A. Lange & Söhne Richard Lange Pour le Mérite

This watch is no longer a secret, but you are certainly many waiting and hoping to see it and know more !

As you already know, Amanico, Foversta and myself had the pleasure to attend a presentation of the new for 2009  A. Lange & Söhne Richard Lange Pour le Merite.

A. Lange & Söhne Richard Lange Pour le Merite in platinum with enamel dial

The duality of this watch is really fascinating. Its outer face is quite classical and sober and totally and efficiently hides the complex reality of its inner works. In fact some journalists from outside the horological press were surprised to be invited for the presentation of such a simple watch!

You can see below that our own Amanico and Foversta were a bit more convinced right from the start by the interest of the new born!

Amanico and Foversta at work

The name « Pour le Merite » is in itself a good reason to look further below the beautiful enamel dial of this watch. The "Ordre du Merite" was created in 1842 by the famous explorator Alexander von Humboldt to celebrate deserving scientists and artists. A. Lange & Söhne has chosen the name "Pour le Merite" for its uncommon complications and specially its fusee-and-chain transmission models, the new one being the third after the Tourbillon "Pour le Merite" and the Tourbograph.

Simple, simpler watch

The Richard Lange original model is now becoming a piece in a limited range of precision watches, reminding us the pocket chronometers of the past that Lange produced in very low numbers, around thirty pieces, and the inventor Richard Lange, older son of the original Lange company founder and creator of special alloys for balance springs.

The new Richard Lange "Pour le Merite" is the second chapter of the family, pushing even further the quest for precision of rate.

The second enamel dial modern Lange watch with the Anniversary model

To some extent a fusee-and-chain transmission could seem to be a rather simple and easy solution to fit in a watch, but you should remember that it is not a chain saw that you look at, but a 40.5mm large watch. Considering the 636 components of the chain alone, and adding the 279 other pieces of the completed calibre, that's 915 pieces assembled in a calibre measuring 31.6 mm by 6mm of thickness!

So there is first the complexity of the building, finish and assembly. Then you should not forget that precision is the objective and the use of a chain in itself is not enough but has to be integrated with several mechanisms to reach the goal.

The chain transmission

You can see below the fusee-and-chain and the barrel mechanism. The fusee is exploded in the left and the mainspring barrel is on the right.

The principle is simple, the implementation is another thing!

First the principle: the main spring wound inside the barrel powers the wheel train to the escapement. When the mainspring is fully wound the torque is maximum and this torque decreases as long as the main spring unwinds itself. If this main spring is geared directly to the wheel train, this decrease of torque means a decreasing amplitude of the balance and consequently a loss in precision.

To counter-effect this decrease of torque the fusee-and-chain mechanism offers an increasing lever effect when the main spring unwinds.

At full winding the chain is rolled around the fusee which is a stepped cone. When the main spring begins to unwind it pulls the chain from the fusee to roll it on the barrel.

At the beginning the torque of the main spring is maximum obviously and the chain is pulled from the thinner extremity of the cone, so the lever effect in minimum.

As long as the chain rolls itself on the barrel the torque of the main spring decreases but this decrease is compensated by the increasing of the lever effect  brought by the fact that the chain pulled is more and more pulled from the thicker extremity of the cone of the fusee, i.e. farther from the axis of the fusee!

Did you get it? 

The fusee-and-chain and barrel mechanism

Below you can see the calibre in the watch, with the barrel at 4:30, linked by the chain to the fusee at 1:30, then the wheel train at the center of the calibre and at 7:30 towards the escapement at 10!

This is the way followed by the energy to power the calibre, in this case hopefully with constant torque in the wheel train and consequently with constant amplitude of the balance.

Three quarter open plate for valid reasons

Obviously this fusee-and-chain principle needs the conception of other refinements to be effective when implemented.

Fascinating mechanics

The first trick has a security purpose. The specific construction of the fusee-and-chain transmission means that the chain is fixed on both extremities on the barrel on one side and on the fusee on the other side. If the chain is pulled to be rolled excessively on one side or the other of its course beyond what is scheduled, the tension on the opposite (un-rolling) side may result in a breaking of the chain. The risk is particularly to overwind the main spring and pull excessively on the chain attachment on the fusee.

