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The real giant hourglass (585 rods) and its derivatives

PostPosted: Mon Jun 14, 2021 11:46 pm
by Eric
I took a little time to experiment with the opposition of Lobel frames. What I will detail in another post, because it's really interesting.
And one thing leading to another, I ended up with this very very satisfying shape.
This 585-rods-hourglass is surprisingly strong and stiff.

I also took pictures for a nice howto. [Edit]: contains a new, faster and more efficient method than the previous one (thanks to the berlingot ;-)).

(Click on the photos to see them in larger size)
Beautiful interweaving of colored lines

From the inside


Re: The real giant hourglass (585 rods)

PostPosted: Mon Jun 14, 2021 11:50 pm
by Eric

The Giant Hourglass

It's like a kind of 3D infinity symbol.


Re: The real giant hourglass (585 rods)

PostPosted: Tue Jun 15, 2021 4:04 pm
by Peter Jepsen
Huuuuge compliments to you Eric!

This one is phenomenal. As I already told, I will have to try this one for sure.
Karl Horton, are you paying attention?! :)

Re: The real giant hourglass (585 rods)

PostPosted: Wed Jun 16, 2021 3:15 am
by Eric
Thank you Peter, it touches me :-)

You can also play with one of the bulbs and get this cute tree:



Re: The real giant hourglass (585 rods) and its derivatives

PostPosted: Wed Jun 16, 2021 3:19 am
by Eric
Cute tree from above

or this pretty hot air balloon:

Re: The real giant hourglass (585 rods) and its derivatives

PostPosted: Wed Jun 16, 2021 6:43 pm
by Eric
Here is the little brother (255 rods) ;)
It is even more solid and resistant.
[Edit]: Have a look at here to learn how to build the two bulbs of this shape.



Re: The real giant hourglass (585 rods) and its derivatives

PostPosted: Wed Jun 16, 2021 7:29 pm
by Eric
Playing with one of the two bulbs I got the water drop shape (that broke the camel's back ;) )

I take the liberty of putting here an excerpt from a conversation I had in private with Peter about this giant hourglass. That might interest some?

"The obvious weak point of the structure is the junction between the two bulbs, concentrated on only three spheres.
It is very solid for the forces applied longitudinally because these 3 spheres connect 8 rods each (21 rods for 24 connections in total to ensure the junction), which are moreover perfectly aligned between the upper part and the lower part for a good distribution of the loads.
On the other hand, for the transverse efforts, it is another story ;-)
So for the transition from the horizontal position to the vertical position, I did it without splitting it in two, but it is necessary to support the upper part and the lower part simultaneously to carefully accompany the movement.
When the structure is placed horizontally on the table, you can even roll it gently if you slightly push at the same time on both ends to strengthen the central connection. If it breaks in handling, it's at the junction, not elsewhere. The bulb is very strong in itself.

As for the choice of colors, even if I try to think about it a little from the beginning, I often finalize it afterwards. It's pretty quick and you waste a lot less time than trying to think of the final color scheme right from the design stage.I try to find lines that will emphasize the roundings as much as possible.
I locate a line of rods which makes a beautiful curve and seems harmonious to me and I then replace the rods one by one with the final color, of course respecting the polarities. It is not uncommon for me to have to do it several times to find a final result that I am satisfied with.
At first I had done mirroring, but it didn't work well with the original color scheme of my first bulb. It did not give nice regular and harmonious curves. Since I wanted my color lines to run from top to bottom, the rods at the center junction determined the final curves I had to follow. You will notice that each color constitutes one and the same continuous and regular line in the shape of an 'eight' around the hourglass.

If I had just added a height of triangles between the two bulbs at the central junction, that would have rotated the base of the top bulb to a vertex vs edge configuration instead of vertex vs vertex (which ended up mirroring the bulbs) and I could have broken the mirror effect and got one or more spirals around the hourglass. But to my opinion this additional ring of triangles would have broken the general harmony of the shape."

Re: The real giant hourglass (585 rods) and its derivatives

PostPosted: Mon Jul 05, 2021 10:50 am
by Eric
The peanut

I disassembled my hourglass.
I removed 3 rows of triangles on each bulb (6 rows in total in the narrow central part of the hourglass)
Here is how I did not break everything by removing part of the structure:

Deformation of the right bulb just to show that we could start on a triangular base:

I reassembled both bulbs and I got this wonderful ... peanut:

it has no real aesthetic or functional interest. It was just to try ... :D

Re: The real giant hourglass (585 rods) and its derivatives

PostPosted: Mon Jul 05, 2021 10:56 am
by Eric
Same job on the small hourglass (removed 2 rows of triangles in the center - 1 row on each bulb):
The small peanut

Small and fat peanut side by side:

Another try by removing only one row of triangles per bulb, i.e. 2 rows in the center of the hourglass:
Removed rods on the right side

It was just to see if it was doable. It is ;)