RE: AMRAD Spark Gaps

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

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

> ----------
> From: 	Tesla list[SMTP:tesla-at-pupman-dot-com]
> Sent: 	Thursday, December 21, 2000 6:37 PM
> To: 	tesla-at-pupman-dot-com
> Subject: 	AMRAD Spark Gaps
> 
> Original poster: "Steve & Jackie Young by way of Terry Fritz
> <twftesla-at-uswest-dot-net>" <youngs-at-konnections-dot-com>
> 
> Ed,
> What keeps the sparks from tracking across the fiber washer edge, thus
> carbonizing it and ruining the gap?  Why does the gap stay in the
> center of
> the disks?  Are the disks thicker in the middle and thus closer
> together in
> the middle?
> --Steve
> ----- Original Message -----
> From: Tesla list <tesla-at-pupman-dot-com>
> To: <tesla-at-pupman-dot-com>
> Sent: Wednesday, December 20, 2000 9:56 PM
> Subject: Re: Spark Gaps
> 
> 
> 
> > An AMRAD quenched gap is an antique, surplus from WWI, and used in
> > spark transmitters!  Very rare now and prized by old junk collectors
> > such as I am; the one I have is the only one I have ever seen in
> > person.  AMRAD was the name of the outfit that made this particular
> one
> > and ended up with a bunch on its hands when war contracts were
> > cancelled. They then tried to sell them for amateur use, but the
> marked
> > dried up as spark went out of style.  As for what it is, easier to
> send
> > a picture than describe it, but its of conventional construction for
> > that period.  Essentially it consists of many flat copper gaps in
> > series, perhaps 1-1/2" in diameter and spaced about 1/32" apart.
> They
> > are separated by fiber washers and the whole assembly is held
> together
> > by a clamping screw.  When it runs the oxygen inside is quickly used
> up,
> > leaving mostly nitrogen.  The gap chambers are sealed from the
> > atmosphere by the fiber washers, with the net result that the copper
> > surfaces stay clean and pink after many hours of running.
> >
> > This type of quenched gap was used for the same reasons they are
> > valuable for TC's.  They turn off fast......
> >
> > Ed
> 
> 
> 
>