RE- Re: Surface Sparks =
From: Robert Michaels[SMTP:robert.michaels-at-online.sme-dot-org]
Sent: Monday, August 04, 1997 4:38 PM
Subject: RE- Re: Surface Sparks =
Point made, and point taken. Acrylic plastic certainly melts
easily. A workaround is to use urea-formaldehyde plastic
("Formica"; "Marlite") or melamine-formaldehyde as they are
thermosets. Glass is of course superior to either of these.
(In my dreams!) I've used polished black marble
and have wondered what effect would be produced
using the types of marble which have metallic
threads or veins running thruout ?!!
As stated, this apparatus is best used with smallish coils,
Some of the mega-coils described in This List
would likely cause the whole damn thing to
to vanish in a flash and a puff of smoke !
and if such are vacuum-tube-driven, the display may be run
for hours at a time (or until meltdown - whichever comes
first). Such makes a wonderful room decoration (for a rec-
reation room or a Tesla/Hi-V theme party).
- - - - - -
A very ambitious project is to cover the plastic (or glass)
with photographic paper (as used for contact prints).
When the coil is run very briefly and the paper then developed,
a permanent record is left of the spark traces. The developed
prints may be re-pasted onto the plastic (or glass) of the
apparatus. In this way, the effect may be enjoyed (to a
degree) even with the power off.
T>From: DR.RESONANCE[SMTP:DR.RESONANCE-at-next-wave-dot-net] T>Sent: Sunday,
T>August 03, 1997 2:43 PM T>Subject: Re: Surface Sparks = Wow!!
T>You will find you will have to go to glass eventually as the high energy
T>spark streamers will begin to actually "melt" their way across the plastic.
T> This usually only takes about 1/2 hour of continuous operation before the
T>melted streamer paths begin to show up. Glass works just as good and can
T>be used indefinitely for this purpose. We made up a 7 ft. dia unit with a
T>variable speed drive for the shop -- we call it the "Eye of Thor" and use
T>it for demonstrations.
T>> From: Robert Michaels[SMTP:robert.michaels-at-online.sme-dot-org]
T>> Sent: Friday, August 01, 1997 3:11 PM
T>> Subject: Surface Sparks = Wow!!
T>> Dear People:
T>> This post is inspired by the several recent ones on the tendancy
T>> of spark discharges to follow a surface and evince a longer
T>> sparking distance than would be obtained from the same voltage
T>> discharging in free air:
T>> This surface-enhanced sparking can be exploited to make a very
T>> entertaining "appliance" for use with small to medium sized
T>> Tesla coils:
T>> 1) - Obtain a sheet of suitable insulating material.
T>> Most any will do, but let's say acrylic plastic
T>> ("Lucite"; "Plexiglas"; "Perspex"; et. al.)
T>> 2) - The effect is enhanced if the acrylic is black, but the
T>> backside may be painted if it is colorless.
T>> [ ... ]
T>> A hissing, snapping circle of sparks jumps from the perimeter
T>> of the aluminum disk to the copper tubing -- usually from
T>> dozens and dozens of places at once, continuously dying out
T>> and reforming in another spot, sometimes rotating around the
T>> disk perhaps first clockwise, and then counterclockwise.
T>> - - - - - - -
T>> This general idea of a disk surrounded by an encircling ring
T>> of copper comes from no less an august personage than Dr.
T>> Tesla himself, but ASFAIK Dr. Tesla mounted his disk and
T>> ring in free air and did not avail himself of the ability of
T>> a surface to greatly enhance spark distance.