they had, again) so I'm not using 2.5" screws when I need 3/4".

Somewhat optimistic again. Seeing the discs together and holding up under very light rotation was a big motivator.

Also, found out a typical budget for a single exhibit like this, is $40,000-$80,000 from a fabrication shop (i.E. Not me, unless I get a solid bid in and figure out some insurance issues and partner up with someone who does better metalwork than I). So, I feel a little less bad about wasting $200 worth of acrylic the other day. I figured, $12-18k, not 3x that amount.

Re: Giant Wimshurst Machine - could use some guidance
RAJEEV TUTEJA, Sat May 31 2014, 11:29AM

dear AwesomeMatt

we are making almost the same machine except that yours is 48" and mine is 36".
for the belt i have a suggestion if you like.
i bought some mixed nylon polypropylene and what not endless belt stuff from a sewing machines dealer which can be cut to whatever length you want and then just heat up the ends and join them.
and believe me even if you are a WWF champion you won't be able to split apart that joint and they are available in different thicknesses. And another plus point of the belt is if you cross them for the other disk the problem that many face of belt dust is almost eliminated (WELL UPTO 90% IN MY CASE At LEAST)
hope this helps
regards and best wishes
p.s. want photos i can post them if you like or a video ?

ohh i forgot to tell you that the belt is meant for motorised sewing machines which are set on a table with electric motor and a foot switch to contorl its speed
rajeev tuteja

Re: Giant Wimshurst Machine - could use some guidance
Eleccentric, Sat May 31 2014, 07:10PM

Looks like you'll need double pulleys or dual-groove pulleys for Finn's suggested belt drive.


It will be visible, but only in deep darkness with dark-adjusted eyes. Not arcs, but soft corona discharge. I differentiate between arcs, sparks, and corona. A spark is what the output of this machine creates - bright, sharp, a single defined path. An arc is a continuous discharge that will wave and ripple with convection. Corona discharge is a lower current phenomenon, soft and diffuse, typically covering a volume of space and can often be touched without harm to your skin. It also can be called a non-thermal or non-equilibrium plasma.

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Sun Jun 01 2014, 08:55AM

This post is useless without pics. But, too busy. Just pasting my log for the day's work.

Progress:

- Fastenal closed. Industrial supply place closed. Ability Medical, was open, closed at 2pm. Auto Parts source had no oring cord, bought washer fluid hose instead for drive belt. Hopefully works, nothing else is open until Monday. Also bought superglue and 1 min epoxy to join hose.
- Rona: caps for 2" support post PVC, 3/4" nylon screws, rubber washers, 1/2" PVC, T-nuts (for Homemade Lightning ball joining suggestion).
- Yesterday's threaded rod far too small, holes in globes are bigger than I thought. Need to shop for larger tomorrow, brought globe home with me.
- Drilled out electrode handle PVC, cut 1" copper to fit, cut copper nipple to joint pieces. Electrode bars are done.
- Cut & straightened wire for combs, new design.
- Took down & disassembled disc assembly. Discovered chipped acrylic. Designed semi-squishy/compressible gasket (bubblefoam), cut and applied.



- Peeled backing from half of discs.
- Reassembled wheel #1 using proper nylon screws. Wheel #1 still spins great! Looks great! Hurray!
- Reassembled wheel #2. Wheel #2 still wobbles like a drunk, even worse than before.
- Disassembled wheel #2, tweaked bolt tightness to compensate for wobble.
- Reassembled wheel #2. No effect.
- Disassembled wheel #2. Problem might be with bushing seat. Disassembled pulley using 20 ton press, reset bushing in pulley extra deep. Set bushing in acrylic.
- Reassemble wheel #2. Wobble is okay except for 1/4 of rotation, has a 3/8" wobble. Attempted adjusting, no effect. Wobble is 3/4 fine, 1/4 to outside, so, probably useable as-is. Wheel is centered well.
- Designed, measured, cut, sanded template for sectors. Template was 2" wide, 2" aluminum tape is actually 1 3/4" wide not 2". Super. Re-engineer all the measurements, now will have 50 sectors per disc (even 100 total), measured, cut sanded new template.
- Carefully traced out 120 sectors on aluminum tape (extras for ones that get ruined while peeling backing).
- Very slowly and carefully cut out 120 sectors of aluminum tape. Everything smooth, no jagged edges. Did not think sectors would take 8 hours from start to finish, and they're not even peeled or applied yet.

Didn't get an answer for whether the machine needs to be done beginning of Monday or end, but was told the person working on the proposal would not be there Monday, so... Tuesday morning it is?

Re: Giant Wimshurst Machine - could use some guidance
Eleccentric, Sun Jun 01 2014, 06:40PM

If you need to ease the time crunch, you can apply a fraction of the sectors and still have a functional machine. Leave out every other or every two sectors, making sure that they line up from one disc to the other. The charging current will be lower, but the voltage should be nearly the same; you'll get sparks the same length, but less frequently for the same number of disc turns.

The wobble sounds negligible - one disc width's worth has not been a problem for the machines I've built, though none have been nearly this large.

When assembling the belt, I suggest that you find a short length of rubber tube that fits snugly inside the hose. Lube it with 90-99% rubbing alcohol and shove as much into one end of the hose as you can, then trim the exposed end to a similar length, lube it similarly, apply your glue of choice, and shove on the other end of the hose. The alcohol will evaporate and the rubber should friction-bind, adding significant strength to the joint. Slicing the hose at an angle for the butt-joint is also a good idea, so the glue has a larger surface area to work on. This is not unlike the gluing method shown in Homemade Lightning for Van de Graaff belts.

If the glue doesn't hold, and if the hose you are using is fiber-reinforced, you could stitch the joint together with nylon thread, as well. I believe I've seen this done on old leather belts for treadle-powered sewing machines.

Assemble the neutralizers before the high voltage collectors and discharge arms. The machine will charge and you will be able to draw sparks off the areas where the collector combs will sit when finished.

Re: Giant Wimshurst Machine - could use some guidance
Newton Brawn, Mon Jun 02 2014, 05:23AM

Hi Rajeev,

How do you assemble de acrilic disk with the wood pulley?

Are you going to use bolts, steel bolts?

The distance of a bolt to the center of the shaft in disk A may have a different distance of a bolt to the center of the shaft in disk B in order to avoid the bolts crash.

If you have videos, I will happy to watch.



AwesomeMatt

The wobble is something annoying.

The first idea I have was assemble a secong bushing in each pulley, assemble the shaft/pulley in a lathe. Then the lathe can face the surface that is in contact with the acrilic disk..

Othewise, a 0.5 mm thick chim applied between the disk and pulley may correct the wobbling. A 40mm long masking tape can solve the problem .


Regards

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Mon Jun 02 2014, 10:12AM


Well, won't be done *before* Monday, might not be done on Monday either.

Lots of video, no pics though, ran out of the building at the last minute before lockdown.

Progress for today:

- Shopped at Princess: 2x 3" sheaves, 5/8" bushings, 5/8" bolts, 5/8" washers
- Shopped at Lowes: 4x 10-32 threaded rods (replacements), small washers
- Disassembled disc, upper axle, lower drive assembly, frame, platform. Nothing left together.
- Migraine arrives, perfect timing.
- Chopped up frame cross bracing to new sizes. Reassembled frame. Is lower, will not short discs anymore.
- Reassembled platform, new spacing, 285mm separation inside frame. Should avoid other shorting issues.
- Drilled out new double-pulleys to match their twins.
- Used hydraulic press to disassemble jammed-on pillow block bearings from lower axle.
- Reassembled pulley triple-stacks, while trying to straighten crooked pulleys with holes that wouldn't line up until they were pulled straight by the bolts. Took forever. Stripped several bolts, used longer ones with plain nuts, hacksawed off excess threads (needs to fit closely), unthreaded nuts to autocorrect bolt threads, re-threaded with delicate but anti-vibration nylon nuts,
- Reassembled, adjusted, re-mounted lower drive assembly. One pulley was so deformed the other 2 couldn't straighten it, just averaged it out. Ugly but should be functional.
- Realized when I reassembled the frame & platform, I didn't square or center any of it. Discs will tear apart if not straight. Disassembled all of it, squared it, reassembled all of it. Migraines are exciting.
- Measured & cut upper axle PVC spacers.
- Lifted Disc #1 to final position, with PVC & Nylon spacers.
- Lifted Disc #2 to final position, with spacers. Exhausting trying to lift, and reach to the far side of, 150 pounds worth of acrylic that I can't see around, on a shaft that keeps sliding out of the way, when nothing can get scratched. Will be doing this at least once more, not alone next time.
- Figured out distance spacing for flat pulleys (the 3"), also calibrated height.
- Sourced and chopped material for pulley mounts.
- Drilled & mounted both pulley mounts onto lower frame.
- Skeptical of washer hose as a belt. Skeptical of charge rate. Skeptical of pulley ratios. May go buy oring cord or something more substantial tomorrow since everything's open again. Calculated edge speed of counter-rotating discs, 48" in diameter moving 2 handle cranks a second at 12:1 ratio, to be exactly 666 km/hr. That's as fast as a jet airplane. It's either crazy, or wrong. Now is not the best time for me to confirm that.

If I get a belt on it... it's ready to twirl and dance.

Then I need to take it apart and put the sectors on it.

And finish all the actual electrical stuff.

With setbacks, probably a full day behind, maybe 2.

Am putting like, 14+ hour days into it. Slow going but not much I can do about it, already throwing all my time into it.

Re: Giant Wimshurst Machine - could use some guidance
Eleccentric, Tue Jun 03 2014, 03:04AM

I don't think you did your kph calculation quite right. I work it out to be about 205 mph, or about half your stated speed. This is still much too fast.

I think you need a lower pulley ratio, or else cranking this thing will be very difficult once it charges.

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Tue Jun 03 2014, 03:15AM

I just tried running a belt to hook up this mechanism that avoids crossed belts.




(Courtesy of Finn).

... I'm an idiot. Clearly, one of the giant pulley pairs has to be slipping. They can't *both* be locked onto the shaft.

FFFFFFFUUUUUUUUUUUU...

Need to be drilled out and a bushing put in on one of them. The plastic wheels are super grippy even if I loosen the set screw.

Bonus though... I don't need to disassemble the machine to put the belt on. I can make it and then install it after. I think...



HOLY SHIT.

I spun it up to speed and it didn't detonate on me.

No sectors, no neutralizers, no combs, no Leyden jars, but, it sort of actually mechanically works!




Argggggg....

Well they pulley ratio was the one thing I didn't bother to do myself. It was spec'd to me. I should have just thought about it and picked my own.

All this trouble with the stupid mounting of the 1" pulley... if I would have gone with, say, a 4" pulley I would have had lots of room to bolt to, no scary torque issues, no balancing issues. Hrmph.

...

Balls went together easier than expected. Just tapped the holes and screwed them onto threaded rod.



I think they need a spacer between the balls. I was thinking, just a 1/2" or so chunk of 1/2" copper pipe, sandwiched in there, and hopefully no need to solder and such?

Right now the end of the 1" copper pipe has a flat end, that's what I'm screwing into. Would it be better to have the ball meet the copper pipe flush, without the flat? I can hammer in a chunk of wood with a nut bashed into the far side, and just screw the ball directly until it's touching the pipe edge.


Also, here's it's first spin. (It wobbles because the table it's on is a rolling worktable and I'm leaning into and out of it, not because the machine wobbles).





Today's progress:

- Tried to buy carbon fiber brushes. Record cleaning brushes may be carbon fiber? Store #1 has nylon only, Store #2 is closed Mondays, Store #3 won't pick up a phone.
- Tried to buy Oring cord. NAPA says they special order from Gregg's. Gregg's Distributors doesn't know what that is, Hitech seals has some but won't get there in rush hour before they close.
- Noted frame was leaning, cut support blocks and secured. Output braces later should help.
- Adjusted lower assembly to center.



