Comments (edit)

(click on a date to see the data to which the comment refers)

DateCorrectionComment
02 May 2012 [17:00:00]+0ADJUST: +200ms/day to 32900 thanks to Mark Rainer for this, and for winding  
26 Apr 2012 [23:00:00]+0ADJUST: +200ms/day to 32700  
24 Apr 2012 [16:00:00]+0ADJUST: -500ms/day to 32500 Thanks to Ted Popper and Annie Kingsbury (Popper) for help with a top-up wind.  
22 Apr 2012 [11:30:00]+0Anyone noticing a glitch here - well, I was demonstrating the effect of adding a 1s/day weight.  
22 Apr 2012 [11:00:00]+0Rather a large delegation today - Jeremy Fairbank and his co-lunchers, plus Philip Hardie and his guests. Clock now wound. We seem to be on a Sunday routine. Back to Tuesdays this week, I think.  
20 Apr 2012 [16:00:00]+0Great to have Joe and Betty Davidson visiting - and topping up the heavy quarters weight - less to do next time!  
19 Apr 2012 [15:30:00]+0The system is up and running again - not exactly in the best way. We have resurrected the old PC and will now try to repair the new one. At least data is streaming again now. many thanks to Rick Lupton for his help today.  
15 Apr 2012 [12:00:00]+0ADJUST: -100ms/day to 33000, winding with help from Simon Wallfisch, Sandy Hunt and Jonathan Hunt  
12 Apr 2012 [10:28:41]+0Guys, would you like to come into the IT Department for a chat. We are not an experts in this field, but we might be able to help (we have friends). We are in Bishops Hostel staircase D.  
08 Apr 2012 [19:59:54]+0Apologies that the data logging system is still down. Anson and Tim have a solution in hand - it just requires the right few hours to do it. Many thanks, you two. Meanwhile the clock is still fine - it is about 1.2 seconds fast.  
01 Apr 2012 [16:07:25]+0ADJUST: -100ms/day to 33100 and very kindly helped with winding by Juliet Babinsky, Carolyn Babinsky, Holger Babinsky, Giovanni Pellegrini and Ruth Pellegrini all of whom are stronger than they thought!  
01 Apr 2012 [06:30:58]+0So where are we: Tim has now also spent a lot of time on this. He says: The short story is that the National Instruments drivers are not working with the new kernel version after the upgrade. The longer story: the drivers check the kernel version by looking at its second digit. With the recent change in numbering, from 2.6.whatever to 3.n1.n2 (without actually a massive leap in the code) this is not particularly helpful. Anecdotal reports on the internet suggested the drivers should still work if these checks were removed. After a bit of work to disable them in the installation scripts, it almost installed. A change to the way locking is handled (linked to removal of the [Big Kernel Lock ], so I understand!) meant that a small change to the ioctl code was needed (which I did not really understand; it looked like an old callback is no longer allowed, and needed removing). Finally, everything compiled and the nikal kernel module loaded (with a memory allocation error in dmesg, but at least it appears to lsmod). Unfortunately, clocklogger then returns [libnipalu.so failed to initialize - Perhaps you need to run updateNIDrivers - Aborted ] So it looks like NI need to update their drivers. In the meantime, I am running out of ideas short of using an old kernel again (which would be annoying!).  
01 Apr 2012 [06:30:57]+0Anson has checked the disks - here is what he says: there were so corrupted inodes that come up as part of the e2fsck run in the root partition. The home directories seemed fine. There is no way of recovering easily the problems because I cannot see how the inodes correspond to actual files. So, I am going to upgrade the operating system tonight to either 11.4 or 12.1. This is a wise thing to do anyway given what we were using before 11.3 is out of support - and the original lost files harder to find.  
25 Mar 2012 [14:18:59]+0Ah. Apparently there was a huge power surge on 20 March at 01h30 - the same time as the PC crash. There is clearly some work to do here....  
25 Mar 2012 [13:45:00]+0Sorry, I have been away from Cambridge and have not had time to fix the problem. I think it is a NiDAQ driver problem because the output file says [DAQ Error]. Not very helpful! Tim, any ideas?  
25 Mar 2012 [13:00:00]+0winding help from Anna Gatti, Nico Gatti, Sofia Gatti, Alessandra Tosi, Rupert Gatti, Valentina Corsetti, Christopher Peacock and Dilan Mehmet - a really very helpful team!  
25 Mar 2012 [07:05:00]+0Clock advanced for summer time  
20 Mar 2012 [17:00:00]+0ADJUST: -100ms/day to 33200 - maybe it has a mind of its own!  
20 Mar 2012 [01:30:00]+0Computer crash - under investigation  
13 Mar 2012 [14:00:00]+0ADJUST: +100ms/day to 33300 - thanks Mark.  
09 Mar 2012 [18:15:00]+0ADJUST: +2000ms/day to 33200 Tim very helpfully went back to regulate - by a huge 2s/day. Hmm, what has changed?  
08 Mar 2012 [20:45:00]+0Tim gale very helpfully went to find out what was happening - found things in a bit of a mess, the cable had been pulled out of the weather station and had to be refitted. This meant stopping the pendulum (the weather station is down the pendulum chamber). Restart, hopefully it will settle down quickly. Teally not sure what caused all this - I suspect the Works Department had to move the computer to gain access to a cupboard, and I think they pulled out the USB cables, then put them back in again..  
07 Mar 2012 [11:15:00]+0Something happened here.  
03 Mar 2012 [15:00:00]+0ADJUST: +100ms/day to 31200  
28 Feb 2012 [12:16:40]+0ADJUST: -200ms/day to 31100 because I want to have the clock back at 0 for the clock change in March  
28 Feb 2012 [12:15:00]+0Great to have help from Sally Pettipher who is on a fitness drive for her coxing.  
21 Feb 2012 [22:10:00]+0Rosemary Richards and Jeremy James from Grantham GravityFields Festival helped with winding today - they now know what gravity is!  
21 Feb 2012 [21:50:00]+0poor PC has not had a rest since Occober 2011, needed a restart.  
07 Feb 2012 [15:09:14]+0A whole heap of helpers today ... Harry Clift, Eloise Hunt, Lynn Clift, Janet Procter - all very muscley!  
31 Jan 2012 [13:17:33]+0Jonas Coene helped with winding - thanks!  
24 Jan 2012 [13:13:50]+0Many thanks to Simon Raikes for throwing his weight around today!  
17 Jan 2012 [12:06:07]+0Winding helpers today: Madelaine Crush, Janice Chambers and Rob Hogan - many thanks!  
10 Jan 2012 [19:00:00]+0Not sure what caused this gap in data. The PC seems to be fine because weather data has been collected. Perhaps the GPS receiver was doing a software upgrade?  
10 Jan 2012 [16:58:46]+0Thanks Janar Davletov (from the Bursary) for help with winding!  
04 Jan 2012 [04:31:40]+0Barometric compensator: Why does the compensator appear to be working for rapid changes in pressure (ie over a few hours) eg [link] [link] but not for slow changes in pressure (over a few days) eg [link] [link] A real mystery. Perhaps there is a link between pressure and temperature, or maybe updraughts?  
03 Jan 2012 [17:25:00]+0Thanks to Alexander Hunt for helping with a wind - just in time!  
27 Dec 2011 [13:00:00]+0Winding excellently assisted by Giovanni Pellegrini, Isabella Pellegrini, Luca Pellegrini and Eloise Hunt  
29 Nov 2011 [18:00:00]+0ADJUST: +50ms/day to 31300 and a wind, thanks to John Fisher Burns, Andrew Testa and Benjamin Barrett for saving my efforts.  
