The spring, energy accumulatorA mechanical watch needs energy to work. This energy is supplied to the mechanism by a spring which is tightened when the watch is wound. This mainspring is housed within a small cylindrical drum known as the barrel.

This spring itself (1) is a long flexible steel strip that is wound by the winding mechanism around the core of the barrel arbor (2) and stores the energy required to run the watch.

Once wound, the spring naturally tries to regain its initial shape by uncoiling, thereby producing the energy required to drive the watch.

The barrel is connected to a toothed wheel (3) meshing with the movement gear-trains.

The geartrain, the counting and transmission organThe transmission system or geartrain transmits the energy stored in the barrel to the escape-wheel.

As the spring unwinds, the barrel turns and drives the wheels.

1. The first wheel after the barrel is the centre-wheel. As its name indicates, it lies at the heart of the movement. This wheel performs 1 full turn in 12 hours , and it carries the hour hand.

2. The next wheel, called the third wheel, is an intermediate wheel.

3. The next wheel is called the fourth wheel. This wheel may also be positioned at the centre of the movement, or located at 6 o’clock on the dial. It performs 1 full turn in 1 minute or 60 seconds (which is why it is also referred to as a seconds wheel) and serves to carry the seconds hand on watches equipped with such a hand.

These three wheels are in brass.

4. The final wheel is the pallet-wheel or escape-wheel. It is not part anymore of the geartrain but of the escapement. It releases the energy transmitted via the gear-trains to the pallet-lever in an intermittent manner.

This wheel is very different from the three others. It is made of special highly resistant steel and undergoes an amazing number of shocks when hitting the pallet-lever (an average of 21,600 impacts in 1 hour, meaning 518,000 in 24 hours). The shape of the teeth is also very different. This wheel is one of the most difficult and delicate movement parts to make.

The escapement and distribution: dividing up timeThe energy constantly transmitted by the mainspring must be divided up into regular units in order to be able to count out time.

The escapement transforms the energy thus received into impulses. If this organ were not present, the wheels would turn to fast and the mainspring would be unwound in a few seconds.

The escapement constitutes the link with the regulating organ and distributes the impulses to the balance.

The pallet-lever (known in French as “l’ancre” because of its resemblance to a ship’s anchor) receives the energy initially provided by the mainspring through the impulses of the pallet-wheel. The role of the pallet-lever is to transform the circular movement of the wheel into an alternating movement to drive the balance. It performs a rocking movement corresponding to the tick and tock sounds heard when a mechanical watch is running.

(1) the pallet lever

(2) The pallet wheel

The regulating organ: the balance and spring assemblyThe balance and spring assembly represents the heart of the watch; it regulates the flow of time by means of the oscillations of the balance and is responsible for the accuracy of the watch. It is composed of a statically poised two-arm fly wheel (the balance - 1) as well as a spring (a steel spring thinner than a hair’s breadth - 2).

The balance performs a circular to-and-fro motion and divided up time into equal units.

1. The pallet-lever gives an impulse to the balance to make it perform one rotation: the TICK sound.

2. During this rotation, the balance-spring is compressed, thereby balancing the energy distributed

3. Then the balance-spring uncoils and forces the balance to swing back : the TOCK sound

4. The to-and-fro principle is achieved, corresponding to an oscillation5. A new impulse is then given by the pallet-lever

An oscillation is composed of 2 vibrations.

Frequency is the number of oscillations in one second. This term is often used to describe a watch calibre and is expressed in vibrations per hour: (click on the links below to listen)

• A frequency of 2.5 Hertz is equivalent to 18,000 vibrations per hour (meaning 5 vibrations per second)

• A frequency of 3 Hertz is equivalent to 21,600 vibrations per hour• A frequency of 4 Hertz is equivalent to 28,800 vibrations per hour• A frequency of 5 Hertz is equivalent to 36,000 vibrations per hour (meaning

10 vibrations per second)The energy thus regulated is transmitted to the hands by a set of wheels.

---------------------------------------------------All together,