Showing posts with label Euclid. Show all posts
Showing posts with label Euclid. Show all posts

Tuesday, September 23, 2025

 Building Archimedean Solids and Platonic Solids: the easy way

Let the lights of the Cosmos generate the geometry of the solids, said Plato

There have been thousands of mathematical pages written on the Archimedean solids and the Platonic solids. However, there has not really been any published work on how to build the Archimedean solids and Platonic solids. This book is the most comprehensive work ever published on how to construct the Archimedean solids and the Platonic solids.

The field of polyhedral geometry, a foundational branch of mathematics, relies on a precise set of terminology to describe the spatial relationships and properties of three-dimensional forms.

Unfortunately, the foundational branch of mathematics for polyhedral geometry does not include the terminology of carpenters who, for centuries, built the Archimedean solids without the aid of mathematics.

Whether you’re building hollow solids or skeletal solids, this book includes miter angles, blade tilt angles, diagrams, and templates to help you make these solids either as hollow solids or as skeletal solids.

This book utilizes geometry to draw out the vertex for each polyhedron, thereby obtaining the dihedral angle and edge bevel angles. No math is required. 

This book is a PDF file containing over 40 table saw sled templates for printing, as well as 382 pages of detailed techniques and instructions. Taking the guesswork out of building the solids. 

 This purchase also includes Posters.PDF download, and Pythagorean Brotherhood Descendants Math Notes PDF download.
Buy for the low price of $39.95


Purchase the book as a PDF file for $39.95




Let no one ignorant of Geometry enter, said Plato



da Vinic's Polyhedra Φ Project

Golden Rectangle Rhombicosidodecahedron

Φ Rhombicosidodecahedron



Archimedean Solid Fish Tanks


Archimedean Solid Solar Lights with Light Refraction

Roman Dodecahedrons

Platonic Solids as Hollow Solids

Platonic Solids as Skeletal Solids

Archimedean Solids as Skeletal Solids with easy-to-follow table saw sleds


Wooden Polyhedra: Precision Construction Techniques
Mastering Mathematical Beauty Through Advanced Table Saw Work
Introduction
The construction of polyhedra in wood is a testament to the union of mathematical elegance and practical craftsmanship. These intricate forms, defined by their precise geometric properties, present a unique challenge to woodworkers, requiring not only a deep understanding of geometry but also mastery of the tools and techniques that enable flawless execution. This book is designed to guide both novice and advanced woodworkers through the demanding process of building wooden polyhedra, focusing on the meticulous setting of miter and bevel angles on a table saw, the use of specialized jigs, and the essential skills needed for perfect assembly.

Understanding Polyhedral Geometry
Polyhedra are three-dimensional shapes bounded by flat polygonal faces, with the regular vertices and irregular vertices, including the Platonic solids (such as cubes, tetrahedra, and dodecahedra) and Archimedean solids. Each face must meet its neighbors at precise angles, and every edge and vertex must be carefully accounted for in the design and construction process. Before beginning, familiarize yourself with the geometry of your chosen polyhedron—study its faces, edges, and required angles, as this will inform every step of your woodworking plan.

Translating Geometry to Woodworking
The leap from geometric diagram to physical wood requires accurate calculation of both miter angles (the angle at which two pieces meet) and bevel angles (the tilt of the saw blade to match the polyhedral faces). For example, constructing a dodecahedron involves cutting twelve identical pentagonal faces, each meeting at precise dihedral angles. Calculating these angles is crucial; this book includes all the necessary mathematical references and woodworking calculations to determine the exact settings for your table saw.

