I got an email from Aaron about the trebuchet he made. Here is what he has to say. And he gives us some great tips.

Just wanted to say thanks for all the great info on your site. And I wanted to send you some photos of my Trebuchet that I built using your basic design.
Overall, I wanted a desktop sized Treb, (so in case you decide to post the pics and the specs) what I did was simply half all of your measurements for the actual structure. For the correct counterweight/projectile ratio I used 2 C and 2 AA batteries taped and hot glued together and came up with (if I remember correctly) around 215g for a final weight.

After doing the 133:1 ratio calculation, the best way I found to make the projectile match the perfect weight of the calculated 1.6g was using a small square of aluminum foil on a gram scale and adding hot glue. As soon as I got to 1.6g I quickly wrapped it up and rolled it in my hand to make the perfectly rounded ball (and I know you know this but if you do post this method of making a projectile, just warn kids that the glue can be hot). For a locking mechanism, I just made holes on either side of the cardboard runway and lined it with washers for better durability and used a piece of wire to run through and hold the arm. All in all this things been a blast and w/o changing any of the variables around I get about 7 1/2 feet out of a launch...which is perfect for this little Desktitan of Demolition!
Thanks again Will, Take care.
Aaron

Make a Tennis Ball Trebuchet - (Fast and easy)

A fast and easy trebuchet project with lots of power. How to make a tennis ball trebuchet I keep it simple and use common stuff so you don't have to spend any money.

The Little Dragon Trebuchet Project - Complete tutorial with lots of pictures on how to make this table top trebuchet. This is a nice little afternoon project you can make out of small pieces of wood and a little bit of time. It's a really great example of how a trebuchet works.