Warning! This post, like the upcoming ones, will be filled with technical jargon and details that may be of interest to enthusiasts of 12th-century technology. Apologies to readers who see Al-Jazari as a window into 12th-century culture.

Introduction

Six years ago, when I started working on the Lego elephant clock, I wrote:

“The elephant is in the initial stages, and I hope to post an update every week. I’d love to hear your suggestions, ideas, or advice you may have for me.” You can read the original post here.

In the meantime, I earned a bachelor’s degree in Arabic and also returned to teaching at Davidson; however, all these distractions prevented any real progress. Now, I am working on it continuously, and this is what the elephant looks like now.

The ambition to design the elephant clock purely from Lego proved unrealistic. The elephant itself and some of the delicate mechanics are from Lego. Still, many mechanisms were redesigned, based on the descriptions in al-Jazari’s book, using CAD software (Fusion 360) and printed on a 3D printer (FlashForge Inventor Dual Extruder).

How does the elephant clock work?

The elephant clock features eight distinct mechanisms with intricate interrelationships. They will be described briefly here. A detailed post will be dedicated to each one. I will translate al-Jazari’s text and explain my modern interpretation. I will discuss what works and what doesn’t. I would be delighted to receive questions, comments, or suggestions for improvements. If you have any suggestions, I promise to try them and report back on what happens, as well as any progress made.

1. The (original) elephant is made of copper. Partitions were installed in its belly, and it became a hidden water reservoir. A float with a hole(طرجهار)    was placed in that reservoir and slowly sank. This is the core of time measurement. In Al-Jazari’s book, the sinking time is half an hour.
2. On the float rests a weight attached to a pulley. On the pulley’s axis sits a scribe holding a pen. When the float sinks, the weight sinks with it, causing the scribe to rotate and its pen to indicate the passing minutes.
3. The clock’s energy source is metal balls stored in the ball channels. The height difference enables the clock’s cyclical operation. After half an hour, when the float has finished sinking, the chain pulls the channel. This causes a metal ball to roll down and start its journey, and a new ball takes its place.
4. The ball falls on a wheel of slanting blades attached to the bird and causes the bird to rotate.
5. The Circle of Hours – This is the heart of this post. The purpose of the circle is to show the passing of time. Above the Falconer are fifteen round windows. At sunrise, all the windows are darkened. Every half hour, half of a window becomes silver color. So, the number of silvered windows represents the hours that have passed. This mechanism is explained in full below.
6. The ball falls from the wheel of slanting blades area to the “selector” mechanism, which chooses whether the ball will fall once to the right dragon and once to the left dragon, and accordingly tilts the Falconer. I couldn’t find a solution in Lego for the Falcon heads, and therefore, the balls come out of a simple opening.
7. The ball falls into the dragon‘s gaping mouth. The extra weight causes the dragon to flip and pull the float back to the surface of the water. When the dragon reaches the bottom, it releases the ball into the vases that lead to the mahout (elephant rider and trainer) mechanism.
8. From the vases, the ball rolls through pipes to the mahout It falls onto a swing that is attached to the mahout’s arms, causing the mahout to hit the elephant’s back with a hammer and a mallet.

The mechanism of the wheel of hours

The text is the English translation by Dr. Donald Hill. I slightly modified the original text.

“One takes a fine ring of silver, its diameter the same as the diameter of the circle of holes, its width the same as the diameter of one hole, and a little more than that. For half of it, the silver is blacked over. Then, a copper disc of the same diameter is laid on the back of the silver ring and firmly soldered to it.

An axle is fitted to the center of the disc, which does not penetrate the face of the castle. The ring now covers the holes, and when it rotates, it does so with ease.

Then, on the perimeter of the disc, 30 teeth are fitted at right angles to the circumference. Each tooth has the shape and the length of a barleycorn, and they are equidistant from one another.

Let the black half cover the holes, the white half being underneath. Now, two links are taken and connected by a pin to form a hinge in such a way that when one rotates about the other, there is no restriction in one direction, but in the other direction, it cannot rotate and remains colinear. One link is longer than the other. In the longer link, an axle is fitted crosswise, near the hinge pin, on the inflexible side:

On the longer link is a و, on the shorter an ه, and on the two ends of the axle م م

Then, the end of the short link is placed between the first and second teeth of the disc, and the end of the long link is beneath the end of the moving channel. The ends of the axle are placed in two firm bearings, one in the right-hand plate of the castle, the other on a crossbeam which does not impede the movement. The flexible side is uppermost, and the non-flexible side is underneath. Now, I say that when the ring at the end of the moving channel is pulled down a set distance, it is prevented from descending below the set distance. Then, the end of the channel forces down the end of the long link و , which descends by a known distance, while the end of the short link ه rises by a known distance. Therefore, the tooth at the end of the short link rises by a known distance – namely half the diameter of a hole. The disc moves, and the white part of the ring rotates over half the first hole. When the moving channel returns to its position, its end lifts from the end of the long link, that light end rises, and the end with the pin in it descends. This end is weighted with lead and, therefore, sinks due to its weight. The short link comes out from between the first and second teeth and enters between the second and third. This happens every time the ring at the end of the moving channel is pulled.”

Fig 58.The Book of Knowledge of Ingenious Mechanical Devices translated and annotated by Dr. Donald Hill.

The Circle of Hours – The Lego Elephant

The round holes are replaced with transparent Lego blocks:

The facade of the castle from the manuscript (Topkapi 1206) compared to the facade of the castle from the Lego elephant

Al-Jazari’s disk with the silver ring has been replaced with a 3D-printed disc. In different manuscripts, the shape of the teeth that Al-Jazari describes as “barley grain” is different. The drawing below is a comparison between the printed disk and a drawing from a 17th-century manuscript of the book:

The lever that is supposed to rotate the hour wheel one tooth at a time looks like this:

The front can rotate freely, as shown in the photo:

In the front link, three lead balls weigh about 0.4 grams. This is enough to cause it to fall unless something pushes it upwards, but this does not happen during regular operations. To clarify the problem, a short video is attached:

You can see that when the end of the long link goes down, the end of the short link goes up as al-Jazari planned. The short link pushes the tooth, the hour circle rotates, and the silver half-ring covers the first transparent brick. But when you let go of the end of the long link, it rises, and the short (heavy) link sinks, but contrary to what is written, it does not come out between the first and second teeth but gets stuck in the second tooth and pushes it back down in the opposite direction of rotation?

I’m unsure whether there’s a problem with al-Jazari’s original design or with my implementation, and I would appreciate any suggestions or assistance.