Introduction: The goal of this project was to design, build and test a tennis ball air cannon to compete in a game of ‘BATTLESHIP’ on the football/softball field. Our air cannon should have adjustable pressure, elevation, Z-axis rotation and be controlled by an Arduino. Our air cannon will be mounted on a base of our own design that will allow for rapid testing and evaluation of accuracy and precision. Finally, using our testing data, we will then engage targets at known distances for certain points.
To begin our process, my group and I had the idea that we wanted to create the most efficient cannon out of all the cannons in our class. Circe first gave us the idea to use a lazy susan like design to help turn our cannon in different horizontal directions. A "lazy-susan" is a revolving stand or tray on a table, used for holding condiments. We all really liked this idea as it seemed like a very simple, easy and efficient way to turn our cannons. We were all very excited to create the turning and elevation pieces for our cannon as we were very eager to have a very efficient design that would allow for good projection.
These pictures are from the very beginning of our design process. Here we worked together to design the cannon support that would allow for elevation and turning of the cannon. When we first started, we had absolutely no idea where to begin. So, we asked Mr. Twilley for some guidance which allowed us to come up with the design seen above. We made sure to draw out our design on the board to demonstrate how we wanted everything to be laid out.
My group and I developed documents for the base of our cannon. The square base is the platform for the “lazy susan” (rotation piece) to go on top off. On top of our square base, we made sure to mark the horizontal angles that our cannon would shoot at. As a result, we would be able to know the specific angle that we would turn the cannon when trying to shoot the tennis ball. The ladder piece is an assembly that will be used to raise to cannon at certain heights with increments of 1 inch. In addition, we created supports for the ladders that are placed on our rotation piece that goes on top of the square base. Next, we created two bridge-like support pieces for each side of the cannon. This would allow the cannon to be able to easily go up and down smoothly. In addition, the rotation piece has specific holes for the ladders, t its supports the supports for the handles on th bacnon.
The pictures below represent our process of printing and putting together our cannon support. This took about 2 to 3 class periods in total. After we cut all of the pieces out, we proceed by using wood glue to piece everything together. We thus had to use cotton swobs and lighting dab glue on the spots that we needed it most. After doing this, my group members and I sprinkled saw dust on the spots that had glue to provide more support. We also had to use a hammer when putting the pieces in their individual slots so there wouldn't be as great of the chance for them to become lose or potentially fall off. Not only did we apply glue in each hole that a piece was supposed to go into to, but we also applied glue around the sides if the piece when it was in its proper hole.
In the pictures above, my team and I are putting our cannon together. We would first prime each piece that needed to be connected to another piece and then we would glue the pieces together using an very thick and cement-like glue. In one long leg of the cannon we used a drill to drill a hole into the cannon. This hole is for the contraption to go into and into which we will pump compressed air in order to shoot the ball out of our cannon. The process took about two class periods as it required exact cuts and measurements. We had to make sure that we properly sealed our pieces together. This way, when we would go to shoot our cannon, no air would be able to leak out. After putting our cannon together, we unfortunately realized that the right side of the cannon was slanted and leaning towards the left side. We realized that we didn't push the right side in far enough when putting the cannon together which led to one side being crooked. Fortunately, this mistake did really affect our cannon's ability to shoot at all as the ball would shoot out of the left side of the cannon and the left side was almost completely straight. In some picture above, my group and I were also printing out and putting together the pieces to our cannon support. Printing these pieces took an entire class period. We learned how to work the shop bot and how to set the board on top. We had to make sure that all of the side were lined up when putting the sheet of plywood on top of the shop bot sheet. After this, we had to screw down the plywood sheet to the board. This required that we get on top of the board to apply pressure and weight on the board when screwing it down. This helped to prevent the board from lifting up when trying to screw it down.
In the second picture, Julia and I were measuring and drawing individual angles on the base of our cannon. This would allow us to know the angle of the the direction that we would fire at. This process took quite some time being that we had to make sure that every line was draw extremely straight using a protractor and ruler. The protractor allowed us to determine the specific angle that we were attempting to draw out.
The pictures above demonstrate how my group and I were able to shoot the ball out of our cannon. We first had to make sure that the cannon was at the specific angle that we wanted it to be by moving the plastic pole in the preferred slot on the ladder piece. We then put the ball in the cannon and used the ram rom to make sure that the ball was all the way in the cannon. We then had to put pressurized air into the cannon and we could only put in around 75-80 psi. To make sure that the right amount of air was in the cannon, we used the pressure gage to check the exact pressure that was in the cannon. Once we knew for sure that the right amount of air was in the cannon, we went ahead on the count of three and shot the ball out of the cannon. My teammates Julia and Circe were at the other end of the field taking measurements on how far our ball would go each time at each angle that we shot at. From this data we were able to conclude which angle allowed for the ball to be shot the furthest. Videos of the balls being shot can be viewed below, along with the table of our data.