Grand Seiko caliber 9R86

Caliber 9R86 is a self-winding movement with column-wheel chronograph and GMT function, based on Seiko's Spring Drive technology. A column wheel system is used to control the starting and stopping of the stopwatch. Its system ensures precise, error free control of the chronograph operation. The column wheel is designed to reduce stress on the clutch and lever, minimizing impact on the movement when the start/stop button is pushed. A vertical clutch system was created to prevent the second hand from jumping when the stopwatch START button is pressed. In the vertical clutch system, when the stopwatch START button is pressed, the start-stop lever opens, the fourth wheel and the clutch ring are engaged by the pushing force of the clutch spring, and the stopwatch begins to measure time. Achieving a level of stopwatch accuracy equivalent to the accuracy of the Spring Drive caliber itself would not have meant much if this accuracy were lost in the operation of the stopwatch. To minimize time measurement errors when the chronograph buttons are pressed, the operation of the buttons was made as precise as humanly possible. A two-step READY/START mode was adopted to ensure that the stopwatch operation would be error-free. It is the same mechanism as is used in Seiko’s hand held stopwatches for professional sports use. The chronograph enters READY mode when the push button is lightly pressed. A further press then starts the stopwatch.