Utilizing Table Saw Sleds Templates
Table saw sleds are indispensable for polyhedral construction. A well-designed sled stabilizes your workpiece and maintains consistent angles for repeated cuts. For complex polyhedra, the templates included in this book required toggle clamps to hold pieces at unusual angles. Build these table saw sleds from stable materials and verify their accuracy before use.
Techniques for Flawless Assembly
Achieving a seamless fit across the many joints of a polyhedron is the ultimate test of woodworking precision. Here are essential assembly techniques:
⦁ Dry Assembly: Before gluing, assemble all pieces to ensure a proper fit. Minor adjustments can be made with sanding blocks or shooting boards.
⦁ Clamping Strategies: Use band clamps, rubber bands, or custom jigs to hold pieces together without distorting the angles.
⦁ Glue Selection: Choose a wood glue with a reasonable open time to allow for careful positioning. I use Titebond III
⦁ Finishing Touches: After assembly, sand lightly to remove any small imperfections, being careful not to alter the angles at the edges of the polygon faces.

Challenges and Mastery
Polyhedral woodworking is not for the faint of heart. Even a deviation of a few degrees can result in visible gaps that compromise both the structural and aesthetic integrity of the final piece. This book serves as both a challenge and a benchmark for advanced woodworking skills, pushing the limits of a table saw’s accuracy and the craftsman’s attention to detail. Mastery is signified not only by the completion of the polyhedral but by the pursuit of perfection in every joint and surface.

Final Words on this book
Constructing wooden polyhedra is a journey through mathematical art and technical mastery. By following the guidance in this book—calculating angles precisely, mastering saw setups, and executing flawless assembly—you will unlock new levels of woodworking skill and create captivating pieces that celebrate both geometry and craftsmanship.

Purchase the book as a PDF file for $39.95


















Sunday, June 15, 2025

 Euclid's Elements Book XIII Proposition 18: Exam

Here's a video I made of the drawing for Euclid's Elements Book XIII Proposition 18: Exam. As well as a sanitized version of the drawing. 



Here's a blank Exam paper you can print out at 24"x36"







Wednesday, April 30, 2025

 Euclid's Elements Book XIII Proposition 18


In a polygonal pyramid, the angle between a base edge and a lateral edge (edge connecting the base to the apex) is called the base-edge angle or edge angle. It's one of several angles you can consider in a pyramid, including angles between faces (dihedral angles). 


Relating the polygonal pyramid edge angle to a roof-framing hip rafter is the easiest way to prove Euclid's Book XIII Proposition 18 is correct. As well, as my drawing of Proposition 18.  Euclid states that the line HC is 5 times the square of lines HK and KC. So, how did Euclid know this was true? How do we prove it's true.  How do we know the lines representing the edge length of the Platonic Solids are the edge lengths of the Platonic Solids when the Platonic Solid is circumscribed in a sphere with a radius of one?



For some reason, Euclid didn't use Euclid's Elements Book II Proposition 11 Extreme and Mean Ratio for The Golden Ratio as the base drawing for Proposition 18.  As, seen on the next couple of pages the Extreme and Mean drawing provides all the proof he needed for comparing the edge lengths of the Platonic Solids when inscribed in a sphere with a radius of one. 



Radius EK = 1
AN side of Cube = 1.15470
AK side of Octahedron=1.41421356
AM side of Icosahedron = 1.051462
CN side of Tetrahedron = 1.632993
AQ side of Dodecahedron = 0.713644
Icosahedron Development
Line AM is the edge length of the Icosahedron inscribed in a sphere with a radius of 1. Point E is the center of the sphere. Points A-M are points on the sphere. Line SM is a plane perpendicular to the line AE. Line SM is the dimension to the center of the deck-plan view drawing of the pentagon with a sphere that has a radius of 1. 

Line AH is the extreme ratio of the Golden Ratio. Angle ACH is the Golden Slope Triangle. Line EB is the square root of 5. Both lines CH and EB intersect at point M. Therefore, we can say the Edge of the Icosahedron is developed from the Golden Ratio and the square root of 5. 

Dodecahedron Development

Line AQ is the edge length of the Dodecahedron inscribed in a sphere with a radius of 1. Point E is the center of the sphere. Points A-Q are points on the sphere. Line YQ is a plane perpendicular to the line AE. Line YQ is the dimension to the center of the deck-plan view drawing of the Equilateral Triangle with a sphere that has a radius of 1. 

