Author: Oriol Pons Puig -
One of the workshop sessions for first-year mechanical engineers consists of modelling a car and testing its aerodynamics. In this workshop, we made the body of the car from a block of Styrofoam and tested the aerodynamics of the model by placing the body in a chassis with wheels and timing it down a slope. The slope consisted of an inclined rectangular box in which air was blown to amplify the car’s drag. Each car had to complete three runs, and the car which achieved the lowest time won. Times were measured using laser sensors.
To qualify for the competition, the highest point of the car's body had to be at least 32mm and the front view of the body had to respect a pattern which imitated the space required to fit a human being. In addition, no extra material could be added to the body of the car.
My winning design
Before starting to cut my Styrofoam block, I drew some sketches of what I wanted the side and front of the car to look like. This allowed me to not only design the body of the car with minimum drag in mind, but also to plan what needed to be removed and what needed to be sanded, and more importantly, by how much.
It was challenging to predict how the air was going to flow around the edges of the car, yet at the same time, it was very rewarding to see my car's times decreasing as I was shaping the body of the car towards what I had planned. My winning time was 2.440 seconds and my average was 2.450 seconds.
Tips for next year’s students
A large number of contestants were disqualified because they overcut the car case and the car did not fit under the regulations. Therefore, I would strongly suggest thinking twice before cutting with the hot wire. Secondly, I recommend testing your car at the earliest possible stage, once you believe you cannot improve it anymore. The temperature of the room increases noticeably during the competition due to the large number of students and I suspect it affects the performance of the models.
Good luck to next year’s contestants!