Any advice on building something like pic related? (Maybe a bit smaller)
first you need blood and marital ties to continental europe, second you need general ruthlessness, and third you need an intense hatred of the scots. with all of these things combined, you can achieve your loup de guerre
What are you going to do with something like that? At most you can probably mess a building up pretty bad, maybe even kill someone if the projectile is large enough. Guns are made to kill or maim, but siege engines aren't made to purposely do that.
What details do you want to know more about? The sling mechanism or the construction of something big?
This guy has some good building tips that helped me https://www.youtube.com/watch?v=8hAX72Xgf1U
I built a standard catapult a few years ago. It has two legs, basically tripods, and the pivoting arm. All made out of lumber. Was an easy build.
I made the tripods too small though. The rocking movement of the counterweight (a box which I filled with heavyish shit, wasn't that good of an idea) is quite violent so it needs to be sturdy. I have been planning on making the counterweight fixed instead of pivoting which would mean that it wouldn't shake that much. It's just too cold now, it's a project for sunny days with nothing to do.
The standard catapult (trebuchet) is inefficient though. As the counterweight moves in an arc it doesn't give that much oomph when it's tangent moves away from being perpendicular to the earth. There is an more efficient version where the counterweight falls down and the pivoting point moves. Can't find it on the tubes though...
I have a book called backyard ballistics wich is interesting, it has a few different guides to build warmachines, as well as lots of background info. Recommended.