FIRST DESIGNING PROJECT OF THE YEAR
Our project was to design an air cannon and a base in which the cannon would rest on. The specification is that the base should be able to rotate horizontally and elevate vertically. After building the cannon as well as the base, we had to test the our prototype and prepare for a battleship challenge.
The link to the directions and brief description of the project: https://docs.google.com/document/d/117dhhldocB9reJR8UUJyin1fMyA5aToRGdfUjNIPVeI/edit
We started by creating a box which would act as a barrel support for our cannon which would restrict the pipes in the cannon to move making the firm. We used an online box maker to make the box and onshape to design the circle that would allow the pipes to go through as shown in the the last picture on the right. Onshape is an online CAD tool that is used for designing projects like our's. It is very convenient because it can be accessed at any place and any time.
The circles that we cut on one side of the box failed. So we measured the dimension a couple of time and cut out circles of different diameter to obtain an accurate value.
November 15 was the we first entered in to the shop. Mr Twilley gave all the students an introduction about the different equipments in the shop and how safely we should use it. We followed he instructions given in the battle ship document and built the cannon accordingly. We started by cutting the PVCs into the given lengths.
We then began to glue the pieces. For this process, we had to apply primer that melts the plastic in the PVC. We added the glue on top of the primer and attached all the parts together.
We made a small hole in the PVC to glue the bike tube into the tube for adding air in the tube for shooting the cannon. We then added the bike tube and used hot glue to secure it from air not leaking. The sprinkler valve is the attached to control the flow of pressure in the cannon. We completed by adding the other half of the cannon.
Our initial design for our base looked like a grave stone. It consisted of three semicircles on either side and a round bottom that we planned to use it for rotation. The circles were bigger that the cannon's diameter so that we could use it for the vertical elevation. But the problem we came across was that we could not have a fixed angle because the cannon might move while we shoot. We were looking for other options that could solve the problem.
While our search, a telescope and a tripod inspired us with a new idea. We tried to create a tripod but we did not have enough material. Even though we couldn't make it, we did not stop there. We brainstormed more ideas and ended up with the design which is the last picture on the left. The design consists of a semicircle part on which the cannon sits on. It contains an inner circle that has many circles for different angles and also a circle in the center. Then there is a circular base that has two wall like structures on either side with one hole on the top middle and the other hole is also in the middle but below the top hole. A rod connects the base and the semicircle part. It is being inserted through top hole of the wall like structure, then into the circle that is in the center of the semicircle part and then back into then wall like structure. This enables the vertical elevation. The other rod is the key tool that is used for changing the angle. The angle can be changed by aligning the circles and inserting the rod through the second hole.
After all the brainstorming, we started to sketch it on onshape. It took a few classes to come up with a right design. We planned to make a few semicircle parts and staking them together but instead we cut two semicircle parts and made a flat top for it. We made sure that the dimensions were correct before we started to cut it out on the board.
BUILDING THE BASE
We were supposed to cut it in small boards but Mr Twilley generously gave us a whole board to cut all the pieces. We struggled a lot and finally we had all the parts. When we started attaching the pieces, it did not fit. We sanded the edges, chiseled the holes, added hot glue in the holes and some how put it all together.
The box was then glued to the semicircle part with the use of wood glue and then assembled all the parts after it dried.
We finished our base and our cannon and we were ready to test. While we were testing, we understood that we were not able to use angles higher than 55 degrees because the cannon hit the floor. We still managed to test with the smaller angles.
We tried to rectify the issue by sanding the edges of the wall like structure and by adding a height to the base. We curved the edges but we were not able to make the base. So we ended up using a wooden stool to increase the height. The stool gave a great impact by allowing us to use the maximum angle that was possible present. It also helped in reaching the goal that was setup for the battle.
We tested with a pressure of 75 psi on the first day, 60 psi and 90 psi on the second day. We shot at three different angles and three shots at each angle to understand the working of the cannon. We came up with the best angle and the best pressure for the challenge. The challenge was also a bit different because we worked at a different terrain. For the practice, we shot on the football field but for the challenge, we shot at a tennis court. It took a couple of shots to comprehend the court. We scored 25 points in the challenge and we placed second in our class.