Re: Structrual support, was: oil dielectric

["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>

Hi Paul,

Other than the base of secondaries used in VTTC and SSTC's and small
tertiary coils in high power magnifiers, disruptive tesla coil
secondaries don't develop very much heat. Any coil form you choose to
use should be strong enough to support the weight of the winding,
topload, and wind forces, have inherently high insulation resistance and
electrical breakdown strength, have relatively low RF loss, be
relatively impervious to moisture absorption, and be sufficiently
thermally stable to withstand expected temperature variations in storage
or operation. Further, the material should be readily available at low
cost. Thin wall PVC pipe satisfies virtually all of these conditions
admirably. While PVC can't handle high temperatures... but fortunately
it doesn't NEED to. 

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.

Regarding shrunken coins - these are available from my web site or off
eBay:
http://www.teslamania-dot-com/
OR
http://cgi6.ebay-dot-com/aw-cgi/eBayISAPI.dll?ViewListedItems&userid=bert.hickma
n-at-aquila-dot-net

Best 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 05/24/2002 7:37:46 AM Pacific Daylight Time,
> tesla-at-pupman-dot-com writes:
> 
> >
> > Paul,
> >
> > Absolutely! And a glazed surface would be preferable to reduce
> > absorption of potentially conductive material. Ceramic has been used for
> > high power RF coil forms for almost 100 years. The downside to using
> > ceramic is that it's significantly heavier and more brittle than PVC.
> >
> > Best regards,
> >
> > -- Bert --
> > --
> 
>   Bert,
> 
> You are correct about the ceramics being much heavier and more brittle. I
asked
> questions about useing 300 series  (non-magnetic) stainless in another
> post.This would allow for a thinner coating of ceramic. Reply posts indicate
> metals would absorbe energy in the form of heat causeing losses in the
coil, as
> well as expansion and contraction in the steel tube. I would not see any
> problem with useing pvc coated with ceramic in place of the stainless, except
> that the glazeing process would melt the pvc. Just how hot would a piece of
> iron become inside a ceramic tube?
>   Envision for a moment, two stainless or titanimum tubes, separated by a
> ceramic spacer for the central body of the coil. Would stainless steel heat
> less?  Although stainless and  titanimum might heat inside a Tesla coil, if
> thinner pieces were used, would they heat less, or simply radiate heat
faster?
> Paul
> PS I have to ask, how much are your shrunken heads? (Quarters)