In drawing #1 we get an overview of the split mechanism. The two gold-colored wheels are the seconds- and minute-recording wheels that can be stopped and started again while the main chronograph continues to function. The central seconds wheel has very fine and barely visible teeth at its perimeter, while the minute recording wheel has 30 coarser teeth because the double split has a 30-minute counter on the dial side. Also notice the cutaways and the light blue details. These details show the position and movement of the various parts when the split has been activated and has recorded an intermediate event, while the solid color details show the same parts while they are operating in synchronization with the main chronograph function. We will explore the individual components in much greater detail as we move along.
The Double Split requires two column wheels to operate the main chronograph functions and the split functions. At "A" is the main chronograph column wheel. Look closely because it is more of a crown that turns at precise increments, as desired, by each press of the main chronograph function buttons, thus starting, stopping, and reseting these functions. Now have a look to see that column wheel "B" is responding to the owner's requirement to stop and record a secondary event (the split recorder). These operations are the basic part of every split seconds chronograph.
Now we "split" from the ordinary and examine two very special features of the Double Split chronograph. In order to record two separate events – seconds and minutes each – there needs to be two chronograph seconds hands and two minute-recording hands. Rather than spread hands all over the dial in a cluttered array, A. Lange & Söhne has chosen very wisely to keep like-minded hands together in central locations.
To explain the first special feature, I’ll address the drawing above. There is the convenience of recording two events via this mechanism - one for the seconds and another for the minutes. At "A" is a hammer (shoe) and at "B" is a heart cam. These two components constitute a clutch system that engages and disengages the two separate recordings of events (we will examine this function in more detail in a few moments).
At "C" is a pipe (tube) that carries either a minute-recording hand or seconds-recording hand. Remember that there are two of these mechanical marvels in the watch. And "D" is a shaft that passes through the pipe and carries another corresponding hand.
