The "Da Vinci Project," a concurrent engineering project devised by Prof. Pedro Reis, created a buzz of excitement among the three participating teams of final-year Bachelor’s students. Reis, who heads EPFL’s Flexible Structures Laboratory (fleXLab), had the idea for the project during a trip to Florence. He decided to take his own fascination with the work of artist-engineers like da Vinci and turn it into a challenge for his mechanical engineering students.
Before rolling up their sleeves, the teams had to pore over several of da Vinci’s Codices - multi-volume sets of the Italian polymath’s drawings and writings - under the supervision of fleXLab postdoc assistants, Fani, Luna and Michael. Should they stick to the blueprints for machines that have already been modeled, such as the aerial screw, the self-propelled cart, the ball bearing, the mechanical knight or the fighting vehicle? Or should they step into the unknown and test one of his theories? It was a tough decision.
Generating as much heat as the sunStudents Salomé, Pierre, Quentin and Louis opted to step into the unknown, choosing to build a 23-gear friction machine supposedly capable of generating ’as much heat as the sun’. "As mechanical engineers, we felt comfortable with concepts like gear structures, gearboxes, reducers and amplifiers," says Salomé. "We thought we were equipped to sail through the challenge, especially given everything we’d been taught about thermal analysis this year." That confidence soon evaporated when they realized the scale of the technical challenge before them. "Driving 23 gears in a row would have required superhuman strength and virtually indestructible materials," explains Pierre. "Da Vinci even envisaged using diamond rods to cope with the weight and friction." The team, which was supervised by postdoc Fani Derveni, modeled and built a machine consisting of five gears. Even though one of the rods broke while the machine was running, the friction generated raised the temperature of the contact surface by 60°C.
Building a self-propelled cart, just because!When you choose a well-known da Vinci machine that has been modeled extensively, your aim isn’t just to follow the blueprint and understand how it works. Instead, you want to set your sights higher: to do something innovative and, perhaps, repurpose the design for a different function. That’s precisely what Naïm, Lucas, Martin, Nicolas and Lina did. Their team chose the spring-powered self-propelled cart that had wowed audiences in its day. "We wondered whether we could take the core mechanism and do something different with it," recalls Lina. "We wanted to test different options and really push ourselves. There were some bumps in the road, but we knew that if we put our heads together, we’d come up with solutions."
Postdoc assistant Michael Gomez supported the students throughout the project, while allowing them the freedom to develop and test their own ideas. Team member Martin explains the concept that they came up with: "We decided to build a kind of cable car that could carry loads across a ravine or a river, providing backup in the event of a power cut or fuel shortage. Every time we reworked our design, we hit a new problem. I really enjoyed this aspect of the creative process."
An aerial screw in an aquariumDa Vinci’s aerial screw, designed in the late 15th century, was inspired by Archimedes’ screw. In his blueprint, da Vinci considered the prospect of the machine’s use for the first human flight, theorizing that the spring-powered screw would push against the air to generate lift. "This machine has been studied extensively and we know it doesn’t work," say students Simon and Guillaume. "It’s too heavy and the screw is enormous. Taking this premise as our starting point, we wanted to make some improvements, whether that meant redesigning the propellers or changing the operating environment."
The team, which also included students Elyssa, Julien and Côme and was ably assisted by postdoc Luna Lin, decided to redesign the screw for use not in the air but in water, a denser medium that provides better lift. Elyssa ran experiments to determine the propeller’s drag coefficient under vertical movement without rotation. "Our initial goal was to get the propeller to rise from the bottom of the aquarium to the surface," she explains. "That meant it had to generate enough thrust to overcome both fluid and its own weight." Julien and Côme, meanwhile, were responsible for prototyping and building the model. The shape of the propeller was a challenge in itself. They designed and printed various versions, altering one parameter each time, so they could compare the results. "We noticed that da Vinci’s propeller wasn’t perfectly cylindrical, and we wondered whether that was a good thing," says Simon. "Our results showed that this gave the machine an advantage in terms of the force it could generate."