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Re: [TCML] VTTC New Grid Coil Geometry

Over the past two months I have been experimenting with a different grid coil geometry. On my dual 833A coil I fabricated a flat pancake coil out of 14 awg wire for grid feed back. The inner diameter is approximately the same as the primary solenoid. It has 24 turns and is placed 1" under the lowest secondary winding. The whole arrangement is covered by a phenolic disc and presents the appearance that the grid coil doesn't exist.
With this geometry I have changed the coupling association that exists among the three coils. I haven't as yet determined the exact relationships, albeit it works great. The coil required some tuning changes that were accomplished by reducing the secondary self capacitance with a smaller toriod and minor adjustment of the grid leak resistor.
I use two identical plate transformers 2800 volts @ 280 ma in parallel through a doubler. I need to lower the coil as it power arcs around 24" to the floor joists above. I suspect continuous 30" corona at full variac. I have no time now to work on it as I ended up on the University Personnel Committee deciding tenure issues. As far as I know this is a different approach to grid coils. Flash over is completely eliminated and I suspect (but have not proved) there is greater magnetic coupling to the primary. Bert Hickman was over a few weeks ago and saw the prototype. When things settle down I'll put up some pictures. You have. I believe, a new alternative now. Let me see what you folks can do with it. 
Regards
John W. G.

John W. Gudenas, Ph.D.
Professor of Computer Science

On Sep 16, 2008, at 9:14 PM, S&JY wrote:
I am wondering if the effect of moving the feedback coil up the secondary is equivalent to introducing some phase shift between primary and feedback 
coil.  If so, perhaps the feedback coil could be located in a more
reasonable lower position, and a phase shift network could be used to
achieve the same result?  It would be a good experiment to try.

--Steve Y.

-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On Behalf 
Of dr.hankenstein@xxxxxxxxxxxxx
Sent: Tuesday, September 16, 2008 6:06 PM
To: Tesla Coil Mailing List
Subject: Re: [TCML] VTTC Coupling
I used to run the feedback coil underneath the primary on my small 811A coils. Dr. Spark built a twin 833C coil several years ago, which Cameron later used as a reference for his coil and research, and placed his feedback coil higher up on the secondary. I duplicated Chris's coil in this respect and have found out that there is a sweet spot for the feedback coil which results in much longer sparks. Chris definitly has the knack for tuning a 833C VTTC. I would recommened his work, which can be found on his website! 

Woo
SNIP.................................SNIP


John W. Gudenas, Ph.D.
Professor of Computer Science


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