Showing posts with label how it works. Show all posts
Showing posts with label how it works. Show all posts

10/04/2026

19. Harmonic shapes - crinkle crankle wall

When we think of a wall, the first thing that comes to mind is a brick construction that is as straight as possible. It is known that the straight line is the minimum path between 2 points; so, you decide the extremes, you plant 2 stakes, you pull a rope and you start building.

In the county of Suffolk, UK, there is also another example of a wall:


The crinkle crankle wall dates to Ancient Egypt and, among other things, saves bricks.

It has a sinusoidal shape that provides stability to the structure without the use of pillars or buttresses at regular distances.

For the same height, the number of bricks used in the wall is proportional to the product of its length and its thickness. Suppose that the wall has a sinusoidal shape and consider a section of wall 2π long. If the wall has the form of the function sin(x), then the length of this curve is found by calculating the following integral: 

If A = 0 we have a straight line, i.e. a flat wall with length 2π = 6.2832, while if A = 1 the integral is 7.6404; their ratio is worth about 1.22, i.e. 22% more.

But the sinusoidal shape considerably strengthens the wall and therefore allows you to use only one row of bricks instead of 2, halving its thickness, i.e. 122% long and 50% wide, in total only 61% of bricks are used.

As long as the value is less than 100% you will save material.

But for what value of amplitude A do we have 100% (i.e. the same number of bricks)?

With A = 2.6 the length is about 6.2822 (almost 2π)


A = 1 (in red)   -   A = 2.6 (in blue)

  

If you are interested, below you can find a nice list of "crinkle crankle walls" with photos:


Crinkle-Crankle Walls Of Suffolk : EDitorial 4-Jan-2016


Crinkle crankle wall - Wikipedia


Crinkle-Crankle Wall, Reclaimed Bricks in Ipswich | RBC – Reclaimed Brick Company

Crinkle crankle wall calculus

Crinkle crankle wall, Fulbourn © Bob Jones :: Geograph Britain and Ireland

Easton - Google Maps

Out and about looking at Crinkle Crankle Walls / Historical Association

Slangenmuur - Wikipedia

This Wall Uses Fewer Bricks Than A Straight Wall

 


26/07/2019

15. Oloid

Discovered by Paul Schatz in 1929, the Oloid is defined as the convex hull of 2 circumferences of radius R equal to each other, arranged on two orthogonal planes and such that each of the 2 steps to the center of the other.






This grooved surface has many interesting properties (for example, all of its generating lines have the same length).



The Oloid has a shape particularly suitable for the mixing of fluids.




The Oloid surface S is equal to the area of the sphere of radius R;
while by means of numerical calculation, it can estimate the volume V:


The Oloid is the only three-dimensional shape that can rotate on its entire surface.


When is made to roll on a flat horizontal surface, the Oloid moves uniformly because the distance from its center of mass at the surface is almost constant.


 The dell'Oloide equation corresponds to an algebraic surface of order 8 :




18/05/2015

2. How It Works: The Sewing Machine

 
 

It's a topological question: when the needle passes the tissue below, it carries the wire in the loop. On the other side there is a system that puts the wire of the second spool (the little one in the machine) in this loop, then the needle rises, taking with it the second wire.
In this way a series of knots are formed along the seam between the spool higher, the big one, and the lower, the small one.
The first practical and widely used sewing machine was invented by Barthélemy Thimonnier, a French tailor, in 1829.