Re: Quartz Accuracy for a Grandfather Clock


"Dave (from the UK)" <see-my-signature@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
wrote in message news:43e3f99e@xxxxxxxxxxxxxxxx
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.

--
Dave K

http://www.southminster-branch-line.org.uk/

FWIW:
http://www.nawcc.org/museum/nwcm/galleries/electric/kennedy.htm
Wall Clock, 1867, S. A. Kennedy, New York

"S. A. Kennedy patented this first American electric clock in 1867. It has
an electromagnet, pendulum driven movement."



http://www.nawcc.org/museum/nwcm/galleries/electric/electric.htm
"Electricity has had numerous horological applications. In early
battery-powered clocks, an electromagnetic impulse maintained the consistent
rate of a balance wheel or pendulum."


also
http://www.nawcc.org/museum/nwcm/galleries/precision/precision.htm

Apologies for butting in.

***


.