The Roman Empire's onager catapult used torsion twisting an object, in this case a restraining rope or spring, by applying torque—to build tension in the arm and generate a powerful swing. The onager catapult was a central siege engine for the Romans from the 4th century A.D. until the 6th century, capable of launching projectiles over 400 feet to breach castle doors and walls. Our design can't quite do that, but it's perfect for kids to build and use in games and experiments. Building this catapult takes precise measurements, skill with a drill, and an understanding of how the pieces work together to launch a projectile (so read the instructions first). It's a fun, hands-on lesson in mechanical energy and torsion science!
BUILD A CATAPULT
MAKE THE CATAPULT FRAME
Drill four/16-inch pilot holes through the 10-inch frame pieces, with the holes 134 inches from each of the four ends and centered vertically. Drill a pilot hole into the center of each end of the crossmembers [1].
Apply glue to the ends of one crossmember and near the pilot holes on the inside of the 10-inch frame pieces; screw the crossmember into place [2]. Repeat this step on the other end.
Drill 3/16-and 1/4-inch holes through the sides of the frame, 5 inches and 5 1/2 inches on center, respectively, from the front of the frame. Glue the footings to the bottom of the frame, flush with the sides and 1 inch on center from the ends [3].
Drill pilot holes into the center of the ends of the footings; screw the wheels into place [4].
INSTALL THE UPRIGHTS AND UPRIGHT SUPPORTS
This story is from the May - June 2022 edition of Popular Mechanics.
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This story is from the May - June 2022 edition of Popular Mechanics.
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