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Re: Top Toroid

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> From: Tesla List <tesla-at-poodle.pupman-dot-com>
> To: Tesla-list-subscribers-at-poodle.pupman-dot-com
> Subject: Re: Top Toroid
> Date: Saturday, February 01, 1997 11:25 PM
> 
> Subscriber: rhull-at-richmond.infi-dot-net Sat Feb  1 21:11:45 1997
> Date: Sat, 1 Feb 1997 09:04:31 -0500 (EST)
> From: richard hull <rhull-at-richmond.infi-dot-net>
> To: tesla-at-pupman-dot-com
> Subject: Re: Top Toroid
> 
> At 11:15 PM 1/31/97 -0700, you wrote:
> >Subscriber: FutureT-at-aol-dot-com Fri Jan 31 23:09:47 1997
> >Date: Fri, 31 Jan 1997 11:08:23 -0500 (EST)
> >From: FutureT-at-aol-dot-com
> >To: tesla-at-pupman-dot-com
> >Subject: Re: Top Toroid
> >
> >In a message dated 97-01-30 03:33:50 EST, you write:
> >>snip
> >><< 
> 
> >  >>
> >
> >Interestingly, toroids (even thin metal ones) get quite warm when used
on a
> >tube coil, at high power levels.
> >John Freau
> >
> >
> John,
> 
> Wow!  I didn't know that.  I only tried to use a large toroid on my tube
TC
> one time and it was a real bust (limited tune range).  I suspect it is
> induction type heating due to the more CW nature of the systems output.
> Where the energy is delivered in a more steady fashion with longer energy
> trains.  You have any ideas on why?
> 
> Richard Hull, TCBOR

John, Richard,
I have observed that ANYTHING connected to the output of a tube coil is
subject to this heat. The tube coil has more of a brush discharge, its RF
output is cleaner, more sinusoidal that the pulse stuff we get from
disruptive discharge on a classic Tesla coil. For this reason there will
always be greater localized heating around the conductor at the top of a
tube coil. Any experimenter who has ever taken the discharge of a tube
tesla coil directly to their skin can attest to the strong localized
heating caused by the RF. When a Top load such as a large sphere or toroid
is placed on a tube coil and there is no observable spark, there is still a
dielectric heating of the air. Medical Diathermy is based on this RF
dielectric heating effect. It is not the metal that is heating up, but
rather the AIR in close proximity to the metal. The heated air then
transfers this heat to the metal. Try putting a plastic bag LOOSELY around
the top electrode so that there is a TRAPPED layer of air between the bag
and the terminal electrode. I secure the plastic bag either with tape or a
rubber band. Turn the coil on, bring up the power, and sometimes you can
even get the bag to MELT from the heat of the trapped air. 

The RF inductive heating effects are quite strong near the primary coil,
but they diminish rapidly as you move away from the center of the primary.
Dielectric heating effects will not directly affect metal, but rather
plastics and gases. I think what we have here is dielectric heating and/or
heating from the brush discharge if it is visible.

Fr. Tom McGahee