Date: Tue Mar 31 15:46:29 2009 Back to Contents ------------------------------------------------------------------------

Author: Bill Alexander

Subject: Re: VDG question


I bought one of the VDGs from Pasco, and it did not work very well at all, when first plugged in. Upon taking off the top, and the bottom, I found that both "combs" had gotten out of place in shipping (the bottom one is not very solidly held). After moving them close to the belt, it works great. Previously, with our old VDG, one time it just quit producing much of any spark. I took it into the optics dark room, and discovered a 1 mm or so sharp piece of metal that was the problem. Invisible out in the light, but in the dark the corona discharge was obvious.

Also, in my experience the best sparks are obtained from VDG to ungrounded sphere to sharp grounded wire about 6 inches on the opposite side of the ungrounded sphere. Nice sparks jump to the sphere, and also jump from the sphere to the point. I have a plastic meter stick with a sharp piece of welding rod on the end, with a long wire to ground.

Good luck,

Bill A.

----- Original Message -----
From: "Santos Ramirez"
Sent: Tuesday, March 31, 2009 11:51:55 AM GMT -08:00 US/Canada Pacific
Subject: [tap-l] VDG question


A professor here ordered a
Cenco Large Van De Graaff # CP33891-00
from Sargent-Welch last week (description follows).

Problem is - it does not generate very large sparks.

Has anyone else had problems with this VDG?
Is it fixable?

(We have 2 old (circa 1960) VDGs that work great and
the one ordered was the only one close in style to the old ones)

TAMU -Physics

Generates 400kV. 105k More than Any Other Van de Graaff!

Based on the well-known Van de Graaff system, our newly improved design
features a large 28cm diameter collector sphere, a substantial 12.5cm
diameter x 56cm high transparent insulating column, a completely enclosed
base with a variable-speed motor, and an integrated discharger on a
movable arm for controlling the length of the sparks and discharging the
sphere after use. The long column and the smooth finish substantially
reduce charge loss by leakage and spray discharges, which results in
improved reliability and greater maximum spark length. The generator can
develop voltages up to 400kV under favorable conditions. The low average
current of about 10ìA or less prevents harmful shocks. Peak current
generated is about 50ìA. Operates under all humidity conditions
encountered in the classroom. With 3-wire line cord and switch for 110V,

From Tue Mar 31 15:46:29 2009