Ancient and Modern Theory on Pulley Systems: A Case Study on Cranes and the Killer Animal Elevator

By Amelie Ingram

1. Introduction

When first arriving in Rome, the average tourist might be blown away by the pure number and size of ancient structures. They probably wonder how the Ancient Romans were able to build such long lasting structures. What they probably don’t realize is how much of what they are seeing is the product of trial and error and pure experiential learning. While walking through the Pantheon, Colosseum, Baths of Caracalla, and so many other sites that contain large arches and walls over 30 meters high, I couldn’t help but picture all the calculations and planning that must have gone into the creation of these massive structures. When touring the Colosseum, our tour guide started explaining how little they knew about our current physics and mathematics at the time. I found this completely fascinating. In this paper I plan to examine a case study of ancient pulley systems as a comparison between their methods of innovation and our current use of Newtonian physics for similar purposes.

The ancient Romans like many other civilizations did not begin from scratch. They based the creation of their society around inherited knowledge from past civilizations: the Greeks, the Egyptians, and of course the Etruscans who were the previous inhabitants of the Italian peninsula. Eventually as Rome grew in strength, they adopted the Etruscans into their society, providing them with Roman citizenship while also adopting much of their culture. However, when you look at ancient Roman culture and structures it becomes glaringly obvious that the Greeks were their main inspiration. The Romans were not just inspired by Greek culture, but rather infatuated with their fashions, architecture, and societal structure. The Romans emulated Greek democracy, as well as their use of certain architectural principles like the use of columns (Luca Colosseum tour). Due to this obsession with Greek culture, the Romans also gained much of the Greek knowledge of philosophy and science. Much of ancient Roman knowledge about our natural world was developed from the teachings of Aristotle and Plato who developed a strong base for our current knowledge of arithmetic and geometry (Fisher, 2015).

1.1 Background of Ancient Roman Physics

In modern analysis of ancient Roman structures we see the complexities of Newtonian physics everywhere. The principles of mechanics and kinematics can be seen in how arches were used to reduce loads and increase the height and strength of Roman engineering. It is easy for one to assume that the ancient Romans had this knowledge when creating these structures, but there is a large historical separation between Ancient Roman times and the beginning of Newtonian physics. The fall of Rome took place around 476 AD and Issac Newton was not born until the 17th century. Newton was primarily responsible for most of our current understanding of calculus, as well as our definitions of the forces that define our natural world. However, the Romans were not completely unknowledgeable in these areas. From the teachings of Aristotle, the Romans had a working knowledge of geometry and the proofs behind triangles, lines, and basic arithmetic. Aristotle ranked different areas of science and mathematics at the time based on their precision (Fisher). He defined subjects like geometry as a high precision area because everything he is studying and defining is stationary. However, he ranked mechanics as a low precision science because he did not yet have a way to describe moving objects and forces the way we do today (Fisher).

There was also a large connection between philosophy and science. While gravity was not accurately defined until much later on, Aristotle described observations he made of the natural world. He explains gravity by saying that the four basic elements have a natural tendency to move towards the center of the Earth (Mendell, 2004). He may not have understood why this force happens or how to apply it to engineering or his discussions of mathematics, but he was able to observe these natural phenomena.

1.2 Construction Planning

Another important consideration when looking at Roman feats of engineering is looking at who was responsible for building and planning these structures. The average citizen in ancient Rome did not have extensive education and had very limited knowledge of mathematics, yet it was slaves, armies, and some employed workers who were responsible for the creation of these structures. While most of the credit was given to the Emperor or other popular figure who paid for these projects, it was not the elite who were planning and constructing these structures. Therefore the workers had to use a trial and error system to determine what does and does not work in engineering. If they built a structure a certain way and it collapses, they know they must change the foundation or material for the next attempt. They did not have the computer programs or even basic physics understanding to create a mathematical model for these structures, but rather they based their methods on observations and trial and error. There is a very interesting result of this method of engineering which immediately caught my interest on the tours we took, which is how the Romans formed unintentionally strong structures (Luca Colosseum Tour). Today when engineers are planning a building or some other form of infrastructure, we calculate exactly how strong a structure must be in order to hold a certain weight or perform a certain purpose. Then we add on a buffer amount of extra strength so that the building will hold. We are much more economical in how we approach these projects. We look at the price of materials and labor and then decide to make the engineering approach as cost effective as possible. Since ancient Romans did not have the ability to calculate the minimum strength needed, they ended up making structures that could hold much more weight than would ever be necessary for them.