- Drilled out flat pulley mounting holes.
- Mounted flat pullies
- Experimented with belt paths.
- Realized one triple-stack pulley will have to be freewheeling on axle, obviously, can't have both going the same direction. Lots of friction from plastic pulleys, need to drill out and add bearing, later.
- Shuffled one flat pulley for necessary offset.
- Measured, cut, superglued belt.
- Realized belt was tied in a knot, ripped apart, reglued. Wrapped with scotch tape to make smooth.
- Realized upper and lower drive assembly requires disassembly to change belt, unless flat pulleys are inside-outside rather than staggered. Requires a larger pulley on one side later.
- Belted up machine. Seam held up!
- Gave machine test spin. It actually worked. Seam gets caught in pulley grooves, no big deal. Slips under startup and is ridiculously tough to turn, takes a couple minutes to reach speed and had me sweating. Whatever, it works!
- Test drilled conb pipe with microbit, seems to work.
- Drilled out output support pipes to accomodate comb mount. No drill size close enough, manually reamed.
- Attempted to tap output globes. $25,000 Shopbot? Check. $10,000 lasercutter? Check. 8 fancy dust collecting systems plumbed to every cutting tool? Check. 3 welders, mill, lathe, tooling? Check. $5000 in nut and bolt hardware? Check. $15 tap set? Not in the budget. Just a few misc pieces. Super. Made one work, tapped small globe, threaded, seems to work minimally but sufficiently. Tapped both ends of a large globe, wonky but works.
- Need to drill out copper endcap for threading. Drillbit smaller than 7/32"? Nope. Super. Hammer and reaming.
- One output electrode done. Done-ish. Needs some tubing spacers. Good enough for now.
- Cut pipe for temporary neutralizer mounts. Works okay.
- Mocked up assembly, made notes of what might cause issues.



Issues:

1 - I kind of ignored where and how to mount the neutralizer brushes. I will probably cut that axle short, but even then, they stick out pretty far. They're close to the output electrodes. That'll be an issue, no?

Maybe shove them where the PVC sleeves are.

2 - Comb pipes aren't long enough. No matter, was just the leftover chunk, will cut more.

3 - Intended to cut acrylic supports to hold output posts steady to center post. Neutralizer brushes are in the way.

4 - Discs are a little far apart. Oh well. Could trim the spacer, but, I'd rather just charge the machine slowly but *not* have a catastrophic crash.

Won't make the deadline tomorrow don't think. Have other commitments.

Re: Giant Wimshurst Machine - could use some guidance
RAJEEV TUTEJA, Tue Jun 03 2014, 05:44PM

dear Newton Brawn

sorry for the late reply.
i used 4 flathead screws to bolt wooden 12" 5 mm disk to 36" acrylic and the wooden pulley in that order.
for spaces between the disks i used thruster bearings with teflon sheet cut to bearing size to avoid any friction between them and the sheets.
hope this helps.

regarding pulley ratio mine is 3/7 i:e 3" wooden in the center with 7" driving pulleys

Re: Giant Wimshurst Machine - could use some guidance
Dr. Slack, Tue Jun 03 2014, 09:50PM

- Measured, cut, superglued belt.
- Realized belt was tied in a knot, ripped apart, reglued.

- Attempted to tap output globes. $25,000 Shopbot? Check. $10,000 lasercutter? Check. 8 fancy dust collecting systems plumbed to every cutting tool? Check. 3 welders, mill, lathe, tooling? Check. $5000 in nut and bolt hardware? Check. $15 tap set? Not in the budget.

Oh, I feel your pain.

Hang on in there, you're doing a great job.

Re: Giant Wimshurst Machine - could use some guidance
Ash Small, Tue Jun 03 2014, 10:12PM


I'd probably drill and tap the hole in the centre, then solder on a short 'stub', or something, if I was pushed for time.

(Use the ball to hold the stub in place while you solder it)

Re: Giant Wimshurst Machine - could use some guidance
Eleccentric, Wed Jun 04 2014, 01:59AM

Note the pulley ratio on the largest Wimshurt ever constructed:

You can also see that the neutralizer arms are much shorter than yours. They don't have to extend to the edges of the discs; they just have to touch the sectors. When it comes to carbon fiber brushes, if you can't find a junk printer to cannibalize, you can probably use carbon fiber tow. Google the phrase "carbon fiber tow" and you will find various cheap sources, including ebay, for soft carbon fiber cordage, string, rope, etc.

You are going to have a lot of problems with those tiny pulleys. I expect a lot of belt slip and wasted cranking effort, once the machine puts a mechanical load on the discs from coulomb forces.

Re: Giant Wimshurst Machine - could use some guidance
Ash Small, Wed Jun 04 2014, 11:13AM


I would have commented on this earlier, but I must have mis-read something about only needing the smaller pulleys to mount the larger ones.

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Wed Jun 04 2014, 07:56PM


Wrong set of pulleys. The lower drive assembly has these big black 12" (...) plastic pulleys that have no way of locking onto the shaft. So I used 6" pulleys that I bought earlier to just bolt right through into them and hold them to the shaft.

...

Took most of yesterday off.

Progress:

- Marked out disc. 47.75" * 3.1415 = 150.00" circumference. 50 sectors means 3" each exactly!


(Anyone need some robotic pantyliners?)

- Oops. Not exactly. Shopbot was dead-on for disc size, but the very last mark revealed the width of the tape measure and other errors added up to 3/4" by the end (0.015" per sector). Measurement > Math. Thankfully didn't start adding sectors yet.
- Measured the circumference, made list of fractional measurements.
- Started converting decimal to nearest fractional inch.
- Metric > Imperial, stopped after about 5 stupid fractions and used mm instead. 3793mm, 75.86mm/sector. Printed out the table for reference.
- Marked out disc.
- Designed & cut sector layout template. A wedge shape I can guide the sectors to, depth and alignment-wise.


(Pew pew!)


(Left edge sits around shoulder disc, angled lines line me up, hole cutouts give me room to my fingers low and out of the way. Also visible is the old 2" template and the new thinner template)

- Tested soapy water method (gives time to adjust before stickiness grips). Doesn't work well with curled pieces. Better to just get it perfect and stay put.
- Started adding sectors, template works great, slow work, but compelted half a disc and they look perfect.



Starting to look like a real Wimshurst!

Re: Giant Wimshurst Machine - could use some guidance
Eleccentric, Wed Jun 04 2014, 10:29PM

Another thought on neutralizer brush material. You nay be able to use metalized mylar foil. This is used to make shiny decorative balloons as well as christmas tinsel. It is fairly conductive at these voltages, and having high resistance in series with the neutralizers really doesn't matter as the capacitance of the sectors is so small.

Another thing to consider would be solder wick - it is comprised of a bunch of extremely thin and soft bare copper wire.

Both of these suggestions lack the springiness of the carbon fiber tow or antistatic brushes. They might work in a pinch, however.

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Thu Jun 05 2014, 09:41AM


I think I have neutralizer brushes covered. Brass shim stock. Not as good as phosphor bronze, but, they'll do I hope.



The little tabletop version uses solder wick for both neutralizers and combs. It's kinda finicky and crappy.

Solder wick is designed to be as soft as possible. It's not too difficult to work-harden copper, but, in braid form it'd probably just crumble.

I kinda gave up on finding carbon fiber combs and started making copper combs out of fine wire. If that fails, I'll just make contact with more brass shim stock and to hell with it.



Found out they already sent off the request for bids on the finished version, with a note saying they might cancel if it doesn't work out. So, I think that means people are more or less confident I can make this work, they just need to know whether it has the OOMPH when they actually see it work in the gallery. No mention of the deadline, other than not to slack off.

Visually, kind of an unproductive day. A lot of trial and error and figuring and not a lot of doing.

- Completed sector placement on second half of Disc #1.
- Measured and marked sector layout for Disc #2.
- Designed Leyden jars out of 4" PVC.
- Cut and test assembled Leyden jars. 42" tall, 18" gap at top required, leaves 24" of foil space.


(Combs are pivoted out of the way, you'll see why in a second).
(Note the 4" PVC tube with square endcap, that's one of the to-be Leyden bazookas).

- Designed output post stabalizers.
- Drilled 2/4 combs with microbits, tested various soldering options. More stubborn than expected, but got them working.
- Designed comb framework, works but wheel frame is crooked, will integrate into post stabalizers. Need more copper pipe.
- Cut one comb and trimmed tines, ugly but should work. Backup plan is contact brushes or carbon fiber again.


(Yep, it's missing a few tines on the left. They didn't survive the blowtorch).

I dunno if that's stupid or not, I like the idea of combs but, they're a pain in the ass to work with and now that they've been torched they're dead soft. Definitely not contact brushes.

- Cut free and threaded second pair of gazing globes.
- Designed new neutralizers, narrow them away from the electrodes.
- Designed how everything will work together, how to mount and assemble all the assemblies, what to upgrade/change if any of it causes problems.
- Wrote shopping list for tomorrow: More 1/2" copper pipe, 4" pulley, more 2" PVC, 3x 2" PVC "T" pieces, proper O-ring cord (almost tore a hose today), 2" PVC end cap to mount to the frame.

Oh, and Leyden jar questions:

1, When making the Leyden jars.. I need a sparkgap's length at the top (18" sparkgap = 18" of deadspace at the top of the jar), I think?

2. Is that both inside and outside? Or could I run the inside right to the lip, and the outside only part way up? Any point in doing that?

3. I'm just PVC gluing a bottom cap on the jar. Will that work for insulation? Or should I also not wrap foil for a few inches?

On the home stretch!

Re: Giant Wimshurst Machine - could use some guidance
Ash Small, Thu Jun 05 2014, 10:48AM

The Leyden jars will only have capacitance where there is foil both inside and outside. Assuming you have a conductor going inside at the top, you'll need AT LEAST 18" gap on the outside, assuming the conductors aren't insulated.. Leave some space at the bottom. If the PVC glue isn't sufficient, you could always put some oil at the bottom inside for additional insulation if required.

Re: Giant Wimshurst Machine - could use some guidance
Eleccentric, Thu Jun 05 2014, 07:37PM

I would be wary of trusting the PVC glue to be as electrically solid as the pipe wall itself. You've got so much surface area to work with, though, that leaving foil off the bottom should not be an issue.

The problem with using brass shim stock for the neutralizers is that they may be harder than the aluminum. The hardness of brass and aluminum alloys are largely overlapping, so it's hard to say whether they will wear scratches into your sectors or not.

Carbon fiber tow is cheap and readily available. You ought not to have much trouble making brushes from it.

If you want the tines on your combs to be hard, temper them. Don't let the assembly cool slowly - quench it with cold water.

You could likely get away with securing them in place with epoxy - just make sure that the wire makes contact on the inside of the pipe. You could mix in some metal powder to help make sure there is good electrical contact, but again, at these voltages, it's not so critical.

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Thu Jun 05 2014, 08:19PM



Oh, it's certainly harder than the dead soft aluminum tape.

I don't really care much. I want it working well enough to demo, and if they want more time put into it I'll swap it out for carbon fiber.


I looked around for a place locally that had it, big city, couldn't find anything. Not sure what kind of place I'd be shopping from though.


JBweld, a metal epoxy even, is an insulator. Mixing metal shavings in doesn't help.

But, yeah, I may end up doing that.

Lots of mediocre solutions, all of which are finicky.

Re: Giant Wimshurst Machine - could use some guidance
Ash Small, Thu Jun 05 2014, 08:41PM

The vast majority of ignition cables for cars, etc. have a carbon fibre core. You might even get some for free.

Another source is a rope called 'Dyneema'. There are several different sorts, but the really high tech stuff has a carbpn fibre core (I'd go for this over the ignition cable, but both should be ok), it's sold in 'yacht chandlers' and marinas and boatyards, if you have any near you.

It's pretty straightforward stripping the insulation off the ign. cable. I've not tried stripping the outer layer off the Dyneema, though.

