Trebuchet Construction Project

Purpose:  To provide the basic information students need to construct a working scale model trebuchet capable of firing repetitively between 40Õ – 60Õ.

Instructions:  Students will compete each task below in sequence.

Tasks

  1. Students are to read the handouts provided by the instructor on the history and use of a trebuchet.
  2. Students are to visit the website below and read the sections on historical trebuchets.  Students should Ôtake the tourÕ of historical trebuchets and read the notes the author included about each machine.

http://members.iinet.net.au/~rmine/gctrebs.html

  1. Students will obtain a complete copy of the rules for the Wright State Trebuchet competition at the following website.

http://www.cs.wright.edu/trebuchet/full-rules-printable.shtml

  1. Now, after reading the rules, we will discuss them in detail in class.  Students should print out the graphics showing the rule specifications about trebuchet maximum height, maximum arm length, counter weight type, and other specifications.  See the images below for assistance.  We will discuss each in class.

  1. Now, students will use the WINTREB software to compute the actual values they will use on their trebuchet.  NOTE:  Even though the maximum length for a moment arm might be 39 inches for example, you may choose to make your moment arm a bit shorter (36 or even 37 inches) to improve accuracy or performance. 
  2. Students will print out a screen snapshot of the data values they use in WINTREB for the instructor to review.  See the figure below to make sure your snapshot looks similar to this one.

  1. Remember for this exercise, we will use 3 unopened, unmodified soda cans as the counterweight.  We will discuss this in class in more detail.  One fact, students may wish to research is not all soda cans are equally dense!  For example, some root beer drinks are denser than other cola products.  THINK about how this might be of advantage to your project.
  2. Next, each student is to create a Bill of Materials for their project.  For example, one might need to make a table like the one below.

Part

Quantity

Source

2Ó x 2Ó x 8Õ pine wood

4

Piqua Lumber

1Ó x 3Ó x 8Õ pine wood

4

Piqua Lumber

1/8Ó x 4Õ x 4Õ Luan plywood

1

Piqua Lumber

¼Ó steel rod – 3 feet long

1

Piqua Lumber

¼Ó nuts

1 – 1 lb box

Piqua Lumber

Wood screws – 1Ó in length

1 – 3 lb box

Piqua Lumber

Wood screws – 2.5Ó in length

1 – 3 lb box

Piqua Lumber

Stranded twine (1/8Ó diameter)

1 roll

Piqua Lumber

Rawhide/leather section

12Ó x 12Ó square

Any fabric store

 

  1. Because you will get to take this home and keep the completed trebuchet, each student is to obtain their own materials for this project.  The expected cost is approximately $12.00 for all materials.
  2. Next, students are to use the print out from WINTREB to measure and mark all materials for cutting.  Please double check each measurement.  Remember the old adage; measure twice, cut once!
  3. Students will predrill all holes for any fasteners used in the machine.
  4. SAFETY ¨ Students are to wear SAFETY GLASSES when using any power tool in the lab.
  5. SAFETY ¨ Students must not wear any loose clothing when using power tools in the lab.
  6. SAFETY ¨ Students must use clamps to hold parts that are to be cut with any power tool.
  7. Students are to assemble the trebuchet using the parts theyÕve produced from their own materials.  If assistance is needed for clamping, moving, or transporting materials, students are expected to ask for help at any stage of this project. 
  8. Once the trebuchet is complete, like the one shown in the image below, students are to practice firing the squash balls (provided by the instructor) and check their distances.  Recall the expected distances are 40Õ – 60Õ.   See the image below for the practice firing method.

Adobe ImageReady

  1. Students are to place small carpet fragments provided by the instructor on the bottom of the trebuchet to keep from damaging the basketball floor, when we go to competition at WSU.
  2. AT ANY TIME IN THIS PROCESS, STUDENTS ARE URGED TO ASK QUESTIONS IF THEY NEED HELP OR UNCLEAR ON A PROCESS.  WHEN IN DOUBT ASK FOR HELP!
  3. You have two weeks to complete this project.  Due date is 22 February 2004.
  4. This project is worth 500 points for this quarterÕs grade.