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Re: [VanDeGraaffGenerator] Re: van de graaff sphere

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  • Elmer Wiersma
    I will keep everyone posted when I make some progress elmer ... From: Richard R. Linder To: VanDeGraaffGenerator@yahoogroups.com Sent: Monday, October 31, 2005
    Message 1 of 12 , Nov 1, 2005
      I will keep everyone posted when I make some progress
      elmer
      ----- Original Message -----
      Sent: Monday, October 31, 2005 10:15 PM
      Subject: Re: [VanDeGraaffGenerator] Re: van de graaff sphere

      Ok Elmer, sounds like you have many resources at the university. Keep us posted, it's an interesting project.
       
      Dick
       
      ----- Original Message -----
      Sent: Monday, October 31, 2005 3:28 AM
      Subject: Re: [VanDeGraaffGenerator] Re: van de graaff sphere

      Dick
       
      yes I know it will be quite a challenge. I know that the pressure on 1 square meter will be 1000 kilogram (about 2200 pounds) if there is no pressure on the other side. it needs to be quite a strong structure. well for an acceptable vacuum would be something about 1/1000 or 1/2000 of atmosferic pressure but if the structure can resist that pressure, it may be not a real vacuum but I need to be able to construct it. maybe I can get my hands on some of that insulating gas they use for the commercial VDG, I am a student on a university so maybe they have some sort of that gas there. I know they have a lot of different gases in store. at the university they also have numerous vacuum machines, that are probably quite strong because they also run scanning electron microscopes (SEM) there. well maybe I don't get 1 megavolt on each terminal but it will sure be pretty high, 300 kilovolt is the minimum I want. That should be well within my reach I think.
       
      thanks for all the replies
      Elmer
    • ben_englund
      Is a there a reason why you don t want to use some metallic pipe or cylinder of appropriate size for your terminals instead of boxes? It should take tha
      Message 2 of 12 , Nov 28, 2005
        Is a there a reason why you don't want to use some metallic pipe or
        cylinder of appropriate size for your terminals instead of boxes? It
        should take tha vacuum better I would think.

        Ben Englund


        --- In VanDeGraaffGenerator@yahoogroups.com, "Elmer Wiersma"
        <elmer.wiersma@f...> wrote:
        >
        > thanks for the info dick and
        > I plan to make the outside of the box vacuum so where the charges
        > collects on the surface but not the inside, I know that can be
        trouble
        > with ceiling the inside of the box from the outside but I will give
        it
        > a try, so the belt will not be operating in a vacuum well maybe in
        a
        > box of it's own with low humidity but the 2 outsides of the 2 boxes
        > will be separated from the rest of the machine. I have connected
        the
        > motor directly to the driver pulley shaft. but if I think what you
        are
        > trying to say about the VDG from MIT is that if you try to get an
        > alternating current in the sphere directly from a electricity cable
        it
        > won't work. maybe I could redesign my plan and have the driver
        pulley
        > connected via chains/belt to the driving motor outside of the
        > box/sphere. i have included a link (below) to an image I maked to
        show
        > exactly what I mean.
        >
        > http://home.tiscali.nl/iftts/vdg/vdg_drawing.jpg
        >
        > Elmer
        >
      • Elmer Wiersma
        No there is no reason why I can t use a metallic pipe, but the problem is where do I get a pipe that is big enough to get at least 300 kV and I would like to
        Message 3 of 12 , Nov 28, 2005
          No there is no reason why I can't use a metallic pipe, but the problem is where do I get a pipe that is big enough to get at least 300 kV and I would like to have 1MV. In the US it is probably easy to by something like that but here (the Netherlands) it is not, it was even hard to find some thin sheet aluminum. I wanted to use sheet aluminum that is 0.2 millimeters thick that is about 0.0008 inch and without any reinforcement it would certainly implode. I also looked it to the option of buying some SF6 because it is a good insulator and so no vacuum is required. But it was extremely expensive just 0.2 kg (0.5 pound) at a pressure of 23 bar of the stuff would cost 300 euro's (240 US Dollars). Just for some fun it is to expensive. Spheres are a major problem to because the biggest bowls I could get here were 7 inches in diameter, it was impossible to find anything bigger that wasn't way over the top in price. I life in a retarded country :(  What I could do is make a cylinder shape out off the aluminum sheet and make a wooden frame on the inside to support it. I would have to think about the design because the standard aluminum sheets here is 40x80 inches and I want to maximize surface so I can get the largest possible surface for the highest possible voltage and so I don't waste a lot of aluminum. Well I will give it a try tomorrow, if I could design something like that.
           
          Elmer
          ----- Original Message -----
          Sent: Monday, November 28, 2005 8:56 PM
          Subject: [VanDeGraaffGenerator] Re: van de graaff sphere

          Is a there a reason why you don't want to use some metallic pipe or
          cylinder of appropriate size for your terminals instead of boxes?  It
          should take tha vacuum better I would think.

