[For IWC Geeks] Caliber 89000 Series / Caliber 69000 Series. Studying IWC Chronograph Movements

Currently, IWC's chronograph models are equipped with the in-house manufactured movements Cal. 89000 series and Cal. 69000 series. Looking at the design of these two movements, you can see the unique and solid development approach of the brand.

Cal.89000 series

　The spread of compact automatic winding mechanisms and vertical clutches has given mechanical chronographs greater design freedom. However, there are also chronographs that use the classic swing-pinion clutch and an improved Pellaton automatic winding mechanism, while also successfully incorporating a flyback mechanism and a coaxial counter. This is IWC's Caliber 89000 series.

Addition of a flyback mechanism

　Flyback allows the chronograph to be reset without stopping it when it is running. If you want to make a flyback function usable, you need to allocate as much space as possible to the flyback mechanism. This is because if you can secure space, you can strengthen the reset mechanism, including the reset hammer. This is why the UROFA 59, released in 1941, had a diameter of 34 mm, which was large for the time.

　Nowadays, thanks to the compact vertical clutch and automatic winding mechanism, it is not difficult to incorporate a flyback mechanism. However, IWC's Cal. 89000 series takes a completely different approach to allocating space for a flyback mechanism.

　In almost all watches, the crown wheel and ratchet wheel (barrel) are next to each other, which makes it difficult to maneuver the chronograph mechanism. In contrast, the 89000 series separates these two and connects them with a ring-shaped intermediate wheel placed on top of the bridge. This creates a huge space in the center of the movement, where IWC has placed sturdy levers and a reset hammer that can withstand flyback. The extra space also reduces bending of parts. As a result, not only is durability increased, but manufacturing costs are likely to be reduced.

　The consideration to saving space can also be seen in the clutch mechanism. IWC deliberately chose a swing pinion, a compact horizontal clutch used in the ETA7750. The clutch mechanism has less inertia than a carrying arm, making it suitable for a flyback mechanism. In addition, the minute and hour counters, which are usually separated, have been combined into one and placed at 12 o'clock. This increases the vertical thickness, but makes the watch more compact horizontally. As a result, there is more space for the chronograph levers and reset hammer. IWC's designers have optimized every aspect of the design for the flyback mechanism.

　The swing pinion has a thin pinion that fits onto the fourth wheel, which rotates once per minute, and then touches the chronograph wheel at the center. Although it saves space, it has weaknesses in that the hands are prone to jumping and the balance wheel swing angle is prone to drop. In response, IWC has shaped the teeth of the swing pinion at an angle, making it less likely for the hands to jump. Furthermore, Stefan Ihnen, who was involved in the design, said, "When fully wound, the balance wheel swing angle is 310 degrees, and even when the chronograph is running, it only drops by 10 degrees." In other words, IWC has eliminated the weaknesses of the swing pinion.

Coaxial integrator also included

　What's interesting is the coaxial 60-minute and 12-hour counters. The counters are driven by gears that mesh directly with the barrel. However, as is typical of modern chronographs, the counter mechanism is located on the movement side rather than the dial side. The clutch is a friction wheel type, which can be described as a simple vertical clutch. It forcibly stops the chronograph when it is not in operation. Although there is resistance when the chronograph is not in operation, it is judged that this does not affect performance because the barrel, which has a high torque, is the power source.

　The 89000 series is a watch that specializes in flyback movement. Of course, all modern flyback chronographs are reliable and easy to use. However, this movement stands out in that it was designed to ensure this. The deliberately heavy pushers are also a good example of IWC's emphasis on practicality.

Cal.69000 series

　The Caliber 79000 series of automatic chronographs has long been IWC's workhorse. This fully tuned ETA7750 is a masterpiece comparable to Breitling's Caliber 13. Its successor is the in-house Caliber 69000 series. While an industrial movement, it stands out for its IWC-like attention to detail.

　Like the Caliber 89000 series, the Caliber 69000 series also uses a swing pinion clutch. This is the successor to the Caliber 79000 series, which was an improved version of the ETA 7750, and was designed by IWC.

　The 69000 series has a small seconds hand at 6 o'clock. A horizontally moving swing pinion is engaged with this to turn the central chronograph wheel. Rolex's Caliber 4130, which has a similar layout, has a vertical clutch between the fourth wheel and the chronograph wheel, but IWC has chosen a more orthodox approach. The Portugieser Chronograph equipped with the 79000 series also had a seconds hand at 6 o'clock, but this was simply moved to a different location on the dial side module.

　Chronographs with vertical clutches generally have the fourth wheel in the center, not the second wheel. In contrast, the 69000 series, like a classic chronograph, has the second wheel in the center. This means there is no jumping when setting the hands, and the feel is very smooth.

　What's interesting is the design of the 12-hour counter. Chronographs with compact vertical clutches all have the 12-hour counter on the movement side. While the 69000 series has a horizontal clutch, the 12-hour counter is on the movement side. Stefan Ihnen, who was involved in the design, explains that this is "to improve maintainability."

　The 69000 series employs a robust mechanism that improves productivity and maintainability. This is, after all, IWC's basic movement. However, the excellence of its design and manufacturing is evident in the smooth operation of the crown and pushers. I highly praise this movement.