Re: Giant Wimshurst Machine - could use some guidance
Eleccentric, Thu Jun 05 2014, 10:08PM



Bear in mind that we are working with a voltage that will leap the gap between the sectors and the tines of your combs - the "insulating" properties of epoxy will do very little to impede the charge from transferring onto the copper pipes, especially if you let the wires extend into the pipe far enough that they touch the inner surface.

Ash Small's suggestion of using the core material from spark plug wires is excellent - I wish I had thought of that. Free or inexpensive, and should be much easier to find locally than raw carbon fiber tow. You could attach the fiber to the copper pipe with some of your aluminum tape.

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Fri Jun 06 2014, 06:44AM

Well... last Thursday I said I was going to try to pull an all-nighter to get it done by Friday. It was discouraged as unsafe.

They asked when I would get it done. I said I didn't know because nothing was being used for its intended purpose, everything part was an experiment and it might be the first idea that worked, or it might be the 5th idea. They wanted more info, so I talked them through it, working my way back:

- It would certainly be done in a month.
- It would almost certainly be done in 2 weeks.
- It would probably be done by next Friday.
- It would maybe get done by Monday/Tuesday.
- It would probably not get done by tomorrow night and if it did, all corners would be cut to do it.

And they were like "So, it'll be done Monday?" ... Uhhh... Let me just repeat this again. :p

That was a week ago. The machine that should be done tomorrow is a lot better than the one that would've been rushed for Monday,

But... I'm going to pull an all-nighter just to be sure. I get locked into the building for the night if I choose to stay, so, bunkering down time.

Progress as of 10pm:

- Swapped out 3" sheave for 4" pulley on left side, for flat pulleys. Outside bands are 1" wider than inside bands.
- Squared up the last bit of frame. Measured the horizontal and the vertical, did some trigonometry, cut a cross-brace, fits perfectly. And perfectly level! Do your homework kids, some day you may use it!
- Trimmed output supports, inserted T-pieces.
- Added beam between output supports, with T-piece to connect to main frame.
- Placed the pair of combs I have completed. Well look at that, they're dead-centered on the wheel, no adjusting necessary.
- Placed 50 sectors on Disc #2. Disc #2 is complete!



(Extra wooden brace & PVC framework to keep everything properly spaced).



(Note where horizontal PVC bolts to vertical wood... the end cap is bolted but rotatable. This way I can twist or untwist the end cap and vary the lineup of the combs. Planned on being crooked, turns out when everything is square, the measurements were spot on).



Combs. Maybe 1/4" to 1/2" space between disc and comb tips. Hope that's close enough, it wobbles. If it doesn't work, brushes will quickly replace it.

I spin it and it looks like a Wimshurst machine. Hurray!

To Do:

- 2 more combs & arm
- Figure out how to mount neutralizer brushes
- Make and mount neutralizer brushes.
- Mount output electrodes.
- Add pair of globes to electrode #2.
- Turn PVC assembly into Leyden jars.

... wow, I think that's it. I was expecting a longer list.

The better way to mount the neutralizer brushes is inside the frame, next to the discs, where the PVC spacer is right now. But the discs weight 100+ pounds each, the axle is 7' (213cm) off the ground, and jammed on. I'm alone for the night, so, they're staying unless I have help holding the axle.

Instead, I will mount them on the extra axle that is sticking outside of the frame, secure them with masking tape or rubber bands, and not care because I'll be distracted by how awesome the sparks are.


First up: Globes and Leyden jars

Updates as I do stuff.



2am (last one was actually around 1am, took a lunchbreak first and wandered around trying to find something open).

- Globes are done, mounted to electrode #2.





Did a bunch of research on Leyden jars, or tried to. No one really makes them this big. Or if they do, they don't give a lot of details. Should I be wrapping axially or lengthwise, how critical is smoothness, how insulatative is silicone or PVC glue, how thick does the foil have to be to not vaporize under the sudden current spike during the discharge, etc.

I read 40MV/meter for a dielectric constant. This PVC is only 4mm thick. That means it's only good for up to 160,000V. I'm maybe below that, maybe not.

Is the voltage potential of the machine that I have to worry about, split between the two Leyden jars? That is... if I have 300,000V being generated in the machine, am I okay? (160kv + 160kv = 320,000v > 300,000v).

I know I could build 4 leyden jars and put them in series, but, I don't really have anywhere else to put them except in the way of the visitor and the electrode pole handles.

Moot anyways, I covered both insides but only 1 outside before I ran out of aluminum tape. Added it to my shopping list for tomorrow... err... when stores open in a few hours.

Shattered an end cap anyways when one fell over. so, was off to the hardware store again anyway before they were done.

Next up... neutralizer brushes and bars I guess. Something way overdue for verifying the other parts of the machine.



7am.

Neutralizer bars... ehn. Sort of done. Wobbley-loose (will shim with tape for now) and missing the brushes. Problem is I know they're not staying this way, so I'm not sure I should finalize them any more. Right now they're just press-fit copper, not soldered.

Tried to rip protective backing off the discs... I of course can't reach that deep between the wheels. Which means I have to take them off. Which means I need 1 or 2 more people to help. Which means, I might as well mount the neutralizer bars where they belong and stop half-assing it.

But I really really really want to see the thing power up before I go calling for help.

Dawn has arrived.






Compromise. Soldered some of the neutralizer's first joints that won't change, gave them a longer "bushing" (chunk of pipe).

Really don't feel like making a second set of combs. So I won't. Rather than drill the pipe, insert wires, solder it up... I'll just wrap aluminum tape around the pipe and sandwich a dozen wires in the process.

Brush material is getting assembled the same way if I can get away with it. I'll soon find out.



Ugh. Was feeling confident, then a pile of related problems.

- Brushes are too hard, scraping the sectors and the disc.

- Brushes need to be springy to keep the ghetto neutralizer bars balanced. The neutralizer bar assembly is awful and wobbly and there's no way to anchor it easily. They have nothing for a collar, and aren't pinned to the axle (right now rubberbanded to the frame so they don't spin like a clock).



- Bars are actually enough leverage to prevent the wheel from turning and start the belts slipping.

- Pulleys need to be revamped. Maybe can't be, because they're using a 1" pulley up top and might not have enough friction even if I drop the lower one to, say, 6:1 instead of 12:1. Ugh.

Kind of natural, to see all the problems show up on the very last stage of test assembly. Just discouraging and... I had the physical fortitude to persevere until it was done because I thought there were no more design obstacles, only just work to do.

Morning of an all nighter is not the time to tinker or troubleshoot or come up with ideas.

Argg.

Odds of having something demo-able today went from like 85% to like 5%.

Re: Giant Wimshurst Machine - could use some guidance
Dr. Slack, Fri Jun 06 2014, 04:25PM

A few tips, the neutraliser bars are at ground potential, which may offer you more options for mounting them.

The neutraliser brushes don't need to carry amps, if you replace that meaty strip with a wisp of copper wire, they will still work electrically, and won't offer the disc as much friction. Copper takes a set, so maybe use a sliver of plastic to support it. A piece of thick copper wire could be hinged from the neutraliser bar and sprung lightly against the disc with a small spring or elastic band, there are endless low-friction alternatives.

The main problem with your gear ratio is not the big pulley at the bottom, but the small one at the top. What options do you have to increase this? If the discs are coming off at some time, then a replacement could be scheduled in.

If not, can you buy a couple of 4" or 6" pulleys, cut them in half, remove an appropriate sized semicircle from each half, and assemble them round the existing tiny pulley, maybe with glue, maybe with fish plates or even stitching between the two halves? With stretchy belts, these pulleys do not have to be exactly concentric. It will look ugly, but may fix your immediate demo, and schedule in the proper replacement before any public see it.

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Fri Jun 06 2014, 05:04PM


Ugh, I know. It was the very first thing I bought (based on Mr. Teslonian's claim of 14.3:1 being feasible) and everything else is based around it. Pulleys that size are only 1/2", so the axle (that is now bowing under 300 pounds of weight) is 1/2". The 48" discs have all of 1.5" of boss and torque arm. The belt has only the 1" pulley circumference to grip onto, etc etc.

Almost every issue can be traced back to that first step.

And, I've almost no opportunity to change it. I suggested it an hour ago as a "What I really should do is..." and was given cringefaces and "How about we don't do that yet..."s. I kinda agree. It would be a lot of jig work to get it re-cut to a different size, and the guy who runs the Shopbot isn't in until next week.

Perfect storm.

I may try your pulley dicing trick, but what I'm afraid of is overtorquing the discs.. it won't change the fact that they're not bolted to the discs except at that 1.5" region which may shatter under more torque.

Copper/plastic combo is another idea I'll add to the list of things to try.

Threw in the towel around noon.

Found more aluminum tape though, so, finished the taping of the Leyden jars inside and out:




Went shopping:

- New endcaps for the Leyden jar to replace the ones that shattered
- Found a nice gentleman that repairs copiers who gave me some carbon fiber brushes (they're only 1/4" long sadly, my wobble is worse than that so... probably won't work :( ),
- Some proper Oring cord ($4.37/foot... $100 later...) and I'm not even sure it will work because it's pretty stretchy itself.
- Two more 6" pulleys (previous 2 I only ever used as a collar for the black 12" pulleys), so now I have 4 total and can use them as my lower drive pulleys.

...

I don't think any first idea has worked. I was making a mental list of the parts and assemblies today, and everything is already on v2 or v3. Naturally, the parts that are still original are the places things are going wrong.

I guess I spend another weekend at it and try for Monday.

Found out that they'll probably go with a flexible quote from the fab shop, so, it's not just "It works? Okay, throw it away, we'll build our own now." Any details I figure out in terms of size or material or construction, all save them money on the bill. So, that's less demoralizing at least.

Re: Giant Wimshurst Machine - could use some guidance
Wastrel, Sat Jun 07 2014, 05:24PM

Do you have an estimation of how fast the discs can rotate before they are an explosion risk? Do you have an estimation of how fast a thirteen year old boy with attention deficit disorder can turn a hand crank?

How close to this sort of spark can a digital watch get and survive? Will the device need a faraday cage?

Awesome and cool btw.

Re: Giant Wimshurst Machine - could use some guidance
Hazmatt_(The Underdog), Sat Jun 07 2014, 06:01PM

I think you're going to need to test your PVC capacitors. They're probably very very leaky.

If you can find a large 1 or 2L beaker and turn those into Leyden jars, you would probably be better off.

But test the PVC ones, or better yet, get some doorknob caps, they would be a slam dunk. You would probably need 4 of them rated at 50KVDC, because when this think works, it's going to throw a big spark.

Static dissipation is your biggest enemy on these things. Wood, plastic, paper, glues... you want to have all of your resistances very very high, higher then 10M Ohms.

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Sat Jun 07 2014, 08:00PM


Nope. Sounds like a problem for an engineer.


13 year old? Bah.

They regularly host "Adult's Night" where they open the bar, everyone gets drunk and makes stuff and plays with the exhibits. And by "plays" I mean "tries to set records on how fast/high/far/extreme/etc they can get the exhibits to perform."

Do I have any idea how fast a team of drunken college boys can spin it?

Well, I invested several years of research into the matter one upon a time, for science...

*This* version won't be an issue. It won't be touched by the public, and the pulleys will slip rather than accellerate.


I remember back in high school, a Van Der Graff generator reset my watch date & time to zeros.

The enclosure is specifically not my problem, some higher ups have already decided it doesn't need a cage or enclosure, just a rail. They've not been swayed by my opinion so, they can deal with that.

...


Part of the purpose of me building this, is to experiment with capacitance values to discover the sweet spots between the following variables:

1. Energy of spark (bigger is better)
2. Loudness (as big as possible without causing hearing damage)
3. Timing (5-15 seconds between sparks for an average visitor)

Experimenting is taking the largest Leyden jars and gradually taking a razor blade the outer foil on the leyden jars and peeling it off.

For what they'll be spending on it, I think I will just suggest they purchase a pair of capacitors custom-made from a shop. But I need to find them a value or a range first.