          Ben Englund
           
        • ben_englund
          Here in the US, I probably wouldn t even have to buy a cylinder that size, I would just find something at the local transfer station(aka dump). Americans
          Message 4 of 12 , Nov 28, 2005
            Here in the US, I probably wouldn't even have to buy a cylinder that
            size, I would just find something at the local transfer station(aka
            dump). Americans throw everything away. Thats where I get most of
            my materials. I'm sure I wouldn't have to wait too long for a large
            stainless cylindrical tank to appear. A sphere is a little harder to
            find, though.


            I could be wrong, but I believe you would be better off making the
            cylinder shapes as apposed to making cubes. curved surfaces are much
            stronger than flat ones.

            Good luck

            Ben Englund





            --- In VanDeGraaffGenerator@yahoogroups.com, "Elmer Wiersma"
            <elmer.wiersma@f...> wrote:
            >
            > No there is no reason why I can't use a metallic pipe, but the
            problem is where do I get a pipe that is big enough to get at least
            300 kV and I would like to have 1MV. In the US it is probably easy to
            by something like that but here (the Netherlands) it is not, it was
            even hard to find some thin sheet aluminum. I wanted to use sheet
            aluminum that is 0.2 millimeters thick that is about 0.0008 inch and
            without any reinforcement it would certainly implode. I also looked
            it to the option of buying some SF6 because it is a good insulator
            and so no vacuum is required. But it was extremely expensive just 0.2
            kg (0.5 pound) at a pressure of 23 bar of the stuff would cost 300
            euro's (240 US Dollars). Just for some fun it is to expensive.
            Spheres are a major problem to because the biggest bowls I could get
            here were 7 inches in diameter, it was impossible to find anything
            bigger that wasn't way over the top in price. I life in a retarded
            country :( What I could do is make a cylinder shape out off the
            aluminum sheet and make a wooden frame on the inside to support it. I
            would have to think about the design because the standard aluminum
            sheets here is 40x80 inches and I want to maximize surface so I can
            get the largest possible surface for the highest possible voltage and
            so I don't waste a lot of aluminum. Well I will give it a try
            tomorrow, if I could design something like that.
            >
            > Elmer
            > ----- Original Message -----
            > From: ben_englund
            > To: VanDeGraaffGenerator@yahoogroups.com
            > Sent: Monday, November 28, 2005 8:56 PM
            > Subject: [VanDeGraaffGenerator] Re: van de graaff sphere
            >
            >
            > Is a there a reason why you don't want to use some metallic pipe
            or
            > cylinder of appropriate size for your terminals instead of
            boxes? It
            > should take tha vacuum better I would think.
            >
            > Ben Englund
            >
          • Elmer Wiersma
            Thanks Ben and Craig for your advice on the matter, it is really helping, because I don t know very much about the voltage generated by a VDG. It also saves me
            Message 5 of 12 , Nov 29, 2005
              Thanks Ben and Craig for your advice on the matter, it is really helping,
              because I don't know very much about the voltage generated by a VDG. It also
              saves me money and from buying stuff and then figuring out it doesn't work.

              Well dick said that if i create a vacuum the charp edges won't matter (at
              least I think it was what he was trying to say). Well vacuum is on it self
              pretty difficult.

              I am looking for some old disused propane tank, it is large and has a big
              curve on the ends. If I can cut the tank in two I would have a perfect
              terminal (I think). Propane tanks are a little bit hard to get because
              almost everything here is recycled. Even old small propane tanks (the patch
              them up and use them again).

              All other cilindrycal stuff like fire extinguishers could work but maybe
              they are to small. I will probably reconsider my idea about a box and look
              for something that is more sphere like or cilinder shape. There is a
              workshop on the first floor at my university maybe they know something or
              can create something out of aluminum that would suit my need.

              Elmer

              ----- Original Message -----
              From: "Craig Fuller" <cbfull@...>
              To: "Elmer Wiersma" <elmer.wiersma@...>
              Sent: Tuesday, November 29, 2005 7:28 PM
              Subject: Re: van de graaff sphere


              > I'm not sure I understand. If you are trying to achieve a higher
              > voltage on your terminal, the size of the terminal is not the issue,
              > the key is to minimize the number of sharp points. A very large
              > sphere is essentially a really, really dull point (or "not sharp").
              >
              > For example, the tip of a needle might have a radius of curvature of
              > a few microns, while a VDG sphere will be much, much larger. Am I
              > making sense?
              >
              > What I mean is, you want to reduce the amount of sharp points on
              > your terminal to as low as possible. If you make a square box, you
              > will have VERY, VERY sharp points AND edges where the charge will
              > leak off, and you will not get the voltage you are trying to
              > obtain. Unless the corners of the box are very rounded, and the
              > edges as well, the maximum voltage is then determined by the radius
              > of curvature of these parts, in general.
              >
              > If you are just trying to get a very big "charging current", that is
              > another matter. The terminal can be any shape you want, as long as
              > the top collector is INSIDE this terminal.
              >
              > I hope I am helping.
              >
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