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Most bang for your static electric buck

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Coyote Wilde

Thu Nov 08 2007, 01:43AM

Registered Member #175 Joined: Tue Feb 14 2006, 09:32PM
Location: Sudbury, ON
Posts: 111

If anyone has built or experienced both, which is the 'better' static generator, Wimshurst or Van de Graaff?
By better, I mean has the most impressive output in terms of the time and effort gone into building one. I'm right now leaning towards a Wimshurst-type, since I can thus avoid the ubiquitous spherical top load of the VDG.
I should really build both-- and probably will, at some point--but I've got to start somewhere. May as well be at the top.
What I'm looking for is just a cheap, easy, and primarily SAFE HV display. Something you can let rugrats and grandparents (without pacemakers) play with without fear. Any suggestions welcome.

Spedy

Thu Nov 08 2007, 02:23AM

Registered Member #964 Joined: Wed Aug 22 2007, 12:39AM
Location: Stockton, CA
Posts: 134

I would prefer to build a Dirod, they're inbetween a large VDG and a Wimshurst for complexity, but most of them can opperate in the most humid conditions. A. D. Moore's larger Radial Dirod can generate an excess of 90k volts.
You can get his book "Electrostatics Exploring, Controlling, and using Static Electricity" 2nd Editon. It also comes with the ever-so-handy complete Dirod manual. I'm going to build a Radial Junior once I'm finished w/ my SSTC project.

Nik

Thu Nov 08 2007, 02:55AM

Registered Member #53 Joined: Thu Feb 09 2006, 04:31AM
Location: Ontario, Canada
Posts: 638

I think this might be the best bang for your buck.

It's pretty much free to make and seems to give all the charge you could ever want for 0$

Bauerb2

Thu Nov 08 2007, 04:07AM

Registered Member #973 Joined: Tue Aug 28 2007, 07:32PM
Location: Pittsburgh, PA
Posts: 66

a few years back i built a rotating vinyl record brushed by a wool sock that charged a leyden jar built from an Utz pretzel jar. i got some impressive 9" discharges that were incredbly bright and loud.
i wouldnt say its a good display unit though, i had to crank that for about 10 minutes before i could get any sort of spark. It was incredibly dangerous too. after one rotation of the disk, touching the jar with your hand would knock you down. very painful.

i would try for a VDG. there are many guides online on how to make cheap ones from medical tourniquets (sp?), or even rubber bands, and small motors. toploads are a pain to find or build. i just used something round covered in alum. tape.

good luck.
-Andrew

Coyote Wilde

Thu Nov 08 2007, 07:24PM

Registered Member #175 Joined: Tue Feb 14 2006, 09:32PM
Location: Sudbury, ON
Posts: 111

Sorry, Nik, but while cheap and easy, that doesn't really appeal as a presentation piece... The dirod does look interesting, and I like the fact that everyone suggests they do well in low humidity. Humidity is killer.
I haven't gotten my hands on the book, but can you explain, Spedy, why rods instead of just metal plates?

Spedy

Thu Nov 08 2007, 11:58PM

Registered Member #964 Joined: Wed Aug 22 2007, 12:39AM
Location: Stockton, CA
Posts: 134

Err, I'm not sure. Some radial designs just use metal foil strips on the disk instead of rods (like Dirod #8 on

). I think the rods let there me no "cylinder" needed to support metal plates (in the axial design) and round-end rods have much less corona leakage than sharp-edged plates. I don't really know any other explanation.

I would try amazon.com or ordering it from local bookstore. My bookstore doesn;t carry it at all. :(
It is a REALLY handy book and has a bunch of demos and a couple other electrostatic generators.

Ugh. The only reason I don;t have a dirod sparking away right now is because the local plastics place doesn;t carry plain old 1x1' sheets... Oh well, I'll have to call to get more info.

Antonio

Fri Nov 09 2007, 12:37AM

Registered Member #834 Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644

A Wimshurst machine is far superior to a Dirod of the same size. The Dirods tend to revert polarity if the voltage gets high, and so never reach very high voltages. The Wimshurst machine never reverts polarity. Any of these machines will perform poorly if the humidity in the air is high (high means >70%). A Van de Graaff produces greater voltage easily, but the unipolar, low current output limits what can be done with one.
A regular 30 cm Wimshurst machine with a pair of 100 pF Leyden jars can easily produce one or two bright 12 cm sparks per turn of the crank. A VDG with a 30 cm terminal produces slightly longer sparks to a grounded object (easier if the terminal is negative), maybe at the same rate, but they are almost invisible.

Spedy

Mon Nov 12 2007, 11:36PM

Registered Member #964 Joined: Wed Aug 22 2007, 12:39AM
Location: Stockton, CA
Posts: 134

Well, you could aways make the dirod separately-excited. You basicaly make a tiny version of the original dirod on the same axle, and use the output from THAT smaller one to provide power to the inductors on the origional machine. No polarity reversal, and higher than normal current output at lower voltages.

DrZoidberg

Tue Nov 13 2007, 01:24PM

Registered Member #350 Joined: Mon Mar 27 2006, 05:14PM
Location:
Posts: 106

Which of the two is easier to build depends on the availability of materials like e.g. do you know a shop that sells metal spheres?
You can get an impressive output with both. A VDG makes longer sparks. A Wimsurst makes more sparks.
You can attach a layden jar to both devices to get really loud and impressive sparks but I wouldn't call that safe.
Since it has to be safe for children you have to leave out any layden jars which means the sparks will be relatively faint with both devices.
I would go with a VDG simply because you can do the famous hair rising demonstration with it plus it works more reliable in high humidity.
But the best option is of course to build both.

Antonio

Tue Nov 13 2007, 01:33PM

Registered Member #834 Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644

Spedy wrote ...

Well, you could aways make the dirod separately-excited. You basicaly make a tiny version of the original dirod on the same axle, and use the output from THAT smaller one to provide power to the inductors on the original machine. No polarity reversal, and higher than normal current output at lower voltages.

This may work if you build the driving machine without spark shields (the insulator plates separating the inductor plates from the rotating part). The shields are the cause of the polarity reversals, but without them the machine eventually sparks trough the neutralizers and discharges. The big machine, if built with spark shields, will quickly accumulate charge on the shields and operate with reduced output. Maybe it can be built without shields, relying only on increased distances to avoid sparking. Or a rotating shield, rotating slowly, can be mounted around the rotor.

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