Fire Away

Fire Away Trebuchet

Description of Initial Design

In our project, Fire Away, our group went with a fairly straightforward design, with a few modifications. Over the one week of working on this assignment, we decided that wood was the best and most accessible material to use for the trebuchet. First we started with a thick plank, and built from there. We added two thin pieces of wood for the legs, and drilled a hole on both sides for the axle. Then, we added an arm, a few nails, grabbed our rubber bands, and we were set to fire for our initial design. 

Our Eight Modifications

1. For our first modification, we reshaped the legs, making sure the axle was in a straight and horizontal position. This provided a more stable launch, which made the projectile go further.

2. Our second modification was removing the basket at the end of the arm that held the projectile to begin with, and replaced it with a simple nail that would be used for attaching the projectile and string. This makes for a quicker release and causes more airtime, thus making more distance.

3. For the third modification we made, we took out the wooden piece in between the legs, which allowed the arm to swing a full 360 degrees. This made the projectile have more force after launch and travel faster in air.

4. The fourth change we made was simply adding more rubber bands for the launch, we tested 2, 3, 4, and 5 rubber bands. This created more tension, allowing for more force.

5. We decided to add a board on the bottom for our fifth modification, which makes for more stability and less movement when we launched the ball. This made for a more straightforward launch, which made the projectile have a steady launch angle.

6. Our sixth modification was adding multiple holes for the axle to go through on the arm. This let us test multiple arm ratios and find the best spot for the axle to be. We found that the best ratio was 2:2, letting the arm have the most momentum and force put into the projectile.

7. We took out the metal hex nut in the projectile in our seventh modification, because in our experimental findings we found that lighter weight=further distance. This is because a lighter weight requires less effort and force to move.

8. For the last modification we cut the arm length back, so that the arm could swing in a complete circle around the axle. The lighter the arm weight, means less effort to rotate.

Main Selling Points

Consistency:

Our trebuchet launched the projectile a consistent distance between 12 and 15 meters. This allowed us to take better averages and provide more accurate data.

Safe:

Because of our large base at the bottom of the trebuchet, our model was stable and safe, which helped increase the distance our projectile traveled. 

Portable:

The trebuchet we made was relatively small and compact, which made it easy to move and easy to set up.

Easy Setup: 

Because our trebuchet is so portable, it makes for an easy setup. Just put on the rubber bands, pull it back, and the projectile is ready to be launched.

Content

1. Mass of Projectile: 0.014kg

The mass of the projectile we used for the data was 0.014 kilograms

2. Horizontal Distance: 13.5m

The distance the projectile traveled was 13.5 meters

3. Time In Air: 1.38s

The time the projectile was in the air was 1.38 seconds

4. Vertical Distance: 2.33m

The height the projectile reached at its apex was 2.33 meters

5. Horizontal Velocity: 9.78m/s

The velocity of the projectile in a horizontal movement was 9.78 meters per second

6. Vertical Velocity: 6.76m/s

The velocity of the projectile when falling was 6.76 meters per second

7. Total Velocity: 11.88m/s

The velocity of the projectile relative to both vertical and horizontal velocity was 11.88 meters per second

8. Release Angle: 34.6°

The release angle of the arm when we launched the projectile was 34.6 degrees

9. Spring Constant: 140 n/m

The spring constant, which measures the ratio of the force affecting the spring to the displacement caused by it, is 140 newtons per meter.

10. Initial Spring Potential Energy: 8.5J

The spring potential energy, which is 8.5 joules, is the energy stored in the rubber bands by being stretched.

11. Kinetic Energy: 0.67J

The kinetic energy that the projectile stores when launched is 0.67 joules

12. Percent Converted: 7%

The energy converted from potential energy to kinetic energy was 7%

Our Analysis Poster with Experimental Data

In our experimental data, we decided to test the weight of the projectile and how it affected the distance it traveled.  We tested three weights of 0.009 kg, 0.014 kg, and 0.019kg. We found that the lighter the projectile, the further the projectile will go.  The 0.009kg projectile was ideal for the furthest launch.