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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