Under Siege
The project was a partner project. In this project we had a choice of builds. We had to choose between three options, a catapult, a trebuchet, or a ballista. We chose to build a catapult. There was no limit to the size. We couldn't use any motor to power the catapult. The goal of the project was to fire a marshmallow as far and as accurately as possible.
The technological concepts in this project were different lofts, rubber band amounts, and catapult arm length. The different lofts were created by angling the whole catapult to create different flight paths for the marshmallow. We changed the amount of rubber bands to change how far the marshmallow would go. The last concept was the arm length. We made this longer and longer until we found the right length for the best distance.
My learning goals for this project were to learn how to find the best loft and arm length for optimal accuracy and distance, and to be able to make a catapult that had the ability to re fire.
This is our finished project. It was made mainly of wood. We made the base and the supporting arms first, then added the firing arm. After some experimentation we added the base to add height and loft, to increase distance. We added the bottle cap on the firing arm to hold the marshmallow before firing. The rubber bands were stretched over a dowel rod to create elastic potential energy.The feedback for our catapult was mainly good. It shot a maximum 26 feet, and on the accuracy test we made it in first try. We were very happy with the catapult's performance and the build quality.
If I were to redesign the project there are a couple of things I would change. I would increase the height of the supporting arms to allow a better range of firing arm motion. I would also enclose the sides of the base for a more appealing overall look.
The main technological resources of the project were the rubber bands, firing arm, and dowel rod.
The rubber bands provided the power to move the firing arm and to launch the marshmallow. The firing arm was how the marshmallow was launched, it moved upwards and hit the dowel rod which flung the marshmallow.
The biggest problem of the project was the rubber bands. If stretched too much they snapped, which was extremely frustrating towards the start of the project. Also, after a few launches the rubber bands became stretched out and lost their power.
We over came this problem with two solutions. Firstly we made the top dowel rod thinner to reduce the total are of rubber band stretching on the wood. Secondly we changed where the nail on the firing arm was to remove unnecessary stretching,
