Energy and machines in Antiquity (Part I)

Here we present the same-titled Chapter from the book ‘Ancient Technology’, by John W. Humphrey (Greenwood Press)

Contrary to what is often believed, the ancient Greeks and Romans— and to a lesser extent the earlier Egyptians and Mesopotamians—possessed a great many mechanical devices: by the classical period they were familiar with levers, pulleys, rotary systems, steam and hydraulic power, gears and gear trains, and even complex pumps and valves.

Sources of Energy

One of the most severe restrictions on technological progress in antiquity was the use of a very limited variety of energy sources: human power and animal power were the most significant, while water and the wind were used for only a few specific applications.
Human power was employed either alone in a great number of tasks (hauling two-ton blocks for the pyramids), or in connection with various mechanical devices like the winch or lever (propelling warships by oars, for example). These devices allowed people to transmit power over a short distance, to change the direction of the power, or to multiply it through mechanical advantage. But humans in fact can produce only a
small amount of usable power: it is estimated that a single person on a treadmill can put out about 0.1 hp.

After animals had been domesticated in the Neolithic Age first as a food supply, they later came to be used as a source of energy, either as beasts of burden and draft animals or to power mechanical devices. In the Mediterranean region oxen were most commonly used for such purposes, since they were economical if slow; the horse (always considered
a noble beast) was used only for transporting light loads (like cavalrymen); while donkeys and mules were assigned to pulling carts and turning rotary mills.

Moving water as a source of energy was never widespread in the ancient world: such a power supply requires a year-round and regular flow of considerable speed and quantity, something that is not common in most of the Mediterranean region. Waterwheels, for example, were apparently seldom used until about the first century B.C.E., when Vitruvius described the wheel used to raise buckets on a chain and—through toothed gear wheels—to grind grain. It was hardly more efficient than man-power: depending of course on its size and the speed of the stream below its vanes, it could produce 0.05–0.50 hp; the more efficient but costly ‘‘overshot’’ wheel could put out perhaps 2 hp.

Neither wind power nor steam power was taken seriously in the ancient world. The former was used almost exclusively for propelling ships; and, though Hero of Alexandria described a windmill connected to an air pump designed to blow an organ, there is no evidence for the existence of any rotary windmills before the tenth century C.E. Hero also designed a workable steam engine, but it had a low torque and was very inefficient (it has been estimated that the machine required 25,000 BTU/hour to produce 0.1 hp, the output of a human). One of its principal limitations was the absence of a cheap, efficient, and portable source of heat: though coal and petroleum were recognized in antiquity, only charcoal was extensively used, in pottery kilns and smelting furnaces, for
example.

(End of Part I)