This is the third and final Lange post from an extended Lange afternoon in Melbourne recently. The first post was an overview of the brand’s arrival in Australia, the second about my favourite, the Zeitwerk, and this final post will be about the rather astonishing Lange 31.

One of the challenges in the design of a mechanical wristwatch is its power reserve – the challenge of storing and then ‘returning’ energy to the watch’s going train in a consistent and uniform way, not to mention how to get a decent power reserve. Especially in watches with a large power reserve, the torque of the often multiple mainsprings of greater dimensions may fluctuate considerably, negatively impacting on the rate accuracy.

A. Lange & Söhne decided to re-examine the power reserve, and came up with the Lange 31, the world’s first mechanical wristwatch with a power reserve of 31 days and a patented constant-force escapement that powers the going train with constant torque delivery. The amount of energy needed to keep the watch running for a month is transferred to the movement with a winding key and stored in a twin mainspring barrel.

The inscription “Monats-Werk” indicates the power reserve status.

The caseback reveals something not usually in wristwatches – a key winding mechanism that was designed for this watch. What a winding key allows is what is called a larger winding transmission ratio. This means that fewer ‘winds’ are required. How is this done? A key (which unfortunately we did not get the opportunity to see) is inserted through an aperture in the sapphire caseback.

Three seals between the winding mechanism and the case protect the watch against water up to 3 bars. To prevent accidental over tightening of the mainsprings, the key has a torque limiter, which means that any attempt to turn the key beyond the point where the mainspring is fully wound disengages the teeth of the wheels inside the key.

So what is inside to keep this watch running for 31 days? The Cal. L034.1 manufacture movement, which has a diameter of 37.3mm and a height of 9.6mm. The energy storage function is handled by the large twin mainspring which contain the two mainsprings, each of which is 1,850mm long, which is five to ten times as long as the springs of conventional mechanical wristwatches.

As far as ‘wow’ factors go, this Lange has it in spades. It has Lange’s renowned levels of finishing, but on top of that, the Lange 31 is almost a bit overwhelming when you see it for the first time. This is a large watch with a very large presence. It has a diameter of 45.9mm and is 15.8mm high. As if its physical size weren’t enough, it weighs 230g (about half a pound) in its platinum case (it is also available, as is in these photos, in pink gold). Why is it so large? Simply because it is necessary – a certain amount of space is required for the movement.

This is not a watch you’ll get many opportunities to see, so if the chance presents itself, grab it.

Categories: A. Lange & Söhne, German watches, Hands-on, Melbourne, Watch Profile, watches