Coronation Chairleg - for King Charles's birthday.

Tomorrow morning, 10am GMT, I'll be fast forwarding the clock in Trinity College by 23 hours. This is instead of putting the clock back an hour.

You might like to stand in a Great Court and watch the hands whizz around.

It's been a summer to forget.
25 June - 6 Aug only averaged 1006mbar (STP is 1013mbar).
In 6 wks TC clock gained 2s. Oh no!
Why? Low air pressure = low density which decreases buoyancy of pendulum bob so apparent 'g' is more. Period=2π√(L/g) so clock goes faster. Trinity College

Some background to The Great Court Run is here en.wikipedia.org/wiki/Trinity_G… - yes the idea is to run around Great Court (about 339 metres) in the time it takes for the clock to strike 12. Here is the run in 2012 youtube.com/watch?v=enmeCn…

5. Happy running!

4. Then there's air density. The spinning 'fly' controls speed by air drag and that depends on air density. It's clear then that the best chance of beating the bells is on a cold dry day 3 days after winding. .../5

3. There is also the effect of weight of the cable so we can see that the strike goes steadily faster as more cable plays out, and then suddenly slower after 3 days when the cable goes down to a single layer on the drum. .../4

2. This is in part because of air density (tempreature/pressure/humidity) but the biggest effect is that the weight driving the bells runs onto a second layer on the drum which gives a bigger torque and therefore faster striking .../3

The Great Court Run is coming up. I've done an analysis over two years 2018-2020 and the time it takes to strike 12 averages 48 seconds but sometimes as slow as 46 seconds and as long as 50 seconds .../2

Thanks Sarah for driving so expertly! Trinity College

Really lovely working with Sarah and Robero Trinity College

Pigeons landing on the minute hand at quarter to the hour can stop the clock trin-hosts.trin.cam.ac.uk/clock/main.php… Trinity College

Here is the pigeon wire close up Trinity College It's very effective at keeping the pigeons off because they can't see their feet as they land

Thanks to Sarah and Robero for taking me up to the clock dial in a cherry picker to tighten up the pigeon wire on the minute hand. Trinity College

Very pleased with this experiment to illuminate the clock dial Trinity College Alumni Trinity College

Tomorrow at noon I'll be ringing the bell in the clock tower of Trinity for 7 minutes, to mark the 7 days so far of the invasion of Ukraine.

Windy today in Cambridge

The Tonga Volcano pressure pulse was felt in the Clock Tower twice after the event, 15 hours the short way (16500km) and then 22 hours the long way (23500km) - both which match a speed of sound of about 300m/s. Amazing. trin-hosts.trin.cam.ac.uk/clock/main.php…