Whats this clock for and hows it made?

[modeng2000Participant @modeng2000]

In the Christchurch Electricity Museum, alas no longer, there was a rotary transformer that was used to add 20 or so volts to the existing supply.

John

[GeorgineerParticipant @georgineer]

When I was an apprentice at Fawley Power Station I was told that frequency gave the “spring” in the system which enabled it to cope with rapid changes in demand, and that seems to be a very practical view of it.  I can certainly remember being on duty on a Saturday evening and watching the frequency meter in the control room drop as a popular television programme finished – I think it was Miss Great Britain – and the whole population put the kettle on, made toast and went to the loo.

George

[John HaineParticipant @johnhaine32865]

 

Talking about mains frequency stability there’s nothing like data.  This website:

https://bmrs.elexon.co.uk/rolling-system-frequency

…gives records of rolling system frequency at 15s intervals from which I downloaded the last week’s worth.  The first plot above shows time error of a clock using the mains frequency as a reference over the past week.  Basically within +20/-30 seconds, not so good.  From the data we can also plot the Allan Deviation which is in many ways a more useful measure of stability. It plots a “standard deviation” against averaging time.  Assuming I’ve driven the program that generates it correctly (Stable32) it shows that over the last week a clock looked at every 15 minutes would have a standard deviation of 1 part in a thousand.  Stability is better for shorter and longer averaging times, but certainly not comparable with a quartz clock.  Since there’s only a weeks worth of data we can’t see what happens for much longer averaging time, the Adev certainly seems to drop precipitously though there’s a slight hook at the end.

[duncan webster 1]

On duncan webster 1 Said:

Reducing frequency reduces power because all the motors connected to the grid slow down a bit, and when we had manufacturing industry there were a lot of motors. One plant I visited in Leeds had a 3000 hp motor driving a car shredder, and that wasn’t an unusually high load for a plant

Hmm… I’m not so sure!  When demand increases above the actual power input to the grid, the alternators will slow down slightly and the frequency will reduce.  But as someone above said, the equation for AC power at least for a resistive load does not include frequency.  But the generated voltage will decrease because V = dB/dt where B is flux density, so this will decrease the supplied power, actually the fractional decrease being twice the fractional frequency and voltage reduction.  Overall power factor of course comes in and slightly changes the numbers.

[HopperParticipant @hopper]

One good thing about being retired is I don’t even care what time it is! My atomic clock is the sun. When it goes down, it’s time to go in from the shed.

I should imagine the cement infill in the OP clock would perhaps be a cost-saving measure to save a bit of bronze yet still give the clock enough weight to absorb the vibrating of the largish hands etc clicking away?

[Peter Cook 6Participant @petercook6]

Judging by the  Sun Alliance quotation  above, it looks as if the clock was designed as an architectural feature. The centre was designed to be filled with a material that matched whatever the clock was mounted to so that only the  chapter ring and hands were distinguishable from the background.

What you fill with will presumably depend on the background you plan to mount it on. How about a nice marble epoxy casting resin?

[Michael GilliganParticipant @michaelgilligan61133]

The search is on, for blue print D.735

MichaelG.

.

Edit: __ a slight digression

http://www.kibworth.org/memories%20of%20gents%201.pdf

 

[John HaineParticipant @johnhaine32865]

In reply to Ian Parkin, you may get useful information by posting your question on the Electric Clocks forum:

https://groups.io/g/electric-clocks/topics

 

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