Re: Quartz Accuracy for a Grandfather Clock

On Sat, 04 Feb 2006 20:42:36 +0000, Joseph2k wrote:
Dave (from the UK) wrote:
Genome wrote:
"Ray & Kathy Albertson" <spam@xxxxxxxxxxxxxx> wrote in message

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.

It doesn't matter. You need to introduce a little magic. Just rip out
the guts of the clock, and put in a proper digital clock movement, but
use the original hands, just get a rotary-hands-type clock movement. Then,
leave the pendulum and its escapement running - tick, tock, tick, tock
- and nobody will bother to stand there and watch for the five or ten
seconds it would take to find out whether the pendulum and clock hands are
in absolute sync. It's sometimes amazing what a little artful deception
can get away with! ;-)

Good Luck!
Rich

.

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