Re: Sparks - Bright in the middle, how to verify it.

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Steve Cook by way of Terry Fritz <twftesla-at-uswest-dot-net>" <Steve-at-g8cyerichmond.freeserve.co.uk>

I seem to remember that about a year ago someone did try some high frame
rate filming, but can't locate the info at the moment, and I don't know what
the results were, it might be worth looking in the archives.

----- Original Message -----
From: Tesla list <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Saturday, January 20, 2001 6:33 PM
Subject: Re: Sparks - Bright in the middle, how to verify it.


> Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-uswest-dot-net>"
<jimlux-at-earthlink-dot-net>
>
> The same phenomenon, in a slightly different form, is also evident on Van
> deGraaf generators.  Sparks tend to grow from one polarity better than the
> other.  When you run your coil on AC, the polarity of the top is reversed
> every half cycle.  On one half cycle, the spark is growing from the ground
> rod towards the terminal, on the other half cycle, it is the opposite.  If
> your spark length is 2/3 the length of the gap between the terminals, in
the
> middle third, you'll see twice the brightness.
>
> I'd love for someone who has a very fast video camera (one of those 1000
> frames/second jobs) to take a look at TC sparks.  When I worked in the
movie
> business, we used to do shoots where for super slow-mo they used to run
> cameras at 300 fps or faster (thousands of frames/second), but I couldn't
> ever work a deal where they'd film my little coil as an experiment.  There
> was always a schedule conflict, or I didn't have the cash for the film and
> processing. At $1/foot, 300 frames (around 25 feet) costs about $25, so
> burning a minute of film is a pretty pricey experiment.  Production
> companies may be profligate with star salaries and cushy seats for the
> advertising agency guys, but they're pretty stingy with the below the line
> costs like film, processing, and staff.
>
> However, there are a lot of the new Kodak and NAC motion analysis systems
> with very fast CCD cameras hooked to a computer around now and the rental
> prices are coming down.  Maybe next time there is a "teslathon" in the
area,
> I will rent one.
>
> You might also be able to improvise something using the fast shutter mode
on
> consumer video gear.  It has a shutter speed of 1/10,000 second (or so),
but
> the frame rate is going to be 60 Hz.  You might get useful data if you
could
> slowly vary the phasing of the power driving the coil relative to that in
> the camera (actually, the camera probably isn't that stable, so it would
> drift by itself). You're not going to get the ideal, a series of frames on
> the same spark, but, you might get a feel for spark growth in general, as
a
> function of time past "bang".
>
> A DC coil running off a well filtered supply might also be easier to
> synchronize to
> ----- Original Message -----
> From: "Tesla list" <tesla-at-pupman-dot-com>
> To: <tesla-at-pupman-dot-com>
> Sent: Saturday, January 20, 2001 8:36 AM
> Subject: Re: Sparks
>
>
> > Original poster: "Charles Hobson by way of Terry Fritz
> <twftesla-at-uswest-dot-net>" <charles.a.hobson-at-btinternet-dot-com>
> >
> > Hello all,
> >
> > Placing a grounded rod about 300mm from the terminal of my coil I get
nice
> > sparks similar in appearance to lightning. At the center of these sparks
> > there is a 25mm segment which is much brighter than the rest. I would be
> > most grateful for an explanation for this phenomena.
> >
> > Chuck
> >
> >
> >
> >
>
>
>
>