Re: spark gap

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Yurtle Turtle <yurtle_t@xxxxxxxxx>

For steady state operation, just look at how aluminum
heat sinks are constructed. They don't go for thermal
mass; instead they go for lots of surface area.

Adam

--- Tesla list <tesla@xxxxxxxxxx> wrote:

> Original poster: "Gerry  Reynolds"
> <gerryreynolds@xxxxxxxxxxxxx>
>
> Hi Bart,
>
> I think what you say is good.  Advantage of solid is
> high thermal
> mass. Advantage of tube is high surface area and low
> cost.  If
> cooling was such that air could flow axially down
> the tube as well as
> across the gap maybe thermal mass would not be an
> issue.  Seems like
> thermal mass only delays arrival of steady state
> temp and if cooling
> was enough to dissapate the generated heat at a
> reasonable temp then
> time to steady state may not be an issue.  Of course
> I havent tried
> this at 120ma  but at 60ma my hollow static gap
> never got warm.  A
> lot depends on how many segments one distributes the
> total gap over as well.
>
> Gerry R
>
> >Original poster: "Barton B. Anderson"
> <bartb@xxxxxxxxxxxxxxxx>
> >
> >Hi Tim,
> >
> >You'll probably get various opinions based on our
> experiences. For a
> >120mA NST, an SRSG would be of benefit. However,
> for a static gap, I
> >prefer solid vs hollow myself. I've found hollow
> gaps heat very
> >quickly and require quite a lot of air to keep
> cool. One down side
> >of hollow gaps is tap connection (it's hollow). A
> solid rod stock
> >gives the added ability to tap a hole in the end of
> each electrode
> >for connections. I'm currently running a solid
> brass gap and can run
> >it indefinitely with air flow. With the same air
> flow on a copper
> >hollow gap, I couldn't. It took a little time, but
> eventually the
> >sparks get shorter and shorter over time as the gap
> heats up and
> >lowers the voltage required to arc the gap. Static
> gaps are very
> >heat dependent for arc voltage stability. Probably
> the #1 issue. The
> >radius of curvature does play a role but good gaps
> can be built with
> >all the sizes you've mentioned with a 120mA supply.
> >
> >With that said, realize that hollow gaps have been
> the main focus
> >for years and is the majority of the lists
> experience with static
> >gaps. I guess mainly because of cost and easy
> access to copper
> >tubing. Mass is certainly helpful for heat
> dissipation and is even
> >typical for stationary electrodes on rotary gaps.
> The principal
> >applies, however, air is still required in either
> case and
> >definitely required for higher current gaps.
> >
> >Take care,
> >Bart
> >
> >Tesla list wrote:
> >
> >>Original poster: Timjroche@xxxxxxx
> >>I'm running:
> >>12kV 120mA NST
> >>.03 uF 45kV maxwell tank cap
> >>12 T .25" tube .25" spacing primary
> >>4.343" OD 28awg 17" lng secondary
> >>maj. dia 17" min dia 4" toriod
> >>
> >>What is the best place to start a static gap?  I
> have . 5" solid Cu
> >>(12 pcs. 4" long), .5" tube, 7/8" tube, and 1.125"
> tube...is hollow
> >>better? bigger dia?
> >>What about length? my 7/8" (6 pcs. 6" long) better
> than .5" 3"long?
> >>can you have to many gaps? i.e. total gap=.5",  2
> tubes?, 6 tubes?, 12 tubes?
> >>
> >>thanxs
> >>Tim
> >>
> >>
> >>
> >>