On December 13, thirteen Yale seniors presented the results of their Mechanical Engineering capstone project (MENG 489a), conducted under the guidance of Professor John Morrell. At the beginning, Morrell split the students into two teams: one team made a device to harvest the energy expended from opening and closing a door and the other team converted a 50cc Piaggio motorbike into a gasoline-electric hybrid. The students selected two projects that they were passionate about, concentrating primarily on energy conversion due to its central role in mechanical engineering.
The energy-harvesting project was partially born out of the observation that a large amount of energy is required to open the heavy doors to Woolsey Rotunda on Yale’s Central Campus. While the students’ calculations uncovered that the amount of energy used to open a door is not large, it is enough to power automatic doors for handicapped individuals. In theory, this would allow for easier installation: a door could be self-powered instead of requiring an electrical line to be dropped from the power grid. In fact, this idea was so good that a Connecticut company called ADA-EZ is now producing units based on this exact concept. While Morrell acknowledged that it was slightly disappointing to discover midway through the semester that a form of their project had already been conducted, he pointed out that the existence of ADA-EZ verified the practicality and ingenuity of the Yale students’ work.
The gasoline-electric conversion of the motorbike utilized the electric motor system as a transient management tool: the system removed a pulse of current from the battery to accelerate the bike and reinserted the current slowly when decelerating or coasting. Lithium-iron-phosphate batteries inside the helmet compartment were used for this purpose because of their capabilities of delivering 180 amps (3 cells in parallel) and operating at a very low resistance. The basic design incorporated a belt mechanism to merge the power from the gas and electric motors. Output energy from the electric motor assisted with turning the central shaft extending from the gas motor. This design doubled the acceleration of the motorbike and made it “drive like a 150cc motorbike.” This increase in performance is important because it can make a relatively fuel-efficient vehicle much more attractive on the open market.
One facet of the capstone project that sets it apart from other Yale courses is that students are truly dependent on one another for success. While most college courses provide students a common experience through the same exams, problem sets, and readings, MENG 489 is composed of interconnected, individual tasks that are all vital to the final product. This puts a little extra pressure on each student because the result of his or her task directly affects the other tasks and the project’s overall success. For example, Morrell highlighted a “heroic effort” by Ryan Carlisle ES ’11 to learn the electronics of the door mechanism, which was especially impressive since Carlisle did not have this technical background coming into the course.
Another challenge of the capstone project was the breakneck pace of the fall term. Between waiting for parts, coordination between different team members, and unexpected set¬backs, the projects took time to develop. But despite the short length, Morrell commented on the intense professional growth of the 13 students over the three-month course. “I love watching the transformation of the students. They begin to trust their instincts, make their own recommendations, and take ownership of the projects.”