Figured out I could use a higher and more sturdy hinge, welded it on top and used the bar I found on Wednesday to make the thin rod go through. Since there were small angles when I welded both times, they added up and I ended up with a slightly off mechanism. But this did not affect throwing since you could fix it as you were aiming.
I decided that the piece that stopped the bar -that was also fixed to the ground- didn’t have to be a fixed single piece. I screwed the bottom piece onto the wood platform and fixed it 2 clamps. And with a small cap (that was spray painted later on) from the kitchen the catapult was ready for testing.
I was glad to see that my colleagues were more than happy to try it and play around with it before people even started to show up. We played around with pretzels and a game to see who would be the first to get a rock inside a plastic cup later in the evening.
And the final bonus cat photo: