Independents

Testing Time: Explaining Greubel Forsey's EWT - Experimental Watch Technology.

Spot the difference?  Two 24 Second Incline tourbillons with different performances under the EWT.  Which one gave the optimal performance?

The problem is to know when to stop.  When are you finished, done, at the end of the process?  For inventive minds, there has to be a process so that you place boundaries, and you know when you are at that boundary.  The idea of an experiment is that you can control the conditions, so you know that if you change one element, while keeping all else constant, that the result you observe is down to the one element being changed, and that the experiment, if controlled in such a manner produces a result that can be repeated.  There is cause and observed and recorded effect.

Robert Greubel and Stephen Forsey set up the EWT for precisely these reasons.  To make sure that the idea they were working on had direction and causation, that the results could be traced and be repeated if necessary, and to ensure that the results at each stage were known for future work so as not to re-invent the same result.

The EWT therefore is experimentation on watch technology; just as the name describes.  There are basically two elements to it: a technical side and a procedural side.  What separates Greubel Forsey's EWT from other firms is the process side.  On the technical side, the aspects are much the same as most other firms.  However, unlike Patek's Research Program {NAME HERE}, or MJLC Extreme Lab, there is not the emphasis on new materials.  While new materials may yet prove to provide greater accuracy for a watch mechanism, GF believe there are still too many unknowns with the existing state of knowledge. New materials are still in an early stage of use in watch mechanisms and as real testing cannot be accelerated, it takes years and not weeks or months to truly evaluate such a new application. It is still too early to communicate concrete results but this area Greubel Forsey are interested in for future work.

For now, Greubel Forsey's initial approach has been to take what is known at the current time, and improve upon the tourbillon itself; to take the existing (proven) escapement and balance system and improve on these elements in the watch movement before starting something else.  That is not to say other mechanical elements in the watch will not come under experimentation.  For example, the fifth invention is a look at a rementoir type system to deliver a steady supply of power from the barrels to the escapement. 

What matters for the EWT is the procedural or process side.  What motivates Robert Greubel and Stephen Forsey is not that they set off with the goal of developing a new watch, but rather an idea, to see if it works, can the idea produce a quantified and measurable impact on the accuracy of the watch?  Some ideas produce results that never see the light of day.  However, research, for research sake, without necessarily having an end product or market driven goal is still worth undertaking.  You never know what you might find out along the way.  It is with this ethos in mind that an initial thought enters the Greubel Forsey EWT process.

Illustration by Example: The 24 Second Tourbillon Incline.

To understand the EWT as a process, the best approach is to take an idea and trace it from the start to the end.  In this instance, there is an end product: the Greubel-Forsey 24 Second Tourbillon Incline watch.  Following an idea until it is dropped would not be as interesting.  Further, the idea, and the results of the research may yet prove useful at a later stage, combined with a different idea.  Even the failed ideas have value, and it is that value (the intellectual capital) that Greubel Forsey is building for use at some possible future point.

The idea for the 24 Second Incline arose out of the research for the Double Tourbillon 30°.  To provide an experimental environment in which to develop the 3-dimensional 30 degree double tourbillon, a system had to be implemented to ensure that the results were both 'known' (that the direction of causation was known so that a change in one element increased the accuracy of timing in the watch), and that the results could be repeated and be reliable on one watch after another.  Think of it this way.  If you change two elements at the same time, you do not know which has had the effect, it could be positive, negative, or perhaps nothing at all.  You have a single equation with two unknowns; you cannot solve the equation.  The EWT provides a learning process, so along the way results can be distinguished between those that work and those that do not work. 

