How to Build a Catapult

Step 7 Make the Winding Spool, Rope, and Firing Pin

A few feet in from the back of the catapult, on the upward sloping braces, drill a hole through each brace, so that a metal pipe can fit though the holes. Cut and place a metal pipe into the holes, and leave a bit sticking out on each end - this will be the spool. Weld another pipe onto the spool, as to create a means to wind the spool with some sort of crude metal handle.

Tie one end of the nylon rope around the spool and the other end around the S-hook. You'll use this later to pull down the arm, then unhook it to prepare to fire.

To make the firing pin, you're going to need a sturdy hinge, some more steel pipe, and any carriage bolt or smooth piece of metal. If you use the carriage bolt, you'll have to grind it down so that it's smooth. Weld the steel pipe to one side of the hinge, and then weld the carriage bolt perpendicular to the end of the pipe that's not attached to the hinge and that the hinge moves in a direction opposite the side that the bolt/smooth piece of metal is welded on. These welds should be X-TREMELY strong - this is critikal. The bolt or smooth piece of metal should be slightly slanted downwards (see picture), and the pipe should be no more than 2.5' long. ^{Sorry about the run-ons}

Screw the not-welded part of the hinge into the back of the catapult so that the pipe is in the center of the back of the catapult.