1. Dillon Schwisow’s Wind Tunnel Project

2.  Experimental Question: What is the effect of car shape and accessories on the amount of weight change/ down-force?  Prediction: I predict that the cars that are more aerodynamic and have a spoiler will have the least weight gain because the more aerodynamic a vehicle is the more air flows over the vehicle instead of pushing it down to create down-force.

3.  Changed variable: Car shape and accessories.  Controlled variables: Same fan speed, same fan, same wind tunnel, same scale, same unit of measurement (grams), same distance between the fan and the car ( about 1 in.), and same scale of cars(1/36).  Measured variable: The amount of weight change (weight change represents down-force).

4. Procedure 1. Gather materials. 2. Construct wind tunnel. 3. Place car on scale. 4. Record starting weight. 5. Turn fan on.(Note that depending on the scale, the starting weight may flip between two numbers). 6. Wait about one minute and record a sustained weight change. 7. Repeat steps 3-6 three times total with each car.  :Step 1 and 2  :Step 3 and 4  :Step 5 and 6

5. Car 1: Lamborghini Murcielago Car 2: Dodge Viper GTS-R Car 3: ’48 Ford pickup

6. Weight in grams Car and starting weight

7. C laim: For all cars, the weight/down-force increases from the starting weight. E vidence: After doing the experiment I looked at my observations for each car and each trial. I noticed that the weight increased from the starting weight. For the car 1, on trial 1, the weight went from 124 to 170,for trial 2 the weight went from 124 to 150,and trial 3, 124 to 130. It was the same for car 2 and 3, the weight increased from the starting weight. For car 2, trial 1 went from 110 to 125, then for trial 2, it went from 110 to 140 and trial 3 110 to 130. Then for car 3 trial 1 went from 133 to 180, then for trial 2, it went from 133 to 150, and trial 3, 133 to 140. The average weight change for car 1 was +26g then for car 2 it was + 20g and for car 3 it was + 27g. All the cars weight/down-force went up when the fan turned on. R easoning: I wasn’t really surprised when car 3 went up to 180g. I think the reason that car 3 had the highest amount of down force is because the cabin of the truck is a big obstacle. That means that the air had to go over the cabin of the truck which created more of an obstacle for the air. Therefore not all of the air could go over the car so then more air got pushed down to increase the weight. From research I learned that you don’t want a lot of down-force. Also the windshield of cars 1 & 2 were both more horizontal than car 3. That means that more air could go straight over the car instead of pushing the car down. My prediction was right, the more aerodynamic cars had the least amount of down-force. The averages show that car 3 had the highest average weight gain (+27g) but car 1 which was more aerodynamic was very close to it, having an average weight gain of +26g and car 2 was + 20g which was surprising as well because it was more aerodynamic than car 3 but not as aerodynamic as car 1, yet it was the only car that had a spoiler. I think the spoilers are to create down force on the back wheels. That would be useful for cornering because it would keep the back wheels on the ground if the car were drifting around corners like in a dirt track race.

8.  Even though I said that you don’t want to have a lot of down-force, that typically applies to normal “street” cars. On the other hand race cars are designed with certain things in mind. For example formula 1 cars are built to generate as much down-force as possible. At the speeds they're traveling, and with their very light weight, the cars actually experience lift at some speeds. So to fix that, the F1 (formula 1) cars have two wings or spoilers, one in the front and one in the rear. The wings direct the air flow so that it creates down-force.  Another factor in aerodynamics is drag. Drag is the resistance from the air. Cars can only go so fast because there is always drag going against the car. Aerodynamic cars usually can go the fastest because they have the least drag. One reason they have the least drag is because they have windshields that have a more shallow angle allowing more air to flow straight over the car. That means there will be less drag pushing against the car, allowing the car to go faster. In theory a car such as car 1 or 2 would be able to go faster than car 3 because they have a more aerodynamic body and have windshields that have a more of a shallow angle than other car 3 so there should be less drag allowing the car to go faster. Aerodynamics and drag are also a big part of fuel efficiency. A Toyota Prius is an example of a aerodynamic car that has a great fuel economy but isn't very fast. Prius owners probably spend less on gas than other car owners because it has better fuel economy than other cars or SUV’s. SUV’s aren't very fuel efficient because they have a larger body design and are usually meant to hold more people therefore they have more drag than sports cars, sedans or station wagons. Sports cars like Lamborghini’s or Ferrari's are usually the most aerodynamic and the one’s that have spoiler’s.