Hoberman sphere
From Wikipedia, the free encyclopedia
A Hoberman sphere is a structure that resembles a geodesic dome, but is capable of folding down to a fraction of its normal size by the scissor-like action of its joints. Colorful plastic versions have become popular as a child's toy: several toy sizes exist, with the original design capable of expanding from 15 cm (6 inches) in diameter to 76 cm (30 inches).
A Hoberman sphere is not a true sphere, but a polyhedron known as an icosidodecahedron. The Hoberman sphere can be unfolded by allowing certain members to spread apart. This can be accomplished by feeding out a string or cable in the larger models. The operation of each joint is linked to all the others in a manner conceptually similar to the extension arm on a wall-mounted shaving mirror.
The largest existing Hoberman sphere is in the atrium of Liberty Science Center in Jersey City, New Jersey. Fully expanded, it is 5.5 m (18 feet) in diameter. The motorized sphere weighs 318 kg (700 pounds), is constructed of stainless steel and aluminium, and continually oscillates between its compact and expanded states.
Its inventor, Chuck Hoberman, holds several patents on folding techniques, many of which resemble the designs of Buckminster Fuller but for the folding aspect.
