This is a catapult (ala torsion style) I built inspired from the video a contributor named schoondogs posted. His catapult looked simple enough so I thought I'd make a step-by-step with some improvements (that's the American way right? - and the Japanese way for that matter). I am not a master craftsman, just trying to be a Hero Dad* for my boys so look past the low grade finishing and more so on the end result. The design is not pretty but it is very functional and that's really all a 5 year old cares about anyway. It took about three hours to build (not counting the trips to Home Depot) and does not include any difficult cuts (all straight cuts) or elaborate tools.
2 - 8' 2x4s
25 or so 3" brass wood screws
24" 1/2 PVC pipe (SCH40)
6 feet of paracord cord
2 small wood dowels (I used a old drum stick)
some type of cup to hold ammo (with hardware for attaching to arm)
Approx 10 big nails (2 1/2 inch honkers)
9" Japanese pull saw (this is great for silent late night projects)
7/64 drill bit
1" drill bit
tape measure (or yard stick)
Range: after all modifications this baby can chuck a tennis ball easily 60 feet
*Hero Dad - any dad trying to impress his kids with some type of act or service - in this case (in the steps of my dad) it's building something really cool
Step 1: Building the base
Cut the 2x4s into 14" and 30" lengths. Drill the 3" screws into each end to create a base for the catapult
Step 2: Add the side supports
Approx 17" from the back of the catapult nail in the upright supports. These supports are 13" tall
Step 3: Install the block supports
Most catapults use a triangular support for their uprights but since I just wanted to make a functional (not pretty) catapult I just opted for easy horizontal blocks.
I did not show this step but you will also need to add the horizontal (stopper) support - this is 14" wide.