h a l f b a k e r y
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This is just a kit of hula hoops and clamps to make a big
The ball can be rolled around, jumped into, etc.
Fun at the beach or at the playing field. Covered in towels
makes a cubby house or sun shelter.
Someone will inevitably try and climb up the ball which will
eventually cause it
to collapse. Fun.
To use an icosahedron as an example, the kit comprises
20 hula hoops and 30 clamps.
The clamps have a hinge on one side and a locking
mechanism in the other side. When in the closed state the
clamp forms two adjacent cylindrical (or more correctly
toroidal segment) holes to fit a small portion (e.g. 5cm) of
two hula hoops. The inner surface of the clamps would be
made of an elastic material to conform to the hula hoop.
The outside of the clamp would also be covered in a soft
material so it doesn't hurt kids as they play.
To assemble, take a hula hoop and clamp three hula
hoops equally spaced around it. Fold hoops together at
the dihedral angle and clamp touching hula hoops. Repeat
until icosahedron is formed.
More advanced kits could have hula hoops of two (or
more) different sizes to made more complex polyhedra
(e.g. truncated dodecahedron).
Baked, even if not WKTE
Hula Hoop Geometry [a1, Nov 12 2021]
H type tube connector
[xaviergisz, Nov 12 2021]
What you're doing only smaller & one-piece-molded [neutrinos_shadow, Nov 15 2021]
[a1, Nov 15 2021]
I made it!
Truncated i-squash-ahedron [xaviergisz, Dec 06 2021]
||I like the idea of a 'geometric solids' construction kit but
using simple hula hoops and clamps is a really nice idea.
As you mentioned, you will need different sized hula
hoops to take the place of the pentagons and hexagons in
the truncated icosahedron, or the triangles and pentagons
in the icosadodecahedron
Edit to add: I found (link) showing others have already done
this. But the idea of a packaged kit still has merit. Enjoy the
||Billy! How many times do we have to tell you not
to lock your little brother inside the hulahehron?!
||+ That is nice. Please be sure to include picture
directions for me! I want mine in blue.
||Thought this might be a hulahoop with a circular inside ring but featuring a polygon disc on the outside edge. This would enable it be used as both a Hula Hoop and as a component to create a geodesic dome. (see Buckminster Fuller)
||That first link doesn't hardly bakes this at all:
1) They only made tetrahedra and a not quite Sierpinski
tetrahedron, not icosahedron or other large balls as described
2) It looks like they just used twisted pipe cleaners rather
than specially designed clamps to hold these together, leading
to the structural collapse shown in the last photo.
||One note about the design: If you create //(or more
correctly toroidal segment)// the angle between the
adjacent hula hoops will be fixed, so if a set of clamps is good
for an icosahedron they won't be quite right for a
dodecahedron. This shouldn't be too hard to resolve.
||I'm going to buy 60 H-type tube connectors (two for
each edge for added strength/stability) and 20 hula
hoops to test out the idea.
||[xaviergisz], nice! Please link photos of all 5 once you're done
& as [scadmientist] wrote, you want the connectors short (as
per the "H type") or hinged; not a fixed pair of large curves as
in the idea. A hinge doesn't need to be "locked"; the system
(once complete) will be stable even with "free" hinges
(although the hula hoops, being flexible, will allow some
movement, but then that's probably a good thing...).
||I've decided that an icosahedron is not going to be strong
enough, so I'll be making a truncated icosahedron. This will
require 32 hula hoops: 20 large and 12 smaller. I've found hula
hoops of 91cm and 71cm diameters, which I think is just about
||//not going to be strong enough//
Given that the hula hoops are (presumably) a little flexible,
more hoops means less strength/rigidity. A dodecahedron
would be your best bet (each hoop connected to 5 others).
Also, a truncated icosahedron (with the hoops you mention)
will be rather large...
||I would suggest cutting semi circles from the inside curves of outer hoops where they intersect inner hoops, like a spherical log house design.
This would let you attach them with a single bolt/lock washer/nut at each connection and the curvature of each cut will, while weakening the individual hoops themselves, lock the whole sphere into a much more rigid shape than if each hoop retained its full rigidity.
||//Given that the hula hoops are (presumably) a little
flexible, more hoops means less strength/rigidity.//
||Once I have the connectors and hoops I'll be able to
experiment to find the strongest structure.
||//Also, a truncated icosahedron (with the hoops you
mention) will be rather large...//
||Yep, about 2.4 meters high.
||If all goes well I'll try for even bigger structures. For
example a rhombic triacontahedron.
||Suggestion: find the right diameter/flexibility plastic pipe/rod
& make your own hoops. Then you can get exactly the sizes
||I might consider modifying hula hoops (by cutting out a small
segment and reattaching the ends) to get the size I want.
||If you wanted to do small mockups first, you could use crochet
rings (link). Cheap and available in several sizes. I know you're
keen on having good clamps, but for little table-top models you
could use twist-ties.