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Re: Gaps



At 10:10 PM 2/1/97 -0700, you wrote:

>> Subject: Gaps

<snip>

>Mr. Curtis describes what he calls a Quenched Gap beginning on page 41. It
>consists of two LARGE, Heavy, Thick, pieces of metal that are cylindrical
>in shape, with the facing ends ground and polished flat. The machined ends
>are then placed from 1/1000 to 1/100 of an inch apart. Due to the massive
>way it is built it can sink a fair amount of heat. This keeps the
>electrodes cool and allows for hundreds to thousands of individual
>discharges per AC cycle. This does not affect the resonant frequency, but
>does affect the nature of the discharge from the secondary. Mr. Curtis is
>lavish in his praise of this spark gap over all other types. He says it
>produces a series of "very short, clean, and nearly undamped surges". He
>mentions that as it heats up it deteriorates in performance. Today we would
>probably force air cool the device. It appears from the description that
>there is no need to force air THROUGH the gaps. (They are very close
>together!)
>
>By the way, these things were quite heavy and massive, with face diameters
>of three inches and more, and thicknesses of about an inch and a half
>(minimum), and greater. The sheer mass causes the heat to be removed
>rapidly. The large parallel surface area allows for MANY conduction paths,
>and thus high RF currents.
>
>I do not have the facilities here to machine such a beast, but there may be
>some of you out there who have access to such machinery as large lathes,
>etc.  Does anyone know if any Coiler has built such a quenched gap and
>reported on its performance? 

I have a set of gaps from an old dithearmy (sp?) machine, that seem to operate
much as you describe.

There are four 3/4" Dia copper rods with massive copper cooling fins attached
to each rod. The rods are individualy adjustable to no more than 1/32" or so
per gap. Two sets of these gaps were used for a total of eight gaps.

A 12" fan blew air across the fins and gap system to cool them down, total
system power was 2.5 Kw 

Only 5KV was applied to the system, so the gaps were VERY tight to get proper
operation. You could look into the gaps and see a mass of sparks between the
gaps, not just one at a time. 

I rewound a new secondary and primary at attached it to the system and with 
a 1" ball electrode got about 12" to 18" spark...

It looked a LOT like a tube coil, more corona like, with many fans of arcs 
radiating out...

I'd say the gaps worked great, but quite a bit diffrent arcs than with a air
blast gap. Likely I was gettting "undamped surges" and more of a CW output
than your basic rotary or static gap.

I'm hopeing to run more experiments with these gaps this spring, once the 
snow melts.

Daryl