Re: AMRAD Spark Gaps

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

Original poster: "bob golding by way of Terry Fritz <twftesla-at-uswest-dot-net>" <yubba-at-clara-dot-net>

Hi Ed ,Terry ,all,
    I tried to make one of these out of old hard disk platters udsing mica
(the sort 6that is
used as windows on the end of the waveguide on a microwave oven) as the
washers.  I found that
they arced in one place and stopped working after a short time. I didn''t
know about having them
thicker in the middle at the time. Maybe that was why they failed. Might
have another go with
this new  info. Thats what I like about this list. You can try something
fail them someone else
picks up the idea and we are all off again. Does seem to me that the gap is
the area that lends
itself to the most experimentation. I suppose it is the most difficult area
to model and get
repeatable results.
cheers
bob golding

Tesla list wrote:

> 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