This catapult was built using 1/4 inch MDF for the Lakehead Fall Design Competition.
It was cut using an Epilog Mini 24, 40 watt laser.
The bucket of the catapult was 3D printed out of PLA using a Dremel 3D20.
The catapult was designed to connect like a puzzle and have connections that require no form of fastening. The catapult can be assembled and reassembled easily. However to improve rigidity and durability, the use of wood glue is encouraged between all of the "slide in" connections.
Note: Dimensions of the AutoCad file are in inches. Dimensions of the .3ps file are in cm.
The catapult was designed to be powered by a torsion system. The material used by the creators was a type of fishing line that was fairly elastic. Overall, about 60 passes of the fishing line was made between the handles. Although fishing line worked well, there may be other materials available which will yield a greater power output.
In addition, two screws were used for the handles of the torsion system. These screws made it easy to increase or decrease the power of the catapult. It is important to note however, that the screws should settle in a position parallel to the base (horizontal) of the catapult to evenly distribute the force between both of the supports. If the screws are left perpendicular to the base (vertical), they tend to damage the section of MDF located between the two supports when the torsion material is subjected to high amounts of tension.
See below for a picture and video revealing how to wrap the material for a torsion catapult.
Video link: https://youtu.be/PRSBKm1encM
Image of how the torsion system should be set up.
Video of how the torsion system should be set up: https://youtu.be/PRSBKm1encM
To improve the catapult design, the bucket attachment could have been made slightly larger than the dimensions of the catapult arm. This is due to the fact that the bucket was a very tight fit onto the arm.
Additionally, other materials could have been experimented with in order to improve the ability of the torsion system. The fishing line used was very timely to install and was fairly easy to snap if the handles were tightened too much.
Moreover, the bumper created to stop the arm could have been altered to better facilitate the angle at which the arm would hit it at. Upon prototyping, the bumper often would fall off since the arm had a tendency to hit it upwards (when the bumper was set up to stop the arm at a shallow angle).