13 Nov 2011 [15:30:00]+0top up winding - thanks to Bianca Sporea and Devon Griffiths for trying their arms!  
30 Oct 2011 [00:30:00]+0... thanks to Anson Cheung and friends Michael Koehl, Jean Ho, Charles Roddie, Claire Sladden, Nicholas Teh, Olivia Skilbeck, Kate Pfeffer, Marco Selvi, Susan Raich, Matthew Willetts and Lydia Reeves for staying up so late... must have been a chore!  
29 Oct 2011 [23:30:00]+0clock change for end of Summer Time.  
25 Oct 2011 [13:15:00]+0ADJUST: +100ms/day to 31250, thanks to Anson Cheung for company, and for agreeing to effect the clock change this coming weekend.  
10 Oct 2011 [21:30:00]+0ADJUST: -150ms/day to 31150, observed by Hermann Hauser and Peter Davidson - both of whom seem to understand at least a little physics.  
01 Oct 2011 [14:30:00]+0I put a sunshield in the left part of the window so the pendulum is in full shade at all times - note the dip is no longer occurring,  
30 Sep 2011 [14:30:00]+0These dips in going are due to the sun shining on the top quarter of the pendulum. The outer steel expands rapidly, the inner zinc stays cool and does not compensate. Once the sun passes then the going returns to normal.  
29 Sep 2011 [14:30:00]+0see above, Re: dips  
28 Sep 2011 [14:30:00]+0see above, Re: dips  
27 Sep 2011 [14:30:00]+0see above, Re: dips  
25 Sep 2011 [16:45:00]+0ADJUST: +150ms/day to 31300, thanks to Christine Costello and Hugh Costello who managed not to drop any weights down the shaft.  
18 Sep 2011 [13:30:00]+0ADJUST: +150ms/day to 31150, thanks to Howard Tuck for his company, and to help with a bit of winding.  
26 Aug 2011 [14:10:00]+0ADJUST: +150ms/day to 31000, thanks Mark Rainer. Perhaps the right setting is somewhere in the middle...  
11 Aug 2011 [08:00:00]+0ADJUST: -150ms/day to 30850 - Hilary undoing her what she did 2 weeks ago. I think this is about the right setting, on average.  
03 Aug 2011 [18:30:00]+0a HUGE downpour occurred at about this time - the sky was like the sea. The GPS receiver (which already can only see half the sky from its view out the window) lost sight of satellites for a few minutes, hence our temporary loss of data.  
02 Aug 2011 [13:00:00]+0thanks to David Hughes for help with winding...  
30 Jul 2011 [17:00:00]+0The webcam is now working again, and it even has sound! Thanks very much to Tim Gale.  
26 Jul 2011 [13:30:00]+0ADJUST: +150ms/day to 31000 - thanks Hilary.  
20 Jul 2011 [12:00:00]+0Today we installed a new PC - hopefully now capable of running the webcam properly (watch this space). It runs OpenSUSE (Linux) so many thanks in particular to Tim Gale for getting the installation all working, in particular the NI-DAQ card and drivers. Impressive that we only dropped a few minutes of data. Well done Tim! Thanks also to Anson Cheung for all his support and advice. We still need to get the cron job running for automatic upload to the website. In the meantime uploads will be manual and a bit sporadic.  
19 Jul 2011 [14:57:00]+0Many thanks to Sian Gardner for volunteering for a workout!  
12 Jul 2011 [12:00:00]+0Many thanks to Lucy Leckey, Richard Leckey, Peter Dennis and Sue Dennis for winding!  
10 Jul 2011 [13:50:00]+0Corrected clock that was 6 seconds fast - as displayed by the hands, ie hands ahead of the mechanism - no obvious explanation. Pigeons at quarter past now? I hope not! Great to see David Greagg - now he knows the difference between a clock and a chronophage pretending to be a clock ...  
28 Jun 2011 [21:50:00]+0bumped the pendulum while removing the plastic pipe from the pendulum chute (installed 19 Jan 2011) - not sure it is doing anything, and it looks ugly...  
26 Jun 2011 [13:00:00]+0ADJUST: +50 ms/day to 30850 (thanks Ellie)  
14 Jun 2011 [18:50:00]+0ADJUST: +200ms/day to 30800 and wound with help from Alek Haigh, Maya Haigh, Ellie Hunt, Anna Harrison, James Dixon, Esra Haigh, Stuart Haigh  
09 Jun 2011 [11:10:00]+0experiment with removing then adding 5000ms/day (to show Simon and Henrietta!)  
02 Jun 2011 [11:24:00]+0ADJUST: -150ms/day to 30600 - with the help of James Grime who is filming all of this for his youtube channel youtube.com/singingbanana  
24 May 2011 [17:00:00]+0ADJUST: -150ms/day to 30750, and help with winding from Andreas Michaelides and Srikanth Madabhushi  
18 May 2011 [20:50:00]+0SPICE visit: Chris Burgoyne, Hilary Costello, Tony Cox, Peter Davidson, Simon Driscoll, Pru Foster, Don Grainger, Jim Haywood, Hugh Hunt, James McGregor, Thao Do, Daniel Peters, Francis Pope, Chris Walton, Peter Braesicke, Alessio Bozzo, Matt Watson, Andy Elson, Emily Knott, Markus Kalberer - a good (and challenging) day had by all!  
13 May 2011 [15:03:00]+0small disturbance due to replacing the 2000+1000+1000+500+500 ms weights with a single 5000ms/day weight - witnessed by Geoff and Wendy Newton from Perth WA, and their daughter Kirsty Kuo. Not wanting to miss an opportuinity, I got them to do some winding!  
08 May 2011 [16:30:00]+0Visit by the AHS American Chapter, thanks to Hilary Costello for hosting. Note the glitch - visitors always cause disturbance, even horologists!  
01 May 2011 [18:15:00]+0ADJUST: -250ms/day to 30900 (dropped 200ms/day down the pendulum chute ... bound to happen one day)  
30 Apr 2011 [18:15:00]+0Barometric compensator seems to have worked pretty well recently [link] [link] as has the temperature compensation [link] [link] . There is a lot noise on these plots, pretty sure this is due to temperature gradients in the clock chamber because it seems to be worse when the sun is shining strongly through the windows and when the central heating is at its hottest in the room below.  
19 Apr 2011 [11:15:00]+0ADJUST: +100ms/day to 31150, thanks again Hilary. I have a far-fetched idea that going is proportional to long-term rate-of-change of temperature at -200ms/day per degC/day. This minor adjustment should help test it.  
16 Apr 2011 [13:00:00]+0Computer restarted after power cut, thanks again to Anson Cheung  
16 Apr 2011 [07:00:00]+0Power cut, safe shut down thanks to Anson Cheung  
12 Apr 2011 [19:30:00]+0ADJUST: +300ms/day to 31050, thanks to Hilary Costello. I am viewing all this from a distance (Australia) and continue to be mystified at the cause of the change in drift that occurred around 5 April - is it due to rate of warming? Spring seems to have sprung around then.  
07 Apr 2011 [07:45:00]+0Power cut - thanks to Anson Cheung and Tim Gale for seeing to the restart.  
26 Mar 2011 [22:30:00]+0Advanced clock for summer time (effected by Mark Rainer and Graham {clocky} Newman). The 30ms shift in drift is due to the removal of the mass of the gravity arms from the pendulum - same effect as removing mass from the regulation tray causes the clock to run slower. For about 3 minutes it ran about 4s/day slow. Note also the 1.2mrad drop in pendulum amplitude and the recovery afterwards.  
