It was new technology that helped Thutmose III to extend the boundaries of Egypt, reaching as far as the River Euphrates in Mesopotamia. And that technology was the chariot – a new form of transportation that could be ruthlessly deployed to expand the empire and defeat Egypt’s enemies, greatly enhancing the military and economic power of the New Kingdom (c.1550-1070 BC).
The success of the chariot was dependent on the design of its wheels. They had to withstand rocky terrain and battle engagements, at speeds exceeding those of people running on foot. At the same time, the vehicle’s occupants needed a ride smooth and stable enough to allow the effective use of bows and lances. The wheels had to adapt rapidly to the stresses produced by two horses, under a yolk and controlled by the charioteer’s reins, pulling the chariot sideways, forwards, and backwards. The wheels had to be easily and quickly repaired or replaced. They had to function in many different climates and terrains, such as the Egyptian Delta and desert, and in mountainous cities like Kadesh in the Levant, which was attacked by Thutmose III, Sety I, and (most famously) Ramesses II.
So how was this remarkable feat of engineering achieved?
The evolution of the wheel
In the 3rd century BC, when the Pyramids at Giza were being constructed, blocks of stone were transported either on a sledge, or on horizontal logs that acted as rollers. The sledge itself could be moved on log rollers, or a box could be used instead of the sledge. This combination led to the creation of a moveable box to which wheels could be attached.
At first, the box-type vehicle had axles the same size as the circumference of the tree trunks from which they were cut. Later, the axles were made thinner to lessen their weight while remaining sturdy enough to avoid breaking under heavy loads. A hole was made in the wheel so that it could be slid over the axle and fastened to it. Initially, the size of the wheel was limited by the circumference of the tree from which it was cut, but later a technique for making larger wheels was developed, using several pieces of wood attached side by side with a hole carved in the centre. This was known as the ‘tripartite wheel’. The pieces of wood were held in place by a rim of copper, reinforced with hobnails, or leather rim bindings. One version of the tripartite wheel was known as the ‘cross-bar wheel’: this had spokes connecting the wheel hub/nave to its rim.
Carts could be constructed in one of two ways: with either a rotating axle to which wheels were attached, or a fixed axle with rotating wheels. It was the latter version that became the model for all wheeled vehicles of the era. It had advantages, such as making wheel-replacement easier (there was no need to replace the axle), but also disadvantages, in that the wheel was weaker than the rotating axle-wheel combination and more likely to fracture.
However, ancient Egypt’s precise role in the development of the wheeled cart is difficult to determine, as similar carts were in use across the Near East, Anatolia, and the Mesopotamian civilisations of Ur and Susa.
From wheeled cart to chariot
Eventually, some of the wheeled carts developed an axle, spoke, rim, and tyre, which resembled that of the earliest pharaonic Egyptian chariots. Queen Ahhotep’s wagon is one such example, with four spokes radiating from a central hub. Two spokes were formed from one piece of wood, which was steamed and bent into a ‘V’ shape, suitable for inserting and binding into a notch in the hub/nave. This method was chosen to strengthen the spoke connection to the hub, and because of the scarcity of suitable wood (such as ash) in Egypt.
The Eighteenth Dynasty chariot wheel
The earliest chariots in the New Kingdom appeared in conjunction with the expulsion of the Hyksos from Avaris and the Delta in c.1550 BC. The conquering pharaoh Ahmose took the Hyksos chariots as booty, using them to launch a military, political, and economic expansion of Egypt. Horses were imported to draw these chariots, as they were faster and more reliable than the cows or donkeys used to pull agricultural or other wheeled transport. The horses were bound to the axle and chariot box by a yolk. The viability of this horse-drawn conveyance depended on the strength and durability of the chariot wheel. If the horses reared, fought, were spooked, or turned too rapidly, the forces on the wheel would increase. This would make it vulnerable to breaking, causing the chariot to overturn, expelling, or even killing, its occupants.
