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.