1. Engineering 10 Trebuchet Project
By HL and TC
Blk. 2

2. Introduction Statement of Inquiry:
Historical technical innovation has contributed to advances in modern human process.
Global Concepts
Scientific and technical innovation
Materials Provided
Wood ( 36 by 12 inches)
Lead counterweight
Various screws, bolts etc.
Sling fabric, plastic wheels
Description:
Students will use the design cycle to create a functioning Trebuchet that is capable of throwing an object with repeated accuracy. (25 feet, 5 consecutive times).
Learning Outcomes
-Work collaboratively in a team
-learn about historical significance of the trebuchet
-Understand basic principles and functions behind the trebuchet

3. Investigation Inquiry questions
What materials are needed
What are some common issues/problems
What does it mean to be proportionate
What is the recommended size
How much counterweight is needed
What type of wood is used
How far should the distance be
What are we throwing
How much time is required
How do we attach the components
What are the components
What type of trebuchet are we building
What calculations are required
What is an effective planning method
Inquiry questions
At the start of this project, we were given time to research info about the trebuchet and brainstorm possible designs. We then researched potential trebuchet designs to create; evaluating each on its characteristics or pros/cons

4. Design We also had to familiarize with basic physics concepts as well
Prior to brainstorming designs, we were unfamiliar with the
Etymology of the trebuchet, therefore we researched
The 5ws of it
We also had to familiarize with basic physics concepts as well
Definition/purpose- A trebuchet is a battle machine used in the middle ages to throw heavy payloads at enemies. The payload could be thrown a far distance and do considerable damage, either by smashing down walls or striking the enemy while inside their stronghold.
Where- Ancient China, then /Europe/ Middle east
What replaced Trebuchets?- The Cannon
Ex. Torsion, lever arms, moment, momentum, force, potential energy, kinetic energy, arm ratios.
These concepts had to be understood in order to design a fully functioning trebuchet.

5. Design To answer our inquiry questions, we conducted research
On the trebuchet, and what designs might inspire us.
There were 4 types we could choose from.
Fixed counterweight on a fixed frame
-weight is fixed
-Weight hits base to fling object
Swinging Counterweight
-weight is loose
Weight falls vertically
F.C on a floating Frame
-fixed weight
-allows weight to fall through the frame
Floating Arm (FAT)
-weight falls, causing one part of arm to fall, and other to swing up

6. Design We came up with three designs after researching various models
Fixed Counterweight with Floating frame
-Had wheels to absorb recoil and use it to increase thrust. However object had to be attached to a sling as well as balancing the counterweight with the arm size, therefore making it difficult to shoot without calculations
Fixed free swing counterweight
This model would allow the object
To be shot in a catapult launch method.
However the object would not go far due to the size ratio.
This trebuchet type is unique,
as the bigger the object is, the farther it can throw.

7. Design In the end we chose the fixed counterweight on a fixed frame.
This model has wheels the frame could surge back and forth by a small amount, allowing the counterweight to fall more vertically.
Secondly, the recoil force absorbed by the wheels could throw the object farther.
Although this type of trebuchet usually has a firing pin that pulls out of the
Frame to fire, we decided to use a string ties to a hook to create an elastic type of launch sequence.
Our good copy design sketch of our chosen design

8. Plan
After creating a blueprint for our project, we created a concise plan to help us build efficiently.
Goals of the team
We plan to finish the trebuchet by Jan 21st; the final deadline for construction.
Utilizing any remaining time and resources to add final tweaks and adjustments.
The PPT will be finished by Jan 21st, after construction is complete, and the trebuchet has been test fired. Until we reach
those deadlines though, we will begin a steady construction process of both these
Assignments simultaneously. Adding/removing info based on results.
Roles of the team
-Tyler-building
-Hoya- Design brief/building

9. Plan Strategies Used: 1. Be industrious and diligent during work time.
2. Make sure each group member fulfills their role.
Make sure the final product is in full working order to compete.
3. Calculate amount of resources needed and how to use them wisely.
4.Take risks and look for new effective ways to improve the product.
No matter how exotic the process.
5. If we make a mistake during construction, we stop and refine before considering
Anything else.
6. Teamwork and cooperation are essential for creating a successful project.

10. Schedule/Manual (by relevance)
Plan
Design Brief
Building
Finish research assignments done in class.
Start the investigation process, research types and pros/cons.
Create multiple designs, then decide on the most feasible.
Create a Blueprint/good-copy sketch.
Write down design process
Create a Plan including schedule and goals/roles of the team.
List Creation Process step by step
Take pictures of creation process
Evaluate by test firing.
Cut out wood pieces after measuring
Verify that all pieces are compatible with each other
Build the horizontal and vertical frame. Nail pieces together.
Add Gussets to strengthen edges and frames. Nail gussets after gluing.
Cut out plastic wheels
Trim out ready-rod for arm, attach wheels with screws.
Calculate arm ratios and strength, then attach to frame.
Attach Sling with firing pin
Attach counterweight
Test fire (using different counterweights)

11. Create Sanding, refining/assisting. Cutting and Drilling Hoya Tyler
Part 1# Assembly
After cutting out the required pieces, we can begin construction on the frame.
We create the horizontal base first, then begin the vertical frame.
We plan to create the design exactly how we pictured it in the planning stage.
Considering its pros and cons and evaluating them based on potential positive or
negative results.