The role of the architect as a professional undertaking emerged during the Roman Empire. Our main remaining source of information on architecture from this period is De Architectura, written by architect and military engineer Vitruvius (Bani-Masoud). Vitruvius defined architecture to be a science relating to both liberal and mathematical areas of study. In his writings, Vitruvius defines nine essential areas of study for masters of architecture: writing, drawing, geometry, history, philosophy, music, medicine, astronomy, and law (Bani-Masoud). Of course looking back historically we know that very few architects or workers at the time had this wide breadth of knowledge that Vitruvius expected of the profession. Vitruvius also made an interesting distinction between fabrica which he defines as practical experience and raciocinatio which he explains is the intellectual side of architecture (Bani-Masoud). Most engineers and architects, as well as slaves and workers, gained their knowledge through the former method, by trial and error. We can see that in the intellectual world a lot was expected of these positions but in reality most of their knowledge came from worldly and professional experience.

2. Pulley Systems

When taking tours of sites like the Colosseum, the Pantheon, and the Baths of Caracalla, I was immediately focused on how the different structures demonstrated balancing forces like gravity, tension, and compression forces. I found it fascinating to learn about how they were able to lift and transport heavy materials from place to place using pulley systems from cranes without a functional definition of gravity or tension. Additionally when touring the colosseum I became fascinated with the underground hypogeum and the system of pulleys that was used to lift animals into the amphitheater. In the next two sections I will discuss how pulley systems balance forces and how they have been used to enhance two very different areas of Roman life: practical engineering uses, and for the enhancement of entertainment in Rome.

Pulley systems were invented by archimedes in Ancient Greece and were mostly used for construction equipment and the earliest forms of cranes like in Figure 2 (Ceccarelli, 2020). The purpose of these simple pulley designs were to redirect weights and lessen loads to make it easier to lift heavy objects when constructing larger structures. Pulley systems use circular pieces with grooves to hold ropes either attached to a fixed spot or a movable rope. These are the two kinds of pulleys: fixed and moveable. These systems use the tension force in ropes to balance out the gravitational force of the weight they are lifting. In order to lift an object in the air the tension force pulling up on the weight from the rope must be larger than the gravitational force in order to overcome the inertia of the object. This means a careful balancing of forces in order to create the desired speed of movement for the weight. All forces must be in equilibrium (net force zero) for an object to be pulled upwards at a constant speed. Archimedes’s goal in inventing these systems was to improve the efficiency and ease of construction.

In a simple pulley system like in Figure 3 below there is a fixed pulley that is attached to a ceiling, wall, or other nonmoving structure. Then one rope is attached to the weight on one side of the pulley and being pulled manually from the other side. In this very simple model the weight is being redirected so that the person pulling can pull downwards instead of upwards for the same desired movement. There is still only one load supporting rope so this system does not actually lessen the force needed to lift the object. The force is still equal to the weight of the object. This system can still make it easier to lift, but does not help much when talking about large slabs of travertine or marble that weigh much more than 500 lbs. The real advantage of pulleys is demonstrated by compound pulley systems in which multiple pulleys are strung together to lessen the force needed to lift the load.

There is one key principle that explains how adding more pulleys can decrease the amount of force needed to lift and that is the work-energy principle. The work-energy principle states that the total work done on an object is equal to the change in kinetic energy (Libretexts, 2020). Work is defined as the force needed to move an object multiplied by the distance the object is moving. If we are moving an object from ground level to say, 10 feet in the air a certain amount of work needs to be done. By adding in more pulleys, we increase the distance that the force is applied over so that less force is necessary (Deziel, 2019). Therefore, it takes less force to move the same object up the 10 feet because more rope is pulled.

A compound pulley system is made of two components, a fixed pulley and a moveable pulley as labeled in Figure 4. The combination of these two types of pulleys in one system allows the force needed to be cut in half (for a system with 2 pulleys). In the figure below, each pulley system contains 4 pulleys and results in a decrease of the load by a factor of one fourth. The left side of the figure shows a basic compound pulley set up. The right side of the figure shows a block and tackle pulley system. Block and tackle pulley systems are a type of compound pulley where more of the pulleys are fixed to gain a better mechanical advantage. Mechanical advantage is equal to the total number of load supporting ropes in the pulley system (Deziel, 2019). This means you do not count any ropes that are just redirecting the force. Mechanical advantage can be calculated by dividing the weight being lifted by the amount of force exerted. For example in the compound pulley system on the left, the mechanical advantage would be:

This means that in order to lift the weight, only ¼ of the force is needed compared to if a person just tried to lift the weight without a pulley system.

2.1 Cranes

Pulleys were used for many purposes during the Roman Empire, but by far the most impactful use was for construction equipment. Rome was a quickly growing empire and a large part of that was their ability to efficiently construct monuments, roads, amphitheaters, baths, aqueducts, temples, and many more structures. The main problem they faced when building these infrastructures was the transportation of materials and lifting large amounts of heavy marble or travertine blocks up to large heights. Think of structures like the Colosseum which at its tallest was about 48 meters high (discoveryrometours). The ancient Romans needed to find a way to lift extremely heavy materials up to large heights, and they needed to do it efficiently in order to keep up with a growing population and a growing demand for infrastructure. Their solution was to utilize the pulley and crane systems developed by the Greeks and make improvements on these systems to maximize efficiency of labor. 