The full winding locking lever

Consequently the winding process is stopped and blocked by a lever before over winding.

When the chain is rolled enough around the barrel, the chain arriving to the thinner extremity of the fusee pushes a cantilever towards the dial side (light brown above), whose lever itself pushes a blocking lever (blue) that rotates a blocking ratchet (in pink) inside the teeth of the ratchet wheel above the fusee.

The full blocking is completed by a little rivet fixed on the chain that is stopped by the lever and consequently further block the chain.

The same lever pictured from above

This mechanism avoiding over winding is not enough to understand the full complexity of the mechanical marvel!

Beauty outside beast inside

Again as precision is the aim, the range of action of the increasing lever effect of the chain-and-fusee transmission must be precisely opposed to the inverted torque curb of the barrel. For that matter the power reserve has been voluntarily limited to 36 hours, this power reserve being evaluated as the longest power reserve to achieve a satisfying result on the precision.

That results in a locking device that stops the watch when the 36 hours of power reserve have elapsed from full winding. So the power reserve wheel at noon below makes one turn in 36 hours. At the end of the 36 hours of power reserve one extremity of a blocking lever (light blue) falls inside a recess in the power reserve wheel (brown).

When the lever falls in that recess, its other extremity engages on the way of a finger fixed on the 4^th wheel arbour (brown at three). When the seconds hand arrives at 0 the rotating finger is blocked by the extremity of the blocking lever and the wheel train stops, the seconds hand remaining vertically at 0! Magic isn't it?  

The low winding locking device

So now you know that you can't overwind the mainspring. You know also that the power reserve is voluntarily limited at 36 hours.

The lever effect of the chain-and-fusee transmission is calculated so that the lever effect must compensate the decrease of torque during 36 hours.

Obviously the final touch is to adjust the 36 hours working range of the main spring when its torque is regularly decreasing so that it matches the counter effect of the chain-and –fusee. This adjustment can be made through a pretensioning ratchet located on top of the barrel.

This can be done by a watchmaker with a Lange proprietary tool and the setting is locked then with a pawl. The mechanism located above the three-quarter plate is easily accessible.

Adjustment of the working range

In the drawing above the ideal 36 hours range is in grey (line) and must be positioned between the green and red ranges, so that the lever effect can counter perfectly the decrease of torque (grey curb).

Lange calibre L044.1

So the apparently simple calibre L044.1 above is indeed a beast of chronometry, made for precision!

Brushed platinum

The watch remains perfectly wearable, very close to the volume of the "standard" Richard Lange.

White and pink

There is one final interesting technical aspect inside the watch.

As the winding is made through the fusee (we've seen that the ratchet wheel is on the fusee), the fusee-and-chain construction needs a planetary gearing inside the fusee so that the drive wheel (that transmits the energy to the wheel train) on top of the dial side of the fusee can turn in one direction while the ratchet wheel turns in the opposite direction on the other side of the fusee when the watch is being wound.

Without this planetary gearing the watch would stop while being wound and that would not be ideal to maintain a long term precision, to say the least.

Three level enamel dial

I could say also that the enamel dial is made in three different pieces so that it is three dimensional, having three different plans! Obviously these three pieces have to be made together to get the same colour.

Maybe the first modern pink gold Lange with three blued hands

The picture below will show you on the upper right corner the pretensioning ratchet on the barrel that allows to adjust the 36 hours range to get the best effect of the chain-and-fusee mechanism.

Coveted German silver

On the balance side I can add that the balance spring is made in-house by Lange like for the original Richard Lange and the balance is free-sprung. The escapement oscillates at 21.600vph.  The inertia of the balance is chosen to match the constant torque delivered by the fusee-and-chain transmission.

Perfect on the wrist

I hope you enjoyed this reading and followed me so long!

A milestone in simplicity

That's a promising 2009 that comes with this Richard Lange "Pour le Merite" !

Dje