My first Home-made VDG. Stands 4ft tall, has a 16'' SS globe attached to a 3.5'' Acylic tube. 2.25'' wide Latex belt from Fredrick Graff and home-made wand out of plastic rod and another 4'' garden globe. Nearly all structural materials are made out of Acrylic, except where needed. Powered by a 12v 12 Amp Hour SLA battery (not shown). These images are actually a bit old. There is a PTFE roller on the top and a nylon roller on the bottom surrounded by 100% wool fabric secured using thin magnet wire wrapped around the roller.
I have a 20ft well insulated wire connected to a clip from Radio Shack which is clamped to a metal fence post in my yard which is connected to the ground terminal on my VDG. On good VDG weather, I get 16-20'' sparks. I'm purchasing a HV Flange Fred now sells and will add spark plug wire instead of cheap PVC insulated wire.. I expect to get a maximum of 25'' after the mods.
A note of warning! if you build a high quality VDG with a ridiculously huge globe like mine (16''), and it is powered from a wall receptacle, be aware of the following:
1. The discharge from the Globe will create an EMP, which induces a pulse in the cord attached to your wall, and subsequently..... your entire house's electronics (and ground terminal). I've so far fried a computer monitor and made our Bose speaker system crackle... I now perform my experiments in the corner of my lot (Towards the neighbors houses.... haha).
2. Do not discharge your VDG around sensitive RF equipment like satellite receivers. They will fry the electronics. I know from experience!
3. Do not use the ground terminal on you wall outlet for grounding your VDG!!!! This puts the ground of all the other electronics in your house at the voltage of your VDG.
4. I strongly advise owners and demonstrators to power their VDG via a battery because it electrically isolates (to some degree) the discharges of your VDG.
5. I recommend using Spark Plug wire for the grounding wire and wire connecting the wand to the VDG. Any holes in the wire spray charge, making your VDG not perform well.
6. Increasing the diameter of your globe increases the time it takes to charge it... thus the frequency of discharging (lightning bolts)
7. If you make your VDG too tall or run it too fast, the belt which is ++ charged on one side going up and -- on the other side going down will attract one another and rub, destroying your belt and performance. Shorten the tube, make thebelt tighter or slow down the RPM to help prevent this.
8. Ground all metal objects on your VDG, the sparks will be drawn to the E field of the metal. if the metal isn't grounded, the VDG will not perform as well. AKA.... Ground your motor!
9. Pleeeaaaase, don't put any semiconductors on here. No PWM circuit to control your motor speed will survive over 5 minutes without being fried. Use a rheostat (big variable resistor) if it's DC powered.
10. Don't carry your VDG by the tube when assembled....
11. I've got 8 layers of electrical tape around the edge of my hole in the globe and it still sprays electrons from it.... Buy a flange.
12. Clean the surface of your VDG globe every 5 minutes or so. Dust particles collect extremely quickly and will hamper performance.
13. Don't put a bottle of Windex (or conductive liquid) on the top of the VDG while it's running. the VDG ionizes the liquid and acts like a capacitor. Grabbing the bottle will not be painless! Although the sparks through the bottle as it charges looks cool. Once a hole has been burnt in the plastic by discharging to say... your finger, the bottle will leak charge from that spot and lightning bolts will travel along the inside of the bottle and leave through the charred hole.
Enjoy my tips and have fun. But more importantly.... Be safe! And don't fry your parent's electronics....