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Re: Dielectric Constant?/Gasoline Arc

Hi Harvey,

At 04:41 PM 6/4/00 -0700, you wrote:
>From a quick
>review of taping, the pause frames seem to indicate
>that when an arc is seen on the primary arc gap, none
>is present on the secondary terminals. Is this to be
>indicative of what a mistuned system will act like in
>time? From what I have been able to observe by taping
>a scope sweep rate of 2ms/div the pause frames  of a
>VCR recording appear to coincide roughly to the 16.6
>ms cycle time of a 60 hz signal. Now if this is true
>then that most static gap systems fire at 120 BPS, 

If your coil is run from 60Hz, then the gap firing rate should be somewhat
synced with the 60Hz even if it is resonant charged.  When the line voltage
is at a peak, the charging rate will also be at a peak.  It would take a
rotary sync gap for it to be perfectly in sync, but the general gap firings
still occur during the times of maximum charging, more or less.

>I were to film a tuned coil system, shouldnt I still
>expect to see a time difference between the primary
>firing and that of the secondary? doesnt that
>secondary firing have to be at the same BPS and ninety
>or possibly even 180 out of phase with the primary
>firing? If it were close to 180 as current actions
>show in a parallel resonance, those arcs filmed in
>time should be near simultaneous, correct? Only asking
>for comments by those more in the know.snip...

The secondary arcs may form to full length over several discharge cycles as
the air heats up and all.  But assuming that the top arcs at the secondary
voltage peak, the time can be fairly accurately calculated between the gap
firing and the secondary peak.  It is 1/k half cycles.  Thus the time is:

	t = 1 / (2 x k x Fo)

t = Time from gap firing to secondary voltage peak.
k = primary to secondary coupling coefficient.
Fo = System resonant frequency

for the system described at:


And from the graphs at:

I would guess 22uS from the graphs.  The equations gives:

	1 / (2 x 0.1753 x 111700) = 25.5uS

So the equation is "close enough" to calculated this time delay for a given

So the question is now, Can your camera detect a time delay of 25uS?

Assuming a frame rate of 33333uS and the persistence of the photo detecting
elements in the camera along with the various other delays, I think it
would be very hard if not impossible.  However you may be able to see the
gap firing "flicker" and a secondary strike to ground "flicker" in a single
scan that may be of use.  The camera is also probably "interlaced" which
really makes things messy.   You are probably better off trying to single
trigger your scope, with the intensity turned up, to catch the event on the
scope's prosper on the video.  Ideally, you would get a digital scope which
would make all this painfully easy.  All those cursors and digital readouts
would be of great benefit for your work.  But they are not cheap :-(

As far as the gasoline experiment goes, your on your own there! =:-O

That's my 2 cents...