Well, honestly maybe I should make a video just like this. I'm not a historian, but I have a beautiful replica of medieval trebuchet that I've build, I have 12 years of experience in operating trebuchets and I have already taught many people how to operate it. You can check out my channel (there are also some videos of my modern approach to trebuchets) and stay tuned. Or just leave a comment under one of the videos that you want a tutorial about loading a trebuchet, I should be able to do it in about two weeks
at the zoo I work @ in LA I sneak Koala bear out of zoo and take them home with me to eat ice cream while I watch nature shows. I then sneak Koala back in zoo next day and no one ever know HAHA I also feed them twizzlers threw the cage and mix sweet tarts into there food dishes. It's a great job!
You definitely could have attached the bike/car/whatever to the projecile that comes with the catapult and connected the projectile to the catapult like normal