Article: This catapult design project is used to teach engineering skills to children.  It builds a slightly more complex torsion catapult than the previous methods, but requires just a few additional supplies and steps.  10 standard (4.5") craft sticks 1 jumbo (6") craft stick 1 drinking straw 1 6" length of wooden dowel, with a small enough diameter to fit through the straw 1 elastic band Glue gun and glue stick 1 milk jug lid or large bottle cap Ammunition! Ping pong balls and grapes both work well with this catapult project. These will hold the dowel/straw fulcrum that will support the throwing arm.  Add a dab of glue 1/2" from the top of a craft stick, and attach another stick to it at approximately a 30 degree angle.  Create a second upright that is the mirror image of the first. Place a dab of hot glue on each of the bottom legs of the first upright, and attach a craft stick connecting the two so that the vertical portion of the upright attaches to the end of the base.  Repeat this process with the second upright.  Then use hot glue to attach one additional craft stick to the front of each of the uprights. The base should now form a rectangle with one end open, and the two uprights sticking up parallel to one another. Cut a 2" length of straw and slide the dowel through it.  Use hot glue on to attach the dowel firmly to the wedge formed at top of the each upright. First loop an elastic band around the craft stick that connects the two uprights.  Then glue the large craft stick to the straw so that about 1/2" hangs below the straw. Finally, carefully attach the other end of the rubber band near the bottom of the large craft stick.  The throwing arm should now be able to rotate freely around the dowel on the straw, and the elastic band will put tension on the throwing arm as you pull it back. To create a strong bond with the throwing arm, use a pencil or other tool to press the elastic band firmly into the hot glue, and hold it  for a few seconds until the glue cools. Do not use your fingers or you will burn yourself! Your catapult is nearly ready to go, but a few more steps will make it sturdier and easier to use!  Attach the milk jug lid to the free end of the throwing arm with a dab of hot glue. Attach one additional craft stick horizontally to connect the slanted sides of the two uprights and provide additional stability. Add additional craft sticks to the bottom of the catapult that out as needed to keep the machine stable while firing. Load a ping pong ball or grape into the milk jug lid.  Pull back the throwing arm and let fly!

What is a summary?
Gather your supplies. Build two uprights for the catapult. Build a base to hold the uprights. Add the fulcrum to the catapult. Build the throwing arm. Add the finishing touches. Fire your catapult!