Van der Graaff Generators!

Helpful tips on how to make them.

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Fast-Forward! Failure and Lessons

So I almost completed my Van de Graaff Generator. I say almost because it’s not technically put together, but I still have to go back about 60 steps, so I can get back on track. Let’s talk about it.

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Here is what I had going. I have an aluminum rod on top, and a teflon-tape wrapped motor on the bottom. They are connected via exercise band, and besides a loud rattling, they run fine. The dome is placed to the side, and i feed the top brush in to it, to test out the effectiveness of the motor assembly before I work on placing the dome on top. I have a grounded source near the bottom. What happens when I run it? Well for all of 30 minutes I had a working generator, it was slow, and needed tweaking, but I was getting shocked and have a charge detector video to prove it.

However. Out of the blue it ceased to work, and I surmised that it was most likely fault of the brushes (I’m just using fray copper wire). In many more professional generators they have stiff pins that are expertly placed. In my design, i can’t very well see the bottom roller, let alone place a brush near it.

Also my Bottom roller is a little thin, and I read from an old 1900s physics lecture that a thin roller can mean the belt is not in contact with the roller long enough to build a charge, or the charge is lost before the belt when moves to the next roller.

I have not given up, I am very well prepared to try again. Mentally at least. As far as materially, i need to rebuold the tower with new rollers, and create a better brush system to pull charge off the rollers.

Will continue posting on the building process before and after my current position soon.

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“Tribo-a-what?” Triboelectricity and You

Seeing how it’s the name of the website, I’m sure you’ve seen the word before, but what is it? What is it responsible for? and How can it be used to create a rattling sphere of electricity capable of storing thousands of volts of electricity? All very good questions, and are important to cover before we delve into the rollers.

Triboelectricity is why static electricity occurs. When you accidentally shock your pet after pulling a blanket around yourself, or the doorknob shocks your hand as you reach for it, it’s because you built up a charge. That charge was created by certain materials on you, coming into contact with other materials. To be more specific, when you rub a blanket across your back, it will sometimes stick, or even make popping sounds from the static electricity. When you walk across a carpet towards the door, your shoes on the carpet build up a charge.

Certain materials build up a charge by touching other materials. A common example in science is to rub a glass rod with silk. Glass and Silk are two materials that create charge when they come into contact with one another. If you were wearing silk, and you rubbed yourself all over a glass window, you’d likely get a shock when you touched a door knob. Other materials exhibit the same effects, like wool and cotton.

The charge is created because when the two objects come into contact, the electrons in one jump over the the other material. When you break contact, there is a charge imbalance. Certain materials create more static charge when they come into contact.

This is where the Triboelectric series comes in. Wikipedia, AlphaLab and Siliconfareast all have very up to date triboelectric series. How the series works is that the further away two objects are from each other, the more charge imbalance occurs when they come into/and break contact. Take for example Nylon and Teflon. On all three series, they are almost as far apart as they can be. These means that they will build a lot of charge quickly by coming into contact with one another. It also means that in general, they will create more charge with the other triboelectric things they come into contact with.

 

These materials are important to know about when choosing the materials for our rollers, coming up later, because if we are essentially building up a static charge automatically, if we use two very triboelectric objects, we’ll get a greater charge.

Let’s talk Motors

Motors, as you hopefully recall, are one of the most important aspects of a generator. Guides I’ve seen online are split between people using little motors for tiny generators, to people who buy very nice, and unfortunately fairly expensive motors. I was in a position where I wanted a motor that was decently sized, but nothing fancy, nothing expensive. I got the idea when watching this youtuber’s videos to repurpose the motor from an old fan.

We have a lot of these fans in my house because it gets hot in the summer, and without A/C, these fans are necessary. But they’re cheap, and they break often. I had one that had its legs broken, so i tore it apart and pulled out the motor.

 

 

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The nice thing was the motor already had a plug and switches on it that I could put into any wall socket. Not everyone has junk motors lying around, but before you throw your hands up declaring you don’t have a motor, really think about where one could be hiding that you can use.

So now I have this motor here, it’s decent at spinning, and I wrapped it up in non-conductive electrical tape just to be sure it doesn’t electrocute me. If you’re struggling to find a motor, you can always buy one of these cheap fans and tear it apart. If you just want a temporary solution that costs nothing, if you have a drill, or and sort of motorized tool ,you could find a rod to attach to it, and just use the tool as your motor.

Some motor’s require more work than others, like mine pictured above, i had to cut off a protruding metal piece, and then sand down what metal i couldn’t cut off, took a good amount of work, which is good.

Starting the project, The Dome.

So after preliminary research I started my Van de Graaff Generator. The basic parts that seemed necessary were

  • The Collector (Usually a Metal Dome on Top, people also uses soda cans, or even cooking pots)
  • The Belt (A material like rubber or latex that is hooked on to two pulleys, and is rotated around them)
  • The Pulleys (Two rods of differing materials,  these two materials need to create a static build up with the belt)
  • The Brushes (Metal combs that have pointed ends, they are what carry the charge)
  • The Motor (A motor, that is used to rotate the pulleys, transferring charge via the belt)

After finding that, the most odd and difficult to obtain object seemed like the Collector (I don’t just have metal domes lying around). So I decided it would be the first thing I look for, and I would go from there. I had seen that people have used many different things for collectors, like cans, and even cooking pots! It shouldn’t be a big stress what the collector is, and in my case, I live pretty close to an Ikea, so I bought these metal salad bowls!

If you have browsed around Van  de Graaff Generator guides, these bowls come highly recommended. You can’t buy them online, so I called my store and asked them if they had them and they did! Here are some pictures of them.IMG_0399

If you can’t get a hold of these, really, a soda can works fine. I count myself lucky, but they’re only as good as the generator they sit atop of, so there’s that.

My plan is to somehow create a hole in them, but i first made them into a dome with some electrical tape. What i did here was sketch a circle of the rim of the bowl, so i could then set the other bowl on that sketch. I checked the make sure the two bowls would line up (I had to squash and slightly bend one of them). And even after that i had to get some help to hold the bowls together so I could tape the seam between them.

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Van de Graaff Generators

What is it about Van de Graaff Generators that is so appealing? Their operation seems magical, so far removed from the behavior of electronics we interact with normally. Everyone’s felt the surprising shock of static electricity after shuffling across a carpet on a dry day, it’s normally an unpredictable, and unremarkable event not to be remembered for long.

Then you find a machine that seemingly automates that process. Automates it to the point that it buzzes and cracks, and the spectacle it creates, one usually reserved for the clouds, can be wielded freely for apparently the same reasons that petting my cat on a dry day turns into a shocking assault.

The average static shocks a person generates are not exactly the same as those generated by a Van de Graaff generator, the generator is set up in a way that exploits that phenomena, but such a device still triggers a deep yearning for understanding in me. An intimate facet of the physical world, and our interaction with it is revealed by our understanding and use of static electricity. It is for this reason that I intend on pursuing these generators, so that I may learn about them, and hopefully help others do the same.

Here on triboelectricity.wordpress i will catalog my creation of Van de Graaff generators in a way that I can help teach others to do the same, as well as catalog my learning of these remarkable machines.

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