Re: New coil troubles

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: robert heidlebaugh <rheidlebaugh@xxxxxxxxxxxxxx>

Just a second thought about the vertical portion of your primary. If tuned
correctly,,, If tuned correctly you should not have an arc problem. You can
use a short lendth of PVS pipe as an insulator extending 1 inch above and
below your vertical portion inside. Tube coilers often do this so they can
get close coupeling without arcing.
     Robert    H
--


> From: "Tesla list" <tesla@xxxxxxxxxx>
> Date: Mon, 20 Dec 2004 22:58:25 -0700
> To: tesla@xxxxxxxxxx
> Subject: Re: New coil troubles
> Resent-From: tesla@xxxxxxxxxx
> Resent-Date: Mon, 20 Dec 2004 22:58:53 -0700 (MST)
>
> Original poster: "Barton B. Anderson" <tesla111@xxxxxxxxxxxxx>
>
> Hi Chris,
>
> Your problem is likely tuning and coupling. There is more info needed to be
> completely accurate. I guessed at wire size to be #24. With toroid, the
> resonator should tune at 335 kHz. Thus, with your .058uF cap size, you need
> 3.9uH of primary. I couldn't model your complete primary since it is part
> helical and flat. I did note that of you have 4 turns of helical and this
> coil would tune in at 4.7 turns, so it should tune in somewhere around the
> first "flat" turn which I believe is turn 5.
>
> You don't mention the sec height in relation to the primary. So, "if" the
> bottom winding were even with the first bottom turn of the helical
> secondary, your coupling would be high, even with only 4.7 helical turns
> (0.163). Simply raising the secondary 1" will drop this value to 0.125 (as
> a reference since I don't know actual positions). Sparks breaking out of
> the center of the secondary indicate the voltage at the breakout position
> (be it a voltage node or whatever) is too high. Because of it's position, I
> suspect your out of tune.
>
> I recommend positioning the secondary so the bottom turn is center to the
> helical and tune the coil at that position. Depending on your actual cap
> value, the inductance needed may be slightly more or less than 4.7 turns.
> You can adjust coupling higher for performance improvement after you are
> sure you are tuned in.
>
> Take care,
> Bart B.
>
> Tesla list wrote:
>
>> Original poster: "Christopher" <cpfortun@xxxxxxxxxx>
>>
>> Hi,
>>
>> I'm writing in regards to a new coil I recently constructed. The specs are
>> as follows : 9kv franceformer....180mA, SRSG, a total of 24 caps.....8
>> seriesed 3 legs paralled.. (.15MFD at 2000V each) making for a total of
>> .058MFD, the primary coil consists of 11 turns......the first four turns
>> are vertical and the other seven are horizontal.....I am using 1/4" soft
>> copper tubing "OD" and the spacing between the turns is 1/4", the
>> secondary is 3" "OD" with a total height of 24 1/2" with the magnet wire
>> wrap length meausuring 22 3/4"........on top of the secondary is a spacer
>> which holds the toroid a total of 3 1/2" above the secondary, the toroid
>> measures 19 1/2" by 4". The electrical connections are as follows : xfmr
>> is in parallel with the caps, on end of the caps is connected straight
>> into the primary coil, the other end of the caps is connected to the spark
>> gap (one side of the spark gap), the other side of the spark gap is used
>> for the tapping point of the primary coil, (The safety gap, secondary
>> coil, and strike rail are connected together as one source going to RF
>> ground). If there may be any questions that need further explaination in
>> regards to the mechanical or electrical setup let me know.
>> Moving on to my troubles.......when I initially constructed my coil I
>> allowed for a 5" inside diameter between my secondary and
>> primary........which left a total of 1" spacing between these two. This
>> wasn't enough because I was getting sparks from my primary to my secondary
>> on the vertical turns. So I redid my primary and made for a 6" inside
>> diameter needless to say this fixed the problem and decreased the tapping
>> point. The problem now is that my streamers are extremely short, maybe 10
>> inches, and I am getting sparks that start about the middle of my
>> secondary which strike down to my primary. The tapping point has no effect
>> on the size of the streamers no matter where I tap it, they are the same l
>> ength. I tried raising the secondary gradually but has no effect on
>> eliminating the sparks from the secondary to the primary.....I either get
>> sparks or nothing at all. The spark gap is set up as 4 stationary
>> electrodes and 1 rotating electrode. I am also using a variac with this
>> system. After the spark gap has been turned on and operated up to full
>> speed, I slowly turn up the variac from 0 V to 120 V, this is the reaction
>> of the spark gap....all four will fire, then two will fire and them the
>> other two will fire almost instantaneously, then only two of the
>> electrodes will fire until I reach 80 volts and then all four will kick in
>> again and stay on up to 120 volts. Does this sound pretty normal for the
>> operation of it ? Anyhow that's enough for now.
>> Any feedback in regards to the sparks from the secondary to the primary
>> and just the overall setup and operation of this unit will be greatly
>> appreciated :)
>> Thanks,
>> Chris F.
>> <mailto:cpfortun@xxxxxxxxxx>cpfortu n@xxxxxxxxxx
>>
>>
>>
>>
>>
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