I agree with the other comments that the machine gun is not very powerful (I may try to replace it with a shield or something). Otherwise the robot is the most awesome ever made 10/10 +++
There is a strange effect, because for me the top magnet floats up. Sometimes it sticks to the other magnet and both float up and start spinning. The first magnet one you made works fine tho.
Nice work. However, I would have tried to demonstrate something with it. For example the left pulley needs a minimum 1200 Nm strength to lift the block, while the right one needs 1600 Nm.
This is a catapult not a trebuchet. If you want a reloadable trebuchet, I made one several days before this one:
http://www.algodoo.com/algobox/details.php?id=43663