A visitor to my site has built a few of the different catapults and trebuchets that I have here. He has also made quite a nice little design improvement to the Trebuchet project. The improvement is a nice little locking mechanism where you can draw the Trebuchet into the ready position and lock it. Then when you pull the pin it fires! Very nice design improvement and a very big thankyou to my web visitor Koji!! Thanks Koji. The last picture shows the Golden hooks that are the design improvement.

You can see that it is very close to the trebuchet design I have laid out. But Koji made some nice little improvements and improvised as he needed to. I used the axle from a toy car and he used a stiff coat hanger. Works great.

His counterweight is a plastic cannister that he filled with batteries.

If you want to build a Trebuchet like this one I have a complete tutorial with pics that shows you how here: How to Build a Trebuchet

This picture shows the ingenious way that he used some eye hooks to make a locking mechanism.