Hoberman mechanism

[1] Multiple of these linkages can be joined together at the ends of the angulated bars by more revolute joints, expanding radially to make circle shaped mechanisms.

The mechanism is a GAE (generalize angulated element) where the coupler curve is a radial straight line.

Chuck Hoberman, a fine arts graduate from Cooper Union, realized that his lack in knowledge of engineering was holding him back from creating the things he could picture in his head.

He later patented a system that uses two identical bent rods connected in the middle by a joint, which he called the Hoberman mechanism.

The Hoberman mechanism is made of two identical angulated rods joined together at their bends by one central revolute joint.

By pushing or pulling on any of the joints, the entire system moves and changes shape, gaining volume or folding into itself.

Because the two angulated rods that make up a Hoberman mechanism are identical, they have the same r1 and r2 values and thus the same coupler curve.

The toy is made of six full rings of Hoberman mechanisms that are all connected to each other so as one piece of it retracts or expands, the entirety of the structure follows.