Hoberman Sphere (Truncated Icosahedron)

WARNING - CHOKING HAZARD! SMALL PARTS!

UPDATE There is an updated version of this model: https://www.printables.com/model/1123105-truncated-icosahedron-v20-hoberman-sphere

I have wanted a Hoberman sphere since forever.  Now, in this glorious age of 3D printing, I have made this a reality for myself - and you too!  

I may re-visit my ‘3 Ring Hoberman Sphere’ model (version 2.0 is in the works), but I think this looks much cooler.  I believe this is the only hand-held truncated icosahedron Hoberman sphere in existence (I've never seen one at least).

I wanted to make it as easy to assemble as possible - with no messing around with glue or melting pieces of filament for hinges - so I designed snap-together triangle joints, which can be put together with a pair of long needle-nosed pliers.

Be forewarned, this build takes patience and dexterity!  There are 600 individual parts!

In addition to the almost 70 hours print time, the longest labor will be removing the support material from the arms (360 of them), which took me about an hour.  I've made two of these so far, and I got really good at it.  I included a few extra parts in case you end up breaking some.

I printed the links in different colors, partly because it helps with assembly, and also 'cause it looks cool.

I recommend printing one batch of the two F_Links first, then the M-L_Links and M-R_Links.  Remove supports from these while printing the second batch of F-Links.  Then while you're printing the Triangle_Bases and the Triangle_Caps, assemble the 90 arms using TWO F-Links, ONE M-L link and ONE M-R link, as shown here.  Be careful, the pins and links can break!

THIS IS THE HARDEST PART.  This is my method:

1) Take an M-R_Link (red one in the picture) and lay it flat with the pins facing up.

2) Take an F_Link (purple in the picture) and position it over the pin (make sure the orientation is correct!) and press it into position on the head of the pin (LEVEL AND EVEN) using something flat like a small block of wood.

3) Position the tips of your needle-nosed pliers over the pin - EVENLY on either side of the F_Link hole - and press down evenly to snap it (*CLUNK*) onto the pin.

4) Repeat with the second F_Link (purple) as shown.  Note that the orientation is the reverse (upside down) of the first F_Link.

5) Position the M-L_Link (the blue one in the picture) so that its pins line up under the holes in the two F_Links.

6) Repeat step 3 for the inner pin/hole first, then the outer pin/hole.

7) Repeat steps 1 through 6 eighty-nine more times!

ASSEMBLING THE SPHERE

This is basically a soccer ball / football (truncated isocahedron), which has 12 pentagons (5 sides) and 20 hexagons (6 sides).  The thing that helped me in assembling is that the pentagons are never next to each other; each pentagon is surrounded by hexagons.  The arm assemblies are the edges of the sphere.

Each corner uses two Triangle_Bases/Caps - an inner one and an outer one - the outer triangle' cap is facing out, the inner triangle's cap is facing in.  

Start by taking 3 arm assemblies and placing the top pivot pins of each FULLY into a slot into a Triangle_Base.  Make sure that the Triangle_Base opening is facing up, while the arm assembly is curving downward - this will be the outer part of a corner.  Then take a Triangle_Cap and place it EVENLY over the opening with the short beveled edges facing down.  Make sure that all of the pivot pins are seated into the slots, then squeeze one corner of the cap into the base using pliers, then squeeze the other edge until the cap snaps into place.  Connect the 3 inner arm assembly pivot pins with the inner Triangle/Base the same way, only this time make sure the cap is facing inwards - opposite of the outer one.

It doesn't matter which end of the arm assembly you use - it works either way.

A good way to start is to make a pentagon(5) and then make hexagons(6) surrounding it.  Remember that pentagons(5) DO NOT TOUCH EACH OTHER, and always have two hexagons(6) between them.  Once you get the hang of it, you can most likely complete it in less than an hour.

I printed this in PLA, because that's all I have, but PETG would probably work better - it is a bit fragile.  You can roll it around, but don't kick it.  With all things printed in PLA, it loosens up over time, which is not a bad thing in this case - the sphere will open and close much more smoothly.  By the way, I recommend NOT fully opening the sphere - it can be difficult to close.  If you do this, you can close it safely by pulling the triangles slightly apart, working your way around the sphere.

I have not tried scaling this up (not enough room on my build plate) or down (parts might be too fragile), but hey, if you want to try it, go right ahead - just make sure you post the make, I'd love to see it scaled down - or WAY up!

I wish you luck making this.  Please hit Like if you think this is as cool as I think it is!

All the best from the cave,

TroggPrinter