In-depth: The Girard-Perregaux Constant Escapement Explained (Video)
by Kyle Stults on March 28, 2013
Pinit

Haute Horlogerie INNOVATION…

GIRARD PERREGAUX CONSTANT ESCAPEMENT WATCH Front

GIRARD-PERREGAUX CONSTANT ESCAPEMENT Si

As you likely saw earlier today, Girard-Perregaux unveiled a revolutionary new piece addressing a fundamental challenge of watchmaking, a concept known as “constant force”.  It innovates on this challenge with a completely new architecture and escapement design.  While not the first constant force escapement for sure, Girard-Perregaux notes that unlike other systems that devise a constant force averaged over time, this is a true constant force escapement.  The GP constant escapement is complex in most regards, though more easily understood when seen visually.  Turns out the first patent — for a 14 micron silicon blade (which you can see above)– was filed back in 2008.  So we know that this piece is has at least a five year timeline of effort behind it.  The effort looks to have been well worth it – one look is all you need to know that the Constant Escapement is something special.

A (Very) Brief Overview Escapements in General

Before diving into this amazing new constant force escapement, I think a bit of background would be helpful and also provide a basis for truly appreciating what GP has invented.  The regulating organ of any mechanical wristwatch is the escapement.  You most likely recognize it as this:

Lever Escapement

The escapement manages the energy received from the mainspring (housed inside a “barrel”) to drive the gear train and manage the rotation speed of the hands.  Frequency (speed of the beats) is important, as is regularity (that the beats are predictable and constant).  As shown above, the most common escapement system used today is the lever escapement.  It was invented by Englishman Thomas Mudge in the mid 1700’s but its modern form is more closely associated with the Swiss (Breguet et al.)

Another more recent innovation is the co-axial escapement, invented by the late George Daniels in the late 1970’sand now used in many if not most of Omega’s watches today.  The Daniels co-axial has been improved upon by Daniels protege Roger Smith.

The Daniels Co-Axial Escapement

Daniels Co-Axial Escapement

Many other forms of the escapement exist and have been tried, but these by far are the most common.

One issue with the lever escapement is that it distributes the energy receives from the barrel, energy that diminishes with time as the mainspring unwinds itself.  The theory of a constant force escapement is that the escapement distributes constant energy regardless of the amplitude (“state of wind”, if you will) of the mainspring.

Chain and fusee constant force mechanism

Chain and fusee constant force mechanism

And of course as I mentioned above there are the more complex, specific constant force mechanisms that have been in use for awhile now (e.g. chain and fusee, variations of which are used by Lange, Breguet, Zenith, Romain Gauthier, and others such as IWC (constant force tourbillon), and so on.  But none like this…

The Girard-Perregaux Constant Escapement

GIRARD-PERREGAUX Constant Escapement Marked

As you can see what Girard-Perregaux has done is invent an ingenious new escapement, unlike anything before it.  It is based largely on of a concept of instability known as buckling.  In the Constant Escapement, a blade of silicon just 14 microns thick — about 6 times thinner than a human hair — is employed as the accumulator of energy.

GIRARD-PERREGAUX CONSTANT ESCAPEMENT Blade Closeup

The blade is given energy from the barrel(s) such that it takes on a wave-like form, flexing nearly to a point of instability whereupon an impluse causes the silicon blade to “snap”, or buckle, transmitting it stored energy back to the balance wheel.  The energy transmitted in this snapping of the silicon blade is, you might have guess by now, constant.

The silicon blade is fixed within a beautifully symmetrical “butterfly wing” frame (escapement spring). Though the aesthetic reasons are perhaps secondary to the functional purpose of this silicon frame — it provides fixed points for the blade at each end and serves to ensure that the blade it buckles with the utmost precision and reliability — basically it helps ensures the integrity of the system.

schreyer_1300583

Suffice it to say that without silicon and other modern technology, this escapement would not be possible.

It all makes a lot of sense if you watch this video:

Speaking of barrels, the Constant Escapement is fed by two parallel-linked barrels, each drum with two springs stacked in series, thus four barrels in total (also patented by GP).

Barrel

There is a linear power reserve meter on the left side of the dial which marks the almost week-long power reserve.  On the upper part of the dial you can see the two barrels as they sit just below the small hour/minute dial.  Note also the three bridges — clearly modeled after Girard-Perregaux’s famous (and traditional) “three gold bridges”.  There is  one bridge for the balance and one each for each escape wheel.  Beautiful, beautiful, beautiful – in an avant-garde sort of way!

Girard-Perregaux Constant Escapement Bottom Dial Closeup

The escapement wheel — actually there are two — are unlike that of the traditional lever escapement.  They are made of pure nickel, and they have only three teeth.  A lever escapement wheel typically has fifteen teeth.  Here it is, shown with arbor and pinion (the small toothed wheel):

GP constant escapement escape wheel
The manually wound caliber is no thicker than 8mm and it beats at 3Hz (21,600 vph).  Though other frequencies are possible, says GP.

GP Constant Escapement Movement Sketch

The caseback also gives some very nice looks at the mechanics of it all:

GP Constant Escapement Caseback

***

As for the watch itself, it is housed in a 48mm white gold case, with a curved case band.  The escapement is of course given center stage, occupying the bottom portion of the dial.  On the upper, you have a small sub dial which displays hour and minutes (as I already noted above).  And of course the power reserve indicator just below and to the left of this.  There is also a red-tipped, center-set seconds hand.

The Constant Escapement will retail for around $100,000, I am told.

***

The great thing is that this pièce de résistance is only the first model in the Constant Escapement collection.  New aesthetics and even different materials for certain components are possible, according to Girard-Perregaux.  Also, although the escapement here is calibrated to beat at 3 Hz (21,600 vph), though other frequencies are possible, says Girard-Perregaux.  I’d suspect that now the the fundamentally new architecture is out there, watch enthusiasts might get treated to a new Constant Escapement model on an annual basis (fingers-crossed).  I can hardly wait.