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Re: text of july 1964 popular electronics article on tesla coils (fw d) (fwd)

Esondrmn-at-aol-dot-com wrote:
> 
> In a message dated 97-03-04 07:47:53 EST, you write:
> 
> << From: William Noble <William_B_Noble-at-msn-dot-com>
>  To: Tesla List <mod1-at-pupman-dot-com>
>  Subject: RE: text of july 1964 popular electronics article on tesla  coils
> (fw d)
> 
>  What bugs me about this isn't that the coil didn't work - I think I
> understand
>  the tuning part now, what bugs me is that the cover of the magazine has a
>  photograph of the coil working.  So, it seems to me that I ought to be able
> to
>  duplicate that, even if it's a crummy design.  - I'm using a commercial
>  capacitor, not a plate of glass, maybe that has something to do with it.   I
> 
>  did try the following experiments:
> 
>  1. added a metal toilet float to the top - small increase in arc, maybe -
> hard
>  to tell
>  2. wrapped primary around a vinyl sheet rolled into an 8" diameter tube, and
> 
>  spread the windings out to about 1/2 inches apart.  no change.
>  3. tapped the primary (I wound 30 turns total) at turns 20, 15.  Small
>  improvement at turn 20, 15 about the same.  much better if I ran 1o turns -
>  e.g. turn 30 to turn 20.  about the same at 5 turns (e.g. 15 to 20).  At the
> 
>  smaller turns on the primary configuration, the secondary would arc through
>  the vinly (.30, two layers) to the primary from about the midpoint of the
>  secondary.  These arc were longer than I could draw off the top. This
> confirms
>  to me that the coil is about twice as long as it ought to be.
>  3. messed around with the length of the spark gap.  no effect - either it
>  worked or it didn't - tuning the arc was ineffective.
> 
>  I haven't tried giving the secondary a good ground - per my prev post, the
>  schematic has pri low side and sec low side tied together, so given that the
> 
>  CT of the sign Xformer is also grounded, this is impossible.  I will try
>  isolating pri and sec and grounding Sec low side to Xformer case and see
> what
>  happens.
> 
>  I think I may also try making a plate glass capacitor exactly like the
> article
>  - that (it says it's .00027) is about triple what my capacitor seems to be
>  labeled.  Maybe I'll also meaure my capacitor and see what it's value is -
>  since the label is corroded, I could have misread it.
> 
>  (and, yes, I'll make a half length secondary soon, but first, there is this
>  small matter of a trip to abu dhabi...)
>   >>
> William,
> 
> Sounds like you are making some progress.  You really aren't going to make a
> lot of headway as it sits because it is so far out of tune.  If you cut the
> secondary in half, you will still need a .006 mfd cap.  These are resonant
> systems and just don't perform unless the tank circuit and the secondary are
> in tune.  I would suggest making a new flat pancake primary out of 1/4"
> copper tubing, 14 turns with about .30" spacing between turns and 6.0" inside
> dia.  This will allow some room for tuning so you can add a toroid.  You
> should be able to get 12" to 16" sparks out of this thing with a 12kv 30 ma
> transformer.
> 
> Have fun in the desert.
> 
> Ed Sonderman