Interesting plots

Good control

The clock ran from 30 August 2009 to 22 November 2009 less than 1 second adrift. There is an unavoidable glitch due to the clock change in October. Then along came a period of sustained low barometric pressure ...

Drift vs Pressure, 30 August 2009 to 30 November 2009

Time changes in March and October

An opportunity to see how the pendulum amplitude decays when undriven:

The time change, 29 March 2009 — Drift and Amplitude. This shows a free decay of the pendulum for a few minutes as the escapement is released to allow the hands to advance by one hour.
The time change, 26 October 2008 — Drift and Amplitude. This shows free decay of pendulum amplitude over a whole hour (the clock has to be stopped to allow the extra hour). Note also that the GPS time goes back by one hour at 2am.
The time change, 26 October 2008 — Going vs Amplitude. An opportunity to see how the going varies with amplitude over a large range of amplitude (the clock was stopped for an hour).

Illustrations of pendulum physics

Drift vs Temperature. Illustrates effect of thermal expansion of pendulum. The compenstion works in steady state, but theory suggests that a steady rise in temperature will cause a steady fall in drift. See the Theory page. (perhaps!)
Going vs amplitude — Here, for some reason (a spider?), the pendulum amplitude dropped dramatically and the Going increased exactly in accordance with theory.
Amplitude vs Air density — Amplitude reduces and air density increases - exactly as predicted by the conventional form drag laws.

Pigeon glitches

These annoying events have been increasing in frequency. Pretty sure it's pigeons standing on the minute hand. Click on the Pigeons link in the menu.

Another glitch, 1 Oct 2009, tiny drop in pendulum amplitude.
Clock stopped mysteriously for 3 seconds, 28 Sept 2009. The clock free-wheeled, causing a tiny drop in pendulum amplitude.
Clock stopped mysteriously for 9 seconds, 27 Sept 2009. The clock free-wheeled for about 9 seconds. This caused a drop in pendulum amplitude, but it regained composure straight away.
Clock stopped mysteriously for 90 seconds, 25 Sept 2009
Clock stopped mysteriously for 3 minutes, 17 Sept 2009

Mysterious unexplained glitches

Sudden slowing of the clock, with no apparent cause, corrects itself after 12 hours. Perhaps something to do with air currents up the pendulum chamber?
Going — amplitude. Here, for some reason (a spider?), the pendulum amplitude dropped dramatically and the Going increased exactly in accordance with theory