Introduction: Simple Tension Catapult Tutorial

This is our final project for the 2014 Biomechanics Field Museum program. We were told to design a catapult using a software called Sketch-Up in both 2D and 3D which would later be processed through a CNC Machine. From there on we took it into our hands and built :)

Enjoy our simple tutorial!

For this workshop;

- 4'x8'x3/4" Plywood (2 Catapults/Sheets)

- Sketch Up Architecture Program

- ShopBot(CNCMachine)

-V-carve Program

- Illustrator (Optional to clean up your Sketch Up BluePrint)

For Assembly;

- Drill

- Screws

- String (Parachord)

- Wood Glue

- Plastic Cups

- Saw

- Elastic/ Bungee Cord

Step 1: Using Sketch Up!

  • Start up by opening the program Sketch Up.
  • If you do not already know how to use the program, make sure to get the hang of it and mess around for a while before starting your catapult.
  • You want to begin by making a 4'x4'x3/4'' square, this will be your work area.
  • Make sure that as you build your 3D model, to make a flat copy as well (this will be your 2D model)
  • Once you're done constructing make sure to export your flattened 2D model as a pdf file. (We had exported it as a .dxf but later found out that lead to complications with the other program.)

Step 2: CNC Time!

When you open up your file in V-carve

If it is messy;

  • You will have to remove extra geometry and that can be done by using Illustrator.
  • Once it is cleared and ready to go, you may start to run your CNC machine, we used Shop-Bot.
  • After the pieces have been cut out you can pop them out.

Step 3: Time to Assemble!

  • Once you've popped out all of your individual pieces, you're going to want to start to sand the edges to get rid of any rough parts. *WATCH OUT FOR SPLINTERS*
  • Now you want to start to glue your pieces together.
  • Following the glue make sure you put screws to better support your catapult.
  • After you've finished constructing your catapult, you will need to take a string that is twice the width of your catapult and string it through the holes on the side of the catapult walls and through your catapult arm.
  • Pull the string on to rods and twist them until you have the wanted tension built.
  • If you want to give your arm more support you can add a bungee cord also.

Step 4: FInished!

This was our finished result.

We enjoyed creating this very much and we hope that you enjoy making your own catapult :)