Re: Giant Wimshurst Machine - could use some guidance
Eleccentric, Sat Jun 07 2014, 09:17PM

The voltage strength of PVC is highly variable. If this design doesn't work out, I see you have a number of 5 gallon buckets sitting around - which are made from a much more suitable material: polypropylene. Here's an image of a smaller machine creating a very nice spark for its size using 5 gallon buckets as Leyden jars:

You would be covering a much smaller area of the buckets, so perhaps two or more on each side would work better.

You are correct in your thinking that the voltage will be shared between the two Leyden jars equally. You don't need to worry about the foil ablating or vaporizing from the current under normal use. If you were to draw a spark directly off the foil, though, that would increase the current density at the point of the spark sufficiently to vaporize a tiny bit of the metal.

I decided to investigate the possibility of using carbon-fiber core spark plug wires as a source of brush material, and am disappointed. The one I cut open and played around with appears to be made from nonconductive fibers impregnated with carbon powder. This is totally unsuitable, as the powder would stick to the discs and eventually short out the sectors. I washed a section of the fibers and they eventually turned white. The resistance of the same bundle went from about about 5k to 5Meg after after washing

Re: Giant Wimshurst Machine - could use some guidance
Ash Small, Sat Jun 07 2014, 10:27PM


Thanks for checking this, Eleccentric. I did experiment with home made resistors a decade or so ago, and tried this then, but I did notice it didn't 'feel' like carbon fibre, and some of the black came off on my fingers (It did make good resistors, though).

Maybe Patrick has some carbon fibre offcuts he could post to Matt?


I PM'd Patrick and he replied "i have a shit load... 1x3, 2x4, cloth, uni-directional, just a shit load."

PM him, and he'll post you some.

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Sun Jun 08 2014, 01:16AM


They were on sale for $1. I bought 8 of them just in case they'd come in handy for this.

I don't have lids for them though. I could probably go buy some. Or whatever... I've spent probably $1200 in materials so far, $4/bucket is trivial.

They're only 13" tall though. So, no way for me to get 18" of separation (the mouth of the bucket is ~11", so, I could steal 5 inches to center, leaving 13" of gap down the outside.. I'd get just the bottom plate covered. Better than zero I suppose.

The PPE is very thin though. Very very thin.

What I've been thinking of doing for a week now, as my backup plan, is stacking one bucket inside another, to double up the insulation and add some airgap too... but I thought I might lose almost all my capacitance that way (plates too far apart).

Ordering thicker acrylic or PVC is also an option.

I really want to try the garbage can idea you or whoever came up with. Just to create some comically maniacal thunder. Break some windows maybe :p

On a related note, I bought a decibel meter last year. I imagined using it at a party to confirm to police that in fact, the music was *not* too loud. Instead, I will use it for science!


Neat, except, I don't have time to wait for things to arrive. Everything is go go go. 1/2 the stuff I've been buying and trying for all kinds of parts on the Wimshurst is in the mindset of "I need to make *some* progress today" or "I need to do whatever might get it done today/tomorrow." This where I'm clearly trying a worse solution when I already know the better one.

Budget isn't an issue really. I paid $100 for some O-ring cord yesterday...

Re: Giant Wimshurst Machine - could use some guidance
Ash Small, Sun Jun 08 2014, 01:27AM

If you can't get any carbon fibre locally, surely he can post it for next day delivery?

If he posts it Sunday, you'll get it Monday, or tuesday at the latest.

Surely you have 'next day delivery' in the States?

EDIT: Even if you have to use aluminium foil or something now, you'll have the carbon in a day or so.

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Sun Jun 08 2014, 03:00AM


Canada.

It's atrociously expensive. Like, over a hundred for a letter. Plus it has to clear customs and the like.

Plan is, get it working with what I can, ASAP, then just do an order and replace all the junk with better stuff.

...

Progress:

- Tried to find a 5/8" drillbit to drill out the new 6" pulleys (1/2" axle) so I could throw a 1/2"-5/8" bushing on them. 21/32" is the closest I could find. Nope. Abandon that.
- Figured that I might as well try 2x the drive torque by doing the crossed belts thing (both pulleys are drive pulleys, versus before, one was slipping and all torque came from a single large pulley).
- Took off old belt. New belts had to be built in-place, because there's no way I'm pulling those discs down by myself to get the belt around the upper axle. Thankfully the lower axle is easy to remove. I'm re-using the washer fluid hose rather than the Oring, because I'd rather practice and destroy the $15 hose than the $100 Oring cord.
- Tried adjusting the pulleys, they're stubborn. The keyway is damaged from set screws being oversized.
- Belt #1: Good! Very tight, barely able to stretch it onto the pulley.
- Belt #2: Impossibly tight, starting to fray. Might not have waited long enough for the superglue, or might just not be long enough.
- Belt #2: Throw away, build a new one.

What a difference! 1/2 the pulley ratio and 2x the drive friction (both pulleys are powered by the lower axle now).

It's a sensible ratio. 90% of my power isn't going into heating up a slip pulley without a bearing (not unsolvable, but crossed belts has no slip pulleys to even deal with). It's 1/2 the total belt length so less stretch and slop (no horizontal pulleys). The belts are far, far tighter because I pushed them harder. Just everything is superior.

And I can get it going fast enough that wobble becomes a problem. Probably 180 RPM? Terrifying fast. Something's ticking regularly and I don't know what it is. Don't care, it's not a Porsche.

I came up with a solution to the neutralizer bars: 2x4s and zipties. Frame along one side and lock it down.

Will try the carbon fiber neutralizer brushes.

Wish I had a capacitance meter to check the Leyden jars so I can do some calculations and research on the energy there (I guess that can be done now, even as open ended tubes?). Mine's packed away somewhere.

Re: Giant Wimshurst Machine - could use some guidance
Patrick, Sun Jun 08 2014, 03:22AM

i can send more than youll use, just need to know what length the scraps should have as a minimum. 1 inch may not do you much good for example.

in any case, i measured a single "strand" of 3,000 fibers. 6.5 inches long / 30 ohms = 4.6 ohms per inch. Its ultra soft fabric, like silk. i dont know how youll attach it though. i love silver epoxy for low current, you could mash it into the CF real good, so that might work.

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Sun Jun 08 2014, 03:30AM

Okay okay, I'll just post the video too...



...

Oh, hey Patrick. That's awesome, thanks a bunch! Let me figure out if I need it or not and I'll PM you if I do.

Re: Giant Wimshurst Machine - could use some guidance
Eleccentric, Sun Jun 08 2014, 05:28AM

I think you'd be better off using two complete 5 gallon bucket Leyden jars in series for each side, rather than doubling up buckets for single jars. I'd invert the bottom one, so it's butt-to-butt with the one on top, with the outer foils in direct contact.

The 18 inch spark will draw equally from each Leyden jar - either jar would only give half that spark distance to ground on its own. So, you may not need to put two in series after all.

The voltage strength of PP is much more consistent than PVC. Depending on what exact type of PVC you have, it may be far better or far worse than the PP.

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Sun Jun 08 2014, 09:20AM

Progress pics. Because few people want to read walls of text.

The crossed belt. That's the spot where it rubs. Not a big deal.



Lower axle assembly. Note how I'm completely ignoring the big pulleys and the flat pulleys. 6" pulley, dual-belt drive, and sailing away from my problems.



Neutralizer bar #1. Spaced with 2x4, held in place with those zipties that have a screw hole at the end. Stays put and doesn't wobble now.



Neutralizer bar #2. Couldn't put it in the same place or use the same arrangement because the PVC brace to the output electrodes is in the way, and, since the belt is offset (pillow block bearings are mounted off to one side, not middle), this one needs more angle. No problem. Also note where the belt makes an X.



See the white plate? Clever little idea the new shop guy came up with. A lot less friction between rubber and smooth plastic than rubber on rubber. Should cut down on belt wear, for the... oh.. 60 minutes of runtime this prototype will ever see in its life.



Carbon fiber brushes! 60 ohms per cm. Fantastico!




Also did a lot of design work so I'm not figuring things out under the pressure of also doing them that day.

Tomorrow To Do:

Leyden Jars:

- Fold tape over inside, attach to chain with slack.
- Fill bottom with sand for weight (electrical issues?)
- Cut acrylic plate & hot glue bottom cap?
- PVC glue bottom and top.
- Top pivot will be unsoldered copper, two elbow with a lever to contact the comb bar.
- Make a chicken stick
- Make a safety chain (gator clip to short out jar when not in use in case it self-recharges).
- Disarm plug between caps along ground.

Neutralizers:

- Question: Do they have to be at the same angle? Right now they're not, one is a few degrees off the one on the other disc.
- Dice up carbon fiber brushes and alum foil onto bars.
- Extend pipe lengths (they're a bit far for the brushes to reach).

Combs:

- Replace with CF?
- Build comb #2

Electrodes:

- Anchoring idea tried and failed today, not sure how to secure them when mounted.
- Rubber bands at pivot? Ghetto but should work?
- Fill with sand, tape off, for balance.
- Ziptie anchors onto pole and post, then use rope/string tie-offs to hold at angle.

Discs:

- Disassemble axle, brace, reach inside and rip protective covering off? Already looks way better just with the outside few inches gone.

It's a lot of work but I think I already know how to do most of it.

Re: Giant Wimshurst Machine - could use some guidance
Ash Small, Sun Jun 08 2014, 11:54AM


It was late here last night, I forgot you are in Canada. If it takes a few days to get there you should still have it by midweek.

Re: Giant Wimshurst Machine - could use some guidance
Eleccentric, Sun Jun 08 2014, 07:46PM

You're soooo close! And, once you take the backing off the discs it will look gorgeous

Counter balancing the discharge electrodes will probably work best, so they'll stay in position with some amount of friction at their pivots.

Sand in your Leyden jars will probably be OK, but there are two things to consider. First, the makeup of the sand - the closer to straight silica the better, I think. Second, sparks will track over a surface considerably longer than they will through open air, but since you already have the surface of the PVC in play, this might not be an issue at all.

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Mon Jun 09 2014, 12:09AM

Well, new security rules passed on from the bigwigs (not the people I deal with). Because I'm not staff, I'm not allowed to be in the building unless someone's in the room supervising me. I guess the fear is after dumping 200 hours in 2 weeks and a few hundred dollars of my own cash into their project, which I've done basically on a handshake agreement, I might turn a bad leaf and decide to start vandalizing the place without anyone to guard me.

Considering I'm available late afternoons and evenings... that cuts my shop time down to an hour or two a day.

Oh well, I guess that's more important than their deadline.

Progress:

- Recut depth-wise pipes on the neutralizer bars, spaced for brushes.
- Cut brushes.
- Alum taped brushes to neutralizer bars, ready to test and....

Kicked out.

It's still daylight out! I'm going to go relax and enjoy the first evening I've had free in a long time :)

Re: Giant Wimshurst Machine - could use some guidance
Ash Small, Mon Jun 09 2014, 12:14AM

The 'Big Wigs' don't like you doing allnighters alone, it goes against every health and safety rule in the book. You are dealing with lethal voltages here, not to mention everything else.....Yes, I know it's the amps that kill.........I bet their insurance doesn't allow it.

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Mon Jun 09 2014, 02:16AM


Nope, not that. I told them from the start that I would not be operating the machine without someone who knows CPR nearby and another person to call an ambulance. My rules, not theirs. They're (office people, not people I deal with) insistent that it's safe enough for the final version to only need a railing, not an enclosure, despite my insistence that if a kid grabs a Leyden jar while it's charged it'll kill them.

I also had company during the allnighter, which was a 1-time thing to push for their deadline.

I asked if I was okay if I did assembly work at a desk in the non-shop lab where staff are allowed to work alone. Nope. Asked if I could do design work on my laptop, nothing physical. Nope. Not even allowed if someone else is in the room, unless they're specifically assigned to supervising me.

Zebra priorities.