Line AH is the extreme ratio of the Golden Ratio. Angle GCF is developed from the extreme ratio of the Golden Ratio. Line XB is developed from the Golden Ratio of 1.61803. Both lines GC and XB intersect at point Q. Therefore, we can say the Edge of the Dodecahedron is developed from the Golden Ratio and the extreme ratio. 

To prove the lines forming the triangles containing the edge length in the semi-circle of the sphere are correct, you can develop the deck-plan view for each of the Platonic Solids as a roof framing exercise. Then, develop the Edge angle triangle(hip rafter slope triangle) and use a bevel square to compare the angles in the triangle to the angles in the semi-circle. 

The deck plan view drawing is developed from a vertex point and the face that intersects the vertex point. 

Tetrahedron
is defined by four equal equilateral triangles and four Vertices
with three edges meeting at each vertex

Cube
is defined by six equal squares and eight Vertices
with three edges meeting at each vertex



Octahedron
is defined by eight equal equilateral triangles and six Vertices
with four edges meeting at each vertex




Icosahedron
is defined by twenty equal equilateral triangles and twelve Vertices
with five edges meeting at each vertex



Dodecahedron
is defined by twelve equal equilateral triangles and twenty Vertices
with three edges meeting at each vertex



To complete the proof of my drawing for proposition 18, you can draw out the hip rafter slope triangles using any radius for the semi-circle. The edge length of the Platonic Solid in the semi-circle is equal to 2 times the radius of the semi-circle times the "rise" leg of the hip rafter slope triangle when the hypotenuse of the hip rafter slope triangle is equal to the radius of the sphere. This is supported by using congruent angles for the edge length of the Platonic Solid. 


A couple of extra drawings of the Icosahedron with the √5 triangles that develop point M. 





2 x Radius of the sphere  x gd = Edge Length in the sphere



Icosahedron developed from √5 Triangle.

Icosahedron Developed from Five Squared

Euclid states that HK is quadruple of the square at KC. Then he says that the square on HK is five times the square of HK and KC. This is the same for line aE that develops the Golden Ratio of 1.618. 

As, seen in this drawing the line AF ,Golden Ratio, is also the straight line of a Hexagon & Decagon. Then we can use the line AF, Golden Ratio, to develop the deck-plan view of the pentagon of the Icosahedron. Line HK is the radius of the deck-plan view of the pentagon and line AH is the length of each side in the pentagon, as well as each side of an Icosahedron.


Only an Alien would have known that cutting the line AL into extreme and mean ratio would have developed the Golden Ratio of AX that is part of the straight line containing the Hexagon and Decagon inscribed in a circle with the radius equal to one.


The vertical lines EC,FD, ML, and QH are the radius's used for the development of the deck-plan view drawings. These radius's develop the Platonic Solid with a sphere circumradius of 1.

Wednesday, April 16, 2025

 Euclid's Elements Book XIII Proposition 17


I have always been fascinated by “who knew what and when they knew it. “ As well as how they knew it. So, yesterday I was searching for a download link on the book De quinque corporibus regularibus by Pierodella Francesca. That has the Platonic Solids and the Archimedean solids. I had already downloaded the book Divina proportione by Luca Pacioli. That supposedly plagiarized Piero della Francesca book. I saw in Luca Pacioli book that he had drawn Euclid's Elements Book XIII Proposition 17, but not Euclid's Elements Book XIII Proposition 18. So, I was wondering if Piero della Francesca had a drawing of Euclid's Elements Book XIII Proposition 18. I never did find a link to download Piero della Francesca's book. Even though I read on a page at the JLC forum, I thought I should study Stereotomy by reading the book De quinque corporibus regularibus by Piero della Francesca 15 years ago.

 

Over the last two months, I’ve been studying Euclid. Stereotomy is taking a point in 3D space and laying down that 3D point on a 2D drawing. So you can scribe the wood. After studying Euclid for the last two months, I realized I needed to take the next step in my journey in geometry and mathematics. Where you take a point in 3D space and transfer that point to another point in 3D space.

