Science Buddies: "Ask an Expert"

did everything right and the thing wont work! please help any suggestions will work (within reason).

Hello and welcome to the forums.

Could you please provide us with more information? What information did you use to build your generator? Can you point us to a web resource explaining what you're trying to do? Then please describe where and what you think is failing. Thanks.

Keith

sorry, ive used this websites model in building an electric motor and am simply trying to get an inch spark. me and my dad have tried everything. the only things we have changed is 1. made the bottom pvc piece shorter 2. used wire thats coated in some silver stuff that i have no idea about 3. and put a toggle switch to in the battery circuit. thanks for your help and god bless

Sorry, I'm not understanding "this" in terms of which website's model.
I tried putting "building an electric motor" into the Science Buddy search engine for the Science Buddies's site and don't see anything related to a Van de Graaff generator.

Please copy and past the URL from the web page into the reply so we can try to see what you are attempting to use as a reference.

sorry again the url is http://sciencebuddies.com/science-fair- ... U&from=TSW. scroll down a little and it should be there you just press "a simple homeade generator" and it will show instructions.

Sorry, I missed the Van de Graaff generator being hidden down in the simple motor project idea.

The "silver" stuff on your wires is probably "tin" or some other anti-corrosive to prevent the copper wire from oxidizing. That shouldn't cause any problems.

There are some "fine points" that might not be obvious from reading this project:

1) The stripped portion of the stranded wire (top and bottom ones) inside the PVC tubing must be formed to act like spring loaded brushes that stay in contact with the rubber band as it moves. If they are on the side where the band is moving up, they should make contact in an upward angle. If they are on the side where the band is moving down, they should contact in a downward angle.
2) The top wire must make good electrical contact to the aluminum can in an area where the paint / annodize coating has been scraped / sanded off.
3) The rubber band must be under tension (stretched ) and moving fast. At least one rotation per second. Faster is better.

What is the relative humidity where you are conducting this experiment? If it is too high, the rubber band and steel pulleys might not produce enough charge transfer on their own. You might try using a plastic sleeve over the nail. A 1/2 inch long piece of an inexpensive plastic ball point pen ink cartridge cut from above the ink line should work. If you have some wool yarn, you might try wrapping some around a nail and finding a way to put it as a tension rod in the tee just above the motor pulley on the opposite side of where your brushes are. The goal of the things I mentioned in this last paragraph would be to increase the static charge on the rubber band surface.

Hope this gives you some ideas and one of them works.

thanks, in the directions it says the "brushes" must be almost touching the rubber band. so you say they need to touch cause i didnt do that.

the "brushes" must be almost touching the rubber band. so you say they need to touch cause i didnt do that.

In a dry (not humid) environment where the rubber band and the pulleys are generating a lot of static charge, almost touching is good enough, but almost touching means that the spacing is small enough for the charge to transfer. Since your existing setup didn't appear to be transfering charge, I recommened eliminating the gap. The problem with actually having the brushes touch the rubber band is that there will be friction and it will cause the rubber band to wear faster. My recommendation of angling the brushes with respect to the direction of rubber band movement was to decrease pressure and thus friction. Once you get charge transfering, you can alwys fine tune it to get longer rubber band life. This is a subtle fine point in Van de Graaff generator construction.

thank you for your help. i will try to do it.