The first 100 people to go to https://blinkist.com/stevemould will get unlimited access for 1 week to try it out. You'll also get 25% off if you want full membership.
Crowned Pulleys do this bizarre counterintuitive thing. Instead of slipping off the curved surface, the band actually moves to the middle and stays there.
Not to be confused with snatch block type pulleys! Destin's video here: https://youtu.be/M2w3NZzPwOM
Here's the video I made with Tom Lipton: https://youtu.be/HcVA-4mcXQQ