A. Lange & Söhne Lange 31
More Complicated than Meets the Eye

Peter Chong

Originally published on TimeZone in 2007.

A watch which runs at a constant rate for 31 whole days without winding? Impossible, say some…Can be done, says the incredible team at Lange. The result – the Lange 31. A very handsome watch, with a simple dial, but hiding an incredibly complex mechanism to crack the 31 day running train.

Not only does the watch run without being wound for 31 whole days, it does so with a constant amplitude… keeping 270 degrees on the balance wheel throughout.

Lange 31, Monats-Werk, A. Lange & Söhne Lange 31, Lange 31 Peter ChongLange 31, Monats-Werk, A. Lange & Söhne Lange 31, Lange 31 Peter Chong

Available only in platinum, and on a forecasted delivery date of 2009, this watch was revealed in a special Press Conference held in Dresden and Glashutte on March 15, 2007 – a date well chosen to demonstrate the incredible prowess of this watch – exactly 31 days to the start of the SIHH 07 in Geneva.

The watches shown were running, working timepieces, and all but one piece was not finished, and all are still subject to design and aestetic changes. The watch as it was presented is the final design, but one never knows.

The dial side of the Lange 31, shown below…a typically teutonic dial with Lange DNA. The nomenclature “monats-werk” indicates that the movement runs for a month.

Monats Werk, Lange 31, A. Lange & Söhne Lange 31, Lange 31 Peter Chong

This is a large watch, measuring some 46mm in diameter, and 15.8mm in height, it weighs an impressive 230g (about half a pound) in its platinum case.

I wore the watch over the duration of dinner – some 4 hours on my wrist – and when I had to return the watch to Tony de Haas at the Bulow Residenz bar, it was with some regret as the watch felt so natural and at home on my wrist. I don’t think the large dimensions of the watch are to be feared and, these days, might even be considered trendy.

Monats Werk, Lange 31 wrist, Lange 31 wrist shot, Lange 31 Peter Chong
A wrist shot on my 7.5-inches wrist and it sits very well

Monats Werk, Lange 31 wrist, Lange 31 wrist shot, Lange 31 Peter Chong
Another shot on a smaller wrist than mine; see that the watch sits quite nicely

But the reason for this large size is not due to trend, but for a more technical nature since the space required is to house the huge mainspring and the clever mechanism to tame the torque.

The watch is powered by 2 mainsprings, each 1.85m in length, and at max power providing 20 N-mm of torque. As a comparison, the twin barrels on the Lange 1 provides 5 N-mm of torque.

Lange 31 – Too Much Power?

Great power can be achieved by making more powerful mainsprings. Stacking two large mainsprings to achieve long power reserves is not only inelegant, but also presents its own problems. At 20 N-mm, the power from the mainspring driving the drive train would cause instant and extremely severe overbanking of the balance – there is just too much power for the balance to handle. If one makes the balance sufficiently strong to handle the power, it would be very large, and due to this, its inertia would cause it to consume the power from the mainspring quickly, and not able to last the intended design power reserve.

Further, a spring discharge is not provide constant torque, but one which obeys the laws of physics, and discharges according to a reverse s-curve like shown in the picture below. I will be using a series of photographs used in the presentation to explain the theory behind solving this problem. Please excluse the less than perfect pictures – but I think they capture the spirit of the presentation with Tony de Haas pointing and gesticulating, and shows the theory well:

Lange 31 constant torque, Lange Sohne constant torque, Lange 31 power reserve, constant torque Peter Chong

One possible to get as close to this theoretical constant discharge curve is to provide a weak spring which discharges completely at short intervals, but is capable of recharging after each discharge on its own. Next imagine the large mainspring barrels to power such a weak spring. This is the principle of a remontoir – a spring within the power train, which charges and discharges periodically by the power of the mainspring, and hence able to provide a more or less constant force to the escapement.

In the case of the Lange 31, this chosen interval is 10 seconds. I will explain why 10 seconds later.

Lange 31 constant torque, Lange Sohne constant torque, Lange 31 power reserve, constant torque Peter Chong

Such a spring would provide a discharge curve over the 10 seconds like so, and repeats itself every 10 seconds.