25 Mar 2011 [13:50:00]+0ADJUST: -150ms/day to 30750, may be better. Witnessed by Rebecca Loving on the eve of her departure to Chicago.  
21 Mar 2011 [06:40:00]+0ADJUST: +400 ms/day to 30900, back to where it was on 29 Jan.  
11 Mar 2011 [05:46:00]+0Power outage (planned) complete coincdence that this is the exact time at which the Japan earthquake struck. It would have been interesting to see if the effect could be seen on the going/amplitude of the clock.  
06 Mar 2011 [11:01:00]+0So what effect is the sunshine having? The top 10% of the pendulum does not have zinc compensation in it so if it were sun-on-the-pendulum effect then sun should mean a lengthening of the pendulum and so the clock slowing down. But completely the opposite happens - the clock suddenly speeds up. It is the reverse of what we have seen ober the winter caused by central heating in the room below. There must be something to do with the clock chamber (which is enclosed) now being warmer than the room below, causing a reversal of the temperature gradient over the length of the pendulum.  
06 Mar 2011 [11:00:00]+0These kinks seem to be related to sunshine. Going was steadily downwards throughout a period of cloudy days, with occasional upward bursts wne the sun comes out. Now that other things seem to be under control (ok, now asking for trouble) the effect of sun is more obvious. There is a large window (south facing) that makes up some 30% of the surface area of the south side of the clock case, and in the afternoon the sun shines on the clock mechanism (including the top 10% of the pendulum rod --- see next comment). The window has secondary double glazing with UV film.  
26 Feb 2011 [20:00:00]+0nothing to report - just enjoying 2 weeks during which the clock has lost only 0.5 seconds. Not sure why the recent slowing down - temperature compensation is ok [link] , still not certain about the barocompensator [link] but there is a lot of noise on the plot. The biggest effect at the moment is draughts, I think, caused by differential temperature with the centrally-heated room below. As spring settles in we should see less of this.  
08 Feb 2011 [21:23:00]+0ADJUST: -250 ms/day to 30500. Reinstated the amplitude measurement plank at the top of the pendulum chamber. This might moderate the extremes of air flow that could be responsible for the observed fluctuations of going.  
01 Feb 2011 [10:00:00]+0clock restarted. Advanced by 4h15m - the longest pigeon event on record.  
01 Feb 2011 [09:00:00]+0With the help of a cherry picker I overcame my fear of heights and fitted a thin wire to the minute hand. This should, with any luck, prevent pigeons from settling on the hand. We will see.  
01 Feb 2011 [05:45:00]+0pigeons. This time they sat on the minute hand for such a length of time that they stopped the clock completely.  
31 Jan 2011 [14:45:00]+0pigeon correction +18 seconds  
31 Jan 2011 [07:45:00]+0yet another pigeon. I said I was serious. Now even more serious. Pigeons, beware.  
30 Jan 2011 [16:58:00]+0pigeon event correction, +24 seconds. Thanks to Andrew Kennedy for the company!  
30 Jan 2011 [12:45:00]+0another pigeon. I am seriously going to do something about this now.  
29 Jan 2011 [21:50:00]+0ADJUST: -150 ms/day to 30750 ... fine tuning. What better thing to be doing on a Saturday night!  
29 Jan 2011 [16:50:00]+0ADJUST: +1100 ms/day to 30900 This change is needed because of the opening up of the pendulum chamber earlier today. Colder air is now drifting down to the base of the pendulum and this is where most of the temperature-compensating zinc is. It contracts on cooling, so lengthening the pendulum (that is how it works). So the clock has slowed down. Really by an astonishing amount. I suspect the air at the base of the pendulum chamber must have been really warm due to the central heating below, set at 22C The pendulum case sits high up in the room so it may well be up in the high 20s C. The temperature up in the clock room is around 6C today. Let us see how it settles down, but I think this will be a new operating regime. I wonder if the amplitude will do anything different now that air currents will be altered?  
29 Jan 2011 [13:05:00]+0For the record, since I moved the weather station here are links to glitches that show the differential temperature effect have been happening often: [link] [link] [link] [link] [link] [link] [link] [link] . They all point to a differential temperature effect of about 150 to 200 ms/day /C thus supporting the hypothesis presented here.  
29 Jan 2011 [13:00:00]+0Having inserted the tube and opening up the chamber I am hoping we will see more uniform (and perhaps lower) temperatures down in the pendulum chamber and as a result I hope to see better temperature compensation.  
29 Jan 2011 [12:35:00]+0Unfortunately I bumped the pendulum a few times while installing the tube - hence a few glitches.  
29 Jan 2011 [12:30:00]+0I removed the boards at the top of the pendulum chamber and inserted a 1metre long 40mm tube down into the pendulum chamber with a view to encouraging cool air to descened, mix with and displace the warm air below (see photos [link] [link] thanks to Wu Hao). It has become clear that the cause of the apparent unsatisfactory temperature compensation is the fact that the lower half of the pendulum is about 2C warmer than the top half and this only occurs on very cold days. Here is an example [link] where changing tempurature of the lower half of the pendulum results in a change in going.  
29 Jan 2011 [12:28:20]+0Here is my thinking on the errors of temperature compensation. On a cold day the clock case is about 1.5C colder than the pendulum chamber as was observed on the day I moved the weather station: [link] The ideally compensated pendulum has a zinc element 2/3 the length of the pendulum (for coeff expansion Zn/Fe = 30/12 ). The bottom of the zinc element is at the bob CoM (near enough) so the top 1/3 of the pendulum length is steel with no zinc.. A temperature differential T between top and bottom (colder at the top) gives a going change of + 0.5 * 1/3 * 12e-6 = + 172ms/day /C so the 1.5C observed difference will cause the clock to run 260ms/day faster. Recent data shows that the going in the recent cold weather is about 300ms/day faster than it was in milder times [link] which is closely consistent with the calculation of 260 ms/day for the observed 1.5C temperature difference.  
19 Jan 2011 [11:27:00]+0power outage, this stopped the logging PC even though we have a UPS... Restarted at 12h45. I took the opportunity to install some proper weights for the fly (in brass 10.5 grams each, thanks to Mark Rainer for making these) so that it spins slower and impacts less on the escapement legs. This will help avoid reverse pigeon events. The amplitude dropped during the 4 minutes it took to install these.  
17 Jan 2011 [08:50:00]+1pigeon correction, +1m21s. I am often asked - surely the virtue of the gravity escapement is that it is immune to disturbances on the hands like wind, snow, birds - yes, but there is a limit. If the pigeon provides a reverse torque greater than the forward torque provided by the drive weight then the clock will stop. It is like the cruise control in a car, if there is a head wind or if you go up a hill then the control works fine but if the wind is too strong or if the hill is too steep and it overpowers the engine then the car will slow down. I have done this calculation [link] and it turns out that perhaps one, probably two pigeons sitting on the minute hand at quarter to the hour will stop the clock. Of course, sitting on the hand at quarter past the hour adds power and up to a point the escapement can cope. I suspect that the escapement has jumped on at least one occasion [link] perhaps due to a pigeon?  
16 Jan 2011 [14:45:00]+1yet another pigeon event [link] , looks to be over a minute - perhaps two. You can see that the pigeon(s) went away and came back. I need a photograph - the only one I have is of a pigeon on the hour hand.  