Manufacture of the chariot in ancient Egypt was probably aided by the availability of many examples that could be copied, including those of the Hyksos. By the beginning of the Eighteenth Dynasty, chariot war-machines were being used in the Hittite Empire in Anatolia, among the Canaanites in the Levant, by the Mitanni (heirs of the Akkadian and Sumerian kingdoms), and by groups in Eastern Europe in the Ural mountains. Thutmose III reports bringing back 900 chariots from Megiddo as booty, and perhaps these were recycled into the Egyptian army. By the reigns of Thutmose III and Amenhotep II, a chariot-building workshop had been established in Thebes, and later one was set up in Amarna (c.1346-1341 BC).
The chariot wheel’s structure
The chariot wheel had to function in many conditions, for example on roads, in battle, in processions, and on wild animal hunts. This required all of its components to work together to keep the wheel from fracturing or becoming detached from the axle.
The hub or nave
This was the most complex component, as it had to fit over the fixed axle without becoming detached, and rotate efficiently forwards and backwards at slow and fast speeds. The wheel had flanges or extensions on both sides: on one side to keep it from rubbing against the chariot box, on the other to make it stable on the axle. This latter function required several adaptations.
As both the axle and hub were made of wood, lubrication was needed to keep them from splintering or bursting into flames when the wheel rotated. This was accomplished using animal fat. The flanges, also wooden, were mortised on to the wheel and extended out on the axle. Since the wheel could become wet from groundwater, the nave/hub required a water- resistant cover, sometimes made of leather, cloth, and gesso (a mixture of plaster and glue), covered over with gold foil, as is visible in a preserved Tutankhamun chariot, and sometimes made of metal, as suggested by excavations near Qantir in the Delta.
There were several options to prevent the wheel from detaching. Some chariots had a nave hoop (a metal ring) at the end of the nave/hub. The vehicles often had a linchpin made of metal or leather, and, in some cases, possibly a cap on the distal end of the axle. The linchpin fitted through a hole drilled in the axle. A hole in the lower part of the linchpin was used for a leather or cloth strap that was tied on the axle.
The spokes were of wood bent in a V shape, as described above, and glued and wrapped in the notches made in the nave/hub. The wheels of the earliest chariots had four spokes, but later ones mostly had six, which provided more stability for their occupants.
Felloes were curved pieces of wood with mortices, into which the outer ends of the spokes were set. The mortices and spokes were then wrapped and glued in place. When all of the spokes were in place, the felloes were held in a circular shape by a surrounding rim.
These were wooden pieces attached to the outside of the felloes and moulded into a circle to form the outer surface of the wheel.
Some chariot wheels had only a wooden rim that acted as a tyre (defined as the part of the wheel that came into contact with the road). In other chariots, the wooden rim was covered by a cloth or leather tyre. One of Tutankhamun’s royal chariots had a tyre of gesso wrapped in gold foil. Hobnails and copper rims functioned as tyres in Ur and Susa, but did not appear in Egypt. Iron tyres surrounding wooden rims were not used until around 900 BC and were problematic, with a tendency to detach due to wheel shrinkage and fracturing caused by variations in temperature.
Depictions of the chariot wheel and box
I have examined the dimensions of the six extant Eighteenth Dynasty chariot wheels and their carts, and compared them to 53 tomb paintings, inscriptions, and depictions on funerary objects. In all cases, the diameter of the chariot wheel looks smaller than in life in the artistic representations, while the height of the chariot box is shown larger than in reality. There are at least two explanations for the discrepancy. First, the chariot occupants wanted to appear as prominent as possible, and a larger chariot box would have drawn attention to them rather than to the wheels. Second, in the depictions the height of the side of the chariot box is in a 2:1 ratio with the diameter of the chariot wheel. This provides a formula for sketching out a chariot box/wheel combination that avoided the need to calculate their dimensions individually. The time saved in completing these sketch parts would have been considerable, especially in paintings or carvings of chariot battle scenes.
Ancient Egyptian chariots continue to interest scholars today, and there have been two projects attempting to create a working replica (one of which was part of an experiment to determine if Tutankamun could have been killed in a chariot accident). The chariot wheel without doubt played an essential role in the military, economic and cultural growth that made Egypt the most powerful empire in the ancient Near East for at least 500 years.