[time-nuts] Time and tide - pendulum clocks and gravity tides

[Tom Van Baak]

Hi Geoff,

Thanks for posting the link. Also nice that the PDF is open access. [1]

Besides a large collection of quartz and atomic clocks some of you know 
that I also play with pendulum clocks. Duncan Agnew's paper is really 
good and I was very happy that someone with his reputation and 
background would spend time to write such a scholarly paper about 
pendulum clocks, specifically about performance and perturbations. The 
world of precision timing has, of course, long since moved from 
mechanical clocks to electronic quartz, atomic, and now optical clocks. 
Yet, some of us are still really fascinated with pendulum clocks. [2]

We know from thousands of postings here that frequency standards are 
somewhat affected by temperature, and often also by pressure, humidity, 
air flow, voltage, tilt (static acceleration), vibration (dynamic 
acceleration), output load, age, and even by velocity & elevation 
(relativistic effects).

So part of the fun of this time nut hobby is to focus on the sources of 
instability and try to measure them. I can't think of another hobby 
where something works 99.999999999% perfectly but we totally ignore that 
and instead worry or delight about the 0.000000001% imperfection still 
left. Some would call it a disease...

Anyway, the world of precision timing with pendulum clocks is similar, 
but being large objects there are even more weird effects at work, all 
of which conspire to degrade performance over time. Geoff -- earthquakes 
for example. [4] One of the most subtle effects of all is the effect of 
the moon (and sun) on a pendulum clocks. Yes, the "phase of the moon" 
really does apply. Ok, it's minor and only a few pendulum clocks ever 
built are good enough to detect this, but that's part of the allure. 
Some pendulum clock & tides background reading here:

http://leapsecond.com/hsn2006/

/tvb

[1] https://hgss.copernicus.org/articles/11/215/2020/hgss-11-215-2020.pdf

[2] http://www.hsn161.com/HSN/newsletter.html

[3] pendulum-nuts [contact me off-list]

[4] http://leapsecond.com/pend/synchronome/quake.htm


On 10/19/2020 3:51 AM, Kiwi Geoff wrote:
> Note sure if this has been raised here before, but a new paper by
> Duncan Agnew is available.
>
> "Time and tide: pendulum clocks and gravity tides"
>
> https://hgss.copernicus.org/articles/11/215/2020/
>
> It thanks TVB in the "Acknowledgements", so hopefully it is safe to
> mention it here.
>
> I enjoyed reading it.
>
> On a personal note, it "sort of" ties in with a project I am currently
> playing with (clocks and ocean tides) where I have written a new
> algorithm to improve the accuracy of setting a conventional Tide
> Clock.
>
> Whilst doing this, I wondered whether I could change my 100 year old
> family heirloom Ansonia Kitchen clock, to run (at a more leisurely
> rate in its retirement) as a Tide Clock, by increasing the pendulum
> period by:
>
> ---------------------------------------------------------------------------------------------
> M2 constituent of the Harmonic Tide
>
> Speed = 28.984104 (degrees per hour)
> Period = 360 / Speed = 12 Hours 25 Minutes 14.165 Seconds
> Increase Pendulum Period by 12:25:14.165 / 12:00:00 = 1.035050
> ---------------------------------------------------------------------------------------------
>
> There is only 1mm of thread left on the pendulum shaft, but I was very
> pleased to be able to regulate it to within the thermal limitations of
> a steel pendulum rod !
>
> Not exactly approaching "Time Nuts" precision though !
>
> Regards,
> Geoff Hitchcox
> Christchurch, New Zealand.
>