BB-8 onstage during Star Wars Celebration 2015 on April 16, 2015 in Anaheim, California.
Alberto E. Rodriguez—Getty Images
September 3, 2015 2:30 PM EDT

A pair of resourceful Star Wars fanatics have put forth a convincing theory on the inner workings of BB-8, the adorable droid set to make its film debut in The Force Awakens this holiday season.

The new droid, which will also be available as a $150 toy for franchise fans, has a head that can remain mostly stationary even as its spherical body is rolling madly to move it from place to place. The effect almost makes it look as if BB-8’s head can defy gravity.

Not so, say the pair of Spanish designers who started a website explaining how the machine works. The fans dug up a patent filed by Disney’s Imagineering group back in 2010 which appears to explain how the BB-8 functions. The patent describes a robot that uses omni wheels to allow its spherical body to roll in any direction, with each wheel being connected to a motor. Gyroscopes and acceleromoeters are used to determine the machine’s postioning. A base plate serves as a counterweight, helping the robot maintain a low center of gravity.

A mast running vertically through the sphere is the key to BB-8’s “floating head” appearance. The fan mockup of BB-8’s internals show the most connecting to the head via a rotation motor that lets the head spin independently of the robot’s spherical body. A flexible joint lower down on the mast allows for additional maneuverability. A separate mockup with less basis in Disney’s patent uses a stool design as the head’s base instead of mast. A magnetic rail shaped like a semicircle sits atop the stool, allowing the head to roll forward and backward separately from the body’s movements.

Eventually, the secrets of the BB-8 will be revealed—at least of its toy version. Fans will be able to buy the gadget and break it down into parts starting Friday.

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