ANSWERS : Technology

Can you make a Van De Graaf WITHOUT having the belt be in a tube?

I've noticed that most Van De Graaf machines have their belt assembly in a tube/pipe. But wouldn't it be possible to just have a frame holding the rollers instead of having them be enclosed? Sure, the belt won't be protected, but I don't really give a damn.

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Burf says: Feb 18, 2010. 12:27 PM

Its not absolutely necessary but the generator won't work nearly as well without it, The main purpose of the tube, besides holding up the dome, it to contain the electrostatic charge. The belt holds the charge very loosely and much of it can be lost to the air before being picked up by the brushes in the dome. Less charge equals a weaker discharge.

Antivolt says: Feb 28, 2010. 11:54 PM

External belt machines

The PVC leaks real bad above 8 inch ID. 12 inch ID tubes refuse
to work at all even when charged by a 10 inch wide belt. Been
there, done as they say.The large machine of D.C. Cox ( Dr
Resonance ) was also an external belt machine. It works very
well at 1,000,000 volts ! He runs the supports up inside of the
belts. He used polypropylene rods which outperforms PVC. The
large "pill capsule" design will be supported by four 2" dia.
polypropylene rods set at slight angles ( 25 degrees) to push
inward. Dr Antonio Carlos M. de Queiroz likes VDGs with external
belt. He found a big HV ceramic insulator that looks suitable as a
centra support, between the runs of the belt. A test showed that it
is as good as PVC as insulator, if not better.

http://tech.groups.yahoo.com/group/VanDeGraaffGenerator/

lemonie says: Feb 18, 2010. 1:13 PM

The top needs support, it happens to be easy to enclose the belt. If you've got an easier plan go for it.

L

169

Kiteman says: Feb 18, 2010. 12:58 PM

The VdG I currently use at school, in fact, every VdG I have used in the last 20 years, has had an insulating tube holding up the top dome, but the belt has run beside the tube, in the open air.