Tips for Winding the Spring for your Torsion Catapult
Here’s a quick summary of what I have to start with…
A note about rope – today I have ½” sisal rope (100#) strength. I have used ¾” sisal rope (361# strength) in the past to throw further (wrapped fewer times across the arm). Some people use small diameter rope wrapped many times around. Synthetic ropes tend to be too “stretchy” and I’ve found that fiber ropes work better. Note that the ends of the rope are wrapped tightly in electrical tape. This is important.
Step 1: Tie a loose, square knot with one end of the rope around a torsion peg.
Step 2: Push the other end of the rope through the 1” washer and one side of the frame, in the pre-drilled 1” holes.
Step 3: Pass the rope under the arm and through the 1” pre-drilled hole and 1” washer on the other side of the catapult frame.
Step 4: Pass the rope around the next torsion handle, and back through the holes. Over the top of the arm (at the notch cut).
Step 5: Repeat the process, wrapping the rope around the pegs and back through, until you’ve gone at least twice over and twice under the arm. This will be difficult! I usually have to use the screwdriver to push the rope end back through the holes on the final pass.
Step 6: Tighten the pegs. Do it as evenly as you can. Tighten toward the upright part of the frame. Here is the catapult with just enough tightness to raise the arm.
Step 7: Tighten more. Use a lever (the 1” lead pipe) to do several turns beyond hand strength.
I wrap the rest of the rope around the frame at this point.
There is an art to tightening the catapult. You’ll get more fling the tighter you make it, but the rope will break at some point. Here’s my catapult tightened to a point where it flings a block of wood ~10’.
Here are a couple of videos of someone (not affiliated with us) making a torsion catapult spring with a small diameter synthetic rope, wrapped many times around the torsion peg. (I find fibrous rope-like sisal works better.)
If you are still having troubles are have lost the instructions included with the kit, please contact us here and we’ll get back to you.