Re: AMRAD Spark Gaps

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

Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-uswest-dot-net>" <evp-at-pacbell-dot-net>

Tesla list wrote:
> 
> Original poster: "Oxandale, Terry by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <Toxandale-at-SPP-dot-org>
> 
> I made one of these gaps many years ago (it's in an old TCBA issue with
> a picture) back in the late '80's. With my 5" coil, I almost doubled the
> length of discharge with this device replacing the normal stationary
> spark gap. Unfortunately, they get hot very quickly, and with the
> insulators I was using between the plates (rubber impregnated cardboard
> used for gaskets in the oil circuit breakers used for distribution), I
> would have to replace them about every hour of run time due to the high
> temperature carbonizing of the gasket. My plates were simply brass discs
> (2" dia X .040") that were pressed to resemble the shape of a dinner
> plate (convex with flat edges). Then the two concave sides were place
> face-to-face together as a unit, and then these units were stacked
> together separated by the insulating gasket between each unit (about 6
> gaps total I believe). I had to devise a frame that could use a large
> fine thread bolt as a means to press all these units together tight
> enough to keep them air tight. The whole thing wasn't any larger than a
> Reubic's Cube, and was quite nice for a lower powered unit (500 to 1000
> watts) with no spark light or noise. If one was to machine the brass
> discs from large enough stock to have heat sink fins, as single piece
> units with a high temp gasket material between these units, these would
> be ideal SG for small coils.
> 
> Un-Terry

	Very interesting method of construction!  Overlooked that article.  Do
you remember which issue?  Mine are not filed very well....  Any idea
what temperature that gasketing material will withstand?  As you saw,
I'd like to replace the gaskets in the gap I have and wonder if that
would be suitable, and where you got it.  Running at about 600 watts the
fins in this particular gap don't get too warm to touch, so suspect the
temperature at the washers isn't very high either.  That's with
convection cooling; should be much cooler with a small fan blowing on
it.

	If you made those plates on a press, seems to me it would have been as
easy or even easier to use copper.  In thinking about it, I would
suspect that with some fairly simple tooling one could crank the
individual elements out pretty quickly, and sell kits for home
assembly.   After looking at some of the workmanship on different web
sites, think this would be childs' work for some of these guys, although
perhaps they aren't interested in such low power operation.

	On the general subject of quenched gaps, in the old publications one of
the advantages of using them is said to be the fact that they could be
used at much lower voltages than rotaries.  Might be interesting to
follow up on that.

Ed