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Re: diathermy machine
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All,
As regards diathermy machines. Daryl Dacko gave a good description of what
a diathermy machine is. They are known both as diathermy machines and as
dielectric heaters. The term diathermy was originally associated with its
use in medicine. It is used to heat local areas such as skin and muscles.
The name diathermy comes from the words dia and thermo and literally means
to heat through. When a dielectric material is placed between the plates of
a diathermy machine it causes heating due to two major causes: dielectric
losses and gaseous heating of surface molecules. Tesla refered to that
aspect as gaseous bombardment. Both are electrostatic in nature and cause a
rapid movement of molecules that results in heat throughout the material
placed between the plates.
Note that the heating effect can readly melt plastics. Such as the
dielectric between capacitor plates. In every Tesla coil there is some of
this dielectric heating of the HV capacitor's dielectric. Sometimes it
results in destruction of the dielectric as a spark penetrates and makes a
rupture because of the softening of the dielectric. One of the reasons for
making oil filled capacitors is to reduce the air, because the localized
heating of the *air* can become much hotter much faster than the dielectric
heating effect of the plastic. That is why it is so important to remove as
much of the air from a homemade oil-filled capacitor as possible. When a
capacitor is run for extended periods of time the entire dielectric may
become extremely hot. This heat is more concentrated at the center, as it
is surrounded by all the other warm dielectric material. That is why the
capacitors get warm, and why the breakdown in this mode is usually at the
center of the rolled capacitor.
Hot spots in neon transformers are also a result of localized heating and
breakdown of either insulation or tar due to the vigorous RF that is all
too often fed back into them. You will notice that often it is the outer
layer of the secondary that is most affected. This is consistent with
electrostatic effects.
As an aside, diathermy machines are not the only machines out there that
can be a source of material for Tesla coil builders. RF induction heaters
make decent Tesla coils, too! Some of these use spark gaps just like the
diathermy machines. By the way, if you want, you can use your Tesla coil
power unit as an RF induction furnace. Here's how:
Disconnect the primary/secondary. Replace the primary with about 5 turns of
1/8 or 1/4 inch copper tubing wound helical style at about 1 inch diameter
and with about 1/4 inch between windings. Get a 1/4 inch diameter bolt
about 2 inches long, and tape one turn of 1/2 inch wide paper around the
center of the bolt. Insert the bolt into the coil such that it is centered
in the coil. I use a test-tube to hold the bolt so it doesn't touch
anything. Turn you power unit on. Within a very short period of time the
paper should burst into flames because the metal bolt got hot enough to
ignite it. Depending on your power unit, you may be able to get the bolt up
to incandescence. When used as an induction heater we are using primarily
electromagnetic effects, whereas the diathermy machine exploits
electrostatic effects. One heats metals and the other heats insulators.
Both use the exact same disruptive discharge circuits that we use in Tesla
coils. So if you come across one, grab it up!
Fr. Tom McGahee