I've done almost all of this with zero paperwork beyond a background check to make sure I'm not a pedophile (confirmed, I'm not). I'll consider that an accomplishment in itself, this place is infamous for it's fortress of red tape and bureaucratic dragons lurking in offices.

Time to whip out the letterheads and forms signed in triplicate.

Re: Giant Wimshurst Machine - could use some guidance
Antonio, Mon Jun 09 2014, 09:42PM

Some notes:

Leyden jars with bottom glued: Probably will fail soon, if not immediately. A seal with hot glue between the tubes and bottom caps may work, but must be very well made. Any imperfection will be a weak point.

Fix the jars firmly to the structure. No need of ballast.

It's better to have the neutralizers adjustable, to look for the best position for the desired spark length. If the angle is too high the machine does not work. If too low it sparks across the disks and neutralizers.

The neutralizers brushes must touch the disks very lightly, or the sectors and disks will be damaged. If the printer brushes are too short, you may try to fix them at the end of flexible wires or springs (last resource). If the contacts are not perfect the machine may not start. Thin nickel-chrome wires from wirewound resistors work well, but eventually break. Thin steel wire works too, but I don't know if it is easy to find. Copper leaves black stains.

The charge collector combs can be made with the carbon brushes too. Just leave them at some distance of the disks. If an accidental touch happens (will happen) no damage will result.

The usual method for fixing the terminals so they can rotate is to attach them to the tubes that make the conductors to the charge collectors with large fended metal plugs.

Remove the protective cover from the disks. Be careful about how you keep their separation. I like to use fiber washers lubricated with paraffin. Metal washers damage the disks.

The small pulleys driving the disks will slip with the machine charged. The torque required to keep the large charged disks turning is not small.

About kids (or adults) turning cranks: You will see that most people do not know how to turn a crank.

Re: Giant Wimshurst Machine - could use some guidance
Patrick, Tue Jun 10 2014, 02:04AM

excuse me, I believe you have my stapler...

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Tue Jun 10 2014, 03:44AM


Well, I'll just use 5x as much hot glue as I think necessary. I'd use silicone, but I'm impatient. (rtv silicone takes 24h to cure).


Well, I guess I can change it with shims, but, without redesigning it, it works well enough as-is.

How high is too high, and how will I know it is too high or approaching too high? Do mine look to be too high?

High is better, generally, yes?


I tweaked them and they work great now. Just barely touching, no rubbing. Way better than brass shim stock.


Moot point, but, I make chainmaille. I have steel in a dozen wire gauges. Brass in 4 or 5, bronze in a few, etc etc.


(Just one particular order).

My niche is the tiny stuff:


(46g copper, 0.0015").


I didn't have long enough nylon. I'll have to make some plugs inside I guess (nut and bolt).


I'm using a pair of nylon washers 1/4" thick. Maybe 1/2" thick each, I forget. Probably 1" total separation, so, yeah.


So far I didn't notice any torque difference, but I didn't charge it up that high (more on that in the next post).

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Tue Jun 10 2014, 03:52AM


Well, I'll just use 5x as much hot glue as I think necessary. I'd use silicone, but I'm impatient. (rtv silicone takes 24h to cure).


Well, I guess I can change it with shims, but, without redesigning it, it works well enough as-is.

How high is too high, and how will I know it is too high or approaching too high? Do mine look to be too high?

High is better, generally, yes?


I tweaked them and they work great now. Just barely touching, no rubbing. Way better than brass shim stock.


Moot point, but, I make chainmaille. I have steel in a dozen wire gauges. Brass in 4 or 5, bronze in a few, etc etc.


(Just one particular order).

My niche is the tiny stuff:


(46g copper, 0.0015").


I didn't have long enough nylon. I'll have to make some plugs inside I guess (nut and bolt).


I'm using a pair of nylon washers 1/4" thick. Maybe 1/2" thick each, I forget. Probably 1" total separation, so, yeah.


So far I didn't notice any torque difference, but I didn't charge it up that high (more on that in the next post).

Progress: (SPOILER - BIG PROGRESS)

- Attached neutralizer brushes.
- Test assembled brushes, adjusted to avoid rubbing.



- Crank test. Expected to hear static, smell ozone, feel resistance change.
- Static and ozone, no noticeable torque difference when charged.
- Reassembled comb/inner electrode #1.
- Modified comb/inner electrode #2, rebuilt from scratch designed for carbon fiber instead, mounted to output poles.



- Disassembled old outer electrode assemblies, reassembled new ones.
- Attached cabling system to control electrodes.
- Test spin, adjusted to avoid rubbing.
- Crank test, expected to hear static, watching for which combs work better...
- ... Leapfrog progress. It's already snapping through the sparkgap!



- Accidentally touched one electrode. Good news, it just hurts, not fatal.
- Purposefully touched electrodes, noted that it slows spark rate on the poles. Painful *&* detrimental.
- Tested spark limitations. Max of about 8". Spinning wheel faster delivers slightly faster zap rate, but, past a certain point does nothing.
- Called it quits before making Leyden jars, which will probably fail. Wanted to end on a high note.



Gap is 3.5" or so. I adjust it in the video to about 8" before it stops arcing. No Leyden jars/caps hooked up at all yet.

Should I be concerned that it stops zapping after 8"? Too many sources of leaks? Or should I not worry until I get some Leyden jars put on there?

Re: Giant Wimshurst Machine - could use some guidance
Eleccentric, Tue Jun 10 2014, 05:51AM

Awesomesauce! No, don't worry about it only doing 8" without the Leyden jars. The sparks will be muuuuuch longer once you have those in place and sized properly. Your neutralizer brushes are set quite high/steep, but it doesn't seem to be negatively affecting operation.

Once the jars are attached, there will be a heavier electrical load on the machine and you should feel it take more energy to turn, or else your discs are too far apart and you are only getting a fraction of what the thing is capable of producing.

Regardless, congratulations on a crazy huge machine!

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Tue Jun 10 2014, 09:22PM

I found a capacitance meter.

Leyden jars without endcaps put on are 1.53nF and 1.57 nF each.

3.10nF.

At 300,000v...

140 Joules. About the energy of a .22LR bullet.

Umm...

Terrifying.

Back on page 1, people said I might have as high as only 30 joules, which would be an impressive bang. 140 is.. MORE IMPRESSIVE.

Well, time to finish them up and see just how loud they are.

I got consistent 12" sparks (1hz) today (could hear but not see), without any capacitors.

Re: Giant Wimshurst Machine - could use some guidance
Ash Small, Tue Jun 10 2014, 10:42PM


I think in series, the capacitance is halved. I think you need to re-calculate. I've had a drink, though.

Awesome machine, though

Re: Giant Wimshurst Machine - could use some guidance
Eleccentric, Tue Jun 10 2014, 11:02PM

Yes, that is only 150kV on each jar, but even so, those may be bigger than you need. Wear hearing protection when you first fire it it up.

So far your machine seems to be acting normal - the "failed" sparks that you can hear but not see happen with my machines as well if the electrodes are too far apart.

2*0.5CV^2 = 34.875 joules (using 1.55nF and 150kV) Much more reasonable!

Hmm.. ..0.5CV^2 = 34.875 joules (using 775pF and 300kV) So I'm pretty sure I've got that right.

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Wed Jun 11 2014, 05:35AM


Well... frustrating turn of events.

Coincidentally, the day I provide them with a functioning prototype, is the same day they (bigwigs, different than before) decide, retroactively, they don't have the budget to build one (the prototype, they still have buckets of money for the fabbed version based on all the documentation, measurements, etc from the now-finished prototype).

They approached me and asked me to do this, not the reverse. I've been regularly communicating the costs to them, and gotten repeated assurance it was within budget and to keep progressing. Of course, working on trust and not legal documents, I don't have much legal recourse for time or materials.

Which is fine. If you can't trust someone without a contract, at sub 6-figure ranges there's not much point in trusting them with one either. Lawyers win it all anyway and I don't want to live my life in litigation.

I'll try tomorrow directly with the person who made the decision to see if it's just miscommunication, but, I wouldn't even say my mood is cautiously optimistic.

Oh yeah, so, it's done. Just waited for the PVC glue to dry on the Leyden jars before I could test it.

Bittersweet.

Re: Giant Wimshurst Machine - could use some guidance
Patrick, Wed Jun 11 2014, 06:57AM

thats crap on a stick...

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Wed Jun 11 2014, 07:32AM


Ehn, let's see what happens tomorrow. I'll give them the opportunity to save face, maybe it's all a big misunderstanding.

Re: Giant Wimshurst Machine - could use some guidance
Finn Hammer, Wed Jun 11 2014, 08:10PM

AwesomeMatt,

Whatever happens, you have done an outstanding job with this prototype, and that is your intellectual property, the hands on knowledge about how to build a large Wimshurst. Not many people try that.
And it has been very interesting to follow this thread!

Cheers, Finn Hammer

Re: Giant Wimshurst Machine - could use some guidance
Hazmatt_(The Underdog), Thu Jun 12 2014, 03:09AM

Wonderful to see that IT LIVES!!!

1. NEVER trust anyone with money. They don't make or keep money by spending it.

2. They will probably aim to steal what they can from you. You've already done all the footwork for them.

3. I can't tell you how many projects I've done for people that had big mouths and never paid. This is what happens when you do a job for a dreamer.

4. You come first. No more work until there is reimbursement. Labor is worth something, you need to be compensated for materials AND labor.

5. SOW. Statement of Work. Always get a statement of work, regardless of contract. This ensures no miscommunication.

6. Reserve the right to refuse work if possible. You shouldn't have to let the customer break your arms so they can have a pretty spinning gadget.
I have a hard time with this one because I do help people who don't know what the hell they are doing, and to my detrement. It's better not to.

-Matt

Re: Giant Wimshurst Machine - could use some guidance
Dr. Slack, Thu Jun 12 2014, 07:41AM

Going back to your OP, you've been 'brought in on a team'.

So the machine so far, who's paid for all the acrylic and stuff? You, or multiple people across the team? I'm trying to understand actual ownership of the machine or its parts.

Where I'm going with this is, if it's all your stuff, and you haven't been reimbursed for it, it might cross your mind to take it off site.

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Thu Jun 12 2014, 10:38PM



Was originally how they phrased it.

The build "team" is me.

I started off answering some HV and technical questions about the build. For example, they were really concerned about nearby carpet (because carpets cause static!) and about grounding, (how thick does the rubber mat they are standing on need to be so that it's safe for children to touch the machine?), and other things that kinda red flagged their knowledge of electricity in context was quite poor.

Then they said they needed to get it done quick, and asked if I was interested in showing up in person to join the build team. So I said I couldn't spare many hours, but sure.

The team was... me.

One other guy ran the Shopbot, but other than that, every nut and bolt has been me. Their shop guy quit right before I was brought in, there was no one build anything, and everyone else had their own work to do.

So, my "team" was really just "The people who wanted it done (people working there)" and "The people getting it done (me only)." They told me how big they wanted it and the spark gap to be and did a little bit of the shopping but that's it. Most days I was in the shop I didn't have any communication beyond "Good morning" and rolling progress updates.

Oh, and I conned a friend with delicate ladyfingers to do the tracing and cutting of all the sectors for me.

Me keeping the prototype isn't leverage. It has no value to me (I'd donate it to the local hackerspace), and it has no value to them. It's taking up room in their shop, I'd be doing them a favor.

They needed the prototype for:

1 - Proof of concept, can a machine that size get arcs that size.
2 - Demo, how does it look in the gallery they're putting it in, does it fit there.
3 - Measurements/values and building materials, build plan, etc for the fab lab to copy.

The day I got it working they're basically done with it. I sent them all the documentation I'd figured out on it, not just for this size but any size, a week ago.

I was gong to be unveiling the prototype at the local Makerfaire in a couple months, but, that'll just be advertising for them, so, probably not doing that anymore.

Ehn. I haven't gone in to talk to them yet, but, it's okay. I'd rather this thread not turn into a bitchy one, so far it's been interesting to anyone in terms of a project log. I appreciate the concern, but I only vented as an explanation of why there might not be any more updates. Let's let the thread stay as positive and drama-free as possible.