In 1999 (when Greubel Forsey) first started experimenting with 3 dimensional tourbillon designs, they concentrated on the degree of angle.  Everything else was kept constant.  The escapement, balance wheel, hair-spring assembly, which had a known performance in a single plane were all kept the same.  The idea being that in the single plane, placing the watch face up on a table (perhaps overnight), or in a safe, would result in a loss of performance as the beneficial effects from the tourbillon were no longer having any effect.  The single plane tourbillon would only be effective for a watch held at the vertical (such as a pocket watch on a stand).  The only element that was changed was the angle of rotation.  Through experimentation, Greubel Forsey found that a 30 degree angle was optimal for the Double Tourbillon 30° diameter with minimum height of movement; although this angle of rotation could be dropped to 25 degrees without any loss of performance.  The ability to keep the balance wheel perpetually moving through all 'planes' of rotation is accomplished by the outer 4 minute cage.

Observed here is the outer cage (4 minute duration) of the 30 degree, plus the inner cage at the angle (at 1 minute duration).

However, another question arose.  If you only had a single axis tourbillon, could you find a means of making it more accurate?  One way would be to incline the escapement and then make it rotate through the 'planes' of rotation faster, spending less time in any one position where the tourbillon no longer has any effect. 

Once the idea, or hypothesis, has been defined, a team is assembled, and the 3-D CAD drawings are started.  Once the 3-D CAD drawings and simulation models have been examined, life size prototypes are constructed.  At times, these can appear very crude, but technically provide a place to start in terms of conducting experiments.  The Greubel Forsey workshops have a number of old precision machining equipment that can be used to manufacture the prototypes without the necessity and cost of programming specialized CNC machines.

Speed!

Does increased speed of rotation actually improve timekeeping performance for the angled tourbillon watch?  Once the angle of rotation had been settled upon, the next objective was to find the optimum speed of rotation (assuming that one existed).  There had been previous watches with a speed of rotation for the tourbillon that was less than 60 seconds, but there was no evidence to suggest if someone had found an optimal rotation speed, and if they did, it would have been for the single plane tourbillon, and not one rotating at an angle of 25 degrees.

To ensure that the results with one prototype are not a fluke and to ensure that the results are consistent, several prototypes are constructed on the same design.  All prototypes are then run with the same settings and the results collated.

Phase I concerned speed; the optimal speed of rotation from what is known on the standard tourbillon escapement and cage design. Greubel Forsey took a 30 degree movement baseplate and gear train, and constructed a single tourbillon, at a 25 degree angle, and from the start point at a 60 second rotation, changed the gearing to increase the speed and measure timekeeping performance.

Described by Stephen Forsey as 'quite funky really', the first phase prototype was uniquely intended to be a functional testing platform resembling almost literally the modified tourbillon 'bolted' onto the mechanism.

Once it was established at what speed of rotation the accuracy of the watch was improved, the next question was what factors could improve the tourbillon still further?

One question that was an initially obvious was whether improved accuracy from the speed of rotation could be improved by altering the inertia from the symmetric 3 arm initial prototype cage. 

Inertia

Phase II was therefore concerned with cage weight and inertia.  There is a trade-off in physics; what you gain at one point has to be paid for at another.  Speed has a cost in terms of energy and force.  What is required is a cage that can counter balance the balance wheel, but also be light enough to rotate at the higher speed.  There are two elements to the inertia of the cage: the energy required to start the cage rotating, and the continued energy required to maintain the cage movement.  The lighter the cage, the less inertia, and the less energy that the tourbillon requires.

The initial prototype (pictured above) was the traditional three-armed cage.  Greubel-Forsey then started to experiment with different forms for the cage.  Initially, they settled on a four-pronged cage that was symmetric in a single line.  Stephen Forsey pointed out that the Phase II cage (pictured below) actually had a higher inertia than the original three-pronged cage.

The form of the 4 pillars in line cage was designed to allow improvements in mass as part of the EWT process.  Hence, this did nothing to diminish the timekeeping properties of the mechanism over a particular duration and Greubel Forsey even went so far as to complete a watch with a finished movement:

The time between cage developments was not wasted. Greubel Forsey used the working prototype to design new elements to the movement and create the aesthetics around the movement (the dial, the back of the watch).

