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VDG belt

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  • ceeawf
    Hi all, I m struggling to find the words to describe how the belt affects the VDG output. What materials on the triboelectric series make the best belts? My
    Message 1 of 4 , Jun 2, 2004
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      Hi all,

      I'm struggling to find the words to describe how the belt affects the
      VDG output. What materials on the triboelectric series make the best
      belts? My gut feeling tells me it should be mid way between the
      position of the two rollers.

      any help appreciated,

      Allan.
    • colt45hal@aol.com
      ALLAN: In my two commercial VDG machines, Dental Dam is used as a belt material with charging rollers of polyethylene and collecting rollers of solid
      Message 2 of 4 , Jun 2, 2004
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        AOL Email
        ALLAN:
         
        In my two commercial VDG machines, "Dental Dam" is used as a belt material with charging rollers of polyethylene and collecting rollers of solid aluminum. These machines were made by Science First, of Buffalo, New York.  My large homemade VDG "Prometheus" uses a neoprene belt with a charging roller of PVC (over a wood core) and a collecting roller of aluminum pipe (over a wood core).  It works fine!
         
        In addition to triboelectric concerns, one must also be concerned with physical parameters, such as elasticity, thickness, belt speed, belt width (the last two determine current), and availability and cost. I had to order my 5" wide, 1/16" thick, 12 foot long Neoprene belt from a belting company.  I spliced it using a 30 degree splice, which produced a seam 10 inches long. 
         
        Listen to Dick concerning this subject, too!
         
        StaticDude HAL
         
         
         
         
      • ceeawf
        Thanks HAL, I got my belt from www.durabelt.com, it is Polyurethane. It works well. but its just for my thesis, i never investigated any others. I have
        Message 3 of 4 , Jun 2, 2004
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          Thanks HAL,

          I got my belt from www.durabelt.com, it is Polyurethane. It works
          well. but its just for my thesis, i never investigated any others. I
          have investigated the current output, i was just wondering how, say,
          a positive belt would work with negative lower and a neutral upper
          roller?

          I've only got a week left, but there are so many questions that keep
          popping up! If anyone would like a look at my finalised thesis i'd be
          more than happy to mail a copy somehow. U guys are definately in the
          acknowledgements!

          cheers,

          allan




          --- In VanDeGraaffGenerator@yahoogroups.com, colt45hal@a... wrote:
          > ALLAN:
          >
          > In my two commercial VDG machines, "Dental Dam" is used as a belt
          material
          > with charging rollers of polyethylene and collecting rollers of
          solid aluminum.
          > These machines were made by Science First, of Buffalo, New York.
          My large
          > homemade VDG "Prometheus" uses a neoprene belt with a charging
          roller of PVC
          > (over a wood core) and a collecting roller of aluminum pipe (over a
          wood core).
          > It works fine!
          >
          > In addition to triboelectric concerns, one must also be concerned
          with
          > physical parameters, such as elasticity, thickness, belt speed,
          belt width (the last
          > two determine current), and availability and cost. I had to order
          my 5" wide,
          > 1/16" thick, 12 foot long Neoprene belt from a belting company. I
          spliced it
          > using a 30 degree splice, which produced a seam 10 inches long.
          >
          > Listen to Dick concerning this subject, too!
          >
          > StaticDude HAL
        • Dick Linder
          Allan: I can relate some experience and theories regarding belts: You are trying to charge a capacitor (the sphere) that by it s very nature has some leakage,
          Message 4 of 4 , Jun 2, 2004
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            Allan:

            I can relate some experience and theories regarding belts:

            You are trying to charge a capacitor (the sphere) that by it's very
            nature has some leakage, hopefully small. Therefore it stands to
            reason the logic of a conveyor belt is valid...wide and fast. Of
            course there are limitations to both of these parameters. Width of
            course limited by the physical design. Speed is limited by the
            behaviour of the belt as the speed is increased. Stretchy belts will
            elongate and at certain speeds, will go into oscillation and the two
            inside surfaces, one (+) and one (-) will be attracted and touch thus
            screwing up the efficiency of charge delivery. Some tabletop
            commercial VDGs suffer from this but still seem to deliver enough
            charge to be satisfactory.

