Things You'll Need
Instructions
Take a Lego block that is 1-by-10 sections long and another that is 1-by-12 sections long. Place the 1-by-10 horizontally on top of the the 1-by-12 piece so that one side is evenly lined up and the other is not. Repeat this for two more blocks of the same size.
Attach these pieces on either side of the width of a flat Lego piece that is 8-by-12 sections long. Take two Lego pieces that are 1-by-10 and secure one on top of the other. Secure it to the front edge of the catapult between the two pieces attached to the sides.
Take one blue sign connector and insert a long Lego beam piece into one of the bottom holes from the center of the 1-by-10 front Lego piece. Secure a small bowl-like object you wish to use for the catapult to the end of the beam with duct tape.
Insert a "plus sign" Lego piece on the other side of the hole to stop the arm of the catapult at a certain point. Insert a circle connector with three holes through the plus sign connector and insert each end into the third hole from end of the front facing 1-by-10 Lego piece.
Place two stacked 1-by-10 Lego pieces at the back edge of the catapult and push a beam through the sixth hole from one end, making sure that it is long enough to be secured on either side. This will stop the catapult arm from launching too far forward.
Secure a plate piece that is 2-by-3 sections long in the center of each 1-by-10 piece. Place a plate that is 1-by-2 sections long on the top center circles of both 1-by-10 pieces once again. Stretch a rubber band between those two places where the catapult sits and hook it on to each end.
Place an object in the small bowl at one end of the catapult, pull back on the rubber band and release to launch the object into the air.