Final Thoughts

After completing our car, we concluded that it was not as successful as we wanted it to be. It was not able to roll very far using just the force of gravity and even with a push, the car did not roll far. The first version of our car included small wheels in the back with washers attached but the washers caused the rolling to be uneven. Even after switching the back wheels to larger ones, although improving the car's stability and ability to roll, it was still not enough to make our car successful. In the future, we would like to further improve our car by doing more research about how it could be successful. An idea that we already have is to have the axles roll instead of the wheels because when the axles roll, the dowels are smooth so there is less friction as compared to the wheels which have a lot of friction when the cardboard rolls. This friction force was a huge problem as it also wore down our wheels quickly. Another idea is to increase the weight of our car because when the mass is bigger, then the force of gravity will be larger and the force will be strong enough to push our car down successfully but this will only have a chance of working if the friction force can be minimize and if we can stabilize our wheels.

Final Thoughts

Overall our car was not successful to the degree of completing the entire course solely with the force of gravity and did not travel as far as anticipated.

The highlights of our car, however, were a fully functional steering and braking system along with a frame that was able to support the weight of the driver.

In the future if we were to modify our car we make some engineering changes in our car. The biggest change that would effect our car’s performance would be increase the size of the back wheel compared to the front wheels. This increases would result in an increase in the magnitude of the force of gravity and decrease the magnitude of friction. As the radius of the back wheel increases the angle theta increases. When theta increases the magnitude of gravity (mg sin theta) increases and decreases the magnitude of friction (cmg cos theta, c= coefficient of rolling friction). 

Problems/ Solutions

Problems:

After finishing our first model, as modeled by our video, we encountered several problems with our problem. The biggest problem of course was the car not being able to roll freely with the force of gravity down a slanted surface. When observing the potential places of errors it was concluded that their was a problem with our wheels: both on the contact with the ground and axle. The error with the constant with the down was that their was too much friction between the dowel and axle since because when lifted up and spinner with an initial force, the wheels would quickly stop which shows a strong force of friction, this would attribute to a high rolling kinetic friction. The contact with the road was also a problem because when tested out on a very step slope, the car stayed at equilibrium, which means there was a high rolling static friction. 

Approach to solve the problems:

To fix the problem of a high static friction we increased the radius of the wheels. This allowed us to decrease static friction because as the wheel radius increase you get closer to a more perfect flat contact with the surface (the earth is characterized as a sphere, but because of its huge radius we perceive the surface as flat). This flat contact means less resistance which intern leads to lower friction. 

Finished Cardboard Car!

Scale drawing of the design of each functional component

  

 

Scale drawing of the design (INITIAL THOUGHTS)

These following design aspects are subject to change as we develop our car in the building stage:

Steering: The current choice of steering was primary influenced by trying to make the construction process as simple as possible. Note that the front axel is made shorter to allow a greater use of dowel length in other areas of greater importance. Also removing length from the front axel reduces change of breakage since a shortage means more force will be required to cause deflection. 

 

Project Research:

During our research we found several interesting physics thoughts that would allow our car to better fill our objective of completing the distance of the race the fastest and being able to obtain an optimal distance. First of all we want to make sure that our primary structure that would be made of wooden dowels will be able to hold the weight of the car and the rider. The most optimal design aspect to do this would be to construct a triangular base supporting the weight which would better distribute the weight rather than having a break point where majority of the pressure meets the dowels. The next factor to consider is the mass of the cart we want without the rider. By using metal washers added the wheels we should be able to one add more mass to the car which will give it a greater inertia allowing it to travel farther and also faster because it will be less prone frictional forces down the sloped track. Two, by adding it on the wheels we don't add any extra force that would be exerted on the wooden frame and also give the wheels more inertia which means they will be less prone to deformation it will be harder for it to not follow a circular motion. By keeping this circular motion it will be able to reduce the friction of the wheels. We also do not plan to have any sides to the car similar to a go kart. Majority of the mass will be concentrated at the back end of the cart to allow for an increased potential energy and because the strongest part of the cart is at the back.