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RE: DC Tesla Coil - was rotary spark gap



Original poster: "Lau, Gary" <gary.lau@xxxxxx>

Hi Dave:

Winding a primary out of 24 gauge wire sounds like a bit too thin?
Granted, you won't get excessive heating with only a 75 Watt power
supply, but primary losses will still be significant.

I also use a two-layer (copper tubing) primary, but with a fixed
geometry and conventional tapping for adjustment.  See
http://www.laushaus.com/tesla/primary.htm.  The two-layer construction
is a great way to achieve a high inductance without an excessively large
diameter primary.

Gary Lau
MA, USA

> -----Original Message-----
> From: Tesla list [mailto:tesla@xxxxxxxxxx]
> Sent: Monday, November 29, 2004 9:41 AM
> To: tesla@xxxxxxxxxx
> Subject: DC Tesla Coil - was rotary spark gap
>
> Original poster: "David Thomson" <dwt@xxxxxxxxxxxx>
>
> Hi Gary,
>
> Thanks for posting your work online. Your designs are easy to follow.
>
> I haven't built a rotary gap yet. But I'm moving in that direction.
My
> next coil will be a small 75 watt DC coil. I'm going to experiment
with a
> variometer in the primary circuit for tuning. The variometer will be
> modeled after one of Tesla's designs involving two flat spiral coils
on a
> sliding brass rod. The centers of the coils will be connected through
the
> brass rod. The coils will be wound with 24 gauge 1:4 ratio flattened
magnet
> wire.
>
> I wound two 13" flat spiral coils on 3/16" Plexiglas, one with the
windings
> going the same direction and one with the windings going opposite
> directions. With just one 13" flat spiral coil, the inductance was
about
> 4.5 mH. With two flat spirals wound in the same direction at 3/16"
apart
> and connected through the center, the total inductance was just 1.11
mH for
> the entire wire length. With the same parameters but wound in
opposite
> directions, the total inductance was 121 mH. The opposite wound coil
has
> other interesting properties as well.
>
> I'll use the opposite wound coils on a sliding brass rod to adjust the
> inductance in the primary circuit since it will give the greatest
range.
>
> I think that because I'll have so much control over the primary
resonance
> that I'll just use a static gap to begin with. But since I have no
> experience with rotary spark gaps I can't help but wonder if I'm
missing out
> on an opportunity to significantly increase the frequency and overall
> performance. What do you think?
>
> Dave
>
> > -----Original Message-----
> > From: Tesla list [mailto:tesla@xxxxxxxxxx]
> > Sent: Sunday, November 28, 2004 5:10 PM
> > To: tesla@xxxxxxxxxx
> > Subject: RE: tungsten alloys for SG electrodes?
> >
> > Original poster: "Lau, Gary" <gary.lau@xxxxxx>
> >
> > Hi Dave:
> >
> > I've not attempted a spherical RSG contact, but I have attempted a
> > cylindrical contact, perhaps with a similar underlying motivation.
My
> > goal was to use as large a ROC as possible on the electrodes to
minimize
> > the gap at which the RSG would fire, so as to minimize losses.
This
> > attempt is illustrated on the lower half of my SRSG page at
> > http://www.laushaus.com/tesla/sync_gap.htm. I never did get that
gap to
> > work reliably. I have a half-baked theory that the larger
electrodes
> > resulted in a longer effective dwell time, and the RSG wanted to
fire
> > well in advance of actual alignment. In the end, the propeller gap
with
> > simple welding rod electrodes worked extremely well and better than
the
> > larger cylindrical electrodes.
> >
> > Regards, Gary Lau
> > MA, USA
> >
> > > Original poster: "David Thomson" <dwt@xxxxxxxxxxxx>
> > > I realize you're building a rotary spark gap, but the tungsten
balls
> > are
> > > excellent for a static spark gap. I brazed the tungsten balls
on the
> > ends
> > > of tungsten rods and they work great. The balls on McMaster
Carr are
> > grade
> > > C1/C2, which is very hard and doesn't pit.
> > >
> > > I'm now curious as to whether a spheroid contact would work with
a
> > rotary
> > > spark gap. I may try to build one.
> > >
> > > Dave
> > >
>