Re: spark gap muffler? -> More tuning questions.

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

Original poster: "Barton B. Anderson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <tesla123-at-pacbell-dot-net>

Hi Bill,
(comments intersperced),

Tesla list wrote:

> Original poster: "Bill Vanyo by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<vanyo-at-echoes-dot-net>
>

> Also, my spark gap is adjustable, but I'm thinking maybe I don't
> understand the principle behind how to adjust it.  Basically, what
> effect does having the gap wide versus narrow have?  I've noticed that
> when it's wide, it seems to fire more erratically.

The total gap width determines the firing voltage. Wider means a higher
voltage for gap
conduction. The 180mA charging current and cap size determines the
frequency the gap will
conduct.

>  If the gap is set too narrow, how does that affact streamer length?

Fires at a lower voltage. Less power to the streamers. If the gap is too
wide, it takes longer
to charge to the increased firing voltage. It runs the risk of killing your
30kV cap. 30kV is
on the low side considering Vp-p voltages which can occur from time to
time. I would keep the
gap relatively narrow to be safe.

> Is there anything else I should look at?  I got sparks about 2 feet max
> in a good breeze.  Was it just the breeze, or is something else way off?
>

You should be capable of 7.4ft at max efficiency. So, there are areas for
improvement. I didn't
see anything standing out in your specs below. I showed 7.7 turns on the
tune point, but that
will vary with top load and placement. You are in the ballpark already.
What does standout is
the large cap size with a static gap. You would probably have better
performance and stability
of the charging current and voltage with an SRSG. Another item is the
variac. Did you remove
the shunts in the NST's in order to adjust current externally? Kind of
curious why your using
the variac.

Take care,
Bart

>         Thanks,
>         Bill V.
>
> BTW, the specs again are:
>
> Power Supply: Three 15/60 NST's, with Terry's protection filter on the
> high voltage side, and redundant line filters and a 50 amp variac on the
> 120V side.
>
> Capacitor: A Maxwell 30 kV, 0.06 uF cap (model # 37321).
>
> Static Spark Gap:  9 copper pipes mounted in a blower box, with
> adjustable spacing.
>
> Secondary: 1000 turns of 22 awg, 6.5" (closer to 6 5/8) diameter, 27.5"
> winding length.  Countless coats of polyurethane.
>
> Primary (just rebuilt): Flat spiral, 10 turns of 1/4" copper tube, 1/2"
> spacing on
> centers.  Inside diameter 9.5".  Tapped between 6 and 7 turns.
>
> Toroid: Aluminum dryer duct, 8 inch cord with 24 inch center to center
> spacing.
>
> Ground: 32" segment of copper clad iron ground rod.
>
> All interconnects are 1/4" copper tubing, with 1/16" thick polyethylene
> insulation (3/8" o.d., 1/4" i.d. tubing), except I use welders cable to
> my primary tap clip (both heavy and very flexible),
> and 15kv rated high voltage wire from the power supply to either side of
> the spark gap.
>
> Misc: Strike rail (open loop).
>
> Tesla list wrote:
> >
> > Original poster: "Barton B. Anderson by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <tesla123-at-pacbell-dot-net>
> >
> > Hi John, Bill,
> >
> > Just to add to John's post regarding gap noise and spark noise (I'll be
> brief):
> >
> > When I first built my coil, the gap made most of the noise. As changes were
> > made
> > and knowledge was being soaked in and applied, the coil began running more
> > efficient including longer sparks. One day I noticed the spark was the main
> > sourse
> > of noise. If the gap is making most of the noise, then the coil is not
> > getting the
> > power to the spark and it is being lost elsewhere.
> >
> > Bart A.
> >
> > Tesla list wrote:
> >
> > > Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> > <FutureT-at-aol-dot-com>
> > >
> > > In a message dated 5/24/01 10:31:10 AM Eastern Daylight Time,
> > > tesla-at-pupman-dot-com writes:
> > >
> > > > Has anyone invented such a thing?
> > > >
> > > >  Basically, I'm wondering if there's any way to make a silent or
somewhat
> > > >  quiet spark gap for a medium to high power coil.  I'm currently
using a
> > > >  static gap, but would consider other designs.
> > > >
> > > >   - Bill V.
> > >
> > > Bill,
> > >
> > > There exists so called true static quench gaps that are quiet, because
> > > the sparking chambers are sealed.  But most of the noise from
> > > a Tesla coil is from the output spark streamers anyway.  What
> > > real benefit would be gained by quieting the gap?  The overall
> > > coil would still be very loud.
> > >
> > > John Freau