Introduction: KCA Science Club "Van De Graaff"
This is a simple Van De Graaff generator. We used a 6-inch piece of plastic pipe 30 inches long; an oscillating fan motor bolted directly to bottom of pipe which had a nice long shaft where a plastic bed roller was driven into it tightly. Another plastic bed roller bolted to the top with 1/4 40 thread all. This allows you to bolt it to the pipe as well as using nuts to keep the roller in the center. Be sure to place your metal bowl down the middle of the pipe first before going to the trouble of bolting the top. We cut the 6-inch hole out of the salad bowl with a dremel tool and a hack saw blade held by hand. We bought some heavy gauge insulated wire, then stripped the plastic coating off and fanned out the wire to pick up the charges off the rollers. Make sure you snip the wires so that they lay evenly along the roller. We had to watch closely at first to make sure the belts did not catch the wires if too close. We used some angles off of an erector set to help hold the wires tightly. We made belts from exercise rubber bands; vinyl-covered shelf paper with a felt backing; neoprene cloth-backed materials used to support backs for sports, as our test belts. The shelf paper worked the best and was pretty cheap. It's a simple, fast construction that we hope to improve. One of the problems is that the belts if too tight make the fan motor hard to turn. We use a drill motor to the shaft sticking out the opposite side of the pipe to get the belt a little loose so the fan motor will turn it. We have had high humidity so far during our experiments but even still have had 10 cm charges. The bottom roller is covered with aluminum tape and the top one with plumbers' pipe-fitting tape (teflon maybe.)
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