Lange 31 constant torque, Lange Sohne constant torque, Lange 31 power reserve, constant torque Peter Chong

The way Lange went about to solve the remontoir is both elegant and complex. The engineers devised a remontoir mounted between two fourth wheels stacked on top of each other, and connected only by the spring of the remontoir. The remointoir recharges once every 10 seconds.

As in a typical watch, the third wheel drives the pinon of fourth wheel directly which makes one revolution every minute. The Lange 31 has 2 fourth wheels. Each is stacked on top of each other and connected only by the remontoir spring in between them. Both are able to move independent of each other and only bound by the limits caused by this remontoir spring. Both fourth wheels makes one revolution every minute, except that a special escapement – the remontoir escapement causes the bottom one to be locked for 10s. It then is released and jumps in spurts once every 10 seconds, while the other fourth wheel moves like that on a normal watch.

The remontoir escapement shown in detail right below. The pinon of the remontoir escapement is driven by the third wheel, and in turn, it drives the lower fourth wheel. A special one toothed escape wheel mounted rigidly on the remontoir escapement pinon wheel receives an impulse once every 10 seconds and is unlocked. This allows power to be delivered once every 10 seconds from the third wheel to the pinon of the remontoir escapement, which then drives the lower fourth wheel. This causes the lower fourth wheel to advance and rewind the remontoir.

When the one toothed wheel is unlocked it releases the full power of the mainspring, and rapidly jumps half a revolution only to be locked by the other pallet. As it is jumps, its pinon drives the bottom fourth wheel which winds the remontoir connected to it. The speed of advance is the relative power difference between the mainspring and the remontoir spring…which is a huge mismatch in power, thus the power train jumps once every 10 seconds. One can observe this in the movement, and also in the minute hand which, being attached to the second wheel, is released once every 10 seconds, and jumps once every 10 second block.

The impulse to unlock the remontoir escapement is provided by the top fourth wheel, which, working on the power of the remontoir spring moves like a normal fourth wheel. It only operates within the small power band of the remontoir spring, imitating a constant force. Mounted rigidly on the top fourth wheel is a cam shaped like an equilateral triangle with three curved sides.

Around this cam is a specially designed lever with two ruby teeth in contact with the cam, and the other end which engages on the special one toothed remontoir escape wheel. This lever is pivotted outside the power train, and is able to move from side to side controlled by the rotating cam. At any one time, one of the two pallets on the lever is engaged with the one tooth wheel, and locks the escapement. But as the cam rotates, it causes the lever to move from side to side, and this action causes the pallet holding the one toothed wheel in place to unlock, and the other pallet to move into position to catch the tooth as it spins across to the other side. At this precise unlocking angle, the third wheel to deliver its power to the bottom fourth wheel. This phenomena is known as escaping in horology…the power of the mainspring is allowed to escape, in a controlled rate by the escapement mechanism. The power flows from the third to the lower fourth wheel, via the pinon of the remontoir escapement is used to reload the remontoir spring, and due to the great strength of the mainspring barrels, occurs almost instantaneously. However, this unleashing of power is short lived, as the cam would have moved into another position which then engages the other pallet of lever to lock the one toothed wheel. As the cam is 3 sided, it causes this to occur once every 10 seconds, and achieves the remontoir escapement.

The remontoir escapement is a complication which is as difficult to adjust and regulate as a tourbillon escapement, and hence the equivalent pricing strategy.

Lange 31 constant torque, Lange Sohne remontoir escapement, Lange 31 power reserve, remontoir escapement Peter Chong
Detail showing the remontoir escapement and the engaging lever and the cam

Lange 31 remontoir escapement, Lange Sohne remontoir escapement, Lange 31 power reserve, constant torque Peter Chong

Lange 31 remontoir escapement, Lange Sohne remontoir escapement, Lange 31 power reserve, constant torque Peter Chong

Lange 31 – The Key System

The remontoir spring is never fully depleted, and is pre-tensioned, this allows the watch to restart when it is stopped under the tension of the remontoir. A stop-clock mechanism is also fitted, to allow the watch to be stopped for precise time adjustment. Note that the movement is an unfinished movement which works perfectly, but without final finishing:

Lange 31 key, Lange 31 remontoir escapement, Lange key system, Lange 31 Peter Chong
Tony de Haas showing where on the movement the remontoir is located

Lange 31 key, Lange 31 remontoir escapement, Lange key system, Lange 31 Peter Chong

The mainspring is so powerful, that it presents another problem…winding it would be a chore…if the gearing of the crown is high, it would take a very long time to wind the watch. Using a ratchet wheel to keep the winding power similar to a Lange 1, it would need 150 turns to completely wind the mainspring. Not very practical. Or one could device a low gearing, and require a few turns. But the power to wind this crown would be impractical.

The Lange engineers came up with a twist to solve this…they chose a low gearing – only 31 turns required to fully the watch. A special key is designed with a large thumb crown to afford the leverage to wind it.

Like the rest of the Lange 31, there is more than meets the eye with this key. The design is complex because it incorporates a ratchet mechanism and torque limiter.

Lange 31 key, Lange 31 remontoir escapement, Lange key system, Lange 31 Peter Chong

The key is machined out of stainless steel, and like a typical Lange product, is beautifully finished. Two keys are provided.

Picture below shows the key next to the Lange 31. In the background is the Datograph, as a comparison of size.

Lange 31 key, Lange 31 remontoir escapement, Lange key system, Lange 31 Peter Chong

Lange 31 key, Lange 31 remontoir escapement, Lange key system, Lange 31 Peter Chong
Detail showing relative locations of the remontoir (A) and the key (B)

Lange 31 – Dial Design and Layout

Numerous dial layouts were tried out. Shown below are 3 discarded designs:

Lange 31 dial, Lange 31 dial design, Lange 31 Peter Chong

And finally arriving at the design proposed as the Lange 31:

Lange 31 dial, Lange 31 dial design, Lange 31 SIHH 2007

Lange 31 dial, Lange 31 dial design, Lange 31 SIHH 2007

Some more pictures:

Lange 31 dial, Lange 31 dial design, Lange 31 SIHH 2007
Movement view, showing final finishing with Glashutte Ribbing, and anglage on the bridges

Lange 31 dial, Lange 31 dial design, Lange 31 SIHH 2007

Lange 31 dial, Lange 31 dial design, Lange 31 SIHH 2007
Axel Bobe – movement designer, examining with great pleasure his creation

Lange 31 dial, Lange 31 dial design, Lange 31 SIHH 2007
Axel’s brother Tino (right) who was involved in the design concept, with Tony de Haas – Technical Director

Photos © Peter Chong for TimeZone

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My view of the A. Lange & Söhne 1815 Tourbillon

Peter Chong

11 February 2014

All of us here at the Lange Forum know that Lange Uhren is a very special manufacture, and every year, does not fail to impress with the ultra large watch at the entrance of their SIHH booth, but more importantly with the marvellous watches they unveil.

This year is no different. I have discussed their Terra Luna in a bit of detail in this earlier article, but now turn my attention to what must be the darling of all and sundry at the fair…their 1815 Tourbillon.

Almost everyone I turn to to ask what was the most interesting piece in the Lange SIHH 2014 collection picked the A. Lange & Söhne 1815 Tourbillon as their choice. No wonder, this watch is a curious blend of beauty and brawns. The aesthetic simplicity and beauty of the 1815 case and dial with the elegant hands, coupled with the tour de force engineering required not only for the construction of a tourbillon, but to stop and reset the seconds hand mounted coaxially to the tourbillon cage. A World Premiere.

The classical looks of the 1815 dial, with Arabic numerals, railroad minute track, and beutiful javelin styled hands. Looking very similar to the now iconic TOURBILLON Pour le Merite of 1994, the new watch is similar in size…both 39.5mm in diameter.

The big visual difference between the 1815 Tourbillon and the Tourbillon Pour le Merite is that the older, now iconic and classic watch has a seconds hand at 8 o’clock and a power reserve indicator at 4 o’clock.. The newer watch sports a cleaner and, perhaps more moden look.  Also, the opening on the dial to show the magnificent tourbillon is now a clean, simpler, circular opening as opposed to a complicated shaped opening in the original Pour le Merite. Inside, the mechanism is a different story. The original Pour le Merite is equipped with a fusee and chain mechanism. The new 1815 Tourbillon, caliber L102.1 is simpler in construction, but includes the world premiere stop seconds with zero reset mechanism.