I'm going to pick up my tools today. If there are more updates in the next while I'll post them.

Re: Giant Wimshurst Machine - could use some guidance
Hazmatt_(The Underdog), Fri Jun 13 2014, 03:28AM

I'm not trying to dramatize the thread, I'm just trying to point out that many of use get "used" for these types of projects, and it usually means that we get the bill.

Re: Giant Wimshurst Machine - could use some guidance
Antonio, Sat Jun 14 2014, 09:37PM

An interesting video showing several machines, including a large sectorless machine. Several construction ideas can be seen. The "Leyden jars" appear to be series associations of commercial high-voltage capacitors. The sectorless machines use just a small area at the edge of the disks. One machine takes charge just from the frontal disk.

Re: Giant Wimshurst Machine - could use some guidance
Newton Brawn, Sun Jun 15 2014, 02:47AM

Hi !

Very interesting.
The Leiden Jars are made of unusual construction,
How is it made ?
Ceramic capacitors in oil inmersion ?
A MMC ?

Re: Giant Wimshurst Machine - could use some guidance
Patrick, Sun Jun 15 2014, 03:26AM

yep we get used, ive had a person seek me out for a build here on the forum, and two on another forum, even signed NDA's. but i never got ripped off, only becuase i refused to work or by parts unless i got the parts-they got the bill. but alot of companies and individuals "scout" those of us here on the internet forums, just for the talent, then their end falls through. probly due to there incompetence.

Re: Giant Wimshurst Machine - could use some guidance
Antonio, Sun Jun 15 2014, 04:37PM


Apparently series of doorknob capacitors immersed in oil.

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Thu Jun 26 2014, 01:09AM


Update:

I'm not going to say every way I've been treated has been on the up and up... but... finally had a discussion today and seems like, it was a misunderstanding. It's not settled, there are some (I believe) genuine accounting snafus that will take a while to resolve in a way that ends well for me, but it seems to be headed in the right direction so I'm being patient.

It's mostly been certain people who should have been kept informed (by the people I worked with) were not informed, etc etc. Which means decisions for them would have been made differently, which means the decisions I made would have been made differently, and so on.

I am again returned to "cautiously optimistic."

But enough bs and drama, you guys don't care. Here's the good stuff: I'm going in tomorrow to hopefully finish the Leyden jars and get some wicked sparks out of it. If things go sour again, at least I'll have enjoyed the experience of some indoor lightning.

Re: Giant Wimshurst Machine - could use some guidance
Eleccentric, Thu Jun 26 2014, 04:49AM

I think it's a safe bet that anyone who tried to help you with this project does care about how you were treated. That's what was first on my mind when I saw you'd posted to this thread again.

The big sparks are an aftereffect, albeit a really cool one. I look forward to your next post.

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Thu Jun 26 2014, 10:46PM

Well... wtf.

Good: Paperwork is signed according to what was agreed.

Better: Leyden jars are done... ish.

Bad: The machine doesn't work. At all. Even a little bit. Even 3 steps back.

...

So in the last 2 weeks, it's just sat. I put up a sign saying not to touch it, doesn't look like anyone touched it, everyone says they were scared to go near it.

1 - With Leyden Jars... spun it for a good 2 minutes.. nothing.

2 - Without Leyden Jars (same as the last day I worked on it)... nothing. No sparks. Not even 1/2".

3 - Without combs.... nothing. No corona, no hiss, no ozone, no sparks, no static, nothing. There used to be.

Other symptoms:

- Belts are way looser (hose that's been left stretched for 2 weeks). Still turns fine.

- Seems a lot easier to crank. Maybe because belts are so loose they stretch when I start up, and because there's not huge amounts of tension to overcome all the time. Or maybe because it's not doing anything. Actually seems easier to turn than before I hooked up the neutralizer bars too, so, not sure if that's me or not.


What I've done:

- Washed/wiped the sectors with alcohol.
- Adjusted neutralizer bars to a less vertical X.
- Made sure neutralizer bars are touching and the brushes are touching the sectors.

...

I dun goofed. What am I missing?

Only thing I can think of is that it's a bit warmer in here, maybe more humid because of the rain as of late (no different than two weeks ago in terms of moisture), but, I'm still in a high elevation city with mostly a borderingly desert climate.

I think I'm going to take the night and think on it... I'm utterly baffled. Maybe rebuild the neutralizer bars from scratch in case the carbon fiber brushes are contaminated with Alum Oxide?

Re: Giant Wimshurst Machine - could use some guidance
Eleccentric, Thu Jun 26 2014, 11:51PM

If you can, reduce the separation between the discs. Also, make sure that when a sector is under a neutralizer brush, that it is aligned with a sector on the opposite disc.

Any chance that the backsides of the discs have become dusty?

If it is the humidity, you could try hitting the thing with a space heater for a while, which will work especially well if you can cover the whole thing in a tent of drop cloth. The biggest risk is softening the acrylic.

Re: Giant Wimshurst Machine - could use some guidance
Antonio, Thu Jun 26 2014, 11:58PM

You are using fiber brushes in the neutralizers, right? They may cause startup problems due to the high resistance. Use thin metal wires in at least one of the brushes. Try also to excite the machine by placing an electrized PVC tube opposite to one of the neutralizer brushes.

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Fri Jun 27 2014, 02:17AM


Not easily done. My spacers are fixed and I have to cut new lengths every time, and I have to have help pulling it apart.

BUT.. they're probably too far apart anyway, so, it was on my list.

Issues with bringing them closer together are the fact that the axle is already bowing (so discs are closer at the top than the bottom), and one of them is still wobbley so it needs some separation. I can probably reduce it by half though.


... Hrm.

On the opposite disc, or the opposite side of the same disc?

The latter... making sure the neutralizer bars short sectors on each side... done.

The former... I'm not sure I understand correctly.

Let's take one disc and neutralizer bar as fixed. How should the one on the opposite side be arranged at that particular snapshot in time? Where the neutralizer brush touches the sector on the front disc, the rear disc should be what? Also a sector? And the opposing neutralizer brush also there?

Previously... the neutralizer brushes were not matched. One was more vertical than the other. It still worked immediately.

Also... the belts are now stretched, so, discs don't spin in lock step. Generally one or the other starts to spin first. The belts slip and they stretch too so there's no way to ensure what's happening on one side is happening on the other.


Two weeks in a shop that does mostly woodworking? Yep.

Not that dusty, but, dusty, sure. Also, I only alcohol wiped the sector covered parts.

Add that to my regular maintenance suggestions?


Yes, carbon fiber. I didn't measure the resistance.. I should do that. Maybe the ozone degraded the brushes or something.


Okay, will do.


Just give a tube of PVC a silk rub, or do I need to create a steady electrical source?

...

The thing that is shocking is that, it's not just not working a little bit, or seeing a performance decrease. It's right dead nothing at all.

Re: Giant Wimshurst Machine - could use some guidance
Antonio, Fri Jun 27 2014, 02:45AM

Excessive distance between the disks may be a problem, but if the machine was working before in the same condition the distance is ok. Axle bowing is a big problem. You may need to use a stronger axle. To excite the machine a well electrized PVC tube shall be enough. Verify if the humidity is low. Heat the disks and insulators a bit with a hair dryer if it is high. Aligning the neutralizers is not necessary, but good if they are insulated from the structure of the machine.

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Fri Jun 27 2014, 03:24AM



They are definitely not insulated, can't figure out a way for them to be insulated, since they have to be mounted to it. They effectively short to the axle and the support beam.

-----

In other news, I would really like to give back to the community by documenting this build and creating a tutorial on how to design a machine of any size.

There is really no place that has this knowledge recorded anywhere. I would have been way in over my head without one-on-one mentoring, interaction, and Q&As from 4HV and other places.

Once the show and tell from this machine is complete, I would like to use this thread to learn more about how and why some of the constraints in the machine are what they are. I have tried to learn as much as I could so I can solve my own problems, but I know at least half the time I just took someone's answer, or number, and used it blindly without having any context behind it. That worked for me, but it's very prescribed.

My goal would be to make a tutorial that takes something complicated, and explains how someone with almost no knowledge of electronics or physics could solve their own problems when designing a machine.

So, hopefully I can continue to pick your guys' brains a bit more, and then after that whenever anyone asks those questions you can say "One of our members filmed a tutorial, just go watch that" instead of explaining it again or giving them specific numbers that work only for that specific person.

Re: Giant Wimshurst Machine - could use some guidance
kilovolt, Fri Jun 27 2014, 09:36AM

AwesomeMatt:
I would highly recommend to replace the fiber brushes with something with really low resistance. I had exactly the same problem with one of my selfmade machines (I took brushes from a laser printer). Sometimes it worked, but sometimes the machine didn't start at all. Take copper brushes and it will work again (I know the copper brushes will lead to scratched disks, but with these the machine will work reliable).

I tried several other materials for the brushes, for example some sort of an antistatic packing material, which had the same results: Intermittent starting problems.

Humidity has an influence, but even with relatively high humidity my machines work, however with less output of course.

Good luck
kilovolt

Re: Giant Wimshurst Machine - could use some guidance
Dr. Slack, Fri Jun 27 2014, 09:43AM

The crossed neutraliser bars. If they are ungrounded, then they *must* touch opposite segments at the same time. If they are grounded (and the wood frame may or may not be an adequate ground at these voltages and currents, it all depends on humidity and wood type, use a wire to be sure) then that requirement disappears. All they need to do is to ground the top surface of a segment as it passes opposite the charged segments on the other disk. This is how the charging mechanism works. Look up induction charging, for instance , the Wimshurst machine automates this process by passing the segment close to the segments on the other disc, grounding it briefly (or connecting it to the oppositely charging segment which amounts to the same thing), and then pulling it away again. Another way to look at it is the neutraliser contact just has to source or sink whatever charge has to flow to the segment. That means it either needs a connection to ground, to the other oppositely charging segment, or has to have a large capacitance to ground.

There's no requirement to phase the segments on one disc to the other disc *assuming* the discs are further apart than the gaps between the segments, and the segments are wider than the gaps. That is, each segment when it's under the neutraliser bar being charged just has to see 'some charge' on the opposite disc.

Is the machine still not working? Any leakage from the segments or the output terminals will kill it. Get a fan heater / hair drier / paint stripper and make sure the machine is dry on the surfaces. Can the room's AC be adjusted to be drier? I've seen many an electrostatic demo that didn't work until everything had been dried out.

If that fails, test all parts of the machine for their ability to hold a charge. Ideally, build or buy an electroscope, ye-olde fashioned hanging V-shaped gold-leaf thingy. And you could do with a source of high voltage, can you borrow a small VandeGraff or Wimshurst from anywhere. Charge up each output terminal, see if they hold charge. If not, separate the terminal and Leyden jar, and test each separately. You could check the segments, but really if you've alcohol wiped the discs then there's not a lot more you can do.

A great place to document the how of the machine would be on our HVwiki. You might even get some others pitching in to add and fix stuff.

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Fri Jun 27 2014, 10:25PM


I tried charging it with a big staticy PVC tube that I'd rubbed on my shirt until it crackled. I'm not sure how to charge it. Homemade Lightning is a bit contradictory. Neutralizer bars form an X... I'm supposed to hold it behind one neutralizer bar, where there is no bar on the back side? Hrm.

I held it all over the place.

Not any effect that I could tell.

I did notice that the belts are so stretched they now fit over the 12" pulleys.. so I figured, why not, and stretched them over the big pulleys. Lo and behold.. when I got it going REAAAAALLY fast, snap crackle pop SPARK. But it has to be moving really, really, fast to get anything. Like there's a critical mass.

Two weeks ago, I hardly had to get it going at all before it was farting electricity.

Also... when I get it going that fast it's rocking and swaying a lot, so, I don't want to neglect the possibility that the machine is working simply because of some benevolent unballancing issue that corrects the problem.

