Date: Tue Mar 31 16:32:58 2009 Back to Contents ------------------------------------------------------------------------

Author: David Maiullo

Subject: Re: VDG question


Hi Santos,

I also vouch for the Science First works very well, just as
Simcha describes.


simcha Segev wrote:
> Santos, It may be too late for your professor but I bought lately a large
> VDG from Science First
> at ~600$ and it
> look nice, work wonderfull in all humidity condition, produce long sparks
> ~25-30 cm and never faild.
> I'm not familier with your cenco VDG but one major problem could be some
> dust sticking on the isulator that hold the collector. Try to wipe it with
> alcohol. It might help. Check if there are some tiny "hair" dert sticking on
> the rubber belt. Other possibility is a bad comb contact (should be close to
> the rubber belt but without tuching) .
> -- Simcha
> -----Original Message-----
> From: [] On
> Behalf Of Santos Ramirez
> Sent: Tuesday, March 31, 2009 9:52 PM
> To:
> Subject: [tap-l] VDG question
> Tappers,
> 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)
> Santos
> 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 10žA or less prevents harmful shocks. Peak current
> generated is about 50žA. Operates under all humidity conditions
> encountered in the classroom. With 3-wire line cord and switch for 110V,
> 50/60Hz.

From Tue Mar 31 16:32:58 2009