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

[Bill S]

Tom
When I added a machine shop to my home I devoted a part of it to set up 
and run a number of precision clocks which at the time consisted of a 
Fedchenko, two Shortt clocks and a tank Riefler. Of course the room was 
above ground and all of the problems regarding temperature and vibration 
had to be considered. The concrete floor of the room was particularly 
deep and I had arranged to have two large square holes made (when the 
floor was poured) in the floor into which I mounted two 3000 pound 
square freestanding concrete blocks that were floor height. The blocks 
were mounted on vibration isolators (used to mitigate the effects of 
earthquakes in California buildiings) which I had made. Although it 
wasn't perfect it did help with the local road noise and random 
vibrations. What I hadn’t counted on was the change of seasons and heavy 
rain. When I set up the clocks (Fedchenko on one of the isolation blocks 
and an Englsh Shortt on the other) I mounted a very sensitive tiltmeter 
on the floor of the room and found that when we had a long duration 
rainfall in the summer, the entire floor tilted slightly. It did the 
same when the seasons changed from Winter to Summer. Keeping a steady 
temperature also proved to be difficult. The tiltmeter was of the type 
used on bridges to check for beam flexing and was made by Sperry. My 
house was built in the 50's and I believe a good deal of fill was used 
to level the site. This most likely caused the problem. Neverthess I had 
quite good results with the clocks.

Bill S
www.precisionclocks.com




On 9/8/2021 9:54 PM, 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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