As part of the EWT process, Greubel Forsey decided to continue testing to see if the cage inertia could be improved, and with it the accuracy of the watch.  Further tests showed performance could be improved by altering the design of the cage, and the cage material.  The testing confirmed the choice of a lighter metal: titanium, and a lighter three-pronged cage, only this time with an asymmetric alignment. 

Using the 4 pillar cage, Greubel Forsey then went about reducing the weight and tracking the performance in order to arrive at the optimum weight/inertia ratio. The cage started out at a weight of 0.56 grams, then 0.52 grams, and at progressively less weight until 0.32 grams.  Finally, the optimal weight for the cage was fixed at 0.39 grams ensuring a solid constructional rigidity with optimum lightness and performance.

Phase III forms of the 24 second tourbillon incline

Finally, with the new cage, and with the aesthetics of the watch design agreed, a Phase III movement was tested (including technical and aesthetic prototype watches) that would resemble the final watch as seen today.  While the watch development in the EWT can be broken down into Phases, they are not rigid constructs and the different Phases can merge into each other, while respecting the final goals.  In total, from the time that the idea was first settled upon, until the Phase III movement passed the EWT, was 3.5 years.

Proof Positive

Testing from the EWT shows that for the Double Tourbillon 30°, there is a compensation of errors due to earth's gravitational pull in all positions of the watch (and not only vertical as the single axis traditional flat tourbillon).  The improvements in performance, as tested, can be broken out in the following way. The maximum difference relative to the base mechanism of a manual-winding watch without a tourbillon is 10 seconds, 7 seconds with a classical single axis flat tourbillon, 4 seconds maximum difference between the standard 6 positions of a wristwatch for the Double Tourbillon 30°, 6 seconds for the Tourbillon 24Second Incline and 3 seconds for Quadruple Tourbillon a Differential.  The results are tested by experiment, and can be replicated.

Proof by Contradiction

The important facet of the EWT is that it gives, as far as possible, a controlled environment to test whether an idea, executed in a certain manner, does improve the timekeeping properties (of the mechanism being studied) What was changed in the 24 second incline was the angle of inclination and the speed of rotation.  The balance wheel and basic tourbillon mechanism remained the same.  There is no change of balance wheel, balance spring design or metal, no new materials for the escape wheel.  Why is this?  As stated before, if you change everything at once, you do not know which change may have brought about the improvements in the timekeeping of the watch.  If you change everything at once, some element may even have a counter effect, only it is not sufficient (so significant) to show against the other change(s) that have a positive effect.

The second condition of an experiment is that the results are replicable.  If you take the standard balance wheel, balance spring, escape wheel and escapement design, incline at 25 degrees and increase the speed of rotation to 24 seconds, (with a cage weight of 0.39 grams), you will achieve the same result each time.  Each watch produced will be more accurate and reliable as a result.  It is a sustainable and replicable technological improvement that does not rely on new materials or designs that have not stood the test of time!

Proof by contradiction: suppose not – suppose that a watch was delivered where a number of elements had been changed – how would you know which element had a positive effect, a negative effect, which elements were complementary, which were contradictory?  For a moment, think of the observatory class movements produced for the Observatory timing competitions in the 1940's and 1950's where everything in the movement could potentially be changed at once.  While the movement was shown as an Observatory winner you don't know where the true improvements came from.  This movement might have been a 'one-off', something that might not be replicable.  If this is not something that can be reproduced; it is not experimental, you do not know what the introduction of the new technologies have accomplished individually.  Under the EWT you isolate each element, test it for performance, and then combine the elements at the end, knowing which was giving the optimal performance. 

Testing also takes time!  Testing requires results that cannot be gleaned overnight.  Greubel Forsey as a watch manufacturer might have been in existence since 1999, but only recently have their inventions been introduced into watches for sale.  Each stage (or phase) within the EWT for a single invention takes time.  Each stage undergoes rigorous testing so that the result is certain.  The gestation period for any mechanism within the EWT is years, with a single alteration potentially taking months to test sufficiently.  It takes time to test using an experimental approach.  But this is the nature of the experimental watch technology (EWT).

Andrew H