This is one of my favourite DT projects! Lots of design and engineering opportunities and great fun.
The children are given the task of researching and then designing and making their own catapult or trebuchet. Could link well to topics on e.g. War or History or simply be a stand alone fun DT project.
If you don't feel too confident about the DT there are plenty of online images and guides that the children can follow.
I've only done this once so far but my class loved it and I'm looking forward to doing it again next year.
The project culminated in pupils having a competition to see which catapult could launch a ping pong ball the furthest.
Hope you enjoy.