In message <un0nte$2kgeg$
1@dont-email.me> at Tue, 2 Jan 2024 10:17:12,
NY <
me@privacy.invalid> writes
[]
I'm always amazed that the clock in the Elizabeth Tower which drives
Big Ben can be made so accurate. My experience with clockwork clocks
(eg chiming granddaughter clocks) is that each one gains or loses a
variable number of minutes each day - each one is not (for example) >consistently five minutes slow 24 hours after being set correctly, but
the error varies day by day. And that's for clocks which have been
repaired within the last year or so. I imagine that the pendulum of
"Big Ben" (shorthand for "the clock that drives Big Ben") is well
compensated for variations in temperature and therefore length. I know
It was part of the original specification for the mechanism that it be
very accurate - it was pushing the limits for such clocks at the time,
but was achieved.
they used to (maybe still do) add/subtract coins on the pendulum weight
to make subtle changes to its length. I imagine for important events
like New Year is is tweaked *very* accurately!
Last time I saw any documentary on it, they were indeed still doing that
- using old pennies, and logging what they were using - I think last one
I saw they were logging it on a computer, so fairly complex calculations _could_ be made.
With modern digital timing and a light beam which is broken by the
pendulum rod, they can probably time the swing of the pendulum very >accurately and so, even averaging over just one swing, they can
determine very accurately how fast or slow it is ticking and therefore
how much correction needs to be made to the period. A bit different to
I don't remember any mention of anything like that. I think basically
for the purposes it is used, they don't need to be _that_ precise.
our clocks which have a pendulum which is only a couple of inches long
and which has a simple knurled nut which screws up and down the shaft
to make the bob rise or fall. The very act of moving the clock to get
at the pendulum, and then unhooking the pendulum to adjust it and then >re-hooking it, probably introduces changes in addition to the
adjustment of the knurled nut. We're fighting a losing battle! We've
got used to tweaking the time of our clocks every morning so they are
at least reasonably correct for that day.
One aspect you don't have to deal with is bird loading: at certain times
of year, starlings on the minute hand cause an appreciable slow-down or speed-up effect on the mechanism!
Something that has occurred to be about software imitations (and the
real thing): I use ClockSmith Lite, but I'm sure there are many others.
These usually work such that the first of the 16 quarter chimes occur on
the instant; in the real clock, it's the first bong that is the denoter.
So the chimes must actually set off in advance of the hour.
(Another thing I hadn't appreciated until I saw it explained: there are
_five_ four-note sequences. You'd think that, for the four quarters,
you'd get sequence A at quarter past, AB at half, ABC at quarter to, and
ABCD on the hour, but for mechanical reasons, that's not the case: you
get A, then BC, then DEA, then BCDE, ready to be back at A [my arbitrary lettering].)
--
J. P. Gilliver. UMRA: 1960/<1985 MB++G()AL-IS-Ch++(p)Ar@T+H+Sh0!:`)DNAf
"quidquid latine dictum sit, altum viditur". ("Anything is more impressive if you say it in Latin")
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