On most watches when you pull out the crown the sliding pinion moves straight in to engage with the setting wheel, or it may swing in, but on an arc that transects the center of the setting wheel’s axis of rotation (red circle). This is a result of the engagement of the intermediate setting wheels. All of this has nothing to do with the 5-day power-reserve or double barrels. If, after setting the time, you turn back the crown a little (not enough to move the hand) before pushing the crown back in the hand will not jump. Oris has indicated that this is a result of design decisions made to accommodate the 5-day power reserve and the two barrels and that the hand jump can be avoided by turning the crown slightly backward before pushing in the crown. Fig 6 – Comparing the oscillating weight of the Oris Caliber 400 (bottom) with the ETA 2824 (top) The weight does have a larger diameter allowing it to achieve the same moment of inertia as a smaller weight using less mass, but this weight falls short. In an effort to reduce the height of the movement, it would appear that Oris has chosen a weight with limited mass around its perimeter. 1 If this is the case, why do so many brands spend the extra money on more complicated bidirectional winding systems? Clearly, there must be advantages to a bidirectional winding system. Plenty of watch brands and horological textbooks indicate that unidirectional systems are equally as efficient as bidirectional winding systems but they have the added advantage of being simpler and made up of fewer parts. First, this watch has a unidirectional winding system winding in one direction and idling or “free-wheeling” in the other direction. It seems that the automatic winding mechanism on this watch is not as efficient as it needs to be (based both on my tests and on the experiences of some other owners.) There are two key factors in the design which contribute to this. But why? Fig 5 – The oscillating weight mounted to the movement It is however enough to both maintain and add approximately an additional day of reserve to the watch (your results may vary depending upon your level of activity.) Having run down 48 hours, one day on the final test only wound up the watch enough for it to run for 95 hours after removing it from the final test. Unfortunately, the quality control test demonstrated that a day of standard motion is not enough to fully wind the watch. This is important because it means that any issues with power reserve are a result of insufficient winding. In fact, I fully wound the stand-alone movement and observed that it ran for 125 hours before coming to a stop so we know that the watch is capable of storing enough energy and operates with sufficient efficiency to deliver the full 5-day power reserve with a little left in the tank. When manually winding this watch it takes more than 100 turns of the crown to fully wind it up, where most watches would be fully wound with about 40 turns of the crown. Before addressing this I think it is important to note that it takes a lot to fully wind a double barrel (5-day power reserve) watch. This 7-day test brought to light one of the first complaints I have heard from individuals who have purchased this watch and that is that they don’t seem to get the full 5-day power reserve as advertised by Oris. Fig 4 – Arrow indicating how to let down the power Servicing these watches should be straight forward for any watchmaker. This watch requires both and is marked with an arrow indicating you must loosen the screw and another pointing to the button to release the spring tension. Most watches require you to either turn a screw or depress a button. Also, the double release for the winding stem (a feature exceedingly rare in watchmaking) is also well marked. The click is clearly labeled with an arrow. For example, with two barrels it can be more difficult than normal to figure out how to release the power stored by the mainsprings before servicing the watch. Anything that is out of the ordinary is clearly marked to aid the watchmaker in his service. The watch comes apart and goes together easily. Often brands don’t think about what will happen when the watch needs to be serviced, but in this case, it is apparent that the needs of the watchmaker were considered. From the watchmaker’s perspective, it even looks like they designed the caliber 400 with after-sales service in mind.
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