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Re: Tuning and Performance Questions (6.5" coil)

Brian,

Your performance sounds pretty good to me.  It seems to me that your
safety gap spacing is a bit conservative, but then again I just toasted
two caps :-)

Does the height of the toroid change the tune at all?  You said that your
performance dropped, but could that have been due to tuning?  

Chip

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
 Chip Atkinson 
 http://www.pupman-dot-com 
 --- If I can't fix it, I can fix it so it can't be fixed --
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

On Mon, 2 Nov 1998, Tesla List wrote:

> Original Poster: "Basura, Brian" <brian.basura-at-unistudios-dot-com> 
> 
> Hello,
> 
> I've been tuning my 6.5" coil and have reached a new personal best of
> consistent 60" strikes to a grounded rod with 1.6kva input.
> 
> I have two questions/concerns:
> 
> 1) Toroid height affects my coil operation dramatically.  Not just spark
> length but consistency and smoothness of operation. With the toroid set at
> it's current height above the secondary, I get a faint purple corona from
> the top of the secondary down to the strike rail.  Is this OK? If I raise
> the toroid 1/2" I get breakout from the top turns of the secondary.
> Lowering the toroid 1/2" destroys performance.
> 
> 2) My capacitor bank consists of four rolled poly caps in a parallel/series
> arrangement for a total of .042mfd with a total dielectric thickness of
> .072" (spread over two capacitors).  I also have a safety gap across the
> capacitor bank.  It's made of two 1/4" stove bolts with their heads facing
> each other and a gap of .3"  When the system is in tune my safety gap starts
> to fire whenever my variac voltage gets to 100v (when out of tune it fires
> much sooner).  Am I being too conservative with this gap?
> 
> 3) Performance was in the 34-36" range until the last marathon tuning
> session where I did a lot of work on toroid height and fine tuning of the
> tap.  I now achieve consistent 60" strikes.  Is this good performance for
> 1.6kva into the system or should I look for more?
> 
> Settings:
> 
> Current limited to 17amps using three MOT's (with shorted secondaries) and
> 6.2 ohms (all in parallel).
> Maximum Variac setting is 95volts
> Primary Tap is at 7-5/8 turns
> Spark Gap is RQ type (with a blower) using five gaps for .150"
> Secondary windings start .5" above the primary
> Toroid is 4.5" above the top secondary winding
> 
> Coil specifications are as follows:
> 
> Primary Transformer
> Input Voltage		95 VAC
> Input Current		17 Amps
> Output Voltage		12,000 VAC (-at-120v in)
> Input frequency		60 HZ
> 
> Primary Design
> Inside Diameter		9.5 inches
> Average Radius		8.88 inches
> Wire Diameter		.025 inches
> Total Diameter		26.0 inches
> Wire Spacing		0.25 inches
> Wire Length		79.0 feet
> Total Turns		17.0
> Secondary Res. Freq.	124.2 khz
> Inductance		0.1407 mh
> Primary Cap to Res.	0.0117 uF
> Angle of Windings	0.0 degrees
> 
> Secondary Design
> Diameter		6.50 inches
> Radius			3.25 inches
> Winding Length		27.5 inches
> Circumference		20.42 inches
> Wire Gauge		22 awg
> Wire Length		1698 feet
> Turns per Inch		37.4
> H/D Aspect		4.23
> Inductance		34.56 mh
> Resonate Frequency	248.1 khz
> Medhurst_K		0.72
> Res. Freq. w/Toroid	130 khz
> Self_C			11.91 pf
> 
> Top Load
> Type			Direr Duct Toroid
> Size			6" chord x 30" diameter
> Top Load C		32.1pf
> 
> Tank Capacitors
> Number of Capacitors	4
> Capacitor Configuration	Series/Parallel
> Type			Rolled LDPE
> Overall C		.042 uf
> C of each unit		.042 uf
> Dielectric Constant	2.0
> Plate Length		120 inches
> Plate Width		14 inches
> Dielectric		.036 inches (6-at-.006")
> 
> 
> Pictures available at the following:
> http://www2.hughes-dot-net/~brianb/teslahome.html
> 
> Thanks in advance (hope this isn't too much information)
> Brian D. Basura
> 
>