12. Part 2# Strengthening/refining
After creating the frame, we measured and cut out a dozen triangles of thin wood to use a s gussets. Gussets would help stabilize the frames and angles, thus prevent the frame from becoming loose.

13. Part 3# Arm and Wheels We used a ¼ ratio for our arm.
When the frame was sturdy enough, we attached a ready-rod to hold the arm in place. Our arm wasn't a straight piece of wood, but consisted of 4 different pieces.
Two pieces were added to stabilize the arm at the revolving point to equalize the weight and prevent the arm from snapping.
-Once the arm was done, we cut out 4 plastic wheels approx. 10cm in diameter to absorb the recoil of the trebuchet when firing.
We used a ¼ ratio for our arm.
Our arm was approx. 25
inches in length

14. Part 4# Sling and weights
Now that the initial structure of the trebuchet was finished, we could begin sling and weight assembly. We used a square piece of fabric approx. 15cm by 10cm as the pouch. Secondly, we tied the pouch to the arm with a thin string.
Thirdly, we made a firing pin out of a string and a hook that was released by pulling on it. Therefore releasing the arm.
(The idea of a string firing pin was to give the arm an almost elastic type of force instead of relying on the removal of a rod pin to increase centrifugal force.)
In the end, we used two large weights instead of one.

15. Evaluation of Final Product
Test /firing results (Approx.)
First time- 10ft
Second time- 15ft
Third time- 27ft
Fourth time -18ft
Fifth time-15ft
Average of 17ft/five consecutive tries
The reason for the large difference in distance
was due to the loosening of the sling. The
sling should have been larger and the string
should ha been tighter. In other words, the
Movement and arrangement of the string and sling
(which was different each time) resulted in a
Different firing trajectory.

16. Evaluation (Tyler)
Overall, I am happy with our final product in terms of structure and resource use. We effectively utilized all resources to create the trebuchet. ( we even had leftover wood). We managed to complete the trebuchet and test it before the deadline but we didn’t have enough time to make modifications or improvements. The string and sling were not accurately assembled, which resulted in the inaccurate results of firing. I feel that I could have done a better job in measuring and testing parts such as the sling before permanently attaching them to the trebuchet. In the future, I plan to do 100% checkups on each part before proceeding to the next.

17. Evaluation (Hoya)
In the end, I am proud of our final product and the ways we used our resources and time. We made good use of every resource to make sure we didn’t over over-budget, and we worked on regular basis every class to consistently improve the trebuchet. Our firing results were a bit disappointing due to the odd pattern results. We had figured out a solution to the problem, but we had run out of time and had to reflect on the process we had managed to make. My role was to assist in the crating process any way I could, and to successfully complete the required design brief. I am satisfied with my role in the design brief as I went in depth of all factors and concept prior, during, and after the construction process. However, I wasn't very effective with my time as I did not get to complete the reflection process in time with the project. Our trebuchet was tested at the final day and I did not get to submit any possible improvements for the brief. For future projects, I intend to keep a tight schedule for our process. This included taking time time out of our own day if we didn't’t finish the required materials for that specific date. I feel that if I had done that, we would have had time to make any necessary improvements to create the best final product, as well as competing the brief in sync with the construction.

18. Team Evaluation
Our team managed to successfully complete the Trebuchet by the deadline, along with the Brief. Each team member contributed equally to the project to enable a successful final product.
The trebuchet itself is in perfect working order. It is easy to use with a simple firing mechanism which included advanced firing physics. (Elastic Theory). Our wheels worked fabulously as they transferred the recoil into momentum energy.
On the contrary, we did have a significant problem. Our sling was not the right size for the tennis ball we were throwing. It was too large for the ball, therefore causing it to slip around when it fired. We figured this was the reason for the odd pattern of distances.
Secondly, the string was very thin and often entangled with the trebuchet, delaying firing and causing confusion.
Our Solution to these problems were to accurately measure out a sling proportionate to the object being thrown as well as using tighter stronger wiring for the arm. We feel that we would have had a perfect work schedule and product if we tested/measured all materials prior to permanent attachment. Doing so would help us create the best product as well as leave time for improvements and reflection.
In term of competition, our trebuchet was average, but we could have done better if we had time to make modifications.
Our work ethic and knowledge of shop materials mainly contributed to our success in creating the project. Each team member did an excellent job of fulfilling their role. We worked hard every class and it sped up the process. In the future we should accurately measure and test all materials in sync with deadlines to prevent problems and to effectively reflect on the project for any improvements.

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