The Romans had many different types of cranes for different purposes. These cranes were mostly made of wood and ropes, so none of these structures still remain today for us to study. Instead historians are forced to use carved depictions of these machines in order to gain a better understanding of the materials, components, and overall process of using them. Figure 5 shows a depiction of an ancient treadwheel crane being used for the construction of a building. Based on the size of the treadwheel and mast of the crane compared to the doors and pillars on the buildings we can see that these cranes were very tall, which allowed the ancient Romans to create such tall buildings. The treadwheel is a human powered structure that rotates as people walk and move along the interior of the wheel (Shapiro, 2007). In the image below we can see 5 figures standing inside the wheel to get it rotating. This a very dangerous job that would have been performed by slaves at the time (Bond, 2018). Then on the left side of the mast we can see many ropes connected to small pulley systems that are connected to the treadwheel in order to haul objects upwards. 

Other ancient Roman cranes used winch systems in order to haul objects upwards (Shapiro, 2007). Winches include a crank that is rotated in order to wrap rope around a spool. This pulls on the rope in order to lift a heavy weight. These cranes were less efficient than the treadwheel cranes, so they were less commonly used for this equipment.

The use of pulley systems for these cranes, as well as the treadwheel and winch systems was a very practical use of the technology. However, they were also used for more cosmetic purposes for the city. One of these purposes was to erect large obelisks throughout the city of Rome. Through various conquests and relations with Egypt, the Roman emperors collected/pillaged 15 obelisks from Egypt, 13 of which are standing today (Dowson, 2024). There are currently more ancient Egyptian obelisks in Rome than any other city in the world, including Egypt. An obelisk is a 4 sided monument with a pyramid shape at the top. They were originally meant to represent rebirth and were placed outside the entrances of Egyptian temples, but when brought to Rome they were meant to represent Rome’s triumphs and conquests (Down, 2007). The first of these Obelisks was taken from Egypt and erected in Rome by Augustus. Now these obelisks are located in piazzas around the city, many of them having been moved from their original locations. All of these obelisks fell down and had to be excavated, except for the Vatican Obelisk which is shown in Figure 6. The Vatican Obelisk was brought to Rome by Caligula in 37 AD (Down, 2007). There are no hieroglyphs on the side of this obelisk so we know very little about its creation and origins in Ancient Egypt. However, we do know from modern measurements that the obelisk is 25.5 meters high and weighs about 326 tonnes (Dowson, 2007). This puts into perspective just how large of loads these ancient pulley systems and cranes were able to lift in order to erect these massive stone structures all throughout the city.

2.2 Killer Animal Elevator

Not only were pulleys used in big construction equipment for hauling large loads, but they were also used in elevator contraptions in the hypogeum of the Colosseum to lift large exotic animals into the arena for battle. The Colosseum is one of Rome’s most famous sites as it was the location of bloody gladiator battles, animal hunts, executions, and naval battles. Most of the colosseum is made of travertine blocks, with a marble exterior. Today, most of the marble and travertine has been reused for other purposes like the construction of the Trevi Fountain (Luca Colosseum Tour). However, the skeleton of the structure still exists. After the colosseum was fully constructed, the city celebrated with 100 days of games. Archaeologists believe that included in these initial games were large naval battles where they flooded the arena. It is believed that such a spectacle only occurred during these initial games, before the construction of the Colosseum’s hypogeum which is the underground series of tunnels, cages, and elevators that made the amphitheater’s events possible (discoverrometours-hypogeum). However, flooding the arena would not have been possible with all these tunnels in the way, so the hypogeum was likely built after the rest of the structure. There was a wooden floor above this hidden area that was covered with sand to soak up the blood from these battles (Luca Colosseum Tour). Part of the beauty of this underground system is the element of surprise it provided for the spectators. They didn’t see all the inner workings of the structure; to them, a trap door opens and suddenly an exotic animal the likes of which they have never seen before comes raging into the arena.

This underground Hypogeum consisted of many moving parts including 15 corridors, ramps, wooden elevators, cages to hold the animals or prisoners, and many trap doors (discoverrometours). I took a tour of this underground hypogeum and was able to take a firsthand look at the reconstructed model of one of the elevators, as well as the evidence left behind that shows where these elevator contraptions were located in the arena. Throughout the underground hypogeum there are square shaped slabs of white stone with a large square hole in the middle as seen in Figure 7. These were the bases for the wooden elevator systems that connected them to the ground. While the wooden structures did not last all these centuries, these stone bases are still around today and lay out a clear pattern of where these elevators were located.

