How about using a round septic tank. Mine is about 5 feet wide and 6 feet
deep Large hole in the top - put ladder for entry.
73,
Bill, WA2DVUCape May, NJ
On Thursday, September 9, 2021, 02:29:40 AM EDT, Bill Beam <[email protected]>
wrote:
On Wed, 08 Sep 2021 18:36:11 -0800, Bill Beam wrote:
>On Wed, 8 Sep 2021 18:54:03 -0700, Tom Van Baak wrote:
>>I am considering a below ground "clock room" away from the house. This
>>will be for some low-drift quartz oscillators and also a couple of
>>precision pendulum clocks. The goal is long-term, unattended, and very
>>undisturbed operation.
>>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.
>>If any of you have personal or professional experience with the design
>>or construction of this sort of thing, especially experience with
>>precast (utility) vaults or poured concrete, please let me know.
>>In case this gets too off-topic for time-nuts, off-list email to me is
>>fine ([email protected]).
>>Thanks,
>>/tvb
>Tom,
>How long do you expect your proposed voult to go undisturbed?
>I have several pendulum clocks. They are disturbed every couple of months
>by earth quakes. By disturbed, I mean pendulum banging against the case
>walls....
>Any ground motion that can be felt will upset the clocks. Often the clocks
>will
>signal an earth quake that is not felt.
>Good luck.
I spent a few years as a geotechnic/soils engineer and learned as others have
pointed out
that a thermal wave of period one year and wave length of several meters
propagates
downward thru the soil. Peak amplitude of a few degrees can be expected near
the surface.
Consider building an "oven" with the clock vault freely floating in a water-ice
mixture. This will
provide constant temperature (0C) and limited mechanical isolation from earth
quakes.
But of course this will be expensive to operate.
As you know 'good' clocks require a lot of energy and generate a lot of entropy.
Protecting the quartz oscillators is much easier than protecting the pendulum
clocks.
Bill Beam
NL7F
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