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 how it wasn't just built to either be fully open or fully closed. Instead, Apple has built it to offer different functions at many different angles.
According to testing done by HTX Studio on YouTube, 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 already said that its hinge contains almost 100 components. A CT scan of the hinge shows that this is concentrated in six sections, including two at the outer edges that are hinges connected to a central shaft.
Another section is a series of gears that are made so that rotating one side of the device also rotates the other. They stay in sync, they stay in lockstep, practically regardless of where you hold them.
Key to the design are two more sections immediately above and below the middle. These are a mix of springs and cams that either support or resist one another, depending on the angle of the screen.
"When the phone is fully open, the cams fit together, while the springs press against them to resist rotation, holding the foam until we apply enough force to fold it," says HTX Studio's video. "As we fold it, the cams compress the springs, which push back, and the resulting frictional torque overcomes the phone's own weight."
All of these sections are paired, with the same mechanical design at the top and bottom of the hinge. The final section is in the center, and seemingly features no moving parts.
Instead, it's the space through which flex cables connecting the two sides of the iPhone Duo can pass uninterrupted.
Avoiding the crease
It's already been demonstrated by Apple that the iPhone Duo screen hides the crease in part through the ten layers of glass on the display. Plus it has a nanotexture display where all other foldables have glossy ones, meaning they practically highlight the crease in comparison.
But beyond that, this new CT scan also reveals the details of one hinge element where Apple does much the same as its rivals.
The top and bottom of the iPhone Duo hinge are mirror images of each other - image credit HTX Studio.
It's called the bending space and represents what radius the curved screen goes to.
"Think of the screen as a sheet of paper," says the video. "Fold it in half with a wide curve, and there won't be much of a crease when you open it, but press it flat with no room to bend, and you will get a very clear crease."
On the iPhone Duo, this bending space is 3.85mm at its widest point. That lies between the 3.8mm and 4.2mm of other unspecified but typical foldables.
Strength and damage resistance
Apple has achieved an IP68 rating for dust resistance, which is rare for a foldable, but still no reason to throw yours down on a beach. Nonetheless, it is something few rivals can match.
Similarly, most rivals reportedly have the same two small bumps at top and bottom of the crease that are there to protect their hinges. If dropped, such foldables can disperse the jolt to the metal sides of the phone instead of into the screen.
Apple's iPhone Duo does not have this and instead, the screen gets to be perfectly smooth all over. It's also able to do this because the entire hinge assembly is encased in a titanium cover for extra strength.
Scratching the screen
The iPhone Duo can support an Apple Pencil, but doing so means writing on the device's surface with a fairly hard-tipped device. HTX Studio, though, tested out not only an Apple Pencil but also regular pencils from 6B to 8H hardness, and tried them in a rig pressing down with a force of 100g.
There was a faintly visible mark on the display with a 6H pencil, but it wasn't apparent to the touch. At 8H, there were much more visible and touchable scratches.
But reportedly this is better than many rival foldables.
The video goes into more detail about the design and components that the CT scan revealed. The YouTubers did this on a review model, and, separately, other reviewers have put theirs through more real-world tests.
