Patek Philippe Spiromax

by Ron DeCorte

March, 2006

Most images may be clicked to view larger versions

It was about one year ago that Patek Philippe introduced their new calibre with a high tech silicon escape wheel. The idea behind the new escape wheel was to eliminate the need for oiling the pallet stones, a long standing scourge of the lever escapement. This year Patek has attacked another area of the watch escapement with yet another development from their Advanced Research department. The hair-spring, or “spiral” in French, has presented its own set of challenges from the beginning.

So what is a hair-spring and why is it so important? Let’s examine the beast in some detail.

In a mechanical watch the number of ticks per second, per hour, and per day are dictated by the hair spring and the balance wheel. The length, width, thickness, and strength of the hairspring, when attached to the balance wheel, forms an instrument-of-time in much the same manner as a fine violin is an instrument-of-music.

Early hair springs where made from carbon steel, highly susceptible to magnetism, oxidation (rust), and temperature. Over time hair spring materials have evolved to eliminate most of these problems, but not entirely. A spring that is totally non-magnetic, will not oxidize, not effected by temperature, and isochronous, has been a long time dream of watchmakers. Has the Patek Advanced Research team solved all the problems, time will tell.

An early verge hair spring was usually a simple affair, flat with only a few coils. As time progressed the number of coils increased when combined with the larger amplitude anchor escapement. 10 plus coils were now the standard for fine time keeping watches, but magnetism, oxidation, temperature, and isochronism remained problematic.

One clever solution to the isochronism problem was developed by A.L.Breguet more than 200 years ago. The outer coil was brought up and above the flat portion of the spring. This simple modification allowed the spring to breathe with less distortion and improved isochronism. One drawback to the “Breguet” hairspring was the increased amount of space it occupies within the watch, about 3 times more.

Metallurgical advances in the late 1800’s and early 1900’s brought about new hair spring materials that were almost impervious to oxidation, magnetism, and had very little temperature variation. It was these advances that spawned the mono-metallic balance wheel that we see exclusively in modern watches compared to the split bi-metallic balances of yesteryear.

Skipping ahead in time we now have nanotechnology, or simply put the ability to build components molecule by molecule in an extremely precise manner. Teaming with other like minded companies and technical universities Patek Philippe started its Advanced Research department several years ago in search of new horological improvements.

Before we go any further I suppose some are asking what is happening to the fine art of watchmaking, well I can’t answer that question for you. But before you make any conclusions I think we should keep in mind all the earlier developments that have advanced horology….

Technology takes time (excuse the pun). In 2005 we saw a new silicon escape wheel from the Patek Philippe Advanced Research team, and in 2006 they are introducing their new Spiromax hair spring.

And what exactly is the Spiromax? Well for one it is the first non-metallic hair spring intended for production. It is true that glass, and other non-metallic materials, have been used (experimentations) over the last couple centuries. But none of these experiments ever evolved into standing horological revolutions.

In the past all hair springs required a lot of time to construct, manipulate (form), and adjust for optimum performance (timekeeping). A collet was used to attach the spring to the balance staff, a stud was attached at the outer end to the balance cock, and the length and over coil demanded countless hours of people-power for final adjustment.

Here we see a Patek calibre fitted with the Spiromax. Patek has not assigned a reference number to this new calibre as of this writing. Note: the balance cock and pallet bridge are fabricated of rock crystal in order to facilitate viewing; this feature will not be used in the final production of watches. As this particular movement is a very early prototype, please excuse any minor imperfections in the Cote-de-Geneve.

The material used for the hair spring is silicon-based, but different from the silicon escape wheel introduced in 2005. The exact composition of the spring material is undisclosed at this time. There is no metal contained in its manufacture. Hence it is totally non-magnetic. According to Patek, they tested a number of mechanical watches that used a conventional modern hair spring (anti-magnetic) and found that 1/3 of them stopped functioning when exposed to high levels of magnetism while not one Spiromax watch failed. We live in a world full of magnetism and as a watchmaker I can attest to the influences it has on mechanical watches, especially the hair spring.

Another apparent advantage of the Spiromax is its mass, 2.4 g/cubic-cm as compared to 8.0 g/cubic-cm for a conventional modern spring, a reduction of 70%. The advantage of mass reduction is simple; the hair spring is far less influenced by gravity and shocks.

Image courtesy Patek Philippe

A Spiromax spring is formed as one-piece with the exception of the stud-clip, far left. Uniformity of the spring is exceptional from the collet (center) to the outer end. You will notice a thicker part near the end of the outer coil. This is Patek’s patented terminal curve that helps control the breathing of the spring (isochronism) and would be impossible with a conventional flat spring.

Image courtesy Patek Philippe

Due to the fact that the spring cannot be lengthened or shortened, as with a conventional spring, the manufacturing process must be extremely accurate.

The technology that makes the Spiromax possible is deep reactive ion etching (DRIE). “Deep” being the key word since until recently it would have been impossible to create a super precision mask given the extreme thinness of each coil as compared to the height. In basic terms this technology is the same used to manufacture computer chips; a mask representing the physical shape of the desired object is created on a wafer and then etched, and finally the mask is dissolved leaving the object behind. I suppose you could call the mask a mold since it dictates the physical shape of what is being fabricated.

Now that we have a basic idea of the fabrication technology lets have a close look at what may be the most important aspect of the Spiromax, isochronism.

The ability of the spring to expand and contract in a uniform manner as it is being wound and unwound by the balance wheel is critical to the time keeping. In the following photographs we will see the difference between a conventional spring and a Spiromax.

Above left we see a conventional spring and on the right a Spiromax. In these photographs both springs are at rest, or I guess we should say not under compression or expansion. Notice the uniformity (spacing) of the coils for both springs.

Now we see both springs under contraction. Notice the extreme disparity of coil spacing in the conventional spring, left at arrow, while the Spiromax remains uniform. Obviously the conventional spring is exerting a great deal of lateral pressure on the balance which is not conducive to accurate time keeping.

Here we see both springs at maximum expansion, and again we can notice the conventional spring has disparity of coil spacing (although not as extreme as earlier) while the Spiromax remains uniform.

(Note: the 6 photographs above where captured from a video made by Patek Philippe.)

OK, call me a cynic, but I asked Patek for a personal opportunity to see and photograph the Spiromax in action. They graciously agreed and the following photographs are what I observed…

On the left the Spiromax is under maximum compression, and on the right under maximum expansion, verifying excellent uniformity through the entire cycle of rotation.

In conclusion I’m very impressed with the Spiromax. It’s refreshing to see technological exploration for the advancement of horology, and Patek Philippe should be applauded for their efforts.

And what advantage(s) should we expect from the Spiromax? As a watchmaker I think the isochronal integrity of the Spiromax will be it’s greatest advantage by establishing what should be a new level of performance for mechanical watches. While it’s non-magnetic properties and reduced mass should not be ignored either since they will also be added attributes.

The most logical question I can pose at this time is, “what’s next?”

For those with an inquisitive mind you can see the Patek patent applications in .pdf format by clicking the images below:

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