Nazaha Muntafi May-cie Designing a trebuchet Nazaha Muntafi May-cie

Introduction Statement of Inquiry Historical technical innovation has contributed to advances in modern day human progress. Global Concept Scientific and Technical Innovation Project Goal Our goal is to develop a working trebuchet with the capacity to throw a tennis ball 25 feet with accuracy.

Inquiry questions What is the best ratio between the swing arm and throwing arm? What are the key features of the base of a working trebuchet? What is the relationship between the size of the trebuchet and the distance it throws? How long must the sling be to throw a tennis ball 25 feet? How do different weights affect the trebuchet? How does a trebuchet compare to a catapult which has the same dimensions for its base? Does the material used to make the sling affect how far a trebuchet throws?

investigation Using the sheets provided by Mr. Wright we began our investigation. After learning about the basic information about trebuchets, we looked into the pros and cons of different trebuchet designs. To continue with our research, we created our own table to be able to record our information is a clear and concise way.

The table we made for our notes

Planning

Design 1: The swinging counterweight on a fixed frame Pros Easy to adjust The basket adjusts fall to a certain degree and helps the weight fall more vertically. Cons Difficult to move Weight does not go down in that straight of  a line Our Questions Would it be stronger than the fixed counterweight on a floating frame ? If yes why?

Design 2: The fixed counterweight on a fixed frame Pros The simplest design with the fewest number of parts. The weight can fall straight down. Cons Forces counterweight to fall in semicircular are which causes weight to fall vertically, decreasing the power. Our Questions What is the relationship between the counterweight and the throwing arm?

Design 3: The fixed counterweight on a floating frame Pros Wheels help surge front and back, causing counterweight to fall more vertically. Cons The counterweight may be difficult to attach. Our Questions To what degree do the wheels help the counterweight fall more vertically?

Design 4: The Floating arm trebuchet Pros The most efficient kind of trebuchet. It looks different compared to other trebuchets. It can pick up the most energy. Cons It’s the most difficult to build out of all the trebuchets. It loses range advantage over regular trebuchet at very large scales. Our Questions At what scale does the fixed counterweight on a floating frame trebuchet lose its range advantage over other trebuchets?

Our plan for the trebuchet The final design Our plan for the trebuchet

Creating the trebuchet

materials 12 Pieces of wood (36”×1”×0.75”) Metal rod×1 Washers×12 Nuts×12 Screws (assorted sizes) Party hat×12 Duct tape Tennis ball×1 Counterweight

Tools Band saw Drill press Drill Wood Glue Rulers Screw drivers Clamps

Creating the trebuchet The following steps describe how we built our trebuchet: Cut the pieces of wood to the desired lengths and label them. Create the sides of the trebuchet. Connect the two sides together and attach two more pieces of wood to form the base. Cut the metal rod to the required length. Put the metal rod through the sides of the trebuchet, the throwing arm and the washers and bolts. Cover a party had with masking tape and attach it to the throwing arm with a hot-glue gun. Use different counterweights to test the trebuchet.

Creating the trebuchet

Work Distribution Inquiring and Analyzing Nazaha – 50% May Cie – 50% Developing Ideas (Planning) Creating the Solution (Building) Evaluating (Trials) PowerPoint Nazaha – 85% May Cie - 15%

Distance Travelled by Tennis Ball (ft) Trials Trial # Distance Travelled by Tennis Ball (ft) Weight Used 1 21 5 2 30 2(5) 3 17 3(2.5) 4 27 3(2.5) – changed the length of chain from trial #3 2(2.5) 6 7 2.5 29 4(2.5) 8 28

Reflection: Nazaha Since I had not taken Product Design 9, I was fairly nervous at the beginning of the because of my inexperience. As we started designing our trebuchet, I became more comfortable because we would have a solid plan while building our own trebuchet. I really enjoyed working with May-Cie. Both of us had our own strengths and weaknesses and likes and dislikes and was able to help each other in areas we were lacking. I drew out the plans and May-Cie cut the wood. After building our trebuchet, we kept fine tuning it although we didn’t reach our goal of having our trebuchet throw a tennis ball 25 feet. The range of our trebuchet was between 7 feet and 30 feet. If we were to do this project again, rather than focusing on just the mass of the counter-weights, I would also adjust the lengths of the arms of the trebuchet to fine tune it.

Reflection: May-cie First of all, I have no experience with building or making something before  so it’s hard for me to recognize all the stuffs that we have to use. I was really scared to touch all the equipments because I didn’t know how to use it but as we started on building trebuchet I gained more confidence because i had to cut all the woods. It was really fun working with Nazaha, we always help each other. We didn’t really reach our goal because we didn’t get 25 feet but we tried our best.  I wish we work more on research and make our trebuchet small but has a longer arms.

Resources used http://www.instructables.com/id/How-to-Build-a-Trebuchet/ http://www.sciencebuddies.org/science-fair-projects/project_ideas/ApMech_p013.shtml http://www.real-world-physics-problems.com/trebuchet-physics.html http://tantaurus.net/trebuchet/php/trebtypes.php