OBSOLETE FILE For the updated version, see http://amasci.com/emotor/vdgdemo.html VANDEGRAAFF GENERATOR DEMONSTRATIONS (c)1994 William J. Beaty MOTOR MAGIC Build the pop-bottle electrostatic motor from plans elsewhere on my web pages. Use your VDG as a power supply for the motor. If you ground one bottle of the motor, stand on a plastic insulator, touch the VDG sphere, and point at the other bottle of the motor, the motor will start to turn. It is powered by the charged wind coming from your fingertip. Initially hold your finger a couple of inches from the bottle until you get the demo working. I managed to slowly increase the distance to the motor, retuning the motor brushes each time for best operation, until I could point at a motor which was four feet away! By instead using a paperclip taped to the VDG sphere and bent so it pointed at the motor, I managed to run the bottle motor from 10 feet away! This was in dry weather, when the VDG was working very well. GIANT VDG LIGHTNING If you have access to a second large VDG sphere, you can create immensely long sparks. (Remember, spark length is not proportional to voltage except under specific circumstances) Connect the second sphere to ground, and position it about 6in from the VDG sphere terminal. Affix to the grounded sphere a 1/4 in. ball bearing, or an "acorn" type 8-32 nut with a spherical head. Position the spheres so that the nut is in the gap between terminals. When the VDG is run, the nut will initiate the spark, and the field between the terminals will provide energy to allow quick growth. In a darkened room, increase the separation between the spheres until you have long sparks. I've occasionally managed to produce 24 in. sparks from a Morris & Lee 14"-sphere VDG in this way. DANCING BUBBLES Blow soap bubbles at your VDG terminal. They will initially be attracted, but then will become charged by ion wind and will then be violently repelled from the generator sphere. They will also be attracted to any other object. With practice you can hold your hand above a charged bubble and keep it aloft by attraction. ELECTROSTATIC LEVITATION Place a large metal sheet or foil-covered cardboard on the ground. It should be at least 2 to 3 times the diameter of your VDG sphere. Connect this sheet to earth-ground. Place some small crumpled pieces of foil on the center of the sheet. Pick up your entire VDG machine, turn it on, and while holding it by its base, move the sphere down towards the crumpled foil. With practice you can get the foil to levitate and hang in the air between the sphere and the ground plate. The VDG attracts the grounded foil, but then the corona discharge from the edges of the chunk will allow the foil to acquire a like-charge from the sphere, which increases a repulsion force. As the foil drops away, it loses its charge via corona, and is again attracted upwards. At a particular distance you can get a piece of foil to hang in space with balanced attraction/gravity forces and continuous corona leakage. (Note: there may be ion-wind filaments associated with this phenomenon. Someone should do the foil-lifting experiment in front of a Schlieren sytem and look for grey lines in the air.) MAGIC BLINKING WAND Put a small (.002uF, 250V) capacitor across a small (NE-2) neon pilot light. Hold one lead in your hand and bring the other lead towards the sphere of an operating VDG. The bulb will begin flashing. DON'T touch both leads at once, or you will get a shock from the capacitor. For safety, you can connect the two leads of your device in series with 1-meg resistors, then cover everthing except the resistor leads with insulating caulk. For dramatic effect you can mount this assembly in the tip of a conductive wand. FAUX - DOO Sometimes the humidity is too high and, even though your machine gives sparks, the "hair raise" demo doesn't work. There is just too much leakage to ground. All is not lost, you can cut up some strips of tissue 2cm x 15cm and tape them all over your VDG sphere. When operated, the tissue strips stand out just fine. Sometimes the humidity is low, yet your audience will have no long-hair 'victims.' In this case simply whip out your garage-sale 60's "Cher" wig and stick it on the sphere-terminal. CRACKLE'S HAILSTORM Pour a small pile of Rice Crispies on top of your VDG and turn on the power. Be prepared for a mess! If your machine is fairly powerful, you can stand on an insulator, touch the VDG terminal, then extend a handfull of cereal (flat palm, fingers spread hard) and they will levitate and fly to the nearest uncharged surface (your audience!) Note: a totally fresh box of Rice Crispies will have such a low humidity that the cereal will be insulating and won't acquire a charge from the terminal. If you open a new box of cereal before a demo, spray a bit of water into the box and shake well to distribute the moisture well. PLUS OR MINUS? To determine VDG polarity, connect a sensitive current-meter between the sphere and the base of your machine. When running, the VDG will produce a few tens of microamperes in the same direction as the high voltage polarity. If you lack a microamp meter, a tiny NE-2 neon pilot light will serve. If connected between sphere and base, one electrode will glow orange when the machine is run. The orange electrode is the negative one. HUMIDITY EMERGENCY Always carry an electric blow-dryer with you when doing VDG demos in high-humidity locations. When your machine fails, the usual cause is adsorbed water on the rollers and belt. Pop open the sphere or the base, run the machine, then direct hot air upon each of the rollers. Don't give up, sometimes it takes 5 minutes or more to dry the felt rollers used in the base of the WINSCO VDG. Another common problem is fingerprints and grime which make the belt and roller become conductive on humid days. Remove the belt, clean both sides with rubbing alcohol, then pat it dry with a clean paper towel. If one of the rollers is plastic, wipe it off with alcohol too. Don't wet the felt roller, it takes too long to dry again. One last possibility: if the voltage on your machine seems to drop suddenly during operation, try wiping down the sphere with a damp cloth. Sometimes your machine will attract a sharp, conductive dust mote which spews charged wind and shorts-down the sphere voltage. Wiping it down will dislodge it. CONDUCTIVE "INSULATORS" A suprising number of "insulators" behave as conductors when used with a VDG machine. Wood, cardboard, paper, twine, floors, and shoe soles can all behave as conductors as far as a VDG machine is concerned. Why? Well, consider a 12-volt, 1-amp, 12-watt flash lantern. In this device the light bulb has a resistance of 12 ohms and the wires contribute nearly zero ohms. As far as the flash lantern is concerned, material which is far more conductive than the 12-ohm lightbulb is behaving as a conductor, while anything far less conductive is behaving as an insulator. Now look at a Vandegraaff machine. A typical output is 30 microamps at 300,000 volts, giving a load resistance of V/I, or 10,000,000,000 ohms. As far as your VDG is concerned, "insulators" must have far more resistance than this. And "conductors" have far less. If a piece of wood has a billion ohms of resistance from end to end, your VDG machine will "think" that it is a conductor! IDEAS FOR MORE? Write me at billbeskimo.com