Re: Alternate toroid shapes

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Original poster: "Dr. Resonance" <resonance-at-jvlnet-dot-com> 


Yes.

12 years ago I "extended" the body of a toroid by grafting a long cylinder
in the center between the toroid upper half and the lower half.  My work was
an effort to obtain a greater capacitance by using an inexpensive device (a
cylinder easily formed by rolling sheet metal).  It was applied to a large
Van de Graaff generator and worked well to extend the capacitance value.

Due to electrostatic shielding effects some capacitance is lost from the
lower part of the upper toroid, however, the gain from the cylinder, which
can be quickly made as long as required, compensates for this loss and adds
considerable capacitance.

The result is a mushroom shaped sphere.

The central idea here was to obtain maximum capacitance for minimum cost.

It presently resides in the Carnegie Science Museum.

A second method I employed is as follows:

Imagine a large Van de Graaff sphere.  Use a large knife to "cut" this
sphere into 4 quarters.  Expand these quarters through space for a distance.
Use flat sheets welded to the quarters to obtain a large electrode surface
with the VDGRF parts acting as corners to effect field control in this
critical area.

A second set of VDGRF quarters provide the corners for the lower portion
while the first set of 4 provide the corners for the upper portion.

Our designed belt entry area into a flat surface will accomodate a belt
width of 48 inches with a spread of 12 inches.  Theorectically, this size
could be expanded to any size desireable.

We tested both of these electrode styles on large coils and their
performance exceeded the 8 ft. dia. toroids that we were using while the
cost was considerably less.  The only requirement is for an excellent welder
to do the work which we are fortunate to have.  All of the seams were
belt-sanded and hand sanded using copious amounts of dish washing detergent
(lowers friction during the sanding process and provides smoother finish).

A third method that works very well is to extend the distance between an
upper toroid and a lower toroid by using large grid stiff screen rolled into
a cylinder.  It it inserted at the inner edge of the toroid cross section.
Our measurements provided capacitance values equal to 1.6 times the
capacitance of a single toroid.  The toroid sizes we used were 48 inch dia.
x 12 inch cross section.  Toroid separation was 40 inches.

Dr. Resonance

Resonance Research Corporation
E11870 Shadylane Rd.
Baraboo   WI   53913
 >
 > Has anyone done any experimentation into toroid topload shapes other than
 > the typical round designs that all use?  Visualize a cross section of the
 > minor diameter that is tear drop shaped as opposed to perfectly round,
with
 > the point of the tear drop facing out.  Are there any inherent advantages
to
 > a shape such as this, and if so, is the reason no one utilizes such a
shape
 > because of construction difficulties?  I couldn't find any reference to
 > toroid designs other than the standard in the archives, and was hoping
that
 > someone could enlighten me.
 >
 > Thanks,
 > John Richardson
 >
 > Hi John,
 >      The typical TC Toroidal topload (more specifically a Torus) is
usually
 > chosen because the uniform radius of curvature reduces corona discharge,
 > and the simple symmetry lends itself to a single set of equations for
 > calculating the capacitance. I believe that the shape you describe having
a
 > sharp ridge around its equator would enhance coronal discharge and
preclude
 > the higher voltage buildup provided by the conventional shape. Also, I
 > believe each and every asymmetric shape would have to have its own unique
 > set of equations to do the Capacitance calculations. This seems a major
 > undertaking for what I believe would be reduced performance.
 >
 > Matt D.
 >
 >
 >
 >
 >
 >