> [TELECOM Digest Editor's Note: City of Chicago used DC power (rather
> than AC) -- at least in the downtown area -- until sometime around
> 1930. That's at least one reason why there were so many WUTCO clocks
> everywhere, instead of 'regular' wall clocks. Clocks cannot run on
> direct current; they require alternating current at 60 cycles.
I imagine the battery powering most wall clocks used nowadays would be
surprised by that statement (if it could think, of course).
Clocks may have used the 60 hz cycle as a timing mechanism, of course,
where a modern clock may use something else that oscillates, such as a
quartz crystal.
Daryl
[TELECOM Digest Editor's Note: But you see, Daryl, in the little wall
clocks with a battery in them, the battery does _not_ drive the
escapement in the clock. The battery merely feeds a little motor which
_winds up_ the spring which forces the escapement to work, which is
how the old Western Union clocks operated as well. If you take the
wall clock down from its place, hold it very quietly for a few minutes
and listen, typically after every three or four -- maybe in some cases
ten minutes, you'll hear a little 'whirring' sound which lasts for
a couple seconds as the spring gets re-wound which in turn drives
the escapement gear, causing it to repeatedly try to force its way
past the two 'fingers' which alternatly jump up and down, trying
to resist the pressure. You could as easily remove the battery totally
then stand there and every five minutes or so use some tiny little
tool to wind the spring by hand. In a _true_ electrical clock, where
a motor inside spins continually there is no escapement; no reason
to ever so slightly retard the gears. Putting it the other way around,
if you removed the battery, then carefully lifed the 'fingers' and
the pendulum out of the way, even with the battery gone, you'd see
the hands on the clock spin around rapidly until such time as all
the tension in the spring was gone. For true electric clocks, they
require AC current at 60 cycles, or else they would speed up or
slow down eratically as the current fluctuated. The old Western Union
clocks would rewind their mainspring hourly; the little more modern
clocks currently in use have _much_ smaller mainsprings and escape-
ment wheels; the battery has to refresh them as stated above; between
3-5 minutes up to 10 minutes as needed. PAT]
Daryl Gibson (daryl.gibson@gmail.com)