[Howto]: Berlingot (+ also Hourglass and Water Drop)

[Eric]

Here we are together to build the famous Berlingot

Note that the steps below are also a new and faster way to build the giant hourglass and water drop!
The old method of construction should be replaced by this one.

Further below is the construction method for the medium-sized berlingot.

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Let's go for that big boy!
Prepare 396 rods and 134 spheres.

First of all build a truncated icosahedron with the fast method.

Choose any hexagon and remove the 3 rods shown in pink here.

[Eric]

Remove the sphere in the center of the hexagon.

Without disconnecting any rod, deform gently the hole by pushing the 3 pentagonal pyramids outwards.

Prepare these 4 additional structures to build the spike.

[Eric]

Take the 9 rod triangle prepared above.
Fold each of its 3 points down and connect it on top of the structure.

[Eric]

Fill in the holes with the 6-pointed stars.

Now you have the first bulb of the giant hourglass.

Add the tripod on top. And there you get the 297-water drop.

[Eric]

At this step, check the rods alignments from above and press where necessary to give a nice well rounded and symmetrical shape.

Identify the hexagon from which we will build the second vertex (here in blue). Make no mistake, otherwise you won't be able to build all 4 vertices.
There are six possibilities that are correct. It should be a hexagon just below one of the 3 pentagons closest to the pink vertex.
Be careful, there are three other pentagons which are just a little further away and which are not the right ones.

Proceed the same way as for the pink vertex to build the blue vertex.

[Eric]

For the 3rd vertex, there are only two possible starting hexagons.
You must choose the hexagon that is directly under one of the 2 pentagons closest to both the pink vertex and the blue vertex.
This hexagon must be surrounded by 3 pentagons!

As before, proceed in the same way as for the pink and blue vertices.
And there you have the yellow vertex.

At this stage, handle the structure with great delicacy, keeping your hands as open as possible to increase the points of support so that it does not collapse under its weight or the pressure of your fingers.
You can still have it rest on its belly. But at the 4th vertex, this will no longer be possible. At the risk of it collapsing under its own weight

View from the inside

[Eric]

As said just before, it is imperative to build a support to rest the shape on one of its vertices before opening it again to build the 4th vertex.

I haven't tried it, but I'm sure it's not possible to lay it on one side without it collapsing under its own weight.

[Peter Jepsen]

Ooh, this is really really clever Eric!
Compliments!

[Eric]

Now let's attack the medium-sized berlingot.

Here's what we're talking about:

Note that the steps below are also a new and faster way to build the 255-hourglass and 132-water drop!

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Prepare 168 rods and 58 spheres.

First of all build an icosidodecahedron with the fast method.

Choose any triangle and remove the 3 rods shown in blue here.

[Eric]

Without disconnecting any rod, deform gently the hole by pushing the 3 pentagonal pyramids outwards.

Add rods to build the vertex as shown below.