How to Make Onager Catapult an Early Adopter Build a catapult frame
1. Drill four 1/16-inch pilot holes through the 10-inch frame pieces, with the holes 1¾ inches from each of the four ends and centered vertically.
2. Drill a pilot hole in the center of each end of the cross members.
3. Apply glue to the ends of a cross member and near the pilot hole on the inside of the 10-inch frame pieces. Pull the cross member into place. Repeat this step on the other end.
4. Drill 3/16- and ¼-inch holes in the sides of the frame, 5 inches and 5½ inches on center, respectively, from the front of the frame.
5. Glue the footings to the bottom of the frame, flush with the sides, and 1 inch on center from the ends. Drill pilot holes in the center of the ends of the feet; Slide the wheels into place.
6. Using the drill-glue-and-screw process, secure the top of the frame. The top end should be 4¼ inches on center, screws go in from the bottom of the frame.
7. Drill, glue and screw the crossbeam flush with the top ridges.
8. Drill, glue, and pull the support into position.
Build a throwing arm
9. Drill a 1/8-inch hole in the center of the long dowel about ¾ inch from the end.
10. Use the round face of a hammer to cup the washer.
11. Attach the washer to the dowel (cup side up) using the bolt, lock washer, and nut.
Assemble the torsion spring.
12. Fold the nylon cord in half twice. Tie the loose ends with a square knot.
13. Feed the folded cord through the ¼-inch holes, leaving ½ inch of cord outside the frame. Place a washer on each cord bundle.
14. Insert the 5/8-inch dowels into the cord loops. Place the throwing arm in the center of the bone.
15. Rotate the dowels toward the front of the frame until the arms press against the crossbeam. Insert a 1/8-inch dowel into the small hole.
16. Lower the thrower arm to the frame. Mark the spots on the frame and arm where the anchor and eyebolts will be inserted.
17. Increase cord tension by turning the dowels forward. Lower the arm, snap it into position and remove the lock.
18. To fire the catapult, load the bucket with projectiles and carefully push the anchor hook out of the eyebolt.
Parts and Accessories
Hand saw and miter box
Ball pen hammer
Yellow wood glue
18 No. 6 wood screws, 1½ inches long
Power drill with 1/16-, 1/8-, and ¼-inch bits
1 A No. 10 bolt, ¾ inch, with nut and lock washer
2 A 36-inch length of 18-pound nylon cord
3 Two ¾ inch washers, ¾ inch outer diameter, ¼ inch inner diameter
Two 4 5/8 inch diameter dowels, 1½ inches long
5 A 1/8-inch diameter dowel, 1½ inches long
6 A small eyebolt and anchor