[time-nuts] Re: in-ground clock room

[Ben Bradley]

I've seen discussion of making a seismic vault (though not sure if
they used that name, making it harder to find in the haystack of
posts) on this mailing list, maybt 15 or 20 years ago, so nut sure if
this is helpful:
https://www.seismicnet.com/maillist.html

For possible immunity from earthquakes, LIGO uses some quite complex
control and feedback systems to hang its mirrors so that mild
earthquakes and local noise won't affect them. From what I've seen
over the years a lot of this info has been published, but I imagine it
would be quite expensive to reproduce. Maybe some sort of Ligo Lite
system would be feasible.

On Thu, Sep 9, 2021 at 10:13 AM Brent <brent.evers at gmail.com> wrote:
>
> Seismic vaults are built similar to your requirements.  I suggest looking
> up the Earthscope program - there should be info out on the web as to how
> their vaults were designed, but in a nutshell, dig a hole, put some gravel
> in the bottom, place a large culvert on end in the hole, pour a few inches
> of concrete in the culvert, put instrumentation in a pedestal inside, run
> power and comms, put a bilge pump and outflow pipe in it on the floor
> (below pedastal), and put a cap on the whole thing.  Those were then
> re-buried, but that prevents easy access (although it probably improves
> temperature stability). A septic tank would be larger, but more effort, and
> may expose more surface area to the sun (temp variation).
>
> I've been in various seismic vaults and they can vary from very extravagant
> to downright crude.
>
>
>
> On Thu, Sep 9, 2021 at 9:04 AM Bob kb8tq <kb8tq at n1k.org> wrote:
>
> > Hi
> >
> > You could do some research on the climate in various parts of the world.
> > Pick the ideal location and move there :) :) You also could optimize the
> > location for various tidal forces ….
> >
> > How deep can you go on your property before you run into something
> > massive? Around here, I can go down between a foot and maybe two
> > feet. At that point it’s time for dynamite. You do not ask “how much to
> > put in a swimming pool?” in this neighborhood.  Part of this is the
> > geology,
> > part is how the builder graded things to  put in the subdivision.
> >
> > While that *sounds* ideal, the shale is tilted due to some thing running
> > into
> > something else a while ago. The net result is ground water running here
> > and there to some fairly significant depths. As the seasons change that
> > ground water and its somewhat random route changes isn’t ideal for
> > temperature stability.
> >
> > Yes, it’s all about some *very* local aspects of your geology.  With some
> > care, I could move a few miles in one direction or another and be in a
> > *very*
> > different situation. (again thanks to just how this ran into that ….).
> >
> > Since temperature stability is only part of the design and mechanical
> > stability is the other. This location might work ok for half of the design
> > goals …. Granite likely would do better than fractured shale though ...
> >
> > Bob
> >
> > > On Sep 9, 2021, at 1:20 AM, Poul-Henning Kamp <phk at phk.freebsd.dk>
> > wrote:
> > >
> > > --------
> > > Tom Van Baak writes:
> > >
> > >> For scale, assume the room is 1 meter × 1 meter × 2 meters deep. So
> > >> that's vastly smaller than digging a basement, but much larger than
> > >> drilling a 8 inch round pipe. Digging down gives some natural isolation
> > >> and temperature regulation. A couple tons of concrete gives high
> > >> stability vertical walls for the pendulum clocks.
> > >
> > > I researched this extensively before we built a house 5 years ago.
> > >
> > > Look at the plot on page 37 in this paper:
> > >
> > >
> > https://www.researchgate.net/publication/279526204_Temperatur_og_temperaturgradienter_ved_og_under_jordoverfladen_i_relation_til_lithologi
> > >
> > > It shows that in Denmark the yearly temperature variations in
> > > penetrates to a depth of 15 meters, and that even at 10 meters
> > > depth, you can expect the swing to be several Kelvin in any year.
> > >
> > > I did find handwaving which said tree-cover reduced the swing by
> > > "a lot" but no measurements to substantiate it.
> > >
> > > In the end I concluded that I could do better in the comfort of my lab.
> > >
> > > You should try to find similar data for your local climate and
> > > geology, before you pour too much money into a hole in the ground.
> > >
> > > --
> > > Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
> > > phk at FreeBSD.ORG         | TCP/IP since RFC 956
> > > FreeBSD committer       | BSD since 4.3-tahoe
> > > Never attribute to malice what can adequately be explained by
> > incompetence.
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