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Registered Member #2084
Joined: Sun Apr 19 2009, 04:31AM
Location:
Posts: 11
I attempted to make my first generator today. It's not working at all maybe someone can spot my problem.
Materials:
Rollers: Axels are made of wooden pegs, rollers are styrafoam covered in pvc pipe coated with double sided tape then the triboelectric material is attached. Top roller is coated in teflon tape , bottom is coated in aluminum foil.
housing: A thick cardboard tube.
Brush: a T.V. Antenna cable taped to the bowl, stiffened with tape and a coat hanger wire. It is about a centimeter directly above the belt.
Sphere: two stainless steel(?) salad bowls taped togeather (tape is on the outside).
Belt: a type of ribbon, it is a thin stretchy plastic. it gets folded a bit on the bottom roller, but I don't think the negative side ever actually touches the positive, it is fairly tightly on the rollers.
Motor: a drill attached to a free end of the bottom peg.
Misc:
The mechanism works fairly smoothly, the rollers roll. the belt stays on them and in the middle.
the bottom of the housing is open, and about 2 inches from the floor, there is no brush to ground it does this matter?.
I think the problem might be Humidity, or that I got a small bit of oil from my hands on the belt, I was however trying to avoid over handling, and only ever touched it a few times. But maybe my materials are out.
Any help or information would be greatly appreciated THANKS!
Registered Member #834
Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644
Cardboard tube? Not enough insulation (by several orders of magnitude). Use a PVC tube. A brush to ground at the lower roller is absolutely necessary, as well as a brush to the terminal at the upper roller. "Ground" here can be just the base of the machine, if not made of a highly insulating material. You will need a more solid construction of the bearings if you want the machine to last more than a few minutes.
Registered Member #133
Joined: Fri Feb 10 2006, 10:27PM
Location: Pensacola, Florida
Posts: 47
Antonio has a very good point concerning the material of the tube. Cardboard readily absorbs moisture and will easily conduct current between your collector and the bottom of your generator at the high voltages involved. This leakage current may be sufficient to bleed off the collector charge before it has a chance to develop the high potential voltage that the generator is designed to produce. I would definitely replace the cardboard tube with a good plastic insulator support.
Registered Member #2084
Joined: Sun Apr 19 2009, 04:31AM
Location:
Posts: 11
I didn't like the idea of using that tube or the welfare berring idea either, but I'm poor.
anywho round 2, I tried something a little smaller its just as jerry rigged, But I can't see why this one won't work :(
Same sort of deal, top roll is teflon coated, bottom is aluminum foil. Its got the same synthetic plastic/rubber sort of belt. and that bottle its housed in is made of plastic. I'm running it with a drill.
the bottom brush is grounded to whatever I can find thats big and metal.
Registered Member #834
Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644
What is that wire across the plastic tube? A Van de Graaff machine does not generate arcs. A pointed wire close to the terminal will drain all the charge silently. Make it sure that everything is very dry. Use a hair drier to heat the machine if necessary (be careful to not deform the tube).
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
Brush: a T.V. Antenna cable taped to the bowl, stiffened with tape and a coat hanger wire. It is about a centimeter directly above the belt.
What kind are you talking about? The two-wire cable, who's wires are about half an inch from each other?
If my understanding of Van De Graaffs is correct, a better brush would be 12 or so gauge stranded wire, with each strand separated. This would be a bunch of different conductors. Also, shouldn't it lightly touch the belt?
The dryer the environment, the better. Otherwise you leak charge faster. This is bad since it is static, and has no real current.
Registered Member #2084
Joined: Sun Apr 19 2009, 04:31AM
Location:
Posts: 11
kewl, not sure if it was the hairdryer, or getting the wires to physically touch, or taping over the sharpish edges, but it definately works.... half ass, but I get about 2cm sparks lol thanks for the help again guys!
Registered Member #834
Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644
You can see that this machine is not very critical. The belt doesn't induce currents, but due to the high electric field, the air between it and pointed wires close to it gets ionized and conducts electricity. The brushes connected to the terminal and to ground shall not touch the belt, but just have points close to it. They can touch the belt, if you use very light brushes that will not damage the belt, but this is not necessary.
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Van der graaf generator issues
