Final Thoughts

Given that we've spent over 15 hours on the car, I'm proud of what we made. The way it turned out was a lot better than last time. This time, the rolling felt a lot smoother than last time, when it didn't really roll and was bumpy due to the significant reduce in friction. We've improved on most problems including friction, stability, and design/look. 

However, there are still some problems with the car. When rolling down a less steep hill on the street, it didn't roll so well. Disappointed, we didn't know what the problem was because we had put a lot of effort into improving the car. After some thought, I realized that the wheels should have a more even surfaced, be pointed straight, and have smoother surface which would further improve the performance of the car. In addition, to prevent other rolling, we could've glued the pvc to the wheel and the dowel to the card board which would have secured everything so that only the pvc would roll against the dowel so that there would be no decrease in angular momentum of the pvc and wheel because of the slower spinning of other parts. Another idea would be to have the dowels roll inside the pvc and have the wheels glued onto the dowels instead of having the wheels and pvc roll like in our car. Another idea is to decrease the rotational inertia of the wheels by making the wheel have less mass and less radius according to the equation I=mr^2

Despite this, I am still happy with the way the car turned out. I can gladly say that we definitely improved everything about our car from last time and I can say that we also improved our teamwork and efficiency as we finished the car in less than half the time it took for the last car. 

Hopefully, we can win the race tomorrow. 

Final Product, Last Touches, Video

Over the weekend, we put the final touches on the car and tested it as shown in the video. The car was painted green and blue (the only colors we had) and had a top cover (for an aesthetically pleasing design) that can open. We glued stoppers to prevent the wheels from coming off which finalized the wheels into place. Also, we extended the steering stick with pvc so that there is more space for the driver to put his feet and so that the amount of force to steer can increase as explained before. We also fixed up the car and stabilized it after the failure and collapse during the first test run.We thought about sanding the wheels to decrease friction but we decided not to. I am glad to say that this is definitely a huge improvement from our first car. 

Progress and Procedure

 
The progress of the car went really well. We finished the entire car in one Sunday working nine hours from 9am to 6pm. We didn't expect to work this long but we got carried away and were too concentrated in our construction. Also, due to time constraints of finals and AP tests, the weekend was the first weekend we could start and after that was finals so we wanted to finished within the time frame of the weekend. We created the unpainted version of the car with the implemented steering system and the wheel rolling system (PVC against dowel). Also we added non paint related decorations to the car. Many aspects of the car that day were improvised based on the materials we had and from there we created our car.

Problems: We were too picky about cardboard so we went to walmart twice and drove all the way to costco for the spoiler. Also it wasn't stable. We had to take it apart glue it and tie to stabilize it multiple times because came apart. We also had to distance wheel away from body of the car to prevent contact.

Sketches, Design, and Explanations

 

These are quick sketches of our pre- car planning. Most of it was about how we would implement the PVC and dowel system to reduce friction. In addition, we knew that we would have a normal box as the body of the car. This is what was planned out. However, many other aspects of the car were implemented based on what materials were available.

Re-use: Wheels, Front dowel, String
New: Cardboard, PVC, back dowel

The main dowel of the previous car was unusable. Therefore, we used what we could from the previous car. Although it was car improvements, we had to construct a new car body using new materials in order to implement our improvements but we did re-use wheels, string, and the front dowel.

Planning: Strings and glue kept cardboard together. Three layered cardboard and dowel underneath stabilized car. Improved rotational system as mentioned earlier. Steering and braking system will remain the same.

Prior Car's Problems and Improvements (Main Post Highlighting Physics Principles)

Problems
Our previous car was filled with many problems.
1. The wheel was in contact with the dowel. This created a lot of friction due to the roughness of the cardboard rolling against the dowel.
2.Large washers were glued around the sides of the wheels. Eventually, the wheels wore down causing the large washers to touch the ground. This caused bumps and uneven rotation of the wheels.
3. The entire body of the car proved to be very unstable when Akul rode the car. The cardboard was not sturdy and it wobbled a lot. In addition the car was mostly just a dowel and it looked very slim and like as stick

Improvements
1. After recalculating, we learned that mass does not matter. Potential energy gets converted into kinetic energy and friction. The equation would be mgh=1/2mv^2+uFn, where F normal would be equal to mgcostheta so the equation would be mgh=1/2mv^2+umgcostheta. The masses cancel out so we can see that mass is not taken into account during calculations. From this, we did not put effort into adding more mass to the car, as it did not matter. Therefore we removed washers from the wheel.
2. The body of the car was made slim in order to reduce the air resistance.
3. (Main Improvement) An improve system of rotation for the wheels was implemented. Using the same wheels, small pieces of pvc were cut and put into the holes of the wheels. The holes were very tight, enough to hold the PVC in place. This was done for each of the wheels. Two dowels, one in the front and one in the back were secured through holes in the cardboard. The PVC in the wheels would have the dowel inside of them so that they would roll freely. So essentially the PVC and the wheel would be rolling against the stationary dowel which reduces friction because the surface of the contacts when rotating belong to the smooth pvc and smooth dowel. Also washers between the cardboard body and the pvc prevented contact with the cardboard and allowed smooth rotation against the the washer instead of the cardboard This reduced friction.
4. To improve stability, we layered three strong banana boxes as the seat and main body of the car. In addition, glue and strings helped tie and keep the car in place.
5. Steering system was improved by extending the handle for the feet to push on. This increases the torque because the lever arm is increased. Torque is equal to force times lever arm. So force is torque divided by lever arm. This means more lever arm will have less force required to steer so the driver can steer more easily.
6. The overall design of the car looks a lot better. More decorations were added and the car now better resembled a real car. In addition, the car was larger now and more comfortable to sit in.
7. Keep the small front wheels because the radius is small which makes it have less rotational inertia which means it spins more easily. The back wheels need to be large to support the car and so that they can reach the ground.