16 Jan 2011 [01:01:00]+1pigeon event correction, it was 21 seconds. Thanks to Beatrice, Madonna and Indiana Jones!  
15 Jan 2011 [08:42:00]+1Looks like another pigeon, my guess is 42 seconds looking at [link] because there is a point plotted every 3 seconds  
13 Jan 2011 [20:00:00]+1correction of pigeon event, +57 seconds, witnessed by Evelina, Dop, Ben, Simon, Tony, Chris and Graham - on a jolly from the Netherlands!  
13 Jan 2011 [17:45:00]+1Pigeon event - pigeon stopped clock for 57 seconds, the bastard. [link]  
11 Jan 2011 [10:00:00]+1What caused this amplitude shift? There is a small drop in temperature and if you look at amplitude v. temperature over the last month (since the weather station was moved into the pendulum chamber) [link] you see multiple episodes of correlation between amplitude and temperature, but these are probably due to changes in drag (temperature rise causes density drop). My theorythough is that a temperature rise also indicates a change in air flow so that warm air is now rising causing amplitude increase. Maybe a good idea to seal up the pendulum chamber more properly.  
10 Jan 2011 [06:35:00]+1ADJUST: +300 ms/day to 29800 - curious that ths is 3000 heavier than it was before the barocompensator was removed. Mysterious. Surely the same device returned to the same location should need the same compensation mass.  
08 Jan 2011 [11:40:00]+1ADJUST: -3400 ms/day to 29500 to compensate for the mass of the barocompensator  
08 Jan 2011 [11:02:00]+1Barometric compensator reinstalled, in the same place it was (up near the pivot) because I want to give it another chance. Thanks to Hilary for clambering around behind the clock, all witnessed by The Strassers (Mike, Lou, Peter, Andrew) and Jonnie Hunt.  
06 Jan 2011 [14:00:00]+1Mark has measured the expansion coefficients for both the aneroids at 0.03 mm/mbar - so they are working fine. In fact this is 40% more sensitive than I had assumed, so it is a mystery why the barocomp is not working. I have a theory that there is something funny about the way the flexure of the pendulum suspension works, so I am going to have a go putting the compensator further down the pendulum, away from the flexure. This is what Philip Woodward did ... so maybe there is a good reason. It will mean having to screw up the regulation nut under the bob again - which is what stuffed up the temperature compensator last time. Ah well, it all makes work for the working man to do.  
06 Jan 2011 [10:00:00]+1... the observant amongst you will have noticed that the clock sped up by 3 seconds retrospectively. This is not relativity in action - it is simply that the clock is actually sounding half a second fast at the moment, so I have brought the logger in line with the real world. Yes, there is a real world!  
05 Jan 2011 [21:30:00]+1So the barocompensator is removed. This means that I now have to do what I used to do and check the pressure forecast at BBC weather [link] because I know that the clock loses -8ms/day per mbar of pressure rise. The barometric presssure is due to rise by 20mbar over the next 6 days so lets see if the clock slows down by 120ms/day.  
05 Jan 2011 [19:00:00]+1ADJUST: +5500 ms/day to 32900 now that the barocompensator has been removed  
05 Jan 2011 [18:55:00]+1The old computer as been reinstated until we can figure out compatibility of NiDAQ drivers with OPENSUSE 11.3 Many thanks to Tim Gale for his help! Useful to record that NiDAQ drivers are updated using sudo updateNIDRIVERS `uname -r` and also to update to the server use lftp -f uploadData.lftp .  
04 Jan 2011 [14:35:00]-1Removed the barometric compensator for bench testing - this required stopping the pendulum. Thanks to Hilary Costello for climbing around behind the clock.  
04 Jan 2011 [12:00:00]-1 Datalogging suspended due to replacement of computer - the old one did not have enough memory to run the webcam reliably. Thanks to Tim Gale and Anson Cheung for all their efforts  
02 Jan 2011 [13:20:00]-1ADJUST: +400 ms/day to 27400 thanks to Mark Rainer. The barocompensator is not doing its job. I will remove it on Tuesday and give it a good look over.  
31 Dec 2010 [11:30:00]-1It is hard to tell how well the barometric and temperature compensators are working because temperature and pressure change at the same time. This is where the monitor page come in [link] because an equation for working out drift from temperature and pressure data can be tested. The equation I am testing is: Going = -120*(Temp-6)-8*(Pressure-1013)-40*dTemp/dt -60) and it fits pretty well. Here is a direct link to the drift estimate and the actual drift - a good fit [link] and the XY plot [link] shows a straight line. If this equation is right then it means that the variation of going with temperature is -120 ms/day per deg C [-520] , with pressure is -8 ms/day per mbar [-8] and with rate-or-change of temperature is 40 ms/day per degC/day [0]. The values in [ ] are for an uncompensated pendulum.  
23 Dec 2010 [13:55:00]-1ADJUST: +100 ms/day to 27000 thanks to Hilary Costello and Alice Cicirello  
21 Dec 2010 [12:30:00]-1ADJUST: -500 ms/day to 26900  
19 Dec 2010 [09:38:00]-1Bedmaker Effect, interim conclusion: 1: opening the door in the room below on a cold day causes the air flow in the pendulum chute to change (a cold downwards air flow is replaced by a warm upwards air flow) because of the chimney effect forced by the tall heated staircase in the building. 2: as the air warms up, the density and viscosity of the air both fall allowing the swing amplitude to increase. 3: The change in direction of air flow (downward to upward) causes the Going to drop (the clock slows down) because upward drag on the pendulum causes an apparent reduction in g.  
19 Dec 2010 [09:37:00]-1Bedmaker Effect (continued) 2: the Going changes more dramatically [link] . What is interesting is that there is a step change in going of about -900ms/day and this occurs straight away, not at all related to the gradual temperature rise. This is clear in the scatter plot [link] (ok, there is a gradient at the expected slope due to thermal expansion, but this is after te initial step occurs. It was Dwight Elvey who made me look again at this, and I think he is right - the observed change in going could well be due to the change in air flow up the chute. If descending cold air is replaced by rising warmer air then the sudden change in direction of air flow will cause a change in Going. This has been looked at in the Theory section of the website, and in Section 4.6.4 and estimate was calculated as -300ms/day per 1m/s of upward air flow. This suggests that the change in upward air flow this morning should have been around 3m/s - which is pretty fast. Certainly measurable. I will have to invest in a digital anemometer now!  
19 Dec 2010 [09:36:00]-1Bedmaker Effect (continued) So, here are some observations: 1: amplitude changes linearly with temperature, as can be seen in a scatter plot [link] and the fact that the rise curve and the fall curve follow each other (ie there is no hysteresis) really suggests that the temperature sensor responds quickly to temperature change and that the amplitude measurement is due to air temperature change. The gradient is about 0.8mrad/C which agrees really well with theory for how drag varies with air density. Nothing definite yet, but the evidence for this theory is mounting.  
19 Dec 2010 [09:35:00]-1Bedmaker Effect, just opening the door (no bedmaker!) on a cold morning, -4C outside. Heating on inside, really toasty. So, opening the door causes a chimney effect, forcing warm air into the pendulum chute. This temperature rise can now be seen [link] because the weather station is located in the pendulum chute itself. I have made some observations and these are in separate comments above.  
18 Dec 2010 [12:01:00]-1Conclusion on temperature sensitivity of sensor: It seems that the sensor setup is not temperature sensitive over the range of temperature changes observed in the Bedmaker Effect (below 1C change). The key indicator is seen here [link] where the amplitude change when a hairdrier is blown onto the sensor is in the wrong direction.  
