I think you can use precast concrete such as a septic tank or rings. My
measurements made a LONG time ago in NM indicate that a mere 18 inches
depth leads to less than one degree (God's units as revealed by the
French) over the period of a year. Bring wiring in via a trench at the
surface level of the top of the vault. Ideally, the cover should be
insulation to near surface, then soil. That's the one sticky point
because as you will know, thermal vortices will be set up in the vault
air. very small slow fans may control? The flow can be modeled, I
think.
Don
On 2021-09-08 19:54, 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 (t...@leapsecond.com).
Thanks,
/tvb
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------------
The whole world is a straight man.
----------------------
Dr. Don Latham AJ7LL
PO Box 404, Frenchtown, MT, 59834
VOX: 406-626-4304
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