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28 Mar 2021 [16:46]
It's interesting to see how cavity temperatures are re-equilibrating [link]
28 Mar 2021 [13:30]
top-up wind. Note that with the opened up weight chute the clock will run for longer Next winding can be on Monday morning 5 March.
28 Mar 2021 [13:29]
Reset last_drift
28 Mar 2021 [12:56]
Did an experiment moving the regulation weights [link] noted that twist increases as the weights are moved towards Great Court (South). It's best to have as much weight to the North as possible. I guess this is because of the new temperature compensator. I wonder if there's a way to put it further North? There is defintely more twist [link]
28 Mar 2021 [12:50]
ADJUST: +9850 ms/day to 33200
28 Mar 2021 [12:36]
The clock is running very fast (gaining 158 seconds per day [link]) so I unscrewed the regulation nut by 3.5 turns (to +10s/day), and then by a further turn to 4.5 turns (to -32s/day). In Nov 2010 we reckoned on 40sec/day per turn. It looks more like 42 s/day per turn/
28 Mar 2021 [11:55]
Restarted the clock and restarted pibackup-clock, pi-clock5 and pi-clock10 (these were shut down for the duration of these antics). Also had to realign the twist prism which had got knocked
28 Mar 2021 [11:53]
Reinstalled the barometric compensator which has a new feature - a temperature fine-tuning compensator designed by Joel Williams 4th-year MEng student. The compensator has a radiator TRV with a weight suspended off it. To bein with we havd a 24g knurled nut and a 96g lead weight held on with a magnet. Let's see what happens!
28 Mar 2021 [11:36]
Reinstalled the pendulum, refitting the regulation weights platform, IR sensor shim, tilt leter, bubbles
28 Mar 2021 [07:41]
After cleaning everything out it all looks to run quite smoothly. The insert at the bottom looks to be the right way around because the tapered pin goes through the slot exactly in the centre.
28 Mar 2021 [07:40]
Weighed the various bits - centre rod 2.6kg (diameter 14.55mm), Zinc 4kg, outer steel 4.5kg
28 Mar 2021 [07:38]
Took the pendulum upstairs and dismantled it. Noted that about half a teaspoon of fine grit and a bit of sawdust came out. I wonder if this has jammed up the temperature compensation? Where did it come from? Possibly through the holes in the side of the outer tube from when we hacked open the pendulum space 17 March 2013
28 Mar 2021 [07:36]
Removed the pendulum by jacking it up using the long steel lever and some weights. Tapped out the tapered pin from the suspension and removed the suspension. Lowered the pendulum down onto a neat wedgde support arrangement that Mark Rainer had made for the last time we removed the pendulum (27 Nov 2010). Undid the regulation nut and manouevred the pendulum rod out down through C6 Great Court.
28 Mar 2021 [07:35]
Removed the regulation weights and their platform, the IR sensor shim, the Wyler tilt meter and the two tilt bubbles in readiness for removing the pendulum
28 Mar 2021 [07:33]
Measured the period of N-S swinging of the pendulum which is 30 swings in 68 seconds, ie 2.3 seconds. The amplitude of swing was about +/-2mm at the bob, ie +/-1mrad. Damping for this motion was high, about 4 swings to 1/e so zeta=1/8pi = 0.04
28 Mar 2021 [07:31]
I checked that the pendulum was running clear at the top of the perspex case, which it was (wondering if this might have been contributing to curious step changes in twirst phase)
28 Mar 2021 [07:30]
advancing the clock for Summer Time - should have been a 5-minute job, but I decided to mess about a bit

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Contact:, Trinity College, Cambridge