Re: van de graaff tube (fwd)

[<sroys@xxxxxxxxxxxxxxxxx>]

---------- Forwarded message ----------
Date: Sun, 5 Dec 2004 09:45:13 -0700
From: Gomez Addams <gomez@xxxxxxxxxxxx>
To: High Voltage list <hvlist@xxxxxxxxxx>
Subject: Re: van de graaff tube (fwd)


On Dec 4, 2004, at 8:29 PM, High Voltage list wrote:

> Original poster: <sroys@xxxxxxxxxxxxxxxxx>
>
>
>
> ---------- Forwarded message ----------
> Date: Thu, 2 Dec 2004 17:26:53 -0600
> From: Dr. Resonance <resonance@xxxxxxxxxx>
> To: High Voltage list <hvlist@xxxxxxxxxx>
> Subject: Re: van de graaff tube (fwd)
>
>
> We found out the hard way that a PVC tube with 12 inch ID doesn't work 
> at
> all --- the leakage current really starts to get high.  We built one 
> like
> this and only got a 1 inch spark out of it.  We use 6 inch ID tubes 
> all the
> tube for our model HV-750 (750 kV DC) machine and 6 inch wide belt and 
> they
> work just fine.  At 8-10 ID you start to seriously lose performance 
> with PVC
> as the main column support.

Well, I for one, have just decided to go with polypropylene for my 
machine(s).
(I may be building two, opposite polarity machines)  Thanks for the 
experiment
and research information!

> 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.

That sound like a truly frightening machine.

> 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.

  I don't think you mentioned your pully diameter?  Using belt surface 
speed instead
of pulley RPM would be more useful for everyone's comparison purposes, 
and would
remove any ambiguity.

>  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.

For your purposes, I can see where that would be a problem.  For my 
purposes... heh.  :)

.................................................................
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[I know a few Macintosh users who have problems distinguishing "IBM
compatible" PC's from space heaters, but that's another problem
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