Lange 31 - more complicated than meets the eye
by Peter Chong

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.
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(C) Peter Chong 2007
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.
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.

Here is a wrist shot, my wrist is 7.5 inches, and it sits very well. 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.
Another shot on a smaller wrist than mine...but see that the watch sits quite nicely. I don't think the large dimensions of the watch are to be feared...these days, might even be considered trendy.

But the reason for this large size is not due to trend...but for a more technical nature...the space required 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.