Energy, Work and Transportation in Ancient Rome and Greece

Lecture 16: Harnessing Animal Power – Land Transportation

Understanding Greek and Roman Technology: From the Catapult to the Pantheon

Dr Stephen Ressler (2013)

Film Review

Ressler spends the first third of this lecture explaining the engineering concepts of  machine, work and power.

Machine: assembly of moving or fixed parts used to perform work.Work: quantity of energy expended when a force moves through a distance.Power: rate at which work is down.

Humanity owes our concept of simple machines to the third century BC Greek mathematician and inventor Archimedes. Although Archimedes didn’t invent the lever, pulley and screw, by deepening our understanding of their operation, he helped expand their usage.

Lever – a simple machine that magnifies applied force.Pulley – a simple machine that changes the direction of applied force

Screw –  a simple machine that converts rotational force (aka torque) to longitudinal force.

The Greeks and Romans employed three other simple machines not described by Archimedes. All were in wide usage before the classical period.

Wedge – a simple machine that converts a singular force into two opposing forces directed perpendicular to the wedge surfaces.

Inclined plane – enables the lifting of an object with less force than its weight.

Wheel/axle – allow an object to be propelled with minimal force.

Land Transportation

According to Ressler, there were four main sources of power in ancient Greece and Rome: human beings, animals, water and wind. A mule has five times the power of a human (performs work five times faster), a mule seven times and an ox ten times. Although usually limited to pushing, pulling or carrying heavy burdens, wagons or plows, animals were occasionally used to power grain mills. Water power was used to mill grain and pump water and wind was used to sail ships.

Human porters can only carry 50-60 pounds for no more than a few yards. For heavy loads Greeks and Romans used donkeys (can carry 200 pounds) and mules (can carry 300 pounds). To carry heavy loads long distances, it’s more efficient to load them onto wheeled vehicles pulled by a team of animals.

Both Greeks and Romans commonly used two-wheeled vehicles to carry people.

Greek warrior chariot

Greek homoxa – could carry four peopleRoman racing chariot

Essedum – Roman two seat passenger cart

Both Greeks and Romans used four wheeled vehicles drawn by pack animals to transport heavy loads. The Romans also had a four-wheeled passenger carriage.

The wheel was invented around the 4th millenium BC, and there is archeological evidence in the Near East of 3rd millenium military chariots with spoked wheels.

The Romans used solid wheels (for their simplicity and strength) for oxcarts and massive siege engines

Spokes – the Greek warrior chariot (see above) used unique crossbar wheels or spoked wheels with up to 10 spokes. Borrowing the design from conquered Celts, the Romans used wheels with up to 21 spokes.Axles – the Greeks and Romans used two types of axles. The first fixed the axle to the cart and allowed the wheels to move independently, the second fixed the wheels to the axle. Ressler demonstrates with scale models how the first was more maneuverable but caused greater wear on moving parts. He also demonstrates how the Romans reduced wear by fitting their wooden axles and wheels with thin iron sleeves.Traction systems – owing to docility and strength, oxen were pack animals of choice for both Greeks and Romans. The yoke used to connect them to a cart or wagon was first developed during the neolithic period and is still used today in the Third World. It consists of a heavy beam fitting over the animal’s shoulders and held in place with a harness. It’s connected to the vehicle with a single draft pole. Greeks used a similar traction system for the donkeys and mules that pulled their hamaxa.

Film can be viewed free with a library card on Kanopy.

https://www.kanopy.com/en/pukeariki/watch/video/146678/146710