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Author Topic: A spinning top made with a sea urchin shell  (Read 142 times)

Iacopo

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A spinning top made with a sea urchin shell
« on: November 19, 2018, 03:13:06 PM »


This is a decorative spinning top, very different from my usual ones.
I used the shell of a coelopleurus, a kind of sea urchin.
These shells, for their shape, dimensions and simmetry are suitable for making tops.  The protuberances in the shell are the joints for the spines, which the animal can move, for defense, and for slowly walking along the seabed. The shells can be brightly coloured, often with pink, red and violet stripes. The violet parts in the shell I used seem like painted, but they are not, it's their natural color.   

The shell is very light and thin, so I filled it with resin, mixed with metal powder, to make it more robust and heavy, so that it can act as a flywheel.
Since the simmetry of the shell is good, but not perfect, I had to balance the top, with the techniques explained in one of my old videos.  The wobble you see in the video is not unbalance, but precession.

I used boxwood for making the stem and the stand of the top; boxwood is very fine grained and hard, so it is suitable for making  fine, detailed turnings.  Some parts of the stem are very thin, (little more than 1 mm), so I inserted a 1mm steel rod reinforcement inside it, otherwise the stem would be far too weak for to spin the top.

Given the proportions of the top, tall and narrow, the relatively high contact point/center of mass distance, which makes for a high toppling down speed, and the rough surface of the shell, which makes for more air drag, this top doesn't spin for long;  usually it spins for 60-90 seconds, my best spin with it is 1'46".



https://www.youtube.com/watch?v=P_cGCZ2b9pc

I find sea urchins fascinating.  The following are two short videos about them, while it moves, and while it eats, (their teeth are a bit impressive):

https://www.youtube.com/watch?v=Agmlmb_9s2Y

https://www.youtube.com/watch?v=EUjepfku8ag

I painted digitally the first picture in the video.  Here is a real photo of a Coelopleurus: 

https://fr.wikipedia.org/wiki/Coelopleurus_floridanus#/media/File:Coelopleurus_floridanus_NOAA.jpg

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Jospin

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Re: A spinning top made with a sea urchin shell
« Reply #1 on: November 19, 2018, 03:31:59 PM »

Very cool!
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Iacopo

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Re: A spinning top made with a sea urchin shell
« Reply #2 on: November 19, 2018, 04:07:30 PM »

Thank you, Jospin !
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the Earl of Whirl

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Re: A spinning top made with a sea urchin shell
« Reply #3 on: November 19, 2018, 07:21:16 PM »

You are amazing, Iacopo!!!

Yes, those teeth are impressive.....and kind of scary!
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Jeremy McCreary

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Re: A spinning top made with a sea urchin shell
« Reply #4 on: November 19, 2018, 10:18:27 PM »

Absolutely stunning, Iacopo! Getting 60-90 s of spin time out of this shell without appreciable wobble was no mean feat.

Now that you've joined me in the world of high-drag finger tops, can't wait to see what you come up with next!
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ta0

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Re: A spinning top made with a sea urchin shell
« Reply #5 on: November 19, 2018, 10:30:00 PM »

Beautiful!  8)

Now you found your match in design for functionality and beauty: nature!  ;)
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jim in paris

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Re: A spinning top made with a sea urchin shell
« Reply #6 on: November 19, 2018, 11:43:21 PM »

oh!oh!
 che bellissima trottola !

in corsica , sea urchins are sometimes called "chataignes de mer" (sea chestnuts)
it's allowed to pick them up only from Dec 1st to March 1st
that's why when you pick up urchins off-season ,people say :
je vais aux chataignes ..( "i'm going to fetch chestnuts") ;D

ciao
jim

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Iacopo

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Re: A spinning top made with a sea urchin shell
« Reply #7 on: November 20, 2018, 03:14:37 AM »

You are amazing, Iacopo!!!

Yes, those teeth are impressive.....and kind of scary!

Thanks ! 
They eat algae above all, but I wouldn't put a finger in front of its mouth.
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Iacopo

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Re: A spinning top made with a sea urchin shell
« Reply #8 on: November 20, 2018, 03:29:02 AM »

Absolutely stunning, Iacopo! Getting 60-90 s of spin time out of this shell without appreciable wobble was no mean feat.

Thank you !  Unbalance becomes evident at slow speed, and this top topples down at a still relatively high speed, so I don't know how perfect is the balance, but certainly is not bad. 
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Iacopo

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Re: A spinning top made with a sea urchin shell
« Reply #9 on: November 20, 2018, 03:35:00 AM »

Beautiful!  8)

Now you found your match in design for functionality and beauty: nature!  ;)

I agree, nature is beautiful.  Thank you !
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Iacopo

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Re: A spinning top made with a sea urchin shell
« Reply #10 on: November 20, 2018, 03:43:45 AM »

in corsica , sea urchins are sometimes called "chataignes de mer" (sea chestnuts)

Thank you, Jim !  In Italy we call them "ricci di mare", (sea hedgehogs), but I find the expression "chataignes de mer" very appropriate.
I bought my shells in E-Bay, they come from Cebu, (Philippines).
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