Electrostatic Generators

[RUUUUUN]

I am building a Wimshurst machine using the tutorial/info found here: http://steampunkworkshop.com/how-build-wimshurst-influence-machine-part-1 and http://www.coe.ufrj.br/~acmq/wimshurst.html

 

I feel a design improvement is in order, and would like to run a few ideas by someone who knows much more than I.

 

Is anyone here very knowledgable about electrostatic generators, particularly the Wimshurst and Van De Graff?

[frosty90]

I am building a Wimshurst machine using the tutorial/info found here: http://steampunkwork...-machine-part-1 and http://www.coe.ufrj..../wimshurst.html

 

I feel a design improvement is in order, and would like to run a few ideas by someone who knows much more than I.

 

Is anyone here very knowledgable about electrostatic generators, particularly the Wimshurst and Van De Graff?

 

That looks like quite a nice wimshurst. I dont have any experience with them though.... I saw a nice antique refurbished one once I should have bought it, but I didnt....I regret that....oh well

 

Van de graafs are cool though. I have made one with a 35cm sphere (a toy earth globe covered with aluminium tape) and a PVC support. The bottom roller was aluminium, and the top was nylon. I used a file to make them taper toward the end, which keeps the belt centered (somehow...) I made the belt from plastic garbage bag!

The pick up 'combs' were fine copper wire strands. You could get 20 cm sparks to an earthed terminal on a very dry day.

 

If you make one, the design isnt all that critical: the roller materials arent all that important. Its usually convienient to use plastic and metal (like aluminium). If you 'pump' the bottom comb with a HV DC supply, you can make both rollers metal. But this isnt needed to produce a good result. But it helps if you have a damp climate. If you seem to be having a lot of leakage, or you just want your van de graaf to charge faster, use a wider belt. You can usually measure the charging current with a cheap multimeter with a microamps scale, one end on the terminal and one on ground. I cannot recall what it 'should' be for a small hobby sized thing, but id gess 10 uA at least for reasonable results, when running on a motor, or a really fast hand crank!

 

Keeping everything dust free and clean is the key for good results. Any materials that could absorb moisture are usless. Wood is out of the question. Black plastics are usually too (sometimes they have carbon in them, so they are conductive). Cardboard is ok, but you need to dry it in the oven first then seal it with laquer of something. Electrostatic machines usually wont work at all in high humidity. Moderate humidity is ok with a pumped van de graaff though....

 

Any conductors which neeed to hold the charge should be very round, with no sharp edges. Even a speck of dust on the surface can be a sharp enough edge if the radius of curvature of the conductor is small.

 

Also, always remember to discharge the thing before you touch it! if your leyden jars on your wimshurst or you sphere on your van de graff are very large, they could hold serious amounts of energy. Very large leydens or van de graaff spheres are really quite dangerous! Good luck, make sure you post construction/result pics!!!!!