Date: Wed Feb 14 17:42:02 2007

Author: John Welch

Subject: Re:

Post:







Has anyone tried replacing the cloth covered metal roller in the base
of a Winsco VDG and/or reversed the rollers to get a positive charged
ball? I'd like to try but it doesn't look trivial, so any tips would be
appreciated.
-John


Sam Sampere wrote:









I picked up a Science
First Van de Graaff generator over the
summer for loan to HS teachers. I’ve used it a couple times and have
been
pretty disappointed in it. I should have realized that when the front
panel
reads “Van de Graff”. The correct spelling is Graaff.

I also heard what sounded
like arcing coming from inside the
base. When I opened it up and turned it on and looked, I could see arcs
from
one of the fuse connectors to the other. Hmmm. Why would the fuse be
arcing to
itself??

Why is the charging
current so small – barely noticeable
on a 100 micro amp meter. Turns out that the motor ground isn’t
connected
to the chassis. Oh, the chassis is floating! So the supplied ground
terminals
aren’t really ground at all because they’re not connected.

A simple alligator clip
connecting building ground to the
base solved all the problems. 25ish microamps, no arcing at the fuse,
no shock
turning off the VdG, etc. Geesh!

As far as small VdGs go,
I think I like the Winsco best.
Unless you have an old Cenco unit. Those are great, especially when you
make
new pulleys out of gray PVC and acrylic as Cliff suggested eons ago.

Sam

--------------------------

Sam Sampere

Syracuse
University
Department of
Physics
201 Physics
Building
Syracuse,
NY 13244
315-443-5999

315-443-9103
(fax)






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