            In my first VDG I have experimented with different thicknesses of
            amber latex (dental dam), .025" black rubber, .030" white
            neoprene, .003" frosted mylar (no stretch) and .032 black neoprene
            (no stretch). The "no stretch" materials did not go into oscillation
            and touch, even at speeds of 60mph. The other materials worked but at
            lower speeds resulting in lower charging currents. The mylar and
            neoprene under ideal conditions provided up to 50uA as compared to
            20uA for the others. If you are charging a small sphere then the
            limitations of the stretchy stuff do not apply since you can run the
            belt at lower speeds. My 2nd VDG will require maximum charging
            current due to the 30" sphere so my choice of belt will be either no
            stretch neoprene or mylar. Performance will be the deciding factor.

            Regarding relative position on the triboelectric list:

            I have not seen a lot of discussion regarding the importance of the
            position of the belt on the tribo list. Of course one requirement is
            that it charges the bottom roller either (+) or (-) so obviously the
            roller and belt cannot be of the same material. If the bottom roller
            becomes (+) you will transport (-) charges to the top and the sphere
            will suck these charges off the belt by way of the collector points.
            This will happen with a neutral metal roller at the top. Personally I
            think the belt may not be stripped of all charges and it will descend
            with some residual (-) still stuck to the belt. It is for this reason
            I am using a PVC roller at the top. The roller will become charged
            (-) and repel (-) charges off the belt and into the collector
            points. I think the belt material should be roughly in between the
            top and bottom roller material if the top roller is something other
            than neutral. FYI, my mylar belt is neutral and at first glance works
            approximately as good as the neoprene.

            Considering your example of a (+) belt and a (-) lower roller and a
            neutral upper roller. I'm not sure if that's the most efficient
            combination even though it might work. To illustrate how spooky the
            belt can be....I bought some "frosted" mylar that is used by
            architects and illustrators to draw on. According to the tribo list
            it was neutral. Performance was outstanding. One drawback was that
            the largest piece available was 36" x 36" so the belt had several
            splices. My friend was experimenting with making player piano rolls
            and had purchased a roll of clear mylar 36" wide x 300 ft long. He
            gave me a long piece and I was able to make a belt with only one
            splice. WOW! Sure, it didn't work worth poop! 0.0uA at 60mph.

            I discovered the cure....using my palm sander, I frosted the outward
            face of the belt and it then worked the same as the first mylar belt.
            Go figure!

            Barring any revelations, my VDG #2 will have a PVC top roller, a
            mylar or neoprene belt and a nylon bottom roller. The nylon roller
            will be interchangeable with a metal roller to give me the
            alternative of running "pumped" mode with a 10Kv power supply.

            Hope this helps a bit with the thesis. You should copy-paste it to
            this forum so we all can enjoy the fruits of your labor.

            Good luck!

            Dick






            --- In VanDeGraaffGenerator@yahoogroups.com, "ceeawf"
            <allan_fairbairn@h...> wrote:
            > Thanks HAL,
            >
            > I got my belt from www.durabelt.com, it is Polyurethane. It works
            > well. but its just for my thesis, i never investigated any others.
            I
            > have investigated the current output, i was just wondering how,
            say,
            > a positive belt would work with negative lower and a neutral upper
            > roller?
            >
            > I've only got a week left, but there are so many questions that
            keep
            > popping up! If anyone would like a look at my finalised thesis i'd
            be
            > more than happy to mail a copy somehow. U guys are definately in
            the
            > acknowledgements!
            >
            > cheers,
            >
            > allan
            >
            >
            >
            >
            > --- In VanDeGraaffGenerator@yahoogroups.com, colt45hal@a... wrote:
            > > ALLAN:
            > >
            > > In my two commercial VDG machines, "Dental Dam" is used as a belt
            > material
            > > with charging rollers of polyethylene and collecting rollers of
            > solid aluminum.
            > > These machines were made by Science First, of Buffalo, New York.
            > My large
            > > homemade VDG "Prometheus" uses a neoprene belt with a charging
            > roller of PVC
            > > (over a wood core) and a collecting roller of aluminum pipe (over
            a
            > wood core).
            > > It works fine!
            > >
            > > In addition to triboelectric concerns, one must also be concerned
            > with
            > > physical parameters, such as elasticity, thickness, belt speed,
            > belt width (the last
            > > two determine current), and availability and cost. I had to order
            > my 5" wide,
            > > 1/16" thick, 12 foot long Neoprene belt from a belting company.
            I
            > spliced it
            > > using a 30 degree splice, which produced a seam 10 inches long.
            > >
            > > Listen to Dick concerning this subject, too!
            > >
            > > StaticDude HAL
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