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

[Bob Bownes]

Temperature stability will vary with climate. Here in upstate NY, you’ll need to get to >50” of depth to start to get any real year round thermal stability. But a local civil engineer should know that number well. We also have to worry about water intrusion, even with concrete, depending on depth. 

Interesting subject. 



> On Sep 8, 2021, at 22:09, djl <djl at montana.com> wrote:
> 
> 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 (tvb at leapsecond.com).
>> Thanks,
>> /tvb
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> 
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> Dr. Don Latham  AJ7LL
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