A watch tells time by using a spring and a wheel. The spring gives energy to the wheel, and the wheel turns back and forth. The wheel makes a tick sound every time it turns. The watch counts the ticks and moves the hands on the dial.

But the spring does not give the same amount of energy all the time. It gives more energy when it is new and less energy when it is old. This makes the wheel turn faster or slower, and the watch tells time wrong.

Watchmakers have tried to solve this problem for a long time. They have made different devices to make the spring give the same amount of energy all the time. These devices are called constant force mechanisms, and they have a long and interesting story.

The First Devices: Fusee and Stackfreed

The first constant force mechanism was the fusee, which was made in the 1400s. The fusee is a cone-shaped wheel that has a chain or a rope around it. The chain or the rope connects the spring and the wheel. The fusee has a spiral groove on its side, which makes the chain or the rope move up and down as it turns. The fusee changes the speed of the wheel by changing the length of the chain or the rope. When the spring is new, the chain or the rope is short, and the wheel turns slow. When the spring is old, the chain or the rope is long, and the wheel turns fast.

The fusee was used in many watches and clocks until the 1800s. Some modern watches still use it as a way to show old watchmaking skills, like [the Zenith Academy Christophe Colomb Hurricane]. But the fusee has some problems, like being big, complicated, and wasteful.

Another old constant force mechanism was the stackfreed, which was made in Germany in the 1500s. The stackfreed is a spring-loaded piece that pushes against a stick that is attached to the spring’s axle. The piece has an odd shape, which makes it push harder or softer as it turns. The stackfreed slows down the spring by pushing harder when it is new and softer when it is old.

The stackfreed was only used in German watches until the 1600s. Other watchmakers did not like it because it used too much energy, made the watch heavy, and wore out quickly.

The Remontoire:

A Small Spring Another kind of constant force mechanism is the remontoire, which means “rewinding” in French. The remontoire is a small spring that gets energy from the big spring and gives energy to the wheel. The remontoire can be put in different places in the watch, like the spring, the center wheel, the third wheel, or the escape wheel. The remontoire usually has a tiny spiral spring that is wound by a wheel with a pin or a hook. The wheel spins with the watch and catches the pin or the hook every few seconds or minutes, depending on how it is made. This makes the spring tight and also stops the wheel from spinning more until the next time. The spring then loosens and gives a steady energy to the wheel until it is tight again.  The remontoire was made in the 1500s and was improved by many watchmakers over the years, like Robert Robin, John Harrison, and Abraham-Louis Breguet. The remontoire was used in some very good clocks and watches of their time, like [the sea clocks of Harrison] and [Breguet], and [the Strasbourg Cathedral clock]. The remontoire is still used in some new watches as a special feature, like [the Lange 31], [the F.P. Journe Tourbillon Souverain], and [the IWC Portugieser Constant-Force Tourbillon].

 

The New Solutions: The Constant Force Escapement and The Co-Axial Escapement

In the 1900s, watchmakers made new ways to get constant force in watchmaking, using new materials and shapes. One of these ways is not a constant force mechanism, but a part of the watch that gives energy to the wheel and makes it turn at equal times. This part is called an escapement.

One of the best examples of an escapement that works like a constant force mechanism is [the Girard-Perregaux Constant Escapement L.M.], which came out in 2013 and won the best prize at a big watch show. This watch has a new escapement that uses a thin piece of silicon as a constant force spring. The piece is shaped like a long eight and is between two escape wheels. The piece bends and snaps from one side to another, giving a steady push to the wheel every time. The piece gets energy from the spring through a normal lever escapement, which acts as a helper. The good thing about this system is that it gives a steady energy right to the wheel, no matter how much energy the spring has.

Another new way to get constant force in watchmaking is not a constant force mechanism, but a different type of escapement that makes less rubbing and keeps a steady pressure in the escapement. This escapement is called the co-axial escapement, and it was made by George Daniels in 1974 and used by Omega in 1999. The co-axial escapement has three pieces and two wheels, which are on the same axis. The co-axial escapement makes less rubbing between the pieces and the wheels, which makes the watch work better and more right. The co-axial escapement also has a self-fixing part that keeps a steady pressure between the pieces and the wheels, which gives a steady push to the wheel.

The End

Constant force mechanisms are parts that try to give a steady or almost steady energy to the wheel of a watch, which is the part that tells time. Constant force mechanisms have a long and interesting story in watchmaking, and they show how smart and creative watchmakers are. Constant force mechanisms can make a watch tell time better, as well as look nicer and more complex. But constant force mechanisms are not very common in watchmaking, because they are hard to make, use, and keep. They also add more parts and weight to the watch, which can make it less reliable and lasting. So constant force mechanisms are usually only for expensive watches that show the skill and newness of watchmaking.

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