Re: Van de Graaff generator safety question (fwd)

[Steven Roys <sroys@xxxxxxxx>]

---------- Forwarded message ----------
Date: Thu, 08 Jan 2004 13:42:18 -0800
From: John Pepper <jspepper@xxxxxxx>
To: High Voltage list <hvlist@xxxxxxxxxx>
Subject: Re: Van de Graaff generator safety question (fwd)

Greetings All,

I have recently completed a functioning pumped Van de Graff using a 20"
waterscapes gazing ball.   Using the small tooling hole as a guide I laid out a
circle for the belt/support hole.   A small dremel with a cut off disk and a bit
of patients were used to cut the hole with satisfactory results.  The hardest part
was getting the edge rolled in on the hole.  I managed to get about a 3/4" radius
at best.  I tried making special tools and using heat but that stainless is tough.

For the belt I used 3" yellow caution tape fixed together with scotch tape.
Works just fine and does not generate allot of belt noise.  I would, however,
recommend something larger than the average sewing machine motor (it did not have
enough power and tended to surge).

For best results I strongly recommend using a small HV ionizer power supply
(~7.5kv@2 ma) to pump electrons onto the lower belt pulley.  The lower pulley is a
grounded aluminum pulley covered with vinyl tape and the top pulley is teflon.   I
used a sawtooth comb placed near the top pulley to remove the charge.

Best results to date with pumping are about 18" discharge to a grounded 3/4"
ball.   I have tried the blowdryer trick to remove moisture but with the
polyethylene belt is tends to grow in length and become too slack.

-John



High Voltage list wrote:

> Original poster: Steven Roys <sroys@xxxxxxxx>
>
> ---------- Forwarded message ----------
> Date: Wed, 7 Jan 2004 16:27:43 EST
> From: Esondrmn@xxxxxxx
> To: hvlist@xxxxxxxxxx
> Subject: Re: Van de Graaff generator safety question (fwd)
>
> In a message dated 1/7/04 7:32:19 AM Pacific Standard Time, hvlist@xxxxxxxxxx
> writes:
>
> > Hi Ed,
> >
> > They all come from Michael Gordan Ltd. which I think is just down the
> > street from your location.  Mirror Balls from Waterscapes that are drop
> > shipped from Michael Gordans.
> >
> > They all have a little hole in them for pressure/manufacturing that I can
> > compare the "real" edge too...
> >   the Starrett says "darn close" to 0.030...
> >
> > All from China or India so "cheap" is the name of the game...
> >
> > Cheers,
> >
> >          Terry
> >
>
> Terry,
>
> Yes, the place is only maybe 1/2 mile from here.  I agree, the s s material
> is thick.  You really have me thinking of building a Van de Graff now.  I have
> a small sewing machine motor that I could use.  Have you cut the hole in your
> gazing ball yet?  What design criteria have you got figured out so far?  What
> diameter form (pvc?) and how long from the base to the bottom of the sphere?
>
> Ed Sonderman