I'm kinda heartbroken about the carbon fiber being a bum choice, but, if it is then it is. I'll go looking for brass instead again.

The neutralizer bars are copper, sitting directly on the upper metal axle, so, they're certainly grounded to each other. But they aren't now and have not ever been symetrically angled to each other.

Since the brushes only touch the last 1/2" of sector, and it's rounded... there's a good chance there will be dead spots on the reverse side.

I first joined 4Hv a couple years ago to add to the wiki, but, it seems functionally abandoned. I don't mind documenting things, but I loathe documenting things that no one reads or participates in.

...

Up next... trying out these Leyden jars while spinning really really fast.

Re: Giant Wimshurst Machine - could use some guidance
Eleccentric, Fri Jun 27 2014, 11:29PM

You could probably salvage some very thin and springy flat metal from an old wind-up watch or an analog movement meter.

I wouldn't abandon the carbon fiber entirely - perhaps more substantial brushes made from longer sections of tow would work better.

Re: Giant Wimshurst Machine - could use some guidance
Antonio, Fri Jun 27 2014, 11:53PM

If the machine works only at high speed the most probable problem is leakage. Verify if the insulators holding the charge collectors are clean and dry. Verify if the machine works without the charge collectors. With only the neutralizers in place it shall charge the disks very evidently.
Look also at possible points in the charge collector assembly that may be causing leakage. A speckle of dust in the wrong place is enough. I like to clean these machines with furniture cleaning products containing silicone and wax, instead of with alcohol. WD-40 works too. Test any cleaning product first in a section of pvc tube, that must be easily electrizable by friction after cleaned. As a last resource, decrease the separation of the disks.

Re: Giant Wimshurst Machine - could use some guidance
Eleccentric, Sat Jun 28 2014, 12:53AM

Sooner than use brass, beryllium copper or phosphor bronze would be much better choices.

Or perhaps you could use bunches of tiny steel ball bearings, or just iron filings, attached to very strong NIB magnets. I'd be wary of the filings since they might get picked off by strong electric charge.

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Sat Jun 28 2014, 01:59AM


Hrm... Lemme check my bucket...



Not a single damn spring.

When I was a kid, MacDonalds had those yank-back-release spring powered toys. A trip to a thrift store should satisfy that.

Also, if resistance is too hight, I'll just add more and longer brushes. Right now there's only 2 brushes per... brush. If I slap on a run of 8 instead... will be 1/4 the restistance.

Went to a carbon fiber place today, they sell in amounts of 500lbs only... yet... have no samples on hand. so, I can't sneak a sample and use that, nor could I order a small amount. Foey.


Interesting. Okay.


That is the first thing I tried yesterday. I used to get static and hiss before I'd even given the handle a full crank, before I even built the combs. Same deal, absolutely nothing until I get it going really fast.


Why? Would any residue of the cleaning product be considered "dirt" or would it be considered beneficial insulator?

...

So, the biggest sparks I could get this time were maybe 5", with the leyden jars hooked up. I was sweating up a storm trying to keep it powered at that speed.

But, woohdamn were they loud. And the farther apart I had the electrodes, the more loud they were. Disproportionately. Naturally... voltage required to jump an airgap is linear with the gap. But, energy stored in a capacitor is proportional to voltage squared... so... doubling the gap is 4x the energy in the snap.

My camera didn't pick them up very well this time. Overwhelmed the sensor I think. It's showing 24 long arcs across the middle of the conductor poles. Maybe just lens artifacts. Kind of a crappy deal, since I hardly spent any time watching it with my own eyes.

I was told the prototype has served every purpose it could, and I'm done working on it. Pack it up, head home. So, other than the crappy video I got today, maybe I won't get any more, perhaps for weeks or months.

They're suggesting that if the fabricator has questions, that they hire me as a consultant, and, if necessary for me to tweak or experiment with the prototype more, to come back and do that only if they need me to.

It's Friday so people were ready to get out of there. We had to stop anyway when the mis-sized crank finally bent its bolt and snapped the arm.

Well, the demo stopped. I was, umm, just cleaning up and went back for more. No more crank in the way, I hooked up the cordless drill. I umm, maybe let some of the smoke out of the first one, but the second one made it spin up nicely. I think I got somewhere around 10-14" sparks. I could see the flashes through the brown paper on the discs :p. I had to spin the wheel increasingly fast to accomplish anything at higher voltages. Not an issue of "Just store more energy" but, seemed "Must overcome increasing leakage to have any left over to store." Interestingly, if I could get to a certain voltage at all... I could get regular sparks there. Like, easily every 3-5 seconds, but if I didn't get one for maybe 10-12 seconds, I never would.

I had the earmuffs on and it was loud. At 5", they sounded like gunshots and made me jump the first time I heard it when someone else was cranking. At 10+"... I swear I could feel the sonic shockwave.

At some point before I could see if the Leyden jars were going to puncture, the crossed belt ripped itself apart and today spun to a close.


Gimme a few hours or a day to compose the video and I'll post it.

Re: Giant Wimshurst Machine - could use some guidance
Antonio, Sat Jun 28 2014, 03:39PM

Carbon fiber brushes can be problematic. If they lose filaments they short-circuit the machine. There are always sparks at the neutralizers, and the brushes may burn and leave carbon dust, again short-circuiting the machine. And they always cause startup difficulties.
The best brushes are metallic, built in a way that touches the disks lightly, but with good contact.
Alcohol may dissolve the glue of the sectors, and the glue residue left may be not a good insulator, leaving the disks contaminated. It may also cause cracks in acrylic. I have seen a complicated acrylic part with several holes and threads that I tried to clean with alcohol after finishing it crack in several pieces.
I see that you know now the problems with belts and cranks...

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Mon Jun 30 2014, 09:48AM

Here's the (private) vid:



Or for those just looking for a picture, here's the old sparks versus the new ones:



BLAM BLAM BLAM.

I don't know that I"ll get a chance to work on it again, but, I'm about half way there, spark wise. Which means I'm about 25% there energy-wise. Final sparks are going to be lotsa fun.

The discharge right now is insane. The lightning bolt is already 2" thick at the one side.

The spark gap is still to narrow to be interesting, since almost every spark is just a straight line.

It's adding weird artifacts on video, little pre-arcs that are aligned left-right okay, but up-down wrong. I cut most of them, but they most often appear the frame before the blue spark (which often doesn't appear at all). I think they're some kind of lens effect, or, they're some residual image from the first feelers before the full arc.

A long odds thing will be to try to schedule some free slow-motion camera time to see what's up.

Re: Giant Wimshurst Machine - could use some guidance
Antonio, Mon Jun 30 2014, 01:43PM

The spark images at wrong places appear only in digital cameras. Probably some interference on the circuits of the image sensors. You didn't take off the backing paper of the disks, that is probably conductive and leaves the machine partially short-circuited.

Re: Giant Wimshurst Machine - could use some guidance
teravolt, Mon Jun 30 2014, 04:23PM

are you using the pvc Lydon's and do you have a picture

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Tue Jul 01 2014, 01:40AM


You're the 3rd person that's suggested to that as the likely fault. I concur. If I ever get to work on it again, I'll get a hand taking it apart and stripping the discs properly.


Yes, am still using the 4" PVC pipes, 42" long. 18" gap at the top, 4" gap at the bottom, 20" of aluminum tape.

Pictures.. no. But you can see them right at the end of the video. They are vertical and next to the 2" PVC output supports.

Why do you ask?

.


Question barrage. Any answers or feedback would be very helpful and documented in a tutorial.

1 - Instead of foil, would there be a point to using plates? I was thinking of stainless plates. Durability forever. Any electrostatic concerns?

2 - Would there be a significant reduction in leakage by rounding the edges of the stainless plates?

3 - Would it be helpful to CNC a small trough out of the acrylic discs for each of the sector plates to sit in?

4 - For LOTS of use, suppose it's spinning almost all day every day... any idea on using a protective (possibly disposable) film like Antonio did on his, with holes cut for buttons? I'm worried about the mechanical aspects and rubbing on the edges of the much softer adhesive surface covering.

5 - I still don't understand how a Wimshurst works. I have a fair knowledge of electrical things, ohms law, power law, that kind of hand-on level stuff, but I have very poor grasp of the actual physics. Could anyone walk me through what is actually happening, where the charge comes from, circuit-wise what the circuit is, etc? I know that at some point things will "click" and then all the little separate pieces I know but can't integrate together will fall into place.

Re: Giant Wimshurst Machine - could use some guidance
teravolt, Tue Jul 01 2014, 02:21AM

With van de graphs the more capacitance the more voltage but that doesn't seem so in a wimshurst just more current. I was just curious how much voltage a peace of pvc tubing will hold off. Shouldn't you be getting arcs that are about 18"? when I built my van de graph my biggest enemy was charges that bled off even the type of rubber the belt was and the way I joined it is a big deal. I think that your wimshurst is very nice and well done.

Re: Giant Wimshurst Machine - could use some guidance
Antonio, Wed Jul 02 2014, 12:06AM

1 - Durability is improved, more difficult to cut, can get loose and fly away, brushes break more easily. I used aluminum plates in this machine and saw all this:

2 - Yes.

3 - The brushes will like this, but this goes agains the idea of letting the brushes touch only the sectors, and not the spaces between them.

4 - Insulated sectors increase the performance significantly, because the sectors can be larger (more current) and the insulation is better (more voltage). I didn't think about the added protection, because it's difficult to apply the covers, and I don't have a good solution for buttons that can be easily removed. The material that I used appears to be quite difficult to scratch.

5 - The machine works due to concentrated electric field when a sector touches a neutralizer brush. Several sectors at the same time attract opposite charge to the touched sector, resulting in more charge on it that was present in the other sectors around it. I have a more lengthy discussion of this and simulations here:

Re: Giant Wimshurst Machine - could use some guidance
Dr. Slack, Wed Jul 02 2014, 08:21AM

It 'clicked' for me after I asked the question about the angle of the neutraliser bars.

1) Look up electrophorus This was one of the earliest electrical machines to multiply charge, and is the simplest place to start. The Wimshurst works on exactly the same principle.

2) What happens in the electrophorus is that you have a source of charge (a). This doesn't get used up during operation, so it performs over and over. You bring a conductive body (b) close to the source. The field from (a) polarises the conductor so there is charge separation between the closest and furthest bits from the source. Another way to look at it is that as the conductive body is conductive, it distorts the field of (a). This means that it is internally charged, and the field from that charge is neutralising the field from (a). Now you ground the point on (b) furthest from (a). Charge flows to/from the excess on that side to ground. Another way to look at that is the conductive body (b) has just got bigger by adding the conductive ground contact to it, which extends further away from (a). This allows the charge to separate further, and in doing this, some charge flows between ground and (b). Remove the ground contact, to stop charge moving onto/off (b), and pull it away from (a). The remaining net charge on (b) from the polarise-ground-unpolarise process redistributes itself all over the surface. As you further pull (b) away from (a) and other grounds, its capacitance to ground falls, and so with constant charge, the voltage rises.

3) A Whimshurt automates this process.

4) Let's assume that the bottom sectors on the *other* disc are charged (just go with me on this). These are (a). Now consider a sector near the bottom of *this* disc. It will be polarised by the charges on the other disc. As the disc turns, (b) passes under and contacts the grounded neutraliser brush, which allows charge to flow. Shortly afterwards, contact with the neutraliser is broken, and the disc carries the now charged sector across the midline of the machine, where it now acts as (a) to the other disc's (b)s when they get to their neutraliser bars. Finally, it is carried out to the edge of the machine, reducing capacitance from the various grounds so increasing the voltage. The high voltage sectors then dump their charge into the collecting combs.

