It looks like he has the booster attached to his lift so that when he lifts up a string(or something like that) pulls it out but gravity pulls it back down when the lift goes down and loosens the string. At least that’s what it looks like he’s doing. His lift is fast enough to make that work.
Amazing design! How would one go about building something like this (a completely passive catapult for a claw)? To be honest, I still don’t realize understand how the catapult works.
Id start by actually building a claw but just spacing them a decent distance apart so you have space. For my first skills competition I only had the claw and it worked fine without the catapult just no far zone. In terms of the catapult, you need to design a loading mechanism and then a system to release the energy.