Troubleshooting a homemade Van de Graaff generator

Question

So, I'm trying to build a Van de Graaff generator from household items, but after a lot of tries, I'm still unable to get it working and was hoping someone here could help.

The problem is that no matter how long I leave it to run, there's just no charges accumulating on the dome at all.

Here are my observations and some things I measured:

• the belt is spinning and there is enough friction between the belt and the rollers
• the bottom comb is connected to the ground (measured with my multimeter)
• the top comb is connected to the inner side of the dome (measured with my multimeter)
• the belt is not touching the combs
• voltage and current (when the machine's running) between the dome and ground are constantly 0

Now for the materials I used:

• I built the main support structure out of wood
• the combs are just spread out copper wire
• the bottom roller is made out of silicon tube
• the top roller is made out of wool wrapped around a piece of pen
• the belt is a piece of electric tape with the sticky side facing outwards
• the dome is made out of 2 metal hemispheres held together with some electric tape

Here are some pictures of the machine:

I've searched the internet and found some forum posts as well as sites for debugging Van de Graaff generators and followed their steps for troubleshooting, but with no success.

I should also mention that I've already changed the material of the bottom roller and the belt (the roller used to be polypropylene and the belt used to be some elastic cloth that I sawed into a belt) and I also made sure that the rollers are leveled and that the belt is centered.

(Also, I know that connecting things with hot glue isn't a great idea, but it's the best thing I had)

Answer 1

You design is innovative and creative, but could be improved.

1. As mentioned, wood absorbs water and, particularly in humid conditions, is not a good enough insulator. Plastic drain pipe, 50 mm or larger diameter, is not expensive and works better.
2. The combs must be within a mm of the belt to be effective, and slightly to opposite sides rather than directly atop or bottom.
3. There should not be friction at top and bottom rollers.
4. Rubber bands make effective belts, not vinyl tape. One can cut them from bicycle inner tubes, for long columns, or just use large bands from a stationery store. Thin bands work better because they travel over the rollers with less friction and internal heating.

Also, in humid weather, most generators won't start without a DC booster.

_{Trivia: I once met Robert Van de Graaff at Ion Physics Corp., which made powerful electrostatic generators running in SF6.}

Answer 2

I have built many of them. The best designs spray a positive charge on the belt with a 15,000 VDC power supply. Both upper and lower rolls are aluminum with a steel drive shaft through their centers. I use fiberglass reinforced strap tape STICKY surface to STICKY surface to make a unitized seamless belt that requires very little driving power. The tape is available in 1” & 2” widths. Make sure your charge sprayer point is placed far enough to cause a purple glow. If you adjust to it close, it will arc and burn a hole through your belt and possibly damage the surface of your lower roll. The machined rolls should have a .04” crown on them.

Answer 3

I think that you are wrong. Friction of the belt and rollers makes the static electricity. I know that the pure triboelectric effect is based on contact but no one's Van de Graff has a perfectly tight and rolling Van de Graff. You can see it on electroboom's video. When he makes a perfectly rolling roller, his generator does not work. Sometimes it is better to use a stationary roller and check the triboelectric series and hope that your belt is being charged by your bottom roller and repelled by the top, or the opposite, charging the top roller caused by the friction of the belt.

Maybe wood is not a good material but as you can see everything is dirty there, clean your Van de Graaff meticulously with degreaser and try to first rub the materials yourself and check if they work.