As four MechSE seniors stood around a lubricated cylinder, roller, and rope in preparation to test their version of an Egyptian Pulley, they were about to find a potential answer.
May 2013 graduates Gabe Gaeta, Yi-An Liou, Caleb Gray, and Neal Jacobsma, members of the Egyptian Pulley Senior Design Project (ME 470) team, successfully proved their model was effective at a testing site in Alton, Illinois this spring. They took on the project after their sponsor, Stephen Blakely (BSME ’69), pitched the idea that while Egyptians may not have had the iron axle in the Early Bronze Age, they could have used an earlier version of a pulley.
In the team's model of the Egyptian Pulley, a roller sits inside the cradle, both finished with sealant, and the rope rests in the roller's groove, which is used to lift an object on the other side of the pulley. Lubricant is added to facilitate movement between the roller and cradle. The project’s goal is to design a pulley that can pull a 5,000-pound block up a 52 degrees incline by using static and dynamic stress analysis. A successful test indicates that man power—about 70 to 80 people—and the pulley may have been responsible for the construction of the Great Pyramid.
"A lot of the current theories, the community does not agree on as a whole and this is largely due to the simple technology Egyptians would have had to use," Gaeta said. "The operation had to be fast and reliable."
To find the materials for a pulley that would produce a “fast and reliable” operation, the team ran stress analysis tests. Egyptian Pulley members opted for high quality limestone when tests revealed that it could withstand a heavier load.
"We wanted to assess the logistics of the pulley to see how it would have worked and see if there are any logistical challenges, if they could be overcome," Gaeta said.
They used half of a 12-inch by 24-inch cylinder-shaped, high quality limestone to use as the roller. Then, they added a grove about 1.5 inches in diameter and deep enough for the rope to sit inside the roller. To ease movement of the pulley, the team used olive oil, a time-appropriate material to lubricate between and seal off the limestone roller and cradle.
"They would have used olive oil or linseed oil," Gray said. "They also had the coating that we are using, which is natural resin, which they had to seal parts of the mummies."
After the team had the components for the pulley ready, it performed stress analyses to ensure that the model would logistically work and withstand the load that it had to carry.
"We have the cylinder, groove, and we had to determine the coefficient of friction between the limestone cylinder and the cradle because we need to figure out the force," Liou said. "We used a force meter and pull while it is lubricated, inside the cradle."
With testing, the group had three goals:
1. To make sure that this pulley would withstand the forces of a 52-degree incline and about 5,500 pounds of tension in the rope.
2. To achieve dynamic analysis.
3. To ensure that the pulley remains stationary as the rope is pulled.
At the site, a forklift pulled the rope down a ramp with a weight of 6,000 pounds. The team placed a force meter where the weight and rope met to measure the tension and factor it into the weight the pulley lifted. Ultimately, the team accomplished a test of just under 4,600 pounds with tension at a 50 degree angle, only two degrees off from the project’s original goal.
"The closer the block got, the larger the angle got," Jacobsma said. "It started at 30 and we got to a 50-degree angle, which is right about where we wanted it."
Two possible solutions the group offered were employing a shaduf, used by Egyptians to lift water, to lift the block over and onto the structure or using a sledge to pull the block up the side of the pyramid and onto the flat surface of the pyramid.
However, the team encouraged their sponsor to continue working on the Egyptian Pulley project and to look into the concept of a smaller pulley using high quality limestone or a two-pulley system.
"From an engineering standpoint everything was within the scope of the project," Gaeta said. "The technology has proven thus far to be plausible."
ME 470 students work in teams to find solutions to a range of problems that manufacturers and service industries encounter. Illinois students have already presented 200 companies with over 950 innovative designs as well as manufacturing, quality control, and product delivery recommendations.