18 Dec 2010 [12:00:00]-1It is good to see that the clock has settled down to where it was. [link]  
18 Dec 2010 [09:39:27]-1Expt 3: [link] Now a hair drier is used to warm up the sensor, and at the same time part of the pendulum shaft is warmed up (it is not possible with a hair drier to target the sensor being so close to the pednulum shaft). We see that there is a small change in indicated amplitude, and this is downwards consistent with the negative temperature sensitivity of the sensor as found in expt 1. But most significant is a very large change in going (slope of the drift) to -1700ms/day. This is consistent with lengthening of the pendulum due to thermal expansion, and it is a large effect because the hair drier is quite hot.  
18 Dec 2010 [09:33:36]-1Here [link] I bumped the pendulum while moving the temperature sensor into the pendulum chamber. The idea now is that the temperature indicated on the website is now the temperature inside the pendulum chamber rather than in the clock case.  
18 Dec 2010 [09:21:33]-1Expt 2: [link] The same again, but the soldering iron is in place for about 5 minutes. This time there is a bigger effect on amplitude (about -0.2mrad) but again no significant effect on going. The thing to note is that the indicated amplitude change is negative, so that the effect of rising temperature is to reduce the indicated amplitude, but temperature change does not appreciably change the indicated rate of Going. The air temperature that the soldering iron produces around the sensor is HOT - very much higher than anything that the central heating will produce. It seems then that while the sensor is indeed temperature sensitive it cannot explain the Bedmaker Effect.  
18 Dec 2010 [09:17:30]-1Experiments, in the light of helpful comments by Dwight Elvey who rightly points out that the optic sensor is probably temperature senitive. See [link] . Expt 1: placed a hot soldering iron under the sensor for about 30 seconds (wanting to warm up the sensor without warming up anything else). Note that the amplitude drops by about 0.05mrad while the going (slope of the drift) is unchanged.  
17 Dec 2010 [09:05:00]-1It is good to see a prediction come true! Interesting to note, with a longer period of the door being open, that the amplitude looks to be increasing exponentially by about 0.4mrad at a time constant of about 20 minutes. The going does not show any decay - just a step of about -450ms/day. This reinforces the theory that the change in going is due to a change in length of the outer tube due to thermal expansion - corresponds to a temperature change of +1C. The puzzle to figure out now is a mechanism for the observed change in amplitude that corresponds to a change of +1C.  
17 Dec 2010 [07:40:00]-1I asked the bedmaker to leave the door open for 20 minutes today [link] . Another concern: is the barometric compensator working [link] ? The blue data points should form a horizontal line - but they are following the -8ms/day per mbar lines exactly as we had before the compensator was installed.  
15 Dec 2010 [14:50:00]-1ADJUST: +200 ms/day to 27400 - not getting this nailed as quickly as I would like. Hopefully then clock will drift toward zero over the next few days and then I will make a final adjustment in the new year.  
11 Dec 2010 [07:40:00]-1The Bedmaker Effect is absent - as expected, it is a Saturday. But I have a theory for what has been going on, and the sums sort-of stack up [link] . Essentially, warm air is forced into the pendulum chamber causing amplitude to increase due to reduced drag and going to decrease because the outer tube of the pendulum warms up - it takes a while for the temperature compensation to reach equilibrium. A test to do on a cold morning next week will be to leave the door open for long enough for an equilibrium to be reached.  
10 Dec 2010 [09:30:00]-1ADJUST: -900 ms/day to 27200 should stabilize now that the draught-up-the-pendulum problem is fixed  
10 Dec 2010 [07:45:00]-1cleaning lady leaving the door open. Hopefully over the weekend there will be no such glitches at 07h45, nor next week during which I have asked her to leave the door closed. Perhaps, as a treat, I will let her open the door next Friday!  
09 Dec 2010 [07:35:00]-1So the plot thickens. I went in at 07h30 to see what is responsible for this amplitude glitch at 07h35 every morning [link] , it happened again today. Is it the strike silencer? No, this releases at around 07h20. Is it the sun at sunrise? No, the sun does not shine on the clock tower until about 08h10, and it is not until 08h45 that the window into the clock case is out of the shadow of the S-E turret. Is it the central heating switching on? Well, not sure, but the event is so sudden and short-lived that the heating switch-on cannot really be responsible. But at precisely 07h35 I heard a noise. It was the cleaning lady opening the door of Dr Hopkinsons room below. I went down to see her and asked if she came in at this time every day and she said yes, exactly this time - not on weekends. How long does she stay? About 10 minutes. Now, when she cleans she leaves the door wide open. This might explain why Dr Hopkinsons comings and goings have no effect. So I asked her if she would leave the door open again tomorrow but next week she will close the door when she cleans. We will see if it makes a difference. But I am still really puzzled: the pendulum chamber is now (since Tuesday) fully taped up and I cannot see any obvious places for draughts to get anywhere near the clock. Maybe there is a non-draught-related explanation - perhaps the cleaning lady is attractive to long swinging objects? Next week will be interesting. (By the way, this glitch is small by comparison to others eg pigeons and spiders, but it is curious all the same)  
08 Dec 2010 [18:22:00]-1here is an experiment, showing the effect on amplitude of the maintaining weight [link] , over a period of 18 minutes. It seems that the maintaining weight reduces pendulum amplitude at a rate of 0.01mrad/min. This is due to pallet friction, I think. It makes the effect observed earlier today all the more puzzling - the same rate of change but in the opposite direction! Note that the increased maintaining weight has no effect on going, but the 07h35 glitch shows on amplitude AND going. There is another effect in play here. What a mystery!  
08 Dec 2010 [07:35:00]-1what is this glitch [link] ? It lasts for about 10 minutes, increases amplitude by about 0.015mrad/min and seems to occur every morning at around 07h35. Now that the draught problem appears to be solved we can see more little features. maye it is something to do with the strike-sliencing mechanism? The thought is that it affects the going train as it releases between 7am and 8am. But surely this should have the same effect as the maintaining weight - ie increasing pallet friction and therefore reducing pendulum amplitude. I should check the effect of the maintaining weight this evening.  
07 Dec 2010 [23:00:00]-1sealed up the pendulum chamber with tape, thanks to Hilary Costello for help. Note that pendulum amplitude drops straight away - a good sign. The amplitude rapidly settles to a steady value overnight. The test will be at 8am tomorrow - will there be a glitch in amplitude? I hope not.  
07 Dec 2010 [08:00:00]-1Recently there have been sudden shifts in pendulum amplitude starting at around 8am every day. I suspect this is when the heating comes on, or perhaps when the cleaning lady opens the door in the room below. It is regular as clockwork on weekdays (see today(Tuesday) [link] and yesterday [link] but note that there was no glitch on Sunday [link]). Whatever the cause, recent cold weather has highlighted the variability of pendulum amplitude with air temperature. There is a cold draft coming out of the cracks around the door of the pendulum chamber so perhaps air currents around the pendulum are to blame. Suspected this for ages, so maybe tonight I should seal up the gaps and find out.  
05 Dec 2010 [16:30:00]-1ADJUST: +1100 ms/day to 28100 The amplitude is very high. Is there something to do with a cold draught in the pendulum shaft? Replaced covers to minimize space for air flow.  
02 Dec 2010 [12:00:00]-1Many thanks to Douglas Young for modifying the code to deal with temperatures below 10C - it was one of those coding things, that the data file had two spaces when the temperature was one digit, meaning that temperatures were not read in at all. Now we can monitor effects as the temperature plunges.  
