There are many designs in existence for small model trebuchets, and there are also many examples of model bridges build from popsickle sticks. Valkyrie Aerospace’s benchtop trebuchet design is unique, however, in that it combines both techniques, resulting in a design that can be built quickly with minimal woodworking skills. As all cuts can be made with a strong pair of scissors, the trebuchet, which demonstrates several important mechanical engineering concepts, is also well-suited as classroom physics project. We have tested the prototype below with a variety of counterweight and payload combinations, and we have found that marbles are ideal projectiles (on a side note, please be careful and avoid launching anything towards people, animals, or fragile objects).
You can begin by printing out a copy of the plans (available as a download at the end of this article), or by opening them in a PDF viewer as you build; precise alignment of components can be achieved necessary. A complete list of tools and materials to be used in the build process is documented in the build plans and includes:
-Popsicle sticks (4 1/2 in x 3/8 in); we used about 60 in our prototype.
-Hot glue gun and spare sticks
-Heavy object for counterweight (such as an old hammerhead)
-Cloth or foamboard for sling or bucket
-Strong scissors or utility knife
Building the trebuchet is not a complicated process, but because it is a three-dimensional item, the arrangement of parts can sometimes be confusing. We have done our best to mitigate this confusion by providing several camera angles of key joints and components.
When making the frame and arm assemblies, try to avoid applying excessive extra glue, as it is unnecessary for the areas that are being bonded and makes a mess. Allow the glue to dry thoroughly before adding the cross-bracing for the frame and threading mason twine through the end holes on the arm.
You can make a bucket to contain the marble as it is accelerated through the swing of the arm; we made ours out of foamboard. A deep bottle cap (e.g. from a soft drink bottle) with holes drilled in either side for the string to be tied through would also work well.
Benchtop trebuchet plans