Re: Slightly off topic- Van DeGraff Generator / other E&M experiments

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Antonio Carlos M. de Queiroz by way of Terry Fritz <twftesla-at-qwest-dot-net>" <acmq-at-compuland-dot-com.br>

Tesla list wrote:
> 
> Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<evp-at-pacbell-dot-net>

>         In this post you mention a "current doubler".  I've never been quite
> sure what this means or how to modify a simple machine to use the
> principle.  Can you give some help on this?

This is usually mounted on a metallic pulley mounted inside the
terminal.
Consists of an insulated metallic pulley and two combs.
A comb A collects charge from the up-going belt, at the point where it
touches the pulley. At the other side of the pulley, a comb B is 
connected to the terminal.
The connection between the comb A and the pulley equalizes their
potential, that due to the "ice pail" effect goes above the potential of
the terminal. Comb B then not only takes charge from the belt 
transferring it to the terminal, but also charges the down-going belt
with opposite charge, that is attracted to the belt by the charged
pulley. 
The effect is that similar opposite currents flow in the up-going and 
down-going sections of the belt, doubling the charging current.
The charging comb A can be omitted, as an insulated pulley will also
become charged soon.
This, at least, is the ideal situation. Sparks between the pulley and
comb B, over the belt, can discharge the pulley periodically, resulting 
in irregular charging current, and corona from the terminal to the
down-going belt (if the belt is not well insulated from the terminal)
can cancel the effect.

The connections for systems with two current doublers, that should
work as an influence machine, is shown as the "Toepler system" and
the "Holtz system" (charging combs omitted) in the picture:
http://www.coe.ufrj.br/~acmq/vdgself.jpg
The Toepler system was what I originally tried to make with my 
double VDG, but due to the exposed belts the system didn't work:
http://www.coe.ufrj.br/~acmq/myvdg.html

About my calculations for power in a VDG, I was wrong in saying that
mechanical losses are small. See what I measured in my machine, in
the address above. The losses there are more than 10 times greater than
the electrical output...

Antonio Carlos M. de Queiroz