28 Nov 2010 [15:50:00]-1ADJUST: +600 ms/day to 27000 still settling in  
28 Nov 2010 [13:30:00]-1ADJUST: +700 ms/day to 26400  
27 Nov 2010 [21:10:00]-1ADJUST: +000 ms/day to 25700 note that we have a new weight configuration  
27 Nov 2010 [20:30:00]-1Note that the temperature rose during this exercise - we had a fan heater going because the outside temperature was sub-zero. This should give us a good opportunity to see if the temperature compensation is working as it cools down overnight...  
27 Nov 2010 [20:00:00]-1We finally got it all back together after about 5 hours work, only to find that the clock was gaining about 140 seconds per day. We then had to wind down the regulation nut on the pendulum bob by 3.5 turns. We then had to reset the bells, but in so doing we found that the second hand was out-of-synch with the quarters bells. All these unintended consequences of our simple readjustment of the pendulum!  
27 Nov 2010 [18:00:00]+1We re-assembled the pendulum, but in so doing we noticed that we had bent the gravity arms of the escapement. In order to prevent further damage we removed the gravity arms. We also re-instated the original suspension (as was removed in October). The repositioning of the gravity arms caused problems with bouncing of the escapement so we decided to adjust the fly on the escapement. This did not work so we had to dismantle the fly.  
27 Nov 2010 [16:20:00]+1Today we (Graham Newman, Mark Rainer, Hugh Hunt) had a go at fixing the temperature compensation of the pendulum. We stopped the clock at 16h20, disconnected the barometric compensator, removed the optic sensor, then Mark had made up a neat cradle for the pendulum bob so that we could remove the pendulum shaft while leaving the bob behind. We then dismantled the pendulum. There was a bit of corrosion but not enough to explain a lock-up of the compensator. We found that the zinc tube was bent by about 3mm at its centre - perhaps enough to have locked the mechanism up if it had got twisted?  
16 Nov 2010 [21:15:00]+1Correction of -15 seconds for a reverse pigeeon event. It seems that the removal of the weights on the gravity arms (17h30 30 Oct) means that the gravity arms jump more easily, as observed when the maintaining weight is engaged alongside the main driving weight. A Pigeon on the hands at hh:15 will have the same effect as a maintaining weight.  
16 Nov 2010 [15:35:00]+1ADJUST: +800 ms/day to 29500 It is clear that the temperature compensation has gone wrong [link] . Quite possibly when we adjusted the regulation nut we managed to jam something in the set of steel/zinc concentric tubes that make up the pendulum [link]  
11 Nov 2010 [08:00:00]+1TC works staff were checking out clearance in the pendulum case - they must have touched the pendulum  
09 Nov 2010 [13:25:00]+1ADJUST: -500 ms/day to 28700 Now that the pendulum is swinging nicely we can see that the temperature compensation is not ideal - sticking somewhere?  
04 Nov 2010 [08:25:51]+1ADJUST: +500 ms/day to 29200 maybe the new suspension is settling in. No matter how tight the screws are the spring will ratchet down against friction.  
02 Nov 2010 [14:30:00]+1ADJUST: +200 ms/day to 28700 - a minor adjustment, given how much change there was on Saturday  
30 Oct 2010 [20:00:00]+1The new steady-state amplitude of the pendulum appears to be 48mrad where it was 55mrad before the gravity arm weights were removed. The going seems to be very steady.  
30 Oct 2010 [18:30:00]+1the clock was restarted and adjusted to winter time.  
30 Oct 2010 [17:50:00]+1ADJUST: -000 ms/day to 28500 NB new weight configuration due to big changes today. the clock was stopped again to allow the strike to be correctly positioned and for the adjustment for winter time to be be effected.  
30 Oct 2010 [17:30:00]+0it was observed that the pendulum amplitude is much greater than it used to be - climbing to over 60mrad. It was decided to remove the two extra weights from the gravity arms - thought to date from the mid eighties when Andrew Huxley had them installed in order to prevent the clock from stopping. It may be, way back then, that the problem all along was rubbing against the pendulum chamber door and impact with the door lock.  
30 Oct 2010 [16:30:00]+0the clock was restarted. After such drastic alteration to the pendulum the clock was going at -236 seconds per day so it was necessary to make drastic adjustment to resume steady going. The regulation nut at the bottom of the pendulum was used. First we tried 2 full turns, then 2 more, then 2 more. This was too much. It appears that each full turn increases the going by 45 seconds per day. We then backed off by half a turn, then another half and then one final half turn. This is where we left it.  
30 Oct 2010 [15:30:00]+0a new suspension was installed. It has 100mm radius cycloidal cheeks and these may help to regulate the variation of going with amplitude. It has a thinner flexure. The barometric compensator was re-installed. The computer logging system was re-located to the easte end of the clock room, and the associated instrumentation was also moved. It all looks a lot tidier.  
30 Oct 2010 [14:30:00]+0The clock was stopped. The pendulum suspension was removed in order to understand why the pendulum moves with a twist. There is accumulated grime in the suspension but no sign of a crack as was suspected. What seems to be happening, though, is that not only has the pendulum has been rubbing on the pendulum-case door it has also been bumping into the door lock. We have removed all obstruction from the pendulum case door and hopefully this will give the pendulum a free swing.  
30 Oct 2010 [14:00:00]+0A big day of work planned. Present were Rosie Ayton, Sam Ricketson, Hilary Costello, Tim Gale, Mark Rainer, Graham Newman, Hugh Hunt  
19 Oct 2010 [13:10:00]+0ADJUST: -400 ms/day to 43170  
02 Oct 2010 [15:05:00]+0ADJUST: +250 ms/day to 43570 witnessed by Cindy and Rob. Not sure why I should be doing this - the going was so good early in September and now it has gone all over the place. Perhaps time to look at the suspension spring... Rob, stickler for symmetry, had me put the regulation weights more evenly on each side of the pendulum shaft - maybe this will help!  
30 Sep 2010 [10:45:00]+0The pigeons are certainly back, caused a 30-second glitch  
25 Sep 2010 [08:45:00]+0A pigeon event, caused a glitch of 27 seconds  
16 Sep 2010 [09:45:00]+0The first pigeon event of the autumn. They are back. Damn. [link]  
13 Sep 2010 [08:00:00]+0Something happened here - after two weeks of beautiful steady going the amplitude has suddenly dropped and the clock is racing. I suspect the pendulum is touching something. Maybe the door to the case has blown itself closed?  
07 Sep 2010 [11:00:00]+0Wonderful steady going. The sudden pressure drop due to recent bad weather did not affect the going - barometric compensator working very well.  
07 Sep 2010 [10:45:00]+0Bill and Shirley Burbidge from Perth WA visited today. While waiting they saw two pigeons land on the minute hand at 11h45. They said that the minute hand bounced up and down as if it were on springs. Interesting that the two pigeons didn not cause a glitch. Maybe it takes three! I really need photographs...  
31 Aug 2010 [12:50:00]+0ADJUST: +120 ms/day to 43320 as witnessed by Sean Holden. The aim now is to be at zero for time change in October.  
06 Aug 2010 [22:00:00]+0correction +48 seconds for pigeon even of 29 July - see [link] - thanks Anson Cheung for doing this!  
05 Aug 2010 [07:15:00]+0ADJUST: +300 ms/day 43200ms  
03 Aug 2010 [06:20:00]+0A massive effect! One theory for why the pendulum only sometimes rubs the door of the clock case is that the lean of the tower varies with seasons and temperature. Ground water table variations will affect foundations (the post on my garden gate demonstrates this admirably). Also I estimate that the sun shining on the south-facing wall of the tower could cause a 5C temperature difference between the S and N faces, hence causing a lean, and 0.2mm shift in the position of the pendulum ...  
