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I Problems Building a Van De Graaff Generator

  1. Jul 14, 2016 #1
    I have been trying to build a small Van de Graaff generator based on the designs found here: http://rimstar.org/equip/build_make_van_de_graaff.htm

    Unfortunately I haven't been having much luck. How can I improve it?
    https://scontent.fsnc1-1.fna.fbcdn.net/t31.0-8/13692923_587926388052702_8808151424123490542_o.jpg

    The body was 3D printed using PLA plastic.
    It encloses the rubber band belt completely.
    https://scontent.fsnc1-1.fna.fbcdn.net/t31.0-8/13735540_587926381386036_2540663988244643720_o.jpg

    The bottom motorized roller is made PCV electrical tape and a slice of PVC tubing:
    https://scontent.fsnc1-1.fna.fbcdn.net/t31.0-8/13698065_587926361386038_7472904692042366737_o.jpg

    The top roller is made of nylon thread:
    https://scontent.fsnc1-1.fna.fbcdn.net/t31.0-8/13680297_587926378052703_6114147970296557842_o.jpg

    The rubber band is one of those used to hold together vegetables from the supermarket.
    The configuration is shows below.

    https://scontent.fsnc1-1.fna.fbcdn.net/t31.0-8/13723871_587926374719370_906130344536881567_o.jpg


    I have used many combinations of many materials for each part. I have tried using steel drinking cups and silver cups for the metal domes. I have tired thick, and thin rubber bands fro the belt, as well as balloon rubber for the belt. I also tried multiple materials for the motorized roller, including only teflon tape, only PCV electrical tape, and the current design with the PCV piping.

    The generator does work, as I have measured potential differences between the two cups using a multimeter, but it doesn't create arcs. Do I need to insulate the metal better?
     
  2. jcsd
  3. Jul 14, 2016 #2

    1oldman2

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    Gold Member

    Is the top pulley shaft riding on some sort of bushing or bearing? Would/could a vacuum cleaner drive belt be used in place of the rubber band? I'm not sure what the brush/pickup consists of but that might be crucial to generating more power, These are just thoughts that initially crossed my mind, I imagine someone with more knowledge will be giving an opinion before long. As an afterthought this might have been better placed in "electrical engineering" thread, I'm curious to see how this works out. Something along the lines of a flag pole cap ball might be the shortest route to your dome problem.
     
  4. Jul 15, 2016 #3

    tech99

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    Gold Member

    Do you have a metal sphere for the top. This seems important. The machine I use has a metal top roller and also some thin metal pick up brushes. I think the two rollers must be different material according to the electro static series. My roller is inside the top sphere.
    With a commercial machine I find it is very important that there is a perfect smooth and clean surface everywhere, and I dry everything with a hair dryer. It is also possible the belt is leaky.
     
  5. Jul 15, 2016 #4

    Paul Colby

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    Gold Member

    What is that material for the column? It has to be a really good non-conductor or all your charge will bleed away. For the design you show there has to be a contact potential difference between the belt-lower pulley and the belt-upper pulley. Since the material is the same for the belt the pulleys must be made of different materials. The cheep one of these I bought generates ~100 uA of current which one may measure with an multimeter.
     
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