The dual-hinged doors on Tesla Model X is like a modern day sophisticated gullwing. For engineering enthusiasts, the Falcon Wing (what Tesla name it) door is indeed something to be appreciated.
I believe the Falcon doors are designed that way for easy access and to avoid the edge of the Model X's door from hitting another car or a wall at the car park for example.
If you've ever wondered how the mechanism of the Falcon Wing doors look and work, here's a demonstration video complete with the greatest children's (and adults', admit it) toys ever: Legos!
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The Tesla Model X's Falcon Wing doors might see questionable reliability, but it's just hard to argue that the dual-hinged mechanism is pretty neat. They're cool not just because they are functionally sexy, but mostly due to the geeky engineering that goes well into its design.
Here's a video from a Youtuber, a member of Tesla Motors Club and Model 3 Owners Club showing how the X's doors work:
Trev Page explains there are two hinges on each of the Falcon Wings doors; one at the door-body junction (A), and another one at the farther outboard (B).
At hinge A, there are two torsion springs each, which applies constant force to rotate the door upward and to open it. In addition, there's a pair of electric actuator (like a cylinder) to not only further help open the dor, but also to oppose the force from the torsion springs when closing the doors.
In another word, the actuators determine the direction of door movement, while the torsion springs are the 'helper' to counter the weight of the door.
Further outboard at hinge B, there are two pairs of electric actuators on each side; arranged in a way to tuck the outer liftgate in or open it out. Each pair of the actuators work opposing each other (can be seen when Trev pressing the Lego using his thumbs).
If watched closely on the actual car, the doors opening actually work its hinges A-B-A-B; the electric actuators at hinge A pushes the door open a bit, the actuators at hinge B tucks the door in until the inner hinge A have pushed the door all the way up, before hinge B pushes the liftgate fully.
So yeah, the doors are a stunning piece of engineering art.
