Here's something you don't usually see on a smartphone teardown: mechanical parts. Big ones!

The folding action of this Razr comprises a continuous geared hinge, a cat-head cam, two support plates, and a few springs.

Motorola's patents illustrate the way the cam and the support plates work together to protect the fragile OLED display. They provide support and hold it taut while the phone is open, then get out of the way to allow for a nice big radius (which helps to prevent a crease in the display from forming) when it shuts.

In X-ray closeups of the hinge area, you can see the continuous geared hinge as well as the springs embedded in each side of the frame.