[time-nuts] Antique pendulum clocks

[Philip Gladstone]

I've started to monitor the individual ticks on a grandfather clock from
the 1790s. Essentially I timestamp whenever the pendulum breaks/restores a
light beam.

The data that I get is surprising in that the pendulum swing varies
according to the position of the hands on the clock. It appears that the
amplitude of the swing depends on the driving force imparted by the
escapement. Since the second hand is not counterweighted, there is slightly
more energy available to drive the escapement during the first half of each
minute and slightly less in the second half. There is much bigger effect at
the end of each hour when the mechanism has to move a lever to trigger the
strike mechanism. This 'end of hour' effect changes the pendulum swing
enough so that the period is noticeably affected (maybe by 300ppm)

Anyway, my google-fu did not reveal anybody else interested in this
stuff... Anybody here interested?

Philip