02 Aug 2010 [17:30:00]+0Restart computer after a power cut. Also opened the pendulum door a bit. Et voila! The going is now -300ms/day. Looks as if Graham-the-sleuth Newman hit the nail on the head. We will wait and see...  
01 Aug 2010 [22:00:00]+0Graham sensibly suggested that maybe the door of the pendulum case is rubbing on the pendulum - this would make sense as we closed the door firmly and locked it, where it was only partially closed before. This would reduce pendulum amplitude and hence speed the clock up  
29 Jul 2010 [07:50:00]+0Pigeon on minute hand, about 45 seconds duration, see [link] - corrected 6 Aug 2010  
24 Jul 2010 [17:40:00]+0Today we had a visit from the Antiquarian Horological Society - Turret Clock Group. More experts the clock has surely never seen. A good day was had by all. Afterwards Graham Newman and I tried to measure the diameter of the pendulum bob - without stopping it. I was holding the tape measure, but I guess I slipped ... hence the glitch on amplitude and drift.  
11 Jul 2010 [15:05:00]+0ADJUST: -100 ms/day 42900. This hot weather is doing something strange. Not surprised! Helped today by the Gunners: Vanessa, Alex, Melissa, Sumie and Chris.  
06 Jul 2010 [22:30:00]+0ADJUST: -100 ms/day 43000. Needed a bit more. Thanks to Eduardo, Cecilia, Zoran, Kai und Michael  
02 Jul 2010 [06:00:00]+0power cut caused logging system to shut down. Restart thanks to Tim Gale, the earlybird. Webcam was not restarted - we arere working on it.  
30 Jun 2010 [00:00:00]+0I think this sudden change in going is caused by a change in the direction of air flow up the pendulum chamber  
14 Jun 2010 [14:00:00]+0ADJUST: -250 ms/day 43100ms, Clearly I did not get this right. Try again (with the help of Jane, James, Maggie, Elsie, Naomi!)  
16 May 2010 [13:00:00]+0ADJUST: +30 ms/day 43350ms, getting fussy! I should really wait now to see what the barocompensator does.  
07 May 2010 [20:15:00]+0ADJUST: -50 ms/day 43320ms, just a little bit more...  
27 Apr 2010 [11:05:00]+0ADJUST: -130 ms/day 43370ms, this is a final adjustment (hopefully) after fitting of the barometric compensator. The clock is currently 0.14s fast and it would be great if it stayed that way for a few months ...  
15 Apr 2010 [22:00:00]+0can anyone explain why the pendulum amplitude should increase suddenly like this: [link] . It happens gradually over two hours from 10pm to midnight. The only thought I have is reduced friction on the escapement as the cable on the drum winds down from the second layer to the first, but if so then why does it not happen every week?  
08 Apr 2010 [00:00:00]+0removed the reference gradient lines for Going vs Pressure because the barometric compensator seems to be doing its job.  
30 Mar 2010 [11:05:00]+0introduced a plate to reduce airflow past the pendulum. There has been a step change in going - I wonder if this it related?  
28 Mar 2010 [11:20:00]+0ADJUST: -1500 ms/day 43500ms, bringing to -2600ms/day the total mass compensation for the barometric compensator  
28 Mar 2010 [00:15:00]+0ADJUST: -1100 ms/day 45000ms, necessary to compensate for the mass of the barometric compensator. Will need further adjustment in the morning.  
28 Mar 2010 [00:10:00]+0fitted a barometric compensator [link] , mass of compensator is 1.854kg, installed close to the pendulum flexure. As a guess, the CoG of the compnesator is between 2% to 5% away from the flexure towards the adjustment table, hence expect to have to remove about 20 to 60 grams of weight, equivalent to about 2000 to 6000ms/day  
28 Mar 2010 [00:05:00]+0plugged gaps under the floor boards to reduce air currents - and maybe to deter spiders.  
28 Mar 2010 [00:00:00]+0clock advanced for summer time.  
25 Mar 2010 [09:00:00]+0restart after another outage  
21 Mar 2010 [20:50:00]+0logger restart after a power outage  
20 Mar 2010 [12:15:00]+0ADJUST: +100 ms/day 46100ms, and advanced 30 sec for pigeon event  
17 Mar 2010 [16:45:00]+0pigeon on the minute hand caused the clock to stop for 30 seconds  
07 Mar 2010 [12:00:00]+0After a College-wide power outage the computer system was restarted.  
05 Mar 2010 [06:48:00]-1Pigeon event (now that the sun is shining again). Reset by 54 seconds on Sat 6 March, 13h15  
23 Feb 2010 [12:15:00]-1ADJUST: -200 ms/day 46000ms (barometric pressure is forecast to stay low for several more days yet...)  
29 Jan 2010 [11:00:00]-1ADJUST: -300 ms/day 46200ms (settling down to a final value, still 100ms/day more than in summer 2009)  
23 Jan 2010 [20:00:00]-1ADJUST: +500 ms/day 46500ms  
23 Jan 2010 [19:30:00]-1The difficultly in setting the Going is, I think, due to air currents up and down the pendulum chamber. If air is flowing upwards then drag reduces effective g and in addition the amplitude increases. Both these effects slow the clock down. It may be that there is a switch between upflow in spring (warm air rises) and downflow in autumn (cold air is heavy). Note the step change in going around mid November.  
19 Jan 2010 [13:50:00]-1ADJUST: +500 ms/day leaving 46000 ms  
12 Jan 2010 [23:10:00]-1ADJUST: -200 ms/day leaving 45500 ms  
12 Jan 2010 [23:00:00]-1Unfortunately, the cardboard was gently touching the pendulum which caused a massive hike in the going. Corrected.  
12 Jan 2010 [12:15:00]-1Pigeon glitch correction of 36 seconds. Also put some cardboard baffles around the pendulum shaft in an attempt to reduce the updraft and downdraft that appears to be affecting the going.  
12 Jan 2010 [12:10:00]-1ADJUST: +700 ms/day (to 45700 ms of weights) - hope to be back to time next Tuesday  
09 Jan 2010 [13:45:00]-1More pigeons - twice (30 seconds stoppage) [link]  
08 Jan 2010 [14:50:00]-1ADJUST: -1000 ms/day (to 45000 ms of weights) - I want to get the drift back to near zero. It seems as if the winter going is faster than the summer going. Does this mean that the temperature compensation is not quite right?  
05 Jan 2010 [14:20:00]-175sec correction for pigeon on 29 Dec  
05 Jan 2010 [14:15:00]-1ADJUST: -100 ms/day (to 46000 ms of weights)  
29 Dec 2009 [08:45:00]-1pigeon caused 75 second stoppage [link], corrected on 5 Jan.  
09 Dec 2009 [14:45:00]-1another pigeon caused 9 second stoppage [link] see photo at [link]  
08 Dec 2009 [10:45:00]-1pigeons stopped the clock for 4 minutes - this is getting serious! If you look closely you can see 3 separate pigeon events [link]  
07 Dec 2009 [10:45:00]-1pigeons on the minute hand, 30 second glitch [link]  
07 Dec 2009 [09:15:00]-1bumped the pendulum accidentally.  
05 Dec 2009 [07:45:00]-1another glitch [link] . BUT we now know what causes the glitches: Mr Down (a College Porter) saw a pigeon sitting on the minute hand. Indeed, the glitches always occur around hh:40 to hh:50 (when the minute hand is horizontal and rising) , and always in daylight hours. The pigeons are present on the dial in large numbers especially when the sun is shining - a warm south-facing place to sit [link] . A quick calculation: suppose two pigeon each weighing 1kg are sitting on the minute hand at a distance of 0.5m from the pivot, and so rising at about 1mm/sec. They requires 10mW of power to lift them (force*velocity). Then the 80kg _going_ weight falling 9m in 7 days generates 12mW of power (again force*velocity). So a power balance suggests that a pigeon or two can easily stop the clock.  
