Trebuchet:Main Parts of a

1. A counter-weight that drops straight down transferring gravitation potential energy into kinetic energy. The larger the weight, the farther the projectile can travel.

2. A base of some sort, typically constructed of triangles for strength.

3. A lever arm: the longer the arm, the more velocity and force generated for launching.

4. A sling for the payload.

5. Sometimes wheels to absorb wasted kinetic energy back into the trebuchet.

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Build itHow can I

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Follow these simple steps.

Grab:•12 or so pencils• Bunch of elastic bands• 1 paper clip• Some masking tape• Some fishing line/string• Lab Weight

A strong base is pretty important. Take some time to make sure everything is parallel and looks good.

Use elastics to bind the pencils together. You’ll find you get good at making joints pretty quickly.

Criteria

Make the two uprights. I like to leave the metal ends up to reduce friction later on.

Make the lever arm from three pencils in a “T” shape. You could use more to make the arm longer. Offset the pencils a little so one sticks out some.

Bend a paper clip to make the release. This will be what the sling hooks into and releases from. You might need to vary the angle of bend and length left sticking out later on.

Fasten this to the end of your “T”.

Your trebuchet should now look something like this. Test to see how well the lever arm can rotate on the uprights.

Using a short length of string, tie a weight onto the bottom of the arm. It takes some trial and error to get the exact length correct. You can now test to see how sturdy your base was. It should have smooth action by now.

Make a little sling from some masking tape. You can even tape the string right into the sling. Some students make the sling more like a little box and find that holds the ammo well.

This is the tricky part: tie one end of the sling to the end of the arm and make a loop in the other end to fit around the paper clip. You’ll need to tie it so the sling opens when it’s at the top of it’s path.

The finished product looks something like this. Again, the release usually gives students the most trouble, and is really a trial and error thing to get just right.