Introduction

The concept of energy in physics can be confusing because it is not a tangible “thing,” but rather an abstract physical quantity that represents the ability of a system to do work. According to the law of conservation of energy formulated by the German physician and physicist Hermann von Helmholtz, energy cannot “disappear” or be created out of thin air but can only be transferred from one body to another and take on different forms. The fact that we use “energy” in everyday life in sentences like “I woke up this morning full of energy” or “She has positive energy” that have little or no connection to the physical concept only makes it difficult for students. To complicate things further, energy has many different units. I will do all the calculations below in joules, denoted j. A joule is a unit of energy in the MKS (meter-kilogram-second) system. One joule can be used to lift a relatively small apple one meter high, or to heat a gram of water by about 0.24 degrees Celsius. It is also the energy needed to light a one-watt light bulb for one second. In other words, it is a small amount of energy.

Every clock has a source of energy. When I was a child, wristwatches were mechanical and, in the evening, you would wind their spring. My father had an “automatic” wristwatch that seemed to me a technological marvel; the movement of the hand powered a rotor (a metal weight that wound the spring). My beloved had three cuckoo clocks in her grandfather’s apartment. At the foot of the coop was a balcony with loving couples. Every hour, a song was played, the balcony spun, and the couples spun within it, and when silence returned, everyone stood from their dance until the next hour. The energy for the clock was provided by pinecone-shaped weights that slowly descended. Once a day, they had to be raised again by pulling a chain. Today, wristwatches and wall clocks, if they are still used, are mostly electronic clocks based on the oscillations of the quartz crystal to display the passing time, so their energy source is an electric battery.

Lego Elephant Clock – Energy Calculations

The (original) elephant is made of copper, and partitions were installed in its belly, making it a hidden water reservoir. Lego is not waterproof, so there is a container made of transparent plexiglass (acrylic glass) in the elephant’s belly. A float with a hole (طرجهار) was placed in the reservoir, which slowly sank. In Al-Jazari’s case, this took half an hour. Considering the patience of modern viewers, I shortened the sinking time to five minutes.

Either way, when the float has finished sinking, its chain pulls the moving channel. This causes a metal ball to roll into its path, and a new ball takes its place. The ball falls into the dragon’s gaping mouth. The extra weight causes the dragon to swing on its axis and pull the float back to the water surface. The clock’s energy source is therefore the metal balls that a servant positions at the top of the clock at dawn. In this post, I will present the fixed and moving channel mechanism, as explained in “The Book of Knowledge of Ingenious Mechanical Devices”, my modern version, and also provide the energy calculations of the clock. This is the image of the Lego elephant with the ball channel area marked with a red circle, and also the heights of the steel ball at various locations, which will be used for the energy calculations later:

Lego Elephant Clock 2025

The ball channel mechanism in “The Book of Knowledge of Ingenious Mechanical Devices

The mechanism of the ball channels is described in subsection nine and is simple to understand. This is a drawing from the book:

The L-shaped channel is the fixed channel, and although the drawing shows only five balls, the clock had 29 balls intended for 14.5 hours of light at the height of summer, with one ball falling every half hour. The balls were made of bronze; this is not explicitly stated, but there is an identical mechanism in the water clock of the boat, and it is explicitly stated there that the balls are made of bronze and weigh 30 dirhams, approximately 90 grams.

Bronze is an alloy of copper and tin, and its density varies with composition. Assuming 8.5 g/cm³ these were balls of about 10 cm³ with a diameter of a little more than 2.7 cm. The balls I used are stainless steel, have a very similar density, and weigh 56 grams. The fixed channel is inclined so that the metal balls roll down to the moving channel. The latter is on the opposite slope and an axis. When the float pulls down the channel, the metal ball rolls away, and a new ball takes its place. This is a top view of the fixed channel and the moving channel.

A top view of the fixed channel and the moving channel in the Lego Elephant Clock.

Attached is a short video showing how the ball channels work:

Energy Calculations

The height of the ball relative to its final position is shown in the image above. The potential energy E_p is given by:

E_p =mgh

Where m is the mass of the ball, 0.056 kg

g is the free fall acceleration due to gravity and is equal to 9.81 m/s²

h is the height relative to the reference plane. At the starting point 0.95 m.

The energy available to us is:

E_p=0.056*9.81*0.95=0.52 j

Joule, as you may recall, is the unit of energy in MKS units and is explained shortly in the introduction. In Al-Jazari’s time, the concept of energy did not exist, of course, and in general, Al-Jazari makes few calculations and works mainly by trial and error. Can energy calculations be helpful to us? The fall of the ball provides energy to all parts of the clock, from the rotation of the bird to the operation of the mahout (elephant trainer and driver). The most essential part is raising the float to the surface of the water. At the beginning of the process, the ball is in the dragon’s mouth at the height of the castle, and the float is filled with water. At the end of the process, the float was lifted and turned over, and the dragon unloaded the ball above the vases. This is a drawing of the process:

Drawing the Dragon’s Rotation Process

I will discuss the physics of the buoy’s inversion process in detail in a future post that will focus on the dragon and its spectacular rotation. What can we learn from simple energy considerations?

