They aren't as great as often claimed. Since they rely upon potentially slight differences in diameter, any layering of cable on either side radically alters things. You have to be religious about policing the rope as it rolls onto the cylinder. This also limits the amount of cable that can be used to whatever can wind on without layering. So ya, it can raise an extremely heavy bit of bridge a few feet, but it isn't suitable for anything resembling a crane or hoist. It is great for lifting an engine block off its mounts, but not for lifting lumber up the side of a building.