Re: Structrual support, was: oil dielectric, ozone production

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

Original poster: "Bert Hickman by way of Terry Fritz <twftesla-at-qwest-dot-net>" <bert.hickman-at-aquila-dot-net>

Paul,

Tesla's early research started with oil-immersed iron core induction
coils, but he rapidly dispensed with iron cores altogether since they
were too lossy. In my earlier response, I had assumed you were asking
about winding a secondary for a classical air-core Tesla Coil using
different materials for the coil form. I'm not sure I understand the
physical configuration of your proposed system. The bottom line is that
metal cores and RF simply don't play well together - that's why RF
transformers use poorly conducting ferrite materials or no cores
whatsoever. If you want to recreate some of these earlier experiments
you could simply use an earlier style automotive ignition coil as a
starting point. The sharpened tip of a wire connected to the HV output
can then create a brush discharge (corona). A flyback transformer and
transistor driver would be another way to do this.  

Bert regards,

-- Bert -- 
-- 
Bert Hickman
Stoneridge Engineering
Coins Shrunk Electromagnetically!
http://www.teslamania-dot-com

Tesla list wrote:
> 
> Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Xyme3-at-aol-dot-com>
> 
> In a message dated 05/27/2002 1:07:09 PM Pacific Daylight Time,
> tesla-at-pupman-dot-com writes:
> 
> >
> > If you instead tried to use a metallic coil form, even if insulated by
> > some type of coating, the coilform will behave as a big short-circuited
> > turn, introducing huge system losses that are virtually independent of
> > the form's magnetic properties. Even slitting the pipe lengthwise to
> > break the "loop" doesn't help much, since you still develop significant
> > internal RF "eddy currents" within the form which sap large amounts of
> > energy from your system, converting it to heat instead of streamers. But
> > even if you were capable of developing significant voltage across the
> > secondary winding, the relatively thin insulation between the winding
> > and the conductive coil form would break down, short-circuiting the
> > secondary winding. PVC is cheap and it'll work for all but the most
> > stringent coiling applications.
> 
> Bert,
> Thank you for the information. Ceramic would solve the problem of heat being
> transferred from the metalic core, however the system loss you describe is a
> concern. You mention specifically the secondary winding and the thin
insulation
> between it and the metallic core breaking down. Is this less of a concern in
> the primary? If only one metal core was inside the primary were used, would
> system losses be half as much?  How about if an iron core was only inside the
> secondary?
> 
> My questions stem from readings about St. Elmo Fire devices. In this
particular
> coil an iron core was used for the primary winding. The iron core was
inserted
> inside the secondary ( which was wound around an iron pipe?) until an
> electronic flame or  brush was produced. The flame produceing electrode
> attached to the external secondary. One passage stated that iron was more
> permable at higher temperatures thus produceing a better brush. In specific
> ozone production was mentioned as a by product. Ozone has been approved for
> sterilization of food in place of chlorine.
> Paul