Fire Away!

Our Project

The goal of this project was simple: make a catapult and make it shoot as far as possible. However, we were given some restrictions.

1. No part of the machine could be longer than 1 meter

2. It had to be able to used used over and over again

3. Must have a base that sits on the ground

4. Two legs that hold up an axle

5. A lever with a load and effort

6. Able to fire on its own without any extra help

7. Should be easily portable

We started off finding materials in the maker space, the room in which we usually start building our projects. For the first building day, I was unfortunately on my own, as my team was busy. I gathered some basic materials that were compatable with our agreed design and set them aside. The next building day I actually had a team to assemble parts with. We ended up with a relatively small machine, but a powerful one. It focused on having a large bunch of rubber bands placed behind the axel in order to achieve maximum power. The arm itself is about a foot long and has a very light weight, which allows it to swing through the air with more ease. The entire machine itself is not that large either. Discounting the arm, almost every part is less than or equal to 1 foot. This allows it to be very mobile and waste no energy on anything other than flinging our clay ball into the distance.

Modifications

We made quite a few modifications to our machine in order to improve its overall performance.

• Decreased arm weight to allows more energy to be spent on moving the projectile

• Increased the axel's height to allow more time for the projectile to gain velocity

• Increased the number of rubber bands to increase the net force of our machine

• Changed the length of the string attached to our projectile to allow more time to follow through before projectile release

• Decreased the weight of our projectile to allow it to travel further

• Moved the rubber band base 10cm back to multiply the power that our machine is outputting

Calculations

• Mass of projectile - 10g

• Horizontal Distance - 45m

• Time in air - 2.5 sec

• Vertical Distance - 7.6m

• Horizontal Velocity - 18 m/s

• Vertical Velocity - 12.25 m/s

• Total Velocity - 21.8 m/s

• Release Angle - 32*

• Spring Constant - 333.3 N/m

• Initial Spring Potential Energy - 10.4 J

• Kinetic Energy - 2.4 J

• % of PE converted to KE - 23%

Selling Points

Unlike the other machines that performed well during this project, ours was very compact and easily portable. Our machine allows for a powerful launch without worrying about the space you have avaliable. We were capable of surpassing 50 meters after just a few modifications, which is one of the highest scores in the class. Its a small but powerful machine.

Reflection

My overall feeling about this project is pretty positive. I think we worked well as a team and succeeded in being one of the highest distance-scoring machines in the class. The one negative thing I feel about this project is the fact that of the final week of the project, I was sick and had to stay home. This had me miss out of many of the calculations. However, I am still happy that I got to contribute to the overall design and construction of our machine.

Additionally, my team did an exellent job in finishing construction quickly, which allowed us to have more time to revise certain parts of the machine. Thank you to Liam McMann and Cole Shortz for being exellent teamates.