The energy required to invert the buoy E_FF is given by:

E_FF =(m_w+m_f )*g*∆h

m_w is the mass of the water in the buoy, about 140 grams = 0.14 kg

m_f is the mass of the buoy, about 48 grams = 0.048 kg

g is the free fall acceleration, equal to 9.81 m/s²

∆h is the height difference between the submerged buoy and the inverted buoy above the water, approximately 10 cm = 0.1 m. The energy required:

E_FF=0.19*9.8*0.1=0.19 j

The energy available for the water clock:

E_p=mg*∆h

Where m is the mass of the stainless-steel ball, 0.056 kg

g is the free fall acceleration, equal to 9.81 m/s²

∆h is the difference in heights. The ball rolls into the dragon’s mouth at a height of 0.8 m and is released above the jugs at a height of 0.3 m. The difference is:

∆h=0.8-0.3=0.5 m

The energy available to us:

E_p=0.056*9.81*0.5=0.27 j

So there is enough energy to turn the float.

Introduction

The elephant clock is by far the most popular of all the works by al-Jazari. There have been several modern reconstructions, multiple animations, and it has its own Wikipedia entry, and more. In the previous post, I tried to explain why millions of viewers in the mall in Dubai or the “1001 inventions” were captivated by its magic. The current post is different from anything I’ve written so far and is a record of my journey to reconstruct the elephant clock in Lego, including the difficulties and the learning on the way. The elephant is in the initial stages, and I hope to post an update every week. I’d love to hear your suggestion, ideas, or advice you may have for me.

Elephant clock, Topkapi manuscript, 1206.

Why build?

When I started this journey, I was working at the Davidson Institute of science education. I proposed to Prof. Haim Harari, founding Chairman of Davidson Institute and former President of the Weizmann Institute of science, to build al-Jazari fifty machines in the “Science Garden”, an open-air museum in Weizmann Institute. Haim refused and told me that the Science Garden was rooted in the 17th-century Newtonian physics and he would like to bring it into the 21st century. Instead, my proposal would take us back to the 12th century… This blog is my alternative exhibition.

Beyond the magic of al-Jazari machines and their value to the history of technology, It is important in undermining stereotypes about Islam that exist both in the Jewish and Arabic population in Israel. Arab Labor ( “AVODA ARAVIT”) is a racial slur that is widely used long before the amusing sitcom written by Sayed Kashua. The slur indicates low quality work. On the other hand, Arab society perceives itself as debilitated and with little contribution to the world of science. Arab students come to Weizmann Institute feeling this is the “temple of science” where they do not belong. The wonderful machines of al-Jazari emphasize the scientific achievements of the Islam golden age, which is not taught at schools at all, and offer a different perspective to both Jews and Arabs.

Previous posts included animations. To me, there is no replacement for actually building the machine. The difficulties on the road and resulting learning are priceless.

Why Lego?

Some reconstructions of al-Jazari were made, including the Elephant Clock. These are pictures of three of reconstructions:

Three reconstructions of the Elephant Clock, left Ibn Battuta Mall in Dubai, in the middle Sharjah Museum of Islamic Civilization, right the Istanbul Museum of The History of Science & Technology in Islam.

I have a lot of respect and appreciation for the restorers. Their Elephant clock is possibly more similar to the original than I am assuming. Somehow their beautiful work can’t recreate the beauty of the illustrations in the book and in the process of transferring the 2D illustration to a 3D reconstruction some of the magic is lost. I think they are too realistic. The elephant is a “real” elephant and the canopy is beautiful and very dignified. There is no room left for our imagination. Also, the Elephant Clock is static in Istanbul as well as in the 1001 inventions exhibition, more like a statue demonstrating the beauty of the design rather than a working water clock. In Dubai, I think, the Elephant Clock is powered by electric motors. This reduces the experience, at least in my eyes. The reconstruction should rely on 12-century technology and the ability of al-Jazari to perform complex control scheme before we had electronics and controllers. The magic of al-Jazari is contemporary (strange but true).

I have no reason to assume that I know something the restores did not know. The move to LEGO simplifies the aesthetic choices and offers playfulness and sense of contemporary at the same time. No LEGO work is a part of the Turkish tradition of miniature art. However, Lego is free to correspond with this art. Lego has its own design language, and even adults works in Lego and Hyper-technology Lego works are fun and playful, also this is a great excuse for me to build in Lego…

Previous al-Jazari machines in Lego

I know only one of al-Jazari machine made in LEGO. Interestingly enough, it is the Elephant Clock. You can see it here:

I Think the design is charming and the use of LEGO is both clever and quite sophisticated. There’s breathing space in the Lego elephant, and I like the human figures, which are an entertaining use of LEGO components. But although the design follows al-Jazari, its operation is based on the “smart brick” (a programmable, lego controller which serves as the brain of LEGO robots) and electric motors. This, in my mind, defies the point. Or at least the challenge I am hoping to meet: reconstruct, and on the way test and learn,al-Jazari engineering from the 12th century.

Where am I

I made a plan to build a  LEGO elephant, 60  bricks high(about 60 cm). There is no precise measurement in the Book of Knowledge, but this is roughly 2:1 scale in relation to the book. The giant elephant you see in the Dubai restoration, for example, is elephant real size (~3.5 m) rather than the dimensions extracted from the original work. I used Tinker Cad, I found it very user-friendly. I inserted a 3D a model of an Asian elephant and filled it with LEGO bricks:

At this point, I did not insert to the model the other components of the clock, such as the canopy, Mahout, the dragons, etc. l will see as I go if I prefer hands-on experimentation or the use the CAD software.

I ordered 5420 dark gray Lego bricks of various sizes from eight different suppliers, from Denmark to Croatia, from the U.S. to France. Thank you bricklink (Internet market for LEGO) I wouldn’t manage without you. The reason for so many suppliers is simple. No one supplier had so many gray parts. Last week I began to build. It looks like this:

About one-third of my LEGO elephant. The trunk rests in our cereal Bowl. Otherwise, it would fall. I began experimenting with the buoy and the mechanism of the scribe, but this will be in my next post.