Archaeologists believe based on the age and wearing of these stone bases that the colosseum originally began with 28 of these elevators. However as the years progressed, the games became more and more elaborate, and eventually the number of elevators grew to 60 by the year 523 when the Colosseum stopped hosting the games (discoverrometours). This map pictured below in Figure 8 shows the locations of these 60 elevators. While I was touring, I was also able to see deep rope marks on the walls that were used to connect to the elevator systems. These are further indicators that allow us to accurately identify the location of the elevators. There were 20 of these elevators down the central corridor and 10 down the other 4 main corridors. In certain hunts all of these elevators would be used simultaneously to release as many as 100 lions into the area at a time (discoverrometours).

There were four main components of the elevator system: the winch, a compound pulley system, shaft for manual labor, and a trap door. At the bottom of Figure 9 you can see the bars of the wooden cage where the animals were held until their release at the top. Next to the cage, you can see a four pronged wooden shaft that was pushed by slaves in order to get the machine to pull the cages up. There were two levels of these manual rotating shafts that were used to pull on the ropes of the cage. It took four people on each level to push the machine so eight people in total to lift these large weights. The machine was built to be able to hold up to 600 pounds (Klein, 2015). This worked very well for most of the exotic animals that the colosseum showcases, except for the elephants. The elephants were never brought into the underground hypogeum, but rather through the main doors since they were too large and heavy to use these contraptions (discoverrometours). The ropes went through a compound pulley system at the top which decreases some of the force needed. The rope wraps around a winch as the cage gets pulled upwards. Lastly a trap door opens at the top at the same time the cages are opened to release the animals onto the arena floor.

This elevator model was built for a documentary called Colosseum: Roman Death Trap (Klein, 2015). The producers of the documentary aimed to create a period accurate clip of animals being released into the Colosseum arena. In order to accomplish this goal, the producers worked hand in hand with a team of archeologists and engineers. They based their design off of research archaeologists had done on the cuts and rope marks left behind in the hypogeum that show the making and location of these machines (Klein, 2015). When constructing the elevator, the team of engineers decided to try not only to recreate the model, but also to recreate the process as much as possible. They used the same materials as in ancient Roman times, getting their timber from the nearby mountains outside of Rome. They even used the same types of axes, two-man saws, and wedges to construct the elevator in ancient times (Klein, 2015). One of the main concerns with creating this video clip was how to get this machine into the colosseum without damaging the fragile interior of the site. In the end, they decided the best method would be to have it fully constructed outside of the colosseum, then lowered into it with a giant crane and gently place it down to not cause damage. In order to test their model for the documentary, the producers decided to use a live wolf as the test subject to honor the legacy of Rome (Klein, 2015). The recreation was a success and after filming they released ownership of the elevator to the colosseum where it has now been accessible to the public since March 2023.

Unlike the construction cranes described above which were used for practical engineering purposes, this elevator was built purely to enhance the world of Roman theatrics. While innovation and expansions were major pillars of the Roman Empire, they also had an intense fixation on entertainment and spectacles. This is why the events of the Colosseum were few and far between, but sensational. They were not just your average day at the theater, they were an all day long thrill. They utilized some of their most complex technology on this contraption for no other reason than to release killer animals into an arena so that the public could witness a bloodbath. However, it wasn’t just animals being lifted into the amphitheater but also decorations. Figure 10 is a drawing from the museum in the Colosseum that shows a live tree being lifted into the amphitheater at the same time as a bear. The games were not just meant to entertain, but rather to transport you to a world of the exotic, showing for the world to see the conquests of Rome. I find it interesting that improving the technologies in this amphitheater purely for entertainment purposes was such a strong motivator for innovation.

3. Conclusion

After researching the ancient crane systems and visiting the killer animal elevator replica system in person, I am still incredibly impressed by their ability to learn through experience. It is hard to imagine understanding a machine like these pulley systems without our modern knowledge of Newtonian physics. I also found it interesting how we still use much of the same technology that they did back then. We have made advances and been able to motorize this equipment. The basic concept of construction equipment remained very similar until the 18th century when the steam engine was invented. After this invention we no longer needed to have 8 people working a single lever in an elevator system, nor do we have 5 people pushing a treadwheel. Now we have engines and motors to perform the same tasks more efficiently that are run on various forms of fuel and energy. However, the basis of our technology is still founded on the same simple structures like the compound pulley system. I found it interesting when our program was touring the construction site of the metro Linea C stop and got to see the kinds of equipment they were using. Of course the modern equipment is advanced to levels far beyond that of ancient Rome. However, I noticed compound pulley systems, and large winches still being used in modern equipment. It is interesting to see how even though technology has come such a long way since ancient times, we are still able to apply many of the same principles.

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