Play Catapult

A catapult is a pretty simple mechanism, no more complex in principle than a teeter totter. One end is shorter than the other; a heavy weight goes on the short end; the long end does the launching. If catapult is built incorrectly it can tip over or release the projectile too early or too late. Build the catapult, then tinker with a few things once it's done to get it firing perfectly.

Instructions

1 Cut the following lengths of lumber 2-by-4-inch lumber: three pieces at 2 yards long, three pieces at 1 yard long and four pieces at 4 feet long. Make a rectangle 2 yards long by 1 yard wide. Bolt the wood together with carriage bolts to create your base. Lay another 3-yard plank down the center of the rectangle lengthwise.
2 Make isosceles triangles which stand up vertically from the each of the long sides of the base. They use the 2-yard lengths from the base as their bases and 4-foot lengths to form the other two sides. They need to be 1 yard high. Cut the ends of the 4-foot lengths so that they fit flush together and against the base. Bolt them together and place an additional 1-yard length vertically from the tip of the triangle to the base.
3 Cut right angle triangles of hardboard about 8 inches on the longest side, place them over the angles where the wood is joined and nail them in place to give support to the structure.
4 Drill a hole large enough for the metal tube through the last 1-yard length of lumber. Drill it 10 inches from one end. Drill a further hole 2 inches from the end and another 2 inches from the other end. Drill a hole through the lumber at the apex of each triangle and slide the metal tube through one, through the middle hole of the plank with three holes and out through the hole in the other triangle.
5 Move the piece of lumber with the three holes in to a central position on the bar. This is your firing arm. Drill holes through the pipe a few inches on either side of where it comes out from each bit of wood. Put carriage bolts through these to keep the bar sliding to far from the central position.
6 Put rope through the hole in the short end of the firing arm. Tie it through about 15 pounds of body building weights to it near the end of the firing arm.
7 Cut a square of fabric 10 inches on each side. Tie rope to two diagonally opposite corners. Loop one end of the rope through the hole in the long end of the firing arm. Tie the other to the metal ring. Bang a large nail halfway into the firing arm next to the hole where the rope is tied. Bend it over and point the head toward the nearest upper corner of the plank. Cut the head off the nail.
8 Place something like a tennis ball in the square of cloth. Slip the metal ring over the cut off nail. The tennis ball will be cradled in the cloth. Pull down the firing arm. Lay the tennis ball and ropes along the central plank. Make sure the aiming area is free of anything or anyone that could be hurt or damaged. Release the firing arm.

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