Caliber AR-01

The Caliber AR-01 is a heavily reworked seagull ST-19, modified to work as a monopusher. The modification at Arcus involves swapping out the 3 parts marked in red for in-house manufactured parts. From the left these are the pivoted detent, the column wheel, and the chronograph second brake.

Although the monopusher modification is indeed unique, making and putting in 3 parts is by no means enough of a reason to justify the price tag of our watch. While the standard movement is excellent, compared to its more expensive counterparts the chronograph actuating mechanism is quite a bit stiffer. As a result, during development of of modification, our primary focus was to improve the ST-19 user experience.

Starting with just the unmodified mechanism, two main adjustments are made to eliminate the bulk of the excess force required to start the chronograph:

1)We remove the paint below the screw head of the screw that attaches the column wheel (marked in green) where the two come into contact. Aesthetically, no changes are noticeable, but the difference in force required to press the pusher is night and day as a result of the extra breathing room.

2) We readjust the spring marked with the yellow arrow which is responsible for making sure the column wheel rotates an equal angle with each push of the actuating button. Although a small adjustment, the spring then applies slightly less force at the contact point (orange arrow). This reduces the friction between the two, while maintaining its function.

These adjustments made things noticeably better, but we still weren't satisfied. From the moment we had a working geometry for the monopsuher, the parts underwent another 6 geometric iterations to make the chronograph operation as smooth as possible, while maintaining a distinct "click" with each actuation.

Although the ST-19 may be found in cheaper watches and does what it does well, with a watch this unique we wanted to make the movement equally special. All the watches we deliver will be individually hand adjusted as outlined above. While the Seagull perhaps lacks the level of decoration of its more expensive counterparts, we guarantee that mechanically it'll put up an excellent fight! Check out the animation below to see the chronograph in action.

To learn more about the common problems of this movement and how we rectify them, check out the this article about the ST-19. For more info on our quality control procedures please see the warranty page. To see our watches that are powered by this movement click here.