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Some Tips on Making A Successful Trebuchet

Will Kalif I recently got an email from a Cub Scout Den Leader ( "Chris C-S, Den Leader, MN" ) who made, with his scouts, 6 of these trebuchets. They were a big success and he has passed on some tips on how to improve things. And he also made a larger version. Here is what he has to say:

"Just wanted to drop you a note to thank you for your detailed tabletop trebuchet plans and instructions. I used them this past weekend with my Cub Scout den of 3rd graders, and they had a blast flinging grapes out on the school yard. "

I thought I'd pass on some of the lessons I learned from this:

To make this a project that the boys could finish mostly on their own and within an hour (roughly), I made the side assemblies in advance. (We made 6 trebs in all, so it was kind of assembly-line work.) I also pre-drilled all the holes (throwing arm, pilot holes in the cross braces and for the eye hooks). The boys were able to do everything but the weights and slings all by themselves; we had parents to help out with the rest.
I found that a 5 1/2" lag bolt made a great axle. I found some at Home Depot that are 1/4" thick, and are only threaded on the last inch. The length was just right for your dimensions. And I didn't have to rip apart any toys.
I had to fiddle with the weights. Your instructions show that 6 AA batteries would be sufficient, but I wasn't able to get a good throw (again, with a grape) until I taped 4 D batteries together. I'm sure there's some math involved that I didn't look at. Rigging the batteries to pass through the frame cleanly took some fiddling, too.

Just for fun, I multiplied your dimensions by three and made another trebuchet out of 2x4s I had in the garage. Alas, it didn't work as well as I'd hoped - I think there's some relationship between the weights, the mass and length of the throwing arm, the length of the sling, and the weight of the projectile that I needed to give more attention to. The boys thought it was cool anyway. Maybe over the summer I'll figure it out.

"Chris C-S, Den Leader, MN"

I want to give my thanks to Chris for the terrific tips on this project and I want to say I am glad that the scouts had so much fun with it!

I also want to say that the idea of using lag bolts for the axle is perfect! This is a great solution and its easy to find the lag bolts at any hardware store.

If you came to this webpage directly from a search engine here is the beginning of the table top trebuchet project: Make a Small Trebuchet

This is a Storm The Castle Project