Make a Model of the Racer
The fifth step of the design process is to build a model of your design. This is the stage where my group decided that the water bottle, turbine powered air car idea is not going to work. It was, at this point, where we completely abandoned the idea and restarted the design process in an attempt to create a better rubber band racer.
Original Racer
Building the model proved a lot more difficult then we originally planned. First of, we collected a lot of water bottles in order to begin transforming that into our racer. We took a Poland Springs water bottle, removed the wrapper, and began by cutting off the side of the bottle. This would become the top of the racer where we could access the rubber bands and other materials that we would run through it.
Final Racer
The first part of the new racer that we put together was the wheels. We made the wheels out of old CDs and the axles out of fiberglass rods. The problem was that the hole in the middle of the CDs were a lot larger than the diameter of the rod. We poked holes the size of the rods into water bottle caps and hot glued them to the middle of the CDs. This made it so the wheels were attached to the rods and would not slide up them or slip off entirely.
The next part that we constructed was the body. We made it out of a piece of poster board that was 22 cm by 18 cm with a cutout in the back to expose the axle of 7 cm by 7.5 cm.
The problem with the body was that there was no way to run the axles through it so that they would still be able to rotate the wheels easily. We took an idea from our original design and applied it to this new design. On the original racer, we ran plastic straws through the holes so that the skinny coffee straws could rotate inside of a circle without being stopped by excess pieces of plastic from the bottle. In this new design, we hot glued two pieces of PVC pipe, length of 4 cm, to the back for the hind axle and a piece of PVC pipe, length of 7 cm, to the front for the front axle. This would help the axles spin in a circle easily and still be attached to the body.
We then knew that we needed to attach a rubber band to the body so that we could have a power source. We hot glued another piece of PVC pipe to the front middle of the racer. The rubber band could wrap around it without flinging off of the car mid-race.
Next we hot glued two water bottle caps together to make one wheel. We repeated this action twice in order to make two wheels. We poked holes into the tops of the caps and ran a skinny coffee straw that we got from the cafeteria through the two of them. The straw became our new axle for the back wheels.
Then we built the turbine. We took another water bottle, cut off the top of it along with the cap and cut that piece into six separate sections. Those sections became the blades of the makeshift turbine.
We than connected all of the pieces that we created in order to make a small racer that was missing its front wheels. It was also at this stage that we changed the wheels to a different unknown material. It was circle and light. We thought it would make for better wheels than the clunky water bottle caps.
We then connect the two wheel sets to the body by running the axles through the PVC pipe on the bottom of the racer, and attached the rubber band to make sure that it all fit together.
After running through it a few timer, we realized that whenever we would release the racer it would only move a certain small distance and then the wheels would stop turning and just glide. We wanted to make it so that the racer had more traction with the ground. My group wrapped the edges of the CD wheels with tape. After racing it again, this proved to be a good choice for the design.
It was still not complete. In order to make the racer more our own, we added a decoration to make it more fun. By using duct tape, we attached a small rubber duck to the front of the car. This duck was not just for decoration, though. It balanced out the weight of the racer, helping it go straight, and helped to remind us of which way the racer should face.
We then twisted the turbine in order to quickly test out the small racer. We found out that the turbine did not move the car at all. Our original design failed before it was fully built. It was at this time that we decided to scrap the idea and restart the design process. We hoped that we could be an adequate racer in time after this small delay.
After testing the racer a few more times, we made a few more changes. We got rid of the rubber duck. It was making the racer a lot more unbalanced than originally planned. We removed the duct tape from the edges of the CD wheels and replaced it with electrical tape. The duct tape had too many folds in it. This caused the wheels to be extremely bumpy and deviate from the original straight line.