A YouTuber has taken a CT scan of the hinge on the iPhone Duo and uncovered both how it works and what its limitations are. One of the surprises at the iPhone Duo launch was that it wasn't built to be simply fully open or fully closed. Instead, Apple designed it to offer different functions at many different angles.
According to testing done by HTX Studio on YouTube, the iPhone Duo can stay open between 15 degrees and 145 degrees. If it's held below 15 degrees, magnets mean it will snap shut. Similarly, beyond 145 degrees, the screen will snap to fully open.
Apple has said its hinge contains almost 100 components. A CT scan shows these are concentrated in six sections. Two sit at the outer edges and connect to a central shaft. Another section is a series of gears that ensure rotating one side of the device also rotates the other, keeping both sides in lockstep regardless of where you hold it. Key to the design are two more sections above and below the middle, a mix of springs and cams that either support or resist one another depending on the screen's angle. When the phone is fully open, the cams fit together while the springs press against them to resist rotation. As it folds, the cams compress the springs, and the resulting friction overcomes the phone's own weight.
The final section sits in the center and appears to have no moving parts. It is the space through which the flex cables connecting the two sides of the iPhone Duo pass uninterrupted. The hinge also includes a bending space of 3.85mm at its widest point, slightly within the range of other foldables, which helps limit the visibility of the crease.
Source: AppleInsider · Summarized by HeadlinesBriefing