 

Hippasus, who was part of the Pythagorean Brotherhood, a secret society of mathematicians, could draw the Platonic Solids, the Icosahedron or the Dodecahedron. I don't know which one it was. But he was stoned to death for having too much knowledge in 500 BC.

 

My goal in my journey in geometry and mathematics is to learn Critical Thinking in Geometry so I can lay down the 3D points in space like Hippasus and Euclid. Euclid's Elements Book XIII Proposition 17 is an excellent example of Critical Thinking in Geometry. 


Representing a three-dimensional 3D point in space, the objects that compose it are studied analytically, in their shapes and position in relationship to the place that contains them. 


My study on nesting the Platonic Solids is based on Euclid's proposition 18. Here I'm able to draw out the edge lengths of the 5 Platonic Solids in a sphere using 1.618 and √2. 


Tetrahedron, Cube, Octahedron, Icosahedron, and Dodecahedron

Sphere Radius = EC = AC = 1

FB side of Cube = 1.15470

EB side of Octahedron = 1.41421356

MB side of Icosahedron = 1.051462

AF side of Tetrahedron = 1.632993

QB = NB side of Dodecahedron = 0.713644 


(√5 + 1)÷2= 1.618033

2÷√3 = 1.1570

√2 = 1.41421

√(2- ((2√5 )÷5))= 1.051462

2÷√3 *√2 = 1.632993

(2÷√3 ) ÷ ((√5 + 1)÷2)= 0.713644







Extreme and Mean Ratio
 The Golden Ratio 


To cut a given straight line so that the rectangle contained by the whole and one of the segments equals the square on the remaining segment.

 
Triangle ABE is the √5 triangle, and triangle GFC is the Dodecahedron Hip Rafter Slope.

Euclid's Elements Book XIII Proposition 18

To set out the sides of the five figures and compare them with one another.
Set out AB the diameter of the given sphere, and cut it at C so that AC equals CB, and at D so that AD is
double DB. Describe the semicircle AEB on AB, draw CE and DF from C and D at right angles to AB,
and join AF, FB, and EB. Then, since AD is double DB, therefore AB is triple BD. In conversion, therefore, BA is one and a half times AD. But BA is to AD as the square on BA is to the square on AF, for
the triangle AFB is equiangular with the triangle AFD. Therefore the square on BA is one and a half times the square on AF. But the square on the diameter of the sphere is also one and a half times the square on the side of the pyramid. And AB is the diameter of the sphere, therefore AF equals the side of the pyramid. cube.





Euclid's Elements Book XIII Proposition 17
To construct a dodecahedron and comprehend it in a sphere, like the aforesaid figures; and to
prove that the square on the side of the dodecahedron is the irrational straight line called
apotome.

BCEF is the top of the Cube. H,N,M,O are midpoints of the square on top of the cube. Draw lines HM, NO, GK, and HL. Mark off point J, the midpoint of HP, and draw line OJ. Then draw line JY the length of OJ.  Develop the square PYIS. Point S will divide the line PO, apotome, into the Golden Ratio. PS is the extreme, and SO is the mean. Mark off points UXV perpendicular to the plane of the cube, using the length PS. Mark off point T, using the length SO. Mark off point W perpendicular to the plane on the side of the cube, using length PS. 








The "Tint Roof" is also the first bastard hip roof ever drawn.(230 BC)








Triangle WXW' is the dihedral triangle for the Dodecahedron. 
The angle between two planes in the Dodecahedron.
The Dodecahedron dihedral triangle angle is 116.5650°








Luca Pacioli's portrait with him drawing the edge length for the Octahedron on the slate board.

 Luca Pacioli 


Icosahedron inscribed in a cube, from De quinque corporibus regularibus, and a modern illustration of the same construction
The edge length of the Icosahedron inscribed inside a cube is:
 cube length ÷ 1.618 = Icosahedron edge length

Then, connect the ends of the Icosahedron edges to the 20 triangular faces of the Icosahedron.