01 Dec 2009 [12:10:00]-1pendulum case in Dr Hopkinson s room opened, very noticable downdraft. Caused clock to speed up - as expected from theory.  
24 Nov 2009 [09:50:00]-1glitch of 33 seconds, fixed at 13h00 same day [link]  
15 Nov 2009 [09:00:00]-1power outage caused data-logging PC to shut down (College disconnected due to works on the new electricity supply to the Kitchens). The weather station data (pressure, temperature, humidity) seems to have been permanentlly affected. Will need to be fixed.  
12 Nov 2009 [11:00:00]-1solar glazing installed, hopefully will help keep the sun from shining too hotly on the pendulum  
05 Nov 2009 [08:50:00]-1glitch of 9 seconds, [link] fixed 09h45 the following day  
03 Nov 2009 [18:35:00]-1glitch adjustment  
03 Nov 2009 [15:50:00]-1glitch of 30 seconds [link] . I think the cable of the going is jamming somewhere  
25 Oct 2009 [00:15:00]-1End of Summer Time adjustment, clock advanced by 23 hours  
20 Oct 2009 [13:00:00]-1corection of 9s glitch, plus wind the clock, plus preparation for clock change on Sunday morning  
19 Oct 2009 [11:45:00]-1another glitch [link]  
09 Oct 2009 [13:30:00]-1New GPS installed. Normal data gathering resumed.  
05 Oct 2009 [16:10:00]-1GPS fault - data gathering halted. New GPS received on order.  
01 Oct 2009 [06:45:00]-1another .... [link]  
29 Sep 2009 [11:00:00]-1correction of 9s glitch plus attention to the freedom of movement of the weight cables - perhaps they are not sliding so freely against each other as they should, and a little freeing up was attempted.  
28 Sep 2009 [06:50:00]-1another glitch [link]  
27 Sep 2009 [09:43:00]-1yet another glitch in amplitude [link] , this time only 9 seconds in duration. What causes this? A real mystery.  
25 Sep 2009 [22:06:00]-1reset the time - interesting that it was only 1min40sec slow, even though the pendulum decay was over 3 minutes. The plot thickens!  
25 Sep 2009 [17:00:00]-18 days later, the same has happened again. Almost identical drop in amplitude over 3 minutes.  
18 Sep 2009 [09:56:48]-1advanced clock by over 3 minutes - whatever it was that happened last night it stopped the clock for quite a while. Close inspection of the amplitude data shows that the escapement was _stuck_ for 3mins 20sec. Is there a big spider about? Or a rat?  
17 Sep 2009 [16:13:20]-1what on earth happened here? Amplitude dropped by 2 mm!  
15 Sep 2009 [12:45:31]-1during the winding I accidentally touched the pendulum - hence a glitch in amplitude. It should settle quite quickly  
31 Aug 2009 [10:39:00]-1ADJUST: +150 ms/day (back to 46100 ms of weights). This is because the clock has had a mean drift of around -150ms/day for the month of August, and has dropped 4 seconds. Curious, though, that the clock was actually 23 seconds slow today. I wonder if a mouse/rat gets into the fly and stops the escapement from time to time? Something seems to be happening. Really need a webcam!  
25 Aug 2009 [13:00:00]-1Is this another spider? The amplitude has dropped for a few hours, no particular feature in meteo properties.  
21 Aug 2009 [13:30:00]-1Computer restarted, thanks to Sam Wenham and Rick Lupton  
30 Jul 2009 [14:00:00]+2PC FAILURE - no data available until further notice. Sorry!  
19 Jul 2009 [10:20:00]+2ADJUST: -150 ms/day (to 45950 ms of weights). The clock has crept to 3.4 seconds fast and is averaging 50ms/day fast. I hope now to drop 100ms/day for 30 days to bring the clock back in line, but who knows what the weather will do - and the spiders.  
14 Jul 2009 [08:45:00]+2ANNUAL SERVICE by Smith of Derby (Jonathan Lee and Matthew Smith). I asked them not to interfere with the escapement or the pendulum. They investigated weights scraping against the stonework during winding, found that the First Strike (Trinity Strike) was scraping. They will make a minor adjustment. Also invesitgated the uneven winding of the Going line on the Going drum. We tried refitting the line at the ratchet end but found that the line then interfered with the quarters advancing bar. General service involving oiling and a check over. As a result, pendulum amplitude has dropped. I wonder if it will recover?  
07 Jul 2009 [04:26:40]+2another amplitude glitch. We really need a webcam looking for spiders!  
04 Jul 2009 [19:35:00]+2 1100 ms/day removed briefly to check calibration  
03 Jul 2009 [11:00:00]+2... no further adjustment necessary (a pleasant surprise)  
02 Jul 2009 [17:00:00]+2replaced miscellaneous washers with calibrated brass weights (courtesy Gareth Ryder who has also made a nice box for them). It was not possible to get the weight exactly right so I suppose an adjustment will be needed tomorrow, or over the weekend after the amplitude has settled down.  
15 Jun 2009 [09:30:00]+2ADJUST: -130 ms/day (to 46100 ms)  
11 Jun 2009 [13:45:00]+2Logging interrupted to install UPS.  
08 Jun 2009 [04:00:00]+2... another spider? What caused the 1mrad (=1mm) drop in amplitude at 4am, recovered 2 hours later?  
19 May 2009 [15:44:38]+2Another curiosity is that small changes of Going vs Amplitude [link] shows a positive slope - not sure why. And there seem to be clusters - as if behaviour changes quickly and sits still for a while. The normal physics of a pendulum [link] predicts a negative slope, as here [link] so there is something more subtle going on. Maybe the spider again?  
19 May 2009 [14:58:20]+2Just a general remark, it has been noticable over the last few days that pendulum amplitude forms a nice linear relationship with air density. This fits perfectly with a 0.5*rho*V^2 drag law. see [link]  
19 May 2009 [12:05:00]+2clock wound at 1.05pm - note the small glitch in amplitude, perhaps opening the clock case causes air currents that causing a small change in pendulum motion. Or maybe the act of winding moves the clock bed slightly causing the pendulum to be disturbed.  
17 May 2009 [00:00:00]+2... and why has it suddenly changed back at midnight? There is no change in anything else - some physics not accounted for here!  
14 May 2009 [23:30:00]+2What caused this gradual change in going, over 8 hours before and after midnight?  
12 May 2009 [12:05:00]+2clock wound at 1.05pm. temp is stable and going seems to be spot on zero. Might this last until October now?  
06 May 2009 [09:00:00]+2the spider again? Things settle down well after this - back to normal and very good running.  
03 May 2009 [16:00:00]+2very strange event, amplitude dropped by 1mrad so clock sped up by 1s/day, corrected itself the next morning. Could this have been a spider spinning its web between the pendulum and the casing? This is a really good event to plot as Going vs Amplitude becvause it obeys the pendulum physics beautifully. [link]  
01 May 2009 [13:00:00]+2ADJUST: +80 ms/day (to speed the clock up)  
15 Apr 2009 [01:00:00]+2clock stopped due to lack of winding  
20 Mar 2009 [14:26:11]-1logger restarted