I hate to break it to you all but Chris Angel isn't a magician, he's an actor. The "spectators" are all paid actors. Any time you see him doing one of his tricks, he really isn't doing a trick at all just playing a role. Just like in other movies, where the special effects guys make the shot look real, the same is so for this knob.
If you notice he NEVER does public appearances and makes things happen on stage or ??? Ever wonder why that is?
BTW: they probably did it with piano wire and a crane. They did something similar in the '30s with (some magician at the time). He did this stunt many times until one of the wires broke and he was flopping all over the place.