Minecraft wiki entry for Rube_Goldberg_machine, associated text: You can make minecart rails with powered rails start them and detector rails to power other things in the RGM. You could use them with activator rails to transport mobs around the RGM. For example, you could make a zombie maze and put a minecart at the end. When the zombie gets in, it is moved quickly along the rails. It might then hit an activator rail and chase after another villager. The villager could have another minecart in front of it, continuing the cycle. You could also make minecarts knock other minecarts into powered rails, shooting them down the track.