5) So how does it start? No two bits of metal insulated from each other will have the same voltage, even if you don't walk across a carpet and then touch a segment. So a Wimshurst machine will *always* have a charge imbalance somewhere on it to start it. Because the brushes and the segments are conductive, the slightest voltage difference will cause charges to flow, that will then self-start the machine. This is in contrast to a Bonnetti machine, which is basically a Wimshurst with no segments. No current can flow here until the voltage is high enough to cause corona, so the neutraliser combs can spray charge onto the disc. A Bonnetti is typically started by charging a glass rod with silk or fur or something, then holding it opposite a neutraliser comb, to get charge spraying.

Other electrostatic machines.

The Kelvin Water-drop machine uses electrophorus charging. Subsequent separation uses gravity.

If you made a Van de Graff belt with alternate metal/plastic chain links, then it's called a pelletron, and you could charge it electrophorus style, but even those are more usually charged by direct spraying


Now this is the sort of post that ought to go into the, as you correctly point out, moribund Wiki.

Re: Giant Wimshurst Machine - could use some guidance
kilovolt, Mon Jul 28 2014, 02:41PM

AwesomeMatt, how is the actual status of this project now? Did you perform some improvements futher or is it discontinued?

Very best regards
hvpower

Re: Giant Wimshurst Machine - could use some guidance
AwesomeMatt, Sat Aug 09 2014, 01:13AM



To be honest, I'm not sure. I have not been back to the science center where I built the Wimshurst since I last mentioned.

I thought their plan was to use my expertise to review and evaluate the proposals and quotes sent in by the professional fabrication shops, and then to tweak their designs. I emailed my contacts and the said they wanted to bring me into the process later, if at all, if further work on my prototype is needed for the fab shop.

So, they've now chosen a fabricator without my advice, for, I think, all 8 new exhibits (the Wimshurst is the centerpiece exhibit of these 8).

They have worked with this fabricator before. The shop has built several of their electrical exhibits, and they have experience making things like Hailstorm boxes, tesla coils, etc for other museums. They do pretty good work.

But, they seem to be very much mechanical engineer people. And, frighteningly, they seem to have (admittedly) sent in a (flexible) quote (that was accepted) for the Wimshurst without knowing anything about them.

And, I mean anything. It appears 100% of what they knew about Wimshursts was from my last video, that the science center sent them.

I had a 2 hour phone call with them, and they asked questions about the design that were the most basic possible. Like, 5 minutes of wikipedia or youtubing "What is a Wimshurst?" would have answered.

They were very nice and intelligent people, and, reassuringly, as I started to explain things, they admitted there was hubris on their part in bidding on the job without knowing a lot more. They didn't know it had 2 wheels. They didn't know they were counter-rotating. They didn't what the Leyden jars were or what they were connected to... nothing.

These are the "experts" that were hired instead of having me build the machine pretty and solid the first time (toss in some budget for a carpenter and a machinist). These are the "experts" who were going to put an engineering stamp on the electrical safety requirements.

Not to impinge them, again they are very kind, very intelligent, very skilled people for mechanical and finishing work. I'm just blown away that the people who reviewed the bid process chose this fab group as the most qualified for this particular project.

I understand it's a managerial role, but, jeez, it's a science center, when choosing a builder for an exhibit, one should at least have a comfortable enough grasp of the technology to ask the right questions.

...

I've asked (to reconfirm) if I could show off the prototype at the local Makerfaire coming up soon, as first agreed, but gotten non-committal responses.

...

Oh, and let me back up. BEFORE I even talked to the fabricators, the science center was thinking of pulling the plug, citing affordability from the quotes they received.

They were thinking of making 2 reductions to the exhibit:

1 - Reducing the interaction
2 - Reducing the "genuine spark creation"

I'm not sure what that means, but the only way you interact with it is by turning the crank (so no more turning a crank?) and I suspect the second item means they're going to have a lightningbolt shaped piece of foil painted blue between the electrodes and an audio speak going "zap zap zap", while a motor turns the wheels which do nothing.

But whatever, maybe they figure who cares about science, as long as there's a big wheel that turns and the media has something to show while they interview some director or VP in the foreground about all the amazing things they're unveiling. Because that "inspires" kids to learn more about science.

...

Oh, or, they may scrap the Wimshurst entirely and go with something boring.

...

Right now, I'm basically writing a "How to Wimhurst" document for the fabricators, *without* telling them exactly what to do, which is 10x as long as it would be the short way.


.

Re: Giant Wimshurst Machine - could use some guidance
Antonio, Sat Aug 09 2014, 02:00AM

Thank you for the updates. About interactions between "regular people" and Wimshurst machines, what I can say is that they will break it in little time because most people don't know how to turn a crank. I would keep the machine in a sealed enclosure, dry and clean, and drive it indirectly through a very solid crank, connected to the machine by some method that limits the force applied, the speed, the direction, and the time. A possibility is to use a fake crank that actually causes a motor to turn the machine in a controlled way. Other questions that could be better investigated are how to make brushes that don't break nor damage the disks, and a driving system without cords that slip and soon break.

Re: Giant Wimshurst Machine - could use some guidance
Nik, Sat Aug 09 2014, 03:29AM

A cheap trick for "people proof" cranks is to put a loose belt from the crank to the machine. Over a certain torque the belt will slip, saving the machine.

Re: Giant Wimshurst Machine - could use some guidance
RAJEEV TUTEJA, Sun Aug 17 2014, 01:58AM

well my 36" machine islo ready but i have a problem.
as soon i connect the layden jars all the his his sound and the corona discharge dissappears. without layden its giving me three inch sparks. am trying now with a different layden jar will post pictures in a few hours. what am i doing wrong

Re: Giant Wimshurst Machine - could use some guidance
Antonio, Mon Aug 18 2014, 12:13AM

Probably Leyden jars with excessive leakage. Verify what happens if you first operate the machine without jars, and while it is sparking connect one of the jars to a terminal.

Re: Giant Wimshurst Machine - could use some guidance
Newton Brawn, Wed Aug 20 2014, 01:31PM

Hi Rajeev,

We are haappy to see your machine, let us see your pictures .

Regarding the capacitors tell us what materials and dimensions you have.

Regards

Re: Giant Wimshurst Machine - could use some guidance
RAJEEV TUTEJA, Thu Sept 04 2014, 08:20PM

some photos attached am getting 6-8 inches spark using 40mm dia and 1 1/2 foot layden jars.
would like to increase the spark lenght. any suggestions are welcome.
thanks and oblige. WATCH VIDEO AT YOU WILL NOTICE THAT I AM SPINNING AT ABOUT 30 RPM my seven inch wheel driving 2 inches boss heads
anysugessions and improvements will be highly appreciated.
thanking you and oblige
regards
RAJEEV TUTEJA

Re: Giant Wimshurst Machine - could use some guidance
Hazmatt_(The Underdog), Fri Sept 05 2014, 02:47AM

That is a really great looking machine you have there!
Post some pictures!

Re: Giant Wimshurst Machine - could use some guidance
Tony Matt, Fri Sept 05 2014, 05:15AM

Hi Rajeev !

Your machine is so nice !!
Congratulations

I have understand that you have said that the acrylic disks have 12" WOOD DISKS, (the wood disks provide a shoulder to the acrylic discs)

I suspect that the wood disks limits the voltage of the machine. Is it possible reduce this wood disks to 6" or Less ?/

Regards

I also suspect some corona inside the capacitor dielectric that limmits the spark lenght. Do you mind to show us a sketch of the capacitors, with specs of the materiasl ?

Someone has a suggestion to increase the lenght of spark ?

Re: Giant Wimshurst Machine - could use some guidance
RAJEEV TUTEJA, Fri Sept 05 2014, 08:31AM

dear tony and hazzmatt
here are some pictures. i have reduced the size so they not come out very nice if you enlarge them.












you can see some other layden jars laying on the table in the last two pics

maybe if you like i will upload 2-3 videos on you tube

dear newton,
i tried four different types.
1. PVC pipe used in electrical fittings in homes dia 40 mm, length one and a half foot, spark 6-8 inches with a bang like a shotgun. 120 decibles at 6 foot to be exact, and the light as i have posted in video on youtube shot in broad daylight at afternoon with the sun on top of my head. at night it looked like a welders arc illuminating area upto 100 meters.
. -do- dia 70 mm spark 7-9 inches a litter louder sound and brighter light.
3. pvc jar 6"H*4" base inside outside aluminium foil .4 mm thick result same as 1
4. -do- "h*5" base result same as 2.

by the way the layden jars no. 1& 2 were filled with pure aluminium fine cuttings precured from chemicals dealer used in chemical labs.a brass rod was then inserted into them. if anyone wants i can draw its diagram in coreldraw and post on this forum with complete instructions to make them. but it will take me a week to post them as i am going to mumbai and pune for a few days.
jars no. 2 and 3 with al. foil inside and out with a chain in the jar type of laydens

dear tony,
sorry i forgot to metion you in my last post.
the wooden disks were made up of dried heat fire and water proof plywood as used in high end furniture so i dont think there was any leakage due to them.
regarding your second question i will surely provide complete details but please give me some time.

TILL NOW NO SUGGESTIONS FOR IMPROVING SPARK LENGTH.

any suggestions will be highly appreciated
thanks to all of you out there
regards
RAJEEV TUTEJA

Re: Giant Wimshurst Machine - could use some guidance
Tony Matt, Fri Sept 05 2014, 09:49PM

Ya,

The corona inside the jars may be seen with a small mirror and dark roon.

The dark room will allow you see any eventual corona with all machine running.

To check the insulation your plywood you may connect a piece of plywwood between the alive terminals of the jars and sse a reduction in the spark lenght.

Wath is the thickness of the pvc insulation in th jars ?
Are the armature (external aluminun electrode conected by a solid wire or by the wood base?

Maybe you try use 4 jars connected in series and see the spark length.

Regards

Re: Giant Wimshurst Machine - could use some guidance
Hazmatt_(The Underdog), Fri Sept 05 2014, 11:46PM

The only thing that I can think of is to lower dissipative losses. The wood is going to act like a very large resistor, especially on a moist day, so getting the wood sealed while very dry may be something to look into. Also, if the wood is being used as an insulator, that may have to be changed for plastic.

very pretty machines!

Re: Giant Wimshurst Machine - could use some guidance
Antonio, Sat Sept 06 2014, 01:16AM

The wood disks at the centers surely cause leakage. You could use acrylic, or HDPE (cutting boards) instead of wood with the same mechanical function.
The thin bars of the charge collectors around the disks cause corona, and more leakage. Use thick tubes there, that can also be wood parts with wires inside. Look at other conductors connected to the terminals. They shall be always thick, without points or sharp corners.
I am not sure of the effect of those triple-ball terminals. I like to use double balls, with the smaller ball with diameter around 1/8 of the desired spark length, and the bigger ball two times or more larger.
Arrange the terminals so the positive terminal is inclined in the direction of the negative. This produces the longest spark length. It is easy to find what is the positive, since if you incline the negative terminal in the direction of the positive only small sparks can be obtained.
The Leyden jars must have metal foil inside and outside. The connection to the inner terminal may be anything that produces a good contact with the internal foil. Chains may be not the best option. The connection between the outer foils must be good too. If you use tubes, the bottoms of the tubes must be solidly sealed, and this is not easy. A plastic plug fixed with hot glue may work.

Re: Giant Wimshurst Machine - could use some guidance
RAJEEV TUTEJA, Sat Sept 06 2014, 03:46AM

DEAR TONY, HAZMATT, ANTONIO

the machine has already been sent to the the customer for approval.
he wants 10 -15 pcs of these. am leaving today to Mumbai (Bombay) to reassable it there, as you can see in the attached photos, many things were taken off for portability, easy, and safe transportation. Mumbai is about 1800 Kms. from Ambala Cantt where i am situated.
Thanks to all of you for your suggestions will try there.
thanks once again but keep posting more suggestions they are needed all the time.
regards
RAJEEV TUTEJA

Re: Giant Wimshurst Machine - could use some guidance
Tony Matt, Sat Sept 06 2014, 09:21PM

Hi Rajeev !

I am happy you already made a nice machine, and you got the oportunity to improve the design as much you want .

Cheers

Tony