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airblst.txt

This gap offers several advantages over many of the gaps I have
studied. It frees the coil up from any electrical utility
required when fans or blowers are used on a static gap. This is
also true when a rotary gap system has been used with a neon
transformer power supply, as this gap can replace a rotary in
this application and give better performance. This gap has very
high Q and gives extremely low quench times. The performance of
this gap on coils powered by neon sign transformers is second to
none. If you run neons, and you want the longest spark at any
cost, then this is the gap for you.

The system consists of two electrodes cut from 1 inch brass bar
stock. The electrodes are 1-1/2 inches long by 1 inch diameter. 
The back side is machined one inch deep to accept a 3/8 inch
threaded brass dowel. The face of the electrodes are flat and
polished. The electrodes weigh 4 & 3/4 ounces each and sink a lot
of heat without requiring cooling fins. Beneath the gap, I
mounted a 1/2" ID pipe fitted with a standard male air coupling
at one end. I hook the air feed pipe to a two-stage piston air
compressor, and using a regulator, blow 20 psi (minimum) of air
through the gap electrodes from the bottom up. It quenches
extremely well.

With the arc shielded during operation, the compressed air blows
a clearly visible jet of hot ions upwards from between the gap.
The flame extends one to two inches high. Even after 15 minutes
of operation at 2 kw, the electrodes are barely warm to the
touch.

This configuration offers several advantages: 

(1) Gap distance can be adjusted precisely and quickly by
rotating the electrodes on the threaded rod, as opposed to most
multiple and quench gaps. (2) Higher power can be accommodated
simply by increasing the air feed pressure (or CFM). (3) A single
pair of strong magnets can be mounted on either side of the brass
gap to assist quenching at even higher powers by dispersing ions
away from the arc and into the high speed airstream. (4) The
electrodes can be quickly removed for examination and/or cleaning
without disassembly of the gap. My electrodes require a light
burnishing with #1200 sandpaper after every hour of operation.
The procedure takes less than 5 minutes.

Using a diaphragm compressor, it is not necessary to regulate the
output. Just hook up and run the compressor flat out. The lower
output (CFM) of the diaphragm compressor reduces quenching, but
can be overcome by using an old portable propane tank in series
as a holding tank. A full tank of air will supply air flow for
quenching at higher power.    

This gap hisses like a large snake when the air feed is turned
on. When you hit your power switch and feed juice to the coil
this gap will take off. The noise is similar to a chain saw run
full throttle without a muffler. Indoors, hearing protection is a
must. Outdoors, your neighbors are sure to complain!