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Rotary Spark Gap

 * Original msg to: Wl-god-tw-at-society-dot-com
 * Carbons sent to: usa-tesla-at-usa-dot-net

Quoting <wl-god-tw-at-society-dot-com>:

> I am currently building a rotary spark gap for my coil and was
> wondering if there is an optimum number of breaks per second 
> for each coil.  

Yes, but the last thing your coil needs is a rotary spark gap. 
There are people out there who are exceeding four feet of spark 
with fairly simple static gaps. You don't need, nor want, a
rotary gap until you are running heavy transformers.

> My coil has approx 500 turns of #26 plastic insulated wire(I
> will be replacing this with #28 magnet wire soon) wound on a 4"
> PVC pipe. 

You want your wire gauge to get thicker, not thinner. You should
be looking at 22 AWG, maybe 24 AWG. Going to 28 AWG is the wrong
direction. If you want greater inductance and lower operating
frequencies go with a larger diameter coil form, don't use
thinner wire.

> Our primary coil is 3 turns of #9 plasic coated (600V) wire of
> approx 8" diameter (This will soon be replaced with #18 plasic
> coated wire rated at 40kV).  

You want to operate with your primary tapped out at quite a few
more turns. Also you are planning on building the same problem
into your primary as in your secondary. You want to use a heavier
conductor, not lighter. Changing from 9 AWG to 18 AWG will all
but cripple your primary efficiencies. You don't need, nor do you
want, heavily insulated HV wire on your primary unless you are
designing and building a stage coil. For a practical hobby coil 
you want a large primary wound from copper tube, or strap. Even
aluminum flashing strap will work great on a small hobby coil.

> My capacitor filled with salt water and there are 16 salt-water
> filled beer bottles in the water.  The electrodes in the beer 
> bottles are connected by means of a metal plate.  Another metal
> plate has been placed underneath the bottles.  Both plates have
> large terminals which wires can be connected to.  

This is a classic salt water capacitor. These are great for
getting beginners sparking. They are cheap, easy to build, and
they hold up. 

> I use an oil furnace transformer rated at 10000V and 22MA.  

This is a good match to your capacitance, but does not deliver
much power. This coil would probably benefit by bumping your tank
circuit voltage up to 12 kvac from a neon sign transformer.

> Any help you can offer with the rotary spark gap or any other 
> suggestions you can offer would be appreciated.  

Drop the rotary and concentrate on getting your input power and
efficiencies up.

> Also any information you have about making a transmitter and 
> reciever for wireless power X-mission.  

Simple enough to do, you need to wind a second coil with a lower
frequency. Since you already have a four inch coil, how about
designing a six inch to work as the receiver? You load discharger
on your four inch coil until spark will not break out even when
the coil is in good tune. The new frequency of the four inch
system with discharger needs to be lower than the bare wire
frequency of the six in coil. Tune the six inch coil to match the
frequency of the four inch system by adding discharger, then
ground the six inch coil. With the frequencies matched the six
inch coil will pick up and resonate on the ground current from
the four inch system. This will accomplish the simplest
experiment in wireless power transmission.

Note:  RF transmitters of this type may require special
enclosures (Faraday cage) in order to operate legally. 

Richard Quick


... If all else fails... Throw another megavolt across it!
___ Blue Wave/QWK v2.12