120,000 Volt Van De Graaff Generator

Step 7 The brushes and tuning

The brushes are multi strand copper wire fanned out and mounted approx. 1/4" inch from the belt roller combo at each end. The top brush is connected to the inside of the sphere and the bottom brush is connected to ground, whether an earth ground or power supply ground seems to be irrelevant.

At this point slip the dome on and apply about 6 volts to the motor. You should feel a charge around the dome.

Tuning. Don't allow the brushes to rub against the belt, the deposited copper will make the belt conductive and the generator will stop working. If it fails to work at all adjust the brushes and try again. If all else fails degrease the rollers and belt with rubbing alcohol, grease is death to triboelectric charge separation.

Comments

[peacefoots]

how small of a motor can you use

[sheial360]

So does the bowl have be cut so the PVC pipe fits in it and the bowl covers  the hole that was made and the roller ?????? ,        
And does the sock  have to move or does it stay still ????

[Tool Using Animal]

Yes the bowl must be cut, the roller absolutely must be inside the domw.

The sock must also move, just like a fan belt on a car

[emeraldamber]

I really don't get the bottom brush connected to the ground... is it connected literally just to the ground..? and what is it for...? me and my groupmates are trying to make one... we used Teflon for the bottom roller and aluminum at the top but it would just not work. does the motor have to be fast working? what should be the mixing bowl made of? aluminum? stainless? help! :(

[Tool Using Animal]

The bottom bruh really is just connected to ground, it's just a soucre of charge. the mixing bowls can be any metal, on mistake I've seen over and over again is the top roller and brush MUST be INSIDE the mixing bowls. The faster the motor the faster the charge builds up and it is a race against how fast the charge leaks away. Pix are always a help in diagnstics.

[slipknot rules]

Van de graafs work best in under 40% humidity :)

[metropox]

Today I finished constructing my very own van de graaff...it was working magnificently, creating miniature electrical arcs across to my hand. I turned it off, did other things, and came back in a couple of hours to give it another go. For some reason it would not charge at all. I checked the brushes to make sure they weren't touching, and the belt (I used a rubber latex exercise belt) seemed clean. I turned on the motor and applied rubbing alcohol to the spinning belt just be sure and it still wouldn't work. I thought maybe the carpet floor was interfering (my ground wire ends by touching the carpet floor), but then again it was working earlier today. Any ideas as to what it could be?

[metropox]

It turns out that humidity was my problem. I had been using the air conditioner to dehumidify the room and didn't realize how fast the room re-humidifies after the air conditioner is shut off.

[bsumner]

how exactly is the wire connected to the inside of the sphere? is it just loosely touching or did you solder it somehow?

[Tool Using Animal]

Just loosely touching, I fanned out the end so atleast one strand will touch.

[bsumner]

oh ok, thanks!