[Howto]: Long size and double-scale Oloids

[Howto]: Long size and double-scale Oloids

Postby Eric » Fri Dec 04, 2020 11:36 pm

Here is my howto of the double-scale Oloid discussed in the Oloid thread in the 'Math-related Geomag discussions' forum.
Feel also free to take a look at my 'Oloid delirium' thread ;-)

Let's start.
First, I make 2 pentagonal bipyramids. The blue one is already finished on the photo below. Let's build the white one.
20201204_170904.jpg
I thought I needed to reinforce the inner structure to help it keep its perfect shape of pentagonal bipyramid (did it in the blue one).
20201204_171902.jpg
But I realized by testing it with the white one that it was not necessary. Once properly closed, the structure takes its shape, remains rigid and no longer deforms. So I removed the silver rods.

By connecting the free rods of the 1st photo to the corresponding spheres we give the concave shape to the double-scale pentagon
20201204_181256.jpg
Last edited by Eric on Mon Jan 11, 2021 8:59 pm, edited 2 times in total.
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Re: Double-scale Oloid howto

Postby Eric » Fri Dec 04, 2020 11:56 pm

To build the other side of the pentagonal bipyramid, I make each double-scale triangle one by one (first the outer frame and then the small triangle for the inner structure).
As long as you have not placed the last double-scale triangle of the pentagonal bipyramid, the structure deforms and is not fully rigid.
20201204_171534.jpg

Now we have our two pentagonal bipyramids that will collide ;-)
20201204_172525.jpg

But first, let's do some digging:
20201204_172830.jpg
We could build the double-scale oloid directly but I find it easier to build the two pentagonal bipyramids separately and then remove the excess rods
Last edited by Eric on Sat Dec 05, 2020 12:26 am, edited 1 time in total.
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Re: Double-scale Oloid howto

Postby Eric » Sat Dec 05, 2020 12:14 am

We have now to remove the 8 excess spheres to ensure the connection:
20201204_173440.jpg
View from the side

It's a little scary from above, but everything will be fine ;-)
20201204_173448.jpg
View from a higher point
All that remains is to carefully push them towards each other to fit them together.

What a great satisfaction when you hear and feel the clicks of the rods connecting to the spheres and the new structure finding its final rigid and strong shape! :D
Remember to check that the connections are firmly made on each sphere and adjust the rods if necessary.
20201204_173654.jpg
Tada: Final assembly :-)

Final count:
  • A pentagonal bipyramid is 60 rods and 22 spheres
  • A double scale Oloid is 96 rods and 34 spheres (you'll need 120 rods and 44 spheres if you go through the 2 bipyramids step)
See more photos and also my "Yin and yang Oloid" in the Oloid Delirium thread.
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Re: Long size and double-scale Oloids howto

Postby Eric » Sun Dec 06, 2020 2:34 am

Peter also challenged us for long size Oloids.
And I took up the challenge ;-)

Here's my howto for scale-1 long size oloid:
20201205_161503.jpg
Add the edge rods only

20201205_161519.jpg
Connect

20201205_161940.jpg
Fill the gaps to form triangles et voilà :-)

If rods are to short to connect to certain spheres, don't panic, just squeeze a little the pentagonal bipyramids by their vertices and that should fix the problem.
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Re: Long size and double-scale Oloids howto

Postby Eric » Sun Dec 06, 2020 2:44 am

Now the scale-1 extra long size Oloid:
20201205_160859.jpg
Prepare only the edges that will connect the vertices

20201205_161005.jpg
Connect and fill the gaps to form triangles

20201205_162357.jpg
Tada!

Nice shots to see in the 'Oloid delirium' thread, with also the twisted Oloid and the angular Oloid :shock:
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Re: Long size and double-scale Oloids howto

Postby Eric » Sun Dec 06, 2020 3:01 am

Let's go bigger now!
Here is how to build the double-scale long Oloid :D

First, split in half the double-scale Oloid that you took so long to build ;)
Or start from two pentagonal bipyramids. As you wish.
20201205_181641.jpg
It's a split!

20201205_182046.jpg
Add spheres to the free rods and prepare the edges only.
I learned with the scale-1 long Oloid that it's easier to build the edges first and then fill the gaps.

20201205_182242.jpg
Make the connection
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Re: Long size and double-scale Oloids howto

Postby Eric » Sun Dec 06, 2020 3:10 am

20201205_182653.jpg
Place the edges of the big triangular faces

20201205_183054.jpg
Fill the gaps with small triangles

20201205_183949.jpg
Admire your work

Nice shots in the 'Oloid delirium' thread 8-)

Let's talk about numbers for this big boy :o :
  • We added 40 rods and 16 spheres to the normal size double-scale Ovoid
  • So a long size double-scale Oloid is 136 rods and 50 spheres
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