How we built the Pixel 10 Pro Fold's new gearless hinge

Google teams found themselves at a crossroads when developing the new Pixel 10 Pro Fold.

"We had to decide how big of a leap we wanted to make," says Sangsoo Park, an industrial designer who works on Pixel phones. "There's the safer path and there's the more aggressive path." The update from the first to the second-generation Pixel foldable had been significant, and there was some uncertainty about how big of a jump to make this time. "It was such a major engineering lift with that first upgrade, we could have easily just updated specs and cameras and done a color refresh," Claude Zellweger, who leads the Pixel industrial design team, agrees.

But that's not what happened. "We felt that if we're able to really progress and push our engineering capabilities, we should," Claude says. That's how we ended up with what Claude describes as the Pixel 10 Pro Fold's "aggressive dimensions," a better performing camera and more - including an all-new gearless hinge, which made much of the new Fold's build possible.

Going gearless for better specs

"The biggest change is that this is what we call a gearless hinge - which literally means it doesn't have any gears," Sangsoo says. "The team was interested in this new design because gears can cause issues over time for a hinge: They can be damaged and dust can get stuck between them over time, degrading the basic opening and closing experience that is critical on a foldable. A gearless hinge is more reliable - it will continue to work flawlessly over time," Sangsoo explains.

Industrial design, advanced architecture and product design teams all came together to develop the gearless hinge. Typical hinges have four gears with teeth that allow two halves of the device to rotate symmetrically as it opens and closes. The gearless hinge maintains this symmetrical motion using mechanical components called CAMs, which convert one type of motion to another. In this case, they're converting rotational to linear motion, which allows the hinge to save some space.

This was an engineering (or as some may say, hinge-a-neering) challenge, though: "Gears are straightforward," says Yongho Lim, who worked on the architecture of the new foldable. And going from the original, rotational motion to linear motion was not. We thought using spring-loaded CAMs on each half might work in place of the gears," he explains. "With the CAMs connected across the hinge, when either half of the device is opened, the other would be forced to follow!" We knew we were on the right path when we built the first prototypes and the two halves opened perfectly in sync." And more importantly, when it survived the drop test. "I've been working in this field for a long time and have seen thousands of drop tests," Yongho says. "But I still hold my breath every time a new design gets dropped for the first time!"

The new hinge survived - and allowed the team to keep the product as thin as possible. And since the internal architecture of the phone was completely rearranged, designers had the opportunity to "push" things a bit more, as Sangsoo puts it. For starters, it meant they could expand the display all the way to the hinge and reduce the border significantly. In fact, the Pixel 10 Pro Fold has the largest display on a foldable at 8 inches, plus a 6.4-inch outer display thanks to smaller bezels, which shrank in part after taking out the hinge's gears.

The new build also helped the team maximize something else they knew people cared about. "The number one user demand is always better battery," says Sangsoo. "The new inner setup meant there was space for a bigger - better - one: It has our biggest battery on a foldable device yet, and can last more than 30 hours."

Thinking "phone first" for look, feel and function

There were also the aesthetics of the gearless hinge to consider. "When we talk about the hinge, there's always a lot of conversation around material changes," says Brian Cutter, who's a CMF (color, materials and finish) designer for Pixel. "And one important thing that we want to do every year is keep the hinge polished." If it were matte, he says, it would just blend in - the polish elevates the phone, signaling it fits in with the rest of the pro Pixels. Teams discussed various material options before deciding on aluminum, the same as the phones themselves, which meant Brian's team could color match nicely and achieve a stunning polish.

Another aesthetic upgrade is the phone's diamond-cut chamfers (or edges) with metallic finish, a design choice that echoes fine jewelry and watches and reflects the rest of the pro-level Pixels as well. Which is the whole idea: "When you hold this device," Sangsoo says, "you feel like you're holding a regular, pro-level phone."

To accomplish that, design and engineering teams needed to get the weight and sizing right. The gearless hinge made this experimentation possible. Teams created 3D-printed and machine block models to try out different angles for the hinge and to tune the torque so they'd get it just right. That development led to, as Claude describes it, "dimensions that feel much like the phone you're familiar with, visually and also tactically." Since the gearless hinge protrudes from the phone's body less, it has better in-hand grip and feel - it's easier to hold. Opening and closing the 10 Pro Fold is also smoother while still "inspiring confidence," Sangsoo and Claude explain, so it feels sturdy.

Beyond look and feel, the Pixel 10 Pro Fold is like pro-level phones in other important ways. It's the only foldable on the market that's compatible with magnetic Qi2 charging systems: Chargers can automatically snap on the back of the device, just like they can with any other compatible phone. It's also the first foldable to achieve IP68 water and dust resistance rating, made possible because teams were able to eliminate the small spaces the old hinge's gears required. "You shouldn't have to give up the normal ways you use a phone to use a foldable," Sangsoo says.

The gearless hinge was a crucial part of making possible a bigger display, better battery and familiar-yet-iconic look and feel. "We wanted to make a phone that fits into people's lives today," Claude says. "And then give them more on top of that."

• Pixel