A Hoberman sphere is a kinetic structure patented by
Chuck Hoberman that resembles a
geodesic dome
A geodesic dome is a hemispherical thin-shell structure (lattice-shell) based on a geodesic polyhedron. The rigid triangular elements of the dome distribute stress throughout the structure, making geodesic domes able to withstand very heavy ...
, 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 children's toys: several toy sizes exist, with the original design capable of expanding from in diameter to .
Description
A Hoberman sphere typically consists of six
great circle
In mathematics, a great circle or orthodrome is the circular intersection of a sphere and a plane passing through the sphere's center point.
Discussion
Any arc of a great circle is a geodesic of the sphere, so that great circles in spher ...
s corresponding to the edges of an
icosidodecahedron
In geometry, an icosidodecahedron or pentagonal gyrobirotunda is a polyhedron with twenty (''icosi-'') triangular faces and twelve (''dodeca-'') pentagonal faces. An icosidodecahedron has 30 identical Vertex (geometry), vertices, with two triang ...
. The Hoberman sphere can be unfolded by allowing certain members to spread apart. The operation of each joint is linked to all the others in a
scissors mechanism like those used to mount
pantograph
A pantograph (, from their original use for copying writing) is a Linkage (mechanical), mechanical linkage connected in a manner based on parallelograms so that the movement of one pen, in tracing an image, produces identical movements in a se ...
mirrors, or how a
folding chair operates. In larger models, this can be accomplished by feeding out a string or cable instead.
The largest existing Hoberman sphere is in the
AHHAA Science Center in
Tartu, Estonia. Fully expanded, it is in diameter. The motorized sphere weighs , is constructed of aircraft-grade aluminum, and continually oscillates between its compact and expanded states. The sphere is suspended above the center's Science Court and is actuated with a computer-based motion control system. This system opens and closes the sphere in a programmed series of lyrical motions choreographed to music, lighting and special effects.
An earlier, similar but slightly smaller Hoberman sphere is in the atrium of
Liberty Science Center
Liberty Science Center is an interactive science museum and learning center located in Liberty State Park in Jersey City, New Jersey, Jersey City, New Jersey, United States. At its opening, it was the largest such planetarium in the Western H ...
in
. The sphere, when fully expanded, measures in diameter.
In 1993 a smaller geodesic sphere was installed at the
Swiss Science Center Technorama in Winterthur, Switzerland.
See also
*
Hoberman mechanism
References
{{Reflist
Further reading
* Greg Lynn (2014), ''Expanding sphere'', Canadian Centre for Architecture
External links
Hoberman Associates - Transformable Design"Radial expansion/retraction truss structures" Google Patents
Google Patents is a search engine from Google that indexes patents and patent applications.
Contents
Google Patents indexes more than 87 million patents and patent applications with full text from 17 patent offices, including:
* United States P ...
how to make a K'nex Hoberman sphereHow to make a popsicle Hoberman sphere
Linkages (mechanical)
Polyhedra
Educational toys