What are the major advantages of the Egyptian Pulley?
The pullers are positioned on top of the pyramid-in-construction, on a flat, stable surface. The Egyptian Pulley provides for efficient redirection of the pull rope and application of a concentrated (pull) force. The Egyptian Pulley's rope groove protects the rope as it is being redirected by preventing rope slippage (and related abrasion) and rope distortion, thereby maintaining integrity of the rope's "twist" structure (and examination of ancient Egyptian rope reveals it to be relatively fragile compared to modern, machine-made manila rope). As such, the Egyptian Pulley operates just like a conventional pulley but, for the same sheave diameter, is much stronger because the Egyptian Pulley has no (conventional) axle (under a bending load), i.e., essentially all loading in an Egyptian Pulley is compressive (confirmed by finite element analysis). Of course, for the same size, the Egyptian Pulley is much heavier, but this is an advantage for the application proposed, by providing stability. Also, the design of the Egyptian Pulley makes it easier to mount to a foundation than a conventional pulley.
Could the rate of one stone block lifted every five minutes been achieved?
Yes. Analysis shows that sixty five pullers positioned on top of the pyramid-in-construction could have easily pulled a 5,000 pound stone (on a wood sled) up the side of the pyramid-in-construction. For example, with teams of pullers using six Egyptian Pulleys, allowing 30 minutes total to lift one stone per Pulley, six stone blocks could have been lifted in 30 minutes -- averaging one block every five minutes. The pull itself would have been done quickly, less than a minute, without stopping -- to avoid static friction and loss of momentum. As soon as a stone lift was initiated another stone could be readied for the next lift; therefore, the total lift time for each stone was essentially only the time required for the lift and the unloading.
Also, multiple lift points around the base of the pyramid during construction would have eliminated stone "traffic jams" -- compared to single avenue lift schemes such as a single ramp. As required, Pulleys could have been quickly repositioned as the the two Pulley components weigh only about 80 pounds each.
Further, such an arrangement of multiple pulleys provides inherent redundancy in the event of a single Pulley or rope failure.
Was there enough room on top of the pyramid-in-construction for the number of pullers needed to meet the rate of stone lifting (one stone every three minutes)?
Yes. With 65 pullers manning two Egyptian Pulleys (there would be time to man two Pulleys between each pull as the next stone is being prepared), only 195 pullers would be required to man six Pulleys. For example, at 250 foot height (and 133,225 sq. ft. top surface area), 195 pullers would occupy less than 5% of top surface area (assuming 20 sq. ft. per puller). Only at greater than 300 feet height does linear distance (for a straight line rope pull) on top even start to become an issue, but this is at about the same height the weight of stones is known to decrease. Is this simply a coincidence?
Did the Old Kingdom Egyptians have strong, long rope?
Yes. The ancient Egyptians were the first great rope makers. Coils of well-made, long rope were discovered at the site of the Great Pyramid (adjacent to the Great Pyramid, where Khufu’s ritual boat was discovered). Ancient Egyptian wall reliefs often depict the use of large ropes, including one showing 172 men using rope to pull a 58 ton stone statue on a wood sled. The Old Kingdom Egyptians understood rope rigging, including knotting and cinching rope under significant loads, for example, to temporarily hold heavy stones in position. They were expert in handling and moving huge stones using rope.
Could the Old Kingdom Egyptians have fashioned hardwood, granite, limestone and copper into high strength Egyptian Pulley rollers and cradles?
Yes. These materials were common in Old Kingdom Egypt. They fabricated finely sculpted, polished objects (with shapes much more complex than cylinders) of limestone and granite. And, of course, they erected huge limestone and granite columns made of cylindrical segments. They knew how to make complex objects of copper by the "lost wax" (investment casting) process.
Weren't the sides of the Great Pyramid too rough to pull the stones over?
The surface of the Great Pyramid as it now exists is misleading. In fact, all the smooth, outer finish stones have been removed (scavenged over the years). Further, most Egyptologists believe those original finish stones were put into position as the Great Pyramid was being constructed, thereby providing a smooth surface over which to pull up the stone blocks (which likely would have been on wood sleds). Also, it possible that temporary wood “rails” could have been placed on the sides of the pyramid-in-construction, over which the stone blocks on wood sleds could have been pulled. Further, available lubricants (such as flax oil and rendered animal fat) would also have likely been used.
How were the stone blocks unloaded at the top?
Several techniques can be imagined, perhaps the simplest involves a temporary locking "key," holding the Pulley in (horizontal) position, which is removed as the stone/sled reaches the top edge. The stone/sled is then simply pulled over the edge and the Pulley transitions horizontally, in the direction the rope is pulled (see sketches on Photo and Sketches page).
Near the top, during thelast stageof construction, with relatively little surface area available, how could the Egyptians have lifted the stones using the Egyptian Pulley?
By using an additional Egyptian Pulley at the directly opposite top edge, with the pull rope going both Pulleys, a "counterweight" (positioned directly below this additional Pulley, i.e., on the slope opposite the stone) could have been used to lift the stone. Workers could have brought relatively small stones (e.g., fifty pounds) to the top surface and loaded enough of these into an open box (attached to the pull rope) until a sufficiently heavy counterweight was achieved to pull the stone up the opposite slope. Or alternately workers themselves could have been the counterweight, by getting into the open box and, using their combined weights, lifting the stone. For example, to lift a 2,000 pound stone (smaller stones are known to be near the top), only about fifteen men, i.e., as counterweight, would have been needed. See Photo and Sketches page.
There are much heavier stones than 5,000 pounds inside the Great Pyramid. Could the Egyptian Pulley been used to lift those stones?
Yes, simply with the use of heavier ropes and more pullers. Also, see the Advanced Pulley Arrangements page -- which shows a "tandem" Egyptian Pulley, the use of which would have reduced rope stress.
What evidence is there that the Old Kingdom Egyptians actually designed, fabricated and used the Egyptian Pulley?
The best evidence is in the Great Pyramid itself. Egyptologists have now identified the remains of a primitive pulley system, composed (originally) of ropes, cylinders (i.e., logs) and limestone cradles (see Photo below) on which the cylindrical logs rotated, to foil tomb robbers in the Great Pyramid; cylinders and cradles are indeed the two components of an Egyptian Pulley.
Further, a 14 inch (axial length) "rope roll" (see Photo and Sketches Page, Sketch 5) with a center rope groove was found at the site of the Step (Djoser) Pyramid, which predated the Great Pyramid by more than 100 years. It is described and illustrated in a 1936 French text about the Great Pyramid (provided on the Photo and Sketches page section of this website). This rope roll looks very much like the Egyptian Pulley cylinder. Similar rope rolls, from the subsequent Middle Kingdom, are in the Petrie Museum Collection (London).
But, to date, no one has searched (i.e., through simple observation) specifically for evidence of Egyptian Pulley components at Egyptian archaeological sites. People may have seen Pulley components but not recognized their function.
Were the Ancient Egyptians clever enough to have conceived of the Egyptian Pulley?
Absolutely. They were as intelligent as humans today. And detailed study of the Great Pyramid only increases one’s amazement at their capabilities. In summary, the Egyptian Pulley would have been obvious to the Old Kingdom Egyptians.
Inside the Great Pyramid
Recent, close-up photo of one of the limestone cradles just outside entrance to the King's Chamber