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Re: [TCML] VTTC New Grid Coil Geometry

Dr. John,
I used a still different grid coil arrangement on my 36" spark Tesla coils. Both used flattish primaries. The grid coils were very close to the secondary 
and were solenoid coils only 1" high and about 1/2" wider diameter than
the secondary. The grid coil was in the same plane as the primary (in a 
sense).  The
grid coil consisted of two layers of winding, about 19 turns total of
18awg pvc insulated wire.  I raised or lowered the grid coil to adjust
things.  These coils were very tricky to adjust, and they never gave
swordlike sparks, they always gave fuzzy sparks.  I don't know if the
arrangement offered any real advantage or disadvantage overall.

Then on my TT-27 VTTC, I attempted to use a flat primary and
put the grid coil along the outside of the primary.  This worked
very poorly.

I like your idea of a hidden grid coil.

Cheers,
John
-----------


-----Original Message-----
From: Dr. John W. Gudenas <comsciprof@xxxxxxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Wed, 17 Sep 2008 12:01 am
Subject: 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 lowes
t 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 wondering20if 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 
 0D
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