Re: Quartz Accuracy for a Grandfather Clock


"Joseph2k" <joseph2k@xxxxxxxxxx> wrote in message
news:0l8Ff.17955$_S7.1104@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Dave (from the UK) wrote:

Genome wrote:
"Ray & Kathy Albertson" <spam@xxxxxxxxxxxxxx> wrote in message
news:11u49jmo0gmalbf@xxxxxxxxxxxxxxxxxxxxx

A few years ago in this group somebody mentioned the idea of using a
WWV
derived time signal to drive a coil that would be magnetically coupled
to
a
magnet puttied to the pendulum of a grandfather clock. The clock
would
be set up to run a tiny bit slow, but the pulses from the magnet would
soon
put it in sync with the time source and keep it spot-on. The article
referred to a project documented in a Scientific American article
("The
Amateur Scientist" column) from over 20 years ago.

Does anyone know of any off-the-shelf items? I googled "electronic
clock
regulator" and variations at some length and found only the device at
http://www.clockmaker.co.uk/, which sounds exactly like what I'm
looking
for but as it is being made and sold for regulating village clocks I
would imagine that it is not in the "under $100" range.

Can anybody point me in the right direction? Or am I going to have to
dig
up that old Scientific American article? Thanks!



Not 'off' the shelf' but if you want to have a dabble you might think
a
bit laterally. I could be wrong but you seem to be suggesting that
your
magnet gives the pendulum a 'kick'. That's sort of rightish but you
don't
have to give it a 'kick' you just have to modify its perception of
gravity. That means you can stick an electromagnet 'below' the
pendulum
(having bashed a steel nail through it if it's non magnetic). Now you
just have to drive the electromagnet with a variable current to adjust
the rate at which things swing.

<snip>
That's the general idea.......


That 'below' should be 'to the side'.

The electromagnet must be to the *side* of the pendulum. You then run
the clock slow (no electromagnet) and speed it up with the
electromagnet, to get the time right.

Although it can be below or above the pendulum (below is more
practical), it *must* be to the side.

If you have the electromagnet centered, then it can only reduce the
amplitude, not the time period. (To a first order approximation,
amplitude and time period are independent.) Only if it is to the side
can you chance the time period.

It will depend on what parts of the swing the electromagnet is on.
The commonest application of this that I know, has the magnet below the
pendulum, and is triggered to slow the pendulum, just after it passes the
bottom of the swing. The clock was set to run fast, rather than slow. The
trigger was done electrically, rather than 'electronically', on the
synchronised clocks used in factory time card systems. The 'master',
released the electromagnets on the slave units, as it passed the bottom of
it's swing.
I would the comments about 'magnets below', referred to this type of
system.

Best Wishes


.

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