Good evening everyone!
This column talks about mechanical watches from an engineer's point of view. This is the fourth in the series.
"What's the difference between a mainspring and a hairspring?"
I will be talking about this topic.
When I talk to customers at the store or on the phone, I sometimes wonder if there are a surprisingly large number of people who confuse "mainspring" and "hairspring."
Although these two have similar names, they are actually completely different things. Both play an important role in mechanical watches, so we hope you will take this opportunity to learn the difference between them.
About the mainspring
What is a mainspring?
*Mainspring
The power source of a mechanical watch is the mainspring. It is sometimes called the "main spring" to distinguish it from the "hairspring."
This has a slightly strange shape resembling a treble clef, but this shape was designed to minimize the difference in torque (rotational force) between when the spring is fully wound and when it unwinds.
* The spring and barrel core housed in the barrel
The mainspring is housed in a gear called a barrel, and when you wind the crown by hand or by using the movement of your arm (in an automatic watch), the kinetic energy is transmitted through the automatic winding mechanism, the ratchet wheel, and the barrel core to wind the watch.
* Mainspring, barrel and barrel core
When the spring is completely removed from the barrel, it is in a treble clef shape and measures over 10 centimetres, and when stretched out straight, its total length reaches over 1 meter.
The power of the wound spring then passes through mechanisms unique to mechanical watches, such as the gear train, escapement, and speed regulation, and unwinds little by little, continuing to move the hands of the clock accurately.
As you can probably tell by reading this far, a "spring" plays the same role as the springs that power mechanical toys that we imagine. They are wound up by hand, and when they unwind, they act as the source of power to move objects.
The Importance of the Mainspring
* Mainspring (left) and balance wheel assembly including hairspring (second from bottom center)
The power reserve of a mechanical watch is mainly determined by the length of the mainspring, and the longer the length, the longer the watch will run. Therefore, in order to extend the power reserve even a little, each manufacturer is trying to make the inner wall of the barrel as thin as possible so that they can install a long mainspring.
Also, at one time, there was active development of a movement called a "twin barrel" that has two barrels. The purpose of this is to increase the storage space for the "spring" that is the power source, thereby extending the running time, and some models have achieved an astonishing power reserve of about 8 days.
About the balance spring
What is a hairspring?
*Hairspring
The hairspring is one of the components that make up the balance wheel, which is the heart of a mechanical watch, and plays an important role in determining accuracy.
As the name suggests, it is made of metal as thin as a beard or a hair (it's interesting that it's called "hair" in English but is called "hige" in Japanese), and is beautifully shaped into a spiral. It's a little hard to tell from the photo, but it is a much smaller part than the mainspring, and in most cases its diameter is less than 1 cm.
* Hairspring attached to the balance
The photo above shows the complete balance wheel, known as a " regulator " in watchmaking terms.
If we compare the balance to a pendulum, the hairspring is the "pendulum string," and the hairspring expands and contracts repeatedly to allow the watch to keep accurate time. However, unlike a table clock, a wristwatch is not always placed in the same position; it can be turned sideways or upside down, and is exposed to changes in gravity. In addition, there is the constraint of having to fit various parts into an extremely limited space, which resulted in the development of such a delicate shape of the hairspring.
Although at first glance the hairspring looks like just a metal thread, its production is actually considered to be the most difficult part of watchmaking. This is because the hairspring is the most important part that determines the precision of a watch, and so it must be made with greater precision than any other part, and it must be manufactured without compromise in any aspect, from the molding process to the heat treatment process to the length adjustment.
Types of hairsprings
*Omega's own Si14 silicon balance spring
Previously, most Swiss mechanical movements used parts from Nivarox-Fah , a company that specializes in hairspring manufacturing. Over the past decade, however, there has been a sudden increase in brands developing and producing their own hairsprings.
Among them, I would like to briefly introduce two of the most common types of hairsprings.
1. Blue Parachrom hairspring
The "Parachrom Blue Hairspring" was developed by Rolex in 2005.
The Blue Parachrom hairspring is a unique bluish hairspring called "Parachrom" and is made of an alloy of Nb (niobium) and Hf (hafnium), and is characterized by its beautiful appearance.
It is also highly resistant to temperature changes and shocks, and has better antimagnetic properties than the Nivarox balance spring.
2. Silicon balance spring
*Rolex Syloxi hairspring
Currently, various watch brands are considering using silicon hairsprings as an important ingredient in the development of hairsprings, making this a "silicon hairspring."
Silicon has the most important properties for a hairspring: it is not affected by magnetic fields, it is lighter than metal, and it is resistant to deformation. It also has high resistance to corrosion and impact. This may sound like a material with many advantages for watches, but from an engineer's point of view, it also has the disadvantage that it does not require fine adjustments during assembly (which is not possible due to the characteristics of the material).
The Nivarox hairspring and Parachrom Blue hairspring mentioned above require fine adjustments by a technician, which is very delicate and affects the accuracy of the watch, so in a sense it was a test of the technician's skill. The fact that such adjustments are no longer necessary is a happy sign of "evolution," but it is also a little sad for technicians that they can be assembled without any special skills.
Rolex currently uses two types of hairsprings for each movement, Parachrom Bleu and Syloxi, but I believe that they will continue to coexist in the future, taking into account their respective suitabilities.
summary
Mainsprings and hairsprings have similar names, so it's easy to get confused, but do you understand the difference between them?
Each part plays an important role in a wristwatch, so if you can understand their differences and imagine how a mechanical watch works, I believe you will come to love mechanical watches even more.
We hope that this article has been useful to you and has piqued your interest in luxury watches! If you have any questions, please feel free to ask us directly, and we look forward to hearing from you!
Look forward to the next one! See you next time!