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

[Dana Whitlow]

It seems to me that in order to derive much thermal stabilization, the *top*
of the space would need to be several feet underground (depending on
geographic location).  And I think that the means for human access would
likely "spoil the broth" unless fairly extreme measures were taken.

Wouldn't it be sufficient to use a space whose thermal coupling were weak
enough to make the time constant a few days (instead of months)?  Then,
ordinary inexpensive means like GPS-locked Rb standards with suitable
(longish) time constants should clean up "GPS noise", yet enable the loop
to take care of low rate temperature variations in the protected space due
to outside temperature changes.

Remember, perfection in clocks is expensive- according to recent things I've
read about entropy of timekeeping, a perfect clock would require infinite
power,
and that alone would blow away all one's efforts at temperature control.

Dana


On Thu, Sep 9, 2021 at 6:19 AM B Riches via time-nuts <
time-nuts at lists.febo.com> wrote:

>  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 <
> wbeam at gci.net> 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 (tvb at leapsecond.com).
>
> >>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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