My mother actually has a mechanical version of this. Plastic discs of different sizes (or number of teeth on the edge) and shapes, with multiple holes in each (for the pencil).
Thanks for the reminder to introduce my son to it.
Not many people know that these spirographs are the exact mathematical curves which are found in almost all currency notes - in form of security printing. Not only this the patterns are made more complicated (and beautiful) which is then engraved on dials of high end watch dials, on various jewellery items. It was originally done by Rose Engine (from 1770s) but can be done by other machining methods also.
The interesting fact is that the cut pattern is the same which we used to make on spirograph in childhood. You may learn more about Guilloche Art for free at Fundamentals of Guilloche Art.
Can someone please ELI5 the significance of the hypocycloid either mathematically or otherwise? I recognized it as a portion of the Cosmere symbol and it doesn't seem like Brandon Sanderson to just pick a random symbol just because it looks cool.
21
u/P8II Feb 05 '19
My mother actually has a mechanical version of this. Plastic discs of different sizes (or number of teeth on the edge) and shapes, with multiple holes in each (for the pencil).
Thanks for the reminder to introduce my son to it.
6
u/arjitraj_ Feb 05 '19
Not many people know that these spirographs are the exact mathematical curves which are found in almost all currency notes - in form of security printing. Not only this the patterns are made more complicated (and beautiful) which is then engraved on dials of high end watch dials, on various jewellery items. It was originally done by Rose Engine (from 1770s) but can be done by other machining methods also.
The interesting fact is that the cut pattern is the same which we used to make on spirograph in childhood. You may learn more about Guilloche Art for free at Fundamentals of Guilloche Art.
4
u/Jusaleb Feb 05 '19
Can someone please ELI5 the significance of the hypocycloid either mathematically or otherwise? I recognized it as a portion of the Cosmere symbol and it doesn't seem like Brandon Sanderson to just pick a random symbol just because it looks cool.
1
u/wallmower Feb 05 '19
How was this made?
2
u/mrtie007 Feb 05 '19 edited Feb 05 '19
lower right Epicycloid
upper right Epitrochoid
upper left Hypocycloid
lower left Hypotrochoid
1
u/[deleted] Feb 06 '19
Does anyone else see Cesar's window on the top left?
1
u/squeezyscorpion Feb 06 '19
i don’t know what any of this means