May peace be upon you

This mini catapult I built in the middle of 2009 as I remembered. I built it just because I like how it works. I want to know how the spring concept is used to throw the stone far away at old time ago.

I did not capture the photo of each step at that time, but I am sure it is easy for you to understand as it is very simple.

Things you need are:

1) some unused long square wood. I used 1cm x 1cm but any wood can be used.

2) excess nylon rope.

3) nail or screw

4) flat wood

Step 1: Cut Wood

Based on my picture, you can cut your wood with handsaw.

The length (size) depend on what you deserve. The bigger size can throw an object at far distance.

Step 2: Join the Wood

These are the basic way to join the woods. My way..hahahaa

Horizontal joint

I first drill a small hole just enough to fit the thread part of the screw/nail. Then I drill a bigger hole about the size of the cap of the screw/nail. This method is used to produced a tough join between woods.

Or you can just direct screw/nail from first wood to the second wood.

Vertical joint

For the vertical joint, I make a mortise to make it stay fix and strong in its position. Then nailed it from bottom.

Step 3: Spring Mechanism

You can use metal spring, rubber band or other elastic material to produce the stretching force.

In my project, I used the excess nylon rope.

Take some nylon rope (length based on your desired) and fold it to half length. Place the arm in between the two folded rope (at the middle).

Rotate the arm so the rope is stretch until tight. You can lock the end of the rope with hard and long material such as nail. The nail can be turn to produce more stretching force to the rope.