I saw a video about a folding speargun by a Spanish speaking inventor a while ago. While it was impractical to use his mechanics, I took his break-barrel idea and changed it for a ball shooter.
The result is a powerful, short, easy to cock and accurate new weapon.
Unfolded and cocked:
The bands are attached to both a leather pouch and a length of paracord. The paracord is held back by the sear/trigger part.
The entire trigger/lock module is able to swing up and down, in order to follow the bands while the weapon is cocked/unfolded. This prevents chafing on the paracord and makes the drawing much more smooth.
The lock for the folding pivot is very simple. It is held under tension with rubber (what else), but the rubber is not needed for holding back the force. Sear and pivot are in line, rock solid.
The weapon only weighs about 600 gramms (1,3 lb), and is about 65 cm long (folded). I may add a red dot and a folding shoulder rest later on.
Here is the video: