Congratulations on your engagement and upcoming wedding. Marrying my
wife was the second best thing that I've ever done, or that has ever
happened to me. I hope your wedding goes great!
I don't think your upper brush will work if you leave it outside the
garden sphere. There is a sheilding effect necessary to get the
charge to leave the belt against the 100 KV potential of the sphere.
Inside a conductive cage, there is no electric field, which lets the
charge leave the belt at leisure. If you don't put the upper roller
inside the sphere, you will at least have to put some aluminum foil
around the inside of the tube enclosing the roller. But if you do
that, I think you'll get massive leakage down the column, especially
if you do the same at the lower roller. I don't think you can get
much over 10 KV if you don't enclose the roller in a Faraday cage of
For belts, I use Theraband brand rubber physical therapy sheets. I
walked into a physical therapy clinic, and asked if they would sell be
a few feet of their thickest, which is blue. They gave it to me for
about a dollar per foot. I cut it into strips 2 inches wide, and
glued the ends together with rubber cement. Paint both surfaces, let
dry for a minute, then press together. Just like contact cement, but
stronger (on rubber).
--- In VanDeGraaffGenerator@yahoogroups.com
> WOW thanks Paul,
> That was way more information then I was expecting. For the collector
> I was going to try and not cut any holes in the garden globe. Using
> epoxy to glue a flange to the globe and then build the brush on the
> flange. So that I could keep as smooth of a surface as possible. I
> do think my rollers are lacking. My one concern is that if the glass
> roller spins at 10,000rpm the glass will shatter due to centrifical
> force. The glass roller is not solid all the way through. The belt I
> know is thick. What else should I use that is thinner. My resources
> are limited. I get very little static build up between the belt and
> roller mateiral but I do get static between the teflon and glass
> rollers though. The last thing is the motor. Either the motor i
> bought at the local hobby town is old or I do not have a good power
> The project is on hold right now. ALl my money is going towards my
> wedding so it may be a while be fore I finish the VDG.
> Thanks for the response.
> --- In VanDeGraaffGenerator@yahoogroups.com, "Paul" <dadguy@>
> > Oracle,
> > Cool project. Nice presentation. I've been tinkering for years,
> > just got my own first generator working this year.
> > Your idea for a garden sphere sounds good. You will have corona
> > problems around the edges of the hole you cut in the bottom. Some
> > folks put a pvc flange under the opening cut in such a sphere, or
> > steel salad bowl like I have. You should get good sparks anyway,
> > if the edges leak a little at first until you get that fixed. I
> > wonder if you could heat the sphere up a little, and get it to
> > melt/embed itself in the pvc, so the edges are hidden by a
> > or so of melted pvc.
> > Have you measured a current yet for your belt and rollers? You
> > at least be able to draw sparks from your brushes. I don't see any
> > brushes in your pics. Anything microscopically ragged, that is up
> > 80 percent the width of your belt should do, including foil. See my
> > pics for one example. Since my heavy foil brushes also have sharp
> > edges sticking out away from the belt, I dont have to attach them to
> > either ground or the sphere. Corona takes care of both connections
> > great! That will not be in keeping with the quality of the rest of
> > your rig, but it will help you get first current and sparks. Next
> > want to check your belt and roller materials for triboactivity.
> > in weak dawn water, and dry first. If you rub the belt on the
> > rollers, do you get crackling, or at least some embarrassing static
> > cling? If not, I don't expect they will work when assembled. Glass
> > is in a good place on the tribo chart, but I wonder if it is so
> > hygroscopic as to ruin its surface properties by attracting a thick
> > film of water. Nylon works well, is cheap and easy to machine.
> > silica gel is just glass with a lot of surface area. Try the
> > test to find out if your glass roller is functional.
> > Your belt looks thick. My thought experimets have me convinced
> that a
> > thicker belt requires higher voltages on the roller to move charge.
> > Higher voltages on your rollers could cause them to lose the charge
> > they need. I suggest you get the thinnest rubber you can, within
> > reason, at least for starters until you know everything is working.
> > Can you cut a large balloon? I used blue theraband brand rubber
> > sheet, purchased for a couple of bucks at any physical therapy
> > cut into the right strip shape, and glued with plain old rubber
> > (coat both surfaces, let dry, put together just like contact
> > If your motor can turn the rollers with the belt on, it should do
> > until you are successful at generating long sparks. As the voltage
> > builds up on the sphere, the load goes up on the motor. My own VDG
> > will need a larger motor when I get the corona leakage problem
> > Looks like you're close! Good luck and have fun!
> > Paul
> > --- In VanDeGraaffGenerator@yahoogroups.com, "oracle9992000"
> > <oracle9992000@> wrote:
> > >
> > > I have been working on a VDg for over 6 months. I need some help
> with a
> > > few parts. I have a power point of it so far please tell me what
> > > think. Power point is under my files.
> > >