Power madness

 

In a previous post I explained how mechanical clocks and watches work, with five elements – energy, wheels, escapement, controller and indicator.  Let’s explore how some clocks and watches get their energy.

Mechanical clocks and watches employ kinetic energy, drawn from a built-in reserve – usually a mainspring (elastic potential energy) or a driving weight (gravitational potential energy).  However, these need to be replenished, or wound-up.  We commonly wind-up a clock or watch directly, with kinetic energy from our muscles (which, before that, was chemical energy from our breakfast).  In an automatic watch, a moving weight spins and winds it up as we move around.  In c.1765, James Cox made a clock that is wound by changes in atmospheric pressure.  Similar is the Atmos clock, which has gas-filled bellows which expand and contract with changes in the surrounding air temperature and pressure – this movement winds the spring in the clock.  This has been a very successful design – it was first introduced in 1928 and it is still being made.  There was even a mechanical clock made to be powered by by an artificial heat source (see image).

A top of this dial is an “up-and-down” indicator showing how long the clock has left to run - sometimes known as a power reserve indicator or  “réserve de marche”.  Marine chronometer by Thomas Mudge, Plymouth, 1774 (British Museum reg. No. 1958,1006.2119)

A top of this dial is an “up-and-down” indicator showing how long the clock has left to run – sometimes known as a power reserve indicator or “réserve de marche”. Marine chronometer by Thomas Mudge, Plymouth, 1774 (British Museum reg. No. 1958,1006.2119)

The movement of self-winding watch showing the winding weight.  Jaeger Le Coultre, Switzerland, 1959  (British Museum reg. No. 1988,0409.3)

The movement of self-winding watch showing the winding weight. Jaeger Le Coultre, Switzerland, 1959 (British Museum reg. No. 1988,0409.3)

 

 

 

 

 

 

 

 

 

 

 

 

An Atmos clock.  Jaeger Le Coultre, Switzerland, 1947 (British Museum reg. No. 1986,1025.1)

An Atmos clock. Jaeger Le Coultre, Switzerland, 1947 (British Museum reg. No. 1986,1025.1)

The bellows that wind the clock are in the large barrel behind the dial.

The bellows that wind the clock are in the large barrel behind the dial.

Table clock with “Weingeistaufzug” (“alcohol elevator”).  The black bar at the bottom-left is an electric heater - it heats the pink-coloured alcohol, causing it to rise to the upper vessel, which then drops under gravity, driving the mechanical clock movement.  Is there any form of energy not involved?!  Karl Jauch, Schwenningen c.1940 (Deutsches Uhrenmuseum Inv. 50-4135)

Table clock with “Weingeistaufzug” (“alcohol elevator”). The black bar at the bottom-left is an electric heater – it heats the pink-coloured alcohol, causing it to rise to the upper vessel, which then drops under gravity, driving the mechanical clock movement. Is there any form of energy not involved?! Karl Jauch, Schwenningen c.1940 (Deutsches Uhrenmuseum Inv. 50-4135)

A rack clock - here the weight of movement and case of the clock serve to provide the driving weight.  To wind it, the clock is simply moved to the top of the rack, and it and it drops over the bottom over the course of a day.  Charles Mabille, Paris c. 1775(British Museum reg. No. 1958,1006.1965)

A rack clock – here the weight of movement and case of the clock serve to provide the driving weight. To wind it, the clock is simply moved to the top of the rack, and it and it drops over the bottom over the course of a day. Charles Mabille, Paris c. 1775(British Museum reg. No. 1958,1006.1965)

Electrical clocks and watches employ electrical energy.  We might provide this by putting in a fresh battery (which is a reserve of chemical potential energy), although sometimes the battery is rather larger than the clock it powers!  Mains powered clocks often do not have a built-in energy reserve and so these are reliant on a continuous supply to keep going. Solar powered clocks and watches use solar panels to convert light to electricity, which then charges a battery – this reserve is essential as the power source is not reliable – e.g. day and night.

Smiths 'Sectric' electric mantel clock.  The clock is not only mains powered, but its motor is “synchronous” i.e. its speed depends on the frequency of the alternating current and this controls the rate of the clock.  This is very reliably as the mains frequency is very stable.  Smiths English Clocks Limited , London, c.1950 (British Museum reg. No. 2008,8022.1)

Smiths ‘Sectric’ electric mantel clock. The clock is not only mains powered, but its motor is “synchronous” i.e. its speed depends on the frequency of the alternating current and this controls the rate of the clock. This is very reliably as the mains frequency is very stable. Smiths English Clocks Limited , London, c.1950 (British Museum reg. No. 2008,8022.1)

The mechanical pendulum of this Synchronome master clock is kept going by an electrical device.  Synchronome Clock Company Limited, London, c.1948 (British Museum reg. No. 2008,8023.1)

This Synchronome master clock is electromechnical – its mechanical pendulum is kept going by an electrical device. Synchronome Clock Company Limited, London, c.1948 (British Museum reg. No. 2008,8023.1)

So, those are a few examples of how clocks and watches can obtain the energy they need.  Of all the types of energy I can think of, only sound and atomic energy have not been not used to directly power clocks and watches.  As to how they exploit the energy… well that is another story altogether… maybe for a later post!

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