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Author Topic: how to build a van de graff generator? and suggestions for parts  (Read 7266 times)
septango
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« on: June 29, 2013, 08:46:30 pm »

Im looking to build a van de graff generator for a project Im working on

how do I do that?

 and does anyone know some cheap everyday parts I could use rather than buying actual custom parts?
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« Reply #1 on: June 29, 2013, 10:12:17 pm »

I reckon you could get quite a long way using standard construction kit parts from Lego. Mechanno and the like.

The column needs to be a good insulator, so most lab demo set-ups use acrylic strips or rods.

Tricky bits are going to be the belt to transfer the charge and the dome collector.

The belt is a strip of insulating material that's flexible enough to run over a couple of pulleys.
All the best ones that I've seen have been a light fabric coated in rubber. Maybe you could sow one up out of ribbon and coat it in latex.

The dome needs to be a conductor. I'd be looking at something like a metal lampshade to do this job.

Keep us up to date with how this goes.
We want WIP pictures.
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« Reply #2 on: June 29, 2013, 10:15:27 pm »

perhaps a metal mixing bowl for the dome?
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oldskoolpunk
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« Reply #3 on: June 29, 2013, 10:36:41 pm »

Here's a cute explaination of how one works.

Basically, a van de Graf generator charges up until the charge arcs off or escapes to air. So the goal is to reduce leakage. The dome will leak less if it has no sharp edges or corners. It doesn't have to be a sphere, but it does have to be a smooth curved surface.

As with all static electricity experiments, you can't accumulate much of a charge if there's high humidity.

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ColeV
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« Reply #4 on: June 29, 2013, 11:55:54 pm »

I made one in sixth grade for a science project. We used a large pvc pipe for the stem (you need something insulating) and two metal mixing bowls bolted together for the top. We built a basic wood box with a hinged door for the base. I still have it around if you need more details, though it's a bit buried. I think our rubber band was literally just a strip of rubber we some how attached into a band. There are surely some science fair type instructions out there.
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« Reply #5 on: June 30, 2013, 06:47:07 pm »

I've been looking hard at these for the globe of a generator.


http://m.ikea.com/us/en/catalog/products/art/50057254/

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« Reply #6 on: June 30, 2013, 09:54:19 pm »

Many years ago, I saw instructions in a very old book for a van de graff generator made from a glass bottle, some silk, and rubber pads cut from an old tire; the silk was wrapped around the bottle, which rotated on its axis so that the silk rubbed against the rubber pads and built up a charge. It was a very simple design intended to be build in a home workshop.

I have touched cars while standing on the ground and gotten a static shock. The charge in those cases must have been created by the rubbing of a loose engine belt, and the charge built up because the rubber tires insulated the car from the ground. The car became a van de graff generator by accident.
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Dr cornelius quack
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« Reply #7 on: June 30, 2013, 10:45:31 pm »

Many years ago, I saw instructions in a very old book for a van de graff generator made from a glass bottle, some silk, and rubber pads cut from an old tire; the silk was wrapped around the bottle, which rotated on its axis so that the silk rubbed against the rubber pads and built up a charge. It was a very simple design intended to be build in a home workshop.

I have touched cars while standing on the ground and gotten a static shock. The charge in those cases must have been created by the rubbing of a loose engine belt, and the charge built up because the rubber tires insulated the car from the ground. The car became a van de graff generator by accident.


I think it's more likely that the charge that builds up on a car is due to the friction of the tires against the road. Van der Graffs work by charge separation, so any static that is generated within the car itself would tend to even itself out by flowing through the connected metal parts of the vehicle.

