Big Ben clock to be turned back to GMT for first time in five years

[AE-NMidlands]

https://www.theguardian.com/uk-news/202 ... five-years

“Under the cover of darkness we effectively stop the clock and hold it for two hours, only restarting it again at midnight and putting the dial lights back on at 2am when it is officially GMT.”

Que?

[Fintray]

https://www.theguardian.com/uk-news/202 ... five-years

“Under the cover of darkness we effectively stop the clock and hold it for two hours, only restarting it again at midnight and putting the dial lights back on at 2am when it is officially GMT.”

Que?

Bit more info here https://secretldn.com/big-ben-clocks-change/

[Oldgreybeard]

Not really related, but I continue to be amazed at the accuracy of old pendulum clocks. I inherited my father's long case clock, a humble farmhouse clock that's a bit tatty and which was built in 1851 (there's a date and name scratched into the brass backplate) so very close to the same age as the Great Clock. This clock is incredibly crudely made, hand filed wheels, obviously roughly hand made other components (looks like it was made by a blacksmith!) yet it is amazingly accurate.

I have a master clock (run from a GPS receiver in the loft) that provides a very accurate (essentially atomic clock accuracy) time reference and the old long case clock is never more than about 30 seconds out. I never set the time on it, as it drifts a few seconds either side of the correct time with small changes in temperature, yet overall stays in time well enough to never need the hands to be moved (except twice a year when the clocks change). Amazes me just how well a properly set up pendulum can behave.

They regulate the pendulum for the Great Clock of Westminster by adding or removing pennies to it, to change its centre of mass and hence the period of its swing. I spent hours regulating my clock by making fine adjustments to the pendulum length, via a crude square nut on the threaded end of the pendulum rod.

[AE-NMidlands]

They regulate the pendulum for the Great Clock of Westminster by adding or removing pennies to it, to change its mass and hence the period of its swing. I spent hours regulating my clock by making fine adjustments to the pendulum length, via a crude square nut on the threaded end of the pendulum rod.

No: they regulate it by adding pennies which raise the centre of gravity of the pendulum effectively making it shorter. Weight is irrelevant to period, it's the length which changes it.

[Oldgreybeard]

No: they regulate it by adding pennies which raise the centre of gravity of the pendulum effectively making it shorter. Weight is irrelevant to period, it's the length which changes it.

I realised I'd left out "centre of" when posting and corrected it just before reading your post!