"Christopher Tidy" wrote in message
...
Hi all,

Thanks very much for all the information. Sorry for the original
cross-post; I was expecting very few replies.

In answer to some of your questions, the clock is a WWII German
"Dehomag" slave clock, originally designed to be driven by a master
clock. It has no second hand. The minute hand appears to be balanced,
but the hour hand not. The clock is about 14" across, so not huge, but
it's exceptionally heavy as nearly everything is made from 1 mm steel
plate. Here's a picture of the clock:

http://www.mythic-beasts.com/~cdt22/dehomag.jpg

I can't decide whether to repaint it black, as it was when
manufactured, or to leave it grey. It's for my bedroom, so if it were
to stop during power cuts I wouldn't mind. It sounds like the 50 Hz
grid frequency will be a plenty accurate time keeping source, and it's
an interesting solution to the problem. We live in a pretty rural area
so I'll try to design a circuit which will be fairly resistant to
noise. I had already planned to put a Schmitt trigger on the input
from the step-down transformer.

Once again, thanks for all the advice. It's much more than I got from
the National Grid - the phone number on their website doesn't even
work!

Best wishes,

Chris
You did not tell us what the drive mechanism is.
If it was similar to the Simplex/IBM master clocks of the time it most
likely advanced every minute by a pulse to an electromagnet.

Now there are several ways you could generate that.
A Small timer motor with a cam like a washing machine timer.
Or an Electronic cct synched by the mains.

If it is for your bedroom you may not want it after the first few hours
as the electromagnet noise will drive you bonkers.
--
John G

Wot's Your Real Problem?