Design Problem:

Design both a CAD model and a physical prototype of an aerodynamic vehicle body to compete in a CO2 dragster race.

CAD Model Pictures:

Inspiration:

I was inspired to make design 3 because after researching I discovered that ellipses were the most aerodynamic shapes. I designed my design to include as many ellipses and be as round as possible. All my designs did not have a specific object inspiration but instead I was just trying to make cool looking, aerodynamic cars. Instead of imitating specific items like other peers, I tried to create complex, abstract geometries. I considered making a larger design, since all my designs have pretty small frontal areas. But I stuck with the smaller designs since they have less mass and therefore less friction as well as decreased drag.

Testing Using Simscale (Drag Coefficient Plots):

Final Chosen Design:

I am going to build a physical prototype of Design 3 because would make the best racer according to the drag coefficient. However, design 2 would be easier to actually construct with a CNC machine. Design 3 will have to be physically modeled by a 3D printer.

Project Links:

• Links to CAD designs

• https://cad.onshape.com/documents/72fc7acb311d382deaffccfe/w/2033e19e22ceb57b827e33f1/e/48e3ac0c474a17c40c9c9864

• https://cad.onshape.com/documents/7b06c856f6875934dd9cc42e/w/40461b42e6349df4bd0d32b5/e/29cb0822b76c41e0143e0341

• https://cad.onshape.com/documents/370e677ae9466bb8d55a9862/w/dfa5bbc88fe16cc868b9f62a/e/aea32361fdc2500d796f1518

• Link to Simscale

• https://www.simscale.com/projects/katcla327/simulating_racer_drag/

Physical Build:

How I Built My Racer:

I used my CAD model to 3D print my racer design. I did this by splitting my design into four separate pieces. After printing was complete, I started to assemble my racer by putting on the wheels and axles. I then ran into issues trying to put the four pieces of my car together. Glue would not stick to the 3D printed and there was no place to put screws. I tried using a blowtorch to melt the plastic together, which worked momentarily but was not stable enough to withstand the race. I ended up resorting to using electrical tape to hold the car together.

Race Evaluation and Improvements:

My car won it's first race against the other 3D printed car in the class that was at the time ranked first which then moved me to the top spot. I was in the championship race in the class and lost but still consider my car pretty successful especially after the many failed attempts at putting my car together.

Strengths:

• My car was very lightweight which allowed it to go faster and have less friction with the floor.

• My design looked relatively good compared to other designs in the class.

• My car design was unique.

• The wheels and axles had a good rotational speed and rotated freely.

• The CO2 hole perfectly fit the CO2 canister inside of it.

Weaknesses:

• The design was very bendable because of the tape.

• The middle section of the car was very thin. It kept sinking down and making the eye-hooks touch the ground during the race, slowing my car down.

• The tape increased the weight of the car.

• The design was very low to the ground which did not leave enough room to run the eye-hooks and line underneath it without slightly grazing the floor.

• The 3D printed material did not hold the eye-hooks well in place so they would not spin. They became loose after the first race and spun to the side during the second, creating friction between the line and slowing my car down.

Improvements:

• I would add holes in my CAD model between each section so I could properly attach the sections without so much tape. This would greatly improve the weight, make it less bendable, and make it more aesthetically pleasing.

• I would use a smaller drill bit to screw in the eye-hooks so hopefully they would not spin as much and instead stay in place.

• I would edit my design to not be quite as thin in the middle section giving it more durability.

• I would make the design shorter to even further decrease weight as it was seen that the lightest racers that do not have to touch the ground go the fastest.

• I would make the middle section of the design go up father from the ground so the eye-hooks do no come close to dragging the floor.