My favorite electrostatic generator is this one:-

http://www.sciencebuddies.org/science-fair-projects/project_ideas/Elec_p069.shtml
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hardlec
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« Reply #8 on: July 19, 2013, 04:23:14 am »

be bloody careful, as a Van de Graf generator can develop enough voltage to act as a defibrillator.  If you don't need a defibrillator, it can also stop a heart.  Static discharges can also fry these new-fangled hand-held Babbage machines, like the Grape or Orange or whatever fruity name they have now...
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« Reply #9 on: July 19, 2013, 05:46:43 am »

Another hazard is that the spark will flow through the most conductive path, so anyone standing nearby will get to see where all your piercings are.
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churchjw
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« Reply #10 on: July 19, 2013, 01:55:29 pm »

Keep in mind that black rubber (like in bike tubes) has graphite in it which is conductive.  The first one I built I used a section of inner tube as my belt, it did nothing.  I have found that exercise bands work well. Here is a random image from the net of the kind of bands I have used http://oatesspecialties.com/images/Exercise%20Bands%20Grouping.jpg  Never tried latex coated cloth.  That sounds like a great idea and could end up looking better.  Whatever you use as your collector at the top try to minimize any sharp corners.  Every seam, point, edge, or bend is an area where you will bleed charge.  In a dark room most of the time you can see the electrons escaping.  I was demoing one for a friend once and we turned off the lights.  You could see this line of charge going down one side.  On closer inspection with the lights on and the machine off I found a hairline crack just where we saw the bleed off.   The other thing I would say is don't put too much in your first one. I spent way too much time trying to find just the right dielectric materials to get the best charge.  I built it tweaked it some then junked it a built a better one.  These things are like potato chips one is never enough.

Jeff
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Not Anumber
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« Reply #11 on: July 26, 2013, 01:23:35 pm »

Would a flat poly V belt such as a modern car's flat serpentine fan belt work ? These get thrown out by car servicing workshops at service intervals so should be easy enough to get hold of free.
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« Reply #12 on: July 28, 2013, 11:01:56 pm »

I'm building my own Van de Graff generator for some time . It is an externally excited generator - it charges the belt not by the triboelectric effect but with a small high voltage power supply . Here are my findings :
  - Ikea salad bowls are perfect for making the top sphere. They can be easily welded together with the TIG welder .
  - you can forget about using any kind of modern transmission belt as the generator belt.  They are made from black rubber containing enough graphite to make them slightly conductive.  I found the pure latex rubber to be the best . Currently I'm using the Thera Band exercise tape  but I'm looking for something thicker.
  - the top and bottom rollers should be barrel-shaped . Otherwise the belt likes to slide to the side of the roller .
  - I found that the easiest method of making the charge collector is to use a piece of conductive rubber which slides on the surface of the belt.

Here is a picture of my generator without the belt and the HV power supply :
Spoiler (click to show/hide)
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« Reply #13 on: July 29, 2013, 02:10:08 pm »

Mr. Consciousflesh nice welds on the bowls.  Its not easy to TIG that thin sheet.  Also that is a great idea for the collector.  What rubber are you using.  I will have to try it.

Jeff
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« Reply #14 on: July 30, 2013, 09:10:48 am »

Thanks . I have a small trick for welding thin sheets - I'm using a piece of the same sheet metal as a filler instead of TIG filler rods. 
Buying conductive rubber in small quantities is not easy . Sometimes you can find it in electronic shops as a material for repairing TV remotes  or as an ESD protection , but I think the simplest method of obtaining it is to buy some large TENS electrodes.
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Wilhelm Smydle
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« Reply #15 on: August 05, 2013, 02:42:25 am »

Would latex tubing work well enough?
In the past I have sanded off the print from PVC pipe for other projects.
It thermal forms well enough for some interesting results.
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von Corax
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« Reply #16 on: August 17, 2013, 08:56:48 pm »

Here's a link to an article in MAKE: #28.

Simple Van de Graaff Generator

(Note the spelling. Don't worry, though; I never get it right either.Wink)

Many years ago, I saw instructions in a very old book for a van de graff generator made from a glass bottle, some silk, and rubber pads cut from an old tire; the silk was wrapped around the bottle, which rotated on its axis so that the silk rubbed against the rubber pads and built up a charge. It was a very simple design intended to be build in a home workshop.


That wasn't a Van de Graaff machine. There was something similar in MAKE: a few years back, but I can't remember which issue or what the machine is called, and I'm away from my library at the moment. :'(

EDIT: Found it. It's called a Ramsden machine, and it appeared in William Gurstelle's Remaking History column in Make #21.
« Last Edit: August 21, 2013, 01:02:21 am by von Corax » Logged

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