Make a trebuchet (mostly) out of lego, capable of launching small objects like acorns or minature marshmallows over thirty feet. It’s a geeky ABS cousin to the PVC Marshmallow shooter, and you can build one yourself.





The trebuchet consists of several parts: A sturdy base with wheels, a movable arm with a counterweight, and a flexible sling with cords on either end. Obviously, it’s got more wheels that it needs– and yet, they somehow seemed appropriate.

The base of the trebuchet needs to be extremely strong to support the axle and withstand the high forces that are generated in the launch. The design is based around a pair of heavily reinforced A-frames, and it performs quite well. You can zoom into the pictures to get a better look. The weakest aspect is that there is (presently) no good bracing against out-of-plane motion of the counterweight. While it is certainly possible to add struts to make it stronger, they tend to get in the way of actually operating the trebuchet.

By sliding the axle, the arm and counterweight of the trebuchet can be removed to work on either the arm or the base.

A couple of non-Lego items used here: A three-pound (!) lead fishing weight, and a loop of copper wire to attach it to the arm.