The tourbillon started life as a device to improve accuracy by allowing the balance to move through all positions thereby equalizing the effects of gravity. However, the enigma is that until 2008, when Lange introduced the Cabaret Tourbillon, a watch equipped with a tourbillon escapement cannot be hacked to set the time precisely. This is because, typically the tourbillon cage is a fairly large system within the wheel train, and there is a risk that on stopping, the train might not have sufficient power to restart. There is also the worry that the starting up process after hacking, the escapement will be catchcing up to normal beat rate, hence compromising the accuracy of the watch.

But in 2008, Lange showed that this can be done with little sacrifice to accuracy. Since then, all Lange tourbillons introduced after had the stop seconds mechanism installed. So it is only natural that it was up to Lange again to show the next step forward for tourbillons by allowing the seconds hand, mounted coaxially with the tourbillon pinon to instantly reset to zero when the crown is pulled and the tourbillon stopped. This zero reset mechanism was debuted by Lange in 1997 with the Langematic Sax-0-mat.

A video on the link posted by Uncle Edwin earlier shows how this is achieved.

The movement is finished to the usual Lange standards…which means to a very high level.

The movement is hand wound, with a power reserve of 72 hours, and cased in either a rose gold or platinum (limited edition of 100 pieces) case 39.5mm diameter and 11.1mm height. The movement beats at 21,600 bph.

A magnificent piece from A. Lange & Söhne. How would you compare the new 1815 Tourbillon to the now highly sought after Tourbillon Pour le Merite?

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My take on the A. Lange & Söhne Terra Luna

Peter Chong

7 February 2014

In the buzz around the halls of the Palexpo where the SIHH is held, there are many who found the 1815 Tourbillon to be a candidate for Most Interesting. The watch is approachable in the simple 3 hand design. It also features the world premier of a zero reset of the seconds hand mounted on the axe of the stop second tourbillon, so that alone is grounds to be a candidate for the most impressive list. But I found the Richard Lange Perpetual Calendar “Terra Luna” to be more interesting.

A. Lange & Söhne Terra Luna

The Richard Lange Perpetual Calendar “Terra Luna” houses a totally new movement with perpetual calendar, the L096.1 is a 14 day power reserve and remontoir escapement, with a unique and beautiful way to present the progress of the moon across the firmament.

A. Lange & Söhne Terra Luna

As is typical of the Lange brand DNA, the movement is beautifully laid out, and nicely finished. The watch is very teutonic in feel, being rather large at 45.5mm diameter and 16.5mm thick.

A. Lange & Söhne Terra Luna

The time display on the main dial is regulator style, with the perpetual calendar indications in window cutouts. The trademark outsized date takes center stage.

A. Lange & Söhne Terra Luna

An arc cutout reveals the power reserve indication in days

A. Lange & Söhne Terra Luna

Pictured above, the bridge carrying the remontoir mechanism first seen on the Lange 31.

A. Lange & Söhne Terra Luna

The moonphase display is also totally interesting. The setting is a large disc with an artistic representation of the sky with gold stars set on a stunning blue disc, revolving around the earth. And the moon, also revolving around the earth shows the phases of the moon in its orbit.

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Significant chronographs: Lange 1815 Chronograph

Peter Chong

24 May 2013

This post is dedicated to my good friend Eddie Sng, whose watch is featured here today.

The 1815 Chronograph was introduced as perhaps a purer version of the iconic Lange Datograph. Simpler without the trademark outsized date, but as I said, purer because traditional chronographs typically do not feature a date display, except in complications with perpetual calendars.

The dial is pure, simple, and well…perfect.

Lange 1815 Chronograph

And the movement side, exactly the same as in the Datograph…as the date mechanism for the Datograph is just below the dial, the view from the rear crystal of the 1815 Chronograph is exactly the same…showing the magnificent chronograph works.

Lange 1815 Chronograph

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