Re: van de graaff tube (fwd)

[<sroys@xxxxxxxxxxxxxxxxx>]

---------- Forwarded message ----------
Date: Tue, 07 Dec 2004 21:21:27 -0200
From: Antonio Carlos M. de Queiroz <acmdq@xxxxxxxxxx>
To: High Voltage list <hvlist@xxxxxxxxxx>
Cc: hvlist <hvlist@xxxxxxxxxxxxxxxxx>
Subject: Re: van de graaff tube (fwd)

High Voltage list wrote:

> From: Dr. Resonance <resonance@xxxxxxxxxx>

> My idea of an ideal VDGRF would be as follows:
> 
> Horizontal cylinder 6 - 8 ft long x 48 inch dia.  40 to 46 inch wide belt
> runs into this cylinder.  Hemisphere end caps welded on both ends and sanded
> perfectly smooth.  Supports would be 4 long pcs of 2 inch dia.
> polypropylene.  Sphere support at 4 x sphere dia. from any other metal
> objects, floor, or ceiling.

How would you power the belt? Maybe batteries inside one of the
terminals.
 
> We finally switched our large ball (40 inch dia.) to polypropylene supports
> with external belt and it went from 1 inch sparks to 32 inch sparks
> immediately.  Belt was 8 inches wide running at 2,000 RPM.  Any faster and
> it begins to sound like a machine gun.  1 spark every 1-2 seconds if about
> right.  1 spark/sec starts to scare people, especially small kids.

I like VDGs with external belt. I found a big HV ceramic insulator that 
looks suitable as a central support, between the runs of the belt. I
was not expecting it to have so good insulation, but a test showed that
it is as good as PVC as insulator, if not better.

Antonio Carlos M. de Queiroz