Today we’ll be setting aside the circuits and solder for a little while in favor of good old fashioned wood and bungee chords to make this backyard catapult. Items needed include nine sections of 2×3 wooden beams of varying lengths, some screws and eye hooks, a bungee chord, a broom handle, and a few other things which are all detailed in the read link below.
Here’s a quick summary version of the four pages of instructions: First the 2x3s must be cut to their proper lengths. The two 24-inch beams must then be drilled to create pivot holes. Notches should then be cut into them with a saw. The same should be done to two 14-inch beams, which will allow them to be fitted to the 24-inch beams at a right angle. With the two 7 1/2-inch beams, the six beams make up the base of the catapult and two support arms extending upward. Two more beams, a crossbar and angled beam, are added to complete the support system, leaving it prepped to add the swing arm.
The swing arm is a 28-inch beam with the broom handle running through a hole in the bottom and a cardboard cup at the top. The broom handle will also run through the pivot holes in the base. The bungee chord should be stretched from an eye hook on the swing arm and one on the base. The strength of the catapult can be adjusted by using a stronger bungee or adjusting the height of the crossbar. For slightly more complex mechanics, bearings can be added to the pivot points to ensure smooth and efficient energy transfer.
[via DIY Life]