One of the main problems I came across was how to measure drag, and came up with a set up, that with sensitive enough equipment, would work. A small model of a Mini Cooper was placed on top of a car, and in a wind tunnel. A string was tied to the front of the car, and the string was threaded over a pulley. At the end of the string was a weight, so when the car was pulled back from wind, the weight lifted a certain amount. The weight rested on a scale, so by subtracting the original weight from the drag-impacted weight, the drag was measured. This worked but I had to make sure that variations between each test could be avoided. This setup was tested in a wind tunnel and also mounted on top of my dads car.
From research, I found that most of the drag on the car is related to how the air comes off the back of the car. This separated flow creates a partial vacuum that is responsible for most of the drag. By creating attachments, I found I could make that area of separated flow smaller. A good visualization of this is the process of narrowing the wake of a boat. My first attachment design consisted of two vertical wings attached at the back sides of the car and curved inward, which narrowed the flow. My second design was one wing down the center. This resulted in increasing the drag instead of lowering it. Several other designs were tested, but they had little effect on the drag. The results I collected in the wind tunnel supported the results I got from testing the set up on the car. My first attachment design was the most successful and it reduced the total drag by 12.5%.
This project is interesting because it can save money for people if applied to full sized cars, and it can help our environment. It can keep the air clean, and the ground still full of oils that are taken to make car gas.
This project is about By adding attachments to the back of a Mini Cooper, I reduced the drag by 12.5% and therefore substantially increased the miles per gallon.
Science Fair Project done By Thomas C. Judge