The pump and the Crankshaft

Introduction

The fourth machine for raising water is a pump based on a slider-crank mechanism. A more detailed explanation about crank, its history, and why is it interesting will follow. Since the drawing by al-Jazari is difficult to understand, I will present the revised drawing by Dr. Donald R. Hill, The book translator, and annotator. This is a good opportunity to write a few words about Hill, who was instrumental in bringing this book to us and in understanding al-Jazari and his importance to the history of Engineering.

Machine for raising water from a pool, Chester Beatty Library in Dublin probably 15th century from Iran or Iraq

Donald Rutledge Hill (1922-1994)

Hill was born in London. He joined the English army engineering unit during World War II until he was wounded in action in Italy. Back in England, he studied Engineering at the London University, obtaining his engineering degree in1949. He later worked for the Iraq Petroleum Company in Lebanon, Syria, and Qatar. Hill was gifted in languages, and before arriving at the Middle East, he was already fluent in French, German, Spanish and Italian. The move allowed him to add spoken Arabic but also to master literary Arabic. In 1964 he completed an M.Litt in the history of Islam and 1970 a Ph.D. from the University of London. His impressive accomplishments are a result of the unique combination of engineering knowledge and mastery of Arabic as well as Orientalism at its best, the study of the Arabic culture rather than a romantic perception or in contrast to the West. His main contributions are the translations of “The Book of Knowledge of Ingenious Mechanical Devices,” by al-Jazari, which is the sole purpose of this blog. He also translated the “Banu Musa” mentioned here more than once, and “On the Construction of Water Clocks” attributed to Archimedes. His contribution far exceeds the traditional role of a translator and includes annotations, drawings and writing several books on the history of engineering and technology that helped reinstate the technology in the golden age of Islam to its proper place.

How does it work?

The technical explanation, as always, will be colored in blue, so anyone who is not interested in Cranks (Are you series? Without Cranks we would not have locomotives or cars!) Or toothed wheels can skip those bits

An ox, in the upper room, is rotating the system. If you are confused after the fake cow, in the previous post, this is an actual animal, and without it, the pump would not work. The part of the gears and the conversion of the rotary movement to a linear one is difficult to understand (for me and others), and it looks like al-Jazari drawing is in error. I bring side by side the original illustration by al-Jazari and the drawing by Hill, and I added captions.

Combined drawing, al-Jazari, and Hill

The Ox, in the top room, rotates the horizontal tooth-wheel, which in turn rotates a vertical tooth-wheel, much like the classic sāqīya already explained here. The difference is that the vertical tooth wheel is attached to a slider-crank. We met this mechanism in the water wheel pump where it converted circular motion to linear motion and possibly vice versa. This is an essential component in engines and pumps till this very day. This is an animation of the pump, and you can see the slider-crank mechanism clearly:

It is easy to see that when the wheel rotates the crank moves within the slot and since the ladle is anchored at the axle it will raise the water and empty them later. In al-Jazari drawing( in contrast to the text which is quite clear) it seems that the vertical tooth-wheel is in 900 and the crank is in an odd angle relative to the slot. Hill’s drawing is correcting all these problems and explains well how it worked. Large engines are usually multicylinder to reduce pulsations from individual firing strokes, with more than one piston attached to a complex crankshaft:

Flat-plane crankshaft (red), pistons (gray) in their cylinders (blue), and flywheel (black)

Crankshaft

Many internet sites consider the crank as an invention of al-Jazari, for example here:

“In 1206, al-Jazari invented an early crankshaft, which he incorporated with a crank-connecting rod mechanism in his twin-cylinder pump. Like the modern crankshaft, al-Jazari’s device consisted of a wheel setting several crankpins into motion, with the wheel’s motion being circular and the pins moving back-and-forth in a straight line. The crankshaft described by al-Jazari transforms continuous rotary motion into linear reciprocating motion and is central to modern types of machinery such as the steam engine, internal combustion engine, and automatic controls. “

Before I expand a little on the evolution of the crank, it is important to note that the concept of an individual inventor is, in most cases, excessive romanticizing. It is inordinate when we have a definite inventor and more so for the Middle Ages or before that.  Take, for example, James Watt, who invented the steam engine in 1769 and issued a patent for it. A few children’s books suggest the idea of the steam engine came at the age of 12 while young James sat in the kitchen with his aunt, staring at a teakettle. The water was boiling so hard that the lid of the tea kettle began to jump up and down. This is simply not true. Watt invented the steam engine while fixing Newcomen’s steam engine for the University of Glasgow. This engine was invented in 1712 and was considered a great success. More than 100 such engines were installed as water pumps in mines in England and Wales. Also, the Newcomen engine is not the first steam engine, and there are predecessors from the 16th and 17th centuries. Don’t get me wrong, James Watt is entirely worthy of his glory, his improvements (the separate steam condenser and later the double-action engine) were very significant and the industrial revolution, for better or worse, is the consequence of the improvements by Watt.

The electric light bulb was invented by Edison, and the airplane was invented by the Wright brothers, but their story is not very different from the story of James Watt. Without diminishing their impotent contributions, their inventions, just like Watt’s steam engine, are a link in a long chain.

Manual cranks appeared in China during the Han dynasty (202 BC-220 AD), and we find ceramic models in the tombs of the period. However, the potential of the crank of converting circular motion into reciprocal motion never seems to have been fully realized in China. There are manual cranks examples from Europe and the Middle East. For example this picture of Roman iron crank for an unknown purpose from the 2nd century AD

roman crank

A Roman iron crank dating to the 2nd century AD was excavated in Augusta Raurica, Switzerland.

The crank appears in the book by the Banu Musa from the 9th century, which al-Jazari new and quoted. However, in their version, the crank did only a partial rotation which wouldn’t allow for significant power transfer.  Al-Jazari did not write, as he did in his fountain [in Hebrew], for example, that he looked at design by the Banu Musa and decided that it requires improvement and does not refer to the originality of his design.

330px-Steam_engine_in_action

Steam Engine, Wikipedia

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